Ion Exchange Technology II Applications
Ion-exchange Technology II: Applications presents an overview of the numerous industrial applications of ion-exchange materials.In particular, this volume focuses on the use of ion-exchange materials in various fields including chemical and biochemi
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Separation of Amino Acids, Peptides, and Proteins by Ion Exchange Chromatography Tanja Cirkovic Velickovic, Jana Ognjenovic, and Luka Mihajlovic
Abstract Separation of amino acids, peptides, and proteins (bioanalytes) via ion exchange (IE) has widespread usage because it is usually very simple to design and it has high capacity and easily achievable control of the separation process. Amino acids, as principal constituents of proteins and having a plethora of biological functions of their own, are always in focus when developing novel methods. Separation and quantification of amino acids is essential in food science, medicine, agricultural science, etc. Peptides exist in nature and have diverse functions. Digestion of proteins by enzymes also gives complex mixtures of peptides and IE finds its application in peptide separation. There are lots of reasons for the popularity of IE in protein isolation and purification. It is used in research, analysis, and large-scale purification of proteins. Ion exchange is ideal for the initial capture of proteins because of its high capacity, relatively low cost, and its ability to survive rigorous cleaning regimes. This chapter covers basic principles and modern applications of IE in separation of amino acids, peptides, and proteins.
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Introduction
The technique of ion exchange (IE) is based on interactions between charged moieties. Amino acids, peptides, and proteins (bioanalytes) are water-soluble, charged amphoteric molecules and as such, able to bind via Coulomb’s interactions to oppositely charged moieties covalently linked to an insoluble carrier (matrix, or a stationary phase). Stationary phases for ion exchange separations are characterized by the nature and strength of the acidic or basic functions on their surfaces and the
T. Cirkovic Velickovic (*) • J. Ognjenovic • L. Mihajlovic University of Belgrade, Studentski Trg 12-16, 11000 Belgrade, Serbia e-mail: [email protected]
Inamuddin and M. Luqman (eds.), Ion Exchange Technology II: Applications, DOI 10.1007/978-94-007-4026-6_1, © Springer Science+Business Media B.V. 2012
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types of ions that they attract. Cation exchangers retain and separate positively charged ions (analytes) on a negative surface, while anion exchangers retain and separate negatively charged ions on a positive surface. There are at least two general approaches for separation and elution with each type of ion exchanger [1]. Strength of the interaction between stationary phase and the analyte can be controlled by changing the ionic strength of the solution. Also, ionic properties of ionizable functional groups by pH titration of the stationary phase or the analyte can be controlled, allowing great variability in the design of IE experiments. Strong ion exchangers bear functional groups that are always ionized, over a wide range of pH values. They are typically used to retain and separate weak acids or bases. These weak ions may be eluted by displacement with ions that are more strongly attracted to the st
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