Torsional rigidity of positively and negatively supercoiled DNA

Journal Article · Thu Jan 02 23:00:00 EST 1992 · Science (Washington, D.C.); (United States)

DOI:https://doi.org/10.1126/science.1553534· OSTI ID:7045169

Selvin, P R; Cook, D N; Pon, N G; Klein, M P; Hearst, J E ^[1]; Bauer, W R ^[2]

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1. Lawrence Berkeley Lab., CA (United States)
2. State Univ. of New York, Stony Brook (United States)

Time-correlated single-photon counting of intercalated ethidium bromide was used to measure the torsion constants of positively supercoiled, relaxed, and negatively supercoiled pBR322 DNA, which range in superhelix density from +0.042 to {minus}0.123. DNA behaves as coupled, nonlinear torsional pendulums under superhelical stress, and the anharmonic term in the Hamiltonian is approximately 15 percent for root-mean-square fluctuations in twist at room temperature. At the level of secondary structure, positively supercoiled DNA is significantly more flexible than negatively supercoiled DNA. These results exclude certain models that account for differential binding affinity of proteins to positively and negatively supercoiled DNA.

• DOE Contract Number: AC03-76SF00098
• OSTI ID: 7045169
• Journal Information: Science (Washington, D.C.); (United States), Journal Name: Science (Washington, D.C.); (United States) Vol. 255:5040; ISSN SCIEA; ISSN 0036-8075
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
BINDING ENERGY
CONFORMATIONAL CHANGES
DATA
DENSITY
DNA
ENERGY
EXPERIMENTAL DATA
FUNCTIONS
HAMILTONIAN FUNCTION
INFORMATION
MATHEMATICAL MODELS
NUCLEIC ACIDS
NUMERICAL DATA
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
PROTEINS
RESOLUTION
TIME RESOLUTION
TIMING PROPERTIES
TORSION