title: Quasi-dynamic mode of nanomembranes for time-of-flight mass spectrometry of proteins.
abstract: Mechanical resonators realized on the nano-scale by now offer applications in mass-sensing of biomolecules with extraordinary sensitivity. The general idea is that perfect mechanical biosensors should be of extremely small size to achieve zeptogram sensitivity in weighing single molecules similar to a balance. However, the small scale and long response time of weighing biomolecules with a cantilever restrict their usefulness as a high-throughput method. Commercial mass spectrometry (MS) such as electro-spray ionization (ESI)-MS and matrix-assisted laser desorption/ionization (MALDI)-time of flight (TOF)-MS are the gold standards to which nanomechanical resonators have to live up to. These two methods rely on the ionization and acceleration of biomolecules and the following ion detection after a mass selection step, such as time-of-flight (TOF). Hence, the spectrum is typically represented in m/z, i.e. the mass to ionization charge ratio. Here, we describe the feasibility and mass range of detection of a new mechanical approach for ion detection in time-of-flight mass spectrometry, the principle of which is that the impinging ion packets excite mechanical oscillations in a silicon nitride nanomembrane. These mechanical oscillations are henceforth detected via field emission of electrons from the nanomembrane. Ion detection is demonstrated in MALDI-TOF analysis over a broad range with angiotensin, bovine serum albumin (BSA), and an equimolar protein mixture of insulin, BSA, and immunoglobulin G (IgG). We find an unprecedented mass range of operation of the nanomembrane detector.
authors.affiliation: Electrical and Computer Engineering, University of Wisconsin, Madison, WI 53706, USA.
authors.forename: Jonghoo
authors.initials: J
authors.lastname: Park
authors.forename: Hyunseok
authors.initials: H
authors.lastname: Kim
authors.forename: Robert H
authors.initials: RH
authors.lastname: Blick
mesh_terms: D000818:Animals; D002417:Cattle; D007074:Immunoglobulin G / Q000737:chemistry; D007328:Insulin / Q000737:chemistry; D008567:Membranes, Artificial; D036103:Nanotechnology; D011506:Proteins / Q000737:chemistry*; D012710:Serum Albumin, Bovine / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D007074:Immunoglobulin G; D007328:Insulin; D008567:Membranes, Artificial; D011506:Proteins; D012710:Serum Albumin, Bovine