1Acid Glycoproteinbased Stationary Phase

AGP is the major plasma protein responsible for the protein binding of basic drugs. A variety of cationic, anionic and uncharged compounds can be resolved using this stationary phase. Cationic compounds resolved include ^-blockers such as alprenolol, ox-prenolol, propranolol, metoprolol and pindolol and histamine antagonists such as chlorpheniramine and dimethindene. Figure 7 shows enantioseparations of metoprolol and pindolol on an AGP-based column. Anionic compounds resolved include 2-arylpropionic acid derivatives such as fenoprofen, ibuprofen and naproxen. As described above, separation of enantio-mers is optimized by changing eluent pH, and the type and content of the uncharged organic modifier. However, cationic modifiers such as N,N-dimethyl-octylamine and tetrabutylammonium bromide and anionic modifiers such as octanoic acid and butylic acid can be used effectively with AGP-based materials. An ion-pairing modifier, N,N-dimethyloctyl-amine, in the eluent gives a large increase in enan-tioselectivity of racemic acid, naproxen, on an AGP-

based stationary phase, where the retention factor of the second-eluted enantiomer is increased drastically. This is due to an allosteric interaction in which the affinity of the protein for the enantiomer is increased by the addition of the modifier.

AGP consists of a protein domain and sugar moieties, both of which have chiral components. It was thought that drug binding to AGP occurred at a single hydrophobic pocket or cleft within the protein domain of the molecule. However, the role of sugar moieties on enantioselective binding by AGP has not been investigated. It has been reported that sialic acid residues influence the enantioselective binding of basic drugs in different ways. They are not involved in the enantioselective verapamil-AGP binding. On the other hand, they participate in the binding of (S)-propranolol but not of (-R)-propranolol. Further studies are required to clarify the role of sugar moieties in chiral recognition and the chiral recognition mechanism of AGP.

Solar Panel Basics

Solar Panel Basics

Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.

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