[Changes in the parameters of equilibrium binding of acidic dyes by contractile proteins during their functional activity and heat denaturation]. / Izmeneniia parametrov ravnovesnogo sviazyvaniia kislotnykh krasitelei sokratitel'nymi belkami pri ikh funktsional'noi aktivnosti i pri teplovoi denaturatsii.

A study was made of the equilibrium distribution of acidic dyes (Heliogen blue, Bromthymol blue, Bromphenol blue, Phenol red) between actomyosin threads (intact, contracted by ATP, or denaturated by heating) and the medium. The limits of dye sorption (A infinity) were shown to rise with the increase in their hydrophobia. The heat denaturation is accompanied with similar changes in all the dyes examined: i.e. with the increase in the limits of dye sorption and constant dissociation, and with the decrease in dye affinity to protein. The functional activity of contractile proteins acted upon with ATP is accompanied with different changes. For Heliogen blue these are like those during denaturation, whereas for Phenol red these are quite opposite: the limits of dye sorption and constant dissociation diminish, and the affinity to protein rises. Thus, during the heat denaturation the number of polar and non-polar groups accessible to dyes increases, whereas during functional activity only the number of non-polar bonds increases, and the quantity of polar bonds is seen reduced.

[Ultrastructure of actomyosin filaments]. / Ul'trastrukturnye issledovaniia plenochnykh aktomiozinovykh nitei.

Investigation of the fine structure of actomyosin filaments indicates that mechanical pressing of protein film (during preparation of the filaments) results in parallel alignment of the filament along the longitudinal axis. Contraction by ATP results in a condensation of the filament system. Heat denaturation is accompanied by destruction of the filament system.

[Action of heavy water on actomyosin pellicular filaments]. / Deistvie tiazheloi vody na plenochnye niti aktomiozina.

Deuterium oxide (D2O) prolongates the contractile ability of actomyosin threads by 85%. The contraction of actomyosin threads decreases in the presence of D2O by 28%. D2O decreases neutral red sorption by actomyosin threads. The limiting dye sorption (A infinity) decreases by 45 and 31% within the ranges of weak and high concentrations, resp. Thus, deuterium oxide may affect the conformation of protein molecules.

[Sorption of neutral red by actomyosin threads during contraction and heating]. / Sorbtsiia neitral'nogo krasnogo nitiami aktomiozina pri sokrashchenii i nagreve.

Studies of the equilibrium distribution of the cation dye-neutral red by actomyosin threads allowed to establish the fact that different concentrations of dye reveal the existence of different bonds with contractile proteins. Firm bonds (7.3 ccal/M) are discovered at low dye concentrations, and weaker bonds (4.5 ccal/M) are seen at higher concentrations. The contraction of actomyosin threads evoked by ATP or heating is accompanied with similar changes, i. e. by the diminishing of the maximum dye sorption within the range of low dye concentrations and by the increase in the maximum dye sorption within the range of high concentrations.