Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0851184 (thinning)
 11,252 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Polymer-polymer interactions were investigated for mixtures of a poly(acrylic acid) (pAA) carrying azobenzene (pC12Azo) and two kinds of pAA carrying alpha-cyclodextrin (CD), in which CDs are attached to the main chain through the 3- and 6-positions in CD (p3alphaCD and p6alphaCD, respectively), using several techniques, such as viscosity and NMR measurements. Viscosity data exhibited contrast changes upon UV irradiation: thinning (p3alphaCD/pC12Azo) and thickening (p6alphaCD/pC12Azo). NOESY spectra confirmed that the contrast viscosity changes were ascribable to differences in how CD moieties interact with pC12Azo after photoisomerization of azobenzene moieties from trans to cis: dissociation of inclusion complexes (p3alphaCD/pC12Azo) and formation of interlocked complexes (p6alphaCD/pC12Azo).
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PMID:Contrast viscosity changes upon photoirradiation for mixtures of poly(acrylic acid)-based alpha-cyclodextrin and azobenzene polymers. 1647 72

Identifying the mechanisms responsible for the interaction of peptides with cell membranes is critical to the design of new antimicrobial peptides and membrane transporters. We report here the results of a computational simulation of the interaction of the 13-residue peptide indolicidin with single-phase lipid bilayers of dioleoylphosphatidylcholine, distearoylphosphatidylcholine, dioleoylphosphatidylglycerol, and distearoylphosphatidylglycerol. Ensemble analysis of the membrane-bound peptide revealed that, in contrast to the extended, linear backbone structure reported for indolicidin in sodium dodecyl sulphate detergent micelles, the peptide adopts a boat-shaped conformation in both phosphatidylglycerol and phosphatidylcholine lipid bilayers, similar to that reported for dodecylphosphocholine micelles. In agreement with fluorescence and NMR experiments, simulations confirmed that the peptide localizes in the membrane interface, with the distance between phosphate headgroups of each leaflet being reduced in the presence of indolicidin. These data, along with a concomitant decrease in lipid order parameters for the upper-tail region, suggest that indolicidin binding results in membrane thinning, consistent with recent in situ atomic force microscopy studies.
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PMID:Molecular dynamics simulations of indolicidin association with model lipid bilayers. 1741 17

Interfacial anchoring interactions between aromatic amino acid residues and the lipid-water interface are believed to be important determinants for membrane protein structure and function. Thus, it is possible that molecules that partition into the lipid-water interface can influence membrane protein activity simply by interfering with these anchoring interactions. Here we tested this hypothesis by investigating the effects of 2,2,2-trifluoroethanol (TFE) on the interaction of a Trp-flanked synthetic transmembrane peptide (acetyl-GW(2)(LA)(8)LW(2)A-NH(2)) with model membranes of dimyristoylphosphatidylcholine. Two striking observations were made. First, using (2)H nuclear magnetic resonance on acyl chain deuterated lipids, we found that addition of 4 or 8 vol % of TFE completely abolishes the ability of the peptide to order and stretch the lipid acyl chains in these relatively thin bilayers. Second, we observed that addition of 8 vol % TFE reduces the tilt angle of the peptide from 5.3 degrees to 2.5 degrees, as measured by (2)H NMR on Ala-d(4) labeled peptides. The "straightening" of the peptide was accompanied by an increased exposure of Trp to the aqueous phase, as shown by Trp-fluorescence quenching experiments using acrylamide. The observation of a reduced tilt angle was surprising because we also found that TFE partioning results in a significant thinning of the membrane, which would increase the extent of hydrophobic mismatch. In contrast to the Trp-flanked peptide, no effect of TFE was observed on the interaction of a Lys-flanked analog (acetyl-GK(2)(LA)(8)LK(2)A-NH(2)) with the lipid bilayer. These results emphasize the importance of interfacial anchoring interactions for membrane organization and provide new insights into how molecules such as TFE that can act as anesthetics may affect the behavior of membrane proteins that are enriched in aromatic amino acids at the lipid-water interface.
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PMID:Influence of trifluoroethanol on membrane interfacial anchoring interactions of transmembrane alpha-helical peptides. 1790 43

As part of a project to utilize the regenerated silk fibroin (RSF) membranes as a supporting matrix for the attachment and growth of corneal stem/progenitor cells in the development of tissue engineered constructs for the surgical restoration of the ocular surface, the behavior of the aged RSF solutions has been investigated. The solutions were produced from domesticated silkworm (Bombyx mori) cocoons according to a protocol involving successive dissolution steps, filtration and dialysis. The solutions were kept at 4 degrees C in a refrigerator for a certain period of time until near the gelation time. The changes in molecular conformation were studied by solution-state (1)H NMR, while the flow of the solutions was characterized by rheological method. Upon ageing turbidity developed in solutions and the viscosity continuously decreased prior to a drastic increased near the gelation time. The (1)H resonances of aged solutions showed a consistent downfield shift as compared to the (1)H resonances of the fresh solution. Shear thinning with anomalous short recovery within a certain range of low shear rates occurred in both fresh and aged solutions. While the solutions behave as pseudo-plastic materials, the chain conformation in aged solutions adopted all secondary configurations with beta-strand being predominant.
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PMID:The behavior of aged regenerated Bombyx mori silk fibroin solutions studied by (1)H NMR and rheology. 1871 39

The cardiac muscle architecture lies at the basis of the mechanical and electrical properties of the heart, and dynamic alterations in fiber structure are known to be of prime importance in healing and remodeling after myocardial infarction. In this study, left ventricular remodeling was characterized using diffusion tensor imaging (DTI) in a mouse model of myocardial infarction. Myocardial infarction was induced in mice by permanent ligation of the left anterior descending coronary artery. Serial ex vivo DTI measurements were performed 7, 14, 28, and 60 days after ligation. Apparent diffusion coefficient, fractional anisotropy, the three eigenvalues of the diffusion tensor, and the myofiber disarray served as readout parameters. After myocardial infarction, the mouse hearts displayed extreme wall thinning in the infarcted area, which covered large parts of the apex and extended into the free wall up to the equator. Average heart mass increased by 70% 7-60 days after infarction. Histological analysis showed that the infarct at 7 days consisted of unstructured tissue with residual necrosis and infiltration of macrophages and myofibroblasts. At 14 days after infarction, the necrotic tissue had disappeared and collagen fibers were starting to appear. From 28 to 60 days, the infarct had fully developed into a mature scar. DTI parameters showed dynamic changes as a function of time after infarction. The apparent diffusion coefficient in the infarcted region was lower than in remote regions and increased as a function of time after infarction. The fractional anisotropy was higher in the infarcted region and was maximum at 28 days, which was attributed to the development of structured collagen fibers. Myofiber disarray, which was analyzed by considering the alignment of fibers in neighboring voxels, was significantly higher in infarcted regions. DTI provides a valuable non-destructive tool for characterizing structural remodeling in diseased myocardium.
NMR Biomed 2009 Feb
PMID:Diffusion tensor imaging of left ventricular remodeling in response to myocardial infarction in the mouse. 1878 Feb 84

Using x-ray diffraction, solid-state 2H-NMR, differential scanning calorimetry, and dilatometry, we have observed a perturbation of saturated acyl chain phosphatidylglycerol bilayers by the antimicrobial peptide peptidyl-glycylleucine-carboxyamide (PGLa) that is dependent on the length of the hydrocarbon chain. In the gel phase, PGLa induces a quasi-interdigitated phase, previously reported also for other peptides, which is most pronounced for C18 phosphatidylglycerol. In the fluid phase, we found an increase of the membrane thickness and NMR order parameter for C14 and C16 phosphatidylglycerol bilayers, though not for C18. The data is best understood in terms of a close hydrophobic match between the C18 bilayer core and the peptide length when PGLa is inserted with its helical axis normal to the bilayer surface. The C16 acyl chains appear to stretch to accommodate PGLa, whereas tilting within the bilayer seems to be energetically favorable for the peptide when inserted into bilayers of C14 phosphatidylglycerol. In contrast to the commonly accepted membrane thinning effect of antimicrobial peptides, the data demonstrate that pore formation does not necessarily relate to changes in the overall bilayer structure.
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PMID:Membrane thickening by the antimicrobial peptide PGLa. 1883 2

Independent experimental and computational approaches show agreement concerning arginine/membrane interactions when a single arginine is introduced at selected positions within the membrane-spanning region of acetyl-GGALW(5)LALALAL(12)AL(14)ALALW(19)LAGA-ethanolamide, designated GWALP23. Peptide sequence isomers having Arg in position 12 or position 14 display markedly different behaviors, as deduced by both solid-state NMR experiments and coarse-grained molecular dynamics (CG-MD) simulations. With respect to the membrane normal of DOPC or DPPC lipid bilayer membranes, GWALP23-R14 shows one major state whose apparent average tilt is approximately 10 degrees greater than that of GWALP23. The presence of R14 furthermore induces bilayer thinning and peptide displacement to "lift" the charged guanidinium toward the bilayer surface. By contrast, GWALP23-R12 exhibits multiple states that are in slow exchange on the NMR time scale, with CG-MD simulations indicating two distinct positions with different screw rotation angles in the membrane, along with an increased tendency to exit the lipid bilayer.
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PMID:Changes in transmembrane helix alignment by arginine residues revealed by solid-state NMR experiments and coarse-grained MD simulations. 2037 35

(2)H NMR experiments on a nonionic oriented lamellar phase demonstrate that shear flow induces structural defects in the lamellar structure. These substantial structural changes give rise to a transition from a viscous to a solidlike behavior; the elastic modulus of presheared samples was found to increase, reversibly, with the applied preshear rate. A similar behavior was found when step-cycling the temperature toward the layer-to-multilamellar-vesicle transition and back at constant shear rate. However, while shear rate controls the defect density, the temperature is found to control the defect rigidity. The lamellar phase exhibits a shear-thinning behavior under steady shear conditions, following the power law eta approximately gamma(n), with n approximately -0.4. Both the shear thinning and the elastic behavior are in agreement with the available theoretical models. The observed shear-induced structural defects are reversible and can be regarded as a pretransition prior to the shear-induced formation of multilamellar vesicles.
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PMID:Shear-induced defect formation in a nonionic lamellar phase. 2037 78

The opening and closing of voltage-gated potassium (Kv) channels are controlled by several conserved Arg residues in the S4 helix of the voltage-sensing domain. The interaction of these positively charged Arg residues with the lipid membrane has been of intense interest for understanding how membrane proteins fold to allow charged residues to insert into lipid bilayers against free-energy barriers. Using solid-state NMR, we have now determined the orientation and insertion depth of the S4 peptide of the KvAP channel in lipid bilayers. Two-dimensional (15)N correlation experiments of macroscopically oriented S4 peptide in phospholipid bilayers revealed a tilt angle of 40 degrees and two possible rotation angles differing by 180 degrees around the helix axis. Remarkably, the tilt angle and one of the two rotation angles are identical to those of the S4 helix in the intact voltage-sensing domain, suggesting that interactions between the S4 segment and other helices of the voltage-sensing domain are not essential for the membrane topology of the S4 helix. (13)C-(31)P distances between the S4 backbone and the lipid (31)P indicate a approximately 9 A local thinning and 2 A average thinning of the DMPC (1,2-dimyristoyl-sn-glycero-3-phosphochloline)/DMPG (1,2-dimyristoyl-sn-glycero-3-phosphatidylglycerol) bilayer, consistent with neutron diffraction data. Moreover, a short distance of 4.6 A from the guanidinium C(zeta) of the second Arg to (31)P indicates the existence of guanidinium phosphate hydrogen bonding and salt bridges. These data suggest that the structure of the Kv gating helix is mainly determined by protein-lipid interactions instead of interhelical protein-protein interactions, and the S4 amino acid sequence encodes sufficient information for the membrane topology of this crucial gating helix.
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PMID:High-resolution orientation and depth of insertion of the voltage-sensing S4 helix of a potassium channel in lipid bilayers. 2060 Jan 9

Lumichrome (L) and melamine (M) produce thermoreversible hydrogels in LM31 and LM11 compositions, but LM13 composition does not produce hydrogel (the numbers indicate the respective molar ratio of the components). The formation of thermoreversible gels is confirmed from morphology, DSC, and rheological experiments where LM13 system does not meet the required characteristics of thermoreversible gels. FTIR spectra suggest that H-bonding between L and M produces the supramolecular complex, and (1)H NMR spectra suggest that pi-stacking of the complex produce fibrillar network structure entrapping a large amount of water producing the hydrogels. The nonplanar structure of LM13 complex probably causes difficulty in pi-stacking, prohibiting the gel formation. The UV-vis spectra show a blue shift of the pi-pi* transition band (354 nm) indicating H-aggregate formation but the pi-pi* band coupled with n-pi* transition (386 nm) shows a constant red shift by 7 nm, indicating independency of pi-stacking on the n-pi* transition in the different LM systems. The PL intensities of LM11 and LM31 gels become more quenched than the intensity of pure L due to formation of nonfluorescent complex (static quenching) in the gels. In the LM13 sol the degree of quenching is less than that of the gels because of absence of energy transfer through the junction points of gels. The increased lifetime values of LM gels compared to that of pure L is also indicative of H-aggregate formation. The PL intensity increases linearly with increase of temperature due to thinning of the fibers decreasing the exciton energy transfer. The emission peak shows a red shift with rise in temperature, indicating H- to J-aggregate transformation, and at the melting temperature it shows a sharp decrease. With both increase and decrease of pH from the neutral pH 7, the gels exhibit higher PL intensity because of sol formation.
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PMID:Bicomponent hydrogels of lumichrome and melamine: photoluminescence property and its dependency on pH and temperature. 2071 27


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