ja5b10648_si_001.pdf (2.09 MB)
Supramolecular Enhancement of Protein Analysis via the Recognition of Phenylalanine with Cucurbit[7]uril
journal contribution
posted on 2015-12-09, 00:00 authored by Jong Wha Lee, Min Hyeon Shin, William Mobley, Adam R. Urbach, Hugh I. KimMass
spectrometry (MS)-based analysis using enzymatic digestion
is widely used for protein sequencing and characterization. The large
number of peptides generated from proteolysis, however, suppresses
the signal of peptides with low ionization efficiency, thus precluding
their observation and analysis. This study describes a technique for
improved analysis of peptic peptides by adding the synthetic receptor
cucurbit[7]uril (CB[7]), which binds selectively to peptides with
N-terminal aromatic residues. Capturing the N-terminal phenylalanine
(Phe) of peptides using CB[7] enhances the peptide abundances both
in electrospray ionization MS and in matrix-assisted laser desorption
ionization MS. Moreover, collision-induced dissociation (CID) of the
CB[7]·peptide complex ions generates b- and y-type fragment ions
with higher sequence coverage than those generated with uncomplexed
peptides. The signal enhancement mediated by CB[7] is attributed to
an increase in the peptide proton affinities upon CB[7] complexation.
The mechanistic details of the fragmentation process are discussed
on the basis of the structures of the complex ions obtained from ion
mobility (IM) measurements and molecular modeling. This study demonstrates
a novel and powerful approach to the enhancement of protein and peptide
analysis using a synthetic receptor, without the need for new instrumentation,
chemical modifications, or specialized sample preparation. The simplicity
and potential generality of this technique should provide a valuable
asset in the toolbox of routine protein and peptide analysis.