RNase-resistance structure

These results indicate that the poliovirus RF-RNA served as a template for the synthesis of RNA complementary to viral RNA (i.e. minus-strand RNA). Separated poliovirus minus- and plus-strand RNAs anneal with an efficiency of 60 % under our experimental conditions (RNA concentrations of 5 (xg/ml, assay of RNase resistance with Tj RNase and RNase I). This value is considerably lower than that found with reovirus (Shatkin and Banerjee, 1970) or phage RF-RNA (Bishop and Levintow, 1971). Part of the reannealed poliovirus RNA is found in a structure resembhng RI-RNA (Bishop and Levintow, 1971) (Koch and Vollertsen, unpubhshed). Therefore, the estimate of the synthesis of pohovirus-specific RNA in E. coli determined by RNase resistance of the annealed RNA represents only a minimal... 

An RNA-HNA (hexitol) hybrid duplex structure has been studied by NMR. " The P-P distances across the minor groove are a determinant for cleavage by RNase H. In the structure, the duplex is in an A-form, and the P-P bond distance similar to that for an RNA-RNA duplex, which may explain the resistance of HNA duplexes to RNase H. A self-complementary HNA duplex h(GCGCTTTTGCGC) containing a central T-tract has been studied by NMR. " The duplex exists in the A-form in the stem regions, with minor distortions in the T-tract causing a 9 A displacement of the helical axes. The T-tract is stabilised by wobble pairs enhancing the overall stability of the duplex. 

Electron microscopists had seen long strands with a double helical structure, sensitive to DNase but resistant to RNase, inside mitochondria. Biochemists have isolated mitochondrial DNA. Enough differences have been shown between nuclear and mitochondrial DNA that the two types of DNA can no longer be confused. Mitochondrial DNA differs from nuclear DNA in its chemical properties, base composition, and turnover. 

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