Two-dimensional nuclear magnetic resonance (n.m.r.) spectroscopy and a variety of computational techniques have been used to generate three-dimensional structures of the two DNA duplexes d(CGCCTAATCG) and d(CGTCACGCGC). The central six base-pairs in these two decamers contain all ten dinucleotide pairs in DNA and thus, represent a model system for investigating how the local structure of DNA va...

Pyruvate kinase binds one adenosine 5'-triphosphate (ATP) molecule at its active site and another at an ancillary site on each subunit. In order to determine the conformation of ATP bound at these sites, proton transferred two-dimensional nuclear Overhauser effect spectroscopy (TRNOESY) measurements were made at 500 MHz and 10 degrees C for several mixing times in the range 40-200 ms. The NOE v...

The conformation of MgATP bound at the active site of Salmonella typhimurium 5-phospho-alpha-D-ribose 1-diphosphate synthetase (PRibPP synthetase) has been investigated by two-dimensional transferred-NOE spectroscopy (TRNOESY). Inter-proton NOEs of the ligand were measured in the presence of the protein at several mixing times in the range of 40-300 ms at 500 MHz and 10 degrees C. Measurements ...

The conformations of the adenosine moiety of MgADP and MgATP bound to rabbit muscle creatine kinase were investigated by two-dimensional transferred nuclear Overhauser effect spectroscopy (TRNOESY). The effects arising from adventitious binding of the ligands to the enzyme on the measurements were delineated. It was shown that, with sample protocols typically used thus far with the TRNOE method...

Consistent force field caiculations have been used to calculate the variation of energy along the pseudorotationai paths of ribose and deoxyribose rings. This energy changes by only 10.5 kcalimol as the ring pucker changes from C3’-endo to C2’-endo. Therefore, the torsion angle 4’ of the sugar-phosphate backbone of nucleic acids is more flexible than a normal C-C single-bond torsion angle and c...

The lithium-tin exchange, a metathesis reaction used for the preparation of organolithium reagents, proceeds by way of intermediate pentorgano "ate" complexes. Under suitable conditions these complexes can be observed spectroscopically. The formation constants of the complexes are dramatically increased by polar coordinating solvents such as THF and HMPA. The "ate" complexes have trigonal bipyr...

Conformational properties of N-aryl-1-azacyclooctan-5- ones with a p-methyl, m-methyl, and p-methoxy group as a substituent have been studied by 1H-NMR, 13C-NMR and IR spectroscopies. Transannular interaction of the two functional groups have been examined from the ring inversion barriers and the carbonyl vibrational frequencies with reference to the corresponding data...

BACKGROUND The advent of combinatorial chemistry has revived the interest in five-membered heterocyclic rings as scaffolds in pharmaceutical research. They are also the target of modifications in nucleic acid chemistry. Hence, the characterization of their conformational features is of considerable interest. This can be accomplished from the analysis of the 3J(HH) scalar coupling constants. R...

The electronic structure of some idealized PH5 geometries of D3h, C4v, and C, symmetries is analyzed. Each geometry is characterized by a low-lying nodeless orbital, three singly noded orbitals close in energy, and a high-lying doubly noded nonbonding orbital. The latter orbital is the only one significantly stabilized by the inclusion of 3d orbitals in the P basis set and also determines the r...