Recent theoretical developments permit the prediction of 1H, 13C, 15N, and 19F nuclear magnetic resonance chemical shifts in proteins and offer new ways of analyzing secondary and tertiary structure as well as for probing protein electrostatics. For 13C, phi, psi torsion angles dominate shielding for C alpha and C beta, but the addition of hydrogen bonding and electrostatics gives even better a...

Singlet state structures of small, cyclic hydrocarbons which can result from the addition of molecular dicarbon (C2) to ethyne (HC≡CH) or ethene (H2C=CH2) have been calculated (B3LYP/6311+G(d,p) level of theory), and were found to contain carbene centres. Some structures of analogous boranes (replacement of the carbene centers by BH fragments) were also calculated. The computation of NMR parame...

A single-crystal X-ray diffraction structure of a 1:1 cocrystal of two fungicides, namely dithianon (DI) and pyrimethanil (PM), is reported [systematic name: 5,10-dioxo-5H,10H-naphtho[2,3-b][1,4]dithiine-2,3-dicarbonitrile-4,6-dimethyl-N-phenylpyrimidin-2-amine (1/1), C14H4N2O2S2·C12H13N2]. Following an NMR crystallography approach, experimental solid-state magic angle spinning (MAS) NMR spectr...

deuterium substitution on two ortho-substituted-och2-fragments in nitro-benzo-9-crown-3 induces low frequency shifts, positive mndcj, in all 13c nmr resonances which is an indication of the increased shielding in this crown ether. the magnitude of these shifts vary from 15dc7=716 to 54dc3=15 ppb for c7 and c3 cd3cocd3, and c6d6 on mndcj values were investigated. the mndcj values depended more o...

A database of peptide chemical shifts, computed at the density functional level, has been used to develop an algorithm for prediction of 15N and 13C shifts in proteins from their structure; the method is incorporated into a program called SHIFTS (version 4.0). The database was built from the calculated chemical shift patterns of 1335 peptides whose backbone torsion angles are limited to areas o...

Two polymorphs of indomethacin were investigated by 1H MAS and CRAMPS, and 1H-13C CPMAS and HETCOR NMR techniques. The obtained spectra clearly elucidated the structural differences between the polymorphs, especially the different numbers of indomethacin molecules within the crystallographic asymmetric units and the different schemes of hydrogen bonding among the molecules. Known structure of i...

Cross-polarization (CP) magic angle spinning (MAS) 13C NMR spectroscopy has become a routine tool in pharmacy, employed to identify and characterize drugs in the solid phase. 13C CPMAS NMR spectra were recorded for solid hydrocortisone 21-hemisuccinate and suxamethonium chloride. White crystalline substances, such as these two drugs, can be easily distinguished; and solid-state 13NMR spectra of...

The measurement of amide nitrogen 14N quadrupolar coupling by two-dimensional 14N/13C correlation experiment is presented with a natural abundant polypeptide. Directly bonded 14N/13C pairs are correlated through J and residual dipolar coupling under magic-angle spinning using a HMQC-type pulse sequence. The 14N quadrupolar coupling is measured from the isotropic second-order quadrupolar shift o...

A new method for refinement of 3D molecular structures by geometry optimization is presented. Prerequisites are a force field and a very fast procedure for the calculation of chemical shifts in every step of optimization. To the energy, provided by the force field (COSMOS force field), a pseudoenergy, depending on the difference between experimental and calculated chemical shifts, is added. In ...

Pressure-dependent (13)C chemical shifts have been measured for aliphatic carbons in barnase and Protein G. Up to 200 MPa (2 kbar), most shift changes are linear, demonstrating pressure-independent compressibilities. CH(3), CH(2) and CH carbon shifts change on average by +0.23, -0.09 and -0.18 ppm, respectively, due to a combination of bond shortening and changes in bond angles, the latter matc...