[Modelling of conformational transitions in macromolecules due to low-molecular binding agents].
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DNA↗
Biomedical subjects
T M Birshteĭn
Publications and source records attributed to T M Birshteĭn.
[Helix-globule transitions of polypeptides selectively reacting with the interface].
An analytical theory of helix-coil transitions for polypeptides in a solution near a flat and homogeneous interface is given. The following cases were considered: a) only the helical parts are absorbtively active; b) only the coiled sections of the chain are active in adsorption. It has been shown that the binding of the polymer chain to the surface is a result of a phase transition of a second order, moreover in case a) the presence of a secondary structure abruptly increases the ability of the macromolecules to bind to the interface. This largely increases the stability of the helical structure of the chain and leads to a practically complete spiralization of the macromolecule. The profile of the conformational transitions was strictly asymmetrical which is typical for the phase transitions. In case b) the process of binding resembles the adsorbtion of the Gaussian coils. In this case the rate of spiralization of the chain decreases in the course of binding and the degradation of the secondary structure is significant even if the helical state in volume is stable. The profile of the transition remains qualitatively similar to the helix-coil transition in volume but is displaced to the region of larger equilibrium constants.
Models, Chemical↗
[The effect of external restrictions on the stability of the globular state].
The delta Td changes of heat denaturation temperature for globule proteins were estimated, for a globule inserted into pores of a inert carrier, that limits the conformational set of the denatured chain. Based on calculations for a grated selfintercepted chain in a slit-like pore, with no interactions with the pore walls, functions of delta Td depending on the rigidity of the unfolded chain, its length and pore sizes were determined. For alpha-chymotrypsin in polyacrylamide gels the estimated delta Td was of several degrees. The possible influence of the pore form and intramolecular interactions for a denatured chain on the value of the stabilizing effect is discussed.
Drug Stability↗
[Studies on the coil-globule transition by the Monte-Carlo method].
The results of a dynamical Monte-Carlo study on the coil-globule and globule-coil transitions are presented. Self-avoiding chains of lengths N = 32 and 64 are investigated. The kinetic model included two- and three-bonds flips. The relaxation of the chain was induced by the abrupt change of the interaction between the monomers. The time evolution of the radius of gyration and the number of intramolecular contacts was obtained. It is established that the transition to the compact state occurs due to the contacts between the monomers close to each other along the chain. The results obtained are compared with the predictions of analytical theories.
Biopolymers↗
[Conformational transitions in adsorbed macromolecules with secondary structure].
An analytical theory is presented taking into account the effects of the flat adsorbing surface on the equilibrium properties of the long single-stranded macromolecule possessing a secondary structure. Change of the secondary structure is described in terms of Zimm--Bragg theory; adsorbtion properties are calculated for the lattice model without taking into account the 3-dimensional interactions. It is shown that the presence of the adsorbing surface sharpens helix-coil transition, displacing it towards the lower constants of equilibrium (s). A relation of the critical energy of adsorbtion (--epsilonkappa) on s is obtained at different values of the cooperativity factor sigma. This relationship represents a phase diagram of the system. Various sections of this phase diagram corresponding to different dependence of s and --epsilon on the external factors are considered. It is shown that the process of adsorbtion may occur in different manners: either cooperatively or by the phase transition of type II with jumps in one or in three points.
Kinetics↗