NOPR Collection:

Study on the electrochemical behaviour of cytochrome C at the gold electrode modified with 4-hydroxy-6-methyl-2-mercaptopyrimidine

2017-02-02T04:32:53Z

Title: Study on the electrochemical behaviour of cytochrome C at the gold electrode modified with 4-hydroxy-6-methyl-2-mercaptopyrimidine Authors: Chen, Miao; Li, Hu-lin Abstract: The reduction and oxidation of cytochrome C at the gold electrode modified with 4-hydroxy-6-methyl-2- mercaptopyrimidine (HMMP) has been investigated by cyclic voltammetry. It has been demonstrated that HMMP is an effective and stable promoter. The thermodynamic parameters of the electron-transfer reaction of cytochrome C at HMMPI/Au , electrode have been estimated in phosphate buffer solution containing 0.1 mol L^-I NaCIO₄. The normal potential E^o, the changes in entropy (∆S^o) enthalpy (∆H^o) and Gibb~ r:fnergy (∆G^o) for :1'tochrorrle C at 20°C and pH 7.0 have been found to be 0.267 V(vs. NHE), - 52.7 J mol^-1K^-1,- 41.25 kJ mol and -25.8 kJ mol^-1 , respectively. The temperature dependence of the formal redox potential £'" obtained in the temperature range of 5- 60°C shows remarkable biphasic character in an alkaline solution with a turning point at 45°C whereas. in an acid or neutral solution the E^o, values change monotonically with temperature which may be attributed to a structural change in the protein moiety of the cytochrome C in alkaline solution. Page(s): 283-287

A response model for surface acoustic wave enzyme sensor applied to the kinetic study of urease-catalytic reaction and urea determination

2017-02-02T04:26:57Z

Title: A response model for surface acoustic wave enzyme sensor applied to the kinetic study of urease-catalytic reaction and urea determination Authors: Tan, Huwei; Cha, Weixiong; Chen, Jinhua; Yao, Shouzhuo Abstract: A binary substrate-enzyme complex response model based on a surface acoustic wave (SAW) enzyme sensor has been derived to study enzymatic-catalytic reactions. It is applied to a non-linear least squares metho based on Marquardt algorithm by fitting urease-catalytic reaction data. The effect of initial values of rate constants on the programme convergence of the proposed method is discussed. The kinetic parameters have been estimated and these are of the same order of magnitude as those reported in the literature. As a comparison, the substrate (urea) concentration has been analyzed by the proposed method, the calibration method and the iterative Kalman filter method .The recovery in the case of the proposed method ranges from 98.0% to 103.2% while that for other two methods is in the range of 96.0- 104.4% and 97.2-103.8% respectively. These methods are also used to determine the urea content in human blood. The proposed method compares favourably with other methods and gives more precise results. Page(s): 288-294

A thermogravimetric study on the catalytic decomposition of ammonium perchlorate from activation energy normalised through kinetic compensation

2017-02-02T04:17:26Z

Title: A thermogravimetric study on the catalytic decomposition of ammonium perchlorate from activation energy normalised through kinetic compensation Authors: Ninan, K N Abstract: Though the reaction temperatures of both low (LTD) and high temperature (HTD) decompositions of ammonium perchlotate (AP) are lowered by CuO catalyst, the activation energy (E) for the reactions, computed from TG data shows an increase for LTD and a decrease for HTD. The values of both E and A ( pre-exponential factor) for LTD and HTD are altered in the presence of the catalyst, thereby making it not feasible to have a direct correlation of activation energy with the effect of the catalyst in enhancing the reaction rate. However, when E values are normalised for the' variation in the values of A, the activation energy is lower for both the stages of decomposition of AP in the presence the catalyst. In order to establish the normalisaltion procedure, the first two stages of the thermal decomposition of calcium oxalate monohydrate are chosen as model reactions. The values of E and A from both isothermal and non-isothermal experiments carried out under different experimental conditions of heating rate and sample mass of CaC₂O₄.H₂O show interdependence through kinetic compensation (KC) effect. The KC effect is also shown by the kinetic parameters from a single non-isothermal experiment, when they are calculated for different values of n. In all these cases, the values of E derived from the KC plots for a fixed value of A are remarkably constant and independent of the variations in experimental conditions for both the stages of decomposition of CaC₂O₄.H₂O. The pragmatic application of the newly proposed KC correction method of deriving consistent values of E, normalised for the variations in A values, has been demonstrated in the catalytic thermal decomposition of AP. Page(s): 295-302

Electronic structures and conduction properties of copolymers of furan and isonaphthofuran

2017-02-01T12:17:37Z

Title: Electronic structures and conduction properties of copolymers of furan and isonaphthofuran Authors: Rattan, Pooja Abstract: The electronic structures and conduction properties of the various periodic and aperiodic quasi-one-dimensional compositional superlattices (A_mB_n)_x (A = furan; B = isonaphthofuran) of Type-I have been investigated on the basis of simple negative factor counting method. It is found that increase in the percentage of smaller band gap component (INFU) (B) makes the copolymers more dopantphilic while increase in the percentage of larger band gap component (FU) (A) makes the' less dopantphilic. Page(s): 303-307