Microspheres proteinoid

Proteinoids are man-made condensation polymers produced by random or directed assembly of natural or synthetic amino acids or small peptide chains. Following the discovery, in the late 1950s, that linear condensation polymers of mixed natural amino acids could interact with water to form hollow microspheres, proteinoids have been the subject of extensiveinvestigations. 

The alkylcyanoacrylates are biodegradable polymers which have been used as tissue adhesives in surgery (Woodward et al, 1965) and have been 

Polybutylcyanoacrylate nanoparticles have also been investigated as potential antigen delivery systems. Particles with adsorbed ovalbumin and mean particles sues of 0.1 and 3//m were administered to rats by gastric intubation (O Hagan et al, 1989). Both groups of rats showed enhanced salivary IgA antibody responses in comparison to those shown by rats 

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The literature of metabolism in proteinoids and proteinoid microspheres is reviewed and criticized from a biochemical and experimental point of view. Closely related literature is also reviewed in order to understand the function of proteinoids and proteinoid microspheres. Proteinoids or proteinoid microspheres have many activities. Esterolysis, decarboxylation, animation, deamination, and oxido-reduction are catabolic enzyme activities. The formation of ATP, peptides or oligonucleotides is synthetic enzyme activities. Additional activities are hormonal and inhibitory. Selective formation of peptides is an activity of nucleoproteinoid microspheres these are a model for ribosomes. Mechanisms of peptide and oligonucleotide syntheses from amino acids and nucleotide triphosphate by proteinoid microspheres are tentatively proposed as an integrative consequence of reviewing the literature. 

Proteinoids, as a model of primitive abiotic proteins >, are formed by polymerization from protobiologically plausible micromolecules (amino acids) under presumed protobiological conditions. Proteinoids have enzyme-like activities and metabolic qualities. Proteinoid microspheres are the most suitable model for protocells since they do not consist of macromolecules extracted from contemporary organisms. 

A number of studies have been performed in the context of a theory that proteins and polynucleotides were formal in a suspension of proteinoid microspheres and the microspheres could then have evolved to contemporary cells. The experimental results and evolutionary considerations have been summarized in the textbook of Fox and Dose published in 1977 2). This review therefore deals with studies since 1977, although some description of literature before 1977 is reviewed as occasion demands. Since the evolutionary consideration of proteinoids and proteinoid micro-spheres has been discussed in much literature and many books, (e.g. 2, 3), the attention in this paper is focussed on the description of the biochemical and experimental parts of the literature. Inasmuch as protobiological activities of proteinoids in solution are carried into microspheres 2), experiments with proteinoids in solution are not excluded. 

In this context, the literature concerning closely relevant experiments and the understanding of mechanisms of metabolism in proteinoid microspheres are reviewed. 

The proteinoid microspheres (Fig. 1), as simulated protocells, form from virtually all of the known wide variety of thermal copolyamino acids 2). Microspheres are formed if the aqueous or aqueous salt solution of proteinoid is heated and the clear decanted solution is allowed to cool. This self-assembly may also be effected by chilling solutions saturated at room temperature. Sonication at room temperature can be used. 

When the pH of a suspension of microspheres of acidic proteinoid is raised by 1-2 units, diffusion of material from the interior to the exterior, fission into two particles, and the appearance of a double layer in the boundary are observed 2 Proteinoid microspheres shrink or swell on transfer to hypertonic or to hypotonic solutions respectively. Some experiments show that polysaccharides are retained under conditions in which monosaccharides diffuse out2. Some proteinoid microspheres possess the intrinsic capacity to grow by accretion, to proliferate through budding, and to form junctions 2). The morphology and other characteristics of proteinoid microspheres are altered by the inclusion of other materials such as polynucleotides, lipids or salts. 

Catabolic and Synthetic Enzyme Activities of Proteinoids and Proteinoid Microspheres... 

Esterolysis, decarboxylation, amination, deamination and oxidoreduction are catabolic enzyme activities of proteinoids and proteinoid microspheres. The formation... 

Proteinoid microspheres containing zinc hydrolyze the natural substrate, adenosine triphosphate (ATP) as well as the unnatural substrates, p-nitrophenylacetate or p-nitrophenyl phosphate. The significance resides in the fact that the energy for most biosyntheses is provided by the hydrolysis of ATP. Zinc, magnesium and other metal salts are known to catalyze the hydrolysis of ATP 10). Proteinoid microspheres containing zinc as a cofactor have an activity for hydrolysis of ATP 11 12). 

After the cooling of a hot solution of acidic proteinoid and zinc hydroxide, zinc-containing microspheres are deposited. The Zn-proteinoid microspheres washed with water retain the activity, but the wash liquids show successively less activity U). Attempts to introduce Zn into proteinoids in this manner gave highly erratic results until freshly prepared zinc hydroxide was used n). There have not been further experimental data published these experiments were mainly to attempt introducing zinc into proteinoid microspheres. 

Fig. 2. Chromatogram showing ATP produced in a suspension of proteinoid microspheres in an aqueous solution of ADP and inorganic phosphate Fox, Adachi, Stillwell13)...

The conversion occurs also in an aqueous suspension of proteinoid microspheres containing dopa in the polymer instead of tyrosine. Presumably, dopaquinone is formed from tyrosine or dopa within the proteinoid during illumination with the aid of ferrous chloride 13). These experiments were performed after studies of the conversion of ADP to ATP catalyzed by the quinone, chloranil, and ferrous ion in dimethyl-formamide solution with white light. The yield of ATP under these condition is 20% 13,14). 

The synthesis of peptide has been tested at pH 7.2 in a suspension of (acidic + basic) proteinoid microspheres. The activity of the complex particles is several times as large as that of the basic proteinoid solution alone 28). 

The syntheses of peptides are energized by ATP, they are operative in the presence of water, and the ATP is most effective in the peptide synthesis when supplied continuously. If the ATP is supplied in repeated small fractions, the conversion from amino acid to peptide in the reaction mixture with acidic and basic proteinoid microspheres is greater than if the same total amount is supplied at once, since the amino acid is present in considerable molar excess over ATP. The most likely explanation for the higher rate of conversion for repeated reaction of ATP is that it is more efficiently used, due to rapid decay of any one charge of ATP 28>,... 

It is remarkable that proteinoid microspheres bring the optimum pH for the amino acid activation from the acidic range to neutral. Acidic condition for the activation may be provided in the metal-proteinoid microspheres in neutral buffer. 

The mode of peptide synthesis by proteinoids or proteinoid microspheres has not so far been ascertained. We propose here possible ways to synthesize peptides from amino acid and ATP by proteinoids, as shown below. Since it is difficult to deduce mechanisms from the data reported, the following scheme is tentative. 

ATP is converted to dinucleotide in magnesium-containing buffer without proteinoid in a yield of 0.7 %, but in the presence of basic proteinoid solution, acidic proteinoid microspheres, or acidic-basic proteinoid microspheres, the conversion to oligonucleotides is 2.2-2.3 %. With AMP instead of ATP no oligonucleotides result. The proteinoids are thus a model for proto-RNA polymerase activity, and ATP is reaffirmed as the source of energy for the synthesis of phosphodiester linkages 47). The microspheres of acidic proteinoid or of acidic-basic proteinoid synthesize di- and trinucleotides, while without proteinoid or basic proteinoid solution dinucleotide only results. Furthermore, the ratios of trinucleotides/dinucleotide are 0.5 for acidic-basic proteinoid microspheres, 0.2 for acidic proteinoid microspheres 47). 

The catalytic, synthetic, hormonal, and inhibitory activities that have been found in proteinoids or proteinoid microspheres are listed in Table 2. The possibility that metabolic activities found were due to contamination by micro-organisms is denied by experiments under aseptic condition or by the several experimental observations. The activities of proteinoids are generally weak. In some cases, proteinoids act several orders of magnitude more slowly than do modern enzymes or organisms, but free amino acids or Leuchs polypeptides usually have no activity or less than the proteinoid composed of the same amino acids. In general, activities of proteinoids increase approximately in proportion to its molecular weight. One or more of the proteinoids has been found to meet the salient requirements of enzymes such as Michaelis-Menten kinetics, pH-activity curves, etc. 

Almost all fractions separated have the activity9 66. In some studies the activity of fractions separated by gel fdtration is increased up to about 20 times, but unidentified inhibitor may have been removed during the fractionation 9). The activity could be improved by the provision of a new active site and structure which could be formed from synthesized polypeptides in proteinoid microspheres. Mixed aminoacyl adenylates have been reacted with proteinoids to yield polymers of substantially increased size, and the modified proteinoids form microspheres 69). 

The inactivity of acidic proteinoid (A) synthesize peptides in solution of pH 7.2 is in contrast to the activity of the lysine-rich proteinoid (B), when A and B form microspheres. The activity of the complex is several times as large as that of lysine-rich proteinoid alone 28). Physical surface and interior providing suitable environment for dehydration may be responsible. It may also be that the closed molecules of both proteinoids may be opened by the interaction, consequently buried active sites of proteinoids become effective. Neutral amino acids contained in each proteinoid may prevent the entire neutralization of acidic and basic residues. In the synthetic pathways of peptides and oligonucleotides by proteinoid microspheres, proteinoid nucleotide complex is proposed in this article as a main intermediate of the reactions. Oligo-... 

Substantial enzymic and synthetic activities of proteinoid microspheres have been found, in spite of a requirement for a narrowed range of condition and materials for the experiments. These findings are evidence to support the evolutionary theory for proteinoid microspheres. 

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