By using an
in vitro model test system, a study was done on the preventive effect of 29 substances on freezing denaturation at -30°C for periods of 4 to 8 weeks.
The rate of denaturation was followed by estimating solubility, viscosity, and ATPase activity, as well as superprecipitation. The overall results might be summarized as follows:
Additives with marked effect: Glutamate, aspartate, cysteine, β-alanine, ϒ-aminobutyric acid, cysteate, acetylglycine and EDTA.
Additives with moderate effect: lysine, histidine, ornithine, serine, betaine and triphosphate.
Additives with little or no effect: glycine, isoleucine, phenylalanine, L- and DL-threonine, glutamine, asparagine, arginine, glycylglycine, folic acid, ethylenediamine, creatinine, pyrophosphate and phytin.
In the experiment testing the effect of the combined use of two kinds of amino acids, some synergistic effect was observed with the combination of lysine and threonine, of lysine and serine, as well as of lysine and cysteine. No increased effect was found when amino acids were added to glutamate.
Discussion of the results suggests that the protective effect of the substances are closely related with their functional groups, their spatial structure and other physico-chemical properties.
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