Laser desorption/ionization time-of-flight mass spectrometry of biomolecules

Lasers have been used to generate ions for mass spectrometer detection. Laser energy can be efficiently and controllably transferred to the sample, because laser provides high energy with a short pulse (1 to 100 ns). Samples are vaporized and ionized before their decomposition. This technique is suitable for the analysis of polar, nonvolatile, and thermally-labile compounds, especially biomolecules. The goal of this research has been to show the utility of laser desorption/ionization time-of-flight mass spectrometry. Our approaches involve: (1) matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and its application to the detection of peptides and proteins, (2) on-line coupling of capillary electrophoresis and mass spectrometer by a new laser desorption/ionization interface;First, we investigate the properties of neutral red as a visible-wavelength matrix for matrix-assisted laser desorption ionization. Since the general transparency in the visible region of proteins, peptides can provide definite advantages over UV desorption. Neutral red is stable over a ten-fold range in laser fluence. The superior ability of neutral red to efficiently ionize molecules is demonstrated with several peptides. In order to monitor the desorption process, the ablated material is collected and then analyzed by capillary electrophoresis. The effects of varying the neutral red to insulin ratio for a constant amount of insulin are examined for the contents of the ablated material. NR is an efficient matrix which can successfully desorb peptides and proteins with fragmentation even at high laser power density;Secondly, a laser vaporization/ionization time-of-flight mass spectrometer for capillary electrophoresis is developed. Mass spectrometry (MS) is usually coupled on-line with capillary electrophoresis to analyze biomolecules by using electrospray (ESI) or continuous-flow fast atom bombardment (FAB). We present a new design for CE-MS. CE, with its low flow rate (\u3c1 [mu]l/min.) is highly compatible with MS even if the total column effluent is introduced directly. A UV laser is used to vaporize and ionize the solution eluting from the column. Using this system, we have analyzed a group of amines and peptides. The concentration detection limit of serotonin is in the 10-7 M range. The separation and identification of amine mixtures by CE will be shown