IMPORTANCE OF MATRIX ANALYTE RATIO FOR BUFFER TOLERANCE USING 2,5-DIHYDROXYBENZOIC ACID AS A MATRIX IN MATRIX-ASSISTED-LASER-DESORPTION/IONIZATION FOURIER-TRANSFORM MASS-SPECTROMETRY AND MATRIX-ASSISTED-LASER-DESORPTION/IONIZATION TIME-OF-FLIGHT/

Many biological samples destined for matrix-assisted laser desorption/ ionization mass spectrometry (MALDI-MS) contain buffers. The presence of these buffers often inhibits the ability to obtain spectra. Here, t he results of a study of the effects of six different buffers on spect ra of three representative small proteins are reported utilizing 2,5-d ihydroxybenzoic acid as matrix. These proteins, bovine insulin, cytoch rome c, and bovine albumin have masses from similar to 5000 to 66,000 Da. Three different sample preparation techniques were investigated: a erospray, dried-drop, and acetone redeposition. Both MALDI Fourier tra nsform and time-of-flight mass spectrometry results show that buffer t olerance of MALDI MS samples depends upon several factors, including t he relative amount of the buffer in the MALDI matrix, as well as the i dentity of the specific buffer. Furthermore, the rate at which buffer tolerance decreases as buffer concentration is increased varies from b uffer to buffer. The current results reveal that, at very high matrix: analyte ratios, buffer tolerance of MALDI is dramatically greater than concluded in previous literature reports. (C) 1998 American Society f or Mass Spectrometry.