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Photon correlation spectroscopy, total intensity light scattering with laser radiation, and hydrodynamic studies of a well fractionated DNA sample
Author(s) -
Jolly Douglas,
Eisenberg Henryk
Publication year - 1976
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.1976.360150107
Subject(s) - chemistry , scattering , light scattering , intensity (physics) , molecular physics , dynamic light scattering , laser , spectroscopy , analytical chemistry (journal) , optics , atomic physics , physics , chromatography , quantum mechanics , nanoparticle
A Malvern laser light‐scattering instrument has been modified for use at scattering angles down to 5° and both total intensity and quasi‐elastic scattering experiments. A sample of sheared, length‐fractionated calf‐thymus DNA was characterized by sedimentation, viscosity and electron microscopy. Quasi‐elastic scattering and absolute intensity determinations were performed with the laser instrument and intensity determinations only with a Fica conventional light‐scattering photometer. The total intensity experiments gave M̄ w = (3.75 ± 0.15) × 10 6 and 〈 R 2 〉 1/2 z = (206.9 ± 10.3) nm which yielded a value for the persistence length, allowing for polydispersity, of 66 ± 6nm. The quasi‐elastic experiments at scattering angles below 20° gave D 0 20, w = (2.23 ± 0.06) × 10 −8 cm 2 /sec which combined with S 0 20, w = 15.6 in the Svedberg equation gave M̄ w = (3.73 ± 0.18) × 10 6 . In addition, from the higher angle data we extracted a value of the longest intramolecular relaxation time, τ1 of 17.5 msec. This is not in particularly good agreement with τ1 predicted by the Zimm–Rouse theory using our other experimental parameters. The disagreement may be due to the restricted applicability of the Zimm–Rouse spring‐bead model as a quantitative representation of DNA molecules. Alternatively, it may be due to present difficulties in the unambiguous interpretation of molecular motions from the experimental autocorrelation functions.