THE EFFECTS OF RIBOSYLNUCLEOTIDE SUBSTITUTION AND METHYLATION ON THE STRUCTURE OF SYNTHETIC POLYNUCLEOTIDES (DNA CONFORMATION).
Item
-
Title
-
THE EFFECTS OF RIBOSYLNUCLEOTIDE SUBSTITUTION AND METHYLATION ON THE STRUCTURE OF SYNTHETIC POLYNUCLEOTIDES (DNA CONFORMATION).
-
Identifier
-
AAI8601708
-
identifier
-
8601708
-
Creator
-
WU, HAI-YOUNG.
-
Contributor
-
Michael J. Behe
-
Date
-
1985
-
Language
-
English
-
Publisher
-
City University of New York.
-
Subject
-
Chemistry, Biochemistry
-
Abstract
-
The A conformation of Poly (rG-dC)(.)Poly (rD-dC) in normal salt conditions is confirmed by its circular dichroic, Raman and NMR spectra. Its characteristic Z-A-Z transition from a very low salt condition (5 mM Tris-HCl) to a high salt condition is also described. In addition, the synthesis of the DNA copolymer Poly (rG-m('5) dC)(.)Poly (rG-m('5) dC) provides an opportunity to study the effect of C-5 position methyl groups on the salt induced conformational transition. The high salt A to Z transition point of Poly (rG-m('5) dC)(.)Poly (rG-m('5) dC) still remains at the 1-2 M NaCl concentration range, unlike the effect of the C-5 position methyl groups on Poly (dG-dc)(.)Poly (dG-dc), which lowers the B to Z transition point from 2.5 M to 0.7 M (Behe & Felsenfeld 1981). Additionally, the low salt transition of Poly (rG-m('5) dC)(.)Poly (rG-m('5) dC) requires a bulkier counterion than does the transition for the unmethylated Poly (rG-dC)(.)Poly (rG-dC). These results indicate that the methylation of cytosine in the C-5 position will not stabilize the Z structure of Poly (rG-dC)(.)Poly (rG-dC), as it does in the Z structure of Poly (dG-dC)(.)Poly (dG-dC).;The C-5 position methyl group on pyrimidine bases has another effect on DNA structure. Both Poly (rG-m('5) dC)(.)Poly (rG-m('5) dC) and Poly (dG-m('5) dC)(.)Poly (dG m('5) dC) have an alternating structure under normal salt conditions. Two closely spaced but distinct peaks in their ('31)P NMR spectra indicate two different phosphate atom environments. The same phenomenon is also seen in the ('31)P NMR spectrum of Poly (dA-dT)(.)Poly (dA-dT); the C-5 position methyl group is also present on the thymidine residues. It is obvious that the C-5 position methyl groups somehow effect the stacking of nucleotide bases which alters the phosphodiester torsional angle. This characteristic is true of every two nucleotide bases; therefore two distinct phosphate environments are shown. The effect of increasing percentages of methylated pyrimidines on the structure of Poly (dA-dU)(.)Poly (dA-dU) have been investigated. The results show that methylated pyrimidines play a large role in the stabilization of the "alternating B" conformation of DNA. In addition, the stable A-conformation of Poly (rG-dC)(.)Poly (rG-dC) in the normal salt condition has been used as a substrate for restriction enzyme Hha I and Hha I methylase. The results show that Hha I methylase works better on the A form than B form. (Abstract shortened with permission of author.).
-
Type
-
dissertation
-
Source
-
PQT Legacy CUNY.xlsx
-
degree
-
Ph.D.
-
Program
-
Biochemistry
