β‐Carboline Alkaloids as Matrices for Matrix‐assisted Ultraviolet Laser Desorption Time‐of‐flight Mass Spectrometry of Proteins and Sulfated Oligosaccharides: a Comparative Study Using Phenylcarbonyl Compounds, Carbazoles and Classical Matrices

Abstract

The successful use of six β-carbolines (i.e.nor-harmane (9H-pyrido[3,4-b]indole), harmane (1-methyl-9H-pyrido[3,4-b]indole), harmine (7-methoxy-1-methyl-9H-pyrido[3,4-b]indole), harmol (1-methyl-9H-pyrido[3,4-b]indol-7-ol), harmaline (3,4-dihydro-7-methoxy-1-methyl-9H-pyrido[3,4-b]indole) and harmalol (3,4-dihydro-1-methyl-9H-pyrido[3,4-b]indol-7-ol)) is reported as matrices in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI/TOF-MS) (λexc=337 nm) for proteins (proteins checked: gramicidin S, bovine insulin, aprotinin, horse heart cytochromec, ribonuclease A, lysozyme, myoglobin, trypsin, protease and bovine serum albumin) and sulfated oligosaccharides (λ-carrageenans ofMr549, 712, 1570 and 1733), using stainless-steel probes and membranes (poly(vinylidene difluoride) (PVDF) polymers) to prepare the samples. The possible use of some phenylcarbonyl compounds (hydroxyphenyl ketones, amino- and hydroxybenzoic acids) and a few carbazole derivatives as matrices is also discussed briefly. In addition, the usefulness of the new matrices in MALDI/TOF-MS (λexc=337 nm) of proteins and sulfated oligosaccharides is compared with those of classical MALDI matrices such as α-cyano-4-hydroxycinnamic acid, gentisic acid, sinapinic acid, 6-aza-2-thiothymine and 3-indole-trans-β-acrylic acid. Laser desorption/TOF-MS (λexc=337 nm) of the new matrices is also described. © 1997 by John Wiley & Sons, Ltd.