Isoelectric point calculation

The surface structure and characteristics (density and acidity) of the hydroxyl groups presented in Fig. 13.21 (using CrystalMaker 2.1.1 software) give very useful information to understand the reactivity of the surface of the particles, particularly when adsorption of another complex is desired to synthesize a bimetallic catalyst, or to control the interaction with an oxide carrier (the deposition step). The isoelectric point calculated with the model (5.9) is in fair agreement with the experimental value (4.3). 

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The deduced PGE protein consists of 378 amino acid residues. Based on the known composition of N-termini of PGI and PGII proteins it is assumed that the 39 N-terminal amino acids of PGE form the pre-prosequence of the protein. The molecular weight (35 584) and isoelectric point (pi = 3.6) of mature PGE were calculated based on deduced amino acid sequence. 

The amino acid compositions of each subunit and the native enzyme are shown in Table 5. There are distinct differences between the two subunits. As would be expected from the isoelectric points, the a subunit contains more acidic amino acids than the /3 subunit does, and the /3 subunit contains more basic amino acids than the a subunit does. The amino acid composition of the native enzyme obtained by actual analyses agrees quite well with that calculated from the compositions of the a and /3 subunits, based on the assumed subunit structure of (a ls- These results confirms the assumption that the native enzyme consists of 8 protomers, each of which is composed of a pair of two non-identical subunits (a2fi2)97 I0S. ... 

H. Neutral lysine can be written HL. The other forms of lysine are H3L2, H2L+, and L. The isoelectric point is the pH at which the average charge of lysine is 0. Therefore, at the isoelectric point, 2[H3L2+] + [H2L+] = [L-]. Use this condition to calculate the isoelectric pH of lysine. 

Table IV. Isoelectric Points Assumed for Component Oxides in Calculating Complex Oxide ZPC s ...

The isoelectric point may be conveniently defined as the ZPC expected for a pure, single component solid oxide, hydrous oxide, or hydroxide with a nondefective structure in an electrolyte totally devoid of specifically adsorbed polar or ionic species. An IEP(s) can be calculated from the charge and size of the cation using Equation 13 and the constants in Tables I and II. The maximum accuracy to be expected may be judged from the graphical correlation given in Figure 3. 

Calculate the isoelectric point for histidine, aspartic acid, and arginine. Calculate the fractional charge for... 

Figure 10.4 (A) The DNA interaxial distance dDNA and the interlayer distance d in the L°a phase (Figure 10.2) plotted as a function of Lipid/DNA (UD) (wt/wt) ratio at the isoelectric point of the0 complex DOTAP/DNA=2.2. dDNA is seen to expand from 24.5 A to 57.1 A. The solid line through the data is the prediction of a packing calculation where the DNA chains form a space rilling one-dimensional lattice. (B) Schematic drawing of DNA-membrane multilayers showing the increase in distance between DNA chains as the membrane charge density is decreased (i.e., as DOpc increases) at the isoelectric point (Adapted from Raedler et al., 1997 Kohover etal., 1999).

Clearly the pH gradient, the electrical field strength, and a number of other parameters can be controlled in a calculable way to achieve desired resolution levels. The excellence of resolution between components having almost identical isoelectric points was illustrated in Figure 8.8. 

Calculate the isoelectric point of aspartic acid (pKal = 2.05, pKa2 = 3.87, pKa3 = 10.00). 

The pH at which the molecule carries no net charge is called the isoelectric point. For glycine the isoelectric point is pH 6.0. Of course, in a solution of glycine at pH 6, at any instant there will be some molecules that exist as COOH—CH2— NH3, and an equal number as COO-—CH2—NH2, and even fewer of COOH—CH2—NH2. Because of the symmetry of the titration curve around the isoelectric point, it is possible to calculate the pH of the isoelectric point, given the individual pKa values. 

Calculate the isoelectric point (pH/) of aspartic acid, using the information from Prob. 3.6. SOLUTION... 

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