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Chanchai Sattayanon Nawee Kungwan Winita Punyodom Puttinan Meepowpan Siriporn Jungsuttiwong 《Journal of molecular modeling》2013,19(12):5377-5385
A theoretical investigation of the ring-opening polymerization (ROP) mechanism of ε-caprolactone (CL) with tin(II) alkoxide, Sn(OR)2 initiators (R?=?n-C4H9, i-C4H9, t-C4H9, n-C6H13, n-C8H17) was studied. The density functional theory at B3LYP level was used to perform the modeled reactions. A coordination-insertion mechanism was found to occur via two transition states. Starting with a coordination of CL onto tin center led to a nucleophilic addition of the carbonyl group of CL, followed by the exchange of alkoxide ligand. The CL ring opening was completed through classical acyl-oxygen bond cleavage. The reaction barrier heights of ε-caprolactone with different initiators were calculated using potential energy profiles. The reaction of ε-caprolactone with Sn(OR)2 having R?=?n-C4H9 has the least value of barrier height compared to other reactions. The rate constants for each reaction were calculated using the transition state theory with TheRATE program. The rate constants are in good agreement with available experimental data. 相似文献
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Jiraporn Suwan Boyangzi Li Puttinan Meepowpan Shaker A. Mousa Bhusana Premanode Robert J. Linhardt 《Carbohydrate research》2009,344(10):1190-37
The novel low-molecular-weight chitosan polysulfate (MW 5120-26,200 Da) was prepared using the depolymerization of chitosan with papain (EC. 3.4.22.2). The sulfonation of depolymerized products was performed using chlorosulfonic acid in N,N-dimethylformamide under semi-heterogeneous conditions. The structures of the products were characterized by FTIR, 13C NMR, and 1H NMR (1D, 2D NMR) spectroscopy. The present study sheds light on the mechanism of anticoagulant activity of chitosan polysulfate. Anticoagulant activity was investigated by an activated partial thromboplastin assay, a thrombin time assay, a prothrombin time assay, and thrombelastography. Surface plasmon resonance also provided valuable data for understanding the relationship between the molecular binding of sulfated chitosan to two important blood clotting regulators, antithrombin III and heparin cofactor II. These results show that the principal mechanism by which this chitosan polysulfate exhibits anticoagulant activity is mediated through heparin cofactor II and is dependent on polysaccharide molecular weight. 相似文献
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