The nuclear magnetic resonance titration curves of chemical shift versus pH of two of the histidine ring C(2) protons of ribonuclease show deviations from the curve expected for a simple proton association equilibrium. We have previously shown (Sachs, Schechter & Cohen, 1971), using model systems...
a. 0b. −2c. +2d. −1ANS: B DIF: Difficult REF: 4.1OBJ: 4.1.b. Define the isoelectric point (pI).8. A polypeptide has a high pI value. Which amino acids mia. arginine What amino acid is depicted by the titration cu...
A method for determination of thermodynamic acidity constants is described. The potentiometric titration curve will be linearised with an iterative procedure for activity coefficients and an assumption for acidity constant calculated without activity coefficients. From the straight line given by least square...
The pK of these histidines, as estimated from the difference titration curve, is about 7.8, both in oxy- and deoxyhemoglobin. This high pK is probably caused by the formation of a saltbridge with the carboxyl group of aspartic acid B3(20)尾 in the same chain. Both hemoglobins contain 72...
Cadmium binding to a histidine- rich glycoprotein from marine mussel blood plasma: Po- tentiometric titration and equilibrium speciation modeling. Environ. Toxicol. Chem. (In preparation).Satish N, Robinson W. Cadmium binding to a Histidine-Rich Glycoprotein from marine mussel blood plasma: ...
The histidine titration curve obtained by NMR is an exact representation of the average protonation state of the imidazole ring. Therefore, it gives an actual microscopic hydrogen-ion dissociation constant for the imidazole group. Each histidine residue in a protein can be observed separately, and ...
Even in apohaemocyanin about 6 × 10−5 histidine residues per g protein are not titrated in their normal pH region. In the presence of sufficient calcium to displace the dissociation completely out of the titration region the titration curve of apohaemocyanin could he linarized according to...
Intrinsic dissociation constants for the carboxyl groups of acidic residues and also for the imidazole side chains of histidine residues in HRP are estimated using the Tanford expression. From the obtained titration curve the intrinsic pKa (pKa,int) of titratable groups, the electrostatic free energy...
The titration curve between pH 2.5 and 7.5 was compatible with that of an equivalent electrostatic sphere possessing 104 titratable carboxyl groups with an intrinsic p K of 4.28 and 17 histidine groups with an intrinsic p K of 6.20. The observed value for the electrostatic interaction factor, w...
Whereas the three other histidine C (2)-peaks exhibited normal titration curves with single p K′ values of 7.20, 6.71 and 6.67, the peak assigned to His(57) had an abnormal titration curve showing two protonation steps in the pH range from 1 to 9. The first protonation with a pH′ ...