Radiolysis of alpha, alpha-trehalose in concentrated aqueous solution; the effect of co-irradiated proteins and lipids.

gamma-Radiolysis (dose-rate: 0 X 89 Gy/s) or electron (e)-radiolysis (dose-rate: 5 X 10(7) Gy/s) of unbuffered aqueous solutions of alpha, alpha-trehalose (concentration: 60 mg/ml, radiation dose: 20 kGy) at 0 degree C yielded glucose (Ggamma = 1 X 7; Ge = 0 X 63) and 5-deoxyxylohexodialdose (Ggamma = 0 X 21; Ge = 0 X 05). Buffering at pH-values of 5 X 0 or 5 X 5 and irradiation caused increased formation of these monomeric products, particularly of the deoxy-compound. On addition of increasing amounts of bovine serum albumin or ovalbumin (10-30 mg/ml) and irradiation the yields of products were markedly reduced. The decrease in glucose formation was less pronounced when sperm whale myoglobin was present during gamma- or electron-irradiation. The G-values of 5-deoxyxylohexodialdose, however, were increased by 45 per cent (gamma-irradiation) and 70 per cent (electron-irradiation) at approximately 10 mg/ml of admixed myoglobin. Further increase in myoglobin concentration led to a gradual decrease in the yields of the deoxy-product. The observed effects are explained by scavenging of water radicals and by interactions of the added substrates with sugar radicals. Emulsified lipids (palmitic acid methylester or trilinoleic glycerol) did not affect the radiation-induced formation of products from trehalose.

Radiation damage in tripalmitin layers studied by means of infrared spectroscopy and electron microscopy.

Structural deteriorations in biomembranes, as inevitably induced while structural information is gathered by electron optical methods, were evaluated by infrared spectroscopy. Tripalmitin model membranes were irradiated with 100 keV-electrons in an electron microscope. The intensity decay of group vibrations over the dose reveals the sequence of damage in the polar and nonpolar part of the molecule. The C-C backbone, being the most important structural feature, shows a significant latency effect up to 0.6 e-/A2 and is completely disordered by 3 e-/A2, corresponding to about three inelastic processes per molecule.