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Viscosity and sedimentation study of sonicated DNA–proflavine complexes
Author(s) -
Cohen Gerald,
Eisenberg Henryk
Publication year - 1969
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.1969.360080105
Subject(s) - proflavine , chemistry , viscosity , ionic strength , persistence length , sedimentation coefficient , dna , intrinsic viscosity , binding constant , relative viscosity , intercalation (chemistry) , crystallography , molecule , analytical chemistry (journal) , thermodynamics , inorganic chemistry , aqueous solution , chromatography , binding site , organic chemistry , biochemistry , physics , enzyme , polymer
The intrinsic viscosity of sonicated calf thymus DNA (molecular weight 4–5 × 10 5 ) increases and the sedimentation constant decreases, with increasing binding of proflavine at 0. 2 ionic strength and at 25°C. The measurements correspond to a linear increase in length of the almost rodlike DNA molecules with the amount of proflavine bound; independent calculations from viscosity and sedimentation measurements yield almost identical results. Over the range of r (moles of proflavine bound per moles of nucleotides) equal to zero to r = 0.13, the length increases by about 20%. This extension is compatible with the intercalation hypothesis proposed by Lerman. Density increments at various values of r , at constant chemical potential of diffusible solutes, were determined. It was also found that, in addition to the known isosbestic point of DNA‐proflavine complexes at 455.5 mμ, an additional isosbestic point exists at 225.5 mμ; this proved extremely useful for the evaluation of binding studies.