ISSN:
0006-3525
Keywords:
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The Raman spectra of the double helical complexes of poly C-poly G and poly I-poly C at neutral pH are presented and compared with the spectra of the constituent homopolymers.When a completely double-helical structure is formed in solution a strong sharp band at 810-814 cm-1 appears which has previously been shown to be due to the A-type conformation of the sugar-phosphate backbone chain. By taking the ratio of the intensity of the 810-814 cm-1 band to the intensity of the 1090-1100 cm-1 phosphate vibration, one can obtain an estimate of the fraction of the backbone chain in the A-type conformation for both double-stranded helices and self-stacked single chains. This type of information can apparently only be obtained by Raman spectroscopy.In addition, other significant changes in Raman intensities and frequencies have been observed and tabulated: (1) the Raman intensity of certain of the ring vibrations of guanine and hypoxanthine bases decrease as these bases become increasingly stacked (Raman hypochromism), (2) the Raman band at 1464 cm-1 in poly I is asigned to the amide II band of the cis-amide group of the hypoxanthine base. It shifts in frequency upon base pairing to 1484 cm-1, thus permitting the determination of the fraction of I-C pairs formed.
Additional Material:
9 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/bip.1972.360110907
Permalink