Liu Yong-Jun

Establishment of experimental model of bacterial growth under inhibitory conditions

The thermal curves ofB. subtilis andP. atruginosa were determined by using a 2277 Thermal Activity Monitor (Sweden). Under inhibitory conditions, an experimental model of bacterial growth was established. The growth rate constant (μ), deceleration rate constant (β) and optimum temperature (T) of bacterial growth were calculated.ZusammenfassungMittels eines 2277 Thermal Activity Monitor (Schweden) wurden die thermischen Kurven vonB. subtilis undP. atruginosa ermittelt. Unter Inhibitionsbedingungen wurde ein experimentelles Modell bakterielen Wachstums festgestellt. Die Wachstumsgeschwindigkeitskonstante μ, Verlangsamungskonstante α und optimale Temperature (T) für das bakterielle Wachstum wurden bestimmt.

Determination of the thermograms and establishment of the experimenal law for bacterial growth and study of kinetic properties

Abstract In this paper, we have recorded thermograms of bacterial growth using a 2277 thermal activity monitor. We have established the experimental law of bacterial growth and calculated the rate constant of the multiplication curve.

Determination of thermograms of bacterial growth and study of optimum growth temperature

Abstract In this paper, we have determined bacterial growth thermograms by using the 2277 thermal activity monitor. We have studied the multiplication curve of bacteria at different temperatures and calculated the rate constant and optimum growth temperature.

Study on the thermokinetic properties of bacterial growth

The power-time curves of bacterial growth at different temperatures were determined by using the 2277 Thermal Activity Monitor (Sweden). From these curves, the growth rate constant (μ) and activation energy (Ea) were calculated. According to the transition state theory of reaction dynamics, the activation entropy (ΔS≠), activation Gibbs free energy (ΔG≠) and equilibrium constant (K≠) of the activation state could be calculated. These results permitted thermodynamic analysis of the bacterial growth metabolism.

A study of the optimum fungistatic action of a synthetic medicine using a microcalorimetric method

Abstract In this paper, we have determined bacterial growth thermograms using a thermal activity monitor. We have also determined bacterial growth thermograms of inhibitor and have studied the fungistatic action of a synthetic medicine (W2). We have calculated the rate constant at different concentrations and with the optimum allowable concentration of the synthetic medicine W2.

Determination of power-time curves of bacterial growth

Bacterial growth power-time curves were determined with a 2277 Thermal Activity Monitor. Bacterial multiplication curves were measured at different temperatures and an experimental model was established. Both growth rate constants and lowest growth temperatures were calculated.

Reaction Mechanism and Regioselectivity of Cu(I)-Catalyzed Hydrocarboxylation of 1-Phenyl-propyne with Carbon Dioxide

Density functional theory (DFT) calculations have been used to conduct a detailed study of the mechanism involved the copper(1)-catalyzed hydrocarboxylation of 1-phenyl-propyne using CO2 and hydrosilane. Theoretical calculations suggested that the activated catalyst Cl2IPrCuH is initially generated in situ by the reaction of Cl2IPrCuF with (EtO)(3)SiH, and that the entire catalytic reaction involves three steps, including (1) the addition of Cl2IPrCuH to 1-phenyl-propyne to afford two isomeric copper alkenyl intermediates, which lead to the formation of the corresponding final alpha,beta-unsaturated carboxylic acid derivatives; (2) CO2 insertion to give the corresponding copper carboxylate intermediate; and (3) sigma-bond metathesis of the copper carboxylate intermediate with a hydrosilane to provide the corresponding silyl ester with the regeneration of the active catalyst. The results of our calculations show that the rate-limiting steps for the two paths leading to the two alpha,beta-unsaturated carboxylic acid derivatives are different. In Path a, the alkyne and CO2 insertion steps were both identified as possible rate-limiting steps, with free energy barriers of 68.6 and 67.8 kJ.mo1(-1), respectively. However, in Path b, the alkyne insertion step was identified as the only possible rate-limiting step with an energy barrier of 78.7 kJ.mol(-1). These results were in agreement with the experimental observations. It was also found that the alkyne insertion step controlled the regioselectivity of the products, and that electronic effects were responsible for the experimentally observed regioselectivity.

Effect of Hydroxylation on Structures and Proton Transfer of A-T Base Pairs

The structures and proton transfer processes of hydroxylated A-T base pairs were theoretically studied at the B3LYP/6-31++G(d,p)//B3LYP/6-31G(d,p) level. Our calculations revealed that hydroxyl radical could react with A-T at different positions to form eight stable adducts. The order of these adducts in energy is (8OH)A-T<A-T(6OH)<A-T(5OH)<(2OH)A-T<(4OH)A-T<(5OH)A-T<A-T(2OH)<A-T(4OH) (the number denotes the label of the atom in the A/T which is attacked by hydroxyl), which relates well with their structural changes upon the addition of hydroxyl radical. The interaction energy between A and T would increase slightly when hydroxyl radical reacts with the adenine, but it would decrease when the radical reacts with thymine. To study the proton transfer processes of the hydroxylated A-T base pairs, the most stable adducts, (8OH)A-T and A-T(6OH), were selected to give calculations. The calculated results indicate that the proton transfer processes of (8OH)A-T and A-T(6OH) follow the concerted mechanism, which is different from the stepwise mechanism of A-T. What is more, its energy barrier is lower than the corresponding energy of the latters first step (rate-determining step).