Nucleic_acid_structure

Nucleic_acid_structure - DNA genomes Relaxed and...

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Nucleic acid structure
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Comparison of the B and A forms of duplex DNA major groove wide and deep minor groove narrow and deep minor groowe wide and shallow major groove narrow and deep
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Structural features of ideal A-, B-, and Z-DNA
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B-DNA C2’ endo anti bases ~perpindicular to helix axis (6 o )
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Conversion of B-DNA to Z-DNA
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The sterically allowed orientations of purine and pyrimidine bases with respect to their attached ribose units.
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Sugar pucker A-RNA B-DNA Z-DNA: C3’ endo for R, C2’ endo for Y
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Major force holding DNA together: hydrophobic interaction (base stacking)
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RNA-DNA hybrid Double helical RNA and RNA-DNA duplexes assume a conformation like A DNA or intermediate between A and B DNA. RNA-DNA duplex: tilt of bases relative to helix axis ~15 o width of minor groove (~ 9.5Å) between that found in A DNA (11Å) and B DNA (7.4 Å)
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Conformations of single-stranded nucleic acids
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Base pairing in one type of DNA triple helix
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Unformatted text preview: DNA genomes Relaxed and supercoiled duplex circular DNA Forming a DNA supercoil Toroidal and interwound supercoils Type IA topoisomerase action Single strand cleavage One strand of the cleaved DNA is covalently attached to protein via a phosphotyrosine linkage. Usually relax negative supercoils in DNA. Eg. TopoI and TopoIII of E. coli . Humans have an enzyme that relaxes positive supercoils. Type II topoisomerase action. Eg: E. coli DNA gyrase Adds negative supercoils to DNA at expense of ATP cleavage. 5 ends of DNA covalently attached to protein. Inhibitors of bacterial enzymes are potent antibiotics (ciprofloxacin, coumarin, novobiocin). Inhibitors of human enzymes are used in cancer chemotherapy (doxorubuicin, camptothecin) Model for the action of type II topoisomerase...
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This note was uploaded on 02/17/2012 for the course CHEM 212 taught by Professor Staff during the Fall '10 term at Rutgers.

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Nucleic_acid_structure - DNA genomes Relaxed and...

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