Matrix‐assisted laser desorption/ionization mass spectrometry of noncovalent protein–transition metal ion complexes

Salih, Bekir; Masselon, Christophe; Zenobi, Renato

doi:10.1002/(sici)1096-9888(1998100)33:10<994::aid-jms714>3.0.co;2-#

Cited by 37 publications

(26 citation statements)

References 6 publications

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“…Equilibrium dialysis using glycine chelated copper (15,24,52) questions arise as to the attributes and/or advantages of the DEPC "footprinting" methodology. For conventional MALDI-MS (53), direct analysis of native metal-peptide complexes is complicated by the required excess of a matrix that is typically strongly acidic and thus favors histidine protonation and protein denaturation.…”

Section: Metal-protein Binding and Neurodegenerative Disease-mentioning

confidence: 99%

“…For conventional MALDI-MS (53), direct analysis of native metal-peptide complexes is complicated by the required excess of a matrix that is typically strongly acidic and thus favors histidine protonation and protein denaturation. Consequently, MALDI can have a reduced ability to detect low affinity sites when compared with other techniques, although novel sample preparation matrices have now been developed to offset the effect (52). Another approach is to use large excesses of metal ions, although this has a potential to reveal low affinity sites, leading to the problem of discerning of nonspecific interaction metal/peptide interactions.…”

Section: Metal-protein Binding and Neurodegenerative Disease-mentioning

confidence: 99%

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Mapping Cu(II) Binding Sites in Prion Proteins by Diethyl Pyrocarbonate Modification and Matrix-assisted Laser Desorption Ionization-Time of Flight (MALDI-TOF) Mass Spectrometric Footprinting

Qin¹,

Yang²,

Mastrangelo³

et al. 2002

Journal of Biological Chemistry

150

133

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Section: Metal-protein Binding and Neurodegenerative Disease-mentioning

confidence: 99%

Section: Metal-protein Binding and Neurodegenerative Disease-mentioning

confidence: 99%

Mapping Cu(II) Binding Sites in Prion Proteins by Diethyl Pyrocarbonate Modification and Matrix-assisted Laser Desorption Ionization-Time of Flight (MALDI-TOF) Mass Spectrometric Footprinting

Qin¹,

Yang²,

Mastrangelo³

et al. 2002

Journal of Biological Chemistry

150

133

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“…The matrices studied in this work are nicotinic acid, dithranol, and 2,5-dihydroxybenzoic acid. ϩ ) were observed in the analysis of proteins [11,17,19,20] and polar synthetic polymers, e.g., polyethylene glycols (PEG) [12], whereas in the analysis of apolar synthetic polymers, e.g., polystyrene (PS), the reduction of divalent metal ions was dominant [13][14][15][16]18].…”

mentioning

confidence: 99%

“…One of the noticeable MALDI phenomena is the dominance of singly charged ions. For instance, the adducts of multivalent metal ions are detected as singly charged quasimolecular ions formed either by deprotonation ([M ϩ Me(II) Ϫ H] ϩ ) or by reduction of metal ions ([M ϩ Me(I)] ϩ ), e.g., Cu(II) to Cu(I) [11][12][13][14][15][16][17][18][19]. Signals of both types of metal ion adducts ([M ϩ Me(II) Ϫ H] ϩ and [M ϩ Me(I)] ϩ ) were observed in the analysis of proteins [11,17,19,20] and polar synthetic polymers, e.g., polyethylene glycols (PEG) [12], whereas in the analysis of apolar synthetic polymers, e.g., polystyrene (PS), the reduction of divalent metal ions was dominant [13][14][15][16]18].…”

mentioning

confidence: 99%

Reduction of Cu(II) in matrix-assisted laser desorption/ionization mass spectrometry

Zhang¹,

Frankevich²,

Knochenmuss³

et al. 2003

J. Am. Soc. Mass Spectrom.

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The mechanisms of the reduction of Cu(II) in matrix-assisted laser desorption/ionization mass spectrometry (MALDI) are studied. In MALDI mass spectra, ions cationized by copper mostly contain Cu(I) even if Cu(II) salts are added to the sample. It was found that Cu(II) was reduced to Cu(I) by gas-phase charge exchange with matrix molecules, which is a thermodynamically favorable process. Under some conditions, large amounts of free electrons are present in the plume. Cu(II) can be even more efficiently reduced to Cu(I) by free electron capture in the gas phase. The matrices studied in this work are nicotinic acid, dithranol, and 2,5-dihydroxybenzoic acid. ϩ ) were observed in the analysis of proteins [11,17,19,20] and polar synthetic polymers, e.g., polyethylene glycols (PEG) [12], whereas in the analysis of apolar synthetic polymers, e.g., polystyrene (PS), the reduction of divalent metal ions was dominant [13][14][15][16]18].In this work, we present a detailed study of the reduction of divalent copper used as a cationization agent in MALDI. Different explanations of this reduction in the gas phase have been given, namely electron capture [21] and charge exchange with matrix [22]. The origin and the amount of free electrons in MALDI has not been comprehensively investigated before and many questions were still open [22]. Recently, studies of the origin of the free electrons in MALDI from our laboratory [23,24] have shown that free electrons are largely formed by photoelectric emission from a metal/ dielectric-substance interface, not by photoionization of matrix [21]. Our studies also showed that the yield of electrons strongly depends on the thickness of the matrix layer. In the case of nonmetallic surfaces, few electrons are produced.According to these results, we are able to investigate the roles of free electrons and matrices as possible reducing agents in MALDI separately. Blocking the electron source by using a nonmetallic sample carrier or a metallic target covered with an insulating layer provides the possibility to examine the effect of the gasphase charge transfer between divalent metal ions and the matrices. For investigation of the effect of the free electron capture, experiments have to be done in the absence of matrix by using direct laser desorption/ ionization (LDI) of the sample.Under continuous extraction conditions, for example on a time-of-flight (TOF) mass spectrometer, free electrons as the most mobile species can either be extracted very quickly (in the negative ion mode) or pushed back towards the target (in the positive ion mode) and thus have less overlap with the plume, i.e., electrons will be less available for capture by positively charged species. On the other hand, delayed extraction allows time for secondary ion-molecule reactions to occur, e.g., the charge transfer reaction between neutral matrix molecules and copper ions. In order to investigate the influence of the high extraction field on the free electron capture and the charge exchange reaction, we have compared the results ...

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“…Specific and nonspecific interactions between a peptide and a Cu ion were observed in similar complexes. 34 A nonspecific interaction is likely formed in the gas phase. 35 The penta-phosphorylated peptide a S1 (74-94) at m/e 907.63 and tetra- For all but one of the CPPs, the intensity of the Zn-bound peptide is significantly less than that of the free peptide.…”

Section: Effect Of Casein Dephosphorylation On Zn Binding To Cppsmentioning

confidence: 99%

Analysis of effect of casein phosphopeptides on zinc binding using mass spectrometry

Green

McGibbon

McCarry

2007

Rapid Comm Mass Spectrometry

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Phosphorylation is one of the key events in signal transduction and zinc plays an important catalytic and/or structural role in many biological systems. The binding of Zn to a phosphopeptide will alter the physiological functions of a peptide. The binding of casein phosphopeptides (CPPs) to Zn has been analyzed using nanospray mass spectrometry. Electrospray ionization (ESI) spectra of peptides produced by tryptic digestion of alpha-casein incubated with Zn show both free and Zn-bound phosphopeptides. The interaction of CPPs and the corresponding dephosphorylated peptides with zinc is compared. This study demonstrates that the phosphorylation state of a peptide dramatically affects Zn binding, with the decrease in Zn-bound forms of peptide paralleling the decrease in phosphorylation as casein is chemically dephosphorylated, although, in some cases, a small amount of residual Zn-binding capacity remains in the completely dephosphorylated peptide. The observed fragmentation patterns of the Zn-bound CPPs support the thesis that nonphosphorylated residues are involved in the metal binding.

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Matrix‐assisted laser desorption/ionization mass spectrometry of noncovalent protein–transition metal ion complexes

Cited by 37 publications

References 6 publications

Mapping Cu(II) Binding Sites in Prion Proteins by Diethyl Pyrocarbonate Modification and Matrix-assisted Laser Desorption Ionization-Time of Flight (MALDI-TOF) Mass Spectrometric Footprinting

Mapping Cu(II) Binding Sites in Prion Proteins by Diethyl Pyrocarbonate Modification and Matrix-assisted Laser Desorption Ionization-Time of Flight (MALDI-TOF) Mass Spectrometric Footprinting

Reduction of Cu(II) in matrix-assisted laser desorption/ionization mass spectrometry

Analysis of effect of casein phosphopeptides on zinc binding using mass spectrometry

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