Catalytic Gas Phase Oxidation of Methanol to Formaldehyde

Waters, T. N.; O’Hair, Richard A. J.; Wedd, Anthony G.

doi:10.1021/ja028839x

Cited by 246 publications

(284 citation statements)

References 53 publications

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“…Instrument modifications have been described previously [35,36]. The ion of interest was mass selected and liquid tbutylnitrite was infused into the He line at a rate of 10 L/min, corresponding to a pressure of ϳ1 ϫ 10 Ϫ7 Torr in the ion trap region.…”

Section: Mass Spectrometry Experimentsmentioning

confidence: 99%

Gas-phase fragmentation of long-lived cysteine radical cations formed via no loss from protonated S-nitrosocysteine

Ryzhov

Lam

O’Hair

2009

J. Am. Soc. Mass Spectrom.

101

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In this work, we describe two different methods for generating protonated S-nitrosocysteine in the gas phase. The first method involves a gas-phase reaction of protonated cysteine with t-butylnitrite, while the second method uses a solution-based transnitrosylation reaction of cysteine with S-nitrosoglutathione followed by transfer of the resulting S-nitrosocysteine into the gas phase by electrospray ionization mass spectrometry (ESI-MS). Independent of the way it was formed, protonated S-nitrosocysteine readily fragments via bond homolysis to form a long-lived radical cation of cysteine (Cys •ϩ ), which fragments under collision-induced dissociation (CID) conditions via losses in the following relative abundance order: •COOH ӷ CH 2 S Ͼ •CH 2 SH Ϸ H 2 S. Deuterium labeling experiments were performed to study the mechanisms leading to these pathways. DFT calculations were also used to probe aspects of the fragmentation of protonated S-nitrosocysteine and the radical cation of cysteine. NO loss is found to be the lowest energy channel for the former ion, while the initially formed distonic Cys•ϩ with a sulfur radical site undergoes proton and/or H atom transfer reactions that precede the losses of T here has been renewed interest in the gas-phase formation and reactions of radical ions of biomolecules. The motivation for these studies range from fundamental interest in species related to biological processes such as enzyme catalysis [1] and oxidative chemistry associated with damage to biomolecules such as DNA [2] and proteins [3] through to the potential for developing novel mass spectrometry based analytical applications [4]. With regards to the formation of radical ions of amino acids and peptides, several methods have been developed as alternatives to electron ionization (EI) [5]. These include UV photodissociation [6 -11] and ion-electron based techniques such as electron capture dissociation (ECD) [12][13][14][15]. Chemical-based methods that involve low-energy collisioninduced dissociation (CID) [16] of ions generated via electrospray ionization and which can thus be carried out on a wide range of mass spectrometers, merit special discussion. The first, pioneered by Siu, involves carrying out CID of ternary metal complexes to form radical cations of peptides via the redox reaction shown in eq 1 [17][18][19]. To date, doubly charged copper(II) ternary metal complexes (eq 1, where Metal ϭ Cu; L ϭ a range of neutral ligands, x ϭ 2, y ϭ 0) and singly charged metal(III) complexes (eq 1, where Metal ϭ Cr, Mn, Fe, and Co; L ϭ a salen ligand, x ϭ 3, y ϭ 2) have been used to study the formation and reactions of peptide radical ions, including recent contributions from Julia Laskin [20 -23].The second method involves carrying out CID on a cationized peptide containing a functional group with a weak bond, which is susceptible to bond homolysis. A number of different functional groups have been examined to date including: (1) N-terminal azo derivatives

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Section: Mass Spectrometry Experimentsmentioning

confidence: 99%

Gas-phase fragmentation of long-lived cysteine radical cations formed via no loss from protonated S-nitrosocysteine

Ryzhov

Lam

O’Hair

2009

J. Am. Soc. Mass Spectrom.

101

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“…Thus, alkoxide cations of late 3d metals preferentially follow route a, [17][18][19][20][21] whereas route b occurs in the case of high-valent early transition metals. 22,23 Moreover, each route has analogs in the pyrolysis of metal alkoxides in the condensed phase which proceeds via cyclic mechanisms to afford either alkenes or carbonyl compounds depending on the metal and the substituents. 24 Recently, also a decomposition of solid zinc alkoxides to hydroxy complexes has been reported.…”

Section: Introductionmentioning

confidence: 99%

Consecutive fragmentations of the cubane-like zinc cluster [CH₃Zn(O-i-C₃H₇)]₄upon electron ionization

Schröder

Schwarz

Polarz

et al. 2005

Phys. Chem. Chem. Phys.

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“…Noncovalent complexes between nucleobases and sugars promote the cleavage of saccharide bonds via condensation reactions [5]. Furthermore, a number of tetralkylammonium salts undergo gas-phase S N 2 reactions, including those involving organic counter ions (eq 1a) [6,7], inorganic counter ions (eq 2) [8], counter ions derived from biomolecules such as peptides (eq 3a, b) [9], DNA (eq 4a) [10], and glycerophosphocholine adducts (eq 5) [11]. For larger alkyl groups, these S N 2 reactions are often in competition with E2 reactions (eqs 1b, 3c, and 4b).…”

mentioning

confidence: 99%

Sources of artefacts in the electrospray ionization mass spectra of saturated diacylglycerophosphocholines: From condensed phase hydrolysis reactions through to gas phase intercluster reactions

James

Perugini

O’Hair

2006

J. Am. Soc. Mass Spectrom.

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The mass spectra of diacylglycerophosphocholine phospholipids comprised of saturated fatty acids (1,2-dipentanoyl-sn-glycero-3-phosphocholine (D5PC); 1,2-dihexanoyl-sn-glycero-3-phosphocholine (D6PC), and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (D14PC)) are sensitive to the electrospray ionization (ESI) conditions. When fresh solutions of phospholipid in 10 mM ammonium acetate are subjected to ESI, protonated oligomeric clusters, [DxPC n ϩ H] ϩ (x ϭ 5, 6, and 14) are observed in the following different types of mass spectrometers: 3D-quadrupole ion trap; linear ion trap, and triple quadrupole. The formation of the protonated cluster ions is not unique to the ion trap instruments, although they tend to be more abundant in these instruments. As the ESI solutions age, new ions are observed, which correspond to acid-catalyzed solution phase deacylation reactions. The collision induced dissociation fragmentation reactions of the oligomer cluster ions exhibit a distinct dependence on the cluster size, with the larger clusters (n Ͼ 2) simply fragmenting via the loss of lipid monomers. In contrast, the fragmentation of the dimeric cluster ion is unique, resulting in a number of additional reactions including covalent bond formation via intermolecular cluster S N 2 reactions and S N 2 transfer of a methyl group. The nature of the charge has a significant role in the formation of products via these intermolecular cluster reactions. Changing the head group to phosphoethanolamine "switches off" the S N 2 reactions, while changing the cation from a proton to either a sodium or a potassium ion, diminishes the intermolecular reactions relative to monomer loss. Semi empirical PM3 calculations on [D6PC 2 ϩ H] ϩ suggest that the S N 2 reactions are thermodynamically favored over simple monomer loss. These results have important implications in the field of lipidomics. (J Am Soc Mass Spectrom 2006, 17, 384 -394)

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Catalytic Gas Phase Oxidation of Methanol to Formaldehyde

Cited by 246 publications

References 53 publications

Gas-phase fragmentation of long-lived cysteine radical cations formed via no loss from protonated S-nitrosocysteine

Gas-phase fragmentation of long-lived cysteine radical cations formed via no loss from protonated S-nitrosocysteine

Consecutive fragmentations of the cubane-like zinc cluster [CH₃Zn(O-i-C₃H₇)]₄upon electron ionization

Sources of artefacts in the electrospray ionization mass spectra of saturated diacylglycerophosphocholines: From condensed phase hydrolysis reactions through to gas phase intercluster reactions

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Catalytic Gas Phase Oxidation of Methanol to Formaldehyde

Cited by 246 publications

References 53 publications

Gas-phase fragmentation of long-lived cysteine radical cations formed via no loss from protonated S-nitrosocysteine

Gas-phase fragmentation of long-lived cysteine radical cations formed via no loss from protonated S-nitrosocysteine

Consecutive fragmentations of the cubane-like zinc cluster [CH3Zn(O-i-C3H7)]4upon electron ionization

Sources of artefacts in the electrospray ionization mass spectra of saturated diacylglycerophosphocholines: From condensed phase hydrolysis reactions through to gas phase intercluster reactions

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Consecutive fragmentations of the cubane-like zinc cluster [CH₃Zn(O-i-C₃H₇)]₄upon electron ionization