Quasielastic light scattering: Effect of ionic strength on the internal dynamics of DNA

✍ Scribed by Michel Caloin; Bernadette Wilhelm; Michel Daune

• Publisher: Wiley (John Wiley & Sons)
• Year: 1977
• Tongue: English
• Weight: 658 KB
• Volume: 16
• Category: Article
• ISSN: 0006-3525
• DOI: 10.1002/bip.1977.360161002

✦ Synopsis

Quasielastic light scattering is used to study the effect of ionic strength on the dynamic behavior of DNA. In a first approach the spectrum of scattered light is analyzed in terms of a single relaxation process. T h e large difference between the ohserved behavior and that expected according to a pure diffusional process reflects the contribution associated with internal modes, which increases with decreasing ionic strength. Such behavior is better allalyzed in terms of a double relaxation process hy using two relaxation times, the reciprocals of which are equal to D K 2 and D K ? + T,-' ( K ) , respectively. where r, ( K ) is an average value describing the set of' modes observed a t a given K value. Relative intensity and relaxation times. which are the more accurate parameters, were used to interpret the results. The observed increase of the relative contribution of' internal modes with decreasing ionic strength is actually a relative decrease of the diffusional contribution induced by a corresponding increase of the radius of gyration R(;. On the other hand, the reciprocal 7;' ( K ) of the relaxation time is a linear function of K' in the analyzed KRc: range and is insensitive to ionic strength between 10-'M and 1M. These results, when discussed according to Rouse's model, lead to define for each value of r;' ( K ) a corresponding mean-squared equilibrium length ( p f ) which is found to he a linear function of K-2.