The osmotic coefficients of the sodium form of some biopolymers

The osmotic coefficients phi p,Na of dilute solutions of the sodium form of some weakly acidic polymers are theoretically predicted in this work. Based on the measured value 0.73 of gamma Na, the activity coefficient of free Na+, of the completely ionized humic acid (sodium salt) in a salt-free solution, the effective interligand distance b is calculated to be 11.34 A by using Manning's counterion condensation theory [Manning, G. S. (1969) J. Chem. Phys. 51(3), 924]. The corresponding values of gamma Na (measured experimentally) and b for the completely ionized exopolymer of Pseudomonas atlantica are 0.624 and 7.57 A when cultivated at a dilution rate D = 0.015 h-1, 0.647 and 8.19 A at D = 0.025 h-1, and 0.613 and 7.29 Aat D = 0.06 h-1. For alginic acid (in the completely ionized sodium form), gamma Na = 0.40 and b = 4.71 A. The osmotic coefficients phi p,Na for the partially and the completely ionized polymers are then predicted with Manning's theory as well.     

Letter to the editor: Electron diffraction for hydrated crystalline biopolymers: nigeran.

A method is presented to record electron diffraction diagrams on hydrated crystalline biopolymers. It involves quick-freezing of the hydrated crystals, which are maintained at a low temperature throughout the experiment. The technique is illustrated with lamellar single crystals of the linear polysaccharide nigeran. Water of hydration is shown to be in a sheet-like array and its removal is accompanied by development of lateral cracks. This morphological shrinkage coincides with an observed shortening of the b lattice parameter, which is normal to the lateral cracks.     

Piezoelectricity of biopolymers

The piezoelectricity of semicrystalline biopolymers was first discovered for wood and bone in the 1950's. Piezoelectric properties have since been investigated for a number of biological substances, including polysaccharides, proteins and deoxyribonucleates. The shear piezoelectric constants −d₁₄ = d₂₅ were determined for their oriented structures with a uniaxial symmetry D_∞. From studies of synthetic polypeptides and optically active polymers, it was concluded that the origin of piezoelectricity lies in the internal rotation of dipoles such as CONH. Values of d₁₄ = −10 pC/N were determined for highly elongated films of poly-L-lactic acid, optically active and biodegradable. The implantation of this polymer induced the growth of bone, possibly because ionic current caused by piezoelectric polarization stimulated the activity of bone cells. Submicron-thick polyurea films were prepared by evaporating diisocyanate and diamine monomers in vacuum. After poling, the films exhibited pyro and piezoelectric effects. The tensile piezoelectric constant d₃₁ = 10 pC/N persisting up to 200 °C was also observed for aliphatic polyurea films. kw     

On some features of historical morphogenesis

The results of the analysis of the diversity dynamics and phylogenetic schemes of various taxa (from species up to classes) show that taxa of different ranks evolved as separate integral natural systems. The main trends in the diversity dynamics of classes and orders are quite different from those of genera and families. The diversity dynamics of genera and families reflect the adaptive essence of these taxonomic categories in the evolution. About five short episodes of mass appearances of genera and families took place in the Phanerozoic. The taxonomic categories of classes and orders are characterized by the archetypes of these groups, and their diversity decreased in the evolution. The appearance of these taxa is not connected with the mass extinctions and changes in the abiotic environment.     

Abiotic origin of biopolymers

A variety of methods have been investigated in different laboratories for the polymerization of amino acids and nucleotides under abiotic conditions. They include (1) thermal polymerization, (2), direct polymerization of certain amino acid nitriles, amides or esters, (3) polymerization using polyphosphate esters, (4) polymerization under aqueous or drying conditions at moderate temperatures using a variety of simple catalysts or condensing agents like cyanamide, dicyandiamide, imidazole, etc., and (5) polymerization under similar mild conditions but employing activated monomers or abiotically synthesized high energy compounds such as adenosine 5-triphosphate (ATP). The role and significance of these methods for the synthesis of oligopeptides and oligonucleotides under possible primitive Earth conditions is evaluated. It is concluded that the latter more recent approach involving chemical processes similar to those used by contemporary living organisms, appears to offer a reasonable solution to the prebiotic synthesis of these biopolymers.Given at the International Seminar Origin of Life, 2–7, August 1974, Moscow, U.S.S.R.     

Conformation characteristics of biopolymers

The 25 year efforts, concerning the problem of conformational peculiarities of nucleic acids and structure-dynamic properties of globular proteins, studied at the Laboratory of Isotopic Methods of the Institute of Molecular Biology of the USSR Academy of Sciences are reviewed.     

Differential colorimetric analysis of some deoxyribosyl compounds

Simple procedures are described for the estimation of purine deoxyribonucleosides and deoxyribonucleotides. The nucleosides are hydrolytically cleaved at pH 2 and oxidized by periodate at room temperature. Under such conditions, the nucleotides are not oxidized, but they may be hydrolyzed and oxidized by periodate at 70 °. In each instance, the resulting malonaldehyde is estimated colorimetrically with thiobarbituric acid. Aqueous solutions containing free deoxyribose, free deoxyribose 5-phosphate, purine deoxyribonucleosides, and purine deoxyribonucleotides may be assayed for each deoxyribosyl species.     

Mechanical features of various silkworm crystalline considering hydration effect via molecular dynamics simulations

Silk materials are receiving significant attention as base materials for various functional nanomaterials and nanodevices, due to its exceptionally high mechanical properties, biocompatibility, and degradable characteristics. Although crystalline silk regions are composed of various repetitive motifs with differing amino acid sequences, how the effect of humidity works differently on each of the motifs and their structural characteristics remains unclear. We report molecular dynamics (MD) simulations on various silkworm fibroins composed of major motifs (i.e. (GAGAGS)_n, (GAGAGA)_n, and (GAGAGY)_n) at varying degrees of hydration, and reveal how each major motifs of silk fibroins change at each degrees of hydration using MD simulations and their structural properties in mechanical perspective via steered molecular dynamics simulations. Our results explain what effects humidity can have on nanoscale materials and devices consisting of crystalline silk materials.