[Cellular calcium signals: nature, registration, and quantitative estimation]. / Kletochnye kal'tsievye signaly: priroda, registratsiia i kolichestvennaia otsenka.

Calcium ions play a central role in the regulation of cellular activity. Calcium influx across the plasma membrane occurs through ion channels (voltage- and receptor-operated channels). Two intracellular channels responsible for releasing Ca2+ from the internal stores are ryanodine and IP3 receptors. Two mechanisms for Ca2+ extrusion have been identified in the sarcolemma (Ca2+ pump and Na+/Ca2+ exchanger) and one in the sarcoplasmic membrane (Ca2+ pump). Hierarchical organization of intracellular calcium signalling is presented. It is considered of opening of the single channels or of groups channels to give quarks and sparks. The methods for the determination of the intracellular Ca2+ concentration are discussed. The equation connecting [Ca2+]i with double wavelengths parameter R was obtained proceeding from three fluorescent forms of indo-1 (L, LM and LP). Using this equation permits improving calculation of [Ca2+]i.

[Protein motors: structure and generation of mechanical force]. / Belkovye motory: struktura i generatsiia mekhanicheskoi sily.

Recent data about the structural and functional features of protein motors (myosin, dynein, kinesin) are presented. The mechanism by which the chemical energy of ATP is transduced into mechanical work is discussed.

[Structural characteristics and aggregation of myosin heads in skeletal muscles]. / Strukturnye osobennosti i agregatsiia golovok miozina skeletnykh myshts.

Native conformational modifications of rabbit skeletal muscle myosin and its subfragment-1 (S-1) within the temperature range of 0-40 degrees C and irreversible unfolding of these proteins structure at temperatures 40-70 degrees C have been studied by the fluorescence and light scattering methods. The results obtained permit stating that myosin and its active subfragments form associates at the concentrations above 0.3 microM. Hydrophobic interactions between definite sites of S-1 are likely to be primarily responsible for the association. The complex profile of S-1 melting curve at high ionic strength indicates the existence of three structural domains in the heavy chain of the myosin head.

[Fluorescent studies on conformational states of human plasminogen. I. pH effect]. / Fluorestsentnoe issledovanie konformatsionnykh sostoianii plazminogena cheloveka. I. Effekt pH.

Conformational transitions of human plasminogen were studied by the fluorescent analysis according to the shift of the fluorescence spectrum maximum and the fluorescence dynamic quenching method. At pH 9.0-6.0 plasminogen has a stable native conformation, with a decrease of pH from 6.0 down to 5.3 the fluorescence spectrum maximum moves towards the short-wave region and with the subsequent lowering of pH--to the long-wave region. A share of the available protein tryptophanyls to quenchers KI and acrylamide in the neutral and weak-acid media is determined. The analysis of the data obtained permits considering that the plasminogen molecule at pH 5,3 is of a more compact structure than at pH 7.0; at pH 2.0 it loosens preserving the compact packing.

[Muscular myosin structural and functional changes during interaction with ATP and bivalent ions]. / Strukturnye i funktsional'nye izmeneniia miozina myshts pri vzaimodeistvii s ATP i dvukhvalentnymi ionami.

The interaction of myosin with ATP and bivalent ions is shown to cause changes in myosin ultraviolet fluorescence. Such a change is more significant for myosin of skeletal muscles than for that of smooth muscles. Kinetics of the fluorescence change has a phase of a sharp rise immediately after ATP addition and a phase of a slow decrease of fluorescence. The changes in fluorescence are connected with formation of an intermediate complex of myosin with ATP (intermediate). It is established that calcium ions are specific in the myosin ATPase reaction and they accelerate considerably the decay of this complex, while magnesium ions inhibits this process.

[Effect of intramolecular and intermolecular reactions of the intensity of histone H2A and H4 fluorescence]. / Vliianie vnutrimolekuliarnykh i mezhmolekuliarnykh vzaimodeistvii na intensivnost' fluorestsentsii gistonov H2A i H4.

Fluorescence of histones H2A and H4 of homo- and hetero-complexes has been studied. It has been found that in the composition of small aggregates consisting of several molecules, the change of histone fluorescence intensity is caused by the change of their tertiary structure. In the composition of large aggregates, including several dozens of molecules, the intramolecular interactions contribute to the change of histone fluorescence. The intermolecular histone interactions are specific and have a cooperative character.

[Temperature effect on the conformation state of fibrinogen and its derivatives]. / Bliianie temperatury na konformatsionnoe sostoianie fibrinogena i ego proizvodnykh.

The temperature dependence of spectral parameter B for fibrinogen, monomer fibrin, D and E fragments is examined by the method of ultraviolet fluorescence. Besides denaturation transition I (49 degrees C), conformational transition II (11-16 degrees C, depending on the sample) is observed in fibrinogen and its D fragment when temperature changes from 2 to 56 degrees C. Temperature transition II is reversible, sensitive to the ionic strength (its rise causes the transition temperature drop). Transition temperature of D fragment always correlates with that of fibrinogen, from which the fragment is obtained. Similarity in complex dependence of the B value on temperature for D fragment and fibrinogen is an additional proof of their structural likeness. No structural transitions are observed with a temperature rise up to 56 degrees C in E fragment. The ability of fibrinogen to inhibit self-assemblage of fibrin changes in the studied temperature intervals. A sharp transition from the acceleratory to inhibitory effect of fibrinogen on fibrin self-assemblage is registered at a temperature of about 11 degrees C. This change might be connected with structural transition II.

[Structure and aggregation of histones. I. Influence of the ionic composition of the medium on the structure and effectiveness of the intermolecular relationships of histone F2a (H2A+H4)]. / Issledovanie struktury i agregatsii gistonov. I. Vliianie ionnogo sostava na strukturu i éffektivnost' mezhmolekuliarnykh vzaimodeistvii gistona F2a(H2A+H4).

The investigation of fluorescence and light-scattering change of histone F2a, ribonuclease, tyrosine, N-acetyltirosinamide, methyl ether tyrosine by the concentration increasing of NaCl, MgCl2, Na2SO4 in the surrounding medium was carried out. In the case of used salts the changes of tertiary structure and histones aggregations depend on the anion type, which is presented in the environment. The tertiary structure of histones formed in the presence of salt is stabilized by weak (hydrophobic and hydrogenic) interactions.

[ATPase activity and fluorescence of myometrial actomyosin in experimental uterine inertia]. / ATF-azna aktyvnist' ta fluorestsentsiia aktomiozinu miometriia za aksperymental'noï slabkosti polohovoï diial'nosti

A comparative study was performed for actomyosin complexes of the female rabbit myometrium in the state of labour (actomyosin of the control) and secondary uterine inertia (actomyosin of the model). Under the secondary uterine inertia the activity of actomyosin Ca2+- and Mg2+-ATPase decreases. When pH of the medium changes, ATPase of control actomyosin has two peaks of the activity: at rH 6.0 and pH 9.0, that of the model at pH 6.0. Actomyosin of the model and control differs by a degree and rate of superprecipitation, thermal stability and structure. It is supposed that the structural changes in actomyosin under the secondary uterine inertia occur due to accumulation of the metabolism products, the level of which with this pathology is beyond the limits of the adaptation potentialities of the organism.

[Aggregation of histone F2b inthe presence of salt and methanol]. / Osobennosti agregatsii gistona F2b v prisutstvii soli i metanola

The kinetics of histone F2b aggregation in the presenceof NaCl and methanole was investigated. The size of aggregates increases during 20 hours, and in the following 13 hours the size of formed complexes does not change. It was shown that the stable colloid system was formed by the olygomers of histone F2b.

[Fibrinogen and fibrin monomer conformation changes dependent of pH magnitude]. / Konformatsionnoe izmeneniia fibrinogena i monomernogo fibrina, zavisimye ot velichiny pH

Conformational states of fibrinogen and fibrin monomer were studied by methods of differential and solvent-perturbation spectrophotometry and ultraviolet fluorescence at about neutral pH (6.5) and in the region of lower pH, 3.2 to 4.0. To prevent repolymerization of fibrin monomer at pH 6.5, urea was added in a non-denaturing concentration of 1.7 M. In the acid region specified, the immediate environment of tyrosine and tryptophan residues was found to be more polar and the accessibility to perturbants higher than at pH 6.5. Much more drastic changes of the same type occurred at pH less than 3 when denaturation of the protein takes place. The conformation of fibrinogen altered progressively upon lowering pH from 4.0 to 3.2. This acidity increase, practically, did not influence the conformation of fibrin monomer. Thus the tolerance of the latter to the appearance of the new positively changed groups seems to be comparably high. The bulk of the conformational changes subsequent upon neutralization of an acid fibrin monomer solution proceeds at a higher rate than the activation transition, i.e. the acquirement of a state of polymerization readiness by fibrin monomer molecules.

[Physico-chemical properties of uterine smooth muscle actomyosin]. / Fiziko-khimicheskie svoistva aktomiozina gladkoi myshtsy matki

The actomyosin complex of human myometrium has a low Ca-activated ATPase activity (0.007-0.012 mu mole H+ per 1 mg protein for 1 min), small degree and rate of superprecipitation. Transition to the state of pregnancy is accompanied by considerable changes in the physicochemical properties of the myometrium actomyosin. ATPase activity is 5-10 times as high and the rate of superprecipitation rises, particularly after the increase in the calcium concentration. The content of nucleic acid in the actomyosin complex decreases and D280/D260=1.1. The intensity of the actomyosin fluorescence at the pregnant state is more than twice as high.

[Change in conformation of histones F 2a and F 2b in solutions of different ionic strength]. / Zmina konformatsii histoniv F2a Ta F2b v rozchynakh iz riznoiu ionnoiu shloiu

A change was studied in the differential absorption spectra and fluorescence quantum yield of histones F2a and F2b with the ionic strength varies. It is shown that the structure of the histone F2a molecule stops changing with an increase in the concentration of NaCl up to 0.5 M. In the histone F2b molecule the conformational changes occur with the NaCl concentration less than 1.0 M. The conformation change results in formation of hydrophobic areas on the histone surface, which intensifies the histone-histone interaction. The role of the histone conformational changes for regulation of gene activity is discussed.