The dichroism of DNA in electric fields

✍ Scribed by Da-Wen Ding; Randolph Rill; K. E. Van Holde

• Publisher: Wiley (John Wiley & Sons)
• Year: 1972
• Tongue: English
• Weight: 937 KB
• Volume: 11
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1972.360111011

✦ Synopsis

We have studied the dichroism of various samples of calf thymus DNA (of molecular

The results may be sumweight from 3 X lo5 to 7 X lo6) in pulsed electric fields.

marized 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 t o 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 a t 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 psec, 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.