Application Of H Nmr Spectroscopy Method
APPLICATION OF H NMR SPECTROSCOPY METHOD
FOR DETERMINATION OF INTERACTION PARAMETERS
IN CELL-WATER SYSTEM
S.P. Gorbik, V.V. Turov
Institute of Surface Chemistry, Ukrainian National Academy of Sciences, General Naumov st. 17, 03164 Kyiv, Ukraine
The object of present investigation was to value the possibility of using liquid phase freezing method for cell suspensions and to measure with its assistance the parameters of live cells interaction between each other and with water medium. Frozen aqueous suspensions of bread yeast Saccharomyces cerevisiae were studied by the H NMR spectroscopy method combined with the liquid phase freezing technique. When frozen with the help of liquid nitrogen cells were exposed to the temperature of 77 K during 10 min, and after thawing them the viability index was about 90 %. When aqueous cell suspensions being exposed to the same procedure the viability index decreased to about 70 %. The characteristics of bound water layers and the values of interface energy (γS) in live cell suspensions were determined for the wide range of concentration of yeast (CY) in suspensions. The concentrations of intracellular and extracellular bound water were determined. Fig. 1 shows the dependence of γS on the concentration of extracellular water (СНО = 100 – CY). This dependence is observed to have two segments, and each of these can be characterized by the maximum value of interface energy (γS1 and γSmax). The first of these values (γS1 = 44 J/g) determines the change in the interface energy that takes place in diluting a gel-like cell suspension up to disappearance of secondary structure. The value of γSmax = 150 J/g determines the destruction of small cellular aggregates in diluted suspensions. Presented in Fig. 2 are the dependences of strongly and weakly bound water concentration on the concentration of yeast culture in suspensions,
and the presence of phase transition in varying the concentration of cells in a suspension is well registered on them. In the initial concentration point corresponding to the destruction of gel-like structures the concentration of
strongly bound water has the minimal value whereas that of weakly bound water has the maximum one. The values of adhesion power were calculated for
Fig. 1. Fig. 2.
the relatively low concentrations of cell culture in suspensions at which gel-like cellular structures were not formed in a solution. Adhesion powers were shown to act at the distances that could be compared to the linear sizes of cells. The high values of surface powers account for the high value of free surface energy. With the diminution in the concentration of cells in a suspension the values of adhesion power increase. This effect is due to the decreased probability of intercellular interactions.
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