the electrochemical oxidation and determination of tryptophan (trp) and glutathione (gsh) in the presence of catechol as a homogeneous redox in the aqueous medium were investigated at the surface of a carbon paste electrode modified with multi-walled carbon nanotube (mwcnt-cpe) using cyclic voltammetry (cv), double step potential chronoamperometry and differential pulse voltammetry (dpv) techni...

The fluorescence decay kinetics of aqueous tryptophan and 3-methylindole have been determined as a function of pH and temperature by using a picosecond dye laser-single photon counting system with a time resolution of 50 ps. At pH 11, tryptophan exhibits a single exponential decay, with a lifetime of 9.1 ns at 18 O C . However, at pH 7 the decay is faster and definitely nonexponential; the valu...

A computational method is developed to carry out explicit solvent simulations of complex molecular systems under conditions of constant pH. In constant-pH simulations, preidentified ionizable sites are allowed to spontaneously protonate and deprotonate as a function of time in response to the environment and the imposed pH. The method, based on a hybrid scheme originally proposed by H. A. Stern...

By utilizing Graphics Processing Units, we show that constant pH molecular dynamics simulations (CpHMD) run in Generalized Born (GB) implicit solvent for long time scales can yield poor pKa predictions as a result of sampling unrealistic conformations. To address this shortcoming, we present a method for performing constant pH molecular dynamics simulations (CpHMD) in explicit solvent using a d...

Protonation and carbamate formation are critical reactions for CO2 capture using amine-based absorbents which impact both absorption amine regeneration. In this regard, thermodynamic analysis towards in N-methylaminoethanol solution is carried out with specific attention to the corresponding protonation reactions. The mechanism investigated acquisition of reaction equilibrium constant heat reac...

The formation constants of the species formed in the systems H+ + Mo(VI) + histidine and H+ +histidine have been determined at different aqueous solutions of methanol (0 - 45 % v/v) at 25 °C andconstant ionic strength (0.1 mol dm-3 sodium perchlorate), using a combination of spectrophotometricand potentiometric techniques. The composition of the complex species was determined by thecontinuous v...

the formation constants of the species formed in the systems h+ + mo(vi) + histidine and h+ +histidine have been determined at different aqueous solutions of methanol (0 - 45 % v/v) at 25 °c andconstant ionic strength (0.1 mol dm-3 sodium perchlorate), using a combination of spectrophotometricand potentiometric techniques. the composition of the complex species was determined by thecontinuous v...

In order to clarify the reaction mechanism of Mryptophan 2,3-dioxygenase (L-tryptophan: oxygen oxidoreductase, EC 1.13.1.12), a hemoprotein, spectral and kinetic studies were carried out with highly puritied enzyme preparations from Pseudomonas fluorescens (ATCC 11299). A new spectrally distinct species of the enzyme heme omx; 418,545, and 580 mp) was observed during the steady state of the cat...

ion of the a-proton. The rate constant for the converkz sion of Intermediate 1 to Intermediate II with [a-Hlserine as Therefore, /L.~ = kZ = 3.17 s-1. substrate which we have obtained from stopped flow absorption For [a-Dlserine, kobs = 2.74 s-l = kz + kmz; kLJkz = 3. measurements (kobs = 6.3 s-l) is about 2 times higher than the Therefore, k-2 = 3 kt; k-z = 2.05 s-1; and kp = 0.685 s-1. rate c...