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We have determined diversities exceeding 10(12) different sequences in an annealing and melting assay using synthetic randomized oligonucleotides as a standard. For such high diversities, the annealing kinetics differ from those observed for low diversities, favouring the remelting curve after annealing as the best indicator of complexity. Direct comparisons of nucleic acid pools obtained from an aptamer selection demonstrate that even highly complex populations can be evaluated by using DiStRO, without the need of complicated calculations.

Submitted by Guilherme Lemeszenski (guilherme@nead.unesp.br) on 2014-02-26T17:05:08Z No. of bitstreams: 0 Made available in DSpace on 2014-02-26T17:05:08Z (GMT). No. of bitstreams: 0 Previous issue date: 1992-12-01 Submitted by Vitor Silverio Rodrigues (vitorsrodrigues@reitoria.unesp.br) on 2014-05-20T15:21:00Z No. of bitstreams: 0 Made available in DSpace on 2014-05-20T15:21:00Z (GMT). No. of bitstreams: 0 Previous issue date: 1992-12-01 The frequency of adenine mononucleotides (A), dinucleotides (AA) and clusters, and the positions of clusters, were studied in 502 molecules of the 5S rRNA.All frequencies were reduced in the evolutive lines of vertebrates, plants and fungi, in parallel with increasing organismic complexity. No change was observed in invertebrates. All frequencies were increased in mitochondria, plastids and mycoplasmas. The presumed relatives to the ancestors of the organelles, Rhodobacteria alfa and Cyanobacteria, showed intermediate values, relative to the eubacterial averages. Firmibacterid showed very high number of cluster sites.Clusters were more frequent in single-stranded regions in all organisms. The routes of organelles and mycoplasmas accummulated clusters at faster rates in double-stranded regions. Rates of change were higher for AA and clusters than for A in plants, vertebrates and organeltes, higher for cluster sites and A in mycoplasmas, and higher for AA and A in fungi. These data indicated that selection pressures acted more strongly on adenine clustering than on adenine frequency.It is proposed that AA and clusters, as sites of lower informational content. have the property of tolerating positional variation in the sites of other molecules (or other regions of the same molecule) that interact with the adenines. This reasoning was consistent with the degrees of genic polymorphism. low in plants and vertebrates and high in invertebrates. In the eubacteria endosymbiontic or parasitic to eukaryotes, the more tolerant RNA would be better adapted to interactions with the homologous nucleus-derived ribosomal proteins: the intermediate values observed in their precursors were interpreted as preadaptive.Among other groups, only the Deinococcus-Thermus eubacteria showed excessive AA and cluster contents, possibly related to their peculiar tolerance to mutagens, and the Ciliates showed excessive AA contents, indicative of retention of primitive characters. FREE UNIV BERLIN,FACHBEREICH CHEM,INST BIOCHEM,W-1000 BERLIN 33,GERMANY