Premium
Polarized electronic spectra of Z‐DNA single crystals
Author(s) -
Ho Pui S.,
Zhou Guangwen,
Clark Leigh B.
Publication year - 1990
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360300115
Subject(s) - chemistry , dipole , spectral line , absorption spectroscopy , crystal (programming language) , crystallography , transition dipole moment , helix (gastropod) , molecular physics , oscillator strength , perpendicular , chromophore , reflection (computer programming) , single crystal , absorption (acoustics) , optics , physics , geometry , photochemistry , programming language , ecology , mathematics , organic chemistry , astronomy , snail , computer science , biology
Abstract Polarized electronic absorption spectra of the (100) face of single crystals of the Z‐form double helical duplex of d(m 5 CGUAm 5 CG) have been obtained from Kramers‐Kronig analysis of reflection data. The c crystallographic axis is parallel to the helix axis and shows but weak absorption. The b axis is perpendicular to the helix axis and shows a structureless absorption band centered at 270 nm with an oscillator strength of 0.26. Calculations of the crystal spectra utilizing available transition moment data for the individual chromophores are carried through using the oriented gas model (no interbase interactions) and, again, employing all base‐base interactions (point dipole) in the duplex. The calculated hypochromism of the 270 nm band is much less than the experimental value obtained from the crystal data. The crystal spectra appear to be representative of Z‐form double helices of essentially infinite length and not of a collection of twelve base duplexes. No evidence for n π* transitions polarized parallel to the helix axis is found.