A 13C T1 study of conformational and molecular mobility of mono‐ and difucosyllactosesfv

Overall and internal motions of lactose Galβ(1 → 4)Glcα and its three fucosylated derivatives Fucα(1 → 2)Galβ(1 → 4)Glcα, Galβ(1 → 4) [Fucα(1 → 3)] Glcα and Fucα(1 → 2)Galβ(1 → 4) [Fucα(1 → 3)] Glcα were investigated in Me2SO‐d6 using the spin–lattice relaxation times of 13C nuclei, T1(13C), measured at 8.5 and 11.7T. The relaxation data of the ring carbons in lactose and the lactosyl core of its derivatives were well described by the axially symmetric motion of the molecule. However, the interpretation of the T1(13C) of ring carbons in fucose residues required the assumption of a conformational mobility about the appropriate glycosidic bonds. For this purpose, a bistable, jump model of internal motion with a varying angle between the rotation axis and the symmetry axis of the overall tumbling was developed. The internal rotation of hydroxymethyl groups in Glc and Gal residues was also analysed quantitatively; the rotation in Glc was found to be slower than that in Gal. The internal rotation of methyl groups in fucoses undergoing a complex motion was interpreted semi‐quantitatively

Factors improving the accuracy of determination of 15N relaxation parameters in proteins.

A number of factors at all stages of data processing which affect the accuracy of determination of 15N relaxation parameters in 15N-labeled proteins is discussed. Methods which allow to improve accuracy of the determined parameters are presented using data obtained for Cucurbita maxima trypsin inhibitor.</jats:p

Studies on the mechanism of mutagenicity and genotoxicity induced by dihydralazine.

Dihydralazine was found to be mutagenic towards S. typhimurium TA1537, TA97, TA1538 and TA98 and genotoxic towards E. coli PQ37. Using the nitro blue tetrazolium reduction method we have found that dihydralazine can generate active oxygen species. The possible role of active oxygen species in mutagenicity (Ames test) and genotoxicity (SOS Chromotest) of dihydralazine was studied by testing the influence of the different active oxygen species scavengers on these two processes. Of the active oxygen scavengers tested, only superoxide dismutase suppressed partially the mutagenic and genotoxic activity of dihydralazine. This result seems to indicate that superoxide anion play a role in these two biological events.</jats:p

Identification of constituent sugar residues in oligosaccharides by two‐dimensional spectroscopy

Pure absorption phase‐sensitive shift‐correlated 1H NMR spectra were shown to furnish complete information on chemical shifts, their connectivities (including one‐ and two‐step remote connectivities) and coupling constants for oligosaccharides of considerable complexity. Therefore, a strategy using these spectra as a first step in ab initio structure elucidation of carbohydrates may require less effort and spectrometer time than alternative strategies exploiting J‐resolved, double quantum and relayed coherence transfer spectra. All these methods and also triple quantum filtered spectra were applied in order to compare their merits and to identify the constituent sugar residues of three peracetylated glycosphingolipids, viz. Galα(1–3)Galβ(1–4)GlcNAcβ(1–3)Galβ(1–4)Glcβ(1–1)Cer(Cer=ceramide),Galα(1–3)Galβ(1–4)GlcNAcβ(1–3)[Galα(1–3)Galβ(1–4)GlcNAcβ(1–6)]Galβ(1–4)GlcNAcβ(1–3)Galβ(1–4)Glcβ(1–1)Cer and GalNAcβ(1–3)Galα(1–4)Galβ(1–4)Glcβ(1–1)Cer(globoside)