Isoelectric peptide

Properties and Structure. a -Acid glycoprotein (a -AGP) has a molecular mass of about 41,000 and consists of a peptide chain having 181 amino acid residues and five carbohydrate units (14,15). Two cystine disulfide cross-linkages connect residues 5 and 147 and residues 72 and 164. The carbohydrate units comprise 45% of the molecule and contain siaUc acid, hexosamine, and neutral hexoses. In phosphate buffer the isoelectric point of the... 

Thomson MOW Click Organic Interactive to learn to estimate isoelectric points for simple amino acids and peptides. 

When the log /J/pH measurement of a peptide is performed by the shake-flask or the partition chromatography method (using hydrophilic buffers to control pH), usually the shape of the curve is that of a parabola (see Ref. 371 and Fig. 1 in Ref. 282), where the maximum log I) value corresponds to the pH at the isoelectric point (near pH 5-6). Surprisingly, when the potentiometric method is used to characterize the same peptide [275], the curve produced is a step function, as indicated by the thick line in Fig. 4.5 for dipeptide Trp-Phe. 

An important quantity characterizing the amino acids, peptides and proteins is the isoelectric point, which is the value of pH at which the ampholytes do not migrate in an electrical field. This occurs when... 

Cargile, B. J., Stephenson, J.L., Jr. (2004). An alternative to tandem mass spectrometry isoelectric point and accurate mass for the identification of peptides. Anal. Chem. 76, 267-275. 

Shimura, K., Kamiya, K., Matsumoto, H., Kasai, K. (2002). Fluorescence-labeled peptide pi markers for capillary isoelectric focusing. Anal. Chem. 74, 1046-1053. 

Ruchel, R. (1977). Two-dimensional micro-separation technique for proteins and peptides, combining isoelectric focusing and gel gradient electrophoresis. J. Chromatogr. 132, 451 168. 

Mao, Y., Zhang, X.M. (2003). Comprehensive two-dimensional separation system hy coupling capillary reverse-phase liquid chromatography to capillary isoelectric focusing for peptide and protein mapping with laser-induced fluorescence detection. Electrophoresis 24, 3289-3295. 

Most previous work on rat MUPs has been conducted with inbred or relatively inbred laboratory rat strains that are likely to exhibit considerably reduced phenotypic variation relative to the wild population, as we see in mice. As an initial exploration of MUP expression, we analysed urine from nine wild-caught male rats captured from several different populations in northern UK by isoelectric focusing electrophoresis (IEF). The protein banding pattern was very similar between individuals, consisting of two major and several minor bands. Peptide mass... 

What charge would a peptide with an isoelectric point of 7.2 have at pH 8.9 ... 

It should also be noted that new sample probes can generate additions to the sample information queries asked of the user at the beginning of the "probe session." Thus, protein probes required the addition of queries regarding molecular weight, isoelectric point and whether biological activity is to be preserved in the chromatographic step. These questions are triggered only if the user specifies the sample as a peptide or protein in answer to the initial sample questions. Also, once the sample is specified as a protein, the question as to the pKa or pKb of the... 

Righetti, P. G., Gelfi, C., Perego, M., Stoyanov, A. V., and Bossi, A. (1997). Capillary zone electrophoresis of oligonucleotides and peptides in isoelectric buffers theory and methodology. Electrophoresis 18, 2145-2153. 

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