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A theory for polarized fluorescence microscopy of chromosome structures
Author(s) -
Basu Samarendra
Publication year - 1977
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.1977.360161014
Subject(s) - polarization (electrochemistry) , chemistry , dna , fluorescence anisotropy , molecular physics , perpendicular , dipole , fluorescence , molecule , degree of polarization , electric field , fluorescence microscope , crystallography , chemical physics , biophysics , optics , geometry , physics , scattering , biochemistry , mathematics , organic chemistry , quantum mechanics , biology
Abstract A theory for the determination of DNA arrangements in DNA‐containing specimens, using planar aromatic dye molecules as probes for plane polarization of fluorescence, has been described. At low dye‐to‐DNA concentrations, the dye molecules are sandwiched between the stacked bases of DNA; hence, the fluorescence from the dye bound to a local region of DNA helix is plane‐polarized with the polarization direction perpendicular to the local axis of DNA. The degree of such polarization from an aligned DNA‐specimen complexed with dye is determined both by the DNA orientation and the conformational state (e.g., base tilt) of DNA into that specimen. Analysis has been made of the relationship between the degree of polarization and the orientation of the emitting dipoles of dye. The dye complexes may be aligned in a mechanical shear or electric field. However, any change in the orientation distribution of the emitting dipoles due to force fields should be taken into account. With some assumptions and approximations, the magnitude and the direction of maximum polarization can be related to different orders of DNA coiling and to their various combinations. Since the measured polarization is averaged over all DNA regions of the specimen, if the magnitude of polarization is appreciable and the polarization occurs in the specific direction of the specimen, the theory helps to eliminate several probable arrangements of DNA. The predominant molecular features of the actual DNA arrangement can be determined through this process of elimination, as explained in two subsequent papers with T‐even bacteriophage and chromosome systems.