Open AccessLabel-Free Direct Visual Analysis of Hydrolytic Enzyme Activity Using Aqueous Two-Phase System Droplet Phase Transitions
Author(s) -
David Lai,
John P. Frampton,
Michael Tsuei,
Albert Kao,
Shuichi Takayama
Publication year - 2014
Publication title -
analytical chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.117
H-Index - 332
eISSN - 1520-6882
pISSN - 0003-2700
DOI - 10.1021/ac500657k
Subject(s) - dextranase , chemistry , polyethylene glycol , dextran , binodal , phase (matter) , hydrolysis , aqueous solution , aqueous two phase system , phase transition , peg ratio , chromatography , analytical chemistry (journal) , chemical engineering , phase diagram , organic chemistry , thermodynamics , physics , finance , engineering , economics
Dextran hydrolysis-mediated conversion of polyethylene glycol (PEG)-dextran (DEX) aqueous two-phase system droplets to a single phase was used to directly visualize Dextranase activity. DEX droplets were formed either by manual micropipetting or within a continuous PEG phase by computer controlled actuation of an orifice connecting rounded channels formed by backside diffused light lithography. The time required for the two-phase to one-phase transition was dependent on the Dextranase concentration, pH of the medium, and temperature. The apparent Michaelis constants for Dextranase were estimated based on previously reported catalytic constants, the binodal polymer concentration curves for PEG-DEX phase transition for each temperature, and pH condition. The combination of a microfluidic droplet system and phase transition observation provides a new method for label-free direct measurement of enzyme activity.