Amyloid Hydrogen Bonding Polymorphism Evaluated by ¹⁵N{¹⁷O}REAPDOR Solid-State NMR and Ultra-High Resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry

Abstract

A combined approach, using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and solid-state NMR (Nuclear Magnetic Resonance), shows a high degree of polymorphism exhibited by Aβ species in forming hydrogen-bonded networks. Two Alzheimer's Aβ peptides, Ac-Aβ(16-22)-NH2 and Aβ(11-25), selectively labeled with (17)O and (15)N at specific amino acid residues were investigated. The total amount of peptides labeled with (17)O as measured by FTICR-MS enabled the interpretation of dephasing observed in (15)N{(17)O}REAPDOR solid-state NMR experiments. Specifically, about one-third of the Aβ peptides were found to be involved in the formation of a specific >C═(17)O···H-(15)N hydrogen bond with their neighbor peptide molecules, and we hypothesize that the rest of the molecules undergo ± n off-registry shifts in their hydrogen bonding networks.

Narrowband Modulation Two-Dimensional Mass Spectrometry and Label-Free Relative Quantification of Histone Peptides

“…In standard broadband 2D MS, the cyclotron frequency range for precursor ions is determined by the lowest m /z ions to be fragmented in the 2D MS experiment, which leads to m / z ranges that are much wider than necessary, thereby limiting the resolving power of the precursor ions (corresponding to the isolation m / z window in standard MS/MS). In one-dimensional FT-ICR MS, heterodyne or “narrowband” techniques have been developed to enable ultrahigh resolution. − We present narrowband modulation 2D MS, which is conceptually different from one-dimensional narrowband MS and does not use heterodyne detection. Narrowband modulation 2D MS increases the precursor ion resolving power with the aim of differentiating the fragmentation patterns of overlapping isotopic distributions (e.g., peptides and proteins with and without disulfide bonds).…”

17O MAS NMR Correlation Spectroscopy at High Magnetic Fields

“…Both homonuclear and heteronuclear MAS recoupling experiments are routinely used to study the structure of peptides and proteins, − and provide accurate measurements of 13 C– 13 C, − 13 C– 15 N, , and 1 H– 13 C/ 15 N − distances. This class of experiments is also applicable, with suitably modified pulse sequences, to 13 C– 17 O, 15 N– 17 O and 1 H– 17 O distance measurements; for example, heteronuclear recoupling experiments have been reported, although only a few examples of two-dimensional heteronuclear correlation experiments are in the literature. − 15 N– 17 O rotational-echo adiabatic-passage double-resonance (REAPDOR) experiments were used to examine hydrogen bonding in amyloid fibrils, with the most complete results requiring an isolated spin-pair and a determination of the precise level of 17 O enrichment in the sample to precisely measure the 15 N– 17 O dipolar coupling. ,, Dipolar mediated heteronuclear correlation experiments between spin I = 1/2 and quadrupolar nuclei based on J-coupled experiments, such as rotary resonance recoupled (R 3 ) refocused insensitive nuclei enhanced by polarization transfer (R 3 -R-INEPT), have been shown to produce high-efficiency polarization transfer. , The addition of a multiple-quantum (MQ) or satellite transition (ST) filter to the dipolar meditated heteronuclear experiments was shown to increase the resolution available in these experiments . Finally, recent advances in 17 O spectroscopy including higher magnetic field experiments (>14.1 T), − application of population transfer techniques, − and dynamic nuclear polarization − ,− enhance the ability to perform these distance measurements.…”

“…Finally, recent advances in 17 O spectroscopy including higher magnetic field experiments (>14.1 T), − application of population transfer techniques, − and dynamic nuclear polarization − ,− enhance the ability to perform these distance measurements. Thus, successful 17 O studies of amino acids, polypeptides, pharmaceutical compounds, and amyloid fibrils have appeared in the literature using one or more of these strategies. − ,,− ,,− …”

17O NMR Spectroscopy: A Novel Probe for Characterizing Protein Structure and Folding

“…Further, they calculated the inter-strand C = 17 O ··· H- 15 N hydrogen bond distances and showed a typical O ··· N distance of 2.7 Å. Subsequently, Wei et al [ 52 ] investigated the polymorphisms exhibited by Aβ peptides, using the solid-state 15 N REAPDOR and advanced mass spectrometry techniques.…”