Organization of nucleobase‐functionalized β‐peptides investigated by soft electrospray ionization mass spectrometry

Abstract

The development and validation of analytical methods is a key to succeed in investigating noncovalent interactions between biomolecules or between small molecules and biomolecules. Electrospray ionization mass spectrometry (ESI-MS) was applied with a Fourier transform ion cyclotron resonance mass spectrometer (FTICR-MS) as well as a quadrupole/time-of-flight tandem mass spectrometer (QqToF-MS) for a systematic investigation of noncovalent complexes based on nucleobase pairing in an artificial and noncharged backbone topology. Synthetical beta-peptide helices covalently modified with nucleobases were organized by recognition of a sequence of four nucleobases. Specific duplexes of beta-peptide helices were obtained on the basis of hydrogen bonding base pair complementarity. Oligomer interactions were detected with defined stoichiometry and sensitivity for the respective duplex stability. FTICR-MS and QqToF-MS were used equally well to indicate double strand stabilities in agreement with the dissociation data determined by UV spectroscopy. Furthermore, the dissociation energies of gas phase ions of the noncovalent complexes were analyzed with collision induced dissociation (CID)-MS/MS and infrared multiphoton dissociation (IRMPD)-MS/MS. The CID conditions turned out to be too harsh for a differentiation of the duplex stabilities, whereas IRMPD might be developed as a technique to detect even small interaction energy differences.

The Role of Initial Oligomers in Amyloid Fibril Formation by Human Stefin B

“…Previously, ESI MS has been used for evaluation of oligomers and prefibrillar aggregates of various peptides and proteins [51], such as, for example, amyloid-β peptide fragment 10–30 [52], nucleobase-functionalized beta-peptides [53], insulin [54], transthyretins [36,55,56], human beta-2-microglobulin [57], native hemocyanins [58,59], flavoproteins [60], bifunctional kinase/phosphatase [58]. We have previously used ESI MS for the determination of the complex between oligomers, tetramers, and dimers of stefin B and monomers of amyloid-β peptide [42].…”