The microcalorimetric bioassay for acute cellular toxicity is based on metabolic heat production from cultured cells. Microcalorimetry is a quantitative, inexpensive, and versatile method for toxicology research. The biological response to toxicants is the inhibition of the heat production rate in cells and toxicity is expressed as the concentration of toxicant that is 50% effective in this inhibition (IC50). In this paper, the effect of Cd2+on Rhizopus nigricans growth was investigated at 25℃ The relationship between growth rate constants (k) and concentration of Cd (C) shows a logarithmic normal distribution, and described as k=1.2742×1061 exp[-1.810×10-3 (C+2 283.0)2], and IC50 is 0.72μg/ml. These signals are readily obtained by an LKB 2277-204 heat 50 conduction microcalorimeter.

The water-soluble quaternary ammonium salt of chitosan was synthesized by reaction of chitosan with glycidyl trimethylammonium chloride. It was characterized by Fourier transform infrared and carbon-13 magnetic resonance spectra. Its microbiostatic effects against Staphylococcus aureus, Escherichia coli and Candid albicans were explored by microcalorimetry. The antimicrobial activity of the quaternized chitosan was stronger in alkaline condition than that in weak acidic condition.

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 8C. By analyzing thermocurves, quantitative parameters could be obtained to characterize the interactions of host cells and phages. The parameters such as ka, Pmax, G etc. change regularly with the decrease of multiplicity of infection (MOI) value. Infection/lysis equations were fitted and the lytic rate constant kL 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.

The heat output of the non-growth metabolism of Chlorella vulgaris has been determined using an LKB-2277 BioActivity Monitor. The experimental results indicate that there is a turn-point on the metabolic thermogenic curves, which can be divided into two parts, an early phase and a later phase. For the early phase, there is a linear relationship between the metabolic power (P) and the cell concentration (C), and that the heat output produced by a single cell

The interaction between monoammonium glycyrrhizinate (MAG) and bovine serum albumin (BSA) were studied by fluorescence and absorption spectroscopy. The quenching mechanism of fluorescence of bovine serum albumin by monoammonium glycyrrhizinate was discussed. The binding sites number n and apparent binding constant K were measured by fluorescence quenching method. The thermodynamic parameters [1]H◦, [1]G◦, [1]S◦ at different temperatures were calculated. The distance r etween donor (bovine serum albumin) and acceptor (monoammonium glycyrrhizinate) was obtained according to F˝orster theory of non-radiation energy transfer. The results of synchronous fluorescence spectra and UV－vis absorption spectra show that the conformation of bovine serum albumin has been changed.