摘要:

AbstractWe report dynamic light scattering measurements over a wide range of scattering vectors for fractionated samples of porcine submaxillary mucin (PSM) glycoproteins in two different solvents: 0.1MNaCl, and 6MGdnHCl. The relaxation spectrum has been successfully resolved into a slow mode corresponding to pure translational diffusion and a fast mode containing information on the relaxation times for intramolecular motion. Analysis of the slow mode permits a light scattering evaluation of the polydispersity of these high molecular weight mucin glycoprotein fractions. Determination of the longest intramolecular relaxation times τ1shows that these are much longer for the PSM fractions in 0.1MNaCl compared to 6MGdnHCl. These data are consistent with earlier studies showing that the chain conformation is the same in both solvents, but that in 0.1MNaCl, the PSM glycoprotein undergoes a self‐association process that is end‐to‐end in nature. Since the τ1value is intimately related to the viscoelastic behavior of PSM solutions and gels, it is interesting to speculate that the end‐to‐end association process may be physiologicall

ISSN:0006-3525    

DOI:10.1002/bip.360280402

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe effect of concanavalin A (Con A) on the thermotropic behavior of positively charged, glycosyl‐free lipids and their mixtures with zwitterionic lipids was investigated by differential scanning calorimetry.The gel to liquid‐crystal phase transition enthalpy of pure dipalmitoylcholine (DPC) was found to be significantly increased in the presence of Con A (ΔH= 31.2 and 42.5 KJ mol−1lipid in the presence and in absence of Con A, respectively). Addition of the lectin to DPC liposomes, furthermore, induces the appearance of a new phase transition centered at 320 K. These results are interpretable by a partial hydrophobic interdigitation of the lectin molecule into the liposomal bilayer.The effect of Con A on the phase behavior of three 2:1 mixtures of zwitterionic and of positively charged lipids was also investigated. Phase diagrams of the systems dipalmitoylphosphatidylcholine‐dihydrosphingosine (DPPC‐DHS), sphingomyelin‐dipalmitoylcholine (SPM‐DPC), and dimyristoylphosphatidylcholine‐dipalmitoylcholine (DMPC‐DPC) are presented. In lipid mixtures of limited miscibility (DPPC‐DHS and SPM‐DPC), Con A induces pronounced phase‐separation effects. These effects are attributable to a direct hydrophobic interaction of the lectin with the liposomal bilayer and do not require the presence of specific receptor groups.The possible relationship between lectin‐induced phase separations in the lipid matrix of biomembranes, and the observed changes in membrane permeability, membranal enzymatic activities,

ISSN:0006-3525    

DOI:10.1002/bip.360280403

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

年代:1989

数据来源: WILEY

摘要:

AbstractTwo‐dimensional nuclear Overhauser enhancement (2D NOESY) data are reported for the polypentapeptide of elastin, poly(VPGVG), and the cyclopentadecapeptide, cyclo(VPGVG)3. In both, the repeating type II Pro2‐Gly3β‐turn can be derived from the NOE data, providing confirmation of many previous studies. In addition, other through‐space connectivities are detailed that also compare favorably with previously determined crystal and solution structures for cyclo(VPGVG)3. Also, near identical data for the cyclopentadecapeptide and the polypentapeptide demonstrate the cyclic conformation‐linear (helical) conformational correlate relationship between the two molecules. The 2D NOESY experiment is seen to be an effective means of establishing the presence or absence of a conformational relationship between a cyclic repeating sequence and its higher molecular weight linear counterpart. This is an approach of substantial practical value when developing the conformation of sequential polypeptides and when attempting to identify the presence of the conformation of a repeating peptide sequence within a more complex primary structure.Having established the basic conformational relationship between a cyclic conformation and its linear helical counterpart, cross peaks present in the linear helical structure that are not present in the cyclic conformational correlate can provide information on the interactions between adjacent turns of the helix. In this connection, a ValγCH3⟷ ProβCH2interaction is reported that can be the basis for determining the number of pentamers per turn of helix once it is determined whether it is dominantly the Val1or Val4γCH3that is interacting wi

ISSN:0006-3525    

DOI:10.1002/bip.360280404

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

年代:1989

数据来源: WILEY

摘要:

AbstractTheoretical computations are performed of the intercalative binding to a model d(CpG)2minihelix of 7‐H pyrido[4.3C]carbazole, the precursor of the antitumor bisintercalating drug ditercalinium. The conformations of the intercalation site are generated by the AGNAS procedure (algorithm to generate nucleic acid structures) of Miller and co‐workers. The ligand‐nucleotide interactions and the nucleotide conformational energies are computed with the SIBFA procedures (sum of interactions between fragments ab intio computed), which use formulas of empirical origin that reproduce ab initio SCF (self‐consistent field) computations. Among the candidate intercalation sites most favored energetically, one has a pattern of conformational angles related to the one determined crystallographically by Sobell et al. in a series of x‐ray structural studies of small intercalator–dinucleotide monophosphate complexes. Optimal values of the unwinding angle, found in the range of −12° to −14°, are consistent with available experim

ISSN:0006-3525    

DOI:10.1002/bip.360280405

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

年代:1989

数据来源: WILEY

摘要:

AbstractVibrational normal mode calculations are presented for a DNA hexanucleoside pentaphosphate, d(CpGpCpGpCpG)2, and for its complex with the cationic interclator ethidium. Two intercalation sites are modeled that differ in DNA backbone torsion angles. Normal mode frequencies for the DNA fragment itself are significantly lower than those reported earlier using different force fields, but an analysis of “effective” frequencies suggests that somewhat higher frequencies are more appropriate. Intercalation leads to significant lowering of mobility for the base pairs adjacent to the drug; in this sequence, the ethidium binding affects the guanosine atoms more strongly than the cytosine atoms. Motions of the bases and the intercalator are analyzed in terms of “twist” about the local helix axis and a “tilt” angle relative to this axis, and the results are compared to fluorescence studies of ethidium‐

ISSN:0006-3525    

DOI:10.1002/bip.360280406

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

年代:1989

数据来源: WILEY

摘要:

AbstractA method is offered to model the complex trajectories of closed circular DNA supercoils and knots. The trajectories are approximated by polygons and analytical expressions of the curves are generated from the polygons with B‐spline functions. The resulting curves are used to evaluate the writhe and elastic energy of a series of interrelated supercoils, and to generate detailed atomic models of the deformed double heli

ISSN:0006-3525    

DOI:10.1002/bip.360280407

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

年代:1989

数据来源: WILEY

ISSN:0006-3525    

DOI:10.1002/bip.360280408

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

年代:1989

数据来源: WILEY

ISSN:0006-3525    

DOI:10.1002/bip.360280401

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

年代:1989

数据来源: WILEY