Title
Electronic and vibrational circular dichroism spectroscopic study of non-covalent interactions of meso-5,10,15,20-tetrakis (1-methylpyridinium-4-yl)porphyrin with (dG-dC)10 and (dA-dT)10
Author
Jakub Novy, Marie Urbanová, Karel Volka
Year
2007
Journal
Vibrational Spectroscopy
Abstract
The non-covalent interactions of (dG-dC)10 and (dA-dT)10 with 5,10,15,20-tetrakis(1-methylpyridinium-4-yl)porphyrin (TMPyP) were studied using the combination of electronic circular dichroism (ECD), vibrational circular dichroism (VCD) spectroscopy, and UV–vis and IR absorption spectroscopy at different ratios of both componentsr = [oligonucleotide]/[TMPyP] = 2/1–10/1 where [oligonucleotide] and [TMPyP] are the amount concentrations of oligonucleotide per base-pair and TMPyP, respectively. It was shown that TMPyP with (dG-dC)10 provided hemiintercalative binding mode for r = 4/1 that is manifested in vibrational spectra: The absorption band assigned to the C6double bond; length as m-dashO6 stretching vibration of guanine is shifted from 1683 to 1672 cm−1, the corresponding VCD couplet from 1694(−)/1674(+) to 1684(−)/1663(+) cm−1 and its intensity decreases. The absorption band assigned to the C2double bond; length as m-dashO2 stretching vibration of cytosine is shifted from 1652 to 1644 cm−1 and its intensity increases. TMPyP with (dA-dT)10 provided three binding modes: (i) external binding to the phosphate backbone, (ii) external minor groove binding for the ratios >6/1 and (iii) external major groove binging associated with the partial B- to Z-transition for the ratios <4/1. The major groove binding is manifested in VCD spectra by the intensity decrease of the bands 1655 and 1638 cm−1 assigned to the thymine vibrations while the bands assigned to the adenine vibrations are unchanged. In the (dA-dT)10–TMPyP complexes, the external binding to the phosphate backbone accompanied by self-stacking of porphyrins along the phosphate backbone chain is preferred at temperatures higher than 40 °C.
Instrument
J-810
Keywords
Circular dichroism, Biochemistry