A Comparison of Glycine, Sarcosine, N,N-Dimethylglycine, Glycinebetaine and N-Modified Betaines as Liposome Cryoprotectants

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Abstract
— Glycinebetaine has previously been shown to be effective at reducing leakage from liposomes which are frozen then thawed. This study involved the preparation of a series of N‐modified betaines and the comparison of their cryoprotective activities with those of glycine, sarcosine, N,N‐dimethylglycine and glycinebetaine. All the compounds investigated, with the exception of (dimethyloctylammonio)acetate, reduced the degree of leakage, after freezing and thawing, with additive concentrations up to 0·6 m. Reducing the degree of N‐terminal methylation of glycinebetaine appeared to increase the leakage from liposomes at additive concentrations between 0·2 and 0·6 m. (Dimethylethylammonio)acetate, (dimethyl‐isopropylammonio)acetate and (N,N,N',N'‐tetramethylethylenediammonio)‐N,N'‐diacetate appeared to be no more effective than glycinebetaine, whereas improved protection was afforded by (triethylammonio)acetate and (diethylmethylammonio)acetate at most concentrations. This study demonstrates that the cryoprotective activity of glycinebetaine may be improved with modifications to the N‐terminal.