Lipoprotein carriers

Pheromones in urine will suffer degradation, hydrolysis, oxidation, and ultraviolet radiation effects. For example, the (Z)-7-12-acetyl derivative in elephant urine will gradually hydrolyze (Rasmussen, 1988). In this case, the lipoprotein carriers of the elephant acetate may also determine the life time of the signal besides serving to filter and select odorants, confer specificity, and play a critical role in the transport and transfer of an active ligand to the vomeronasal organ (Rasmussen and Schulte, 1998). 

Fig. 3. Reversible membrane association of lipidated proteins (redrawn firom Ref. [11]). (a) Binding of a ligand (shaded circle) to an iV-myristoylated protein triggers a myristoyl switch, (b) Binding of a ligand (shaded oval) to the polybasic motif of a singly lipidated protein reduces the second signal allowing the protein to desorb from membranes, (c) Phosphorylation within the polybasic motif lowers its affinity for anionic phospholipids (electrostatic switch), (d) A prenyl group is sequestered by a binding partner, (e) Lipidated secreted proteins (the star represents a lipid modification cholesterol and/or fatty acid) spread ftom their source by binding to lipoprotein carriers.

The biocompatibility of PHAs originates from the fact that some monomers incorporated into the polymer chain occur naturally in the human body. The monomer (i )-3-hydroxybutyric acid is a normal metabohte found in human blood. This hydroxy acid is present at concentrations of 3 10 mg per 100 ml blood in healthy adults. Also low molecular weight PHAs are found com-plexed to other cellular macromolecules - hence they are called complexed PHAs (cPHAs). For example, cPHAs have been found in human tissues complexed with low-density lipoproteins, carrier protein albumin and in the potassium channel (KcsA) of Streptomyces lividans. Biocompatibility of PHAs, like any other biomaterial, is dependent on factors such as shape, surface porosity, surface hydrophilicity, surface energy, chemistry of the material and its degradation product. In tissue engineering, it is important that the... 

It is not clear how much of the carotenoid is dropped off each time the lipoprotein carrier is sequestered. 

Kempen et al. [176] synthesized a water-soluble cho-lesteryl-containing trigalactoside, Tris-Gal-Chol (I), which when incorporated in lipoproteins allows the utilization of active receptors for galactose-terminated macromolecules as a trigger for the uptake of lipoproteins. The effect of increasing concentrations of Tris-Gal-Chol on the removal of LDL and HDL from serum and their quantitative recovery in the liver is shown in Fig. 13. These data show that lipoproteins containing Tris-Gal-Chol can be used as a liver-specific drug-carrier system. 

Recent data indicate that SR-BI is a nonspecific receptor for many lipophilic molecules (Lorenzi et al., 2008 Reboul et al., 2007b). Apart from HDLs, rodent SR-BI also binds to LDL, VLDL, acetylated LDL, oxidized LDL, and maleylated bovine serum albumin. SR-BII has a similar ligand specificity and function to that of SR-BI (Webb et al., 1998). However, it has been shown that vitamin E (which like carotenoids is carried in the bloodstream mainly by LDL and HDL) is transported more efficiently into the endothelial cells from HDLs than from LDLs (Balazs et al., 2004 Kaempf-Rotzoll et al., 2003 Mardones and Rigotti, 2004). This is in striking contrast to cholesterol, which is taken up much more efficiently from LDLs than HDLs by the RPE to the retina (Tserentsoodol et al., 2006b). It remains to be shown which lipoproteins are the main carriers for carotenoids transported from blood into the RPE. 

Matsuyama, S., Tajima, T., and Tokuda, H. (1995). A novel periplasmic carrier protein involved in the sorting and transport of Escherichia coft lipoproteins destined for the... 

Most proteins have molecnlar masses between 5000 and 500,000. The hormone insnlin, for example, has a molecular mass of about 6000. Hemoglobin, which carries oxygen around in our bloodstream, has a molecular mass near 68,000. ApoB-100, the protein part of the low-density lipoproteins, generally known as the carrier of bad cholesterol, has a molecnlar mass of 513,000. Nucleic acids have molecular masses that range from a few thonsand to many millions. These are clear examples of big molecnles. 

LDL (low-density lipoprotein) the primary carrier of cholesterol in the blood a positive risk factor for cardiovascular disease bad cholesterol. ... 

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