Analysis of Water Adsorption and Thermodynamic Properties of Three Rhei Radix et Rhizoma Decoction Pieces / 中国实验方剂学杂志

Objective:To investigate the moisture adsorption and thermodynamic characteristics of raw products， wine-processed products and fried charcoal products of Rhei Radix et Rhizoma， in order to guide their drying and storage. Method:Static isotherm weighing method was used to determine the adsorption isotherm curves of three Rhei Radix et Rhizoma decoction pieces at 25， 35， 45 ℃， and the test data were fitted with 7 commonly used water adsorption models to determine the best model for studying the adsorption thermodynamic parameters of these decoction pieces. Result:The best adsorption models of these three decoction pieces were all GAB model. At 25， 35， 45 ℃， the absolute safe moisture content of fried charcoal products was 7.43%， 6.79% and 6.20%， of wine-processed products was 8.68%， 8.17% and 7.03%， of raw products was 9.88%， 9.36% and 7.77%， respectively. At 25， 35， 45 ℃， the relative safe moisture content of fried charcoal products was 9.46%， 8.63% and 8.21%， of wine-processed products was 11.49%， 11.03% and 9.74%， of raw products was 13.49%， 12.66% and 11.14%， respectively. The net equivalent heat of adsorption （Qst） and differential entropy （Sd） of these three kinds of decoction pieces all decreased with the increase of equilibrium moisture content， Qst and Sd were in accordance with the entropy-enthalpy complementary theory. The constant velocity temperatures of raw products， wine-processed products and fried charcoal products of Rhei Radix et Rhizoma were 386.66， 391.15， 394.34 K （unit conversion of 1 K=-272.15 ℃）， their Gibbs free energies were 0.372 2， 0.406 0， 0.372 2 kJ·mol-1， respectively. Their adsorption processes were an unspontaneous process driven by enthalpy. Conclusion:The orders of equilibrium moisture content， monomolecular layer moisture content， Qst and Sd of three Rhei Radix et Rhizoma decoction pieces are all raw products>wine-processed products>fried charcoal products. The moisture absorption capacity of the decoction pieces is ranked as raw products>wine-processed products>fried charcoal products. The frying and roasting process significantly affects the hygroscopicity and thermodynamic properties of the three decoction pieces， the reason for this difference may be that the high temperature of the stir-frying results in the decrease of the hygroscopic groups and the increase of the hydrophobic materials in raw products， and the change in the texture of the decoction pieces. The research on the water adsorption characteristics of three Rhei Radix et Rhizoma decoction pieces can provide reference for selecting their storage conditions and drying process.

Kinetic properties of cell wall bound superoxide dismutase in leaves of wheat (Triticum aestivum L.) following stripe rust (Puccinia striiformis) infection.

Stripe rust (Puccinia striiformis f.sp. tritici) is the most devastating disease of wheat (Triticum aestivum L.) accounting huge economical losses to the industry worldwide. HD 2329 was a widely grown wheat cultivar which had become highly susceptible to stripe rust and was used to understand the biochemical aspects of the host pathogen interaction through characterization of superoxide dismutase (SOD). In the present study, two types of SOD, ionically or covalently bound to the particulate fraction were found in the stripe rust infected and uninfected wheat leaves of susceptible cultivar HD 2329. Cell walls of leaves contained a high level of SOD, of which 41-44% was extractable by 2 M NaCl and 10-13% by 0.5% EDTA in infected and uninfected leaves. The NaCl-released SOD constituted the predominant fraction. It exhibited maximum activity at pH 9.0, had a Km value of 1.82-2.51 for uninfected and 1.77-2.37 mM for infected, respectively with pyrogallol as the substrate, and a Vmax of 9.55-21.4 and 12.4-24.1 A min-1g-1FW. A temperature optimum of 20oC was observed for SOD of both uninfected and infected leaves. SOD showed differential response to metal ions, suggesting their distinctive nature. Inhibition of wall bound SOD by iodine and its partial regeneration of activity by mercaptoethanol suggested the involvement of cysteine in active site of the enzyme. These two forms showed greater differences with respect to thermodynamic properties like energy of activation (Ea) and enthalpy change (H), while entropy change (S) and free energy change (G) were similar. The results further showed that pathogen infection of the leaves of susceptible wheat cultivar induced a decrease in the SOD activity and kinetics which might be critical during the response of plant cells to the infection.

Molecular interactions and excess thermodynamic properties of mixed solutions of zinc sulphate and zinc nitrate at 303K by ultrasonic method.

The ultrasonic velocity, density and viscosity were measured in aqueous mixtures of zinc sulphate (Heptahydrate) and zinc nitrate (Hexahydrate) at 308 K. Acoustic parameters, such as specific acoustic impedance, free length, isotropic compressibility, molar compressibility, molar sound velocity, free volume, available volume, relaxation time, excess parameters and the deviation from the experimental values has been evaluated. The value of ultrasonic velocity decreases and comes to a minimum and then increases as the mole fraction of zinc nitrate increases in the mixed salt solution. The excess adiabatic compressibility of zinc sulphate and zinc nitrate mixed solution with water was positive at all concentrations, while it is negative at a mole fraction of 0.7945. Variation of these parameters with concentration indicates the non-linear behavior. This non-linear variation of velocity with increase in concentration indicates the complex formation between the constituents of mixture. The results were interpreted as per the intermolecular interactions.