Biomedical subjects

Liu Yi

Publications and source records attributed to Liu Yi.

11 recordsLinked to original sources

PubMed2005

Some properties of the interaction between 2,2'-diselenadibenzoic acid and serum albumins.

The binding of 2,2'-diselenadibenzoic acid to bovine serum albumin (BSA) and human serum albumin (HSA) was studied by using fluorescence spectroscopy. The measurement was performed in Tris-HCl buffer aqueous medium at pH = 7.40. The quenching constant at 303 K was (3.277 +/- 0.046) x 10(13) L mol(-1) s(-1) for BSA, and (3.946 +/- 0.002) x 10(12) L mol(-1) s(-1) for HSA. Decreased quenching was observed in association with increased temperature. Our findings show that the observed binding constant is dependent on the ionic strength of the medium. It is said that electrostatic interactions play a role in the binding of 2,2'-diselenadibenzoic acid to serum albumin, in addition to the hydrophobic association. The decrease of the linearity of S-V plot demonstrates reduced binding of ligand to the protein in the presence of anionic surfactants such as sodium dodecyl sulfate (SDS), which indicates that 2,2'-diselenadibenzoic acid most likely binds to the hydrophobic pockets within sub-domain IIA of serum albumin, the same site as SDS.

Caproates↗

PubMed2005

Microcalorimetric studies of the action of Er3+ on Halobacterium halobium R1 growth.

A microcalorimetric technique was used to evaluate the influence of Er3+ on Halobacterium halobium R1 growth. By means of a LKB-2277 Bioactivity Monitor ampoule method, we obtained the thermogenic curves of H. halobium R1 growth at 37 degrees C. In order to analyze the results, the relationship between k and C was obtained. The addition of Er3+ in low concentration cause a decrease of the maximum heat production P max and growth rate constants k; however, Er3+ in a high concentration might promote growth of H. halobium R1. When Er3+ is in a much higher concentration, the growth of H. halobium R1 is inhibited completely. For comparison, the shapes of H. halobium R1 cells were observed by means of transmission electron microscope (TEM). According to the thermogenic curves and TEM photos of H. halobium R1 under different conditions, it is clear that the metabolic mechanism of H. halobium R1 growth has been changed with the addition of Er3+.

Calorimetry↗

PubMed2004

Microcalorimetric investigation on the growth model and the protein yield of Bacillus thuringiensis.

A novel microcalorimetric technique based on the bacterial heat output was applied to evaluate the special growth model, the protein expression and the generation time of Bacillus thuringiensis for the first time. The thermogenic curves of the aerobic metabolism of B. thuringiensis strains YBT-833, YBT-1520 and YBT-833-2-1 were determined by using an LKB-2277 BioActivity Monitor. The analysis of the thermogenic curves indicated both the mutant strain and the wild-type strains followed the same linear growth model during sporulation. The metabolism heat output revealed heat output was correlated to the yield of the insecticidal crystal proteins (ICPs) very well, the more protein product, and the less heat output. Based on the data acquired, we proposed that this method could be a useful tool in monitoring the fermentation of B. thuringiensis.

Bacillus thuringiensis↗

PubMed2004

Absorption and fluorescence study of the interaction between (2-hydroxy-benzimido)ethyl-n-hexylselenide and bovine serum albumin.

The binding of Schiff base selenide, (2-hydroxy-benzimido)ethyl-n-hexylselenide, to bovine serum albumin (BSA) was studied using fluorescence spectroscopy. The measurement was performed in Tris-HCl buffer aqueous medium at pH 7.4. Stern-Volmer graphs were plotted and quenching constants were estimated. The quenching constant at 303 K was (1.639 +/- 0.046) x 10(13) L mol(-1) s(-1). Decreased quenching was observed as temperature increased, but at the temperature range of 303-313 K, the association of Schiff base selenide to BSA was not significantly different. The static quenching presented in the system of Schiff base selenide and BSA. A complex was possibly formed between Schiff base selenide and BSA, which was responsible for the quenching of the fluorescence of BSA. This fact was also confirmed by differences in the absorption spectra of BSA before and after Schiff base selenide addition. The hydrophobic interaction was found to play a main role in the binding according to the thermodynamic parameters, enthalpy change (DeltaH) and entropy change (DeltaS) of reaction. Schiff base selenide most likely binds to the hydrophobic pockets within sub domain IIA of BSA, which can be proved by competition experiments for sodium dodecyl sulfate. By constant-wavelength synchronous fluorescence spectra, the influence of (2-hydroxy-benzimido)ethyl-n-hexylselenide on the surrounding environment of tyrosine and tryptophan residues in BSA was also investigated. The red shift of the fluorescence peak of tryptophan residues indicated that the hydrophobic amino acid structure surrounding tryptophan residues in BSA collapsed slightly after the addition of (2-hydroxy-benzimido)ethyl-n-hexylselenide.

Absorption↗

PubMed2003

Study on interaction between T4 phage and Escherichia coli B by microcalorimetric method.

The process that T4 phages multiply in host cells of Escherichia coli B was determined using LKB-2277 Bioactivity Monitor by means of stopped-flow method, and the growth was measured turbidometrically at the same time at 37 degrees C. By analyzing thermo-curves, quantitative parameters could be obtained to characterize the interactions of host cells and phages. The parameters such as k(a), P(max), G etc. change regularly with the decrease of multiplicity of infection (MOI) value. Infection-lysis equations were fitted and the lytic rate constant k(L) was obtained. The results show that the metabolic activity of infected cells is more intensive than that of normal cells. The phenomenon of lysis inhibition (LIN) was first detected with the microcalorimetric method, and the mechanism is discussed.

Bacteriolysis↗

PubMed2003

Study of the thermokinetic properties of copper(II) on Escherichia coli growth.

By using an LKB2277 Bioactivity Monitor, stop-flow mode, the power-time curves of Escherichia coli at 37 degrees C affected by Cu(II) were determined. Some parameters, such as growth rate constants k, inhibitory ratio I, the heat output Qlog in the log phase, and the generation times G were obtained. According to these parameters, we found that a low concentration of Cu(II) (0-20 microg/mL) had an promoting action on the growth of E. coli, but a high concentration of Cu(II) (40-100 microg/mL) had an inhibitory action. The toxicity of Cu(II) can also be expressed as the half-inhibitory concentration IC50; the value is 69.7 microg/mL. The assay is quantitative, inexpensive, and versatile.

Algorithms↗

PubMed2003

Microcalorimetric investigation of the effect of manganese(II) on the growth of Tetrahymena shanghaiensis S199.

The heat output of and the effect of manganese (II) on Tetrahymena shanghaiensis S199 growth metabolism has been determined by means of a LKB-2277 BioActivity monitor. Different concentrations of manganese(II) ions have different effects on the growth of T. shanghaiensis. At low concentrations (0-40 microg/mL) culture growth is promoted, whereas high concentrations (60-800 microg/mL) slow growth. Furthermore, concentrations of 1200 microg/mL or greater stop the growth of this protozooa completely.

Algorithms↗

PubMed2003

Effect of Sm(3+) ion on growth of Bacillus thuringiensis by microcalorimetry.

By using an LKB-2277 Bioactivity Monitor, cycle-flow method, the thermogenic curves of aerobic growth for Bacillus thuringiensis cry II strain at 28 degrees C have been obtained. The metabolic thermogenic curves of B. thuringiensis cry II contained two distinct patterns: the first reflects the changes during the bacterial growth phase and the second corresponds to the sporulation phase. From these thermogenic curves in the absence and presence of Sm(3+) ions, the thermokinetic parameters such as the growth rate constants k, the interval time tau(I), the maximum power P (max 1) and heat-output Q(log) for log phase, the maximum power P (max 2) and heatoutput Q(stat) for stationary phase, the heat-output Q(spor) for sporulation phase and total heat effects QT are calculated. Sm(3+) ion has promoting action on the growth of B. thuringiensis cry II in its lower concentration range; on the other hand, this ion has inhibitory action on the sporulation of B. thuringiensis in its higher concentration range. We also found that the effects of Sm(3+) ion on B. thuringiensis during the sporulation phase were far greater than that during the bacterial phase. It is concluded that the application of B. thuringiensis for controlling insecticides is not affected by the presence of the rare-earth elements in the environmental ecosystem.

Bacillus thuringiensis↗

PubMed2002

Microcalorimetric study of the action of Ce(III) ions on the growth of E. coli.

A microcalorimetric technique based on bacterial heat output was used to evaluate the action of Ce(III) ions on the growth of Escherichia coli. The power-time curves of the growth metabolism of the bacteria were studied in the presence and absence of Ce(III) by means of a LKB-2277 Bioactivity Monitor, by a stopped-flow method at 37 degrees C. For evaluation of the results, the maximum power, Pmax, the growth rate constant k, and the heat effects Qlog, Qstat, and Qtot for the log phase, the stationary phase, and total heat output, respectively, were determined. For comparison, a spectrophotometer was used to estimate the number of cells in the liquid culture. The shape of the bacteria was examined by electron microscopy. We concluded that the presence of cerium ions at concentrations below 350 microg/mL have a stimulatory effect on the growth of E. coli, whereas concentrations at or above 400 microg/mL may have an inhibitory effect.

Calorimetry↗

PubMed2002

[Comparison of parameter optimization algorithms for environmental model].

Parameters identification is achieved through the minimization of objective function based on model outputs and the observed data. Because of ever increasing complexity of environmental-models, there are significant difficulty for conventional optimal methods to present a global optimization. On the contrast, however, direct optimization algorithms are widely developed in recent years due to increasing computer efficiency and show promising applications. Four direct optimal algorithms, i.e. CRS algorithm, SCE UA algorithm, SA algorithm and Annealing-Simplex algorithm, were thus selected in this paper to compare their performances via case studies.

Algorithms↗

PubMedDate not supplied

The action of Cu2+ on Bacillus thuringiensis growth investigated by microcalorimetry.

By using an LKB-2277 Bioactivity Monitor, ampoule mode, the heat output of Bacillus thuringiensis growth metabolism has been determined at 28 degrees C and effect of Cu2+ on B. thuringiensis growth was studied. Copper has been regarded as an essential trace element for life. Its deficiency may be the cause of diseases. Cu2+ of different concentration have different effects on B. thuringiensis growth metabolism, Cu2+ of low concentration (0-30 micrograms/ml) can promote the growth of B. thuringiensis, and Cu2+ of high concentration (40-120 micrograms/ml) is able to inhibit its growth and B. thuringiensis can't grow at all when the concentration of Cu2+ is up to 130 micrograms/ml.

Bacillus thuringiensis↗