The B reversible Z transition of poly(dI-br5dC).poly(dI-br5dC). A quantitative description of the Z form dynamic structure.
The study of poly(dI-br5dC).poly(dI-br5dC) films by infrared spectroscopy shows that in low salt concentration, the conformation of this polynucleotide belongs to the B-family and in high salt concentration to the Z-family. 31P nuclear magnetic resonance and circular dichroism confirm the existence of these two forms. By circular dichroism and ultraviolet absorption, it is shown that the equilibrium constant of the B reversible Z transition depends upon temperature. The deuteration rates of exchangeable protons involved in hydrogen bonds between base pairs were deduced from the changes in absorbance near 1700 cm-1. In the B-form, one class of protons is measured with an exchange half-time of 20 minutes. In the Z-form, two classes of protons are measured with very different exchange half-times, the exchange half-time of the slow protons being of the order of 850 minutes. By comparison of these results with those previously obtained for poly(dG-dC).poly(dG-dC), these very slow protons of these two Z-polynucleotides are identified as the cytosine amino protons. A quantitative description of the dynamic structure of the Z-form is presented.
D002942:Circular Dichroism; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D009690:Nucleic Acid Conformation; D009994:Osmolar Concentration; D011070:Poly I-C / Q000031:analogs & derivatives*; D011089:Polydeoxyribonucleotides; D013055:Spectrophotometry, Infrared; D013329:Structure-Activity Relationship
D011089:Polydeoxyribonucleotides; C019530:poly(dC-dG); D011070:Poly I-C