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SynopsisPurine polyribonucleotides poly(A), poly(G), and poly(1) associate reversibly with agarose gels a t high NaCl molarities over the pH range 6-10, a t 2Oo-4O0C. Pyrimidine polyribonucleotides poly(C) and poly(U) could not be immobilized in agarose gels under the above conditions. However, poly(C) could be immobilized in agarose without precipitation between pH 3.2 and 4.0.Association of poly(G) and poly(1) with agarose appears to decrease progressively with deprotonation of their purine residues, and both polymers interact with the gel very weakly above pH 10 regardless of NaCl concentration. The binding to agarose of these polymers a t pH 7.5 is also strongly influenced by temperature in the range 2Oo-4O0C. The association of single-stranded poly(A) is only shifted toward higher NaCl molarities by increased pH; its binding is also little affected by temperature in the above range.At NaCl molarities effecting the saturating retention in agarose and a t neutral pH, the immobilization of several polynucleotides could be prevented by urea in a concentrationdependent manner. The corresponding profiles of urea molarity appear to disclose a number of hydrophobic interactions between polynucleotides and agarose, some of which could be relatively strong, especially in the case of poly(A).

Abstract— Following a single intracranial injection of [5‐3H]orotic acid, the decay dynamics were determined for rRNAs of whole brain in male and female Wistar‐inbred albino rats aged 2.5‐3.5 months. The turnover rate for male brain rRNAs was significantly lower than in females (mean half‐lives being, respectively, 12.2 ± 2.2 (S.D.M.) days, and 7.4 ± 1.3 days in four regression measurements). This difference was apparently not related to the turnover rate of acid‐soluble brain nucleotides, which turned over much faster and at a similar rate in rats of both sexes; it also could not be connected with brain levels of rRNAs or DNAs, which were quite similar For males and females. The results are discussed in terms of possible sex hormone determination of brain RNA metabolic patterns especially in males.