The elastic properties ofsingledouble-stranded DNA chains of different lengths as measured with optical tweezers.
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=10-12N). Experiments are reported in whichsingledouble-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.
Institut für Biochemie, Universität Leipzig, Leipzig, Germany.
M
M
Salomo
K
K
Kegler
C
C
Gutsche
M
M
Struhalla
J
J
Reinmuth
W
W
Skokow
U
U
Hahn
F
F
Kremer
Optical tweezers; Single polymers; Stretching