Abstract
A study was made of the thiol groups present in nuclei froin rat thymus gland. Of the total thiol content of the nuclei, 70% was associated with arginine-rich histones. Proteins, including those containing thiol groups, are lost from nuclei isolated in ionic medium. Nuclei isolated in sucrose medium STAsucrose (0.25M), calcium chloride (5 mM), and tris (5 mM), at pH 7.2! retain reproducible amounts of thiol compounds and glucose 6-phosphate dehydrogenase.'' The reactivity of thiol groups in nuclei isolated in sucrose medium is increased if the final suspension is made in ionic medium. STA1-/ sup 14/C!-N-Ethylmaleimide'' was used in conjunction with radioautography to investigate the distribution of thiol groups in the nuclear population from rat thymus. X-irradiation in vivo or in vitro decreases the concentration of thiol groups in nuclei isolated in sucrose medium; this effect is transient if the glutathione reductase, present in the nuceli, is not inhibited by 10 mu M-- Zn/ sup 2+/ ion. Xirradiation in vivo increases the number of reactive thiol groups especially in nuclei from small thymocytes; this effect is most obvious in nuclei isolated in ionic medium where the inhibitory action of x-irradiation on nuclear thiol groups is not detected. Linoleic acid peroxide,more » in concentrations approximately equimolar to the thiol concentration, decreased the thiol content of the nuclei. (auth)« less
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