Synthesis and catalytic kinetics of tellurium-modified hyaluronic acid with glutathione peroxidase activity

A novel mimic TeHA was synthesized by modifying hyaluronic acid (HA) with tellurium, whose function is similar to that of glutathione peroxidase (GPX). The structure of TeHA was characterized by means of infrared spectroscopy and nuclear magnetic resonance spectroscopy, showing that the target Te is located at -CH2OH of the N-acetyl-D-glucosamine of HA. The activity of TeHA is 163.6 U/mu mol according to Wilson's method. In contrast to other mimics, TeHA displays a high activity. Moreover, TeHA can use many hydroperoxides as substrates, such as H2O2, cumenyl hydroperoxide, and tert-butyl hydroperoxide, and cumenyl hydroperoxide is the optimal substrate. A ping-pong mechanism was deduced for the reduction reactions catalyzed by TeHA according to the steady-state kinetic studies.

Studies on the stability of polyazamacrocycle-Eu (Tb) by potentiometry and its catalytic hydrolysis on phosphate diester

The stability constants and species distributions of complexes of two lanthanide ions, Eu (III) and Tb(III), with a macrocyclic ligand, 3,6, 9, 17 20, 23-hexaazo-29, 30-dihydroxy-13, 27-dimethyl-tricylco-[23,3,1,1(11,15)] triaconta-1 (28) 11,13,15 (30), 25 26-hexane (BDBPH), in 1: 1 and 2: 1 system, were determined potentiometrically in 50% ethanol solution, at 35.0 degrees C and I = 0.100 mol/L (KCl). The two metal ions could form deprotonated mono- or dinuclear complexes with BDBPH with high stability after the three protons of the ligand completely neutralized. At higher pH values, Eu(M) could not form hydroxo complexes with BDBPH, while Tb(III) could form hydroxo complexes in the types of M2L(OH) M2L(OH)(2) and M2L (OH)(2). The kinetic study on the hydrolysis reaction of his (4-nitrophenyl) phosphate (BNPP) catalyzed by Tb-BDBPH system (2:1) was carried out in aqueous solution (pH 7.0 similar to 10.0) at 35 degrees C with I = 0.1000 mol/L (KCl). The second-order rate constant k(BNPP) (2.3 x 10(-3) (mol/L)(-1)center dot s(-1)) was determined. The dinuclear monohydroxo species, L-Tb-2-OH, is kinetically active species.

Enzymatic and kinetic properties of selenium-containing catalytic antibody with cGPX activity

Three selenium-containing catalytic antibodies mHB4, mHB5 and mHB7 which acted as mimics of cytosolic glutathione peroxidase(cGPX), were prepared by chemically introducing selenium into monoclonal antibodies HB4, HB5 and HB7. HB4. HB5 and HB7 were raised against a GSH derivative GSH-S-DNP dibenzyl ester, The cGPX activity of mHB4, mHB5, mHB7 were 170, 1 867, 32 U/mu mol, respectively. The cGPX activity of mHB5 was 0, 32 fold of natural rabbit liver cGPX and 1. 51 fold of m4A4. About two atoms of selenium existed in each of mHB5 molecule determined by inductively-coupled plasma/mass spectroscopy (ICP-MS), The optimal activity of mHB5 was at between pH 8. 4 and 8, 8, The reaction catalyzed by mHB5 involved a Ping-Pong mechanism. At pH 7. 0 and 37 degreesC, the apparent second-order rate constants for reaction of mHB5 with H2O2 and t-ROOH were as followed: k(+1) (H2O2) = 9. 71 x 10(6) L/(mol min), k(+1)(t-ROOH) = 5. 99 x 10(5) L/(mol.min). Rate accelerations (k(cat)/K-m/k(uncat)) 9. 8 x 10(6) and 3.7 x 10(5) fold those of the uncatalytic reaction were observed.

Synthesis of C-1 bridge-containing metallocene catalysts and their catalytic activities for olefin polymerization

The synthesis and characterization of metallocene complexes which can be used as catalysts in the presence of MAO for olefin polymerization were discussed in the present paper. The metallocene complexes have been characterized by IR, H-1 NMR, EI-MS spectra and element analyses; The catalytic features of Olefin polymerization were studied under different conditions. Metallocenes in which metals is Ti had no activity for ethylene polymerization, Polymers with different features can be obtained by using different catalysts.