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Rapid kinetic studies on the conformation of single‐stranded DNA
Author(s) -
Walz Frederick G.
Publication year - 1972
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.1972.360111115
Subject(s) - chemistry , kinetics , dna , relaxation (psychology) , kinetic energy , crystallography , stacking , ion , temperature jump , biochemistry , organic chemistry , psychology , social psychology , physics , quantum mechanics
The conformational states of single‐stranded calf thymus DNA were probed using the tmeperature‐jump kinetic technique. A rapid decrease in transmission at 260 nm followed by a broad relaxation spectrum was observed for single‐stranded DNA at 0.15M KCI, pH, 6.5 at 25°. The relaxation spectrum could also be detected as a hydrogen ion release. Sonicated samples of 103,000 daltons showed identical relaxation kinetics as unsonicated samples. The relaxation kinetics were studied as a function of temperature, pH, and salt concentration and could be interpreted as representing the melting of short, isolated folded segments. The rapid process that could not be kinetically resolved is interpreted as single‐strand unstacking. Upon the addition of excess MgCl 2 at pH 7.0, a hydrogen ion release from single‐stranded DNA was observed that was 3.5 times greater than that observed for a comparable sample of native DNA. Evidence is presented which indicates that charge‐pairs exist in folded segments that are A‐T rich. There was no kinetic evidence of structures in single‐stranded DNA other than single‐stranded stacking and short isolated folded regions.