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PubMed2006

[Physico-chemical determinants of physiOlogical evolution: from protocell to the human].

One of the key physiological problems of evolution is elucidation of the role of environmental inorganic factors in origin of life. A statement is substantiated that a highly significant event in evolution of life was the appearance of protocells with the K cytoplasm in K water reservoirs with their subsequent adaptation to the environment in which Na dominated. This step was accompanied by replacement of the cell envelope with the cell plasma membrane. Precursors of animals' elaborated mechanism of maintenance of the K-cytoplasm with Na-counterkation in the environment. In plants, Na remains a trace element, in animals the Na and K contents are approximately equal, but they are present in different fluid phases. In animals presence of Na+ in the external medium, K+ inside cells has become an initial pre-requisition for electrogenesis and appearance of asymmetrical cells. Electrogenesis of these cells has become a physiological pre-requisition for cell differentiation, the appearance of the nerve cell. Asymmetrical cell has provided development of absorption, digestion, excretion, respiration. Formation of the inner medium has become a prerequisite for establishment of homeostasis. Serum osmolality, sodium concentration, pH, Ca2+ are the most rigidly maintained constants in the blood serum of humans.

Animals↗
PubMed1995

Reactions involving carbamyl phosphate in the presence of precipitated calcium phosphate with formation of pyrophosphate: a model for primitive energy-conservation pathways.

The formation of carbamyl phosphate (CAP) in dilute solutions of cyanate (NCO-) and orthophosphate (Pi) was measured both in the absence and in the presence of a precipitated matrix of calcium phosphate (Pi.Ca). The second-order rate constant and the free energy of CAP synthesis were not modified by the presence of the solid matrix, indicating that synthesis occurs in the homogeneous Pi-containing solution. The elimination reaction of CAP to form NCO- and Pi followed first-order kinetics and the rate constant was the same whether or not calcium phosphate was present. Elimination was not complete, and the steady level of remaining CAP was that expected from the free energy of synthesis. The formation of pyrophosphate (PPi) was detected in CAP-containing medium only in the presence of calcium, showing a close correlation with the amount of precipitated Pi.Ca. Phosphorolysis of CAP followed a sigmoidal time course, compatible with adsorption of CAP to the solid matrix as a prelude to transphosphorylation. Addition of 5'-AMP and of short linear polyphosphates inhibited phosphorolysis of CAP. It is proposed that the presence of a solid phosphate matrix and the relative concentrations of cyano compounds, as well as those of nucleotides and inorganic polyphosphates, could have played a crucial role in the conservation of chemical energy of CAP and in its use in prebiotic phosphorylation reactions.

Adenosine Monophosphate↗
PubMed1995

Adsorption of 5'-AMP and catalytic synthesis of 5'-ADP onto phosphate surfaces: correlation to solid matrix structures.

A non-enzymatic formation of 5'-ADP starting from phosphorylation of 5'-AMP in the presence of either calcium phosphate or calcium pyrophosphate precipitates is reported. This reaction is taken as a model for the study of heterogeneous catalysis of transphosphorylation in prebiotic conditions. Experiments were performed in completely aqueous media and in media containing dimethyl sulfoxide (Me2SO), to simulate periods of dehydration in primitive aquatic environments. It has been observed that the nucleotide is adsorbed onto both calcium phosphate and calcium pyrophosphate in accordance with Langmuir isotherms. Adsorptive capacity and affinity of the precipitates for nucleotide are changed by the presence of Me2SO, suggesting that the interaction between biomonomers and surfaces can be modulated by the degree of hydration of the anionic components of these compounds. In completely aqueous environments, formation of 5'-ADP from 5'-AMP adsorbed on precipitates of calcium phosphate and calcium pyrophosphate is very small. However, in the presence of 60% Me2SO this synthesis increases by factors of 3 and 6 for surfaces of calcium phosphate and calcium pyrophosphate, respectively, and follows first-order kinetics. Determinations of free energy changes show that phosphorylation of 5'-AMP adsorbed to these precipitates is thermodynamically favorable. Depending on the precipitation time of the samples and the composition of the medium, structural analysis of these precipitates by electron and X-ray diffraction shows changes in their cristallinity grade. It is proposed that these changes are responsible for the modulation of the quantity of adsorbed nucleotides to the surface of solid matrices as well as the catalytic activity of the precipitates.

Adenosine Diphosphate↗
PubMed2002

Synthesis beyond the molecule.

Weak, noncovalent interactions between molecules control many biological functions. In chemistry, noncovalent interactions are now exploited for the synthesis in solution of large supramolecular aggregates. The aim of these syntheses is not only the creation of a particular structure, but also the introduction of specific chemical functions in these supramolecules.

Binding Sites↗
PubMed2001

Triple resonance solid state NMR experiments with reduced dimensionality evolution periods.

Two solid state NMR triple resonance experiments which utilize the simultaneous incrementation of two chemical shift evolution periods to obtain a spectrum with reduced dimensionality are described. The CO N CA experiment establishes the correlation of (13)C(i-1) to (13)C alpha(i) and (15)N(i) by simultaneously encoding the (13)CO(i-1) and (15)N(i) chemical shifts. The CA N COCA experiment establishes the correlation (13)Ca(i) and (15)CO(i) to (13)C alpha(i-1) and (15)N(i-1) within a single experiment by simultaneous encoding of the (13)C alpha(i) and (15)N(i) chemical shifts. This experiment establishes sequential amino acid correlations in close analogy to the solution state HNCA experiment. Reduced dimensionality 2D experiments are a practical alternative to recording multiple 3D data sets for the purpose of obtaining sequence-specific resonance assignments of peptides and proteins in the solid state.

Amino Acids↗
PubMed2001

U.S. Chemical program: purpose, challenges, and evolution.

This article explores long-term issues and problems that have seriously undermined the U.S. Chemical Testing Program established by the Environmental Protection Agency (EPA) under the Toxic Substances Control Act. This program is meant to gather information needed to protect human health and the environment from damaging exposure to toxic chemicals. Despite seemingly broad and impressive authority under the statute, there are a number of inherent difficulties, as well as substantial political constraints, that impede comprehensive oversight of chemicals in U.S. commerce. The article discusses several approaches that EPA has adopted to overcome statutory and political limitations and increase chemical testing information. The most recent and promising of these efforts has involved international negotiations to harmonize testing approaches with OECD nations and to cooperate on an agenda that will better share the testing burden on an international level.

Journal Article↗
PubMed2003

Fluorometric determination of chemically available lysine: adaptation, validation and application to different milk products.

A spectrophotometric method based on the reaction between available lysine and ortho-phthaldialdehyde (OPA) was adapted and validated for fluorometric determination of the chemically available lysine contents in milk matrices (UHT and conventional in-bottle sterilized cow milk, milk-based infant formulas and infant formula ingredients). The values of the analytical parameters show its usefulness as a routine method (linearity, r = 0.9992; detection limit, 0.0066 mg/mL assay; accuracy, 99-108%; precision, intra-day 2.1-5.9% and inter-day 3.5 10.2%). No statistically significant differences (p < 0.05) were found between the values obtained with the adapted method and those obtained applying the 1-fluoro-2,4-dinitrobenzene (FDNB) (Carpenter) technique. The OPA method was used to measure the chemically available lysine contents in UHT and sterilized milk marketed in Spain, to study the evolution of chemically available lysine during the shelf-life of UHT milks, and finally the quality of name- and store-brand UHT milks was also compared. No statistically significant differences (p < 0.05) were found between either the available lysine contents of the same type of UHT or sterilized milk or between store- and name-brand UHT milks. Statistically significant differences (p < 0.05) were found between the chemically available lysine contents in UHT and sterilized milk. Losses of chemically available lysine ranging from 2.7 to 29% were obtained during the shelf-life of UHT milk.

Animals↗
PubMed1990

What are antibiotics? Archaic functions for modern activities.

Secondary metabolites are proposed to have played important roles in the evolution of the reactions of living forms on earth, in effecting and modulating reactions during biochemical evolution by chemical and structural interaction with 'receptor' sites in primitive macromolecular templates. For example, in the evolution of the translation system, as the polymerizing reactions became more complex and proteins became involved, the low molecular-weight effectors were functionally replaced by polypeptides, but retained their ability to interact with receptor sites in nucleic acids and proteins. Many of these low molecular-weight effectors now play a different role, that of antagonists, by interacting with the original receptor sites in macromolecular structures; this explains their contemporary activity as antibiotics.

Animals↗
PubMed1997

Major "anastrophes" in the origin and early evolution of biological energy conversion.

The metabolism of living organisms has long been usefully divided into anabolism and catabolism. Anabolism is constructive, being concerned with the assembly of complex molecules, whereas catabolism is destructive in the sense that it involves the degradation of molecules. In addition to the well-known word catastrophe for sudden, drastic destruction and its consequences, it has been found practical to introduce in the evolutionary context the word "anastrophe" (an old greek word for turning back, in the opposite direction-from anastrephein, where ana = back and strephein = to turn) to cover sudden, drastic constructive events and their consequences. Mutations in genes and genomes giving selective advantage to an organism are typical anastrophic events. A single site mutation in a gene coding for a protein may be good, neutral or bad, or anastrophic, neutral or catastrophic, respectively, for the organism. The consequence of an anastrophic mutation may be a decisive first step on the long way to a new species, whereas a catastrophic mutation may lead to major cell damage or death. This example of the use of the anastrophe concept in biological evolution leads to the question about its applicability to other parts and paths of the cosmic evolutionary process, such as physical, chemical, social and cultural evolution. Here it will be mainly considered in connection with the energy conversion aspects of the chemical evolution leading to the origin of life and of the subsequent early biological evolution. More specifically, it will be attempted to describe possible major anastrophes in energy conversion both before and after the first occurrence of life on earth.

Animals↗
PubMed1995

Life on Mars? I. The chemical environment.

The origin of life at its abiotic evolutionary stage, requires a combination of constituents and environmental conditions that enable the synthesis of complex replicating macromolecules from simpler monomeric molecules. It is very likely that the early stages of this evolutionary process have been spontaneous, rapid and widespread on the surface of the primitive Earth, resulting in the formation of quite sophisticated living organisms within less than a billion years. To what extent did such conditions prevail on Mars? Two companion-papers (Life on Mars? I and II) will review and discuss the available information related to the chemical, physical and environmental conditions on Mars and assess it from the perspective of potential exobiological evolution.

Earth, Planet↗