How motor proteins induce mechanical movement at the molecular level has been a focus of biophysicists for a long time. While the whole picture is yet to be completely revealed, recent developments in looking at nanometer‐scale movement with millisecond‐time resolution driven by single motors have revealed important new details about the moving step size and amount of force generated per molecule.

This paper deals with an analysis of debris produced during the polishing of diamond. The debris is carefully collected 'as ejected' to shorten the history of the freshly removed material. Using high-resolution electron microscopy as well as electron-energy-loss spectroscopy, the structure of the material is revealed and analysed in terms of density, percentage of sp 2 hybridized carbon, and oxygen content. Debris from polishing in the so-called hard and soft directions were involved in this investigation. Overall the structure of all (...) debris is amorphous carbon. The material appears to be composed of small clusters, some nanometres in diameter, in which the graphite basal planes can be recognized. Very few and very small nanometre-sized diamond particles were found in the debris from polishing in the hard direction. The results support a polishing mechanism based on a mechanically induced transformation of diamond to graphite, after which material removal easily occurs. The well-known anisotropy observed in polishing can be explained satisfactorily on the basis of this model. Finally, in appendices, the art of polishing and the role of the black powder during preparation of the scaife are discussed. (shrink)

From cytological examination, the size and form of the chromosomes in the eukaryotic nucleus are invariant across generations, leading to the expectation that constancy of inheritance likely depends on constancy of the chromosomal DNA molecule conveying the constant phenotype. Indeed, except for rare mutations, major phenotypic traits appear largely without change from generation to generation. Thus, when it was discovered that the inheritance of traits for bacteria, mitochondria and chloroplasts was also constant, it was assumed that chromosomes in those locations (...) were also constant. Such has not turned out to be the case, however; those chromosomes are highly variable in structure. I propose, therefore, that only for the nucleus is there a requirement that a chromosome be “finished” (contain only fully replicated genomes) before it may segregate to daughter cells. This requirement does not apply to the variable chromosomes among chloroplasts, mitochondria and bacteria. BioEssays 29:474–483, 2007. © 2007 Wiley Periodicals, Inc. (shrink)

Species evolve, very slowly, through selection of genes which give rise to phenotypes well adapted to their environments. The cultures, including the languages, of human communities evolve, much faster, maintaining at least a minimum level of adaptedness to the external, non- cultural environment. In the phylogenetic evolution of species, the transmission of information across generations is via copying of molecules, and innovation is by mutation and sexual recombination. In cultural evolution, the transmission of information across generations is by learning, (...) and innovation is by sporadic invention or borrowing from other cultures. This much is the foundational bedrock of evolutionary theory. But things get more complicated; there can be gene-culture co-evolution. Prior to the rise of culture, the physical environment is the only force shaping biological evolution from outside the organism, and cultures themselves are clearly constrained by the evolved biological characteristics of their members. But cultures become part of the external environment, and influence the course of biological evolution. For example, altruistic cultures with developed medical knowledge reduce the cost to the individual of carrying genes disposing to certain pathologies (such as diabetes); and such genes become more widespread in the populations maintaining such cultures. Assortative mating can affect biological evolution, and particular cultures may influence the factors which are sorted for in mating. (For a careful discussion of the effects of cultural evolution on natural selection, see Cavalli-Sforza and Bodmer, 1971:774- 804). This paper examines mechanisms involved in the co-evolution of a biological trait, the critical period for language acquisition, and a property of human cultures, the size of their languages. A gene/culture interaction will be shown that can be described as a kind of symbiosis, but perhaps more aptly as an `arms race'. In this introduction, we will sketch the basic mechanics of the interaction in very broad terms; the rest of the paper will explain and justify the details. The implications of our model for second language acquisition are given toward the end of the paper. (shrink)

In 1926, Haldane published an essay titled 'On Being the Right Size' in which he argued that the structure, function, and behavior of an organism are strongly conditioned by the physical forces that exert the greatest impact at the scale at which it exists. This chapter puts Haldane’s insight to work in the context of contemporary cell and molecular biology. Owing to their minuscule size, cells and molecules are subject to very different forces than macroscopic organisms. In a sense, (...) macroscopic and microscopic entities inhabit different “worlds”: the former is ruled by gravity and inertia, whereas the latter is governed by Brownian motion. One implication is that we should be extremely skeptical of models and analogies that seek to explain properties of microscopic entities by appealing to properties of macroscopic ones. Unfortunately, this is precisely what the appeal to engineering metaphors in molecular biology attempts to do. Molecular biologists routinely resort to such metaphors because they are familiar and intuitively intelligible. But if our machines were the size of molecules it would be impossible for them to function the way they do. It follows that we should avoid distorting biological reality by construing it in engineering terms. In this chapter I examine four key metaphors in molecular biology – “genetic program,” “cellular circuitry,” “molecular machine,” and “molecular motor” – and I argue that their deficiencies derive from their neglect of scale. I also try to explain why many biologists today appear to have forgotten the importance of scale that Haldane drew attention to in his essay. I suggest that the reason has to do with the influence of Schrödinger’s argument in 'What is Life?' regarding the stability of the gene. (shrink)

It is argued that John Bickle’s Ruthless Reductionism is flawed as an account of the practice of neuroscience. Examples from genetics and linguistics suggest, first, that not every mind-brain link or gene-phenotype link qualifies as a reduction or as a complete explanation, and, second, that the higher (psychological) level of analysis is not likely to disappear as neuroscience progresses. The most plausible picture of the evolving sciences of the mind-brain seems a patchwork of multiple connections and partial explanations, linking anatomy, (...) mechanisms and functions across different domains, levels, and grain sizes. Bickle’s claim that only the molecular level provides genuine explanations, and higher level concepts are just heuristics that will soon be redundant, is thus rejected. In addition, it is argued that Bickle’s recasting of philosophy of science as metascience explicating empirical practices, ignores an essential role for philosophy in reflecting upon criteria for reduction and explanation. Many interesting and complex issues remain to be investigated for the philosophy of science, and in particular the nature of interlevel links found in empirical research requires sophisticated philosophical analysis. (shrink)

In eukaryotic cells the nucleus and its contents are separated from the cytoplasm by the nuclear envelope. Macromolecules, as well as smaller molecules and ions, can cross the nuclear envelope through the nuclear pore complex. Molecules greater than approx. 60 kDa and containing a nuclear localization signal are actively transported across the nuclear membranes, but there has been little evidence for regulatory mechanisms for smaller molecules and ions. Recently, diffusion across the nuclear envelope has been observed to (...) be regulated by nuclear cisternal Ca2+ concentrations. Following depletion of Ca2+ from the nuclear store by inositol 1,4,5‐trisphosphate or Ca2+ chelators, a fluorescent 10 kDa marker molecule was no longer able to enter the nucleus. Distinct conformational states of the nuclear pore complexes depended on the Ca2+ filling state of the nuclear envelope, supporting the assumption that a switch in the conformation of the nuclear pore complex may control the transport of intermediate‐sized molecules across the nuclear envelope. Thus nuclear Ca2+ stores may regulate the conformational state of the nuclear pore complex, and thereby passive diffusion of molecules between the cytosol and the nucleoplasm. The physiological significance of this finding is currently unknown. (shrink)

Hypotrichous ciliates extensively process genomic DNA during their life cycle. Processing occurs after cell mating, beginning with multiple rounds of DNA replication to form polytene chromosomes. Thousands of transposonlike elements are then excised from the chromosomes and destroyed, and thousands of short, internal eliminated sequences (IESs) are excised from coding and noncoding parts of genes and destroyed. IES removal from a gene is accompanied by splicing of the remaining chromosomal DNA segments to form a transcriptionally competent gene. For some genes (...) these DNA segments are in a scrambled order and are ligated into a genetically correct order at the time of IES removal. Next the polytene chromosomes are cut up band‐by‐band and all genes are excised from the chromosomes as short, linear molecules averaging 2.2 kbp (in Oxytricha nova). Gene excision is accompanied by destruction of all nongenic DNA, which, together with the transposonlike elements and IESs, accounts for ∼95% of the total sequence complexity of the genome in O. nova. Telomeric sequences are added to the excised gene‐sized DNA molecules. Finally, the gene‐sized molecules are replicated several times to form the macronucleus of the organism. (shrink)

The size and organization of the brain are determined by the activity of progenitor cells early in development. Key mechanisms regulating progenitor cell biology involve miRNAs. These small noncoding RNA molecules bind mRNAs with high specificity, controlling their abundance and expression. The role of miRNAs in brain development has been studied extensively, but their involvement at early stages remained unknown until recently. Here, recent findings showing the important role of miRNAs in the earliest phases of brain development are reviewed, (...) and it is discussed how loss of specific miRNAs leads to pathological conditions, particularly adult and pediatric brain tumors. Let‐7 miRNA downregulation and the initiation of embryonal tumors with multilayered rosettes (ETMR), a novel link recently discovered by the laboratory, are focused upon. Finally, it is discussed how miRNAs may be used for the diagnosis and therapeutic treatment of pediatric brain tumors, with the hope of improving the prognosis of these devastating diseases. (shrink)

The small, relatively constant size and conservative evolution of chloroplast DNA (cpDNA) make it an ideal molecule for tracing the evolutionary history of plant species. At lower taxonomic levels, cpDNA variation is easily and conveniently assayed by comparing restriction patterns and maps, while at higher taxonomic levels, DNA sequencing and inversion analysis are the methods of choice for comparing chloroplast genomes. The study of cpDNA variation has already yielded important new insights into the origin and evolution of many agriculturally important (...) crop plants, and promises to significantly enhance our phylogenetic understanding of the major lines of descent among land plants and algae. (shrink)

Scaling of pattern with size has been described and studied for over a century, yet its molecular basis is understood in only a few cases. In a recent, elegant study, Inomata and colleagues proposed a new model explaining how bone morphogenic protein (BMP) activity gradient scales with embryo size in the early Xenopus laevis embryo. We discuss their results in conjunction with an alternative model we proposed previously. The expansion‐repression mechanism (ExR) provides a conceptual framework unifying both mechanisms. Results of (...) Inomata and colleagues implicate the chordin‐stabilizing protein sizzled as the expander molecule enabling scaling, while we attributed this role to the BMP ligand Admp. The two expanders may work in concert, as suggested by the mathematical model of Inomata et al. We discuss approaches for differentiating the contribution of sizzled and Admp to pattern scaling. (shrink)

emerging field of nanotechnology. Nanotechnology gets its name from the nanometer, a distance of 10 -9 meters or roughly the diameter of a molecule, and the term refers to the technology for structuring matter with precise control at the nanometer scale, atom-by-atom or molecule-by-molecule, to form a pre-specified pattern. In other words, nanotechnology is the general ability to build large or small structures to complex atomic specifications.

There have been many claims that quantum mechanics plays a key role in the origin and/or operation of biological organisms, beyond merely providing the basis for the shapes and sizes of biological molecules and their chemical affinities. These range from Schr¨odinger’s suggestion that quantum fluctuations produce mutations, to Hameroff and Penrose’s conjecture that quantum coherence in microtubules is linked to consciousness. I review some of these claims in this paper, and discuss the serious problem of decoherence. I advance some (...) further conjectures about quantum information processing in bio-systems. Some possible experiments are suggested. © 2004 Elsevier Ireland Ltd. All rights reserved. (shrink)

The identification of molecules controlling embryonic patterning and their functional analysis has revolutionized the fields of Developmental and Cell Biology. The use of new sequence information and modern bioinformatics tools has enriched the list of proteins that could potentially play a role in regulating cell behavior and function during early development. The recent application of efficient methods for gene knockout in zebrafish has accelerated the functional analysis of many proteins, some of which have been overlooked due to their small (...) size. Two recent publications report on the identification of one such protein and its role in zebrafish embryogenesis. The protein, currently designated Apela, was shown to act as a secreted protein whose absence adversely affected various early developmental processes. Additional signaling proteins that have been identified in one of the studies are likely to open the way to unraveling hitherto unknown developmental pathways and have the potential to provide a more comprehensive understanding of known developmental processes. (shrink)

In 1965, John A. Pope presented a paper entitled 'Two-Dimensional Chart of Quantum Chemistry' to illustrate the inverse relationship between the sophistication of computational methods and the size of molecules under study. This chart, later called the 'hyperbola of quantum chemistry', succinctly summarized the growing tension between the proponents of two different approaches to computation–the ab initio method and semiempirical method–in the early years of electronic digital computers. Examining the development of quantum chemistry after World War II, I focus (...) on the role of computers in shaping disciplinary identity. The availability of high-speed computers in the early 1950s attracted much attention from quantum chemists, and their community took shape through a series of conferences and personal networking. However, this emerging community soon encountered the problem of communication between groups that differed in the degree of reliance they placed on computers. I show the complexity of interactions between computing technology and a scientific discipline, in terms of both forming and splitting the community of quantum chemistry. (shrink)

The general recognition of the existence of atoms and molecules occurred only at the beginning of the twentieth century. Many researchers contributed to this, but the ultimate proof of the molecular nature of matter that convinced even the last sceptics was the confirmation of Albert Einstein’s statistical-fluctuation theory of Brownian motion, a part of his comprehension of interdisciplinary atomism, by Jean Perrin’s experiments on colloidal gamboge particles. Einstein noticed a difference between the values of Avogadro’s constant derived from Perrin’s (...) experiments and Planck’s calculation from black-body radiation. Einstein assumed the incorrectly evaluated size of the gamboge spherules to be a culprit of the difference and asked Perrin to check the assumption with additional experiments and using the viscosity formula introduced in his own dissertation. The result was a discrepancy that neither Einstein nor Perrin settled any further. In this communication, based on the survey of developments in colloid and polymer science and their comparison with relevant experiments, an explanation of the dilemma is given that now, after more than a century, proves Einstein correct. The comparison was de facto possible during his lifetime. (shrink)

After 1905, Einstein's miraculous year, physics would never be the same again. In those twelve months, Einstein shattered many cherished scientific beliefs with five extraordinary papers that would establish him as the world's leading physicist. This book brings those papers together in an accessible format. The best-known papers are the two that founded special relativity: On the Electrodynamics of Moving Bodies and Does the Inertia of a Body Depend on Its Energy Content? In the former, Einstein showed that absolute time (...) had to be replaced by a new absolute: the speed of light. In the second, he asserted the equivalence of mass and energy, which would lead to the famous formula E = mc 2 . The book also includes On a Heuristic Point of View Concerning the Production and Transformation of Light , in which Einstein challenged the wave theory of light, suggesting that light could also be regarded as a collection of particles. This helped to open the door to a whole new world--that of quantum physics. For ideas in this paper, he won the Nobel Prize in 1921. The fourth paper also led to a Nobel Prize, although for another scientist, Jean Perrin. On the Movement of Small Particles Suspended in Stationary Liquids Required by the Molecular-Kinetic Theory of Heat concerns the Brownian motion of such particles. With profound insight, Einstein blended ideas from kinetic theory and classical hydrodynamics to derive an equation for the mean free path of such particles as a function of the time, which Perrin confirmed experimentally. The fifth paper, A New Determination of Molecular Dimensions , was Einstein's doctoral dissertation, and remains among his most cited articles. It shows how to calculate Avogadro's number and the size of molecules. These papers, presented in a modern English translation, are essential reading for any physicist, mathematician, or astrophysicist. Far more than just a collection of scientific articles, this book presents work that is among the high points of human achievement and marks a watershed in the history of science. Coinciding with the 100th anniversary of the miraculous year, this new paperback edition includes an introduction by John Stachel, which focuses on the personal aspects of Einstein's youth that facilitated and led up to the miraculous year. (shrink)

High‐precision tumor targeting with conventional therapeutics is based on the concept of the ideal drug as a “magic bullet”; this became possible after techniques were developed for production of monoclonal antibodies (mAbs). Innovative DNA technologies have revolutionized this area and enhanced clinical efficiency of mAbs. The experience of applying small‐size recombinant antibodies (monovalent binding fragments and their derivatives) to cancer targeting showed that even high‐affinity monovalent interactions provide fast blood clearance but only modest retention time on the target antigen. Conversion (...) of recombinant antibodies into multivalent format increases their functional affinity, decreases dissociation rates for cell‐surface and optimizes biodistribution. In addition, it allows the creation of bispecific antibody molecules that can target two different antigens simultaneously and do not exist in nature. Different multimerization strategies used now in antibody engineering make it possible to optimize biodistribution and tumor targeting of recombinant antibody constructs for cancer diagnostics and therapy. BioEssays 30:904–918, 2008. © 2008 Wiley Periodicals, Inc. (shrink)

A marked feature of eukaryotic programmed cell death is an early drop in mitochondrial transmembrane potential. This results from the opening of permeability transition pores, which are composed of adenine nucleotide translocators and mitochondrial porins. The latter share striking similarites with bacterial porins, (including down‐regulation of their pore size by purine nucleotides), suggesting a common origin. The porins of some invasive bacteria play a crucial role during their accommodation inside the host cell and this co‐existence resembles the endosymbiotic origin of (...) mitochondria. The above observations suggest that early in eukaryotic evolution, former invaders may have used porin‐type channels to enter their host and to induce its death when the levels of its cytoplasmic purine nucleotides were dropped. The appearance of adenosine nucleotide translocators in the primitive eukaryotes, which permitted usage of the oxidative metabolism of the invaders, provided the basis for the permeability transition phenomena, now linked to the apoptotic process. Bcl‐2‐type molecules, being able to modulate the permeability transition pores by interaction with adenosine nucleotide translocators, may have played an essential role in conferring a means of controlling apoptosis. (shrink)

The goal of synthetic biology is to create artificial organisms. To achieve this it is essential to understand what life is. Metabolism-replacement systems, or (M, R)-systems, constitute a theory of life developed by Robert Rosen, characterized in the statement that organisms are closed to efficient causation, which means that they must themselves produce all the catalysts they need. This theory overlaps in part with other current theories, including autopoiesis, the chemoton, and autocatalytic sets, all of them invoking some idea of (...) closure. A simple model of an (M, R)-system has been implemented in the computer, and behaves in ways that may shed light on the requirements for a prebiotic self-organizing system. In addition to a trivial steady state in which nothing happens, it can establish a non-trivial steady state in which all intermediates have finite concentrations, with their rates of degradation balanced by their rates of synthesis. The system can be regenerated from the set of food components plus a single intermediate, and maintain itself in that state indefinitely, despite continuous degradation. At the very low compartment volumes that may have existed in prebiotic conditions, for example in cavities in minerals, or in micelles formed by simple amphiphiles, statistical fluctuations in the numbers of molecules need to be taken into account. With the stochastic approach there is no non-trivial steady state in strict mathematical terms, because the system will always collapse to the trivial state after sufficient time. However, the average time before collapse is so long for volumes greater than $10^{-19}\;{\textsc{l}}$ (much smaller than the volume of the order of $10^{-15}\;{\textsc{l}}$ for a typical bacterial cell) that for practical purposes the self-maintaining state of non-null concentrations becomes significant, recalling the situation of bistability that is observed in deterministic analysis. In turn, there exists a minimum size below which the self-organizing system cannot maintain itself on chemically relevant time scales. The value of the critical volume depends on the particular concentrations and rate constants assumed, but the principle could apply generally. (shrink)

Imagine your body is populated by billions of respirocytes capable of delivering 236 times more oxygen than your natural red blood cells. These mechanical, micron sized spheres are appropriately programmed by your physician to meet your personal requirements, be it the treatment of anemia or the enhancement of your physical abilities. Robert Freitas’ vision of such artificial blood cells comprised of nanometer-scale components was published in 1998 in a peer-reviewed medical journal, and was the first medical nanorobot design (...) paper to be published.The fact that this proposal for a future blood substitute was accepted as worthy of publication in a scientific journal, despite the inventor's explicit statement that such a device could not be built at the time, clouds the criteria upon which an informed opinion about the feasibility of such devices could be formed. In that respect, the idea of respirocytes formidably testifies to the current “blurring of fact and fiction” occurring in the field of nanotechnology. (shrink)

Until quite recently, recombinant DNA technology was not able to deal with DNA molecules larger than 20–40 kb. This is a serious limitation for the study of mammalian, and in particular human genomes whose total length is approx. 3 × 106 kb, since the best resolution of genetic and chromosomal analysis is usually the rough equivalent of 1000–5000 kb. Three recently developed methods promise to bridge this gap: pulsed field gel electrophoresis, which can analyze megabase‐sized DNA fragments; cloning (...) in yeast, which can clone and propagate DNA fragments of several hundred kb; and jumping libraries, which allow ‘jumping’ over large distances along the chromosome. This review presents the current status of these very promising technologies. (shrink)

Magnetic resonance imaging (MRI) is an imaging technique with a rapidly expanding application range. This methodology, which relies on quantum physics and substance magnetic properties, is now being routinely used in the clinics and medical research. With the advent of measuring functional brain activity with MRI (functional MRI), this methodology has reached a larger section of the neuroscience community (e.g. psychologists, neurobiologists). In the past, the use of MRI as a biomarker or as an assay to probe tissue pathophysiological condition (...) was limited. However, with the new applications of MRI: molecular imaging, contrast‐enhanced imaging and diffusion imaging, MRI is turning into a powerful tool for in vivo characterization of tissue pathophysiology. This review focuses on the diffusion MRI. Although it only measures the averaged Brownian translational motion of water molecules, using different analysis schemes, one can extract a wide range of quantitative indices that represent tissue morphology and compartmentalization. Statistical and visualization routines help to relate these indices to biologically relevant measures such as cell density, water content and size distribution. The aim of this review is to shed light on the potential of this methodology to be used in biological research. To that end, this review is intended for the non‐MRI specialists who wish to pursue biological research with this methodology. We will overview the current applications of diffusion MRI and its relation to cellular biology of brain tissue. BioEssays 30:1235–1245, 2008. © 2008 Wiley Periodicals, Inc. (shrink)

Eukaryotic DNA replication initiates at multiple origins. In early fly and frog embryos, chromosomal replication is very rapid and initiates without sequence specificity. Despite this apparent randomness, the spacing of these numerous initiation sites must be sufficiently regular for the genome to be completely replicated on time. Studies in various eukaryotes have revealed that there is a strict temporal separation of origin “licensing” prior to S phase and origin activation during S phase. This may suggest that replicon size must be (...) already established at the licensing stage. However, recent experiments suggest that a large excess of potential origins are assembled along chromatin during licensing. Thus, a regular replicon size may result from the selection of origins during S phase. We review single molecule analyses of origin activation and other experiments addressing this issue and their general significance for eukaryotic DNA replication. BioEssays 25:116–125, 2003. © 2003 Wiley Periodicals, Inc. (shrink)

Mitochondrial function and biogenesis depend on the transport of a large variety of proteins, ions, and metabolites across the two surrounding membranes. While several specific transporters are present in the inner membrane, transport processes across the outer membrane are less understood. Recent studies reveal that the number of outer membrane channels and their transport mechanisms are more diverse than originally thought. Four protein‐conducting channels promote transport of distinct sets of precursor proteins across and into the outer membrane. The voltage‐dependent anion (...) channel (VDAC) forms the major channel for small hydrophilic molecules. In addition, three channels with yet unknown substrate specificity exist in the outer membrane. In this review, we outline the emerging functional diversity, selectivity, and regulation of mitochondrial outer membrane channels. The presence of several channel‐forming proteins challenges the traditional view that the outer membrane forms an unspecific size‐exclusion filter for the flux of small hydrophilic molecules. (shrink)

Structural biology has experienced several transformative technological advances in recent years. These include: development of extremely bright X-ray sources and the use of electrons to extend protein crystallography to ever decreasing crystal sizes; and an increase in the resolution attainable by cryo-electron microscopy. Here we discuss the use of these techniques in general terms and highlight their application for biological filament systems, an area that is severely underrepresented in atomic resolution structures. We assemble a model of a capped tropomyosin-actin minifilament (...) to demonstrate the utility of combining structures determined by different techniques. Finally, we survey the methods that attempt to transform high resolution structural biology into more physiological environments, such as the cell. Together these techniques promise a compelling decade for structural biology and, more importantly, they will provide exciting discoveries in understanding the designs and purposes of biological machines. Structural biology is undergoing technological advancements that now reveal the structures of previously inaccessible biological machines. Microfocus synchrotron beamlines, X-ray free electron lasers, and MicroED cope with vanishingly small crystals, while cryo-electron microscopy targets single molecules at near atomic resolution. These advances promise an exciting decade for structural biology. (shrink)

In the 1970s, R.D. MacElroy coined the term ‘extremophile’ to describe microorganisms that thrive under extreme conditions (MacElroy 1974). This hybrid word transliterates to ‘love of extremes’ and has been studied as a straightforward concept for the past 40 years. In this paper, we discuss several ways the term has been understood in the scientific literature, each of which has different consequences for the distribution and importance of extremophiles. They are, briefly, Human-Centric, at the Edge of life’s habitation of Morphospace, (...) by appeal to Statistical Rarity, described by Objective Limits, and at the Limits of Impossibility for metabolic processes. Importantly, these concepts have co-existed, unacknowledged and conflated, for decades. Confusion and equivocation threaten to follow from the wildly varied inclusion or exclusion of organisms as extremophiles depending on the concept used. Under some conceptions, entire kinds of extremophiles become meaningless. Since our understanding of how life works is shaped by what we take to be its extremes, clarifying extremophily is key for many large-scale projects in biology, ecology, biotechnology and astrobiology. In what follows, we proceed as if a noncontroversial account of life is possible and that it is possible to find complex chemistry in the Universe that is similar enough to Life on Earth such that both may be considered instances of ‘life’ (but see Mariscal & Doolittle 2018). We raise, but do not address, the questions of whether the distribution of Life on Earth is representative of what we may find elsewhere in the Universe, whether the same kinds of extremophiles would exist given a replay of the tape of life. Additionally, each of these concepts assumes life based on some sort of biochemistry in this universe, effectively setting aside claims made by some artificial life proponents that their digital organisms are genuine examples of life (Langton 1989, Ray 1995). On the distinction between extremophilic and extremotolerant, we note that all accounts accept the latter as a broader category than the former, since ‘phily’ means love and tolerance is a prerequisite for love under any conception. Indeed, there will be many extremely impoverished environments where tolerance is the only option and thriving is precluded, e.g. Bacillus marismortui was extracted and grown from 250-million-year-old salt crystals in the Permian Salado Formation in an inactive yet persistent state (Vreeland et al., 2000). We also note that extremophily, as a functional category, is potentially applicable at many levels of the biological hierarchy. Extremophily at one level does not necessarily extend to higher and lower levels. For instance, a microorganism in isolation might be quite intolerant to certain environmental conditions yet flourish when subjected to the same conditions as a community or natural biofilm. Alternatively, a protein molecule might be quite stable or active under certain conditions even if the optimal environment for the organism containing it is far more mesophilic. There is an industry of artificially selecting organisms and proteins to adapt to extreme environments (see van den Burg & Eijsink 2002), providing some justification to consider ‘functioning at extremes’ as a worthwhile category of investigation. Finally, we also note certain physico-chemical ranges are rarely considered with respect to extremophily – timespan, size, nutrient availability (Hoehler & Jørgensen 2013), etc. – as well as some biological parameters – abundance, isolation, competition, etc. Perhaps scientific interest must also come into play as to the reason these criteria are not considered relevant. We return to this issue later. In the next section, we give five definitions of extremophily, show their benefits, drawbacks, and unintended yet unavoidable consequences. These arguments are summarized in Table 1 and represented visually in Figures 1 and 2. Given research on polyextremophiles, it seems Figure 2 is a more plausible representation of the state of current knowledge than Figure 1 (Harrison et al. 2013). Life is patchily distributed across various dimensions, which may reflect its contingent history, poor sampling, or (perhaps) fundamental limits. Figure 3 shows the conceptual flowchart for all of these views. In the following section, we take a step back to ask whether we should choose between these definitions and how such a judgment could be made. We argue for a limited pluralism, in which some, but not all, of the concepts are acceptable relative to certain practical and theoretical aims. (shrink)

The theory of beauty has always rested on the representation of the infinite, understood in its finite expression and perceptible through the senses. The relationship of beauty to truth, of art to science, is inevitably modified with the new way of treating the infinite in the modern conception of the world. Non-classical science works with the notions of “infinitely large” and “infinitely small,” modifying their meanings in terms of experimental observations. We put these words in quotation marks because the Whole (...) may be considered as finite or infinite according to the angle from which it is viewed: the “infinitely small” only becomes so in determined circumstances, for example, when we consider the extended and discrete elements of space and time in a macroscopic approximation, as infinitely small elements of perpetual motion. Modern science studies these two poles of being—the Whole and its parts—in their interaction, admitting the dependence of macroscopic and even cosmic processes with regard to the processes being created in infinitely small spheres (or, according to another interpretation, finite but extremely small). However, as characteristic of our time as these concepts are—most often hypothetical—they nonetheless express a very old historical tradition that contemporary retrospection, turned toward classical science and the past of science in general, allows us to discern very clearly. All the culture of the past was dominated by the principle of the authority of the Whole over its parts. In peripatetic cosmology and physics, individual processes depended on the cosmic harmony of the center and frontiers of the universe, on the spheres and places toward which bodies tend. This authority of the general law, of universal harmony, of the system hinging on individual processes, is confirmed in Aristotle's Physics, but not only there: we find it in almost all the thinkers of antiquity. On the plane of general logic, it received expression in the Hegelian concept of the true infinite, a concept constituting to a high degree the philosophical equivalent of classical science. In Hegel's time, this last was already drawing away somewhat from the idea of an absolute and strict subordination of elementary processes to integrating systems and general laws, laws being realized through the probability of microprocesses, thus statistical laws, and whose exact application ignored individual acts, for example, the mechanism of molecules in thermodynamics. The statistical theory of heat has rendered continual a discrete microcosm—for the movement of individual molecules it substituted the average speed of the molecules—and continual laws became supreme points determining macroscopic processes. These laws had a differential nature. In other words, they prescribed the defined relationships between the infinitely small increases in size. Also, the schema of the classic law consisted in defining infinitely small processes by an infinitely large integral legality because of the number of processes. The infinitely true of Hegel is the actual infinite being realized in each of its finite elements; it is the subjection of the finite element to the infinite. (shrink)

Preparative and analytical methods developed by separation scientists have played an important role in the history of molecular biology. One such early method is gel electrophoresis, a technique that uses various types of gel as its supporting medium to separate charged molecules based on size and other properties. Historians of science, however, have only recently begun to pay closer attention to this material epistemological dimension of biomolecular science. This paper substantiates the historiographical thread that explores the relationship between modern (...) laboratory practice and the production of scientific knowledge. It traces the historical development of gel electrophoresis from the mid-1940s to the mid-1960s, with careful attention to the interplay between technical developments and disciplinary shifts, especially the rise of molecular biology in this time-frame. Claiming that the early 1950s marked a decisive shift in the evolution of electrophoretic methods from moving boundary to zone electrophoresis, I reconstruct various trajectories in which scientists such as Oliver Smithies sought out the most desirable solid supporting medium for electrophoretic instrumentation. Biomolecular knowledge, I argue, emerged in part from this process of seeking the most appropriate supporting medium that allowed for discrete molecular separation and visualization. The early 1950s, therefore, marked not only an important turning point in the history of separation science, but also a transformative moment in the history of the life sciences as the growth of molecular biology depended in part on the epistemological access to the molecular realm available through these evolving technologies. (shrink)

The explanation of the phenomenon of Brownian motion, given by Einstein in 1905 and based on the kinetic–molecular conception of matter, is considered one of the fundamental pillars supporting atomism in its victorious struggle against phenomenological physics in the early years of this century. Despite the importance of the subject, there exists no specific study on it of sufficient depth. Generally speaking, most histories of physics repeat the following scheme: the discovery made by Robert Brown in 1827 , of the (...) continuous movement of small particles suspended in a fluid did not arouse interest for a long time. Finally, at the close of the century, Gouy's research brought it to the attention of the physicists. Gouy was convinced that Brownian motion constituted a clear demonstration of the existence of molecules in continuous movement. Nevertheless, he did not work out any mathematized theory that could be subjected to quantitative confirmation. All nineteenth-century research remained at the qualitative level and yet it was able to clarify some general characteristics of the phenomenon: the completely irregular, unceasing, motion of the particles is not produced by external causes. It does not depend on the nature of the particles but only on their size. The first significant measurements, carried out by Felix Exner in 1900, appeared to deny the possibility of reconciling the kinetic theory with Brownian motion. The discovery of the ultra-microscope then allowed Zsigmondy to perceive the presence of movements, which were completely analogous to Brown's, in the particles of the colloids; these movements were rather smaller in size than those invesigated up to then. Thus Zsigmondy aroused interest in the phenomenon. Finally, in 1905, Einstein succeeded in stating the mathematical laws governing the movements of particles on the basis of the principles of the kinetic–molecular theory. The following year Smoluchowski arrived at conclusions which corresponded to Einstein's. These laws received a first, rough confirmation in the years immediately following by the work of The Svedberg, Seddig and, for some historians, Henri. Then in 1908 Jean Perrin gave it a definitive confirmation. (shrink)

Most cells communicate with their immediate neighbors through the exchange of cytosolic molecules such as ions, second messengers and small metabolites. This activity is made possible by clusters of intercellular channels called gap junctions, which connect adjacent cells. In terms of molecular architecture, intercellular channels consist of two channels, called connexons, which interact to span the plasma membranes of two adjacent cells and directly join the cytoplasm of one cell to another. Connexons are made of structural proteins named connexins, (...) which compose a multigene family. Connexin channels participate in the regulation of signaling between developing and differentiated cell types, and recently there have been some unexpected findings. First, unique ionic‐ and size‐selectivities are determined by each connexin; second, the establishment of intercellular communication is defined by the expression of compatible connexins; third, the discovery of connexin mutations associated with human diseases and the study of knockout mice have illustrated the vital role of cell‐cell communication in a diverse array of tissue functions. (shrink)

The purpose of this paper is to present an overview of emergent examples of macroscopic quantum phenomena. While quantum theory asserts that such quantum behaviors as superposition, entanglement, and coherence are possible for all objects, assumptions that quantum processes operate exclusively within the quantum realm have contributed to on-going bias toward presumed primacy of classical physics in the macroscopic realm. Non-trivial quantum macroscopic effects are now recognized in the fields of biology, quantum physics, quantum computing, quantum astronomy, and neuroscience, with (...) implications for medicine, psychology and sociology. Robust examples of macroscopic quantum coherence and entanglement contain unmistakable biological advantages, such as are observed in the green sulphur bacteria photosynthesis transfer mechanism, and in the navigational system of the European Robin. Macroscopic quantum processes in the form of an olfactory electron tunneling mechanism best account for the otherwise inexplicable difference observed in the odor of identically-shaped molecules. Evidence of reverse-direction causality is apparent in experiments with large numbers of photons and human subjects. Entanglement, retrocausality, and superposition of states are suggested as causal factors to account for increases in efficacy of the placebo effect. Alternate histories of "flashbulb memories" and embodied cognition are considered as possible examples of superposition of states in a holographic multiverse in which the many worlds of the multiverse and the many worlds of quantum mechanics might just be one and the same thing. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}. (shrink)

Developmental biology is the science of explaining how a variety of interacting processes generate the heterogeneous shapes, size, and structural features of an organism as it develops rom embryo to adult, or more generally throughout its life cycle (Love, 2008b; Minelli, 2011a). Although it is commonplace in philosophy to associate sciences with theories such that the individuation of a science is dependent on a constitutive theory or group of models, it is uncommon to find presentations of developmental biology making reference (...) to a theory or theories of development. For example, in the third edition of Essential Developmental Biology (Slack, 2013), three families of approaches are described (developmental genetics, experimental embryology, and molecular and cell biology), and the appendix contains a catalogue of ‘key molecular components’ (genes, transcription factor, families, inducing factor families, cytoskeleton, cell adhesion molecules, and extracellular matrix components); however, no standard theory or group of models provides a theoretical scaffolding to the book nor is any mentioned. (shrink)

What we observe, through our usually limited lens, is that differential growing of space determines forms -characterized by their shape, size and coloration. As non-Euclidean geometrical mathematics have proclaimed: forms are manifestations of the curvature of space. Physics and other natural laws impose mathematical structural restrictions to biological forms. The molecules comprising any living form become arranged in specific ways in response to physical forces as well as chemical and biochemical conditions. Over time, such forms inherit additional historical restrictions (...) that make up their meaning, their semiotics. Color does not escape from this orthogenic reality. In this study, we present the colored pattern of the connexivum of Triatoma maculata, an insect vector of the etiologic agent of Chagas disease. This model is used as an example to appreciate mimicry under a heterodox and provocative approach. We unveil that beyond 1) mathematical and 2) historical semiotic restrictions of T. maculata mimesis of a yellowish-black alternating pattern, there are also 3) artistic interpretations; where metaphysics of life, beyond human perspective, is included. (shrink)

For many years, there has been a gap in our capacity to study the structure and organization of chromosomal DNA molecules. The very small genomes of some viruses and bacteriophages (≤ 50,000 bp or 50 kb) are amenable to analysis by conventional gel electrophoresis, while the extremely large DNA molecules (> 100,000 kb) comprising the chromosomes of higher eukaryotes have been analysed under the light microscope, using a range of banding and in situ hybridization techniques. However, intact DNA (...) molecules with sizes between these two extremes have been largely inaccessible experimentally. This gap has recently been bridged with the development of two‐dimensional electrophoretic procedures that allow the separation and purification of chromosome‐sized DNA molecules ranging from ∼ 50 kb to several thousand kb.1–3 There are currently two variations of the technique in use: pulsed field gradient (PFG) gel electrophoresis1,2 and orthogonal‐field‐alteration gel electrophoresis (OFAGE).3 Both are based on a common principle, differing primarily in the geometry of the electrodes. Already, they have been employed to determine the approximate chromosome sizes and numbers for a variety of lower eukaryotes, including yeast and several protozoa.2–10 These ‘molecular karyotypes’ provide fundamental information about the genomic organization of each organism, and allow very rapid construction of linkage maps. Surprisingly, they have also revealed a remarkable plasticity in the genomes of several lower eukaryotes. (shrink)

Predicting the binding mode of flexible polypeptides to proteins is an important task that falls outside the domain of applicability of most small molecule and protein-protein docking tools. Here, we test the small molecule flexible ligand docking program Glide on a set of 19 non-α-helical peptides and systematically improve pose prediction accuracy by enhancing Glide sampling for flexible polypeptides. In addition, scoring of the poses was improved by post-processing with physics-based implicit solvent MM- GBSA calculations. Using the best RMSD among (...) the top 10 scoring poses as a metric, the success rate (RMSD ≤ 2.0 \textbackslash AA for the interface backbone atoms) increased from 21 with default Glide SP settings to 58 with the enhanced peptide sampling and scoring protocol in the case of redocking to the native protein structure. This approaches the accuracy of the recently developed Rosetta FlexPepDock method (63 success for these 19 peptides) while being over 100 times faster. Cross-docking was performed for a subset of cases where an unbound receptor structure was available, and in that case, 40 of peptides were docked successfully. We analyze the results and find that the optimized polypeptide protocol is most accurate for extended peptides of limited size and number of formal charges, defining a domain of applicability for this approach. (shrink)

Stomata are microscopic pores on the surface of land plants used for gas and water vapor exchange. A pair of highly specialized guard cells surround the pore and adjust pore size. Studies in Arabidopsis have revealed that cell–cell communication is essential to coordinate the asymmetric cell divisions required for proper stomatal patterning. Initial research in this area identified signaling molecules that negatively regulate stomatal differentiation. However, genes promoting cell‐fate transition leading to mature guard cells remained elusive. Now, three closely (...) related basic helix–loop–helix (bHLH) proteins, SPEECHLESS, MUTE and FAMA have been identified as positive regulators that direct three consecutive cell‐fate decisions during stomatal development. The identification of these genes opens a new direction to investigate the evolution of stomatal development and the conserved functions of bHLH proteins in cell type differentiation adopted by plants and animals. BioEssays 29:861–870, 2007. © 2007 Wiley Periodicals, Inc. (shrink)

The objective of this article is to demonstrate how the historical debate between materialism and idealism, in the field of Philosophy, extends, in new clothes, to the field of Quantum Physics characterized by realism and anti-realism. For this, we opted for a debate, also historical, between the realism of Albert Einstein, for whom reality exists regardless of the existence of the knowing subject, and Niels Bohr, for whom we do not have access to the ultimate reality of the matter, unless (...) conditioning it to the existence of an observer endowed with rationality, position adopted in the Interpretation of Complementarity – posture that was expanded in 1935 when Bohr assumed a “relationalist” conception, according to which the quantum state is defined by the relationship between the quantum object and the entire measuring device. This is an extremely important debate, as it further consolidates the results of nascent Quantum Mechanics, guaranteeing Bohr the leadership of the orthodoxy based on the interpretation of complementarity. Here, when dealing with Quantum Theory, we will not make any distinction between the terms Quantum Physics, Quantum Theory or Quantum Mechanics. The entire discussion will be held under the name “Quantum Theory”. Theory that tries to analyze and describe the behavior of physical systems of reduced dimensions, close to the sizes of molecules, atoms and subatomic particles. We hope that the reader will appreciate the genius of these two titans in this field of Physics when they magnificently formulate the arguments that support the object of their defenses. (shrink)

There have been occasions when the publication of a particular book has had a singular impact on the conceptual world of the chemist. Sometimes the publication occurs near the beginning of a major change in discourse, and sometimes more near the end. Jean Perrin published Les Atomes in 1913 as the culmination of a century-long controversy over the size and physical reality of atoms and molecules. After its publication almost all chemists and physicists agreed that atoms and molecules (...) of the size we currently understand to be appropriate are real physical objects. The story of the background, development, publication, content and response to Les Atomes forms the text of this paper. The content of Les Atomes is also the basis for extended reflection on the philosophical significance of the work of Jean Perrin. (shrink)

Sexual reproduction is a composite, not a singular, phenomenon and as such can be subdivided into a number of componentsi.e. fusion, recombination, fission, and the male-female phenomenon. These components can evolve independently, though any evolutionary change in one component is likely to influence the future evolution of the other components. The ambiguity that surrounds the term ‘sex’ due to a failure to recognise the composite nature of sexual reproduction has led to considerable confusion in past discussions of the evolution of (...) the phenomenon. This paper considers the possible chronological interaction of the components of sexual reproduction both with each other and with the sequence of selective pressures that seem likely to have acted. This chronological approach is used to consider: the origin of sexual reproduction; the evolution of sexual reproduction in the common ancestor of the procaryotes and eucaryotes; the modification of the ancestral system in the procaryote line following the procaryote-eucaryote dichotomy; and the modification of the ancestral system in the eucaryote line up to the origin of the male-female phenomenon.It is suggested that the fusion and recombination of the first living organisms were chronological continuations of the fusion and recombination of complex organic molecules that led up to the origin of life. The evolution of the third major component of sexual reproductioni.e. fission , by definition coincided with the origin of life. Initial selection on the components of sexual reproduction are likely to have been related to the optimum manifestations of size, complexity, diversity, multiplication, and distribution. Resultant early evolutionary trends are likely to have been: selective fusion between more-similar organisms; increase in number of fissions per fusion; and less recombination.The procaryote-eucaryote dichotomy is argued to have evolved in response to the increasing cellular problems of packing and replicating an increasing amount of hereditary material. The evolution of a single circular hereditary organelle in the procaryote line is argued to have led to the loss of total fusion and the specialisation of individuals into either donors or recipients. The donor-recipient phenomenon of procaryotes is directly analogous to the male-female phenomenon of eucaryotes and leads to parallel evolution due to sexual selection in both groups. In the eucaryote line the ancestral mechanism of sexual reproduction is argued to have persisted through, but to have been greatly modified by, the evolution of complex machinery for the handling of multiple hereditary organelles at cell division and reduction division. The evolutionary modification of the ancestral system of sexual reproduction is suggested to have led in eucaryotes to the evolution of: the species phenomenon; allelic recombination; and the male-female phenomenon. (shrink)

Nature's simplest atom and mother of all matter, hydrogen feeds the stars as well as interlaces the molecules of their biological descendants – to whom it ultimately whispers the secrets of quantum reality. Hydrogen’s most prevalent earthly guise lies within the composition of water. A slight electrical disturbance can split water into hydrogen and oxygen gas, resulting in diaphanous bubble clouds slowly rising towards the liquid’s surface. Though the founding fathers of electrochemistry posited that the mass of liberated bubbles (...) is directly proportional to the input voltage, certain modes of electrolysis release more energy than is spent. One such mode involves water’s Janus-faced capacity to react as either an acid or a base. Emanating from an array of electrodes at the bottom of a water-filled chamber, strings and strata of hydrogen bubbles meticulously trace their emergent surroundings. In addition to eddy formations incited by a bubble's rapid growth and subsequent detachment from the electrode surface, acoustic vibrations permeate the two-phase fluid. As the sonic frequency and amplitude rises, the hydrogen bubbles start to coalesce with one another. When the sound field reaches maximum intensity, it can trap bubbles within its antinodes. The vibrations are generated both by transducers and by the bubbles themselves, which emit frequencies ranging from the audible spectrum to as high as 800 kHz. A white laser sheet scans and illuminates the hydrogen bubble trajectories. Each quivering bubble-lens divides the white light into its constituent spectrum of colors. While scanning, the laser sheet also swiftly pulsates and thereby extends the perceivable resolution of micro-momentary bubble dynamics. Before it even begins to map out its vibratory environment, a bubble goes through various stages of spatio-temporal evolution. During the first phase of growth, a bubble nucleus inflates linearly with time. At the second stage, bubble growth is limited by the diffusion of gas within the liquid, causing its size to increase as the square root of time. The final phase before detachment is limited by the kinetics of dissolved gas production, causing the bubble to grow as the cube root of time.1 Beyond macroscopically observable bubbles, an expanse of nanobubbles hides within the water’s internal architecture. Some researchers presume that these nanobubbles of dissolved gas are the carriers of water’s magnetic ‘memory’, enabling electromagnetic fields to saturate its innards for hours and even days after their initial appearance. In the seas and oceans, the lingering presence of electromagnetic fields photonically imparted by sunlight, triggers the electrolysis responsible for most of the Earth’s hydrogen. An essential form of photosynthesis, solar water splitting is the cleanest and most efficient means imaginable for generating and storing energy. —Evelina Domnitch & Dmitry Gelfand *** Animals and plants are formed in earth and in water because there is water in earth, and there is pneuma in water, and there is soul heat in all pneuma ; so that in a way all things are full of soul. Hence plants and animals quickly form once this gets enclosed; and when this enclosing happens, when the corporeal liquids get heated, a sort of frothy bubble is formed. Now the difference between the various creatures which are produced in this way are due to the stuff which makes up the envelope around the soul-source.2 Throwing light into this pneumatic spray of perdurances, which would otherwise swarm below the threshold of human visibility, Evelina Domnitch and Dmitry Gelfand’s Hydrogeny saturates the viewer’s sensorial space with the nano-architectures of froth. Straddling the cell wall between scientific enquiry and artistic praxis, Hydrogeny , beckons a recasting of Lucretius' clinamen in tune with the technologies of the modern observer. For Lucretius it was the indeterminate swerving of an atomistic layer of reality which accounted for the unpredictability of change and the existence of free will. Taken up by Harold Bloom to describe the swerving of cultural production from that which has already been made, the idea has since been textually redressed by Lacan, Derrida, Serres, Deleuze, Nancy, and Badiou. Here we have been given a kaleidoscopic technique for refining and expanding awareness of our enmeshment with so many nested, atomistic layers of object-bubbles—of things—as Aristotle might say,“full of soul.” The gravitational pull of Hydrogeny ushers a de-centered human spectatorship to the ever more intimate recesses of what media philosopher N. Katherine Hayles calls our capacity for “deep attention.”3 Vaporous attention suspended and re-oriented. Microscopic as these diaphanous waves are, the calling they produce is anything but inconsequential. Evelina Domnitch and Dmitry Gelfand are two-thirds of the Amsterdam-based Art–Science Labratory, Optofonica , an atelier initiated by the Italian interdisciplinary artist TeZ in 2006. Follow more of their work at www.portablepalace.com —Isaac Linder NOTES (1) cf. Brandon, Kelsall, Levine, & Smith. “Interfacial Electrical Properties of Electrogenerated Bubbles.” Journal of Applied Electrochemistry 15 (1985):485-493. (2)Aristotle, On the Generation of Animals, 762a18, tr. A. L. Peck (Cambridge, MA: Loeb Classical Library, 1942). (3)“ My article on hyper and deep attention ,” N. Katherine Hayles, accessed on September 14, 2011. (shrink)