Serine isoelectric point

Several extracellular proteases have been purified and characterized from entomopathogenic fungi. Molecular weights, isoelectric points and specific inhibitors of some of these enzymes are summarized in Table 1. The majority of them belong to the family of serine proteases. 

Figure 2.13 shows the fractional equilibrium concentration curves for serine (pKal = 2.2 and pKa2 = 9.22). One can use the same equations, Equation (2.107a), Equation (2.107b), and Equation (2.107c), if H2A, HA, and A-2 are substituted by HY+, HY1, and Y, respectively. The isoelectric point (IEP) is the pH at which the amino acid does not move in an electrical field or possesses a net charge of zero. It is obtained from (pKal + pKa2). 

The properties of the isolated peptides were quite similar in nature, whereby each peptide consisted of 12 amino acids in length and possessed a munber of residues with functional side groups that could stabilize nanoclusters. In many instances, these side chains were the hydroxyl-terminated side chains of serine, threonine, and tyrosine. In two of the peptides (AG3 and AG4), the location of the hydroxylated amino acids was conserved within two of the peptides. Similarly, one proline amino acid was conserved throughout all three of the sequences. Upon incubating each peptide in a solution of silver nitrate with no exogenous reductant, a clearly observable plasmon resonance peak arose at 440 nm for AG3 and AG4, but not with AG5. The peak was quite broad, indicative of a disperse size and shape distribution. The main difference between the active peptides and inactive AG5 was an overall basic isoelectric point for AGS The assays were performed at neutral conditions which would modulate the side-chain dynamics under acidic or basic conditions. 

PSA is a single-chain glycoprotein that is 7% carbohydrate. It has 237 amino acid residues and four carbohydrate side chains with linkages at amino acid 45 (asparagine), 69 (serine), 70 (threonine), and 71 (serine). The N-terminal amino acid is isoleucine, and the C-terminal residue is proline. Its MW is 28,430, and it has isoelectric points from 6.8 to 7.2 because of its various isoforms. The three-dimensional structure and the antigenic domain of PSA have been characterized. ... 

The chiral polythiophene, poly(3- (.S )-5-amino-5-carboxyl-3-oxapcntyl -2,5-thiophenylene) hydrochloride, l-POWT, ring-functionalized with the amino acid L-serine, has been synthesized by Inganas and coworkers,69,168 and was found to exhibit pH-dependent UV-visible, fluorescence emission, and CD spectra. At a pH equal to the isoelectric point of the amino acid, the poly thiophene chains separate and adopt a nonplanar right-handed helical conformation. Increasing the pH leads to a more planar conformation of the backbone and aggregation of the polymer chains. 

Mathematical Galculate the isoelectric point of each of the following amino acids glutamic acid, serine, histidine, lysine, tyrosine, and arginine. 

Abramson et al. (19646) have prepared by ultrasonication optically clear aqueous dispersions of phosphatidyl serine (PS). Infrared and titration data indicated that at the isoelectric point the molecule is a dipolar ion of phosphate and amino groups. They also found evidence for the existence of the following three forms isoelectric or acidic (XXX), HPS monosodium salt (XXXI), NaPS and disodium salt (XXXII),... 

The characteristics of an extracellular mcl-PHA depolymerase purified from the marine isolate Pseudomonas luteola M13-4 have been reported by Rhee et al. (2006). This enzyme is similar to Pseudomonas alcaligenes LB 19 (Kim et al. 2002) but is different from poly(HB-co-HV) (PHBV) depolymerase of Xanthomonas sp JS02 (Kim et al. 2000a, b, c) the molecular mass is 28 kDa, the isoelectric point is 6.0 with a reactivity optimum at pH 10 and 40°C. Serine residues seem to play an important role in the hydrolysis reaction by analogy with P. alcaligenes LB 19. PHO has been totally degraded polyhydroxyhexanoate (PHH) and a copolymer of (PHB-co-60%HV) have been partially hydrolyzed. 

Bhushan and Ali [21] used optically pure (-) brucine as a chiral selector they selected oL-amino acids which have isoelectric point below pH 7 and carried out separation on stationary phase where pH was 7.1-7.2 (during preparation of the plates they added the silica gel slurry 0.1 N NaOH). In such a case, amino acids existed as an anion and interacted with the basic brucine. Selectivity of the used system for some amino acids (isoleucine, leucine, and alanine) enantiomers was very high h/ F for D,L-serine was 12 and 50, respectively. 

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