The pa per pres ents some as pects cor re lat ing ther mal sta bil ity of RNA fold ing and the oc cur rence of struc tural mo tifs in nat u ral ri bo nu cleic ac ids. Par tic u larly, the ther- mody namic sta bil ity of 2 -5' and 3'-5' linked RNA and the contribution of unpaired ter mi nal nu cleo tides (dan gling ends) in sec ond ary (2D) and ter tiary (3D) struc tures of RNA are dis cussed. Both ex am ples sug gest that dur ing evo lu tion na ture se lected sequences and struc tures of RNA which are the most ther mally sta ble and ef fi cient for their bi o log i cal func tion.
The nucleotide sequence of the genomic RNA of a Polish isolate of a potato leafroll virus was determined. Some variations between the determined sequences were observed. A comparison of the frequency of sequence variants in particular regions of the genome is presented. The nucleotide sequence reported will appear in the EMBL Data Library under the accession number X74789.
This review gives a short account of selected aspects of oligoribonucleotide synthesis via the H-phosphonate method. It includes: (i) recent methods for the preparation of suitably protected ribonucleoside 3'-H-phosphonates (the phosphonylation step), (ii) some chemical and stereochemical features of the formation of H-phosphonate internucleosidic linkages, and (iii) stereoselective synthesis of oligoribonucleoside phosphorothioates using chemo-enzymatic approach.