Cation-dependence of the self-association behavior of guanylyl-(3'-5')-guanosine.
The aggregation behavior of guanylyl-(3'-5')-guanosine, GpG, in the form of the tetramethylammonium (TMA), Li, Na, and K salts in aqueous solution has been investigated by NMR and FTIR techniques. The salts were prepared by a cation-exchange method. The ability of the cations to induce aggregate formation is TMA+ < Li+ < Na+ < K+, where TMA+ has only a weakly promoting action and K+ has a very strong effect. Three types of aggregates have been observed: (a) small aggregates which are in rapid exchange with respect to the NMR time scale; (b) intermediate-sized aggregates which are slow to exchange; (c) very large aggregates which can only be observed by FTIR. In all cases the aggregated species are held together by base stacking and guanine-guanine hydrogen bonding. A stoichiometry of 2 GpG per K+ has been determined by a 1H NMR titration of TMAGpG with KCl. Models have been proposed for the various-sized species. These include stacked dimers, stacked tetramers (similar to G-tetrads), and species in which K+ ion bridges between phosphates in separate tetramers.
Walmsley
J A
JA
Division of Earth and Physical Sciences, University of Texas, San Antonio 78249.
Schneider
M L
ML
Farmer
P J
PJ
Cave
J R
JR
Toth
C R
CR
Wilson
R M
RM
D002414:Cations, Monovalent / Q000737:chemistry*; D002852:Chromatography, Ion Exchange; D015226:Dinucleoside Phosphates / Q000737:chemistry*; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D000644:Quaternary Ammonium Compounds / Q000737:chemistry
D002414:Cations, Monovalent; D015226:Dinucleoside Phosphates; D000644:Quaternary Ammonium Compounds; C018309:guanylyl-(3'-5')-guanosine; C027917:tetramethylammonium