Determining the Binding Sites of β-Cyclodextrin and Peptides by Electron-Capture Dissociation High Resolution Tandem Mass Spectrometry

Abstract

Cyclodextrins (CDs) are a group of cyclic oligosaccharides, which readily form inclusion complexes with hydrophobic compounds to increase bioavailability, thus making CDs ideal drug excipients. Recent studies have also shown that CDs exhibit a wide range of protective effects, preventing proteins from aggregation, degradation, and folding. These effects strongly depend on the binding sites on the protein surface. CDs only exhibit weak interactions with amino acids, however; conventional analytical techniques therefore usually fail to reveal the exact location of the binding sites. Moreover, some studies even suggest that CD inclusion complexes are merely electrostatic adducts. Here, electron capture dissociation (ECD) was applied in this proof-of-concept study to examine the exact nature of the CD/peptide complexes, and CD binding sites were unambiguously located for the first time via Fourier-transform ion cyclotron resonance (FTICR) tandem mass spectrometry.

Noncovalent Complexes of Cyclodextrin with Small Organic Molecules: Applications and Insights into Host–Guest Interactions in the Gas Phase and Condensed Phase

“…The two opposite trends were noted during electron capture dissociation (ECD)-MS experiments conducted on permethylated or intact β-CD/peptide noncovalent complexes [ 53 , 162 ]. ECD-MS is a unique fragmentation technique that conserves labile noncovalent bonds while facilitating extensive peptide backbone fragmentation.…”

Distinguishing enantiomeric amino acids with chiral cyclodextrin adducts and structures for lossless ion manipulations

“…1). In this regard, numerous studies have probed and modeled the formation of host-guest inclusion complexes for enantiomeric separations [36][37][38][39][40][41][42][43][44], and, as already noted, the use of cyclodextrins as both chiral stationary phase supports and mobile phase additives [5,[7][8][9][10][11][12][13][14][15][16][17][18].…”

Electron-based fragmentation methods in mass spectrometry: An overview

“…The ECD technique allows electrons to be captured by positive ions to form radical cations with subsequent specific cleavages for peptide N‐Cα bonds. Due to this unique fragmentation feature, ECD has opened up new opportunities for the study of proteins during the last decade; e.g., its application to top‐down sequencing (Kelleher, ), post‐translational modifications (PTMs) (Sweet & Cooper, ), protein‐protein complexes (Zhang et al, ), host‐guest interactions (Qi et al, ; Qi & Volmer, ), and isomer differentiation of peptides (Cooper et al, ; Cournoyer et al, ). Additionally, by manipulating the ions’ energy, several new electron‐based fragmentation techniques have been developed, which greatly broaden its application range; e.g., electron transfer dissociation (ETD) for application in low‐cost ion trap mass analyzers (Syka et al, 2004), hot‐ECD for producing abundant secondary fragmentation (Williams et al, ), electron‐induced dissociation (EID) for singly‐charged ions (Lioe & O'Hair, ), negative‐ion electron capture dissociation (niECD) (Yoo et al, ) and electron detachment dissociation (EDD) for deprotonated ions (Budnik et al, ).…”