guanosine-monophosphate and tetramethylammonium

The (31)P NMR spectra of (TMA)(2)(5'-GMP), where TMA is [(CH(3))(4)N](+) and 5'-GMP is guanosine 5'-monophosphate, and K(2)(5'-GMP), containing various amounts of KCl or TMACl, have been obtained at 2 degrees C. Variable-temperature spectra have also been obtained for K(2)(5'-GMP). The TMA(+) ion serves to neutralize the charge on the dianionic 5'-GMP and permits the added K(+) to bond preferentially in structure-forming sites. (1)H NMR spectra (one- and two-dimensional) have been obtained for K(2)(5'-GMP) and used to assign the proton resonances in the self-associated structures and determine that all residues have the anti glycosidic conformation. The (31)P and (1)H NMR spectra are very complex and indicate the presence of a large number of molecular environments and a structural variation dependent upon the mole ratio of 5'-GMP to K(+). A new model for the solution structure is proposed in which the 5'-GMP forms a pseudo-four-stranded helix with guanine-guanine hydrogen bonding forming a continuous helical strand, rather than the usual planar G-tetrad structure. The guanine-guanine hydrogen bonding sites are the same as that found in a G-tetrad. The K(+) ions would be located in the center of the helix and bonding to the carbonyl oxygens. They are interacting with the phosphates as well. Integration data from the largest sized species give an estimate of 14.3 +/- 1.1 residues in a helical structure.

Topics: Cations, Monovalent; Guanosine Monophosphate; Macromolecular Substances; Models, Molecular; Nuclear Magnetic Resonance, Biomolecular; Nucleic Acid Conformation; Phosphorus Radioisotopes; Potassium; Protons; Quaternary Ammonium Compounds; Sodium; Solutions; Thermodynamics

Proton NMR line broadening methods were used to determine the rates of amino proton exchange for disordered 2'- and 5' - GMP dianions in aqueous solutions containing tetramethylammonium (TMA+) cations. Replacing TMA+ with Na+ does not substantially alter the exchange rates, provided that H-bonded, Na(+)-directed tetramer structures are absent. Activation enthalpies (kcal/mol) and entropies (eu) for 2'-GMP are: delta H not equal to = 18.5 +/- 1.3, delta S not equal to = 9.6 +/- 4.2 for TMA+ salt at pH 8.10, and delta H not equal to = 14.7 +/- 2.6, delta S not equal to = -3.7 +/- 8.0 for the Na+ salt at pH 8.11. Extrapolated values of pseudo first-order rate constants at 25 degrees C are in the range of k = 1-10 sec-1. At suitable concentrations and temperatures, the Na+ salts of both 2'- and 5' - GMP formed stacked and unstacked tetramer units. Relative to the exchange kinetics observed for the disordered nucleotide, the exchange process in the tetramer units was catalyzed in half the amino protons and inhibited in the other half. The catalytic process (k > 10(3) sec-1) has been attributed to amino protons not involved in interbase H-bonding, where as the inhibited process (k < 10(-1) sec-1) was assigned to those protons which do form such bonds. The structure-catalyzed process in both the stacked and unstacked tetramers was manifested by a loss of NMR amino proton intensity due to weighted time-averaging with the resonance for bulk water. A bridging water molecule between an amino proton and a phosphate on an adjacent nucleotide in the tetramer unit may provide a mechanistic pathway for the structure-catalyzed process.

Topics: Guanosine Monophosphate; Hydrogen Bonding; Kinetics; Magnetic Resonance Spectroscopy; Molecular Structure; Protons; Quaternary Ammonium Compounds; Sodium; Solutions; Water

The tetramethylammonium salt of guanylyl-(3'-5')-guanosine has been prepared by a cation-exchange technique and it has been found that the tetramethylammonium ion drastically reduces the self-association of GpG in solution. This has allowed the characterization of GpG by FTIR and 1-D and 2-D NMR spectroscopy. A complete, well-resolved 1H NMR spectrum in D2O has been obtained and all resonances have been assigned. A weak, essentially non-cooperative intermolecular association is observed in solution (15-20 mM) below 40 degrees C. The association occurs via base stacking and base-base hydrogen bonding.

Topics: Chemical Phenomena; Chemistry; Dinucleoside Phosphates; Guanine Nucleotides; Guanosine; Guanosine Monophosphate; Magnetic Resonance Spectroscopy; Quaternary Ammonium Compounds; Salts; Spectrophotometry, Infrared; Temperature

Topics: Adenosine Monophosphate; Chromatography, High Pressure Liquid; Cytidine Monophosphate; Guanosine Monophosphate; Indicators and Reagents; Inosine Monophosphate; Quaternary Ammonium Compounds; Ribonucleotides; Solvents; Tetraethylammonium; Tetraethylammonium Compounds; Uridine Monophosphate; Xanthine; Xanthines