title: Management of the diffusion of 4-methylumbelliferone across phases in microdroplet-based systems for in vitro protein evolution.
abstract: Fluorongenic reagents based on 4-methylumbelliferone (4-MU) have been widely used for the detection of phosphatase, sulfatase, esterase, lipase and glycosidase activities in conventionally formatted enzyme assay systems. However, the sensitivity of assays based on these substrates is also potentially very useful in the microdroplet formats now being developed for high throughput in vitro evolution experiments. In this article, we report the investigation of diffusion of 4-MU as a model dye from water-in-oil droplets and the internal aqueous phase of water-in-oil-in-water droplets in microfluidics. The effect of BSA in the aqueous phase on the diffusion of 4-MU is also discussed. Based on these results, we provided here proof-of-concept of the reaction of the enzyme OpdA with the substrate coumaphos in water-in-oil-in-water droplets. In this double-emulsion system, the reaction of OpdA and coumaphos was achieved by allowing coumaphos to diffuse from the continuous aqueous phase across the oil phase into the internal aqueous droplets.
authors.affiliation: CSIRO Materials Science and Engineering, Highett, VIC, Australia.
authors.forename: Nan
authors.initials: N
authors.lastname: Wu
authors.forename: Fabienne
authors.initials: F
authors.lastname: Courtois
authors.forename: Yonggang
authors.initials: Y
authors.lastname: Zhu
authors.forename: John
authors.initials: J
authors.lastname: Oakeshott
authors.forename: Chris
authors.initials: C
authors.lastname: Easton
authors.forename: Chris
authors.initials: C
authors.lastname: Abell
mesh_terms: D000818:Animals; D002417:Cattle; D003372:Coumaphos / Q000378:metabolism; D004058:Diffusion; D004655:Emulsions / Q000737:chemistry*; D057075:Enzyme Assays / Q000379:methods*; D005456:Fluorescent Dyes / Q000032:analysis / Q000737:chemistry / Q000378:metabolism; D006923:Hymecromone / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D008823:Micelles; D046210:Microfluidic Analytical Techniques / Q000379:methods*; D044345:Phosphoric Triester Hydrolases / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000737:chemistry; D014468:Umbelliferones / Q000032:analysis / Q000737:chemistry / Q000378:metabolism
chemical_list: D004655:Emulsions; D005456:Fluorescent Dyes; D008823:Micelles; D014468:Umbelliferones; D012710:Serum Albumin, Bovine; D006923:Hymecromone; D044345:Phosphoric Triester Hydrolases; C305311:chlorferron; D003372:Coumaphos