title: Tip-enhanced laser ablation sample transfer for biomolecule mass spectrometry.
abstract: Atomic force microscope (AFM) tip-enhanced laser ablation was used to transfer molecules from thin films to a suspended silver wire for off-line mass spectrometry using laser desorption ionization (LDI) and matrix-assisted laser desorption ionization (MALDI). An AFM with a 30 nm radius gold-coated silicon tip was used to image the sample and to hold the tip 15 nm from the surface for material removal using a 355 nm Nd:YAG laser. The ablated material was captured on a silver wire that was held 300 μm vertically and 100 μm horizontally from the tip. For the small molecules anthracene and rhodamine 6G, the wire was cut and affixed to a metal target using double-sided conductive tape and analyzed by LDI using a commercial laser desorption time-of-flight mass spectrometer. Approximately 100 fg of material was ablated from each of the 1 μm ablation spots and transferred with approximately 3% efficiency. For larger polypeptide molecules angiotensin II and bovine insulin, the captured material was dissolved in saturated matrix solution and deposited on a target for MALDI analysis.
authors.affiliation: Department of Chemistry, Louisiana State University, Baton Rouge, LA, 70803, USA.
authors.forename: Suman
authors.initials: S
authors.lastname: Ghorai
authors.forename: Chinthaka A
authors.initials: CA
authors.lastname: Seneviratne
authors.forename: Kermit K
authors.initials: KK
authors.lastname: Murray
mesh_terms: D000804:Angiotensin II / Q000737:chemistry; D000818:Animals; D002417:Cattle; D007328:Insulin / Q000737:chemistry; D007834:Lasers; D018625:Microscopy, Atomic Force; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D007328:Insulin; D000804:Angiotensin II