Energy transport in carbohydrates. Part II. Radiation decomposition of D-glucose

Abstract

Direct isotope dilution analysis has been employed to measure the –G-values for the degradation of anhydrous α- and β-D-glucose and α-D-glucose monohydrate on γ-irradiation. The anhydrous forms behave identically, and initial –G-values of ca. 20 have been obtained. The monohydrate is more resistant to radiation, and the initial –G is ca. 11. For each of the forms the –G-value decreases as irradiation is continued. After freeze-drying from aqueous solution, the anhydrous polycrystalline D-glucose produced is more resistant to radiation (initial -G ca. 7), and the results confirm previous observations based on acid yields. Gluconic and glucuronic acids have been identified and estimated among the acid products. Other aldehydic acids are also produced, and yield–dose curves for these acids indicate that fragmentation of the D-glucose occurs during the initial chemical act. Although the overall yields of irradiation products varied for the various forms examined, no difference was observed in the nature of the products. The high decomposition rates observed for the hexoses indicate that these molecules provide favourable conditions for energy transport and undergo greater degradation in the solid state than in solution. A resonance-energy transport mechanism associated with the three-dimensional network of hydrogen bonds in the crystals is outlined. The mechanism accounts for the greater radiation stability of the monohydrate and the freeze-dried state (which contains considerable imperfection in the crystal lattice).