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1.
The effects of hydrophobic thickness and the molar phosphatidylglycerol (PG) content of lipid bilayers on the structure and membrane interaction of three cationic antimicrobial peptides were examined: aurein 2.2, aurein 2.3 (almost identical to aurein 2.2, except for a point mutation at residue 13), and a carboxy C-terminal analog of aurein 2.3. Circular dichroism results indicated that all three peptides adopt an α-helical structure in the presence of a 3:1 molar mixture of 1,2-dimyristoyl-sn-glycero-3-phosphocholine/1,2-dimyristoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DMPC/DMPG), and 1:1 and 3:1 molar mixtures of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine/1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (POPC/POPG). Oriented circular dichroism data for three different lipid compositions showed that all three peptides were surface-adsorbed at low peptide concentrations, but were inserted into the membrane at higher peptide concentrations. The 31P solid-state NMR data of the three peptides in the DMPC/DMPG and POPC/POPG bilayers showed that all three peptides significantly perturbed lipid headgroups, in a peptide or lipid composition-dependent manner. Differential scanning calorimetry results demonstrated that both amidated aurein peptides perturbed the overall phase structure of DMPC/DMPG bilayers, but perturbed the POPC/POPG chains less. The nature of the perturbation of DMPC/DMPG bilayers was most likely micellization, and for the POPC/POPG bilayers, distorted toroidal pores or localized membrane aggregate formation. Calcein release assay results showed that aurein peptide-induced membrane leakage was more severe in DMPC/DMPG liposomes than in POPC/POPG liposomes, and that aurein 2.2 induced higher calcein release than aurein 2.3 and aurein 2.3-COOH from 1:1 and 3:1 POPC/POPG liposomes. Finally, DiSC35 assay data further delineated aurein 2.2 from the others by showing that it perturbed the lipid membranes of intact S. aureus C622 most efficiently, whereas aurein 2.3 had the same efficiency as gramicidin S, and aurein 2.3-COOH was the least efficient. Taken together, these data show that the membrane interactions of aurein peptides are affected by the hydrophobic thickness of the lipid bilayers and the PG content. 相似文献
2.
Matthias Meier 《Biophysical journal》2010,98(8):1529-1538
The effect of nonionic detergents of the n-alkyl-β-D-glucopyranoside class on the ordering of lipid bilayers and the dynamics of membrane-embedded peptides were investigated with 2H- and 31P-NMR. 1,2-dipalmitoyl-sn-glycero-3-phosphocholine was selectively deuterated at methylene segments C-2, C-7, and C-16 of the two fatty acyl chains. Two trans-membrane helices, WALP-19 and glycophorin A71-98, were synthesized with Ala-d3 in the central region of the α-helix. n-Alkyl-β-D-glucopyranosides with alkyl chains with 6, 7, 8, and 10 carbon atoms were added at increasing concentrations to the lipid membrane. The bilayer structure is retained up to a detergent/lipid molar ratio of 1:1. The insertion of the detergents leads to a selective disordering of the lipids. The headgroup region remains largely unaffected; the fatty acyl chain segments parallel to the detergent alkyl chain are only modestly disordered (10-20%), whereas lipid segments beyond the methyl terminus of the detergent show a decrease of up to 50%. The change in the bilayer order profile corresponds to an increase in bilayer entropy. Insertion of detergents into the lipid bilayers is completely entropy-driven. The entropy change accompanying lipid disorder is equivalent in magnitude to the hydrophobic effect. Ala-d3 deuterated WALP-19 and GlycA71-97 were incorporated into bilayers of 1,2-dimyristoyl-sn-glycero-3-phosphocholine at a peptide/lipid molar ratio of 1:100 and measured above the 1,2-dimyristoyl-sn-glycero-3-phosphocholine gel/liquid-crystal phase transition. Well-resolved 2H-NMR quadrupole splittings were observed for the two trans-membrane helices, revealing a rapid rotation of the CD3 methyl rotor superimposed on an additional rotation of the whole peptide around the bilayer normal. The presence of detergent fluidizes the membrane and produces magnetic alignment of bilayer domains but does not produce essential changes in the peptide conformation or dynamics. 相似文献
3.
《生物化学与生物物理学报:生物膜》2018,1860(8):1489-1501
Lipid bilayers play an important role in biological systems as they protect cells against unwanted chemicals and provide a barrier for material inside a cell from leaking out. In this paper, nearly 30 μs of molecular dynamics (MD) simulations were performed to investigate phase transitions of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dipalmitoyl-sn-glycero-phosphocholine (DPPC) lipid bilayers from the liquid crystalline (Lα) to the ripple (Pβ) and to the gel phase (Lβ). Our MD simulations accurately predict the main transition temperature for the single-component bilayers. A key focus of this work is to quantify the structure of the Pβ phase for DMPC and compare with measures from x-ray experiments. The Pβ major arm has similar structure to that of the Lβ, while the thinner minor arm has interdigitated chains and the transition region between these two regions has large chain splay and disorder. At lower temperatures, our MD simulations predict the formation of the Lβ phase with tilted fatty acid chains. The Pβ and Lβ phases are studied for mixtures of DMPC and DPPC and compare favorably with experiment. Overall, our MD simulations provide evidence for the relevancy of the CHARMM36 lipid force field for structures and add to our understanding of the less-defined Pβ phase. 相似文献
4.
Oxidation of glycerophospholipids results in the formation of large variety of oxidized phospholipid products that differs significantly in their chemical compositions and molecular structures. Biological activities of these oxidized products also differ considerably. Here we report the comparisons of the physicochemical properties of non-oxidized phospholipid particle containing two closely related tOx-PLs: 1-palmitoyl-2-(5-keto-6-octendioyl)-sn-glycero-3-phosphocholine (KOdiA-PC) and 1-palmitoyl-2-(9-keto-10-dodecendioyl)-sn-glycero-3-phosphocholine (KDdiA-PC). DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) was used as a model membrane non-oxidized phospholipid. Physicochemical properties of the lipid particles were characterized by using fluorescence spectroscopy, native polyacrylamide gel and agarose gel electrophoresis. Our result shows that the presence of closely related tOx-PLs, which differ only in the chemical composition of the oxidized fatty acyl chains at the sn-2 position, exerts considerably different effect on the physicochemical properties of non-oxidized phospholipid particles containing them. 相似文献
5.
The mixed Langmuir monolayers composed of model constituents of biological membranes, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphocholine (POPC), and 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), were investigated to provide information on the intermolecular interactions between these membrane components and the physiologically active vitamin E–α-tocopherol (TF), as well as on the phase behavior of these mixed systems. Additionally, topography of these monolayers transferred onto the mica support was investigated by the inverted metallurgical microscope. Morphological characteristics were directly observed by Brewster angle microscopy (BAM). From the surface pressure–area isotherms and the analysis of physicochemical parameters (compressibility and mean molecular area at the maximum compressibility) it was found that depending on the acyl chains saturation degree, TF has different effect on the phospholipids. In the case of DPPC, the addition of TF to the phospholipid film causes destabilization of the ordered hydrocarbon chains, while in the POPC/DOPC–TF systems, the attractive interactions are responsible for the monolayer increased stability. Thus, the results of these studies confirm the hypothesis that α-tocopherol may play a role in the stabilization of biological membranes. 相似文献
6.
Tomoya Taniguchi Toshinori Shimanouchi Masayuki Sohgawa Minoru Noda 《Biotechnology and bioengineering》2020,117(8):2469-2478
To facilitate the early diagnosis of Alzheimer's disease and mild cognitive impairment patients, we developed a cantilever-based microsensor that immobilized liposomes of various phospholipids to detect a trace amount of amyloid β (Aβ) protein, and investigated its aggregation and fibrillization on model cell membranes in human serum. Three species of liposomes composed of different phospholipids of 1,2-dipalmtoyl-sn-glycero-3-phosphocholine (DPPC), DPPC/phosphatidyl ethanolamine and 1,2-dipalmitoyl-sn-glycero-3-phosphorylglycerol having varied hydrophilic groups were applied, which showed different chronological interactions with Aβ(1–40) protein and varied sensitivities of the cantilever sensor, depending on their specific electrostatic charged conditions, hydrophilicity, and membrane fluidity. 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) having short hydrophobic carbon chains confirmed to show a large interaction with Aβ(1–40) and a high sensitivity. Furthermore, the incorporation of cholesterol into DMPC was effective to selectively detect Aβ(1–40) in human serum, which effect was also checked by quartz crystal microbalance. Finally, Aβ detection of 100-pM order was expected selectively in the serum by using the developed biosensor. 相似文献
7.
S. Sunder D.G. Cameron H.L. Casal Y. Boulanger H.H. Mantsch 《Chemistry and physics of lipids》1981,28(2):137-147
Deuterated methylene groups have been introduced synthetically in selected positions of the sn-2 palmitoyl chain of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and deuterated methyl groups in the sn-1 and sn-2 palmitoyl chains as well as in the sn-3 phosphocholine group.The vibrational spectra of seven such deuterium labelled derivatives of the title compound have been studied as the assignment of the C–D stretching vibrations is discussed. 相似文献
8.
We have studied RNA binding to vesicles bounded by ordered and disordered phospholipid membranes. A positive correlation exists between bilayer order and RNA affinity. In particular, structure-dependent RNA binding appears for rafted (liquid-ordered) domains in sphingomyelin-cholesterol-1,2-dioleoyl-sn-glycero-3-phosphocholine vesicles. Binding to more highly ordered gel phase membranes is stronger, but much less RNA structure-dependent. All modes of RNA-membrane association seem to be electrostatic and headgroup directed. Fluorometry on 1,2-dimyristoyl-sn-glycero-3-phosphocholine liposomes indicates that bound RNA broadens the gel-fluid melting transition, and reduces lipid headgroup order, as detected via fluorometric measurement of intramembrane electric fields. RNA preference for rafted lipid was visualized and confirmed using multiple fluorophores that allow fluorescence and fluorescence resonance energy transfer microscopy on RNA molecules closely associated with ordered lipid patches within giant vesicles. Accordingly, both RNA structure and membrane order could modulate biological RNA–membrane interactions. 相似文献
9.
The interaction of cationic pentalysine with phospholipid membranes was studied by using phosphorus and deuterium Nuclear Magnetic Resonance (NMR) of headgroup deuterated dimyristoyl phosphatidylcholine (DMPC) and dimyristoyl phosphatidylserine (DMPS). In the absence of pentalysine, some of the deuterium and phosphorus spectra of DMPC/DMPS 5:1 (m:m) membranes gave lineshapes similar to those of partially-oriented bilayers with the planes of the bilayers being parallel to the magnetic field. The deuterium NMR data show that the quadrupolar splittings of the deuterated methylenes of the DMPC headgroup are not affected by adsorption of pentalysine on the PC/PS membranes. By contrast, the pentalysine produces significant changes in the quadrupolar splittings of the negatively charged DMPS headgroup. The results are discussed in relation to previous 2H NMR investigations of phospholipid headgroup perturbations arising from bilayer interaction with cationic molecules.Abbreviations NMR
nuclear magnetic resonance
- DMPC
1,2-dimyristoyl-sn-glycero-3-phosphocholine
- DMPS
1,2-dimyristoyl-sn-glycero-3-phosphoserine
- POPC
1-palmitoyl, 2-oleyl-sn-glycero-3-phosphocholine
- POPG
1-palmitoyl-2-oleyl-sn-glycero-3-phosphoglycerol
- PC
phosphatidylcholine
- PS
phosphatidyl serine
- PG
phosphatidylglycerol
- HEPES
N-(2-hydroxy-ethyl)piperazine-N-2-ethanesulfonic acid
- TRIS
tris-(hydroxymethyl)aminoethane
- EDTA
ethylenediamine-tetra-acetic acid 相似文献
10.
Hongwei Wu Kai Su Xudong Guan M. Elizabeth Sublette Ruth E. Stark 《生物化学与生物物理学报:生物膜》2010,1798(3):482-3203
Aqueous phospholipid mixtures that form bilayered micelles (bicelles) have gained wide use by molecular biophysicists during the past 20 years for spectroscopic studies of membrane-bound peptides and structural refinement of soluble protein structures. Nonetheless, the utility of bicelle systems may be compromised by considerations of cost, chemical stability, and preservation of the bicelle aggregate organization under a broad range of temperature, concentration, pH, and ionic strength conditions. In the current work, 31P nuclear magnetic resonance (NMR) and atomic force microscopy (AFM) have been used to monitor the size and morphology of isotropically tumbling small bicelles formed by mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) or 1,2-di-O-tetradecyl-sn-glycero-3-phosphocholine (DIOMPC) with either 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) or 1,2-di-O-hexyl-sn-glycero-3-phosphocholine (DIOHPC), testing their tolerance of variations in commonly used experimental conditions. 1H-15N 2D NMR has been used to demonstrate the usefulness of the robust DMPC-DIOHPC system for conformational studies of a fatty acid-binding protein that shuttles small ligands to and from biological membranes. 相似文献
11.
SAXS/WAXS studies were performed in combination with freeze fracture electron microscopy using mixtures of a new Gemini catanionic surfactant (Gem16-12, formed by two sugar groups bound by a hydrocarbon spacer with 12 carbons and two 16-carbon chains) and the zwitterionic phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) to establish the phase diagram. Gem16-12 in water forms bilayers with the same amount of hydration water as DPPC. A frozen interdigitated phase with a low hydration number is observed below room temperature. The kinetics of the formation of this crystalline phase is very slow. Above the chain melting temperature, multilayered vesicles are formed. Mixing with DPPC produces mixed bilayers above the corresponding chain melting temperature. At room temperature, partially lamellar aggregates with local nematic order are observed. Splitting of infinite lamellae into discs is linked to immiscibility in frozen state. The ordering process is always accompanied by dehydration of the system. As a consequence, an unusual order-disorder phase transition upon cooling is observed. 相似文献
12.
Erik?B. Watkins Haifei Gao Andrew?J.C. Dennison Nathalie Chopin Bernd Struth Thomas Arnold Jean-Claude Florent Ludger Johannes 《Biophysical journal》2014,107(5):1146-1155
Globotriaosylceramide (Gb3), a glycosphingolipid found in the plasma membrane of animal cells, is the endocytic receptor of the bacterial Shiga toxin. Using x-ray reflectivity (XR) and grazing incidence x-ray diffraction (GIXD), lipid monolayers containing Gb3 were investigated at the air-water interface. XR probed Gb3 carbohydrate conformation normal to the interface, whereas GIXD precisely characterized Gb3’s influence on acyl chain in-plane packing and area per molecule (APM). Two phospholipids, 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE), were used to study Gb3 packing in different lipid environments. Furthermore, the impact on monolayer structure of a naturally extracted Gb3 mixture was compared to synthetic Gb3 species with uniquely defined acyl chain structures. XR results showed that lipid environment and Gb3 acyl chain structure impact carbohydrate conformation with greater solvent accessibility observed for smaller phospholipid headgroups and long Gb3 acyl chains. In general, GIXD showed that Gb3 condensed phospholipid packing resulting in smaller APM than predicted by ideal mixing. Gb3’s capacity to condense APM was larger for DSPC monolayers and exhibited different dependencies on acyl chain structure depending on the lipid environment. The interplay between Gb3-induced changes in lipid packing and the lipid environment’s impact on carbohydrate conformation has broad implications for glycosphingolipid macromolecule recognition and ligand binding. 相似文献
13.
Erik B. Watkins Haifei Gao Andrew J.C. Dennison Nathalie Chopin Bernd Struth Thomas Arnold Jean-Claude Florent Ludger Johannes 《Biophysical journal》2014
Globotriaosylceramide (Gb3), a glycosphingolipid found in the plasma membrane of animal cells, is the endocytic receptor of the bacterial Shiga toxin. Using x-ray reflectivity (XR) and grazing incidence x-ray diffraction (GIXD), lipid monolayers containing Gb3 were investigated at the air-water interface. XR probed Gb3 carbohydrate conformation normal to the interface, whereas GIXD precisely characterized Gb3’s influence on acyl chain in-plane packing and area per molecule (APM). Two phospholipids, 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE), were used to study Gb3 packing in different lipid environments. Furthermore, the impact on monolayer structure of a naturally extracted Gb3 mixture was compared to synthetic Gb3 species with uniquely defined acyl chain structures. XR results showed that lipid environment and Gb3 acyl chain structure impact carbohydrate conformation with greater solvent accessibility observed for smaller phospholipid headgroups and long Gb3 acyl chains. In general, GIXD showed that Gb3 condensed phospholipid packing resulting in smaller APM than predicted by ideal mixing. Gb3’s capacity to condense APM was larger for DSPC monolayers and exhibited different dependencies on acyl chain structure depending on the lipid environment. The interplay between Gb3-induced changes in lipid packing and the lipid environment’s impact on carbohydrate conformation has broad implications for glycosphingolipid macromolecule recognition and ligand binding. 相似文献
14.
The increased use of plant sterols as cholesterol-lowering agents warrants further research on the possible effects of plant sterols in membranes. In this study, the effects of the incorporation of cholesterol, campesterol, β-sitosterol and stigmasterol in phospholipid bilayers were investigated by differential scanning calorimetry (DSC), resonance energy transfer (RET) between trans parinaric acid (tPA) and 2-(6-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)hexanoyl-1-hexadecanoyl-sn-glycero-3-phosphocholine (NBD-PC), and Triton X-100-induced solubilization. The phospholipids used were 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), d-erythro-N-palmitoyl-sphingomyelin (PSM), and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). In DSC experiments, it was demonstrated that the sterols differed in their effect on the melting temperatures of both the sterol-poor and the sterol-rich domains in DPPC and PSM bilayers. The plant sterols gave rise to lower temperatures of both transitions, when compared with cholesterol. The plant sterols also resulted in lower transition temperatures, in comparison with cholesterol, when sterol-containing DPPC and PSM bilayers were investigated by RET. In the detergent solubilization experiments, the total molar ratio between Triton X-100 and POPC at the onset of solubilization (Rt,sat) was higher for bilayers containing plant sterols, in comparison with membranes containing cholesterol. Taken together, the observations presented in this study indicate that campesterol, β-sitosterol and stigmasterol interacted less favorably than cholesterol with the phospholipids, leading to measurable differences in their domain properties. 相似文献
15.
María Florencia Pignataro Martín M. Dodes-Traian F. Luis González-Flecha Mauricio Sica Irene C. Mangialavori Juan Pablo F. C. Rossi 《The Journal of biological chemistry》2015,290(10):6179-6190
The effects of lipids on membrane proteins are likely to be complex and unique for each membrane protein. Here we studied different detergent/phosphatidylcholine reconstitution media and tested their effects on plasma membrane Ca2+ pump (PMCA). We found that Ca2+-ATPase activity shows a biphasic behavior with respect to the detergent/phosphatidylcholine ratio. Moreover, the maximal Ca2+-ATPase activity largely depends on the length and the unsaturation degree of the hydrocarbon chain. Using static light scattering and fluorescence correlation spectroscopy, we monitored the changes in hydrodynamic radius of detergent/phosphatidylcholine particles during the micelle-vesicle transition. We found that, when PMCA is reconstituted in mixed micelles, neutral phospholipids increase the enzyme turnover. The biophysical changes associated with the transition from mixed micelles to bicelles increase the time of residence of the phosphorylated intermediate (EP), decreasing the enzyme turnover. Molecular dynamics simulations analysis of the interactions between PMCA and the phospholipid bilayer in which it is embedded show that in the 1,2-dioleoyl-sn-glycero-3-phosphocholine bilayer, charged residues of the protein are trapped in the hydrophobic core. Conversely, in the 1,2-dimyristoyl-sn-glycero-3-phosphocholine bilayer, the overall hydrophobic-hydrophilic requirements of the protein surface are fulfilled the best, reducing the thermodynamic cost of exposing charged residues to the hydrophobic core. The apparent mismatch produced by a 1,2-dioleoyl-sn-glycero-3-phosphocholine thicker bilayer could be a structural foundation to explain its functional effect on PMCA. 相似文献
16.
Perturbation of DPPC bilayers by high concentrations of pulmonary surfactant protein SP-B 总被引:3,自引:0,他引:3
Deuterium (2H) NMR has been used to observe perturbation of dipalmitoylphosphatidylcholine (DPPC) bilayers by the pulmonary surfactant protein B (SP-B) at concentrations up to 17% (w/w). Previous 2H NMR studies of DPPC/dipalmitoylphosphatidylglycerol (DPPG) (7:3) bilayers containing up to 11% (w/w) SP-B and DPPC bilayers containing up to 11% (w/w) synthetic SP-B indicated a slight effect on bilayer chain order and a more substantial effect on motions that contribute to decay of quadrupole echoes obtained from bilayers of deuterated DPPC. This is consistent with the perturbation of headgroup-deuterated DPPC reported here for bilayers containing 6 and 9% (w/w) SP-B. For the higher concentrations of SP-B investigated in the present work, 2H NMR spectra of DPPC deuterated in both the headgroup and chain display a prominent narrow component consistent with fast, large amplitude reorientation of some labeled lipid. Similar spectral perturbations have been reported for bilayers in the presence of the antibiotic polypeptide nisin. The observation of large amplitude lipid reorientation at high SP-B concentration could indicate that SP-B can induce regions of high bilayer curvature and thus provides some insight into local interaction of SP-B with DPPC. Such local interactions may be relevant to the formation, in vitro and in vivo, of tubular myelin, a unique structure found in extracellular pulmonary surfactant, and to the delivery of surfactant material to films at the air–water interface.Abbreviations DPPC 1,2-dipalmitoyl-sn-glycero-3-phosphocholine - DPPG 1,2-dipalmitoyl-sn-glycero-3-phosphoglycerol - DPPC-d62 1,2-perdeuterodipalmitoyl-sn-glycero-3-phosphocholine - DPPC-d4 1,2-dipalmitoyl-sn-glycero-3-phospho-(, perdeutero)-choline 相似文献
17.
Human islet amyloid polypeptide (hIAPP), which is considered the primary culprit for β-cell loss in type 2 diabetes mellitus patients, is synthesized in β-cells of the pancreas from its precursor pro-islet amyloid polypeptide (proIAPP), which may be important in early intracellular amyloid formation as well. We compare the amyloidogenic propensities and conformational properties of proIAPP and hIAPP in the presence of negatively charged lipid membranes, which have been discussed as loci of initiation of the fibrillation reaction. Circular dichroism studies verify the initial secondary structures of proIAPP and hIAPP to be predominantly unordered with small amounts of ordered secondary structure elements, and exhibit minor differences between these two peptides only. Using attenuated total reflection-Fourier transform infrared spectroscopy and thioflavin T fluorescence spectroscopy, as well as atomic force microscopy, we show that in the presence of negatively charged membranes, proIAPP exhibits a much higher amyloidogenic propensity than in bulk solvent. Compared to hIAPP, it is still much less amyloidogenic, however. Although differences in the secondary structures of the aggregated species of hIAPP and proIAPP at the lipid interface are small, they are reflected in morphological changes. Unlike hIAPP, proIAPP forms essentially oligomeric-like structures at the lipid interface. Besides the interaction with anionic membranes [1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) + x1,2-dioleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)]], interaction with zwitterionic homogeneous (DOPC) and heterogeneous (1,2-dipalmitoyl-sn-glycero-3-phosphocholine:DOPC:cholesterol 1:2:1 model raft mixture) membranes has also been studied. Both peptides do not aggregate significantly at DOPC bilayers. In the presence of the model raft membrane, hIAPP aggregates markedly as well. Conversely, proIAPP clusters into less ordered structures and to a minor extent at raft membranes only. The addition of proIAPP to hIAPP retards the hIAPP fibrillation process also in the presence of negatively charged lipid bilayers. In excess proIAPP, increased aggregation levels are finally observed, however, which could be attributed to seed-induced cofibrillation of proIAPP. 相似文献
18.
The influenza virus matrix protein 2 (M2) assembles into a tetramer in the host membrane during viral uncoating and maturation. It has been used as a model system to understand the relative contributions of protein-lipid and protein-protein interactions to membrane protein structure and association. Here we investigate the effect of lipid chain length on the association of the M2 transmembrane domain into tetramers using Förster resonance energy transfer. We observe that the interactions between the M2 helices are much stronger in 1,2-dilauroyl-sn-glycero-3-phosphocholine than in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine bilayers. Thus, lipid chain length and bilayer thickness not only modulate peptide interactions, but could also be a major determinant of the association of transmembrane helices into functional membrane protein oligomers. 相似文献
19.
By means of Fourier transform infrared spectroscopy the subtransition temperature of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and the derivatives in which either or both of the acyl chains were deuterated were determined. It was found that, while the temperatures of the gel to liquid-crystal and the pre-transitions decrease with increasing deuteration, the temperature of the subtransition is independent of the degree of deuteration. 相似文献
20.
Salnikov ES Friedrich H Li X Bertani P Reissmann S Hertweck C O'Neil JD Raap J Bechinger B 《Biophysical journal》2009,96(1):86-100
Ampullosporin A and alamethicin are two members of the peptaibol family of antimicrobial peptides. These compounds are produced by fungi and are characterized by a high content of hydrophobic amino acids, and in particular the α-tetrasubstituted amino acid residue α-aminoisobutyric acid. Here ampullosporin A and alamethicin were uniformly labeled with 15N, purified and reconstituted into oriented phophatidylcholine lipid bilayers and investigated by proton-decoupled 15N and 31P solid-state NMR spectroscopy. Whereas alamethicin (20 amino acid residues) adopts transmembrane alignments in 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) or 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membranes the much shorter ampullosporin A (15 residues) exhibits comparable configurations only in thin membranes. In contrast the latter compound is oriented parallel to the membrane surface in 1,2-dimyristoleoyl-sn-glycero-3-phosphocholine and POPC bilayers indicating that hydrophobic mismatch has a decisive effect on the membrane topology of these peptides. Two-dimensional 15N chemical shift - 1H-15N dipolar coupling solid-state NMR correlation spectroscopy suggests that in their transmembrane configuration both peptides adopt mixed α-/310-helical structures which can be explained by the restraints imposed by the membranes and the bulky α-aminoisobutyric acid residues. The 15N solid-state NMR spectra also provide detailed information on the helical tilt angles. The results are discussed with regard to the antimicrobial activities of the peptides. 相似文献