posted on 2024-02-01, 20:03authored byHayden
A. Thurman, Gayani Wijegunawardena, Francis Berthias, David L. Williamson, Haifan Wu, Gabe Nagy, Ole N. Jensen, Alexandre A. Shvartsburg
Ion mobility spectrometry (IMS) coupled to mass spectrometry
(MS)
has become a versatile tool to fractionate complex mixtures, distinguish
structural isomers, and elucidate molecular geometries. Along with
the whole MS field, IMS/MS advances to ever larger species. A topical
proteomic problem is the discovery and characterization of d-amino acid-containing peptides (DAACPs) that are critical to neurotransmission
and toxicology. Both linear IMS and FAIMS previously disentangled d/l epimers with up to ∼30 residues. In the
first study using all three most powerful IMS methodologiestrapped
IMS, cyclic IMS, and FAIMSwe demonstrate baseline resolution
of the largest known d/l peptides (CHH from Homarus americanus with 72 residues) with a dynamic
range up to 100. This expands FAIMS analyses of isomeric modified
peptides, especially using hydrogen-rich buffers, to the ∼50–100
residue range of small proteins. The spectra for d and l are unprecedentedly strikingly similar except for a uniform
shift of the separation parameter, indicating the conserved epimer-specific
structural elements across multiple charge states and conformers.
As the interepimer resolution tracks the average for smaller DAACPs,
the IMS approaches could help search for yet larger DAACPs. The a
priori method to calibrate cyclic (including multipass) IMS developed
here may be broadly useful.