Adsorption of polypeptides on the solid surface. II. Effect of secondary chain structure and helix–coil transition

The theory of adsorption of semistiff chains on a planar surface developed by the authors previously has been used to consider the helix–coil transition in single-stranded macromolecule interacting with an adsorbent plane. The cases of nonselective interaction when the adsorption energy is independent of the unit conformation (a) and selective interaction with only helical (b) or coiled (c) sequences active in adsorption were investigated. In case (b) the existence of secondary structure favors chain bonding to the surface. This leads to the increase in the stability of the helical state and complete polypeptide chain spiralization. The profile of the conformational helix–coil transition acquires an asymmetrical shape inherent to the second-order phase transition. In case (c) the bonding of a partially helical chain to the surface is similar to the adsorption of Gaussian coils and is accompanied by the destruction of secondary structure, this destruction being appreciable even if the helical state in space was favorable.     

The oxygen effect in E. coli cells. Role of the photoreactivated component in modifying the oxygen effect in E. coli WP2 uvrA6 cells

A study was made of a contribution of photoreactivated lesions to the oxygen effect (OE) manifestation in cells of UV-sensitive E. coli WP2 uvrA6. It was shown that the contribution of the photoreactivated lesions depends upon radiation energy and gas conditions in which radiation is delivered. The OE value in the uvrA6-mutant may be modified in the irradiation conditions preventing induction of the photoreactivated lesions (gamma-irradiation in the presence of nigrosine, and X-irradiation).     

The electronic structure and radiorprotective activity of a series of substituted iminodihydrofurans]

Compounds that increase the survival rate of lethally exposed hybrid (CBA x C57B1/6)F1 mice have been revealed within the series of iminodihydrofurans. The quantum-chemical estimates, made by the MNDO method, show that substances which are capable of donor-acceptance interaction with DNA nucleotides and have the energy of donor orbitals, comparable with the electron structure of nucleotides, possess radioprotective efficacy.     

Adsorption of the polypeptides on a solid surface. III. Behavior of stiff chains in a pore

A strict analytical theory has been developed describing the behavior of a model lattice polymer chain of arbitrary stiffness in a slitlike pore at polymer–adsorbent interaction energies –ε. The thermodynamic characteristics of the system were calculated. It was shown that the transition of the macromolecule from the solution volume inside a pore occurs by the first-order phase transition with evolution of latent heat of adsorption. The transition point –ε = –ε_c is determined by the chain stiffness and is independent of the pore width D. It is shown that in the precritical range, –ε < –ε_c, the free energy ΔF of the macromolecules in the pores is adequately described by the universal dependence ΔF = ΔF(D*/A), where D* is some effective pore width depending on the value of –ε, and A is the length of the Kuhn segment. At high attraction energies, –ε ? –ε_c, the macromolecules are bonded to the pore walls by a great number of units and their free energy depends only on –ε and the chain stiffness, ΔF = ΔF(A, ε). Close to the critical energy –ε ? –ε_c (transition range), ΔF is determined by both the stiffness of the macromolecule and the pore width D: ΔF ～ A²D^?1 for fairly high values of A and D. The possibilities of using porous media as protein stabilizers are discussed, and the value of the stabilizing effect depending on the chain stiffness is estimated.     

Recombinogenic Telomeres in Diploid Sorex granarius (Soricidae,Eulipotyphla) Fibroblast Cells

The telomere structure in the Iberian shrew Sorex granarius is characterized by unique, striking features, with short arms of acrocentric chromosomes carrying extremely long telomeres (up to 300 kb) with interspersed ribosomal DNA (rDNA) repeat blocks. In this work, we investigated the telomere physiology of S. granarius fibroblast cells and found that telomere repeats are transcribed on both strands and that there is no telomere-dependent senescence mechanism. Although telomerase activity is detectable throughout cell culture and appears to act on both short and long telomeres, we also discovered that signatures of a recombinogenic activity are omnipresent, including telomere-sister chromatid exchanges, formation of alternative lengthening of telomeres (ALT)-associated PML-like bodies, production of telomere circles, and a high frequency of telomeres carrying marks of a DNA damage response. Our results suggest that recombination participates in the maintenance of the very long telomeres in normal S. granarius fibroblasts. We discuss the possible interplay between the interspersed telomere and rDNA repeats in the stabilization of the very long telomeres in this organism.     

The viroimmunotest for mass determinations of nanogram amounts of antigens

Simple highly sensitive screening variant of viral immunoassay for detection of nanogram quantity of antigen is proposed. The antigen linked with antibodies adsorbed on polystyrene 96-well plates was revealed by conjugate of Fab' fragments of antibodies with phage phi X174. The concentration of the antigen could be detected qualitatively and quantitatively (from 0.3 ng/ml to 1000 ng/ml).