Very low-angle light scattering. A characterization method for high-molecular-weight DNA

✍ Scribed by Harold I. Levine; Robert J. Fiel; Fred W. Billmeyer Jr.

• Publisher: Wiley (John Wiley & Sons)
• Year: 1976
• Tongue: English
• Weight: 848 KB
• Volume: 15
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1976.360150705

✦ Synopsis

A very low-angle light-scattering photometer is described with respect to optical features, scattering cell, correction factors, and absolute calibration in the angular range 2'-35". An improved microfiltration apparatus was used to obtain essentially dust-free aqueous solutions for very low-angle light scattering. The instrument was calibrated with silicotungstic acid, an absolute molecular-weight standard, and the calibration was confirmed with the use of several secondary standards.

Very low-angle light-scattering measurements were made to determine the weight-average molecular weight M r and z-average radius of gyration Rg,* of a commercial preparation of calf-thymus DNA. Microfiltration of the solutions allowed measurements down to 6". The value M, = 20.0 X lo6 obtained by extrapolating 6"-9O data to 0' is more than three times that from 30'-75" data (6.38 X lo6) but -50% smaller than that from 10-35" data (23.7 X lo6). The experimental errors in M r and Rg,L are estimated to be f8% and 41496, respectively.

Combined 6"-75" data from two photometers fit well a theoretical scattering curve for a model wormlike coil of the same M, as the DNA sample.