Studies on the interaction of homologues of spermine with deoxyribonucleic acid and with bacterial protoplasts

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Abstract
Four homologues of the naturally occurring polya-mine spermine, of the type H2N. [CH2 ]3. NH. [CH2]n. NH. [CH2]3. NH2 where n=2, 3, 5 and 6, have been synthesized. Their ability to stabilize Escherichia coli protoplasts against osmotic lysis was compared with that of spermine. All homologues were approximately as effective as spermine. The effect of low concentrations of the homologues on the Tm of calf thymus DNA and of Aerobacter aerogenes DNA in 0.03M-sodium chloride-imM-potassium dimethylglutarate buffer, pH 6.2, was tested. The increase in Tm for a given concentration of amine was found to be n=5 >=n=4 and n=6 >n=3 >n=2. When calf thymus DNA in 0.15M-sodium chloride-15mM-sodium citrate was used spermine gave the highest increase in Tm. It is concluded that the stabilization of E. coli protoplasts by tetra-amines is a non-specific effect independent of chain length, whereas the elevation of Tm of DNA is a more specific effect which depends on chain length.