Direct observation of the hydrocarbon chain tilt angle in phospholipid bilayers

Stamatoff, J.; Graddick, W.F.; Powers, Linda S.; Moncton, D. E.

doi:10.1016/s0006-3495(79)85289-3

Cited by 49 publications

(29 citation statements)

References 6 publications

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“…Values of W,/, ranging from 5' to 15O are common for the mosaic spread of supported samples measured in studies of biological membranes (18,(24)(25)(26)(27)(28)(29)(30). However, knowing the width at half-height of the distribution is not sufficient to assess the effect of this disorder on the measurements, since the shape of the distribution is also important, as is demonstrated in Table 1.…”

Section: Orientation Measurements Of Phospholipid Bilayersmentioning

confidence: 99%

On the relationship between the order parameter and the shape of orientation distributions

Lafrance¹,

Nabet²,

Prud’homme³

et al. 1995

Can. J. Chem.

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The molecular orientation is generally expressed by an "order parameter," (P,), which depends on both the angular position and the shape of the orientation distribution. This parameter is an average made over all orientations of the structural units studied in a sample and, consequently, a given (P,) value can correspond to different orientation distributions. In this article, model distributions are used to show the relationship between the shape, width, and angular position of the center of the orientation distribution on the (P,) coefficient, for the case where the distribution of the molecular chains exhibits cylindrical symmetry with respect to the reference direction. A significant difference is observed between the order parameters calculated for distributions of Gaussian and Lorentzian shapes with similar width at half-height. The variation of the (P,) coefficient as a function of the width at half-height, W,,,, and of the position of the center of the distribution, 0,, is analyzed. Figures showing the range of W,,,-0, coordinates that can correspond to a given (P,) value are presented. As an example, the influence on the order parameter of the disorder between the different domains of phospholipid samples (mosaic spread) and of the conformational disorder in the acyl chains of these molecules is also studied. This example permits the evaluation of the magnitude of the errors that can be introduced in calculations of the tilt angle of the molecular chains in the case of distributions of finite widths or of bimodal character.Key words: orientation, orientation function, phospholipid bilayers, conformational disorder, mosaic spread.Resume : L'orientation molCculaire est gCnCralement exprimCe par un parambtre d'ordre, (P,), dont la valeur dCpend B la fois de la position angulaire et de la forme de la distribution d'orientation. Ce parambtre d'ordre constitue une moyenne faite sur toutes les orientations des unites structurales CtudiCes dans un Cchantillon et, en constquence, une valeur de (P,) donnCe peut correspondre 2 diffkrentes distributions d'orientation. Des distributions modkles sont utilisCes afin de montrer l'influence de la forme, de la largeur et de la position angulaire du centre de la distribution d'orientation sur le coefficient (P,), pour le cas oh les chaines molCculaires posskdent une symCtrie cylindrique par rapport B la direction de rCfCrence. Une difference significative est observCe entre les parambtres d'ordre calculCs pour des distributions de formes Gaussienne et Lorentzienne de mCme largeur i mi-hauteur. La variation du coefficient (P,) en fonction de la largeur 2 mi-hauteur, WIl2, et de la position du centre de la distribution, €Ic, est analysCe. Des figures montrant la plage de coordonnCes W,,,-0, pouvant correspondre B une valeur de parambtre d'ordre donnCe sont prCsentCes. A titre d'exemple, la variation du coefficient (P,) en fonction du dCsordre entre les diffkrents domaines dlCchantillons de phospholipides et en fonction du dCsordre conformationnel dans les chaines ...

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Section: Orientation Measurements Of Phospholipid Bilayersmentioning

confidence: 99%

On the relationship between the order parameter and the shape of orientation distributions

Lafrance¹,

Nabet²,

Prud’homme³

et al. 1995

Can. J. Chem.

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“…For T < T, and low water concentrations, the equilibrium phases are crystalline-i.e., periodic in.three dimensions. At higher water concentrations, for T < Tc, x-ray diffraction measurements on partially oriented samples indicate rows of scattering along the (h,0,l) axis, h (4.2 A)-1, suggestive ofphases that have well-developed periodicity within each-bilayer but in which successive bilayers are not correlated (19,20). Thus, these phases can be simply interpreted as two-dimensional crystals stacked on top of one another but without any correlation in their relative positions.…”

mentioning

confidence: 99%

“…X-ray diffraction studies of lecithin/water phases have been carried out by a number of workers (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22), and the general properties of the phase diagrams are well established. There exists a transition temperature T, (see, for example, ref.…”

mentioning

confidence: 99%

Hydration of single crystals of dipalmitoylphosphatidylcholine.

Urabe¹,

Asher²,

Pershan³

1981

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

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Optical birefringence and x-ray measurements are reported for single crystals (0.5 mm x 2 mm X 5 ,m) of dipalmitoylphosphatidylcholine as a function of temperature and relative humidity. Large single crystals grown in CHC1jacetone at a low water concentration undergo an irreversible phase transformation at 20'C and 70% relative humidity or at 60°C and 65% relative humidity. After this transformation occurs, the crystals can be made to undergo a reversible transformation into and out of the L. phase. The x-ray-determined mosaic spread in the hydrated crystal is less than :0.04°both above and below.the main transition.A number of different approaches have been made to prepare oriented lecithin/water samples without ever obtaining the same degree of alignment in high-water samples that can be obtained in low-water single crystals (1)(2)(3)(4)(5)(6)(7)(8)(9). In this manuscript, we describe optical and x-ray measurements on monodomain single-crystal samples of dipalmitoylphosphatidylcholine (Pam2PtdCho) that have a mosaic spread of <0.040 at different temperatures and water contents. They were obtained by exposing crystals grown from an acetone/chloroform solution containing <0.5% water at =160C to relative humidities of up to 95% and temperatures up to 75TC. Optical and x-ray studies of the as-grown crystals are described elsewhere (10).X-ray diffraction studies of lecithin/water phases have been carried out by a number of workers (11-22), and the general properties of the phase diagrams are well established. There exists a transition temperature T, (see, for example, ref. 12) that is a monotonically decreasing function of water content such that, for T > Tc, the equilibrium phase consists ofplanar arrays of "fluid bilayers." This is classified as the La phase in the lipid literature and as a smectic A phase in the liquid crystal literature (23). For T < T, and low water concentrations, the equilibrium phases are crystalline-i.e., periodic in.three dimensions. At higher water concentrations, for T < Tc, x-ray diffraction measurements on partially oriented samples indicate rows of scattering along the (h,0,l) axis, h (4.2 A)-1, suggestive ofphases that have well-developed periodicity within each-bilayer but in which successive bilayers are not correlated (19,20). Thus, these phases can be simply interpreted as two-dimensional crystals stacked on top of one another but without any correlation in their relative positions. Although phases with these properties have been discussed in the liquid crystal literature, it is now generally agreed that, if such phases do exist, the periodicity within the bilayer must have a finite correlation length (24,25). This would result in Bragg-like peaks that have shapes different from those oftrue Bragg peaks from three-dimensional crystals.Attempts have been made to observe this phenomenon in thermotropic liquid crystals by using high resolution x-ray diffraction techniques on well-oriented monodomain samples. In one case, a system previously believed to have this property w...

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“…Stamatoff et al [5] determined the tilt angle directly, using free-standing monodomain samples. However, the maximum concentration of water was only 10wt.% and the data were analyzed on the assumption that all tilt directions were equally probable.…”

mentioning

confidence: 99%

“…Apparently the tilt direction was poorly defined in that region. Using there the analysis of Stamatoff et al [5], we derived the same tilt angle as with our method.…”

mentioning

confidence: 99%

Direct X-Ray Study of the Molecular Tilt in Dipalmitoyl Lecithin Bilayers

Hentschel

Hösemann

Helfrich

1980

Zeitschrift Für Naturforschung A

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Direction and angle of molecular tilt in an ordered multilayer system of dipalmitoyl lecithin and water were directly determined by X-ray diffraction as a function of temperature in the gel phase with ca. 20 wt. °/o of water.Early X-ray studies by Levine [1] and Tardien et al. [2] indicated that the hydrocarbon chains are tilted with respect to the layer normal in the gel phase of lecithin-water multilayer systems. Janiak et al.[3] obtained a temperature dependence of the tilt angle. Except the work of Levine, all these experiments were done with dispersions ("powders") and the tilt angle was deduced from the stacking period and the concentration of water. The latter was usually large enough ( > 20% by weight) to keep the pretransition and the main transition at the temperatures characteristic of the single bilayer, i. e. at 34 °C and 43 °C [4]. Stamatoff et al. [5] determined the tilt angle directly, using free-standing monodomain samples. However, the maximum concentration of water was only 10wt.% and the data were analyzed on the assumption that all tilt directions were equally probable.The following investigations were carried out with a "multisandwich" sample consisting of 100 mylar films alternating with multilayer systems of dipalmitoyl lecithin (DPL), both 5 [xm thick. The multisandwich was prepared at 60 °C by compressing a mixture of DPL and 20 wt.% of water. At room temperature the 1 mm high sample was cut into a 1x10 mm strip. Polarizing microscopy showed the bilayers to be well-aligned parallel to the mylar films [6]. The sample was then allowed to stand for 50 h in water-saturated air at 4 °C, sealed in a thin quartz capillary, and finally mounted on the sample holder of an X-ray pinhole camera. When the temperature was changed, measurements were resumed only after at least one day. The diffraction patterns confirmed the good alignment. With horizontal layers there were several orders of small-angle reflections indicating the stacking period along the vertical and wide-angle reflections from the hydrocarbon chain lattice near the equator. A density map of wide angle reflections is given in Figure 1. It suggests that the chains are tilted along one of the basic vectors of a hexagonal lattice (Case I) rather than along one of the bisectors (Case II). The two cases which are the most likely are sketched in Figure 2 The tilt angle derived for Case I, the stacking period, and the spacing of the hydrocarbon chain lattice are 0340-4811 / 80 / 0600-0647 5 01.00/0. -Please order a reprint rather than making your own copy.

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Direct observation of the hydrocarbon chain tilt angle in phospholipid bilayers

Cited by 49 publications

References 6 publications

On the relationship between the order parameter and the shape of orientation distributions

On the relationship between the order parameter and the shape of orientation distributions

Hydration of single crystals of dipalmitoylphosphatidylcholine.

Direct X-Ray Study of the Molecular Tilt in Dipalmitoyl Lecithin Bilayers

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