ChemInform Abstract: KINETIC ISOTOPE EFFECTS FOR REACTIONS OF METHYL FORMATE‐METHOXYL‐(18)O

Sawyer, Charles B.; Kirsch, Jack F.

doi:10.1002/chin.197402094

Cited by 7 publications

(23 citation statements)

References 1 publication

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“…The linearity of the data and the standard deviations of the replicates indicate that the precision of the isotope ratios obtained from the product ion should be sufficient to permit heavy atom isotope effects to be determined on nucleotides. Similar results were obtained for the protonated base product ion when [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] O]uridine was analyzed (data not shown). The procedures described to obtain and analyze IDs by tandem MS for nucleotides (and peptides [22]) will permit heavy atom isotope effect studies to be conducted on these biomacromolecular substrates.…”

Section: Application To Time-of-flight Mass Analyzers and Tandem Masssupporting

confidence: 79%

“…18 O 1 ]pGp were purified by HPLC (300 mm × 3.9 mm, 10 μm C 18 packing) eluted isocratically using 50 mM diisopropylethylamine (Aldrich), 1% acetic acid in water (pH 4.3) as the mobile phase. For [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] O]uridine, samples were resolved by a gradient of acetonitrile in 0.2 M ammonium acetate (5% -20% acetonitrile in 60 min.). Appropriate fractions containing either uridine, UMP, TMP or pGp were collected.…”

Section: ′-Uridine-[nonbridging-18 O 1 ]Phosphatementioning

confidence: 99%

“…The application of the analysis of isotope ratios by analysis of IDs was extended to tandemquadrupole time of flight mass spectrometry by analysis of [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] O]uridine and UM[ 18 O 1 ]P with an Applied Biosystems Q-STAR. All analyses were performed by direct infusion of the nucleoside/nucleotide in 50% acetonitrile 1% formic acid.…”

Section: Time Of Flight Mass Spectrometrymentioning

confidence: 99%

“…IRMS can only analyze small, non-polar gasses such as CO 2 , N 2 , and H 2 ; thus, this technique can only be used when the atom of interest can be quantitatively converted to one of these gasses. Scintillation counting requires substantial double-labeling schemes involving specific isotopic pairs (usually 3 H and 14 C, although others can be used [10]), again limiting the molecules that can be analyzed.One alternative to these methods is whole molecule mass spectrometry, a technique that was used as early as the 1970s for isotope ratio analysis of formyl-methyl ester and ethanol by gas chromatography quadrupole mass spectrometry (QMS) [11,12]. Today, the development of gentler ionization methods such as electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) allow larger molecules to be analyzed.…”

mentioning

confidence: 99%

“…One alternative to these methods is whole molecule mass spectrometry, a technique that was used as early as the 1970s for isotope ratio analysis of formyl-methyl ester and ethanol by gas chromatography quadrupole mass spectrometry (QMS) [11,12]. Today, the development of gentler ionization methods such as electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) allow larger molecules to be analyzed.…”

mentioning

confidence: 99%

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Inaccuracies in selected ion monitoring determination of isotope ratios obviated by profile acquisition: nucleotide 18O/16O measurements

Cassano

Wang

Anderson

et al. 2007

Analytical Biochemistry

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Precise and accurate measurements of isotopologue distributions (IDs) in biological molecules are needed for the determination of isotope effects, quantitation by isotope dilution and quantifying isotope tracers employed in both metabolic and biophysical studies. While single ion monitoring (SIM) yields significantly greater sensitivity and signal/noise than profile mode acquisitions, we show that small changes in the SIM window width and/or center can alter experimentally determined isotope ratios by up to 5%, resulting in significant inaccuracies. This inaccuracy is attributed to mass granularity, the differential distribution of digital data points across the m/z ranges sampled by SIM. Acquiring data in the profile mode and fitting the data to an equation describing a series of equally spaced and identically shaped peaks eliminates the inaccuracies associated with mass granularity with minimal loss of precision. Additionally a method of using the complete ID profile data that inherently corrects for "spillover" and for the natural abundance ID has been used to determine 18 Keywords isotope ratio; isotopologue distribution; mass isotopomer distribution; tandem mass spectrometry; heavy atom isotope effect; oxygen-18; nucleotide; mass granularity; whole molecule mass spectrometry 1 This work supported by NIH grants GM56740 (M.E.H.), R33 DK07029 (VEA & SP) and a HHMI predoctoral fellowship (A.G.C.). *Corresponding Authors: Vernon E. Anderson and Michael E. Harris, Department of Biochemistry, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4935, Phone: 216-368-2511 (VEA); 216-368-4779 (MEH), Fax: 216-368-3419, Email: vernon.anderson@case.edu; michael.harris@cwru.edu. 3 Current address: Department of Chemistry, Drew University, Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access Author ManuscriptAnal Biochem. Author manuscript; available in PMC 2008 August 1. Published in final edited form as:Anal Biochem. 2007 August 1; 367(1): 28-39. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author ManuscriptHeavy atom isotope effects generated by substituting 13 C, 15 N or 18 O are important tools for probing the mechanisms and transition states of chemical reactions [1], including enzymecatalyzed reactions [2][3][4][5][6][7]. Because the observed effects for isotopic substitution of heavy atoms are extremely small, typically a few percent, they cannot be determined by direct comparison of experimentally determined rate constants. Instead, heavy atom isotope effects are generally measured by internal competition methods that...

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Section: Application To Time-of-flight Mass Analyzers and Tandem Masssupporting

confidence: 79%

Section: ′-Uridine-[nonbridging-18 O 1 ]Phosphatementioning

confidence: 99%

Section: Time Of Flight Mass Spectrometrymentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 3 more Smart Citations

Inaccuracies in selected ion monitoring determination of isotope ratios obviated by profile acquisition: nucleotide 18O/16O measurements

Cassano

Wang

Anderson

et al. 2007

Analytical Biochemistry

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Mechanistic investigations of the hydrolysis of amides, oxoesters and thioesters via kinetic isotope effects and positional isotope exchange

Robins

Fogle

Marlier

2015

Biochimica et Biophysica Acta (BBA) - Proteins and Proteomics

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The hydrolysis of amides, oxoesters and thioesters is an important reaction in both organic chemistry and biochemistry. Kinetic isotope effects (KIEs) are one of the most important physical organic methods for determining the most likely transition state structure and rate-determining step of these reaction mechanisms. This method induces a very small change in reaction rates, which, in turn, results in a minimum disturbance of the natural mechanism. KIE studies were carried out on both the non-enzymatic and the enzyme-catalyzed reactions in an effort to compare both types of mechanisms. In these studies the amides and esters of formic acid were chosen because this molecular structure allowed development of methodology to determine heavy-atom solvent (nucleophile) KIEs. This type of isotope effect is difficult to measure, but is rich in mechanistic information. Results of these investigations point to transition states with varying degrees of tetrahedral character that fit a classical stepwise mechanism. This article is part of a special issue entitled: Enzyme Transition States from Theory and Experiment.

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Multiple Isotope Effects on the Acyl Group Transfer Reactions of Amides and Esters

Marlier

2001

Acc. Chem. Res.

106

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Acyl group transfer reactions, especially those to amides and esters, are important in biochemistry. Multiple kinetic isotope effects for the atoms at the reactive center of these molecules have provided the most detailed bonding picture of the transition state to date. These kinetic isotope effect studies are reviewed for several reactions of formamide, methyl benzoate, and methyl formate. In these cases all the evidence is consistent with a stepwise mechanism, involving tetrahedral intermediates. In the case of p-nitrophenyl acetate, the change to an excellent leaving group causes the tetrahedral intermediates to become kinetically unstable; the kinetic isotope effects are best fitted to a concerted mechanism.

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ChemInform Abstract: KINETIC ISOTOPE EFFECTS FOR REACTIONS OF METHYL FORMATE‐METHOXYL‐(18)O

Cited by 7 publications

References 1 publication

Inaccuracies in selected ion monitoring determination of isotope ratios obviated by profile acquisition: nucleotide 18O/16O measurements

Inaccuracies in selected ion monitoring determination of isotope ratios obviated by profile acquisition: nucleotide 18O/16O measurements

Mechanistic investigations of the hydrolysis of amides, oxoesters and thioesters via kinetic isotope effects and positional isotope exchange

Multiple Isotope Effects on the Acyl Group Transfer Reactions of Amides and Esters

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