Matrix isolation infrared studies of nucleic acid constituents. 5. Experimental matrix-isolation and theoretical ab initio SCF molecular orbital studies of the infrared spectra of cytosine monomers

1988 ◽  
Vol 110 (25) ◽  
pp. 8319-8330 ◽  
Author(s):  
M. Szczesniak ◽  
K. Szczepaniak ◽  
J. S. Kwiatkowski ◽  
K. KuBulat ◽  
W. B. Person
Keyword(s):  
Nucleic Acid ◽  
Ab Initio ◽  
Molecular Orbital ◽  
Infrared Spectra ◽  
Matrix Isolation ◽  
Infrared Studies

Matrix isolation studies of nucleic acid constituents. 1. Infrared spectra of uracil monomers

1983 ◽  
Vol 105 (19) ◽  
pp. 5969-5976 ◽  
Author(s):  
M. Szczesniak ◽  
M. J. Nowak ◽  
H. Rostkowska ◽  
K. Szczepaniak ◽  
W. B. Person ◽  
...  
Keyword(s):  
Nucleic Acid ◽  
Infrared Spectra ◽  
Matrix Isolation

Infrared spectra of tautomers and rotamers of 9-methylguanine. An experimental and theoretical study

1991 ◽  
Vol 69 (11) ◽  
pp. 1705-1720 ◽  
Author(s):  
K. Szczepaniak ◽  
M. Szczesniak ◽  
W. Szajda ◽  
W. B. Person ◽  
J. Leszczynski
Keyword(s):  
Absorption Spectrum ◽  
Ab Initio ◽  
Infrared Spectra ◽  
Electronic Absorption ◽  
Ab Initio Calculation ◽  
Theoretical Study ◽  
Free Energies ◽  
Argon Matrix ◽  
Tautomeric Forms ◽  
Infrared Studies

Both amino-oxo and amino-hydroxy tautomeric forms of 9-methylguanine have been identified in approximately equal abundance in. infrared studies of these molecules isolated in the hydrophobic environment of an argon matrix at 12 K. The amino-hydroxy tautomer occurs in two different rotamers correlated with the rotation of the OH group. The ratio of concentrations of the two rotamers is sensitive to UV irradiation, and this ratio then relaxes to an equilibrium value after irradiation is stopped. This sensitivity allows us to separate the experimental spectra related to the oxo tautomer and to each of the rotamers of the hydroxy tautomer. The relative concentrations of the amino-oxo and amino-hydroxy tautomers ([a-o]/[a-h] = K(o-h) = 1.0 ± 0.3) and of the two rotamers (K(h1-h2) = 0.31 ± 0.10 in an argon matrix at 12 K and about 30 ± 15 in the vapor at 470 K) are estimated from the observed relative infrared absorbances. From these relative concentrations the differences between the free energies of the tautomers (ΔG470 (o-h) = 0 ± 0.5 kJ mol−1) and of the two rotamers (ΔG(h1-h2) = 0.12 ± 0.03 kJ mol−1 in the argon matrix at 12 K and ΔG470 between +2 and −13 kJ mol−1 in the vapor at 470 K) have been estimated. The electronic absorption spectrum of 9-methylguanine isolated in the argon matrix at 12 K and the effect of brief ultraviolet irradiation on it have also been studied. In an effort to interpret the experimental results, ab initio calculations of the infrared spectra have been made for 9-methylguanine at the 3-21G//3-21G level. Comparison with the experimental spectra is of some help with the assignment of the infrared spectra for the different tautomers. Key words: 9-methylguanine, tautomerism, infrared and ultraviolet spectra, matrix isolation, ab initio calculation.

Combined matrix-isolation FT-IR and ab-initio 6-31++G∗∗ studies on tautomeric properties of nucleic acid bases and simpler model molecules

1997 ◽  
Vol 410-411 ◽  
pp. 397-401
Author(s):  
Linda Houben ◽  
Kristien Schoone ◽  
Johan Smets ◽  
Ludwik Adamowicz ◽  
Guido Maes
Keyword(s):  
Nucleic Acid ◽  
Ab Initio ◽  
Matrix Isolation ◽  
Nucleic Acid Bases ◽  
Ft Ir ◽  
Combined Matrix
Sign in / Sign up

Export Citation Format

Share Document