The elastic properties of single double-stranded DNA chains of different lengths as measured with optical tweezers

Abstract

Optical tweezers are microscopic tools with extraordinary precision in the determination of the position (±2 nm) of a colloid (diameter: ∼2.0 μm) in 3D-space and in the measurement of small forces in the range between 0.1 and 100 pN (pN=10−12 N). Experiments are reported in which single double-stranded (ds)-DNA chains of different length [2,000 base pairs (bp), 3,000, 4,000, and 6,000 bp] are spanned between two colloidal particles by use of appropriate molecular linkers. For the forces applied (≤40 pN) a fully reversible and well reproducible force–extension dependence is found. The data can be well described by both the worm-like chain model or by an approach developed by R. G. Winkler. For the resulting persistence length, a pronounced dependence on the ionic concentration in the surrounding medium is found.

Diffusion and segmental dynamics of rodlike molecules by fluorescence correlation spectroscopy

“…This leads to what may be called Gaussian model of a semiflexible polymer. 10,[31][32][33][34][35][36][37][38][39][40] There are a number of results confirming the usefulness of such an approach for structural 10,41,42 as well as dynamical properties. 9,14,16,17,20 ͑ii͒ To determine the structural properties of the Kratky-Porod wormlike chain, various approximation schemes have been applied [43][44][45][46][47] and a number of equilibrium properties have been obtained successfully.…”

Single colloid electrophoresis

“…Usually experiments are carried out on colloidal dispersions [4][5][6], but few studies exist where the electrophoretic response of a single isolated colloid is determined [7][8][9][10]. For that optical tweezers are employed, experimental tools having an extraordinary resolution in measuring the position of a colloid and the forces acting on it [11][12][13][14][15].…”

Probabilistic models for damage and self-repair in DNA self-assembly

“…Hence, we simulate lattices ranging in sizes from 200 to 4000 tiles. Force spectroscopy and other methods that can manipulate objects at submicrometre scale tells us that the range of force these structures experience is very small, generally in the 100 s of pN [21]. On the other hand, the threshold distance is a function of the length of sticky end, given that we use the worm-like chain (WLC) model [22].…”