Physicochemical Alterations in Spleen Deoxyribonucleoprotein after in Vitro X-Irradiation with 850 R

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Abstract
The deoxyribonucleoprotein (DNP) complex was isolated from spleens of immature mice. The complex was non-dialyz-able, soluble in distilled water, and insoluble in aqueous 0.14 [image]NaCl; it had a UV absorption maximum at 260 m[mu] and a minimum at 239 m[mu]. The N/P ratio was 4.4 to 4.7. The complex contained approximately 5% ribonucleic acid. Incubation of DNP with added crystalline trypsin at 25[degree] resulted in the release of free DNA, and the rate of release was a function of trypsin concentration. In vitro X-irradiation of DNP with 850 r, followed by incubation with trypsin, resulted in a more rapid liberation of free DNA from the irradiated DNP than from non-irradiated nucleoprotein. When trypsin was not added, no differential release of DNA from irradiated versus nonirradiated DNP was detected. The ability of DNP to swell and dissolve in distilled water was employed as another criterion of radiation effect. After X-irradiation of DNP with 850 r, followed by incubation at 37[degree] for 30 minutes, there was a marked inhibition of its capacity to swell and form a gel in water. Pretreatment of nonirradiated DNP with aqueous 1 [image] NaCl- a procedure known to elicit dissociation of DNP - also resulted in decreased swelling of DNP in water. The experimental data provides evidence for the view that spleen DNP, per se, is radiosensitive at moderate X-ray doses.

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