title: "Green" synthesis of unnatural poly(Amino Acid)s with Zwitterionic character and pH-responsive solution behavior, mediated by linear-dendritic laccase complexes.
abstract: This article describes the enzyme-catalyzed "green" synthesis of an unnatural poly(amino acid). dl-Tyrosine was polymerized under environmentally friendly conditions using linear-dendritic laccase complexes as initiators and water as solvent. The influence of the dendron generation in the linear-dendritic copolymers, the monomer concentration, and time and temperature on the polymer yields and molecular masses was investigated. Depending on the reaction conditions poly(tyrosine) with molecular mass (Mw) up to 82 kDa could be obtained in yields ranging between 45 and 69%. It was found that the linear-dendritic laccase complexes can induce further chain growth upon addition of fresh monomer to the preformed poly(tyrosine) in a fashion resembling the classic "living" polymerization. The structure of the poly(tyrosine) was investigated by NMR, FT-IR, and MALDI-TOF and it was discovered that the polymer chains consist of phenol repeating units linked together by C-C and C-O bonds randomly distributed along the backbone of the polymers. The materials formed are completely water-soluble and behave as typical poly(zwitterions) changing charge and size with the medium pH. DLS measurements reveal that the zeta potential of the polymers can vary between +15 mV at pH 1.2 with hydrodynamic diameter (Dh) = 6.7 nm to -35 mV at pH 11.8 and Dh = 10 nm. The isoelectric point was found at pH = 2.3-2.6, where Dh of the polymer is at the minimum (2.4 nm).
authors.affiliation: The Michael M. Szwarc Polymer Research Institute and ‡Department of Chemistry, State University of New York - College of Environmental Science and Forestry , Syracuse, New York 13210, United States.
authors.forename: Ivan
authors.initials: I
authors.lastname: Gitsov
authors.forename: Lili
authors.initials: L
authors.lastname: Wang
authors.forename: Nikolay
authors.initials: N
authors.lastname: Vladimirov
authors.forename: Arsen
authors.initials: A
authors.lastname: Simonyan
authors.forename: David J
authors.initials: DJ
authors.lastname: Kiemle
authors.forename: Andri
authors.initials: A
authors.lastname: Schutz
mesh_terms: D000818:Animals; D016466:CHO Cells; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D006224:Cricetinae; D003412:Cricetulus; D055772:Green Chemistry Technology / Q000379:methods*; D006863:Hydrogen-Ion Concentration; D042845:Laccase / Q000737:chemistry / Q000494:pharmacology*; D010455:Peptides / Q000138:chemical synthesis*; D019999:Pharmaceutical Solutions / Q000737:chemistry*; D017433:Protein Structure, Secondary; D055454:Trametes
chemical_list: D010455:Peptides; D019999:Pharmaceutical Solutions; C017663:polytyrosine; D042845:Laccase