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N Soffe

Publications and source records attributed to N Soffe.

7 recordsLinked to original sources
PubMed1997

The influence of a scalar-coupled deuterium upon the relaxaton of a 15N Nucleus and its possible exploitation as a probe for side-chain interactions in proteins.

The magnitude of the quadrupole coupling constant (e2Qq/h) of a deuteron is a good probe for hydrogen bonding. In protein structures, hydrogen-bonding interactions between side chains, between side chaings and ligands, and between side chains and solvent are frequently found. An experiment that detects, via scalar coupling, the influence of a deuteron on the 15N nucleus of asparagine or glutamine side chains is presented. The experiment depends upon the resolution of the 1 delta 15 N(D) isotope shifts that allow the various isotopomers and isotopologues to be distinguished when 15N-labeled samples are dissolved in solvent mixtures of H2O/D2O. 15N lineshapes with theoretical simulations that provide estimates for the 2H quadrupole coupling constants are presented. The influence of 15N-2H dipolar-quadrupole cross correlation and the resulting small frequency shifts in the 15N multiplet are resolved in some of the spectra. The experimental data are provided using the free amino acids asparagine and glutamine for which the side chains were isotopically enriched in 15N and the recombinant pair of modules, fibronectin type 1 and epidermal growth factor, (F1-G) of tissue plasminogen activator, which were uniformly isotopically enriched in 15N.

Asparagine↗
PubMed1994

Secondary structure and backbone dynamics of human granulocyte colony-stimulating factor in solution.

The secondary structure and backbone dynamics of the cytokine, human granulocyte colony-stimulating factor (hG-CSF) have been determined by heteronuclear nuclear magnetic resonance (NMR) techniques. Virtually complete NH, C alpha H, C beta H 15N, 13C alpha, and 13C beta assignment of the 175-residue recombinant protein, methionyl-[Cys-17-Ser]-hG-CSF, was achieved by use of three-dimensional (3D) heteronuclear 1H-15N and triple-resonance 1H-15N-13C experiments. Spectra recorded at 750 MHz aided the assignment of severely overlapped regions. The structures of G-CSF from several species have recently been determined by X-ray diffraction [Hill, C. P., Osslund, T. D., & Eisenberg, D. (1993) Proc. Natl. Acad. Sci. U.S.A. 90, 5167-5171; Lovejoy, B., Cascio, D., & Eisenberg, D. (1993) J. Mol. Biol. 234, 640-653]. Like several cytokines, hG-CSF has a four-helix topology (A-D) with overhand loop connections, but with an additional helical segment (A') identified in the connection between helix A and helix B. The solution-state determination of the secondary structure is based on short- and medium-range NOEs, backbone J-couplings, and NH exchange data and is corroborated by 13C alpha secondary shifts. The helices are defined as follows: A, 10-38; A',44-53; B, 71-91; C, 102-123; D, 143-172. The dynamics of the amide backbone resonances, investigated using 1H-15N heteronuclear NMR, indicate a rigid protein core with some increased mobility in the AB loop and more pronounced mobility in the CD loop.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1987

A method for the rapid assignment of 1H NMR spectra of oligosaccharides using homonuclear Hartmann-Hahn spectroscopy.

An NMR method is described, based on coherence transfer in the rotating frame, which allows for the rapid determination of proton resonance assignments in oligosaccharides. The composite one-dimensional spectrum of the oligosaccharide is decomposed into a subset of spectra that are derived from individual monosaccharide residues. Proton resonance assignments can be obtained from these subspectra by inspection of the multiplicities of the component resonances and by spectral simulation. The method is shown to have particular value in the assignment of proton resonances derived from primary sequence branch-point residues, which often have complex spin-coupling patterns. Other advantages of this method over conventional techniques are discussed.

Acetylglucosamine↗
PubMed1985

1H- and 13C-n.m.r. assignments and conformational analysis of some monosaccharide and oligosaccharide substrate-analogues of lysozyme.

The 1H- and 13C-n.m.r. spectra of solutions of GlcNAc, beta-GlcNAc-(1----4)-GlcNAc, and beta-GlcNAc-(1----4)-beta-GlcNAc-(1----4)-GlcNAc in D2O at 50 degrees are interpreted in terms of the conformations, using a combination of 1D- and 2D-n.m.r. spectroscopy and spectra simulation techniques. Two preferred orientations of the hydroxymethyl group were found for each of these saccharides. The conformations have been compared with those found from X-ray crystallographic data and conformational energy calculations.

Animals↗
PubMed1985

Solution structure of mitochondrial cytochrome c. I. 1H nuclear magnetic resonance of ferricytochrome c.

The 1H nuclear magnetic resonance spectra of tuna and horse ferricytochromes c have been investigated and the resonances of all amino acid methyl groups have been assigned to specific absorption lines. The assignment procedure involves principally the comparison of one-dimensional nuclear magnetic resonance spectra from a range of homologous ferricytochromes c and does not require a prior knowledge of the secondary or tertiary protein structure. Of the 49 methyl groups of tuna cytochrome c, the assignment of 33 is made without reference to the X-ray crystal structure. The method should therefore be applicable to other proteins of similar size where X-ray structures are unavailable. The assignments will be used to investigate the structure of cytochrome c in solution.

Amino Acid Sequence↗