Determination of the kinetics of deuteration of DNA. RNA hybrids by ultraviolet spectroscopy
The kinetics of the hydrogen-deuterium exchange reactions of poly(dA).poly(rU) and poly(rA).poly(dT) has been examined, at pH 7.0 and at various temperatures in the 15-35 degrees C range, by stopped-flow ultraviolet spectrophotometry. For comparison, the deuteration kinetics of poly(d(A-T)).poly(d(A-T)) and poly(rA).poly(rU) has been reexamined. At 20 degrees C, the imino deuteration (NH----ND) rates of the two hybrid duplexes were found to be 1.5 and 1.8 s-1, respectively. These are nearly equal to the imino deuteration rates of poly(d(A-T)).poly(d(A-T)) (1.1 s-1) and poly(rA).poly(rU) (1.5 s-1) but appreciably higher than that of poly(dA).poly(dT) (0.35 s-1). It has been suggested that a DNA.RNA hybrid, an RNA duplex, and the AT-alternating DNA duplex have in general higher base-pair-opening reaction rates than the ordinary DNA duplex. The amino deuteration (NH2----ND2) rates, on the other hand, have been found to be 0.25, 0.28, and 0.33 s-1, respectively, for poly(dA).poly(rU), poly(rA).poly(dT), and poly(d(A-T)).poly(d(A-T)), at 20 degrees C. These are appreciably higher than that for poly(rA).poly(rU) (0.10 s-1). In general, the equilibrium constants (K) of the base-pair opening are considered to be greatest for the DNA.RNA hybrid duplex (0.05 at 20 degrees C), second greatest for the RNA duplex (0.02 at 20 degrees C), and smallest for the DNA duplex (0.005 at 20 degrees C), although the AT-alternating DNA duplex has an exceptionally great K (0.07 at 20 degrees C). From the temperature effect on the K value, the enthalpy of the base-pair opening was estimated to be 3.0 kcal/mol for the DNA.RNA hybrid duplex.
- Research Organization:
- Univ. of Tokyo, Japan
- OSTI ID:
- 5964558
- Journal Information:
- Biochemistry; (United States), Journal Name: Biochemistry; (United States) Vol. 18; ISSN BICHA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ABSORPTION SPECTROSCOPY
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DEUTERATION
DEUTERIUM
DNA
ELEMENTS
HYDROGEN
HYDROGEN ISOTOPES
ISOTOPES
ISOTOPIC EXCHANGE
KINETICS
LIGHT NUCLEI
NONMETALS
NUCLEI
NUCLEIC ACIDS
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
REACTION KINETICS
RNA
SPECTRA
SPECTROSCOPY
STABLE ISOTOPES
THERMODYNAMICS
ULTRAVIOLET SPECTRA