The Experts below are selected from a list of 162 Experts worldwide ranked by ideXlab platform
Randy W. Purves - One of the best experts on this subject based on the ideXlab platform.
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High field asymmetric waveform ion mobility spectrometry-mass spectrometry: an investigation of Leucine Enkephalin ions produced by electrospray ionization
Journal of the American Society for Mass Spectrometry, 1999Co-Authors: Roger Guevremont, Randy W. PurvesAbstract:High field asymmetric waveform ion mobility spectrometry (FAIMS) provides atmospheric pressure, room temperature, low-resolution separation of gas-phase ions. The FAIMS analyzer acts as an ion filter that can continuously transmit one type of ion, independent of m/z . The combination of FAIMS with electrospray ionization and mass spectrometry (ESI-FAIMS-MS) is a powerful technique and is used in this study to investigate the cluster ions of Leucine Enkephalin (YGGFL). Separation by FAIMS of Leucine Enkephalin ions having the same m/z ( m/z 556.5), [M + H]^+ and [2M + 2H]^2+, was observed. In addition, four complex ions of Leucine Enkephalin, [2M + H]^+, [4M + 2H]^2+, [6M + 3H]^3+, and [8M + 4H]^4+, all having m/z 1112, were shown to be separated in FAIMS. Fragmentation of ions as the result of harsh conditions within the mass spectrometer interface (FAIMS-MS) was shown to provide similar information to that obtained from MS/MS experiments in conventional ESI-MS.
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High field asymmetric waveform ion mobility spectrometry–mass spectrometry: an investigation of Leucine Enkephalin ions produced by electrospray ionization
Journal of the American Society for Mass Spectrometry, 1999Co-Authors: Roger Guevremont, Randy W. PurvesAbstract:High field asymmetric waveform ion mobility spectrometry (FAIMS) provides atmospheric pressure, room temperature, low-resolution separation of gas-phase ions. The FAIMS analyzer acts as an ion filter that can continuously transmit one type of ion, independent of m/z. The combination of FAIMS with electrospray ionization and mass spectrometry (ESI-FAIMS-MS) is a powerful technique and is used in this study to investigate the cluster ions of Leucine Enkephalin (YGGFL). Separation by FAIMS of Leucine Enkephalin ions having the same m/z (m/z 556.5), [M + H]+ and [2M + 2H]2+, was observed. In addition, four complex ions of Leucine Enkephalin, [2M + H]+, [4M + 2H]2+, [6M + 3H]3+, and [8M + 4H]4+, all having m/z 1112, were shown to be separated in FAIMS. Fragmentation of ions as the result of harsh conditions within the mass spectrometer interface (FAIMS-MS) was shown to provide similar information to that obtained from MS/MS experiments in conventional ESI-MS.
Károly Vékey - One of the best experts on this subject based on the ideXlab platform.
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Leucine Enkephalin--a mass spectrometry standard
Mass spectrometry reviews, 2010Co-Authors: Judit Sztáray, Antony Memboeuf, László Drahos, Károly VékeyAbstract:The present article reviews the mass spectrometric fragmentation processes and fragmentation energetics of Leucine Enkephalin, a commonly used peptide, which has been studied in detail and has often been used as a standard or reference compound to test novel instrumentation, new methodologies, or to tune instruments. The main purpose of the article is to facilitate its use as a reference material; therefore, all available mass spectrometry-related information on Leucine Enkephalin has been critically reviewed and summarized. The fragmentation mechanism of Leucine Enkephalin is typical for a small peptide; but is understood far better than that of most other compounds. Because ion ratios in the MS/MS spectra indicate the degree of excitation, Leucine Enkephalin is often used as a thermometer molecule in electrospray or matrix-assisted laser desorption ionization (ESI or MALDI). Other parameters described for Leucine Enkephalin include collisional cross-section and energy transfer; proton affinity and gas-phase basicity; radiative cooling rate; and vibrational frequencies. The lowest-energy fragmentation channel of Leucine Enkephalin is the MH+ → b4 process. All available data for this process have been re-evaluated. It was found that, although the published Ea values were significantly different, the corresponding Gibbs free energy change showed good agreement (1.32 ± 0.07 eV) in various studies. Temperature- and energy-dependent rate constants were re-evaluated with an Arrhenius plot. The plot showed good linear correlation among all data (R2 = 0.97), spanned over a 9 orders of magnitude range in the rate constants and yielded 1.14 eV activation energy and 1011.0 sec−1 pre-exponential factor. Accuracy (including random and systematic errors, with a 95% confidence interval) is ±0.05 eV and 10±0.5 sec−1, respectively. The activation entropy at 470 K that corresponds to this reaction is −38.1 ± 9.6 J mol−1 K−1. We believe that these re-evaluated values are by far the most accurate activation parameters available at present for a protonated peptide and can be considered as “consensus” values; results on other processes might be compared to this reference value. © 2010 Wiley Periodicals, Inc., Mass Spec Rev 30:298–320, 2011
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Leucine Enkephalin--a mass spectrometry standard.
Mass Spectrometry Reviews, 2009Co-Authors: Judit Sztáray, Antony Memboeuf, László Drahos, Károly VékeyAbstract:The present article reviews the mass spectrometric fragmentation processes and fragmentation energetics of Leucine Enkephalin, a commonly used peptide, which has been studied in detail and has often been used as a standard or reference compound to test novel instrumentation, new methodologies, or to tune instruments. The main purpose of the article is to facilitate its use as a reference material; therefore, all available mass spectrometry-related information on Leucine Enkephalin has been critically reviewed and summarized. The fragmentation mechanism of Leucine Enkephalin is typical for a small peptide; but is understood far better than that of most other compounds. Because ion ratios in the MS/MS spectra indicate the degree of excitation, Leucine Enkephalin is often used as a thermometer molecule in electrospray or matrix-assisted laser desorption ionization (ESI or MALDI). Other parameters described for Leucine Enkephalin include collisional cross-section and energy transfer; proton affinity and gas-phase basicity; radiative cooling rate; and vibrational frequencies. The lowest-energy fragmentation channel of Leucine Enkephalin is the MH(+) → b(4) process. All available data for this process have been re-evaluated. It was found that, although the published E(a) values were significantly different, the corresponding Gibbs free energy change showed good agreement (1.32 ± 0.07 eV) in various studies. Temperature- and energy-dependent rate constants were re-evaluated with an Arrhenius plot. The plot showed good linear correlation among all data (R(2) = 0.97), spanned over a 9 orders of magnitude range in the rate constants and yielded 1.14 eV activation energy and 10(11.0) sec(-1) pre-exponential factor. Accuracy (including random and systematic errors, with a 95% confidence interval) is ±0.05 eV and 10(±0.5) sec(-1), respectively. The activation entropy at 470 K that corresponds to this reaction is -38.1 ± 9.6 J mol(-1) K(-1). We believe that these re-evaluated values are by far the most accurate activation parameters available at present for a protonated peptide and can be considered as "consensus" values; results on other processes might be compared to this reference value.
Roger Guevremont - One of the best experts on this subject based on the ideXlab platform.
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High field asymmetric waveform ion mobility spectrometry-mass spectrometry: an investigation of Leucine Enkephalin ions produced by electrospray ionization
Journal of the American Society for Mass Spectrometry, 1999Co-Authors: Roger Guevremont, Randy W. PurvesAbstract:High field asymmetric waveform ion mobility spectrometry (FAIMS) provides atmospheric pressure, room temperature, low-resolution separation of gas-phase ions. The FAIMS analyzer acts as an ion filter that can continuously transmit one type of ion, independent of m/z . The combination of FAIMS with electrospray ionization and mass spectrometry (ESI-FAIMS-MS) is a powerful technique and is used in this study to investigate the cluster ions of Leucine Enkephalin (YGGFL). Separation by FAIMS of Leucine Enkephalin ions having the same m/z ( m/z 556.5), [M + H]^+ and [2M + 2H]^2+, was observed. In addition, four complex ions of Leucine Enkephalin, [2M + H]^+, [4M + 2H]^2+, [6M + 3H]^3+, and [8M + 4H]^4+, all having m/z 1112, were shown to be separated in FAIMS. Fragmentation of ions as the result of harsh conditions within the mass spectrometer interface (FAIMS-MS) was shown to provide similar information to that obtained from MS/MS experiments in conventional ESI-MS.
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High field asymmetric waveform ion mobility spectrometry–mass spectrometry: an investigation of Leucine Enkephalin ions produced by electrospray ionization
Journal of the American Society for Mass Spectrometry, 1999Co-Authors: Roger Guevremont, Randy W. PurvesAbstract:High field asymmetric waveform ion mobility spectrometry (FAIMS) provides atmospheric pressure, room temperature, low-resolution separation of gas-phase ions. The FAIMS analyzer acts as an ion filter that can continuously transmit one type of ion, independent of m/z. The combination of FAIMS with electrospray ionization and mass spectrometry (ESI-FAIMS-MS) is a powerful technique and is used in this study to investigate the cluster ions of Leucine Enkephalin (YGGFL). Separation by FAIMS of Leucine Enkephalin ions having the same m/z (m/z 556.5), [M + H]+ and [2M + 2H]2+, was observed. In addition, four complex ions of Leucine Enkephalin, [2M + H]+, [4M + 2H]2+, [6M + 3H]3+, and [8M + 4H]4+, all having m/z 1112, were shown to be separated in FAIMS. Fragmentation of ions as the result of harsh conditions within the mass spectrometer interface (FAIMS-MS) was shown to provide similar information to that obtained from MS/MS experiments in conventional ESI-MS.
Judit Sztáray - One of the best experts on this subject based on the ideXlab platform.
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Leucine Enkephalin--a mass spectrometry standard
Mass spectrometry reviews, 2010Co-Authors: Judit Sztáray, Antony Memboeuf, László Drahos, Károly VékeyAbstract:The present article reviews the mass spectrometric fragmentation processes and fragmentation energetics of Leucine Enkephalin, a commonly used peptide, which has been studied in detail and has often been used as a standard or reference compound to test novel instrumentation, new methodologies, or to tune instruments. The main purpose of the article is to facilitate its use as a reference material; therefore, all available mass spectrometry-related information on Leucine Enkephalin has been critically reviewed and summarized. The fragmentation mechanism of Leucine Enkephalin is typical for a small peptide; but is understood far better than that of most other compounds. Because ion ratios in the MS/MS spectra indicate the degree of excitation, Leucine Enkephalin is often used as a thermometer molecule in electrospray or matrix-assisted laser desorption ionization (ESI or MALDI). Other parameters described for Leucine Enkephalin include collisional cross-section and energy transfer; proton affinity and gas-phase basicity; radiative cooling rate; and vibrational frequencies. The lowest-energy fragmentation channel of Leucine Enkephalin is the MH+ → b4 process. All available data for this process have been re-evaluated. It was found that, although the published Ea values were significantly different, the corresponding Gibbs free energy change showed good agreement (1.32 ± 0.07 eV) in various studies. Temperature- and energy-dependent rate constants were re-evaluated with an Arrhenius plot. The plot showed good linear correlation among all data (R2 = 0.97), spanned over a 9 orders of magnitude range in the rate constants and yielded 1.14 eV activation energy and 1011.0 sec−1 pre-exponential factor. Accuracy (including random and systematic errors, with a 95% confidence interval) is ±0.05 eV and 10±0.5 sec−1, respectively. The activation entropy at 470 K that corresponds to this reaction is −38.1 ± 9.6 J mol−1 K−1. We believe that these re-evaluated values are by far the most accurate activation parameters available at present for a protonated peptide and can be considered as “consensus” values; results on other processes might be compared to this reference value. © 2010 Wiley Periodicals, Inc., Mass Spec Rev 30:298–320, 2011
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Leucine Enkephalin--a mass spectrometry standard.
Mass Spectrometry Reviews, 2009Co-Authors: Judit Sztáray, Antony Memboeuf, László Drahos, Károly VékeyAbstract:The present article reviews the mass spectrometric fragmentation processes and fragmentation energetics of Leucine Enkephalin, a commonly used peptide, which has been studied in detail and has often been used as a standard or reference compound to test novel instrumentation, new methodologies, or to tune instruments. The main purpose of the article is to facilitate its use as a reference material; therefore, all available mass spectrometry-related information on Leucine Enkephalin has been critically reviewed and summarized. The fragmentation mechanism of Leucine Enkephalin is typical for a small peptide; but is understood far better than that of most other compounds. Because ion ratios in the MS/MS spectra indicate the degree of excitation, Leucine Enkephalin is often used as a thermometer molecule in electrospray or matrix-assisted laser desorption ionization (ESI or MALDI). Other parameters described for Leucine Enkephalin include collisional cross-section and energy transfer; proton affinity and gas-phase basicity; radiative cooling rate; and vibrational frequencies. The lowest-energy fragmentation channel of Leucine Enkephalin is the MH(+) → b(4) process. All available data for this process have been re-evaluated. It was found that, although the published E(a) values were significantly different, the corresponding Gibbs free energy change showed good agreement (1.32 ± 0.07 eV) in various studies. Temperature- and energy-dependent rate constants were re-evaluated with an Arrhenius plot. The plot showed good linear correlation among all data (R(2) = 0.97), spanned over a 9 orders of magnitude range in the rate constants and yielded 1.14 eV activation energy and 10(11.0) sec(-1) pre-exponential factor. Accuracy (including random and systematic errors, with a 95% confidence interval) is ±0.05 eV and 10(±0.5) sec(-1), respectively. The activation entropy at 470 K that corresponds to this reaction is -38.1 ± 9.6 J mol(-1) K(-1). We believe that these re-evaluated values are by far the most accurate activation parameters available at present for a protonated peptide and can be considered as "consensus" values; results on other processes might be compared to this reference value.
Günther Hochhaus - One of the best experts on this subject based on the ideXlab platform.
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Leucine Enkephalin-tyrosinase reaction products — Identification and biological activity
Biochimica et biophysica acta, 1994Co-Authors: Véronique Larsimont, Laszlo Prokai, Günther HochhausAbstract:Abstract Leucine Enkephalin (1 mM) was reacted with mushroom tyrosinase under reductive conditions (ascorbic acid, 50 mM). Reaction products were isolated by high-performance liquid chromatography and identified using electrospray ionization mass spectrometry. The products of the reaction were found to be hydroxylated at the Tyr 1 moiety of the peptide. The major product was a monohydroxylated derivative of Leucine Enkephalin ([HO-Tyr 1 ]LE) and the minor product of the reaction was a dihydroxylated derivative ([(HO) 2 -Tyr 1 ]LE). The affinity of [HO-Tyr 1 ]LE to receptors in rat brain homogenate was compared to that of Leucine Enkephalin itself. Hydroxylation of LE was found to decrease receptor affinity to both μ and δ opioid receptor sites by a factor of about 20.
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Leucine Enkephalin tyrosinase reaction products identification and biological activity
Biochimica et Biophysica Acta, 1994Co-Authors: Véronique Larsimont, Laszlo Prokai, Günther HochhausAbstract:Abstract Leucine Enkephalin (1 mM) was reacted with mushroom tyrosinase under reductive conditions (ascorbic acid, 50 mM). Reaction products were isolated by high-performance liquid chromatography and identified using electrospray ionization mass spectrometry. The products of the reaction were found to be hydroxylated at the Tyr 1 moiety of the peptide. The major product was a monohydroxylated derivative of Leucine Enkephalin ([HO-Tyr 1 ]LE) and the minor product of the reaction was a dihydroxylated derivative ([(HO) 2 -Tyr 1 ]LE). The affinity of [HO-Tyr 1 ]LE to receptors in rat brain homogenate was compared to that of Leucine Enkephalin itself. Hydroxylation of LE was found to decrease receptor affinity to both μ and δ opioid receptor sites by a factor of about 20.