Characterization and determination of titratable groups of proteins by linearization of titration curves. II. Application to lysozyme

✍ Scribed by O.E.S. Godinho; L.M. Aleixo; J.P. Hora Alves

• Publisher: Elsevier Science
• Year: 1982
• Tongue: English
• Weight: 425 KB
• Volume: 123
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1016/0003-2697(82)90441-9

✦ Synopsis

The potentiometric acid-base titration curve of fully protonated lysozyme at ionic strengths of 0. IO and f .O M has been performed. The stoichiometry and the pK* values of each titratable group have been determined through the linearization of titration curves. Two types of carboxylic groups with pxI, values of 3.76 and 5.02, the imidazole group with pK* 7.37 and the amino group with pK, 9.63, have been identified at an ionic strength of 0.10 M at 250°C. The number of titratable groups found per mole of protein has been 5.12 and 5.60 for the two types of carboxylic groups, 1.13 for the imidazole group, and 3.19 for the amino groups. The endpoint of the titration of the protein obtained by this method accords quite well with the endpoint obtained by the use of Gran function applied to the excess of strong base.