Conformational transitions of poly(dA-dC).poly(dG-dT), poly(dA-dT).poly(dA-dT), and other alternating purine-pyrimidine DNAs were studied in aqueous ethanol solutions containing molar concentrations of sodium perchlorate, which is a novel solvent stabilizing non-B duplexes of DNA. Using CD and UV absorption spectroscopies, we show that this solvent unstacks bases and unwinds the B-forms of the DNAs to transform them into the A-form or Z-form. In the absence of divalent cations poly(dA-dC).poly(dG-dT) can adopt both of these conformations. Its transition into the Z-form is induced at higher salt and lower ethanol concentrations, and at higher temperatures than the transition into the A-form. Submillimolar concentrations of NiCl2 induce a highly cooperative and slow A-Z transition or Z-Z' transition, which is fast and displays low cooperativity. Poly(dA-dT).poly(dA-dT) easily isomerizes into the A-form in perchlorate-ethanol solutions, whereas high perchlorate concentrations denature the polynucleotide, which then cannot adopt the Z-form. At low temperatures, however, NiCl2 also cooperatively induces the Z'-form in poly(dA-dT).poly(dA-dT). Poly(dI-dC).poly(dI-dC) is known to adopt an unusual B-form in low-salt aqueous solution, which is transformed into a standard B-form by the combination of perchlorate and ethanol. NiCl2 then transforms poly(dI-dC).poly(dI-dC) into the Z'-form, which is also adopted by poly(dI-br5dC).poly(dI-br5dC).

• MeSH
• biofyzika MeSH
• biofyzikální jevy MeSH
• cirkulární dichroismus MeSH
• denaturace nukleových kyselin MeSH
• DNA chemie   MeSH
• ethanol MeSH
• konformace nukleové kyseliny * MeSH
• perchloráty MeSH
• poly dA-dT chemie   MeSH
• polydeoxyribonukleotidy chemie   MeSH
• roztoky MeSH
• sekvence nukleotidů MeSH
• sloučeniny sodíku MeSH
• spektrofotometrie ultrafialová MeSH
• techniky in vitro MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• DNA MeSH
• ethanol MeSH
• perchloráty MeSH
• poly dA-dT MeSH
• poly(d(G-T).d(C-A)) MeSH Prohlížeč
• polydeoxyribonukleotidy MeSH
• roztoky MeSH
• sloučeniny sodíku MeSH
• sodium perchlorate MeSH Prohlížeč