Orientation studies of hydrated dipalmitoylphosphatidylcholine multibilayers by polarized FTIR-ATR spectroscopy

Okamura, Emiko; Umemura, Junzo; Takenaka, Tohru

doi:10.1016/0005-2736(90)90195-t

Cited by 70 publications

(57 citation statements)

References 24 publications

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“…The R ATR for the symmetric methylene stretch was 1.4, which results in a value of 0.4 for S L . This S L value would be considered low for DMPC but is consistent with liquid-crystalline lipids having an average bilayer orientation perpendicular to the supporting crystal and is in good agreement with S L values reported previously for gel-phase lipids taken above the phase transition temperature (41) and previous studies of POPC (45).…”

Section: Ir Spectroscopy In Lipid Bilayerssupporting

confidence: 91%

“…The dichroic ratio, R ATR , of the symmetric methylene stretch, determined from the ratio of absorbance at 0°and 90°polarizations, was 1.1, which results in a calculated lipid order parameter, S L of 0.7. This value is consistent with lipids in the gel phase forming a well ordered deposited bilayer parallel to the crystal surface (28,41).…”

Section: Ir Spectroscopy In Lipid Bilayerssupporting

confidence: 83%

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Conformation of the synaptobrevin transmembrane domain

Bowen

Brunger

2006

Proc. Natl. Acad. Sci. U.S.A.

101

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The synaptic vesicle protein synaptobrevin (also called VAMP, vesicle-associated membrane protein) forms part of the SNARE (soluble N-ethylmaleimide sensitive factor attachment protein receptor) complex, which is essential for vesicle fusion. Additionally, the synaptobrevin transmembrane domain can promote lipid mixing independently of complex formation. Here, the conformation of the transmembrane domain was studied by using circular dichroism and attenuated total reflection Fourier-transform infrared spectroscopy. The synaptobrevin transmembrane domain has an ␣-helical structure that breaks in the juxtamembrane region, leaving the cytoplasmic domain unstructured. In phospholipid bilayers, infrared dichroism data indicate that the transmembrane domain adopts a 36°angle with respect to the membrane normal, similar to that reported for viral fusion peptides. A conserved aromatic͞basic motif in the juxtamembrane region may be causing this relatively high insertion angle.Fourier-transform infrared spectroscopy ͉ membrane fusion ͉ membrane protein ͉ neuotransmission I n neurons, synaptic vesicles dock at the plasma membrane and fuse upon an increase in local Ca 2ϩ concentration, releasing neurotransmitters into the synaptic cleft (1-3). Many of the proteins involved in this complex reaction have been identified (4-8). Members of the SNARE (soluble N-ethylmaleimide sensitive factor attachment protein receptor) family are involved in the final stages of neurotransmitter release. The binding of the synaptic vesicle protein synaptobrevin to the plasma membrane proteins syntaxin and SNAP-25 is essential for stimulated neurotransmitter release. Although the required factors and precise sequence of events that trigger Ca 2ϩ -dependent vesicle fusion is hotly debated, the SNAREs are well established as a fundamental yet incomplete part of the fusion machinery (6).The neuronal SNARE proteins are largely unstructured as monomers (9-12) and undergo a dramatic structural transition to form an ␣-helical heterotrimer (13, 14). The energy from this structural transition was proposed to drive membrane fusion (10, 13, 15), but recent studies have shown that SNARE complex formation can occur without inducing fusion (16,17) and that SNAREs disrupt membranes and promote lipid mixing independent of complex formation (16,(18)(19)(20). Thus, the relationship between structure induction, complex formation, and membrane fusion activity remains unclear.Synaptobrevin (also called VAMP, vesicle-associated membrane protein) contains a single SNARE motif involved in formation of the complex with syntaxin and SNAP-25 and a C-terminal transmembrane domain. The conserved juxtamembrane region (residues 77-90) binds phospholipids and calmodulin (21). Tryptophan residues in the juxtamembrane region cause portions of the SNARE motif to insert into the bilayer (22). These interactions have been suggested to regulate SNARE complex formation and play a role in vesicle fusion (23)(24)(25). However, the effect of the transmembrane domain on the structure of ...

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Section: Ir Spectroscopy In Lipid Bilayerssupporting

confidence: 91%

Section: Ir Spectroscopy In Lipid Bilayerssupporting

confidence: 83%

Conformation of the synaptobrevin transmembrane domain

Bowen

Brunger

2006

Proc. Natl. Acad. Sci. U.S.A.

101

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“…Frequency changes of the antisymmetric and symmetric CH2 stretching (w,CH2 and w,CH2) bands on the monolayer compression are shown in Table 2. Both bands shift to lower frequencies with the increase in the surface pressure, suggesting the increase in the amount of all-trans conformers of the hydrocarbon chain (14)(15)(16). These frequency shifts are very similar to the recent results of ITIR external reflection spectroscopy by Dluhy et al (17,18) for DPPC monolayers spread on the water surface.…”

Section: Resultssupporting

confidence: 87%

“…observed at 1468 cm--' irrespective of the surface pressure, Quantitative evaluation of the molecular orientation indicating that the hydrocarbon chains are predominantly Using our new method (6), the orientation of the hydropacked in the hexagonal subcell lattice (6,14,15).…”

Section: Resultsmentioning

confidence: 99%

Molecular orientation in thin Langmuir–Blodgett films of dipalmitoylphosphatidylcholine as studied by FTIR transmission and reflection–absorption spectroscopy

Okamura¹,

Umemura²,

Takenaka³

1991

Can. J. Chem.

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EMIKO OKAMURA, JUNZO UMEMURA, and TOHRU TAKENAKA. Can. J. Chem. 69,1691Chem. 69, (1991.Langmuir-Blodgett (LB) films of DPPC were prepared by the horizontal lifting technique at various surface pressures encompassing the plateau region of its surface pressure (a) -area (A) isotherm. Molecular orientation in the LB films was quantitatively evaluated by a method recently proposed by Umemura et al. (J. Phys. Chem. 94, 62 (1990)) using Fourier transform infrared (FTIR) transmission and reflection-absorption (RA) spectra. From the results obtained, it is apparent that (i) in the LB films deposited at higher surface pressures above the plateau, the hydrocarbon chains are of all-trans conformation and well oriented at the tilting angle of ca. 20" from the surface normal; (ii) at lower surface pressures below the plateau, the chain segments are almost randomly oriented (like in a liquid-crystalline state) with an increased amount of the gauche conformers; and (iii) in the films deposited within the plateau, the hydrocarbon chains are in an intermediate state between the above two states. It is therefore concluded that the plateau corresponds to a process of the reorientation of the hydrocarbon chains from an almost randomly-oriented state to a highly-oriented one with the increase in the number of the all-trans conformers.Key words: dipalmitoylphosphatidylcholine, Langmuir-Blodgett film, molecular orientation, infrared reflection-absorption spectra, surface pressure-area isotherm.EMIKO OKAMURA, JUNZO UMEMURA et TOHRU TAKENAKA. Can. J. Chem. 69,1691Chem. 69, (1991.Utilisant la technique du soulkvement horizontal a diverse pressions superficielles couvrant la region du plateau de son isotherme de la pression superficielle (a) -surface (A), on a prCparC des films de Langmuir-Blodgett (LB) de la DPPC. Utilisant la mCthode proposCe rCcernrnent par Umemura et ses collaborateurs (J. Phys. Chem. 94, 62 (1990)) et bade sur les spectres infrarouges par transformation de Fourier de transmission (IRTF) et de rkflexion-absorption (RA), on a CvaluC d'une faqon quantitative l'orientation molCculaire dans les films de LB. A partir des rksultats obtenus, il est apparent que, dans les films LB dCposCs : (i) a des pressions superficielles supkrieures a celle du plateau, les chaines hydrocarbonCes posskdent toutes la conformation complbtement trans et elles sont toutes orientCes un angle d'environ 20°par rapport &la surface normale; (ii) a des pressions infkrieures a celles de la pression du plateau, les segments de chaines sont pratiquement orient& au hasard (Ctat semblable a celui d'un cristal-liquide) avec une quantitk plus importante des conformkres gauches; et (iii) a des pressions correspondant a celles du plateau, les chaines hydrocarbonCes sont dans un Ctat intermkdiaire entre les deux Ctats mentionnks plus haut. On en conclut donc que le plateau correspond a un processus de rkorientation des chaines hydrocarbontes d'un Ctat orient6 pratiquement au hasard vers un Ctat hautement orient6 avec une augmentation du nombre des conformbr...

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“…The orientation of the helical axis of the peptide relative to the lipid multilayers was assessed by placing a gold wire grid polarizer (Perkin-Elmer) in the infrared beam paralIeI and perpendicular to the ATR crystal surface with oriented lipid-peptide film. Acyl chain orientations for lipid-peptide films spread onto the germanium substrate were estimated from polarization measurements of the CH2 asymmetric stretching frequency 2,850 cm" (Okamura et al, 1990). The dichroic ratio (RATR), an index of the mean acyl chain orientation in the film, was determined by the ratio of the absorption of linearly polarized light parallel (All) and perpendicular (A,) to the plane of incidence (RATR = Al/Al).…”

Section: Ftir Spectroscopymentioning

confidence: 99%

Conformation and molecular topography of the N‐terminal segment of surfactant protein B in structure‐promoting environments

et al. 1996

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Although the effects of surfactant protein B (SP-B) on lipid surface activity in vitro and in vivo are well known, the relationship between molecular structure and function is still not fully understood. To further characterize protein structure-activity correlations, we have used physical techniques to study conformation, orientation, and molecular topography of N-terminal SP-B peptides in lipids and structure-promoting environments. Fourier transform infrared (FTIR) and CD measurements of SP-B1_25 (residues 1-25) in methanol, SDS micelles, egg yolk lecithin (EYL) liposomes, and surfactant lipids indicate the peptide has a dominant helical content, with minor turn and disordered components. Polarized FTIR studies of SP-B,-25 indicate the long molecular axis lies at an oblique angle to the surface of lipid films. Truncated peptides were similarly examined to assign more accurately the discrete conformations within the SP-B,_,, sequence. Residues Cys-8-Gly-25 are largely a-helix in methanol, whereas the N-terminal segment Phe-1-Cys-8 had turn and helical propensities. Addition of SP-Bl-25 spin-labeled at the N-terminal Phe (i.e., SP-BT_25) to SDS, EYL, or surfactant lipids yielded electron spin resonance spectra that reflect peptide bound to lipids, but retaining considerable mobility. The absence of characteristic radical broadening indicates that SP-B1-25 is minimally aggregated when it interacts with these lipids. Further, the high polarity of SP-BI-25 argues that the reporter on Phe-1 resides in the headgroup of the lipid dispersions. The blue-shift in the endogenous fluorescence of Trp-9 near the N-terminus of SP-B1-25 suggests that this residue also lies near the lipid headgroup. A summary model based on the above physical experiments is presented for SP-BI-2S interacting with lipids.

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Orientation studies of hydrated dipalmitoylphosphatidylcholine multibilayers by polarized FTIR-ATR spectroscopy

Cited by 70 publications

References 24 publications

Conformation of the synaptobrevin transmembrane domain

Conformation of the synaptobrevin transmembrane domain

Molecular orientation in thin Langmuir–Blodgett films of dipalmitoylphosphatidylcholine as studied by FTIR transmission and reflection–absorption spectroscopy

Conformation and molecular topography of the N‐terminal segment of surfactant protein B in structure‐promoting environments

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