Reaction of a hydrated electron with gentamycin and collagen - A pulse radiolysis study

The reactions of a hydrated electron (e(aq)(-)) with aminoglycoside antibiotic gentamycin and collagen in aqueous medium at different pH have been investigated employing a pulse radiolysis technique. The pseudo-first order equation of reaction kinetics was used to give an accurate description of the decay of e(aq)(-) in gentamycin solutions. The rate constant of the(aq)(-) decay in collagen solution was high and reached 3.2 x 10(10) M(-1) s(-1). The rate constants for the reaction of the e(aq)(-) with gentamycin were found to be influenced by pH, decreasing with the deprotonation of the -NH3 groups, while for pH > pK(a) which for gentamycin is equal to 7.8, the rate constant was unchanged. These observations suggest that when the amino groups are protonated, reductive deamination occurs, but for unprotonated non-reactive amino groups, a radical anion is formed on the glycoside moiety.