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Biomedical subjects

A Brack

Publications and source records attributed to A Brack.

78 records · Page 5Linked to original sources
PubMed1975

Polymerization of amino acid methyl esters via their copper complexes.

Polymerization of glycine methyl ester catalyzed by cupric ions in organic solvents yields oligoglycines with a degree of polymerization up to none. With a trifunctional amino acid, the yield and degree of polymerization were much lower. Extension of this reaction to an aqueous medium was not successful even when copper ions were complexed with substances like montmorillonite or fatty acids. The prebiotic significance of this reaction is discussed.

Amino Acids↗
PubMedDate not supplied

Enantiomer enrichment in early peptides.

The two main ordered conformations of polypeptides, the alpha-helix and the beta-sheet, were considered as possible asymmetric supports for stereoselective processes leading to the enrichment in one enantiomer. alpha-Helices can accommodate residues of both chirality distributed in the same chain, whereas the formation of beta-sheets arises from the association of chain segments containing at least seven residues of the same chirality. When the residue composition departs from the racemic mixture, one handedness of the helix is favored, whereas the beta-sheet nuclei become predominantly of a unique chirality. Taking into account these observations, processes of enrichment specific for alpha- amd beta-structures were envisaged theoretically theoretically as well as experimentally.

Biological Evolution↗
PubMedDate not supplied

Studies of the influence of different cross-linking reagents on the immune response against a B-epitope.

We have previously shown that the carrier polytuftsin obtained by polycondensation of tuftsin, a naturally occurring macrophage activator, increases significantly the antibody response against a linked B-epitope. In the present work, we have studied the influence of different cross-linking reagents on the quality of the conjugation and on the immune response, at both B-cell and T-cell levels. We observed that the cross-linking method used for coupling the B-epitope to the carrier influences the immune response. A hypothesis is put forward to explain the differences observed.

Amino Acid Sequence↗
PubMedDate not supplied

Exo/Astrobiology in Europe.

The question of the chemical origins of life is engraved in the European scientific patrimony as it can be traced back to the pioneer ideas of Charles Darwin, Louis Pasteur, and more recently to Alexander Oparin. During the last decades, the European community of origin of life scientists has organized seven out of the twelve International Conferences on the Origins of Life held since 1957. This community contributed also to enlarge the field of research to the study of life in extreme environments and to the search for extraterrestrial life, i.e. exobiology in its classical definition or astrobiology if one uses a more NASA-inspired terminology. The present paper aims to describe the European science background in exo/astrobiology as well as the project of a European Network of Exo/Astrobiology.

Astronomy↗