Biomedical subjects

Xiang Yan

Publications and source records attributed to Xiang Yan.

21 records · Page 2Linked to original sources

PubMed2002

Metallomicellar catalysis: catalytic cleavage of p-nitrophenyl picolinate by Cu2+ complex of 4-chloride-2,6-bis(N-hydroxyethylaminomethyl)-benzophenol in micellar solution.

The hydrolysis of p-nitrophenyl picolinate (PNPP) catalyzed by the Cu(II) complex of 4-chloride-2,6-bis(N-hydroxyethylaminomethyl)-benzophenol was investigated kinetically by observing the rates of release of p-nitrophenol in the presence of three surfactants, which are hexadecyltrimethylammonium bromide, n-lauroylsarcosine sodium, and polyoxyethylene23 lauryl ether, at different pH and 25 degrees C. The scheme for the reaction involving a ternary complex comprising ligand, metal ion, and substrate in a micelle was established, and the relative kinetic and thermodynamic parameters were determined, including first-order rate constant (kN), association constant (Ks) for ternary complex, and pKa for the hydroxide ion of the ternary complex. The reaction mechanism was discussed.

Journal Article↗

PubMed2001

Metallomicellar Catalysis Cleavage of p-Nitrophenyl Picolinate Catalyzed by Binuclear Metal Complexes Coordinating Tripeptide in CTAB Micellar Solution.

The catalytic hydrolysis of p-nitrophenyl picolinate (PNPP) by Cu(II) and Zn(II) complexes coordinating tripeptide were studied kinetically by observing the rates of release of p-nitrophenol in the buffered micellar solution at 25 degrees C and different pH values. The experimental results indicate that 1 : 2 ligand : metal ion complexes in CTAB micellar solution are the active species in the reaction, and the complexes, especially that with Cu(II), efficiently catalyze the hydrolysis of PNPP. As a result, a kinetic model of binuclear metal complex catalysis involving a ternary complex in CTAB micellar solution is proposed to analyze the kinetic behavior of catalysis, and thus, relative kinetic and thermodynamic parameters are obtained. The results predict that the catalytic reaction by metallomicelle with binuclear complex involves a bifunctional mechanism. Copyright 2001 Academic Press.

Journal Article↗

PubMedDate not supplied

Rosiglitazone combined with insulin preserves islet beta cell function in adult-onset latent autoimmune diabetes (LADA).

BACKGROUND: LADA is thought to result from the chronic autoimmune destruction of the insulin-producing pancreatic beta cells. In addition to antidiabetic effects, the newly developed insulin sensitizer-thiazolidinediones have the potential to increase the insulin content of islet cells by downregulating local inflammation and autoimmune response. Therefore, we hypothesized that LADA patients might benefit from thiazolidinediones treatment. METHODS: LADA patients, with a fasting C-peptide (FCP) of 0.3 nmol/L or more, were enrolled and randomly assigned to receive subcutaneous insulin alone (insulin group, n = 12) or rosiglitazone plus insulin (insulin + RSG group, n = 11) to compare the impacts on islet beta cell function. Plasma glucose, HbA 1c, fasting C-peptide (FCP) and C-peptide after 2 h 75-g glucose load (PCP) were determined every 6 months. GAD-Ab and C-peptide were measured with radioimmune assays. Islet beta cell function was evaluated by PCP and DeltaCP(DeltaCP = PCP-FCP). RESULTS: All of the 23 patients have been followed up for 6 months, 17 cases for 12 months and 14 for 18 months. (1) During 6 months' follow-up, there were no significant changes for DeltaCP and PCP levels in both groups. (2) PCP and DeltaCP levels in insulin + RSG group patients stayed steady during the 12 months' observation (P = 0.161 for both PCP and DeltaCP), while in the insulin alone group, both FCP (P = 0.021) and PCP (P = 0.028) levels decreased significantly. Furthermore, PCP (P = 0.004) and DeltaCP(P = 0.015) differences between 12th month and baseline were higher in insulin + RSG group than those in the insulin group. (3) When observed up to 18 months, PCP and DeltaCP levels in insulin + RSG group patients still stayed steady, while PCP and DeltaCP levels decreased more in the insulin alone group. CONCLUSIONS: This pilot study suggests that rosiglitazone combined with insulin may preserve islet beta cell function in LADA patients.

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