Polarization, proteins

Landau E M, Rummel G, Cowan-Jacob S W and Rosenbusch J P 1997 Crystallization of a polar protein and small molecules from the aqueous compartment of lipidic cubic phases J. Phys. Chem. B 101 1935-7... 

Hung TJ, Kemphues KJ 1999 PAR-6 is a conserved PDZ domain-containing protein that colocalizes with PAR-3 in Caenorhabditit elegant embryos. Development 126 127—135 Izumi Y, Hirose T, Tamai Y et al 1998 An atypical PKC directly associates and colocalizes at the epithelial tight junction with ASIP, a mammalian homologue of Caenorhabditit elegant polarity protein PAR-3. J Cell Biol 143 95-106... 

Adsorption chromatography relies on the different affinity of components of a mixture for a liquid moving phase and a solid stationary phase. The separation mechanism depends upon differences in polarity between the different feed components. The more polar a molecule, the more strongly it will be adsorbed by a polar stationary phase (Varki et al. 1999). Similarly, the more nonpolar a molecule, the more strongly it will be adsorbed by nonpolar stationary phase. It is often employed for relatively nonpolar, hydrophobic materials so that the solvent tends to be nonpolar while the stationary phase is polar. Proteins have a high affinity to polar chromatographic media and the recovery of the sample is usually difficult. Therefore, this method is not commonly used to purify and characterize proteins. 

A high complementarity of the surface properties. Lipophilic parts of the ligands are most frequently found to be in contact with lipophilic parts of the protein. Polar groups are usually paired with suitable polar protein groups to form hydrogen bonds or ionic interactions. 

Tables IV—VI, from Blake et al. (1983), describe the contacts made by the ordered water. The waters are nearly all bonded to polar protein atoms. The infrequent interaction with amide NH reflects the inaccessibility of these atoms. Charged side chains generally bind two ordered waters polar groups, one.

Water interacts principally with polar protein surface groups (ca 1 water/ polar site)... 

Triacylglycerols are highly concentrated stores of metaholic energy because they are reduced and anhydrous. The yield from the complete oxidation of fatty acids is about 9 kcal g" (38 kJ g- ), in contrast with about 4 kcal g l (17 kJ g-i) for carbohydrates and proteins. The basis of this large difference in caloric yield is that fatty acids are much more reduced. Furthermore, triacylglycerols are nonpolar, and so they are stored in a nearly anhydrous form, whereas much more polar proteins and carbohydrates are more highly hydrated. In fact, 1 g of dry glycogen binds about 2 g of water. 

Hattendorf DA, Andreeva A, Gangar A et al Structure of the yeast polarity protein Sro7 reveals a SNARE regulatory mechanism. Nature 2007 446 567-571. 

So far, it is not fully understood how the asymmetric PAR protein distribution is connected with the reorganization of the actomyosin cortex. Here, we have analyzed the polarity protein PAR-2 and a component of the actomyosin cortex, the non-muscle myosin NMY-2, in vivo with standard and scanning FCS inside the C3ffosol and on the cortex of C. elegans embryos. 

PAR-2 seems to be uncoupled from movement of NMY-2, a member of the actomyosin cortex, as observed in sFCS measurements on the cortex. Further investigations into the different cortical elements and polarity proteins are necessary to elude the mechanisms of asymmetric cell division in developing C. elegans embryos. FCS and sFCS are two techniques capable of investigating the dynamics of the involved proteins, providing a complementary approach to existing techniques. 

The water-mediated interactions may also be of considerable importance. In the activated form the lid occupies a new position on the surface of the molecule, some 8 A away from the original location. This deep surface depression extends 10 A into the molecule and is filled in the native enzyme by 18 water molecules, half of which are direcdy hydrogen bonded to the polar protein groups. During the conformational change ail but three of these solvent molecules are expelled. In the lipase-inhibitor complex these three molecules become buried and mediate the polar contacts formed primarily by Asn-87. 

Rongo C, Whitfield CW, Rodal A, Kim SK, Kaplan JM. 1998. LIN-10 is a shared component of the polarized protein localization pathways in neurons and epithelia. Cell 94 751-59... 

The Role of Solvent in Polar Protein-Ligand Interactions... 

Organic solvents. Water-soluble organic solvents such as ethanol interfere with hydrophobic interactions because they interact with nonpolar R groups and form hydrogen bonds with water and polar protein groups. Nonpolar solvents also disrupt hydrophobic interactions. 

The interaction of /3-casein molecules with lecithin monolayers is governed by the surface activity (hydrophobicity) of the macromolecule. Hydrophobicity does not guarantee interaction of a protein with lecithin in dispersion (22), but it favors penetration of proteins into monolayers at the air-water interface. The whole molecule seems to penetrate in the case of /3-casein (Figure 7) this leads to the compression of the lipid molecules and perhaps the formation of a layer of relatively restricted lecithin molecules around the periphery of the protein molecules. The situation is quite different for a very polar protein such as lysozyme where... 

It, therefore, seems clear that the molecular modification of progesterone, altering its solubility, distribution ratio, polarity, protein- binding characteristics, steric requirements, crystalline structure, and rate of metabolism (as well as the nature of the metabolic products themselves), would alter some of the properties of progesterone, eliminate some, and introduce new and unexpected properties, many of which may not be evident even after extensive animal studies. 

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