The chemical shift difference (delta[13C(beta)]-delta[13C(gamma)]) is a reference-independent indicator of the Xaa-Pro peptide bond conformation. Based on a statistical analysis of the 13C chemical shifts of 1,033 prolines from 304 proteins deposited in the BioMagRes database, a software tool was created to predict the probabilities for cis or trans conformations of Xaa-Pro peptide bonds. Using...

Isotropic 13C chemical shifts of the ribose sugar in model RNA nucleosides are calculated using SCF and DFT-GIAO ab initio methods for different combinations of ribose sugar pucker, exocyclic torsion angle, and glycosidic torsion angle. Idealized conformations were obtained using structures that were fully optimized by ab initio DFT methods starting with averaged parameters from a collection of...

Tentative assignment for each carbon resonance in the natural abundance high resolution carbon-13 nuclear magnetic resonance Fourier transform spectrum at 25.2 MHz of the biologically active cyclic octapeptides, synthetic oxytocin (43 carbons) and lysine-vasopressin (46 carbons) and the cyclic dodecapeptide bacitracin (66 carbons) has been made using a number of different techniques. The 1% ass...

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 54D<...

Deuterium isotope effects on ¹³C-NMR chemical shifts are investigated in a series of 10-hydroxybenzo[h]quinolines (HBQ's) The OH proton is deuteriated. The isotope effects on ¹³C chemical shifts in these hydrogen bonded systems are rather unusual. The formal four-bond effects are found to be negative, indicating transmission via the hydrogen bond. In addition unusual long-range effects are seen...

The genus Aristolochia,an important source of physiologically active compounds that belong to different chemical classes, is the subject of research in numerous pharmacological and chemical studies. This genus contains a large number of terpenoid compounds, particularly diterpenes. This work presents a compilation of the 13C-NMR data of 57 diterpenoids described between 1981 and 2007 which were...

Complexation characteristics of 1,4,7,10,13,16-hexaoxacyclooctadecane (18-crown-6, 18C6) with Li+ and K+ in a hydrophobic ionic liquid of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide under dry and humid conditions at 298.2 K were studied by 1H and 13C NMR chemical shifts. The comparison of the 1H and 13C chemical shifts of 18C6 molecule between the dry and humid IL solutions w...