Mass Spectral Analysis Using Isotopic Envelope Deconvolution
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Solution Overview
Problem
Conventional mass spectrometry methods face challenges in accurately identifying and quantifying ions, especially in cases where monoisotopic masses differ by small fractions and are not baseline-resolved, leading to ambiguity and error in molecular formula searches, particularly for larger molecules like peptides and proteins.
Innovation Solution
A new search algorithm utilizing multiple observable isotopes and profile mode mass spectral data to deconvolute overlapped isotopes, allowing for the identification and quantification of ions on conventional mass spectrometers with unit mass resolution, without relying on peak picking or centroiding, and incorporating comprehensive mass spectral calibration for accurate elemental composition determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional mass spectrometry methods are used with unit mass resolution, then the instrument is simple and cost-effective, but the ability to resolve and identify ions with closely spaced monoisotopic masses is poor
Solution Approach 1:
The patent transitions from one-dimensional peak picking (single mass value) to utilizing the entire isotopic envelope profile across multiple mass values. By analyzing the complete isotopic distribution pattern rather than individual peaks, the method extracts additional dimensional information that enables precise identification even with unit mass resolution instruments.
Solution Approach 2:
The invention changes the parameter used for identification from monoisotopic mass alone to the complete isotopic distribution pattern. By incorporating multiple parameters (intensities and masses of all observable isotopes) into the search algorithm, the method achieves higher precision without requiring higher resolution hardware.
2Measurement precision
If peak picking or centroiding is used to identify ions, then the process is simple, but accuracy is reduced when peaks are not baseline-resolved
Solution Approach 1:
The patent performs preliminary calibration of the mass spectrum to establish accurate mass-to-charge relationships and intensity scaling before conducting the search. This preliminary action ensures that the subsequent comparison between observed and theoretical isotopic patterns is performed on properly calibrated data, improving accuracy without adding complex real-time processing.
Solution Approach 2:
The method generates theoretical isotopic distribution patterns for candidate molecules and compares them against the observed spectral profile. By creating accurate theoretical copies of expected patterns and matching them to experimental data, the algorithm achieves high identification accuracy without requiring complex peak deconvolution procedures.
3Reliability
If only monoisotopic mass is used for molecular formula determination, then the search is simple and fast, but reliability is poor for larger molecules with overlapping isotopes
Solution Approach 1:
The patent segments the isotopic envelope into multiple observable isotopic peaks and analyzes each segment's mass and intensity independently. By breaking down the complete isotopic pattern into individual peak components, the method extracts more information from the spectrum while maintaining computational efficiency through systematic processing of each segment.
Solution Approach 2:
The search algorithm is designed to handle multiple types of molecules (small molecules, peptides, proteins) and various mass spectrometry conditions using a single unified approach. The method universally applies isotopic pattern matching across different molecular sizes and instrument types, achieving reliable results without requiring separate specialized procedures for each case.
Data Source
AI summary
A method for analyzing data from a mass spectrometer comprising acquiring raw profile mode data containing one or more ions and their isotopes in a mass spectral range; calculating theoretical isotope distributions for all ions of interest including native or labeled ions based on their molecular composition; convoluting the theoretical isotope distributions with target peak shape function specified during instrument calibration, actual peak shape functions, or approximated peak shape functions, to obtain theoretical isotope profiles for all ions; constructing a peak component matrix of relevant theoretical isotope profiles included as peak components; performing a weighted multiple linear regression between the profile mode data and the peak component matrix; and reporting regression coefficients as relative concentrations for each of the ions, or ranking these ions based on fitting statistics as search results. A mass spectrometer system (FIG. 1) operating in accordance with the method. Medium having computer code for operating the spectrometer.