Determination of relative gas-phase basicities by the proton-transfer equilibrium technique and the kinetic method in a quadrupole ion-trap

Brodbelt-Lustig, J.; Cooks, R. Graham

doi:10.1016/0039-9140(89)80104-3

Cited by 64 publications

(55 citation statements)

References 27 publications

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“…So far, ESI has not been used for the estimation of PA values of MALDI matrices. In the present study, we estimated PA values of fifteen MALDI matrices under electrospray ionization conditions, which is easier and more broadly applicable than fast atom bombardment or chemical ionization techniques, using the kinetic method [35,36].Estimation of PA values by the kinetic method involves measurement of peak height ratios of the protonated monomers of the compound with unknown PA and that of the reference base with known PA values, generated from the collision induced dissociation of the corresponding proton-bound heterodimers. According to the kinetic method, the ratio of rate constants (k A and k B ) for the competitive dissociation of a cluster ion comprised of the compound of interest and a reference compound, eq 1, can be expressed as eq 2 [37, 38].…”

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Estimation of the proton affinity values of fifteen matrix-assisted laser desorption/ionization matrices under electrospray ionization conditions using the kinetic method

Mirza

Raju

Vairamani

2004

J. Am. Soc. Mass Spectrom.

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The kinetic method, which is known to be simple, fast and precise, is used for the measurement of proton affinity values of fifteen selected matrix-assisted laser desorption/ionization matrices under electrospray ionization conditions. The stabilization of [ T he most exciting innovations in the last decade for the analysis of non-volatile, high molecular weight compounds is the development of new mass spectral techniques like matrix-assisted laser desorption/ionization (MALDI) [1][2][3] and electrospray ionization (ESI) [4]. MALDI has been successfully applied for the analysis of peptides and proteins [5][6][7][8][9][10][11], oligonucleotides and nucleic acids [12,13], carbohydrates [14 -16], and synthetic polymers [17][18][19][20][21]. Despite its wide range of applications and many fundamental studies [22][23][24][25][26][27][28][29][30], there is a need for better understanding of the MALDI process, to improve ion yields, to gain access to new classes of compounds, and to provide rational guidelines for matrix selection, which play crucial roles in sample analysis. In the discussions of the ionization mechanism, proton-transfer reactions have a very prominent role. The protonated analyte is presumably produced by gas-phase reactions between matrix ions and analyte molecules. Thermochemical data like gas phase basicities (GB) and proton affinities (PA) of the matrices may contribute to better understanding of the MALDI processes.To date, very few studies have been carried out for the measurement of GB and PA of MALDI matrices [31][32][33][34]. The PA values that have been reported for MALDI matrices are inconsistent with one another because of intrinsic errors in the different methods, due to sampling of ions of different internal energy, and because of the use of different ionization techniques in these studies. So far, ESI has not been used for the estimation of PA values of MALDI matrices. In the present study, we estimated PA values of fifteen MALDI matrices under electrospray ionization conditions, which is easier and more broadly applicable than fast atom bombardment or chemical ionization techniques, using the kinetic method [35,36].Estimation of PA values by the kinetic method involves measurement of peak height ratios of the protonated monomers of the compound with unknown PA and that of the reference base with known PA values, generated from the collision induced dissociation of the corresponding proton-bound heterodimers. According to the kinetic method, the ratio of rate constants (k A and k B ) for the competitive dissociation of a cluster ion comprised of the compound of interest and a reference compound, eq 1, can be expressed as eq 2 [37, 38].(1) Experimental MaterialsThe MALDI matrices, 4-hydroxy-␣-cyanocinnamic acid (4HCCA), 2,5-dihydroxy benzoic acid (gentisic acid, GA), 5-methoxysalicylic acid (MSA), trans-3, 5-dimethoxy-4-hydroxycinnamic acid (sinapinic acid, SA), 1,8,9-anthracenetriol (dithranol, DT), 2,4,6-trihydroxyacetophenone (THAP), trans-3-indoleacrylic acid (IAA), 3-hydroxypicoli...

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Estimation of the proton affinity values of fifteen matrix-assisted laser desorption/ionization matrices under electrospray ionization conditions using the kinetic method

Mirza

Raju

Vairamani

2004

J. Am. Soc. Mass Spectrom.

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“…The ability of the quadrupole ion trap to selectively isolate ions and monitor product formation as a function of time makes it applicable to equilibrium determinations. 28 The only concern in such studies is the uncertainty in the temperature of the ions. Many temperatures have been reported for the ion trap, ranging from 363 to 3300 K .…”

Section: Resultsmentioning

confidence: 99%

Use of Borinium Ions as Probes of Steric Effects in Gas-phase Ion-Molecule Complexes

Isbell

Brodbelt

1996

Rapid Commun. Mass Spectrom.

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The relative free energies of binding of the dimethoxy borinium ion to several substituted pyridines were determined using the equilibrium method and were found to correlate well with relative gas-phase basicities except in the case in which different sterics were present near the site of cation attachment. Dimethoxy borinium ion binds to 3,5-dimethylpyridine and 3,4-dimethylpyridine 2.5+0.4 and 3.5+0.3 kcal/mole more strongly than it does to 3-methylpyridine. 2,4-Dimethylpyridine shows a 2.0+0.4 kcal/mole preference over 2-methylpyridine for dimethoxy borinium ion attachment. This difference is in agreement with the difference in gas-phase basicities of these two compounds, suggesting the borinium ion binds to the same position as the proton. 2,3-Dimethylpyridine deviated from this trend, with its borinium ion complex being 1.5+0.4 kcal/mole less stable than that of 3-methylpyridine.

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“…12,13,14b. 15125 1~s 6,IS weak dependence of ion intensity ratio on the average center-of-mass kinetic energy of the parent ions was evidenced. Meanwhile, we started an FTICR study of the gas-phase basicity of phosphoryl and sulfonyl compounds.…”

Section: Ln(klk)=ln[l(bh')il(bh')]mentioning

confidence: 91%

“…cm=Ek, lab(McgiMcg+Mian) (6) where Mcg is the mass of the collision gas (argon, in our case) and M,,,, is the mass of the proton-bound dimer.…”

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confidence: 99%

On the Use of the Kinetic Method for the Determination of Proton Affinities by Fourier-transform Ion Cyclotron Resonance Mass Spectrometry

Decouzon¹,

Gal²,

Herreros³

et al. 1996

Rapid Commun. Mass Spectrom.

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Determination of relative gas-phase basicities by the proton-transfer equilibrium technique and the kinetic method in a quadrupole ion-trap

Cited by 64 publications

References 27 publications

Estimation of the proton affinity values of fifteen matrix-assisted laser desorption/ionization matrices under electrospray ionization conditions using the kinetic method

Estimation of the proton affinity values of fifteen matrix-assisted laser desorption/ionization matrices under electrospray ionization conditions using the kinetic method

Use of Borinium Ions as Probes of Steric Effects in Gas-phase Ion-Molecule Complexes

On the Use of the Kinetic Method for the Determination of Proton Affinities by Fourier-transform Ion Cyclotron Resonance Mass Spectrometry

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