LC/MS Unknown Identifications Using MSMS Libraries Part II: NIST Search Software and Libraries
Mass Spec Interpretation Services/James Little: LC/MS Unknown Identifications Using MSMS Libraries Part II: NIST Search Software and Libraries
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 II will cover:
Detailed Handouts including tables of content are available in the LabRulezLCMS library.
- Introduction to Presenter, James Little
- Table of Contents
- Series of Talks: LCMS Unknown Identifications Using MSMS Libraries
- Help Files for NIST Search
- NIST Software in General is “Windows Compliant”
- NIST Tandem Quick Start Guide
- Overview: NIST Mass Spectrometry Software and MSMS Libraries
- Limitations of MSMS Searches for Unknown Identifications
- Three Basic Types of NIST MSMS (Tandem) Searches
- Overall Description for Searching Libraries and Displaying Results
- NIST MSMS (Tandem) Libraries 2020 Release
- Minimizing Number of Results After Search Performed
- Two Types of Ions Filtered with MSMS Hit List Filter Option
- Setting Default Parameters for Similarity Search (7 Steps)
- Setting Default Parameters for Identify MS/MS Search (8 Steps)
- Setting Default Parameters for MS/MS Hybrid Search (9 Steps)
- Searching Demonstration (Live YouTube)
- Presentation References (Internet Hyperlinks)
Future parts will focus on:
- Part III: More Detailed Discussion of MSMS Hybrid Search
- Part IV: Importing MSMS Spectra
- Part V: NIST Structure Searches
- Part VI: MS Interpreter Correlation of Substructure to MSMS Ions
- Part VII: Using and Creating Other MSMS Libraries
- Part VIII: Identification of Unknowns with “Spectraless” Libraries