Differential scanning calorimetry（ DSC） was used to measure the thermal hysteresis activity(THA) of plant antifreeze proteins(AFPs). The results reveal that DSC is a good method to screen and study AFPs. In the sixt...Differential scanning calorimetry（ DSC） was used to measure the thermal hysteresis activity(THA) of plant antifreeze proteins(AFPs). The results reveal that DSC is a good method to screen and study AFPs. In the sixteen components extracted from Ammopipanthus mongolicus leaves, one(P3S1) was found to have apparent thermal hysteresis activity by DSC. As the amount of ice nuclei in the sample decreased, the THA of P3S1 increased from 0.01℃ to 0.65℃ . It is notable that the two- peak thermal hysteresis effect was observed. Two endothermic peaks appeared in the melting process of P3S1, while the freezing peak also consisted of two peaks. The peaks appeared antecedently showed larger thermal effect. This phenomenon shows P3S1 has two different kinds of interaction with water and ice crystal. It is probably an important property of a class of AFPs.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 thermal properties of porcine brain tubulin polymerization and denaturation and the efftcts of taxol were studied from 4 ℃ to 115 ℃ with a new highly-sensitive differential scanming calorimeter (Micro DSC Ⅲ, Se...The thermal properties of porcine brain tubulin polymerization and denaturation and the efftcts of taxol were studied from 4 ℃ to 115 ℃ with a new highly-sensitive differential scanming calorimeter (Micro DSC Ⅲ, Setaram,France). The DSC results indicated that microtubule polymerization can proceed uia an endothermic process and that taxol could alter the process.A large aggregation peak was found at about 85 ℃ in the course of the denaturation and it disap pcared with adding taxol. The heat flow oscillation was observed during the controlled-temperature experiments and taxol could stabilize the structure of the microtubules so that the oscillation disappezred.展开更多
文摘Differential scanning calorimetry（ DSC） was used to measure the thermal hysteresis activity(THA) of plant antifreeze proteins(AFPs). The results reveal that DSC is a good method to screen and study AFPs. In the sixteen components extracted from Ammopipanthus mongolicus leaves, one(P3S1) was found to have apparent thermal hysteresis activity by DSC. As the amount of ice nuclei in the sample decreased, the THA of P3S1 increased from 0.01℃ to 0.65℃ . It is notable that the two- peak thermal hysteresis effect was observed. Two endothermic peaks appeared in the melting process of P3S1, while the freezing peak also consisted of two peaks. The peaks appeared antecedently showed larger thermal effect. This phenomenon shows P3S1 has two different kinds of interaction with water and ice crystal. It is probably an important property of a class of AFPs.
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 thermal properties of porcine brain tubulin polymerization and denaturation and the efftcts of taxol were studied from 4 ℃ to 115 ℃ with a new highly-sensitive differential scanming calorimeter (Micro DSC Ⅲ, Setaram,France). The DSC results indicated that microtubule polymerization can proceed uia an endothermic process and that taxol could alter the process.A large aggregation peak was found at about 85 ℃ in the course of the denaturation and it disap pcared with adding taxol. The heat flow oscillation was observed during the controlled-temperature experiments and taxol could stabilize the structure of the microtubules so that the oscillation disappezred.
