F-actins are semi-flexible polyelectrolytes and can be assembled into large polymer-actin complex with polymorphism through electrostatic interaction with polycations. This study investigates the structural phase beha...F-actins are semi-flexible polyelectrolytes and can be assembled into large polymer-actin complex with polymorphism through electrostatic interaction with polycations. This study investigates the structural phase behavior and the growth of polymer-actin complexes in terms of its longitudinal and lateral sizes. Our results show that formation of polymer-actin complexes is cooperative, and morphology and growth of polymer-actin complexes depend on polycation species and concentrations of polycation and salt in a constant actin concentration. We found that the longitudinal growth and lateral growth of polymer-actin complexes are dominated by different factors. This induces the structural polymorphism of polymer-actin complexes. Major factors to influence the polymorphism of polymer-actin complexes in polyelectrolytc system have been discussed. Our results indicate that the semi-flexible polyelectrolyte nature of F-actins is important for controlling the morphology and growth ofactin architectures in cell.展开更多
The polymerization of actin has been studied with applying a new method of microcalorimetric measurement in vitro. The thermodynamic parameters of actin poly merization at 310.15K is reported. △Hm= 49.26kJ·mol-1...The polymerization of actin has been studied with applying a new method of microcalorimetric measurement in vitro. The thermodynamic parameters of actin poly merization at 310.15K is reported. △Hm= 49.26kJ·mol-1， △G=-25.62kJ·mol-1 and △S=241 .54J·K-1×mol-1. Thermogram showed that the thermokinetic process of actin polymerization had two different thermal effects where in the first exothermic step is con sidered to be the total results of several reations: metal ion (Mg2+, K+) binding to actin;the change of conformation of actin and hydrolysis of ATP in actin; and the second en dothermic step is assigned to the results of association and length adjustment (annealing process). Cisplatin, at lower concentration, affects the polymerization of G-actin reflected in the decrease of △Hm; and at higher concentration it induces the crosslinking and de polymerization of F-actin in the equilibrium system of G/F. The experimental results manifest that when the concentration of cisplatin is increased to a certain value, the sign of △Hm will be changed from positive to negative i. e. the magnitude and sign of △Hm of actin polymerization is dependent on the concentration of cisplatin. This is possibly related to the pharmacologic or toxicological action of cisplatin.展开更多
The number of papers about decavanadate has doubled in the past decade. In the present review, new insights into decavanadate biochemistry, cell biology, and antidiabetic and antitumor activities are described. Decame...The number of papers about decavanadate has doubled in the past decade. In the present review, new insights into decavanadate biochemistry, cell biology, and antidiabetic and antitumor activities are described. Decameric vanadate species (V10) clearly differs from monomeric vanadate (V1), and affects differently calcium pumps, and structure and function of myosin and actin. Only decavanadate inhibits calcium accumulation by calcium pump ATPase, and strongly inhibits actomyosin ATPase activity (IC50 = 1.4 μmol/L, V10), whereas no such ef- fects are detected with V1 up to 150 μmol/L; prevents actin polymerization (IC50 of 68 μmol/L, whereas no effects detected with up to 2 mmol/L V1); and interacts with actin in a way that induces cysteine oxidation and vanadate reduction to vanadyl. Moreover, in vivo decavanadate toxicity studies have revealed that acute exposure to polyoxovanadate induces different changes in antioxidant enzymes and oxidative stress parameters, in comparison with vanadate. In vitro studies have clearly demonstrated that mitochondrial oxygen consumption is strongly affected by decavanadate (IC50, 0.1 μmol/L); perhaps the most relevant biological effect. Finally, decavanadate (100 μmol/L) increases rat adipocyte glucose accumulation more potently than several vanadium complexes. Preliminary studies sug- gest that decavanadate does not have similar effects in human adipocytes. Although decavanadate can be a useful biochemical tool, further studies must be carried out before it can be conf irmed that decavanadate and its complexes can be used as anticancer or antidiabetic agents.展开更多
基金This research is financially supported by SORST, JST and the Ministry of Education, Science, Sports, and Culture, Japan (Grant-in-Aid of Creative Scientific Research).
文摘F-actins are semi-flexible polyelectrolytes and can be assembled into large polymer-actin complex with polymorphism through electrostatic interaction with polycations. This study investigates the structural phase behavior and the growth of polymer-actin complexes in terms of its longitudinal and lateral sizes. Our results show that formation of polymer-actin complexes is cooperative, and morphology and growth of polymer-actin complexes depend on polycation species and concentrations of polycation and salt in a constant actin concentration. We found that the longitudinal growth and lateral growth of polymer-actin complexes are dominated by different factors. This induces the structural polymorphism of polymer-actin complexes. Major factors to influence the polymorphism of polymer-actin complexes in polyelectrolytc system have been discussed. Our results indicate that the semi-flexible polyelectrolyte nature of F-actins is important for controlling the morphology and growth ofactin architectures in cell.
文摘The polymerization of actin has been studied with applying a new method of microcalorimetric measurement in vitro. The thermodynamic parameters of actin poly merization at 310.15K is reported. △Hm= 49.26kJ·mol-1， △G=-25.62kJ·mol-1 and △S=241 .54J·K-1×mol-1. Thermogram showed that the thermokinetic process of actin polymerization had two different thermal effects where in the first exothermic step is con sidered to be the total results of several reations: metal ion (Mg2+, K+) binding to actin;the change of conformation of actin and hydrolysis of ATP in actin; and the second en dothermic step is assigned to the results of association and length adjustment (annealing process). Cisplatin, at lower concentration, affects the polymerization of G-actin reflected in the decrease of △Hm; and at higher concentration it induces the crosslinking and de polymerization of F-actin in the equilibrium system of G/F. The experimental results manifest that when the concentration of cisplatin is increased to a certain value, the sign of △Hm will be changed from positive to negative i. e. the magnitude and sign of △Hm of actin polymerization is dependent on the concentration of cisplatin. This is possibly related to the pharmacologic or toxicological action of cisplatin.
文摘The number of papers about decavanadate has doubled in the past decade. In the present review, new insights into decavanadate biochemistry, cell biology, and antidiabetic and antitumor activities are described. Decameric vanadate species (V10) clearly differs from monomeric vanadate (V1), and affects differently calcium pumps, and structure and function of myosin and actin. Only decavanadate inhibits calcium accumulation by calcium pump ATPase, and strongly inhibits actomyosin ATPase activity (IC50 = 1.4 μmol/L, V10), whereas no such ef- fects are detected with V1 up to 150 μmol/L; prevents actin polymerization (IC50 of 68 μmol/L, whereas no effects detected with up to 2 mmol/L V1); and interacts with actin in a way that induces cysteine oxidation and vanadate reduction to vanadyl. Moreover, in vivo decavanadate toxicity studies have revealed that acute exposure to polyoxovanadate induces different changes in antioxidant enzymes and oxidative stress parameters, in comparison with vanadate. In vitro studies have clearly demonstrated that mitochondrial oxygen consumption is strongly affected by decavanadate (IC50, 0.1 μmol/L); perhaps the most relevant biological effect. Finally, decavanadate (100 μmol/L) increases rat adipocyte glucose accumulation more potently than several vanadium complexes. Preliminary studies sug- gest that decavanadate does not have similar effects in human adipocytes. Although decavanadate can be a useful biochemical tool, further studies must be carried out before it can be conf irmed that decavanadate and its complexes can be used as anticancer or antidiabetic agents.
