Open AccessThe attachment of amino fragment to purine: inner‐shell structures and spectra
Author(s) -
Saha Saumitra,
Wang Feng,
MacNaughton Janay B.,
Moewes Alex,
Chong Denalo P.
Publication year - 2008
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s0909049508000630
Subject(s) - chemistry , purine , reactivity (psychology) , electrophile , stereochemistry , density functional theory , spectral line , crystallography , computational chemistry , enzyme , biochemistry , medicine , physics , alternative medicine , pathology , astronomy , catalysis
The impact of the amino fragment (–NH 2 ) attachment on the inner‐shell structures and spectra of unsubstituted purine and the purine ring of adenine are studied. Density functional theory calculations, using the LB94/TZ2P//B3LYP/TZVP model, reveal significant site‐dependent electronic structural changes in the inner shell of the species. A condensed Fukui function indicates that all of the N and C sites, except for N (1) and C (5) , demonstrate significant electrophilic reactivity ( f − > 0.5 in | e |) in the unsubstituted purine. Once the amino fragment binds to the C (6) position of purine to form adenine, the electrophilic reactivity of these N and C sites is greatly reduced. As expected, the C (6) position experiences substantial changes in energy and charge transfer, owing to the formation of the C—NH 2 bond in adenine. The present study reveals that the N1 s spectra of adenine inherit the N1 s spectra of the unsubstituted purine, whereas the C1 s spectra experience significant changes although purine and adenine have geometrically similar carbon frames. The findings also indicate that the attachment of the NH 2 fragment to purine exhibits deeply rooted influences to the inner‐shell structures of DNA/RNA bases. The present study suggests that some fragment‐based methods may not be applicable to spectral analyses in the inner shell.