title: A thiophene-containing compound as a matrix for matrix-assisted laser desorption/ ionization mass spectrometry and the electrical conductivity of matrix crystals.
abstract: The electrical conductivity of the matrix crystal might be a new factor to enhance matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) sensitivity. In MALDI-MS, several compounds are used as a standard matrix. Utilization of such compounds is based on an a posteriori approach, but there is no theoretical guidance for selecting a matrix. In an attempt to further understand performance in MALDI-MS, we utilized peptide detection for random screening of a chemical library (12,383 compounds) for compounds with matrix functions in MALDI-MS. A lot of thiophene compounds were found to be a matrix, in which 2-[5-(2,4-dichlorobenzoyl)-2-thienyl] acetic acid (DCBTA) provided an important clue to measure the electrical conductivity of the matrix crystal, because the structure of DCBTA is analogous to conductive polymers and organic solar cells. Most of the crystals of standard matrices, such as alpha-cyano-4-hydroxycinnamic acid (CHCA), 3,5-dimethoxy-4-hydroxycinnamic acid [sinapinic acid, (SA)], and DCBTA showed electrical conductivity, whereas the conductivity of crystal was not observed in 2,5-dihydroxybenzoic acid (2,5-DHB). On the other hand, super-DHB using 2-hydroxy-5-methoxybenzoic acid [5-methoxysalicylic acid, (MSA)] as an additive to 2,5-DHB, improved the electrical conductivity of the crystal, that followed the enhancement of peak intensity in MS spectrum. These observations might indicate that the electrical conductivity of matrix crystals is a key consideration in obtaining efficient MALDI performance.
authors.affiliation: Health Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Midorigaoka, Ikeda, Osaka 563-8577, Japan.
authors.forename: Akikazu
authors.initials: A
authors.lastname: Yasuda
authors.forename: Takayuki
authors.initials: T
authors.lastname: Ishimaru
authors.forename: Shogo
authors.initials: S
authors.lastname: Nishihara
authors.forename: Masamichi
authors.initials: M
authors.lastname: Sakai
authors.forename: Hideya
authors.initials: H
authors.lastname: Kawasaki
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Arakawa
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Shigeri
mesh_terms: D003373:Coumaric Acids / Q000737:chemistry; D003460:Crystallization; D004553:Electric Conductivity; D004586:Electrophoresis; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000295:instrumentation / Q000379:methods*; D013876:Thiophenes / Q000737:chemistry*
chemical_list: D003373:Coumaric Acids; D013876:Thiophenes; C007175:alpha-cyano-4-hydroxycinnamate; C073734:sinapinic acid