DNA, circular

Figure IL P-NMR spectra (left) of a, poly(dG-dC) poly(dG-dC) in buffer, b, poly(dG-dC) poly(dG-dC) modified to = OAO with [(dien)PtCP]Cl and c, sample in b after reusing the ethanol concentration to 40%. The arrow designates the resonance characteristic of Z -DNA, Circular dichroism spectra (right) of the...

Recently, electrochemical methods for the determination of DNA strand breaks at an electrode have been developed. With these methods, one singlestrand break (ssb) among >2 x 10 intact phospho-diesteric bonds can be determined in submicrogram amounts of DNA. Circular covalently closed super-coiled (sc) DNA is attached to HMDE. If there is a strand break a new electrochemical signal appears (Figure 5A). 

Superhelix density, a according to W. Bauer J.Vinograd [J. Mol Biol. 33 (1968) 141-172], the number of superhelical turns per 10 base pairs of the DNA circular duplex. It is therefore a measure of the strain on the DNA due to supercoiling. Negative S. d. ranging from 0.04 to 0.09 have been reported. 

Kumar R, El-Sagheer A, Tumpane J, Lincoln P, WiUielmsson LM, Brown T (2007) Template-directed oligonucleotide strand ligation, covalent intramolecular DNA circularization and catenation using cUck chemistry. J Am Chem Soc 129(21) 6859-6864. doi 10.1021/ja070273v... 

Inducement of F-DNA Circular Dichroism Signals for Duplex Deoxyribonucleotide Homopolymers by Polycationic Strings. Arch. Biochem. Biophys., Vol. 364, No. 1, pp. 129-131, ISSN 0003-9861. 

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