| Home  | About ScienceAsia  | Publication charge  | Advertise with us  | Subscription for printed version  | Contact us  
Editorial Board
Journal Policy
Instructions for Authors
Online submission
Author Login
Reviewer Login
Volume 50 Number 1
Volume 49 Number 6
Volume 49 Number 5
Volume 49S Number 1
Volume 49 Number 4
Volume 49 Number 3
Earlier issues
Back

Research Article

ScienceAsia 29 (2003): 045-049 |doi: 10.2306/scienceasia1513-1874.2003.29.045

Determination of Acidity and Basicity Constants of Polyaspartic Acids by Potentiometric Titrations

Vithaya Ruangpornvisuti* and Boosayarat Tomapatanaget


ABSTRACT: The acidity and basicity constants of asp-asp-asp, asp-asp-asp-asp, asp-asp-asp-asp-asp and asp-asp-asp-asp-asp-asp polypeptides were determined in 0.1 M potassium nitrate at 25 oC by potentiometric titrations. Logarithm of the basicity constants of the asp-asp-asp, asp-asp-asp-asp, asp-asp-asp-asp-asp and asp-asp-asp-asp-asp-asp are 8.34, 8.50, 8.56 and 8.99 respectively. The number of the acidity constants of the polyaspartic acids is equivalent to the number of carboxylic acids in their molecules. The pH at the isoelectric points of the asp-asp-asp, asp-asp-asp-asp, asp-asp-asp-asp-asp and asp-asp-asp-asp-asp-asp in aqueous solution, evaluated from their corresponding acidity constants and the titration data are 3.1, 2.8, 2.7 and 2.4, respectively.

Download PDF


Department of Chemistry, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand.

* Corresponding author, Email: vithaya.r@chula.ac.th

Received 6 Dec 2001, Accepted 1 Jut 2002