engleski

Short-fragment Na-DNA dilute aqueous solutions: Fundamental length scales and screening

Dielectric spectroscopy is used to investigate fundamental length scales of 146 bp short-fragment (nucleosomal) dilute Na-DNA solutions. Two relaxation modes are detected: the high- and the low-frequency mode. Dependence of the corresponding length scales on the DNA and on the (uni-valent) salt concentration is studied in detail, being different from the case of long, genomic DNA, investigated before. In low-added-salt regime, the length scale of the high frequency mode scales as the average separation between DNAs, though it is smaller in absolute magnitude, whereas the length scale of the low-frequency mode is equal to the contour length of DNA. These fundamental length scales in low-added-salt regime do not depend on whether DNA is in a double-stranded or single-stranded form. On the other hand, with increasing added salt, the characteristic length scale of the low-frequency mode diminishes at low DNA concentrations probably due to dynamical formation of denaturation bubbles and/or fraying in the vicinity of DNA denaturation threshold.

aqueous biopolymers ; DNA ; length scales ; dielectric spectroscopy

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