MFAssignR

MFAssignR assigns molecular formulas to exact masses from ultrahigh resolution mass spectrometry (UHRMS) to enable nontargeted compositional analysis of complex environmental and biological mixtures.

Key Features:

• Post-Processing Pipeline: Provides a post-processing pipeline tailored for ultrahigh resolution mass spectra to prepare and process mass lists.
• Noise Estimation and Isotope Filtering: Implements mass defect analysis for noise estimation and identifies isotope pairs, including explicit filtering of polyisotopic masses of ^13C and ^34S.
• Mass Measurement Recalibration: Performs recalibration of mass measurements to improve mass accuracy.
• Molecular Formula Assignment: Converts exact mass measurements into molecular formulas using data-dependent assignment pathways that minimize a priori constraints.
• Flexibility for Custom Applications: Supports optional handling of formula ambiguities and multiple non-oxygen heteroatoms for applications such as isotopically labeled species, halogen-containing compounds, and tandem UHRMS analysis.
• Data Preparation Functions: Includes a suite of data preparation functions to condition input mass spectra for downstream processing.

Scientific Applications:

• Dissolved Organic Matter Characterization: Characterizes complex dissolved organic matter in environmental samples via nontargeted UHRMS formula assignment.
• Organic Aerosol Analysis: Enables molecular-level analysis of biomass burning–influenced organic aerosols, reducing assignment ambiguities compared with other molecular formula assignment methods.
• Isotopic and Halogenated Compound Studies: Supports analysis of isotopically labeled reactive species, halogen-containing compounds, and tandem UHRMS experiments that require multiple heteroatom consideration.

Methodology:

Applies mass defect analysis for noise estimation, filters polyisotopic masses (e.g., ^13C, ^34S), recalibrates mass measurements, assigns molecular formulas via data-dependent pathways, and provides data preparation functions.