Polymeric pH indicators immobilized PVA membranes for optical sensors of high basicity based on a kinetic process

Two kinds of polymeric pH indicators PPF (phenolphthalein-formaldehyde product) and CPF (o-cresolphthalein-formaldehyde product) immobilized cross-linked poly(vinyl alcohol) membranes (PPF-PVA and CPF-PVA) for optical intermittent determination of high basicity ([OH-] = 1-8 M) based on a kinetic process were developed. In our previous work, we had demonstrated that PPF-PVA and CPF-PVA could perform the determination of high pH values from pH 10.0 to 14.0. Here the discoloring kinetic behaviors of PPF-PVA and CPF-PVA were compared with those of free phenolphthalein, o-cresolphthalein and thymolphthalein. Experimental results and theoretical analysis indicated that the response behaviors of the optodes' membranes in concentrated NaOH solutions were diffusion-independent and still complied with the pseudo-first-order kinetics. In addition, two data analysis methods for determination were presented. One was directly based on the reduced absorbance: the other was based on the discoloring kinetic constant. It was found that the latter could perform a rapid (60 s) and reliable (relative standard deviation: 2.6%) determination for high basicity.

Dominant kinetic paths on biomolecular binding-folding energy landscape

The identification of kinetic pathways is a central issue in understanding the nature of flexible binding. A new approach is proposed here to study the dynamics of this binding-folding process through the establishment of a path integral framework on the underlying energy landscape. The dominant kinetic paths of binding and folding can be determined and quantified. In this case, the corresponding kinetic paths of binding are shown to be intimately correlated with those of folding and the dynamics becomes quite cooperative. The kinetic time can be obtained through the contributions from the dominant paths and has a U-shape dependence on temperature.

Quantifying the kinetic paths of flexible biomolecular recognition

Biomolecular recognition often involves large conformational changes, sometimes even local unfolding. The identification of kinetic pathways has become a central issue in understanding the nature of binding. A new approach is proposed here to study the dynamics of this binding-folding process through the establishment of a path-integral framework on the underlying energy landscape. The dominant kinetic paths of binding and folding can be determined and quantified. The significant coupling between the binding and folding of biomolecules often exists in many important cellular processes. In this case, the corresponding kinetic paths of binding are shown to be intimately correlated with those of folding and the dynamics becomes quite cooperative. This implies that binding and folding happen concurrently. When the coupling between binding and folding is weak (strong), the kinetic process usually starts with significant folding (binding) first, with the binding (folding) later proceeding to the end. The kinetic rate can be obtained through the contributions from the dominant paths. The rate is shown to have a bell-shaped dependence on temperature in the concentration-saturated regime consistent with experiment. The changes of the kinetics that occur upon changing the parameters of the underlying binding-folding energy landscape are studied.

Kinetic study of paracetamol on prolidase activity in erythrocytes by capillary electrophoresis with Ru(bpy)(3)(2+) electrochemiluminescence detection

We explored the CE with Ru(bpy)(3)(2+) electrochemiluminescence detection for the kinetic study of drug-enzyme interaction. Effects of four nonsteroidal anti - inflammatory drugs including aspirin, paracetamol, sodium salicylate and phenacetin on prolidase (PLD) activity in erythrocytes were investigated. Aspirin enhanced PLD activity whereas the other three had inhibiting effects. This may reveal their different effects on the collagen biosynthesis and catabolism that influence tumor invasiveness. Kinetic study of paracetamol on PLD showed that the value of Michaelis constant Km for PLD was 1.23 mM. The mechanism of PLD inhibition by paracetamol is noncompetitive inhibition, and the inhibitor constant K-i value obtained in our research was 9.73 x 10(3) mu g/L.

Synthesis and surface morphology of tetraaniline-block-poly(L-lactate) diblock oligomers

Tetraaniline-block-poly(L-lactide) diblock oligomers are synthesized via ring-opening polymerization. The diblock oligomers cast from all L-lactide selective solvent (chloroform) show spherical aggregates for the leucoemeraldine state, and ring-like structures that are composed of much smaller spherical aggregates for the emeraldine state. The formation mechanisms of the two different surface morphologies are discussed in detail.

Scanned probe oxidation on an octadecyl-terminated silicon (111) surface with an atomic force microscope: kinetic investigations in line patterning

Scanned probe oxidation (SPO) nanolithography has been performed with an atomic force microscope (AFM) on an octadecyl-terminated silicon (111) surface to create protuberant oxide line patterns under ambient conditions in contact mode. The kinetic investigations of this SPO process indicate that the oxide line height increases linearly with applied voltage and decreases logarithmically with writing, speed. The oxide line width also tends to vary with the same law. The ambient humidity and the AFM tip state can remarkably influence this process, too. As compared with traditional octadecylsilated SiO2/Si substrate, such a substrate can guarantee the SPO with an obviously lowered voltage and a greatly increased writing speed. This study demonstrates that such alkylated silicon is a promising silicon-based substrate material for SPO nanolithography.

Kinetic and electrochemical properties of icosahedral quasicrystalline Ti45Zr35Ni17Cu3 powder

Kinetic and electrochemical properties of icosahedral quasicrystalline Ti45Zr35Ni17Cu3 alloy powder as negative electrode material of Ni-MH battery have been investigated at different temperatures. The calculated results show that the apparent activation enthalpy of the charge-transfer reaction is 43.89 kJ mol(-1), and the activation energy of hydrogen diffusion is 21.03 kJ mol(-1). The exchange current density and the diffusion coefficient of hydrogen in the bulky electrode increase with increasing temperature, indicating that increasing temperature is beneficial to charge-transfer reaction and hydrogen diffusion. As a result, the maximum discharge capacity, activation property and high-rate dischargeability are greatly improved with increasing temperature. However, the charge retention and the cycling stability degrade with the increase of the temperature.

Computer simulation of Zn(II) speciation and effect of Gd(III) on Zn(II) speciation in human blood plasma

The speciation and distribution of Zn(II) and the effect of Gd(III) on Zn(II) speciation in human blood plasma were studied by computer simulation. The results show that, in normal blood plasma, the most predominant species of Zn(II) are [Zn(HSA)] (58.2%), [Zn(IgG)](20.1%), [Zn(Tf)] (10.4%), ternary complexes of [Zn(Cit)(Cys)] (6.6%) and of [Zn(Cys)(His)H] (1.6%), and the binary complex of [Zn(CYS)(2)H] (1.2%). When zinc is deficient, the distribution of Zn(II) species is similar to that in normal blood plasma. Then, the distribution changes with increasing zinc(II) total concentration. Overloading Zn(II) is initially mainly bound to human serum albumin (HSA). As the available amount of HSA is exceeded, phosphate metal and carbonate metal species are established. Gd(III) entering human blood plasma predominantly competes for phosphate and carbonate to form precipitate species. However, Zn(II) complexes with phosphate and carbonate are negligible in normal blood plasma, so Gd(III) only have a little effect on zinc(II) species in human blood plasma at a concentration above 1.0x10(-4) M.

Computer Simulation Tb(lll) Speciation in Human Blood Plasma

A multi phase model of human blood plasma was developed and the Tb(Ⅲ) speciation in this system was studied. The results show that the speciation of Tb(Ⅲ) depends on the concentration of Tb(Ⅲ). When the concentration of Tb(Ⅲ) is below 4.000×10 -8 mol/L, most of Tb(Ⅲ) exists as soluble species while the concentration of Tb(Ⅲ) is in between 4.000 ×10 -8 mol/L and 1.667×10 -2 mol/L, precipitates(TbPO 4 and Tb 2 (CO 3 ) 3 ) are the dominant species of Tb(Ⅲ). Among soluble Tb(Ⅲ) ...

Kinetic characteristics of the interaction between morphine and its antibody by SPR competitive immunoassay

It is impossible for surface plasmon resonance to measure directly the binding kinetics between a low-molecular-weight analyte interacting and its immobilized binding partner. Solution competition method was applied to the kinetic study of the interaction between morphine and its antibody. The affinity constant between the antibody of morphine and morphine-BSA immobilized on the sensor chip was also obtained. The result showed that the affinity of polyclonal antibody is stronger than that of monoclonal antibody. And it also indicated that the protein combined with the analyte affected the binding of antibody to antigen.

Kinetic analysis of TNF immune complex by using surface plasmon resonane

The kinetic analysis of the interaction between tumor necrosis factor(TNF) and its monoclonal antibody was performed by surface plasmon resonance(SPR) technique. The monoclonal antibody was immobilized to the surface of CM5 sensor chip by amine coupling. TNF at different concentrations was injected across the mAb immobilized surface. The interaction was recorded in real time and could be seen on the sensorgram. One cycle, including association, dissociation and regeneration, lasted no more than 15 min. The interaction results was evaluated using 1 : 1 Langmuir binding model. The kinetic rate constants were calculated to be: k =1.68 X 10(3) L (.) mol(-1) (.) s(-1), k(d) = 1.73 X 10(-4) s(-1), and the affinity constants K-A = 9. 7 X 10(3) L (.) mol(-1), K-r)= 1. 03 X 10(-7) Mol (.) L-1. The X-2 was 3.47, which showed that the interaction is consistent with the 1 : I model. We can see from the results that although there are two binding sites in one mAb molecule, TNF reacts with each site in an independent and noncooperative manner.

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.

Study on speciation of Pr(III) in human blood plasma by computer simulation

Speciation of Pr(III) in human blood plasma has been investigated by computer simulation. The speciation and distribution of Pr(III) has been obtained. It has been found that most of Pr(III) is bound to phosphate and to form precipitate. The results obtained-are in accord with experimental observations.

Kinetic study of Ce4+ extraction with Cyanex 923

Ce4+ extraction rate from aqueous sulphate solutions by Cyanex923 in heptane was studied using a constant interfacial cell with laminar flow at 30 degreesC. The experimental hydrodynamic conditions were chosen and the contribution of diffusion to the measured rate of reaction was minimized. Cerium extraction rate was measured at different chemical composition by varying the concentrations of hydrogen ion, sulphate and Cyanex923. A cerium-Cyanex923(B) extractive is formed at the interface. The data were analyszed in terms of pseudo-first order constants and a reaction mechanism was developed.

Studies on insoluble species of Gd (III) in human blood plasma by computer simulation

The insoluble species of Gd (III) in human blood plasma were investigated by computer simulation. The distribution of the Gd (I) species was obtained. It was found that most of the Gd (III) ions were bound to phosphate to form precipitate GdPO4 at the concentration of 1. 000 x 10(-7) mol/L and when the concentration of the Gd (III) increased to 3. 750 x 10(-4) mol/L, in excess of the concentration of phosphate, the Gd (III) ions were bound to carbonate to form another kind of precipitate, Gd-2 (CO3)(3).