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Raman spectroscopy study of acid–base and structural properties of 9‐[2‐(phosphonomethoxy)ethyl]adenine in aqueous solutions
Author(s) -
Kopecký Vladimír,
Mojzeš Peter,
Burda Jaroslav V.,
Dostál Lubomír
Publication year - 2002
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.10111
Subject(s) - protonation , chemistry , raman spectroscopy , aqueous solution , moiety , stereochemistry , nucleotide , base (topology) , ionic bonding , crystallography , organic chemistry , ion , biochemistry , mathematical analysis , physics , mathematics , optics , gene
Abstract The acid–base properties of the acyclic antiviral nucleotide analogue 9‐ [2‐(phosphonomethoxy)ethyl] adenine (PMEA) in aqueous solutions are studied by means of Raman spectroscopy in a pH range of 1–11 and compared with the properties of its common adenosine monophosphate counterparts (5′‐AMP, 3′‐AMP, and 2′‐AMP). Factor analysis is used to separate the spectra of pure ionic species (PMEA 2− , HPMEA − , H 2 PMEA, H 3 PMEA + ) in order to determine their abundance, sites of protonation, and corresponding spectroscopic p K a values. The characteristic Raman features of the neutral adenine moiety in PMEA 2− and HPMEA − species resemble those of neutral adenine in the AMPs, whereas significant differences are observed between the Raman spectra of the N1‐protonated adenine of the solute zwitterionic H 2 PMEA and its N1‐protonated AMP counterparts. On the contrary, the spectrum of crystalline H 2 PMEA, adopting an “anti‐like” conformation, is found to be similar to the N1‐protonated AMPs in solution. To explain peculiar Raman features a “syn‐like” conformation is suggested for N1‐protonated PMEA species in aqueous solutions instead of an anti‐like one adopted by H 2 PMEA in crystals or by common AMPs in aqueous solutions. A physical mechanism of the anti‐like to syn‐like conformational transition of the solute PMEA that is due to adenine protonation and the flexibility of the (phosphonomethoxy)ethyl group is proposed and discussed. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 67: 285–288, 2002