LC/MS Unknown Identifications Using MSMS Libraries Part VII: Using and Creating Other MSMS Libraries
Mass Spec Interpretation Services/James Little: Using and Creating Other MSMS 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 VII 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
- Read This Before Utilizing Handout
- Philosophy on Incorporating User and Commercial Libraries in Identifications
- User Libraries Converted and Approach
- NIST Lib2NIST Utility for Library Conversions
- Accessing Lib2NIST Utility
- Quality of MoNA and Converting to NIST format
- Low Resolution (lr_) versus High Resolution MSMS NIST Libraries
- Problems Converting and Searching User Libraries and “Work-Arounds”
- Composition of the MoNA Libraries and Structures in MoNA GCMS Library
- Conversion of Wiley Commercial Libraries with Lib2NIST
- Conversion of Personal User Library with no Precursor_m/z field
- PowerShell Script for Adding Precursor_m/z to Personal User Library
- Creating/Adding User Library within NIST Search Program
- What If My Imported Library Spectrum Contained No Precursor_m/z Field?
- What IF I Need to Add Several Different Fields for a Set of Spectra?
- “Re(Index)” Library Indices After Additions or Creating New Library
- Automatic Distribution of Eastman Libraries Over Network
- Live Demo on YouTubeWebinar References (Internet Links)
Future parts will focus on:
- Part VIII: Identification of Unknowns with “Spectraless” Libraries