Electron spin resonance studies have been carried out on irradiated molecular mixtures containing a macromolecule (Sephadex, CM-Sephadex or DEAE-Sephadex) and a sulfur compound (reduced or oxidized penicillamine). The pH prior to freeze-drying was in all cases adjusted to predetermined values. The irradiation as well as the electron spin resonance measurements were carried out at 77°K. The transfer of radiation energy from uncharged Sephadex occurred more efficiently to oxidized penicillamine than to reduced penicillamine when the samples were freeze-dried from acid solutions, while the opposite was the case when the samples were freeze-dried from alkaline solutions. The pH prior to freeze-drying influenced greatly the temperature range where the major part of the transfer of unpaired spins occurred from the macromolecule to the disulfide. While no further energy transfer occurred to oxidized penicillamine when the samples were heated above room temperature, an extensive transfer of unpaired spins took place from the macromolecule to the thiol in the temperature range 293°K to 333°K. This transfer seemed to involve mainly the dissociated form of the thiol. The results suggest that the pH prior to lyophilization influences the course of the secondary radical reactions occurring upon heat treatment of the samples while it has only a minor influence on the stability of the radicals present immediately after irradiation at 77°K.

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