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Closely spaced external standard: a universal method of achieving 5 ppm mass accuracy over the entire MALDI plate in axial matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.
Rapid Commun Mass Spectrom. 2003; 17(19):2177-87.RC

Abstract

Close deposition of the sample and external standard was used in axial matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) to achieve mass accuracy equivalent to that obtained with an internal standard across the entire MALDI plate. In this work, the sample and external standard were deposited by continuous deposition in separate traces, each approximately 200 micro m wide. The dependence of the mass accuracy on the distance between the sample and standard traces was determined across a MALDI target plate with dimensions of 57.5 mm x 57.0 mm by varying the gap between the traces from 100 micro m to 4 mm. During acquisition, two adjacent traces were alternately irradiated with a 200-Hz laser, such that the peaks in the resulting mass spectra combined the sample and external standard. Ion suppression was not observed even when the peptide concentrations in the two traces differed by more than two orders of magnitude. The five peaks from the external standard trace were used in a four-term mass calibration of the masses of the sample trace. The average accuracy across the whole plate with this method was 5 ppm when peaks of the sample trace had signal-to-noise ratios of at least 30 and the gap between the traces was approximately 100 micro m. This approach was applied to determining peptide masses of a reversed-phase liquid chromatographic (LC) separation of a tryptic digest of beta-galactosidase deposited as a long serpentine trace across the MALDI plate, with accuracy comparable to that obtainable using internal calibration. In addition, the eluent from reversed-phase LC separation of a strong cation-exchange fraction containing tryptic peptides from a yeast lysate along with the closely placed external standard was deposited on the MALDI plate. The data obtained in the MS and MS/MS modes on a MALDI-TOF/TOF mass spectrometer were combined and used in database searching with MASCOT. Since the significant score is a function of mass accuracy in the MS mode, database searching with high mass accuracy reduced the number of false positives and also added peptides which otherwise would have been eliminated at lower mass accuracy (false negatives).

Authors+Show Affiliations

Barnett Institute and Department of Chemistry, Northeastern University, Boston, MA 02115, USA.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

14515315

Citation

Moskovets, Eugene, et al. "Closely Spaced External Standard: a Universal Method of Achieving 5 Ppm Mass Accuracy Over the Entire MALDI Plate in Axial Matrix-assisted Laser Desorption/ionization Time-of-flight Mass Spectrometry." Rapid Communications in Mass Spectrometry : RCM, vol. 17, no. 19, 2003, pp. 2177-87.
Moskovets E, Chen HS, Pashkova A, et al. Closely spaced external standard: a universal method of achieving 5 ppm mass accuracy over the entire MALDI plate in axial matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Rapid Commun Mass Spectrom. 2003;17(19):2177-87.
Moskovets, E., Chen, H. S., Pashkova, A., Rejtar, T., Andreev, V., & Karger, B. L. (2003). Closely spaced external standard: a universal method of achieving 5 ppm mass accuracy over the entire MALDI plate in axial matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Rapid Communications in Mass Spectrometry : RCM, 17(19), 2177-87.
Moskovets E, et al. Closely Spaced External Standard: a Universal Method of Achieving 5 Ppm Mass Accuracy Over the Entire MALDI Plate in Axial Matrix-assisted Laser Desorption/ionization Time-of-flight Mass Spectrometry. Rapid Commun Mass Spectrom. 2003;17(19):2177-87. PubMed PMID: 14515315.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Closely spaced external standard: a universal method of achieving 5 ppm mass accuracy over the entire MALDI plate in axial matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. AU - Moskovets,Eugene, AU - Chen,Hsuan-Shen, AU - Pashkova,Anna, AU - Rejtar,Tomas, AU - Andreev,Viktor, AU - Karger,Barry L, PY - 2003/9/30/pubmed PY - 2004/1/13/medline PY - 2003/9/30/entrez SP - 2177 EP - 87 JF - Rapid communications in mass spectrometry : RCM JO - Rapid Commun Mass Spectrom VL - 17 IS - 19 N2 - Close deposition of the sample and external standard was used in axial matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) to achieve mass accuracy equivalent to that obtained with an internal standard across the entire MALDI plate. In this work, the sample and external standard were deposited by continuous deposition in separate traces, each approximately 200 micro m wide. The dependence of the mass accuracy on the distance between the sample and standard traces was determined across a MALDI target plate with dimensions of 57.5 mm x 57.0 mm by varying the gap between the traces from 100 micro m to 4 mm. During acquisition, two adjacent traces were alternately irradiated with a 200-Hz laser, such that the peaks in the resulting mass spectra combined the sample and external standard. Ion suppression was not observed even when the peptide concentrations in the two traces differed by more than two orders of magnitude. The five peaks from the external standard trace were used in a four-term mass calibration of the masses of the sample trace. The average accuracy across the whole plate with this method was 5 ppm when peaks of the sample trace had signal-to-noise ratios of at least 30 and the gap between the traces was approximately 100 micro m. This approach was applied to determining peptide masses of a reversed-phase liquid chromatographic (LC) separation of a tryptic digest of beta-galactosidase deposited as a long serpentine trace across the MALDI plate, with accuracy comparable to that obtainable using internal calibration. In addition, the eluent from reversed-phase LC separation of a strong cation-exchange fraction containing tryptic peptides from a yeast lysate along with the closely placed external standard was deposited on the MALDI plate. The data obtained in the MS and MS/MS modes on a MALDI-TOF/TOF mass spectrometer were combined and used in database searching with MASCOT. Since the significant score is a function of mass accuracy in the MS mode, database searching with high mass accuracy reduced the number of false positives and also added peptides which otherwise would have been eliminated at lower mass accuracy (false negatives). SN - 0951-4198 UR - https://www.unboundmedicine.com/medline/citation/14515315/Closely_spaced_external_standard:_a_universal_method_of_achieving_5_ppm_mass_accuracy_over_the_entire_MALDI_plate_in_axial_matrix_assisted_laser_desorption/ionization_time_of_flight_mass_spectrometry_ L2 - https://doi.org/10.1002/rcm.1158 DB - PRIME DP - Unbound Medicine ER -