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Quartz Crystal Microbalance Measurement of Self‐Assembled Micellar Tubules of the Amphiphilic Decyl Ester of d ‐Tyrosine and Their Enzymatic Polymerization
Author(s) -
Marx Kenneth A.,
Zhou Tiean,
Sarma Rupmoni
Publication year - 1999
Publication title -
biotechnology progress
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 129
eISSN - 1520-6033
pISSN - 8756-7938
DOI - 10.1021/bp990038j
Subject(s) - quartz crystal microbalance , polymerization , chemistry , monomer , amphiphile , chemical engineering , polymer chemistry , polymer , organic chemistry , adsorption , engineering , copolymer
Amphiphilic decyl derivatives of d ‐tyrosine self‐assemble into long rodlike or tubular aggregate structures in aqueous buffered solution. In this report we demonstrate the novel use of the quartz crystal microbalance (QCM) to measure the presence in solution, and subequent enzymatic polymerization, of long rodlike monomer aggregates of the decyl ester of d ‐tyrosine (DEDT) as a function of their formation and increasing surface binding level as pH values increase from 3 to 7. From these data, using the Sauerbray equation to calculate the effective elastic mass surface binding of deprotonated DEDT aggregates, a p K app of 8.3 is obtained for the DEDT α‐NH 2 group protonation−deprotonation and subsequent aggregation equilibrium. Furthermore, once aggregates are bound to the QCM surface, we initiate and subsequently monitor enzymatic polymerization of the DEDT monomers by horseradish peroxidase through the measurement of significant changes in the quartz crystal frequency and motional resistance. Following the onset of polymerization, the viscoelastic properties of the bound monomer aggregates change. A final polymerized state is achieved in which the altered physical properties of the polymerized rodlike aggregates make the solution immediately above the QCM surface−solution interface behave as a Newtonian fluid, producing a nearly pure viscosity−density energy dissipative effect on the measured crystal frequency and motional resistance values.