MATERIALS SCIENCE & ENGINEERIMG ELSEVIER Materials Science and EngineeringC 4 (1996) 189-192 Enzymatic polymerization of amphiphilic alkyl tyrosine derivatives from emulsions Rupmoni Sarma a, K. Shridhara Alva b, Kenneth A. Marx a,*, Sukant K. Tripathy a, Joseph A. Akkara °, David L. Kaplan ° a Department of Chemistry, Centers for Advanced Materials and Intelligent Biomaterials, University of Massachusetts, Lowell, MA 01854, USA b Department of Physics, Centers for Advanced Materials and Intelligent Biomaterials, University of Massachusetts, Lowell, MA 01854, USA Biotechnology Division, US Arm), Natick Research, Development and Engineering Center, Natick, MA O1760, USA Abstract Horseradish peroxidase catalyzed polymerizations of amphiphilic derivatives of d- and/-isomers of tyrosine have been carried out in micetlar solutions. The rate of polymerization has been found to be maximum at a pH of 6.1-6.2 and showed a second-order dependence on the monomer concentration. This enzyme shows stereospecificity towards the d-isomer compared to the/-isomer, which is consistent with the aqueous reaction with underivatized isomers of tyrosine. The resulting polymers, having a molecular weight of 2700, have been characterized by UV-Vis spectroscopy and ~H NMR. The polymer shows surface activity at the air-water interface unlike the corresponding monomer, which aggregates under identical conditions. Keywords: Micelles;Polyphenol;Horseradishperoxidase; Enzymaticpolymerization 1. Introduction Phenolic based polymers have been the focus of interest for industrial applications. Horseradish peroxidase (HRP) catalyzed polymerization of phenols has been studied in mon- ophasic aqueous or organic solvents as well as in reverse micelles [ 1-5]. These methods result in an insoluble cross- linked polymer. Cross-linked polymers, due to their insoluble nature, are difficult to process for industrial applications. Pol- ymers of alkyl derivatives of phenols are easily processable, but they pose problems of common solvent for the enzyme catalyzed reactions. Though the reverse miceltar technique is useful in the polymerization of alkyl derivatives of the mon- omers, in the case of long alkyt chain derivatives, the mon- omer becomes soluble in the bulk organic solvent instead of staying at the oil-water interface. Polymerization of these long alkyl chain derivatives could be accomplished by form- ing micelles in aqueous medium. In micelles, the polar phe- nolic moieties are exposed towards the bulk aqueous phase, in which the enzyme is dissolved, while the hydrophobic chain forms the micellar core. Amphiphilic molecules, bearing distinct hydrophobic and hydrophilic segments aggregate in aqueous media, forming * Correspondingauthor. 0928-4931/96/$15.00 © 1996 ElsevierScienceS.A. AIt rights reserved PIIS0928-4931 (96)00152-X various molecular organizations such as micelles, vesicles and membranes. Amphiphiles having one long aliphatic chain form micelles when their concentration exceeds a critical value known as the critical micellar concentration [6]. Micetles are in a state of dynamic equilibrium with non- aggregated amphiphiles in solution [ 6-8]. Therefore, one of the incentives to study polymerization of monomers in micelles was to chemically fix these loose monomeric micel- lar structures. This paper presents a novel method for the polymerization of long chain derivatives of phenols. Compounds studied here are the decyl ester d-(DEDT) and /-(DELT) isomers of tyrosine whose structures are shown in Fig. 1. The HRP cat- alyzed polymerization of l- and d-isomers of tyrosine is known to exhibit limited stereospecificity, with the reaction of the d-isomer about twice as fast as the/-isomer [9]. Here, we also report on the stereospecificity of the enzyme cata- lyzed polymerization reaction towards the isomers of the long chain derivatives of tyrosine. 2. Experimental procedures Horseradish peroxidase, (EC 1.11.1.7) was purchased from the Sigma Chemical Company, St Louis, MO. 30%