Other Proteinbased Stationary Phases

A number of further minor protein-based stationary phases for HPLC, based on avidin, ovotransferrin and flavoprotein, have been described. Avidin, a basic protein, strongly binds biotin with an association constant of 1015molL_1. Avidin-based stationary phase shows excellent chiral recognition ability for 2-arylpropionic acid derivatives such as ibuprofen, ketoprofen, flurbiprofen, pranoprofen and feno-profen. Figure 10 shows enantioseparations of ibuprofen, ketoprofen and flurbiprofen on an avidin-based column. A biotin-bound avidin stationary phase does not exhibit chiral recognition ability, because the biotin modifies the structure of the avidin.

Ovotransferrin is labile to heat and acid, but it seems that it is stable to heat when combined with metal ions such as iron, copper, manganese and zinc. Ovotransferrin is further stabilized by conjugation to silica gel as a chiral stationary phase, and ovo-transferrin-based stationary phases have been used for the separation of a basic compound, azelastine.

Flavoprotein, the riboflavin-binding protein, in egg whites and yolks has been introduced as a chiral stationary phase for HPLC. Egg white and yolk flavoproteins appear to be the product of the same gene but to have undergone different post-transla-tional modifications. The amino acid sequence is the same but the yolk flavoprotein is between 11 and 13

amino acids shorter. There are differences in the carbohydrate links between flavoproteins from egg yolks and whites. Chiral stationary phases based on flavoproteins from egg whites and yolks exhibit chiral recognition abilities for uncharged, anionic and cationic compounds. There is no evidence whether the drugs interact with the riboflavin-binding site or not.

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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