Amino acids charge characteristics

The choice of a suitable immobilization method for a given enzyme and appHcation is based on a number of considerations including previous experience, new experiments, enzyme cost and productivity, process demands, chemical and physical stabiHty of the support, approval and safety issues regarding support, and chemicals used. Enzyme characteristics that greatly influence the approach include intra- or extraceUular location size surface properties, eg, charge/pl, lysine content, polarity, and carbohydrate and active site, eg, amino acids or cofactors. The size, charge, and polarity of the substrate should also be considered. 

Physical-chemical characteristics of prion proteins are evident after assigning different parameters, including hydrophobicity, charge, and molecular weight to the amino acid residues (Inouye and Kirschner, 1991, 1998) (Table II, Fig. 5). The sequences among different animals... 

A common characteristic of CPPs is that they contain a minimal motif of less than 20 amino acids rich in basic residues. There are two subclasses of CPPs the first class consists of amphipathic helical peptides, where lysine is the predominant supplier of the positive charge, for example model amphipathic peptide (MAP) and transportan, whereas the second group, which includes TAT and penetratin, is rich in arginine residues (48-60,86). 

Stabilization of a P-hairpin structure can be achieved in two ways, promoting a stable (or restricted) turn structure (as done with mimetics) or linking the two arms either chemically, or, more naturally, by hydrophobic interactions. In an approach to utilizing both methods, a D-Pro-Gly linkage was used to stabilize a left-handed turn (type I or II ) and various charged and hydrophobic residues were used to stabilize the molecule and enhance the interaction between arms. I252"254 Examples of these peptides studied in nonaqueous solution by IR, VCD and NMR spectroscopy exhibit characteristics of well-formed hairpins. 255 Alternatively, in aqueous solution, IR, VCD, and ECD results for related peptides agree with the NMR interpretation of conformations characterized as hairpins stabilized at the turn and frayed at the ends. 256 These latter results also have a qualitative match with theoretical simulations. Recently, examples of hydrophobically stabilized hairpins studied by NMR spectroscopy have avoided use of a nonnatural amino acid. 257,258 ... 

Following extractive deproteinization of the plasma, the amino acids (and their stable-isotope-labeled internal standards) are separated by HPLC and introduced into the mass spectrometer. Electrospray ionization results in the formation of electrically charged molecules, which are separated on the basis of their mass/charge (m/z) ratio in the first quadrupole. Following fragmentation in the collision cell, the characteristic fragment for each amino acid is selected in the second quadrupole. This process is named multiple reaction monitoring. 

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