ISSN:
0006-3525
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
Using a sensitive birefringence instrument, the birefringence arising from the orientation of the DNA chain during electrophoretic transport has been recorded. This birefringence is shown to proceed both from the alignment (stretching) of the molecule in the direction of the electric field and from the extension of the length of its primitive path (overstretching). The contribution of these two processes can be separated in the decay of the birefringence after the end of the application of the electric field. The fast relaxation of the overstretching occurs first and is demonstrated to be the main contribution to the birefringence. The orientation factor of the remaining stretched state and its decay can be quantitatively understood using the biased reptation model. It provides, in addition, a high value for the tube diameter or gel pore size a (4500 ± 450 Å for a 0.7% agarose gel with a c-0.6g dependence in the agarose concentration cg) and a low value for the effective charge per base pair (0.2e as compared to 0.5e using the condensation hypothesis). The contribution of overstretching to the birefringence is also quantitatively interpreted in term of the change in the mean length l of DNA inside a pore size a. The dynamics of decay of this overstretching is well represented by a stretched exponential with a stretching exponent α = 0.44. The mean decay time decreases slightly with increasing fields and scales with the overall DNA length close to N20. © 1993 John Wiley & Sons, Inc.
Zusätzliches Material:
14 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/bip.360330905
