title: Monitoring Enzymatic Reactions in Real Time Using Venturi Easy Ambient Sonic-Spray Ionization Mass Spectrometry.
abstract: We developed a technique to monitor spatially confined surface reactions with mass spectrometry under ambient conditions, without the need for voltage or organic solvents. Fused-silica capillaries immersed in an aqueous solution, positioned in close proximity to each other and the functionalized surface, created a laminar flow junction with a resulting reaction volume of ∼5 pL. The setup was operated with a syringe pump, delivering reagents to the surface through a fused-silica capillary. The other fused-silica capillary was connected to a Venturi easy ambient sonic-spray ionization source, sampling the resulting analytes at a slightly higher flow rate compared to the feeding capillary. The combined effects of the inflow and outflow maintains a chemical microenvironment, where the rate of advective transport overcomes diffusion. We show proof-of-concept where acetylcholinesterase was immobilized on an organosiloxane polymer through electrostatic interactions. The hydrolysis of acetylcholine by acetylcholinesterase into choline was monitored in real-time for a range of acetylcholine concentrations, fused-silica capillary geometries, and operating flow rates. Higher reaction rates and conversion yields were observed with increasing acetylcholine concentrations, as would be expected.
authors.affiliation: Department of Chemistry, Stanford University , Stanford, California 94305, United States.|Department of Chemistry-BMC, Uppsala University , SE-75124 Uppsala, Sweden.
authors.forename: Erik T
authors.initials: ET
authors.lastname: Jansson
authors.affiliation: Department of Chemistry, Stanford University , Stanford, California 94305, United States.
authors.forename: Maria T
authors.initials: MT
authors.lastname: Dulay
authors.affiliation: Department of Chemistry, Stanford University , Stanford, California 94305, United States.
authors.forename: Richard N
authors.initials: RN
authors.lastname: Zare
mesh_terms: D000109:Acetylcholine / Q000378:metabolism; D000110:Acetylcholinesterase / Q000737:chemistry / Q000378:metabolism*; D002794:Choline / Q000032:analysis*; D004800:Enzymes, Immobilized / Q000737:chemistry / Q000378:metabolism; D011108:Polymers / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D004800:Enzymes, Immobilized; D011108:Polymers; D012822:Silicon Dioxide; D000110:Acetylcholinesterase; D002794:Choline; D000109:Acetylcholine