Cholesterol groups

CHESG Cholesterol group-modified enzymatically synthesized glycogen... 

The study of the reasons for the formation of intramolecular structures reveals that the enhanced interaction of cholesterol groups occuring on cooling is very important. The dilution of the sequence of cholesterol-containing monomeric units by butylmethacrylate units (copolymers of ChMA-11 with butylmethacrylate) leads gradually to the degeneration of the conformational transition (Fig. 31, curves 3-5). 

The decisive role of cholesterol groups in the process of compact globular structure formation is confirmed by the temperature dependence of xw for solutions of PCMA-11... 

The fragments of macromolecules with ordered cholesterol group sequences, that are formed in bad solvents, may serve as nuclei of supermolecular order in films, obtained from these solvents. Structural and optical studies have shown that PChMA-11 films produced by solvent evaporation display different properties those obtained from chloroform and toluene solutions (small relaxation times, see Table 17) are optically isotropic, and those obtained from heptane solutions (large relaxation times, see Table 17) are optically anisotropic, what reflects the differences in conformational state of polymeric chains in these films. Contrary to the optically isotropic films, a high degree of side branch ordering characterizes optically anisotropic films, which is confirmed by X-ray studies. The observed difference of LC polymer structure in the bulk is thus the consequence of their different conformational state in solution this reveals some possibilities for the control of LC polymer structure at the initial steps of mesophase nucleation in solutions. 

The hydrophobic lipid anchors can be either fatty chains (e.g. derived from oleic or myristic acid) or a cholesterol group. Lipid anchors help in forming liposomes (or micellar structures) and determine the physical properties of a lipid bilayer, such as membrane rigidity and rate of lipid exchange between lipid... 

Values (mean SE) refer to measurements obtained at the end of the diet period. Values at the onset of the period, indicated in parentheses, are given only if they differed from the subsequent values (p<. 05, paired t-test). Simultaneous comparisons between the four groups (analysis of variance, see Methods) revealed significant differences only between cholesterol groups and standard diet groups (values with p <. 001). 

Ingallinella P, Bianchi E, Ladwa NA et al (2009) Addition of a cholesterol group to an HIV-1 peptide fusion inhibitor dramatically increases its antiviral potency. Proc Natl Acad Sci USA 106 5801-5806... 

Cholesteryl-cyclodextrins Cholesteryl-CyDs have been designed, and are obtained by grafting a cholesterol group onto a CyD. Indeed, cholesterol is described as a phospholipid-bilayer stabilizer and the cholesterol part of cholesteryl-CyDs can enter this bilayer whereas CyD, the hydrophilic part, is located in the internal and external aqueous media between bilayers [90, 91]. 

Lopez-Quintela et al. concluded that in case of large chain lengths the behavior was dominated by the EO chain, while for n < 10 the rigidity of the cholesterol group dominated, imposing its properties on the surfactants [32]. 

WAXS measurements demonstrated that the two lateral distances for the long-chain surfactants were similar to those of other polyoxyethylene surfactants (3.87 and 4.72A). Thus, the authors concluded that the molecules were packed in the solid state similar to other polyoxyethylenes and that the thermodynamic behavior of the surfactants was mainly governed by the polyoxyethylene chain. Since the lateral distances among the polyoxyethylene chains are smaller than in the cholesterol, the polyoxyethylene chains could be more closely packed in the soUd state only by an antiparallel arrangement, in order that the more voluminous cholesterol moieties do not interfere with each other. However, when the chain was reduced, below n = 10, the cholesterol group rigidity was pronounced, the lateral distances became similar to the lateral distances in the cholesterol, and transformation into a liquid-crystalline phase occurred [32]. 

To interprete these X-ray spacings, let us first examine the structure of model compounds PMAA-n and PMMAA-n. The macromolecules of these polymers have a chemical structure similar to that of Pc5iMAA-n with the difference that they do not contain cholesterol groups in the side chains. 

Although the structure of cholesterol-containing polsrmers is not yet completely understood, there is no doubt that the liquid crystalline properties exhibited by these polymers are due to a particular oirder in the arrangement of cholesterol groups. This is corroborated by the results of studying the structure and optical properties of model compounds not containing cholesterol. The above-mentioned PMAA-n and PMMAA-n are optically isotropic in all three physical states vitrified, elastic and viscous. 

We have already considered the structure and properties of polymers containing cholesterol in such monomer unit. It is also of interest to examine the structure and properties of polymers in which the content of cholesterol groups can be varied, i,e, copolymers, Given in Table V are transition temperatures for some copolymers that we have synthesized. 

Figure 5 (a and b) Chemical structure of the sodium salt of several bile acids 1 cholic acid, 2 chenodeoxycholate, 3 deoxychoUc acid, 4 glycocholic acid, 5 taurochoUc acid, and 6 tauro deoxychoUc acid, (c) Structures of micelles from choUc acid derivatives, proposed by Small and coworkers. Two or four molecules assemble because of hydrophobic interactions between the cholesterol groups. The hydroxyl groups (black dots on cholesterol) and the carboxylic acids side group shield the hydrophobic domain from water. (Refs. 22-24 for cmcs and Ref. 16 for aggregation numbers.) (Reproduced with permission from Ref. 21. Indian Academy of Sciences, 2004.)... 

---