Protamine-Sensitive Polymer Membrane Electrode: Characterization and Bioanalytical Applications

✍ Scribed by J.H. Yun; M.E. Meyerhoff; V.C. Yang

• Publisher: Elsevier Science
• Year: 1995
• Tongue: English
• Weight: 838 KB
• Volume: 224
• Category: Article
• ISSN: 0003-2697
• DOI: 10.1006/abio.1995.1032

✦ Synopsis

A polymeric membrane electrode that exhibits significant and analytically useful potentiometric response to submicromolar levels of the heparin antagonist, protamine, is reported. The sensor is prepared by incorporating a lipophilic cation exchanger, potassium tetrakis(4-chlorophenyl)borate (KTpClPB) (at 1 wt%), within a specially formulated polymer membrane composed of (33 \mathrm{wt} % 2)-nitrophenyl octyl ether (2-NPOE), and (66 \mathrm{wt} %) poly(vinyl chloride) (PVC). When the polymer film is mounted in an appropriate electrode body, the resulting membrane electrode responds reproducibly to protamine via a nonequilibrium quasi-steadystate change in the phase boundary potential at the membrane/sample interface. Such response can be used to directly monitor, via classical potentiometric titrations, the binding between protamine and a variety of native (porcine and beef) as well as low-molecularweight heparins. Scatchard analysis of the EMF titration data provides binding constants and stoichiometries for protamine-heparin interactions. The electrode can be further used to follow the enzymatic digestion of protamine by trypsin. In the presence of a given level of protamine, initial rates of potential decrease ( (-d E / d t) ) are shown to be linearly related to trypsin activity in solution over the range of (0-130) units/ ml. The speed and simplicity of the protamine sensor make it an attractive alternative to classical methods for studying the interaction of protamine with other biologically important macromolecules as well as the proteolytic activity and reaction kinetics of trypsin. co 1995 Academic Press, Inc.