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The dichroism of DNA in electric fields
Author(s) -
Ding DaWen,
Rill Randolph,
Van Holde K. E.
Publication year - 1972
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.1972.360111011
Subject(s) - chemistry , dipole , circular dichroism , helix (gastropod) , dna , dichroism , electric field , relaxation (psychology) , moment (physics) , linear dichroism , limiting , transition dipole moment , crystallography , nuclear magnetic resonance , physics , optics , biochemistry , organic chemistry , mechanical engineering , psychology , ecology , social psychology , classical mechanics , quantum mechanics , snail , biology , engineering
We have studied the dichroism of various samples of calf thymus DNA (of molecular weight from 3 × 10 5 to 7 × 10 6 ) in pulsed electric fields. The results may be summarized as follows: 1 We find that calf thymus DNA behaves in electrical orientation as if it possessed a large permanent dipole moment. This apparent moment is sensitive to such effects as Mg ++ binding which lower the net charge on DNA. 2 The limiting dichroism at infinite field corresponds to an angle of at least 80% between the transition moments at 265 nm and the helix axis, and could be consistant with a number of known forms of DNA. This result is independent of DNA molecular weight. There is evidence that the conformation may be different in 80% ethanol. 3 The dichroism relaxation curves contain a component with a relaxation time of about 8 μsec, which is nearly independent of molecular weight, and a longest component which behaves either according to the Broersma theory for low‐molecular‐weight samples, or the Zimm‐Rouse theory at high molecular weights.