In a publication of 1831 later seen as a milestone in the development of chemistry, Justus Liebig announced a new apparatus for the analysis of organic compounds and provided analytical results for fifteen substances. In this paper we used the detailed descriptions published by Liebig in 1837 to reconstruct his apparatus and methods for hydrogen, carbon and nitrogen analysis. Our replications of his analyses of racemic acid, cinchonine, narcotine, and urea reveal that his two pieces of apparatus give excellent results (...) for carbon and hydrogen content, but erratic results for nitrogen. The results corroborate the assessments of Liebig and his contemporaries, and show that the analytical method for carbon and hydrogen analysis was remarkably accurate. We offer this case, with its convincing replicability, not only to clarify the nature of Liebig's innovations, but also as a new model for understanding broader contested issues in the philosophy and sociology of science. Our analysis suggests that the great shift in science from gentlemanly avocation to professional vocation was tightly linked to laboratory practice, and not just to social networks and context. It also provides the basis for a critique of H. M. Collins's theory of the 'experimenters' regress'. (shrink)

Excerpt from Pasteur Et le Transformisme Il avait constaté que les racemates étaient formés d'un mélange de cristaux hémiédriques droits et gauches et, les ayant triés à la pince, il put isoler les hémiédriques gauches (qui étaient alors inconnus), et vérifier, ce qu'il prévoyait, qu'ils devaient dévier à gauche. About the Publisher Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art (...) technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works. (shrink)

Life is characterized by a selectivity for asymmetric molecules. A great deal of theoretical and experimental work has yet to explain why living organisms utilize only L‐amino acids in proteins and D‐sugars in RNA and DNA. Also unknown is how a form of life based on asymmetric molecules evolved from an environment containing a racemic mixture of prebiotic molecules. By what mechanism did this selectivity for asymmetric molecules take place?

Long since, people tried to solve the mystery of the way that led to the appearance and propagation of living entities. However, no harmonious understanding of this mystery existed, because neither the scientifically grounded source minerals nor the ambient conditions were proposed and because it was groundlessly taken that the process of living matter origination is endothermal. The Life Origination Hydrate Theory (LOH-Theory) first suggests the chemical way capable of leading from the specified abundant natural minerals to origination of multitudes (...) of multitudes of simplest living entities and gives an original explanation for the phenomena of chirality and racemization delay. The LOH-Theory covers the period up to origination of the genetic code. The LOH-Theory is grounded on the following three discoveries based on the available information and on the results of our experimental works performed using original instrumentation and computer simulations. (1) There is the only one triad of natural minerals applicable for exothermal thermodynamically possible chemical syntheses of simplest living-matter components. (2) N-base, ribose, and phosphdiester radicals and nucleic acids as whole are size-compatible with structural gas-hydrate cavities. (3) The gas-hydrate structure arises around amido-groups in cooled undisturbed systems consisting of water and highly-concentrated functional polymers with amido-groups.The natural conditions and historic periods favorable for simplest living matter origination are revealed. The LOH-Theory is supported by results of observations, biophysical and biochemical experiments, and wide application of original three-dimensional and two-dimensional computer simulations of biochemical structures within gas-hydrate matrix. The instrumentation and procedures for experimental verification of the LOH-Theory are suggested. If future experiments are successful, they, possibly, could be the first step on the way to industrial synthesis of food from minerals, i.e., to execution of the work that is performed by plants. (shrink)

D‐amino acids are being recognized as functionally important molecules in mammals. We recently identified endogenous D‐cysteine in mammalian brain. D‐cysteine is present in neonatal brain in substantial amounts (mM) and decreases with postnatal development. D‐cysteine binds to MARCKS and a host of proteins implicated in cell division and neurodevelopmental disorders. D‐cysteine decreases phosphorylation of MARCKS in neural progenitor cells (NPCs) affecting its translocation. D‐cysteine controls NPC proliferation by inhibiting AKT signaling. Exogenous D‐cysteine inhibits AKT phosphorylation at Thr 308 and Ser (...) 473 in NPCs. D‐cysteine treatment of NPCs led to 50% reduction in phosphorylation of Foxo1 at Ser 256 and Foxo3a at Ser 253. We hypothesize that in the developing brain endogenous D‐cysteine is as a physiologic regulator of NPC proliferation by inhibiting AKT signaling mediated by Foxo1 and Foxo3a. Endogenous D‐cysteine may regulate mammalian neurodevelopment with roles in schizophrenia and Alzheimer's disease (AD). (shrink)