LC/MS Unknown Identifications Using MSMS Libraries Part VI: MS Interpreter Correlation of Substructure to MSMS Ions | LabRulez LCMS

LC/MS Unknown Identifications Using MSMS Libraries Part VI: MS Interpreter Correlation of Substructure to MSMS Ions

We, 21.4.2021
| Original article from: Mass Spec Interpretation Services/James Little
A series of videos exploring the use of NIST Search Software for the identification of unknowns using tandem (MS/MS) spectra.
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Mass Spec Interpretation Services/James Little: MS Interpreter Correlation of Substructure to MSMS Ions

MS/MS (Tandem) spectra can be used to identify unknowns employing library searches. This is accomplished in much the same approach as that employed for EI GC-MS with the NIST search software. The much improved NIST Search Version 2.4 is included with the 2020 library release.

I will attempt to introduce the user to the use of the NIST Version 2.4 search software employing NIST, Wiley, “crowd-sourced (MoNA)”, and user libraries for the identification of unknowns.

NIST has an ambitious program to extend their already comprehensive, high-quality MS/MS databases.

See the following link: NIST Pipeline for Extending MS/MS Libraries

This involves a very comprehensive process for selecting pertinent compounds for purchase and subsequent analyses. The problem with variability of the spectra is reduced by analyzing the samples on a variety of instruments at a variety of energy levels (20 steps). In addition, many different precursor ions and fragment ions are characterized (MSⁿ). This has already led to a very large high quality library of accurate mass MS/MS spectra in the 2020 release version (31K compounds/1.3 M spectra) and the effort is ongoing.

The Part VI will cover:

Detailed Handouts including tables of content are available in the LabRulezLCMS library.

  • Introduction of Presenter, James Little
  • Table of Contents
  • Series Topics
  • Help Files for NIST Search
  • NIST Software in General is “Windows Compliant”
  • Session Topics
  • Adding a Structure to a Spectrum
  • Sending Spectrum with Structure to MS Interpereter
  • Processing Data in MS Interpreter
  • Suggested Default Settings
  • Displaying the Propose Substructures Correlated to Ions
  • Stepping through More Than One Proposed Structure
  • Lassoing Structures Manually
  • Processing Any Entry in NIST Search with structure/spectrum
  • Direct Structure Paste in MS Interpreter
  • Processing MS/MS Spectra Containing Isotopic Clusters
  • Live YouTube Demonstration
  • References with Internet Links
  • Acknowledgements

Future parts will focus on:

  • Part VII: Using and Creating Other MSMS Libraries
  • Part VIII: Identification of Unknowns with “Spectraless” Libraries

The past sections have focused on:

James Little/Mass Spec Interpretation Services
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