Structural effects on the circular dichroism of ethidium-nucleic acid complexes

Technical Report · Wed Apr 01 04:00:00 EST 1981

OSTI ID:6412279

Dahl, K S

Binding of the frameshift mutagen ethidium biomide to dinucleoside phosphates (dimers) of different base sequences was studied by optical methods, notably uv-visible spectroscopy, circular dichroism (CD), and fluorescence detected circular dichroism (FDCD). The ethidium ion intercalated between the base pairs of the minihelix formed by the complementary dimers; the stoichiometry of the complex was 2:1 dimer:dye. Equilibrium constants for complex formation showed a general preference for dye binding to complementary sequences in the order: Py(3'-5')Pu > Pu(3'-5')Pu identical to Py(3'-5')Py > Pu(3'-5')Py where Py = a pyrimidine base and Pu = a purine base. Complexes with ribodinucleoside phosphates had larger formation constants than their deoxyribo- analogues. A study of ethidium ion binding to dCA/sub 5/G + dCT/sub 5/G tested for any site preference of dye binding and for any correspondence between the dimer:dye FDCD spectra and oligomer:dye FDCD spectra. Ethidium ion binding and optical activity in complexes with calf thymus DNA were studied as a function of NaCl concentration. The binding constant was dependent upon salt concentration, increasing as the ionic strength decreased. The magnitude of the induced Cd band at 307 nm also increased as the ionic strength decreased.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6412279
• Report Number(s): LBL-12655; ON: DE81023086
• Country of Publication: United States
• Language: English

Related Subjects

550200* -- Biochemistry
59 BASIC BIOLOGICAL SCIENCES
ABSORPTION SPECTROSCOPY
ACRIDINES
AZINES
BIOCHEMICAL REACTION KINETICS
BROMIDES
BROMINE COMPOUNDS
CHEMICAL BONDS
DATA
DICHROISM
DNA
DYES
EXPERIMENTAL DATA
HALIDES
HALOGEN COMPOUNDS
HETEROCYCLIC COMPOUNDS
IMINES
INFORMATION
KINETICS
MUTAGENS
NUCLEIC ACIDS
NUCLEOSIDES
NUCLEOTIDES
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
OXYGEN COMPOUNDS
PHOSPHATES
PHOSPHORUS COMPOUNDS
PYRIDINES
REACTION KINETICS
RIBOSIDES
SPECTRA
SPECTROSCOPY
ULTRAVIOLET SPECTRA