Conformational states of cowpea chlorotic mottle virus ribonucleic acid components.

The conditions determining conformational changes in the four ribonucleic acid components of cowpea chlorotic mottle virus have been studied. All four components have at least two electrophoretically separable conformers, the occurrence of which can be regulated by both monovalent and polyvalent cations. This phenomenon also occurs, in a much less striking way, in the ribonucleic acids of the two other members of the bromovirus group, brome mosaic virus and broad bean mottle virus. Although specific in some respects, these changes have much in common with effects which have been observed in tRNAs, 55 RNAs and rRNAs. A provisional interpretation of the conformational behaviour of the viral RNAs is given in terms which have been proposed for certain tRNAs which have been studied in great detail.

A method for the purification of large quantities of biologically active ribonucleic acid components from cowpea chlorotic mottle virus, a multicomponent plant virus.

Cowpea chlorotic mottle virus RNA has been prepared in comparatively high yield (at least 50%) by a modified phenol extraction method. The preparation, which has high biological activity, has been resolved into four components by zonal centrifugation on a 15-40% (w/v) sucrose density gradient. The components obtained have been tested for biological activity against whole plants and plant protoplasts. Each of the two largest components RNA 1 and RNA 2 was by itself infective (50-90% of the specific infectivity of the whole genome) and produced virus-specific proteins (coat protein and P2) and RNAs ("RNA 3" and "RNA 4"). Contamination by small proportions (less than 10%) of neighbouring RNAs is presumed to be involved in this infectivity. The two smallest components were obtained in an almost pure form.

The preparation and analysis of a new trinucleotide from yeast ribonucleic acid, containing two adjacent 2'-O-methylpentose residues.

Quantities of the order of 10mg of three alkali-stable trinucleotides were prepared from yeast ribonucleic acid. Analyses showed that they were of the type N1m-N2m-N3p, where m signifies 2'-O-methylation of the pentose residue. One, Am-Um-Gp, is newly described.

Preparation, purification and analyses of thirteen alkali-stable dinucleotides from yeast ribonucleic acid.

Of the 16 alkali-stable dinucleotides known to be obtained by hydrolysis of commercial yeast RNA with alkali, 13 were prepared in quantities of the order of 10mg or more. The samples, with only one exception, contain at least 90% of dinucleotide, and spectroscopic constants and nucleotide-sequence determinations, although not conclusive, indicate a high degree of purity of these products. The small dinucleotide fraction in 150g of RNA hydrolysed with alkali (1-2% of the total nucleotides) was separated from the mononucleotides by stepwise ion-exchange chromatography on DEAE-cellulose columns and resolved into seven fractions containing from one to four different dinucleotides by electrophoresis on paper at pH3.0. These fractions were resolved into their constituent dinucleotides by chromatography in ammonium sulphate. Contamination of the products by impurities from the paper was minimized by washing it before using it for chromatography or electrophoresis and, by using a thick grade of paper (Whatman no. 17), it was possible to handle and purify relatively large quantities of nucleotides.