Deterministic hypotheses on the origin of life and of its reproduction

Transfer functions of proteinoid microspheres

Proteinoids, or thermal proteins, are inorganic entities formed by heating amino acids to their melting point and commencing polymerisation to form polymeric chains. Typically, their diameters range from 1μm to 10μm. Some amino acids incorporated into proteinoid chains are more hydrophobic than others, leading proteinoids to cluster together when they are present in aqueous solutions at specific concentrations, allowing them to grow into microspheres. The peculiar structure of proteinoids composed of linked amino acids endows them with unique properties, including action-potential like spiking of electrical potential. These unique properties make ensembles of proteinoid microspheres a promising substrate for designing future artificial brains and unconventional computing devices. To evaluate a potential of proteinoid microspheres for unconventional electronic devices we measure and analyse the data-transfer capacities of proteinoid microspheres. In experimental laboratory conditions we demonstrate that the transfer function of proteinoids microspheres is a nontrivial phenomenon, which might be due to the wide range of proteinoid shapes, sizes, and structures.

Structural protein reorganization and fold emergence investigated through amino acid sequence permutations

Correlation between random amino acid sequences and protein folds suggests that proteins autonomously evolved the most stable folds, with stability and function evolving subsequently, suggesting the existence of common protein ancestors from which all modern proteins evolved. To test this hypothesis, we shuffled the sequences of 10 natural proteins and obtained 40 different and apparently unrelated folds. Our results suggest that shuffled sequences are sufficiently stable and may act as a basis to evolve functional proteins. The common secondary structure of modern proteins is well represented by a small set of permuted sequences, which also show the emergence of intrinsic disorder and aggregation-prone stretches of the polypeptide chain.

Integrity and biological activity of DNA after UV exposure

The field of astrobiology lacks a universal marker with which to indicate the presence of life. This study supports the proposal to use nucleic acids, specifically DNA, as a signature of life (biosignature). In addition to its specificity to living organisms, DNA is a functional molecule that can confer new activities and characteristics to other organisms, following the molecular biology dogma, that is, DNA is transcribed to RNA, which is translated into proteins. Previous criticisms of the use of DNA as a biosignature have asserted that DNA molecules would be destroyed by UV radiation in space. To address this concern, DNA in plasmid form was deposited onto different surfaces and exposed to UVC radiation. The surviving DNA was quantified via the quantitative polymerase chain reaction (qPCR). Results demonstrate increased survivability of DNA attached to surfaces versus non-adsorbed DNA. The DNA was also tested for biological activity via transformation into the bacterium Acinetobacter sp. and assaying for antibiotic resistance conferred by genes encoded by the plasmid. The success of these methods to detect DNA and its gene products after UV exposure (254 nm, 3.5 J/m(2)s) not only supports the use of the DNA molecule as a biosignature on mineral surfaces but also demonstrates that the DNA retained biological activity.

Evolutionary change - patterns and processes

The present review considered: (a) the factors that conditioned the early transition from non-life to life; (b) genome structure and complexity in prokaryotes, eukaryotes, and organelles; (c) comparative human chromosome genomics; and (d) the Brazilian contribution to some of these studies. Understanding the dialectical conflict between freedom and organization is fundamental to give meaning to the patterns and processes of organic evolution.

Hypotheses on a germline origin of antibody diversity. Possible applications: improvement of the efficiency of immune response and autoimmune disease treatment

In this paper, the antibody reaction is supposed to be due to the combination of a limited number of different antibodies against the epitopes of the antigen. In addition, the efficient part of the epitopes of proteins is assumed to be the size of dipeptides. The 400 different dipeptides would be distributed in two sets, those which are foreign to the host, against which would be directed antibodies, and those which are present in the proteins of the self, which would elicit no reaction. Each chain of the antibodies would recognise one aminoacid and 40 genes would be sufficient (20 for the light chains and 20 for the heavy chains) to code for the variable parts of the immunoglobulins against proteic antigens. With these hypotheses, the combination of antibodies against at least four different epitopes of the size of dipeptides can account for the main characteristics of the antibody reaction: response against any foreign proteic antigen and specificity. In fact, the epitopes have been found to be larger than dipeptides, several additional aminoacids are involved in the antibody-binding sites. Somatic mutations and VDJ recombinations are selected to give the maximal affinity for the antigens. However, these mechanisms have not been shown to create different specificities from the same V genes. Moreover, the phenomenon of heteroclisis and the decrease, due to mutations, of antigen-binding capacity of antibodies, sometimes observed, are better explained by the model proposed here than by the classical theory. The modification of the epitope subset of the self, by intrathymic injection of antibodies against particular pathogens, is proposed to improve the immune response when microorganisms develop immune escape mechanisms. On the other hand, in the case of autoimmune diseases, the displacement of autoantibodies against self-epitopes could be carried out by the injection into the thymus of specific anti-idiotypic antibodies.