摘要:

AbstractFor‐Thp‐Leu‐ΔzPhe‐OMe (2), an analogue of the chemotactic tripeptide For‐Met‐Leu‐Phe‐OMe, containing 4‐aminotetrahydrothiopyran‐4‐carboxylic acid (Thp) and (Z)‐2,3‐didehydrophenylalanine (ΔzPhe) as achiral, conformationally restricted mimics of Met and Phe, respectively, has been synthesized. In the crystal the new formyltripeptide adopts a type I β‐turn conformation stabilized by a weak H bond between the formylic oxygen and the ΔzPhe NH.1H‐nmr analysis based on NH solvent accessibility and nuclear Overhauser effect experiments suggests that the β‐turn is not preferred in CDCl3solution where a γ‐turn, centered at the Thp residue, prevails. The biological activity of2has been determined on human neutrophils and compared to that of previously studied analogues. The tripeptide2is practically unable to elicit superoxide anion production and lysozyme release, while slight, but not statistically significant activity was induced in chemotaxis. The role of the orientation of the aromatic ring with respect to the backbone adjacent atoms is

ISSN:0006-3525    

DOI:10.1002/bip.360341002

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe effects of heating temperature on gel properties and conformational changes were investigated in glycinin and β‐conglycinin gels using Theological and Fourier transform ir (FTIR) methods. Solutions of 15 wt % glycinin or β‐conglycinin in 35 mMphosphate buffer at pH 7.6 were heated at various temperatures for 30 min and rheological properties were measured at 20°C. The storage modulusG′ as a function of frequency changed from a monotonical decrease with decreasing frequency to a plateau in the range from 0.0018 to 40 Hz by heating at temperatures higher than 80°C for glycinin and 65°C for β‐conglycinin. A band at 1618 cm−1(associated with the β‐sheet structure) on ir spectra increased with the formation of heat‐induced gels. The value of the storage modulusG′ correlated well with the increase in absorbance at 1618 cm−1. These results suggest that the formation of a β‐sheet structure may be closely related to the value of the storage modulusG′ for heat‐induced gels in soybean proteins and that heat‐induced gels of glycinin and β‐conglycinin are formed by cross‐links with intermolecular β‐shee

ISSN:0006-3525    

DOI:10.1002/bip.360341003

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe receptor‐like recognition behavior of the GM1 ganglioside has been examined theoretically in terms of conformational and binding properties. Modeling was conducted at two limiting conditions of dielectric constant in order to determine sensitivity to scaling of coulombic interactions. A systematic conformational search of the GM1 oligosaccharide in the absence of explicit solvent molecules indicates that there are many inherently low energy conformational states. Up to 39 conformers were found with energies within 5 kcal/mole of the observed lowest energy conformer. Using a dielectric constant of 80, a systematic search of sodium binding sites on GM1 identified 37 sites where a positively charged group might bind, while at least 12 sites were identified using a dielectric constant of 1. Notably important binding sites include pockets formed by the proximity of glycosidic (O1), sugar ring (O5), and exocyclic methylene hydroxyl (OH6) oxygens on the sugars. The oxygens of acetyl groups attached to sugars also contribute to the binding. Direct coordination with the carboxylate of sialic acid is not a prerequisite for cationic binding. The large number of conformational states and binding sites for the GM1 oligosaccharide are paradoxical to the specific recognition behavior of the molecule. This paradox can be explained in terms of bridging ligands, which are found from molecular dynamics to be capable of stabilizing molecular conformation. © 1994 John Wiley&Sons, I

ISSN:0006-3525    

DOI:10.1002/bip.360341004

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe coaggregation ofStreptococcus mitisstrain J22 in the early stages of dental plaque formation has been shown to result from interaction of cell wall polysaccharides with lectins on the surface of other oral bacterial species. This bacterium was grown in a medium containing13C as the sole carbon source. We have isolated the lectin receptor polysaccharide from this strain with full enrichment in13C and have determined a number of two‐bond and three‐bond13C‐1H coupling constants from measurements of the offsets in two‐dimensional homonuclear nmr spectra [exclusive correlated spectroscopy (E‐COSY) method]. A scheme for reliable extraction of these coupling constants from homonuclear Hartmann‐Hahn and nuclear Overhauser effect spectroscopy spectra is tested in model compounds. We interpret the three‐bond coupling across the glycosidic linkage in terms of dihedral angles in order to provide conformational information to supplement molecular modeling and nuclear Overhauser effect data. We show that the E‐COSY method works well even for coupling constants smaller than the nmr line width and that a number of the3JCHacross the glycosidic linkage are in the range of 1–2 Hz, which is much smaller than many previously reported values. © 1994 Jo

ISSN:0006-3525    

DOI:10.1002/bip.360341005

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractRecombinant murine amelogenins M179 and M166 were expressed inEscherichia coliand purified. The aggregation properties of these amelogenins have been investigated in aqueous solutions as well as acetonitrile‐containing solutions using dynamic light scattering. Dynamic light scattering provides direct measurement of the translational diffusion coefficient and hydrodynamic radius, and of an estimate of the molecular weight. Polydispersity and statistical parameters of how to interpret the analysis are also provided. Amelogenin aggregation was examined in solutions of a range of pH, ionic strengths, and protein concentrations. It was shown that at pH 7.8–8 and ionic strength of 0.02–0.05Mthe M179 molecules form monodispersed aggregates with hydrodynamic radii ranging from 15 to 19 nm. Analysis of hydrodynamic radii and size distribution of M179 aggregates in acetonitrile‐containing solvents compared to that in aqueous solutions indicated a primary role for hydrophobic interactions in the association process of amelogenin molecules to form aggregates. Comparison between the aggregates formed by M179 and M166, which lacks the hydrophilic carboxy‐terminal 13 residue sequence of M179, suggested that the self‐assembly of amelogenin molecules to form stable and monodisperse aggregates requires the presence of the hydrophilic carboxy‐terminal sequence of M179. © 1994 John W

ISSN:0006-3525    

DOI:10.1002/bip.360341006

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractDNA molecules ranging in size from 1 to 630 kilobase pair and intercalated with either ethidium bromide (EtBr) or propidium iodide (PI) were electrophoresed in 1% agarose at four different electric field strengths. The extent of intercalation of EtBr under the conditions of our electrophoresis experiments was determined by a spectroscopic technique, whereas the extent of intercalation of PI was inferred from previous studies. The effects of the increase in DNA contour length and the concomitant decrease of linear charge density were separated based on our analysis of the mobility data. We conclude that the main factor responsible for the reduced electrophoretic mobility of intercalated DNA is the diminished linear charge density and not the increased contour length. © 1994 John Wiley&Sons, Inc

ISSN:0006-3525    

DOI:10.1002/bip.360341007

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe divalent cation‐induced protein folding properties of the template macromolecule, bovine dentine phosphophoryn (BDPP), have been examined by1H/31P/13C/113Cd‐nmr spectroscopy. Cd(II) was employed, exploiting the sensitivity of113Cd‐nmr to ligand‐binding interactions and kinetics. Cation binding was studied over the stoichiometric range of 0–50 : 1 Cd(II) : protein (mole ratio), well below the range of Cd(II) concentration required to induce protein precipitation. The stepwise titration of divalent cation‐depleted phosphophoryn at pH 7.2 in H2O/D2O with113CdCl2revealed that (PSer)n, (PSerAsp)n, and (Asp)npolyelectrolyte cation‐binding domains undergo two major transitions in their secondary and tertiary structures: the first transition, occurring between 1 : 10 and 1 : 1 Cd(II) : protein stoichiometry, and the second, between 10 : 1 and 50 : 1. By monitoring the amide NH intensities,31P‐nmr chemical shift, and13C Asp‐C, resonances, it was concluded that Cd(II) ions exhibit a binding‐site preference for polyelectrolyte cation‐binding domains, in the order\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm (PSer)}_n {\rm > (PSerAsp)}_n {\rm > (Asp)}_n $$\end{document}This preference correlates with the degree of negative charge density for each sequence motif. Accompanying the backbone conformational transitions at the polyelectrolyte regions were conformational transitions in the flanking hinge domains, indicating that the hinge domains participate in the folding of the phosphophoryn molecule as divalent cation binding occurs at the polyelectrolyte domains.We were unsuccessful in detecting phosphophoryn‐bound Cd (11) species by113Cd‐nmr because of chemical exchange modulation. However, using a smaller 21‐residue peptide mimetic of phosphophoryn, we have observed three stoichiometric‐dependent113Cd resonances that differ in terms of the oxoanion coordination number. Our observation of multiple Cd(II) species in the presence of the peptide supports our contention that Cd(II) has many chemically distinct coordination sites on phosphophoryn, each in multiple equilibria with H2O, Cl−, and side‐chain oxoa

ISSN:0006-3525    

DOI:10.1002/bip.360341008

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractInfrared and Raman spectra have been obtained of crystalline glutathione and its deuterated derivative and interpreted by normal mode analysis. The force field consisted of our empirical force fields for the peptide group and NH 3+3and CO 2−end groups, plus our ab initio force fields for the CH2SH and CH2COOH moieties. Observed bands are reproduced with an average error of 5 cm−1, demonstrating that the vibrational spectrum of such a complex molecule can be understood in great depth. © 1994 John Wiley&S

ISSN:0006-3525    

DOI:10.1002/bip.360341009

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe optical rotation of methyl 3‐O‐(α‐D‐mannopyranosyl)‐α‐D‐mannopyranoside is calculated semiempirically as a function of the linkage dihedral angles ϕ (H1‐C1‐O1‐C3′) and ψ (C1‐O1‐C3′‐H3′). Comparison with the observed optical rotation in aqueous solution indicates the existence of at least two conformers in solution, which implies a degree of linkage flexibility. The result is in agreement with some, but not all, calculated potential energy surfaces, and with recently published nm

ISSN:0006-3525    

DOI:10.1002/bip.360341010

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe optical rotation of methyl 2‐O‐(α‐D‐mannopyranosyl)‐α‐D‐mannopyranoside is calculated semiempirically as a function of the linkage dihedral angles ϕ (H1‐C1‐O1‐C2′) and ψ (C1‐O1‐C2′‐H2′). Although the rotation calculated for the global energy minimum conformation found in several rigid‐residue modeling calculations (ϕ,ψ = −40°,−20°) is in good agreement with the observed solution rotation, the observed rotation is also compatible with the limited flexibility inferred from more recent relaxed residue modeling calculations on a structurally related rham

ISSN:0006-3525    

DOI:10.1002/bip.360341011

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY