Molecule cone-shaped

Naturally occurring cyclodextrins and their higher homologues are truncated cone-shape molecules with a hollow, tapered cavity 7.9 A deep... 

Cyclodextrins are hollow, cone-shaped molecules. Their length is 7.9 A and their diameter is 5.7 A (a-CDX), 7.8 A (/i-CDX) and 9.5 A (y-CDX). The primary hydroxyl groups lie on the wide rim and the secondary hydroxyl groups are located on the narrow rim. The interior is a non-polar, hydrophobic cavity. Therefore cyclodextrins normally show their complexing properties for hydrocarbon molecules in very polar solvents, such as water, or dmso. 

This type of stacking of cone-shape molecules has already been proposed for the description of the molecular organisation in the mesophase of some bowlic liquid crystals based on tungsten-oxo calix[4]arenes, 80, 81 [142]. 

Fig. 2 The phase behavior of mixed-chain phosphatidylethanolamine in excess water. At low temperature this lipid exists as crystalline bilayers (the gel or Lq state). With increasing temperature the bilayers undergo a reversible endothermic transition commonly called the bilayer phase transition. The resulting state (the liquid crystalline or L3 state) is composed of fluid bilayers. The lipid hydrocarbon chains are more disordered in fluid bilayers than in crystalline bilayers. This results in more cone-shaped molecules as illustrated in the top of the figure. With further increase in temperature the lipid molecules become still more cone-shaped and their preferred conformation is the inverted hexagonal En state.

Fig. 1.1. Macroscopic polarization in the distorted nematic phase composed of bent-core molecules with transverse electric dipoles or cone-shaped molecules with longitudinal dipoles.

Fig. 37.1 Schematic representation of a macrocyclic amphiphilic molecule (a) and chemical structures of the native caiix[4]arene (b) and resorcin[4]arene (c). The caiix[4]arene macrocycle, composed of four phenolic units, forms a fairly rigid truncated cone-shaped molecule when adequately modified to lock the structure to avoid conformational changes to partial cone conformations. The aromatic alcohol functions are exposed at the narrow rim, and the para phenolic positions at the wide rim. Applying different chemistries, the macrocycle can be selectively modified either on one rim or on the other. The regio-selectivity of the chemical modifications is not restricted to the selection of the modified rim the number and the position within a rim could also be controlled...

Cq is the membrane intrinsic curvature, that is, the curvature of the membrane with zero deformation (e.g., a single layer of cylindrical molecules should have an intrinsic curvature of zero, but cone-shaped molecules will pack two dimensionally to have a curvature with no energy cost, k is the bending modulus, and is known as the saddle-splay modulus. As we can see in Figure 3.10, it is quite possible to have a curved membrane with a mean curvature of zero in the case of saddle-like deformations. Therefore, it becomes clear that to describe the energy cost of a saddle deformation the extra terms are necessary. 

A set of host compounds of considerable current interest are calix(n)arenes [26] and the related resorcarenes [27]. Both sets of compounds form cone-shaped molecules. Calixarenes contain para substituted phenol units connected by methylene bridges. The most common have four, six, or eight phenolic units, and by varying the nature of the substituent group or derivatizing the hydroxyl groups... 

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