title: Electron-Transfer Secondary Reaction Matrices for MALDI MS Analysis of Bacteriochlorophyll a in Rhodobacter sphaeroides and Its Zinc and Copper Analogue Pigments.
abstract: Bacteriochlorophyll a (BChl a), a photosynthetic pigment performing the same functions of chlorophylls in plants, features a bacteriochlorin macrocycle ring (18 π electrons) with two reduced pyrrole rings along with a hydrophobic terpenoid side chain (i.e., the phytol residue). Chlorophylls analysis by matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) is not so straightforward since pheophytinization (i.e., release of the central metal ion) and cleavage of the phytol-ester linkage are invariably observed by employing protonating matrices such as 2,5-dihydroxybenzoic acid, sinapinic acid, and α-cyano-4-hydroxycinnamic acid. Using BChl a from Rhodobacter sphaeroides R26 strain as a model system, different electron-transfer (ET) secondary reaction matrices, leading to the formation of almost stable radical ions in both positive ([M]+•) and negative ([M]-•) ionization modes at m/z 910.55, were evaluated. Compared with ET matrices such as trans-2-[3-(4-t-butyl-phenyl)-2-methyl-2-propenylidene]malononitrile (DCTB), 2,2':5',2''-terthiophene (TER), anthracene (ANT), and 9,10-diphenylanthracene (DP-ANT), 1,5-diaminonaphthalene (DAN) was found to provide the highest ionization yield with a negligible fragmentation. DAN also displayed excellent ionization properties for two metal ion-substituted bacteriochlorophylls, (i.e., Zn- and Cu-BChl a at m/z 950.49 and 949.49), respectively. MALDI MS/MS of both radical charged molecular species provide complementary information, thus making analyte identification more straightforward. Graphical Abstract ᅟ.
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Bari Aldo Moro, Campus Universitario, Via E. Orabona, 4, 70126, Bari, Italy.|Centro di Ricerca Interdipartimentale SMART, Università degli Studi di Bari Aldo Moro, Campus Universitario, Via E. Orabona, 4, 70126, Bari, Italy.
authors.forename: Cosima Damiana
authors.initials: CD
authors.lastname: Calvano
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Bari Aldo Moro, Campus Universitario, Via E. Orabona, 4, 70126, Bari, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Ventura
authors.affiliation: Istituto Processi Chimico Fisici CNR, Università degli Studi di Bari Aldo Moro, Campus Universitario, Via E. Orabona, 4, 70126, Bari, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Trotta
authors.affiliation: Dipartimento di Scienze, Università degli Studi della Basilicata, Via dell'Ateneo Lucano, 10, 85100, Potenza, Italy.
authors.forename: Giuliana
authors.initials: G
authors.lastname: Bianco
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Bari Aldo Moro, Campus Universitario, Via E. Orabona, 4, 70126, Bari, Italy. tommaso.cataldi@uniba.it.|Centro di Ricerca Interdipartimentale SMART, Università degli Studi di Bari Aldo Moro, Campus Universitario, Via E. Orabona, 4, 70126, Bari, Italy. tommaso.cataldi@uniba.it.
authors.forename: Tommaso R I
authors.initials: TR
authors.lastname: Cataldi
authors.affiliation: Dipartimento di Chimica, Università degli Studi di Bari Aldo Moro, Campus Universitario, Via E. Orabona, 4, 70126, Bari, Italy.|Centro di Ricerca Interdipartimentale SMART, Università degli Studi di Bari Aldo Moro, Campus Universitario, Via E. Orabona, 4, 70126, Bari, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Palmisano
mesh_terms: D025541:Bacteriochlorophyll A / Q000737:chemistry*; D003300:Copper / Q000032:analysis*; D004579:Electron Transport; D004583:Electrons; D012242:Rhodobacter sphaeroides / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D015032:Zinc / Q000032:analysis*
chemical_list: D025541:Bacteriochlorophyll A; D003300:Copper; D015032:Zinc
keywords: Bacteriochlorophylls; Electron-transfer matrices; MALDI; Mass spectrometry; Tandem MS