查找使用阿拉丁产品的科研文献

Determination of Thrombin Activity by Reversed-phase High Performance Liquid Chromatography

Zhang Liang,Yang Dehui,Liu Ye

Background: A reversed-phase high-performance liquid chromatographic method for determining thrombin activity is described. The improved method can provide a high resolution between substrate Nα-P-toluenesulfonyl-L-arginine methyl ester (TAME) and the product of enzyme reaction, Nα-P-toluenesulfonyl-L-Arginine (TA). Methods: When the substrate concentration was 5 mg/mL, the Michaelis equation approached the zero-order reaction, and the thrombin enzyme activity must have a good linear relationship with the consumption of TAME or the yield of TA. Results: The method is suitable for quantitatively analyzing thrombin activity in formulation or serum. Conclusion: Three batches of thrombin lyophilized preparations were determined for activity.

Thermal Diffusivity of 2-Ethoxy-2-methylpropane (ETBE) and 2-Methoxy-2-methylbutane (TAME) at Temperatures from (293 to 523) K and Pressure up to 10 MPa

Ying Zhang,Xiong Zheng,Yutian Chen,Maogang He

The thermal diffusivities of 2-ethoxy-2-methylpropane (ETBE) and 2-methoxy-2-methylbutane (TAME) (mass purity > 0.990, GC) were measured by the dynamic light scattering method. The investigated p–T regions are T = (293 to 523) K and p = (4 to 10) MPa, including saturated liquid, saturated vapor, and liquid. The expanded relative uncertainty in thermal diffusivity was estimated to be less than 2.4% over the whole investigated range. The influences of temperature and pressure on thermal diffusivity were presented. The empirical correlation of thermal diffusivities for both saturated liquid/vapor and liquid were also proposed with absolute average relative deviations (AARDs) of 0.22 and 0.26% for saturated-liquid ETBE and TAME, 0.13 and 0.20% for saturated-vapor ETBE and TAME, and 0.23 and 0.69% for liquid ETBE and TAME, respectively.

Effects of acetazolamide on the conformations and activities of digestive enzymes: pepsin and trypsin

Liu Ting,Chen Xiaopeng,Xing Jinfeng,Ge Zhiqiang

The changes in activities and conformations of pepsin and trypsin induced by acetazolamide (ACZ) were studied with spectroscopic methods under their respective physiological pH conditions in vitro. The results showed that both the enzymes activities were obviously inhibited as increasing in acetazolamide concentration, while the inhibitory ratio of trypsin was higher than pepsin. The intrinsic fluorescence of the two enzymes was quenched by acetazolamide through static process. Acetazolamide bound trypsin in a more firmly way than pepsin. Thermodynamic analysis revealed that driving force of acetazolamide-pepsin was different from acetazolamide-trypsin. The electrostatic interaction had a significant effect on the binding process of acetazolamide-trypsin, whereas interaction of the acetazolamide-pepsin was driven by hydrogen bonding and van der Waals force. Circular dichroism spectroscopy and synchronous fluorescence showed acetazolamide induced conformational and microenvironmental changes of both the enzymes. These investigations suggested that acetazolamide at different physiological pH may have different effects on the conformations and functions of proteins through variant mechanisms. This study is helpful for understanding the changes in the function and structure of digestive enzymes influenced by acetazolamide in gastrointestinal tract in vivo.

Speed of sound measurement in ethyl tert-butyl ether and tert-amyl methyl ether by Brillouin light scattering

Xiong Zheng,Ying Zhang,Maogang He

Ethyl tert-butyl ether (ETBE) and tert-amyl methyl ether (TAME) have been considered as the potential fuel additives as the replacement of methyl tert-butyl ether (MTBE). Now it is necessary to supplement and perfect the thermophysical properties of oxygenates, including acoustic property. In this paper, speed of sound in ETBE and TAME were measured by Brillouin light scattering from 293.15 K to 680 K and from saturated vapor pressure to 10 MPa, including saturated liquid/vapor, compressed liquid and supercritical region. It is estimated that u ( T ) = 0.01 K under saturated condition; u ( T ) = 0.02 K, u ( p ) = 0.015 MPa for p  < 5.5 MPa, u ( p ) = 0.03 MPa for p  > 5.5 MPa under compressed liquid and supercritical conditions; and the relative expended uncertainty in the speed of sound is estimated to be less than 0.5% with coverage factor of k to be 2. Moreover, the reference relations of the speed of sound for saturated liquid, vapor and compressed state are presented for interpolation with the average absolute deviation of 0.23%, 0.07% and 0.33% for ETBE and 0.34%, 0.24% and 0.29% for TAME, respectively.

Protective effect of ovalbumin-flavonoid hydrogel on thrombolytic activity and stability of nattokinase

Yejun Zhong,Lei Yang,Ziyi Zhu,Hongyu Chen,Chengmei Liu,Taotao Dai,Er Sheng Gong

The protective effect of ovalbumin-flavonoids (naringenin, genistein, naringin, puerarin, and daidzein) hydrogels on the thrombolytic activity and stability of nattokinase were investigated. The results suggested that flavonoids promoted the gelation of ovalbumin solution, which was not able to form hydrogel at the same concentration upon heating. The nattokinase/ovalbumin-naringenin hydrogel had the strongest hardness and springiness. All nattokinase/ovalbumin-flavonoids hydrogels were more elastic than viscous. After in vitro digestion, the thrombolytic capacities of all nattokinase/ovalbumin-flavonoids hydrogels were significantly higher than that of free nattokinase. Moreover, nattokinase/ovalbumin-flavonoids hydrogels showed higher thermal and pH stability than free nattokinase. Fluorescence spectroscopy and molecular docking analysis revealed that the main interactions between nattokinase and daidzein, nattokinase and genistein were mainly hydrogen bond, while the main interactions between nattokinase and naringin, nattokinase and puerarin, nattokinase and naringenin were hydrophobic interaction. This research suggested that nattokinase/ovalbumin-flavonoids had great potential for applications in the treatment of thrombus.

A multicomponent propane monooxygenase catalyzes the initial degradation of methyl tert-butyl ether in Mycobacterium vaccae JOB5

Yiyang Chen,Hao Ren,Xiangyu Kong,Hao Wu,Zhenmei Lu