Bilayer crystal structure

We wish to express our appreciation to J. Daly, NIH, for generously supplying the batrachotoxin essential for the bilayer experiments to S. D. Darling, University of Akron, for his work on the crystal structures of C2 and C4 and to T. Chambers, FDA, for molecular graphics. 

We note here that all the information presently available on high molecular weight polymer crystal structures is compatible with the bundle model. While very nearly all crystalline polymer polymorphs involve all-parallel chain arrangements, even the only known exception, namely y-iPP [104,105], where chains oriented at 80° to each other coexist, is characterized by bilayers of parallel chains with opposite orientation. This structure is thus easily compatible with crystallization mechanisms involving deposition of bundles of 5-10 antiparallel stems on the growing crystal surface. Also the preferred growth... 

Atomic force microscopy (AFM) can be used to obtain high-resolution imagery of molecular orientation and ordering for materials adsorbed onto substrates. Early AFM studies on gluconamides were hampered by the tendency of the fibers to unravel on substrates forming bilayer sheets.41 These layers showed the head-to-tail packing of a monolayer which is similar to the crystal structure reported for anhydrous gluconamides.38 A procedure to retain the fiber networks on surfaces with the addition of a small fraction of... 

The crystal structure can be considered as a structure regularly stacked with bimolecular layers along the a-axis. Within the bimolecular layer, two molecules related by inversion symmetry face each other in the tail-to-tail fashion with their molecular axes inclined by about 26° to the bilayer surface. This inclination enables the head-to-tail arrangement of azobenzene chromophores as expected from the spectroscopic study. 

Although varying considerably in molecular size, any GPCR polypeptide sequence contains seven hydrophobic a-helices that span the lipid bilayer and dictate the typical macromolecule architecture. Seven transmembrane domains bundled up to form a polar internal tunnel and expose the N-terminus and three interconnecting loops, to the exterior, and the C-terminus with a matching number of loops, to the interior of the cell [1-3]. This structural information was recently confirmed by the resolution of the crystal structure of rhodopsin [4,5]. 

Ogg, D., Elleby, B., Norstrom, C., Stelans-son, K., Abrahmsen, L., Oppermann, U., Svensson, S. (2005) The crystal structure of guinea pig llfl-hydroxysteroid dehydrogenase type 1 provides a model for enzyme-lipid bilayer interactions. J Biol Chem 280, 3789-3794. 

Fig. 83. (a) Schematic electronic structure of a ion in a MnOg octahedron with IT distortion. The in-plane eg band in the layered manganite shows a different band dispersion and bandwidth depending on the respective orbital states, (b) Doping-level dependence of lattice distortion at room temperature in La2 2jSr +2jMii207. Thick arrows on the right hand of respective crystal structures indicate the spin structures within a bilayer unit at low temperatures. After Kimura et al. (1998). 

DCA is the first bile acid whose inclusion ability was confirmed in the crystalline state. During the last century many research groups dealt with the inclusion compounds of DCA with various guest molecules, such as aliphatic, aromatic and alicyclic hydrocarbons, alcohols, ketones, fatty acids, esters, ethers, nitriles, peroxides and amines, and so on [2], In 1972, Craven and DeTitta first reported the exact crystal structure of DCA with acetic acid [3], Subsequent crystallographic studies made clear that most of DCA inclusion crystals have bilayer... 

In contrast to DCA, there were no detailed reports on the inclusion abilities of its related compounds. There are only a few descriptions of apocholic acid [5] (ACA, see later, in Figure 5) with a very similar bilayer structure to DCA. In 1986, Miyata and Miki et al. discovered lots of inclusion compounds of CA with the similar bilayer structures [6], On the other hand, it took a long time to determine the hexagonal crystal structures of CDCA inclusion compounds, and LCA exhibits no inclusion abilities as yet. In this way, it was confirmed that an increase or decrease of only one atom brings about completely different inclusion behaviors and crystal structures. This fascinating fact has given us adequate and continuous motivation to investigate the inclusion compounds of bile acid derivatives. 

Mylius, in 1887 [7] was the first to report that CA will include some alcohols. One hundred years later Johnson and Schaefer found that it possessed a crossing type of crystal structure [8], whereas Miki et al. discovered a bilayer structure [6b], Extensive studies made it clear that CA forms various host frameworks to include a wide variety of organic guest compounds. For example, small... 

Figure 7 Crystal structures and hydrogen-bonding networks of BHCA (a) bilayer structure, (b) crossing structure, and epibile acids with 2-pentanol, (c) 3EDCA, and (d) 3ECA.

Figure 10 Crystal structures of CA with acetic acid (a) 1 1 crossing structure and (b) 1 2 bilayer structure. Crystal structures of CAM with acetonitrile and water (c) 1 1 1 triangular structure and (d) 1 1 2 bilayer structure. Open, gray and filled circles represent carbon, nitrogen and oxygen atoms, respectively. Hydrogen atoms are omitted for clarity.

Another intercalation was observed in the inclusion crystals of CA with n-propylbenzene [32c], Heat treatment of a 1 1 molar ratio of CA with n-propyl-benzene gave intermediate inclusion crystals with the same guests at 2 1 stoichiometry. Comparison of both crystal structures by powder X-ray diffraction indicated that the bilayers slide past each other on the lipophilic sides by ca. 4.5 A in the horizontal direction. The 2 1 crystals can be returned to the original crystal (1 1) by soaking them in the liquid n-propy I benzene, and the bilayer can slide back to the initial position without changing to the amorphous state. 

The presence of. vyn-postioned hydroxyl groups on the C3 and C5 of the N-octyl-D-gulon-(35a), altron-(37a), allon-(36a), and idon-(38a) amides, makes these compounds water-soluble and therefore does not allow the formation of aggregates. And induced a bent. This bent does not allow the formation of any regular chain amide hydrogen bonds due to the excessive hydration. The crystal structures of D-Gul-8 35a164 and D-Tal-8 34a165 have been reported and shown to contain tail-to-tail bilayers. 

The packing pattern of BABI is mostly conserved in PhBABI, despite the substantial difference in their lengths, because they form different 7T-stacking cant angles relative to the direction of their 7T-stack axes, and because void spaces between the PhBABI molecules in the lattice are occupied by solvent molecules that are probably important filler to help bilayers to form (Fig. 26). Even the thickness of a bilayer from aminoxyl chain to aminoxyl chain is nearly the same in the two - 11.1 A in BABI and 11.2 A in PhBABI, both room-temperature crystal structures. The driving force of the BIm unit for hydrogen-bonded chain assembly is clearly strong. 

Fig. 4.7 Location of amlo-dipine within the membrane bilayer derived from its cen-ter-of-mass location and crystal structure. Its location near the hydrocarbon corewater interface can facilitate both a hydrophobic interaction with the phospholipid acyl chain and an ionic interaction between the protonat-ed amino function of the drug and the charged anionic oxygen of the phosphate head group. Nimodipine structure and location are consistent with only hydrophobic interactions with the phospholipid acyl chains. No electrostatic interaction with the head groups of PI was noted. (Reprinted from Fig. 2 of ref. 95 with permission from the American Chemical Society.)...

Small-angle X-ray diffraction was used to identify the time-averaged location of amiodarone in a synthetic lipid bilayer. The drug was located about 6 A from the center of the lipid bilayer (Figure 4.13) [125, 126]. A dielectric constant of k = 2, which is similar to that of the bilayer hydrocarbon region, was used to calculate the minimum energy conformation of amiodarone bound to the membrane. The studies were performed below the thermal phase transition and at relatively low hydration of lipid. The calculated conformation differed from that of the crystal structure of amiodarone. Even though the specific steric effects of the lipid acyl chains on the confor-... 

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