Proteins charge characteristics

Isoelectric focusing also finds application in analysing the stability of biopharmaceuticals over the course of their shelf life. Repeat analysis of samples over time will detect deamidation or other degradative processes that alter protein charge characteristics. 

The adjuvanticity of liposomes depends upon their composition, number of layers and charge characteristics. They act as effective adjuvants for both protein- and carbohydrate-based antigens and help stimulate both B- and T-cell responses. Their likely mode of action includes depot formation, but they also possibly increase/enhance antigen presentation to macrophages. The exact molecular mechanism(s) by which they stimulate a T-cell response remains to be elucidated,... 

Part of the reason that ion exchange is so versatile is that proteins are amphoteric their charge characteristics vary according to the pH environment. In addition, each species of protein responds differently, so that a group of proteins eluting in the order A,B,C at one pH may elute in a different order or with different... 

Isoelectric Focusing This is an electrophoretic method in which the proteins are separated based on their charge characteristics. This is accomplished by the proteins moving through a medium with a pH gradient. 

What physical properties are conferred on biological membranes by phospholipids How can the charge characteristics of the phospholipids affect binding of peripheral proteins to the membrane What role... 

Another effect related to the charge characteristics of AVE is the apparent absence of cytotoxicity as indicated by complete absence of cell death. This has been shown in a concentration-dependent (Figure 4) and a time-dependent fashion (Figure 5). The cellular protein concentration curve remains flat over a range of 5-40 4g DNA, corresponding to 15-120 4g of total lipid (Figure 4). No rounded-up or floating cells were found by microscopic observation at any concentration or time point. 

HI Nishida, H Arai, T Nishida. Cholesterol ester transfer mediated by lipid transfer protein as influenced by changes in the charge characteristics of plasma lipoproteins. J Biol Chem 268 16352-16360, 1993. 

The peptides, which are composed of only a few amino acids, exhibit predictable behavior in CZE in that their mobility (electrophoretic migration) can be predicted on the basis of their size (mass) and their charge characteristics. The charge of such peptides can be predicted from the pKa values of individual amino acids contained in them. For larger peptides and proteins, the calculation of charge based on ionization constant is not trivial and can not be easily calculated based on the pKas of the free amino aids. Besides the mass-to-charge ratio, the other factors that affect mobility are hydrophobic-ity, primary sequence, conformational difference, and the chirality of amino acids. This point has been demonstrated by an investigation on several nonapeptides of identical composition but with different primary sequences ... 

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