Theory of periodic structures in lipid bilayer membranes

Falkovitz, Meira S.; Seul, Michael; Frisch, H. L.; McConnell, Harden M.

doi:10.1073/pnas.79.12.3918

Cited by 62 publications

(31 citation statements)

References 25 publications

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“…The formation of the ripple due to the coexistence between these two phases is also proposed in many other experimental and theoretical studies. 4,[19][20][21][22][23] However, since it was found that in the P ′ phase the chains are mainly frozen in an all-trans configuration, 18 the explanation of coexistence is less probable and the difference in the existence of the ripple is attributed to a change in tilt angle and/or elastic properties. [12][13][14][15][16][17] Sengupta et al 17 conclude that the asymmetry of the ripple is not caused by an asymmetry of the height profile, but that the difference in the bilayer thickness is the primary feature.…”

Section: Discussionmentioning

confidence: 99%

“…Also, a combination of these two approaches is possible: it is proposed that competition exists between macroscopic curvature and microscopic properties of the bilayer. 17,23,11 A third approach is the approach in which interbilayer interactions are taken into account in the formation of the ripple. 13 The general picture of the rippled phase is that the shape is an asymmetric sawtooth, with a difference in thickness between the long and the short arm.…”

Section: Discussionmentioning

confidence: 99%

“…Explanations can be found in variations of the thickness of the bilayer due to changes in tilt angles of the hydrophobic chains, [12][13][14][15][16][17][18] and coexistence between the fluid L R phase and the gel phase L ′ . 4,7,[19][20][21][22][23] Also, it is not very clear if the (anomalous) swelling of a membrane is coupled to the formation of the rippled phase 2,24,25 and if the rippled phase only exists in multilayers or if it is also present in a single bilayer system. [26][27][28] Despite all investigations, an explanation of the formation of the rippled phase at a molecular level is still lacking.…”

Section: And References Therein)mentioning

confidence: 99%

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Phase Behavior of Model Lipid Bilayers

2005

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We investigated the phase behavior of double-tail lipids, as a function of temperature, headgroup interaction and tail length. At low values of the head-head repulsion parameter a hh , the bilayer undergoes with increasing temperature the transitions from the subgel phase L c via the flat gel phase L to the fluid phase L R . For higher values of a hh , the transition from the L c to the L R phase occurs via the tilted gel phase L ′ and the rippled phase P ′ . The occurrence of the L ′ phase depends on tail length. We find that the rippled structure (P ′ ) occurs if the headgroups are sufficiently surrounded by water and that the ripple is a coexistence between the L c or L ′ phase and the L R phase. The anomalous swelling, observed at the P ′ f L R transition, is not directly related to the rippled phase, but a consequence of conformational changes of the tails.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: And References Therein)mentioning

confidence: 99%

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Phase Behavior of Model Lipid Bilayers

2005

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“…The wavelengths of these modes would have to be substantially less than the diameter (=300 A) of the small, unilamellar vesicles to account for their similar T, values relative to multilamellar dispersions. It is interesting that certain of the longer wavelength modes may be frozen-out in the Lat > Pa. phase transition of pure Pam2-PtdCho dispersions (41). The relationship of any cooperative bilayer fluctuations to lateral self-diffusion of phospholipids in the liquid crystalline phase of lipid bilayers (15) appears to be uncertain at present-e.g., one might imagine that an upper bound to the lifetimes of the modes might be imposed by lateral diffusion or that diffusion of phospholipids through any relatively long-lived modes set up in the bilaver could affect the T1 relaxation.…”

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confidence: 99%

New view of lipid bilayer dynamics from 2H and 13C NMR relaxation time measurements.

Brown¹,

Ribeiro²,

Williams³

1983

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

147

118

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Natural abundance 13C spin-lattice (TI) relaxation time measurements are reported for unilamellar vesicles of 1,2-dipalmitoylphosphatidylcholine (1,2-dipalmitoyl-sn-glycero-3-phosphocholine), in the liquid crystalline phase, at magnetic field strengths of 1. 40, 1.87, 2.35, 4.23, 7.05, 8.45, and 11.7 tesla (resonance frequencies of 15.0, 20.0, 25.1, 45.3, 75.5, 90.5, and 126 MHz, respectively), and the results are compared to previous 2H T, studies of multilamellar dispersions. For both the 13C and 2H T, studies, a dramatic frequency dependence of the relaxation was observed. At superconducting magnetic field strengths (4.23-11.7 tesla), plots of the 13C TF1 relaxation rates as a function of acyl chain segment position clearly reveal the characteristic "plateau" signature of the liquid crystalline phase, as found previously from 2H NMR studies. The dependence of Tj ' on ordering, determined previously from 2H NMR, and the Tj' dependence on frequency, determined from both '3C and 2H NMR studies, suggest that a unified picture of the bilayer molecular dynamics can be provided by a simple relaxation law of the form T' l ATf + BS2 H W-'1/2. In the above expression, A and B are constants, SCH (=SC-D) is the bond segmental order parameter, and of is the nuclear Larmor frequency. The first (A) term includes contributions from fast, local segmental motions characterized by the effective correlation time Tf, whereas the second (B) term describes slower, collective fluctuations in the local ordering. The value of Tf 10-11 sec, obtained by extrapolating Tj' to infinite frequency, suggests that the segmental microviscosity of the bilayer hydrocarbon region does not differ appreciably from that of the equivalent n-paraffinic liquids of similar chain length.NMR techniques were among the first biophysical methods to be applied to lipid bilayers and biological membranes (1, 2). Perhaps the foremost progress in recent years has been made in applications of NMR lineshape analysis to studies of the molecular ordering and conformations of membranous lipids (3-7). Yet, in spite of early promise (8-11), the interpretation of nuclear spin relaxation experiments has not progressed similarly and, in fact, has remained an outstanding problem in membrane biophysics for more than a decade (cf. ref. 12). The bulk of previous work has involved spin-lattice (TI) relaxation time measurements, which are sensitive to details of the molecular motions in the MHz region. Perhaps the major justification for T, relaxation studies of membranes is their dual character as both solid-like and liquid-like materials. The analogies to simpler liquid crystals point to the necessity of obtaining both static and dynamic information in defining these systems and of distinguishing membranes from other classes of biological macromolecules, such as the globular and fibrous proteins and the nucleic acids. These latter biopolymers, while also rich in dvnamic behavior (13,14), appear to have fairly well-defined average structures that can be directly re...

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“…Such discrepancy between the theoretically and directly obtained values may to some degree be due to the assumption of the theoretically analyzed molecular model that all hydrocarbon chains were in solid state, fully extended and tilted to the bilayer normal. From the pervious observations by FALCOVITZ et al (1982) it is clear, however, that certain areas of the phospholipid bilayer, especially those around the peaks and troughs of ripples, consist indeed of hydrocarbon chains in a fluid-like configuration. The theoretically derived values were, consequently, magnified in comparison to the results of direct measurments of the STM images.…”

Section: Discussionmentioning

confidence: 99%