Identification of Hydroxyl Protons, Determination of Their Exchange Dynamics, and Characterization of Hydrogen Bonding in a Microcrystallin Protein

Agarwal, Vipin; Linser, Rasmus; Fink, Uwe; Faelber, Katja; Reif, Bernd

doi:10.1021/ja910167q

Cited by 39 publications

(45 citation statements)

References 73 publications

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“…This is different to what we have observed previously for a hydrogen bond involving a tyrosine hydroxyl and a carboxylic group. 25 In that case, the cross peak intensities of the donor carbons were approximately two-fold stronger in comparison to the intensities of the acceptor carbon. The downfield shifted 1 H imidazole resonance indicates that the proton is delocalized between the donor and the acceptor group, which is consistent with what has been found for model compounds by Limbach and co-worker.…”

Section: Discussionmentioning

confidence: 90%

“…In this experiment, a long 1 H, 13 C cross polarization mixing step is employed which allows us to transfer magnetization from the exchangeable imidazole proton to closely spaced carbon atoms which are not directly bonded. 25 The aromatic region of the spectrum is shown enlarged in Fig. 2A.…”

Section: Resultsmentioning

confidence: 99%

“…23,24 Due to the fact that magnetization transfer via dipolar interactions is very efficient, quickly exchanging side chain hydroxyl protons can be observed and assigned easily. 25 At the same time, scalar coupling based experiments yield reliable resonance assignments in the solid-state. [26][27][28][29] Fibril samples prepared from deuterated Ab peptides allow us to collect long range distance restraints which will help to refine the quarternary structure of the fibril.…”

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confidence: 97%

“…14 In all structural models, Ab peptides are arranged in a parallel fashion. An antiparallel arrangement is only observed for the Iowa mutant Ab-D23N, 15 and for truncated forms of the peptide such as Ab [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] . 16 The fibril structure is stabilized in particular by hydrogen bonding interactions.…”

mentioning

confidence: 99%

“…20 In the past, we have shown that for perdeuterated proteins it is possible to identify the donor and acceptor moieties of side chains involved in hydrogen bonds using a sufficiently long CP. 25 For Ab, hydrophobic interactions in the C-terminus yield an antiparallel arrangement of the protofilaments. 7 The other face of the protofilament is more hydrophilic, and is not involved in tertiary contacts in the models presented so far.…”

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confidence: 99%

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Hydrogen bonding involving side chain exchangeable groups stabilizes amyloid quarternary structure

Agarwal

Linser

Dasari

et al. 2013

Phys. Chem. Chem. Phys.

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The amyloid b-peptide (Ab) is the major structural component of amyloid fibrils in the plaques of brains of Alzheimer's disease patients. Numerous studies have addressed important aspects of secondary and tertiary structure of fibrils. In electron microscopic images, fibrils often bundle together. The mechanisms which drive the association of protofilaments into bundles of fibrils are not known. We show here that amino acid side chain exchangeable groups like e.g. histidines can provide useful restraints to determine the quarternary assembly of an amyloid fibril. Exchangeable protons are only observable if a side chain hydrogen bond is formed and the respective protons are protected from exchange. The method relies on deuteration of the Ab peptide. Exchangeable deuterons are substituted with protons, before fibril formation is initiated.Alzheimer's disease (AD) is a slowly progressive neurological disorder which is associated with memory loss, cognitive impairment and finally dementia and death. The amyloid b-peptide (Ab) is the major structural component of amyloid fibrils in the plaques of brains of Alzheimer's disease patients. Ab is a cleavage product resulting from Alzheimer Precursor Protein (APP) processing. 1 The g-secretase cut yields Ab fragments of different lengths of which Ab40 and Ab42 are most abundant. 2,3 In vitro, the Ab peptide aggregates over time into oligomers and fibrillar structures. 4 In the past, several Ab fibril structure models have been suggested. These are based on MAS solidstate NMR experiments, 5-11 and cryo-electron microscopic image reconstructions. 12 Even though there is some controversy concerning the conformational space that Ab fibrils can adopt, all published models, including the 2-fold 7,10 and 3-fold 9 symmetric Ab 1-40 fibril structure suggested by Tycko, and Bertini and co-workers, agree on the basic building block which involves a b-sheet (b1, residues 12-24), a turn, and a second b-sheet (b2, residues 28-40). Biophysical studies indicate a certain degree of conformational plasticity for the N-terminal b-sheet. 13,14 Whereas b2 is present in all the studies, b1 can be truncated or does not adopt a regular b-sheet structure. Depending on the preparation conditions, amide protons in the region of the peptide where the first b-strand is expected show differential H/D protection factors. 13 Similarly, a certain degree of conformational variability in the N-terminus is suggested using cryo-electron microscopy. 14 In all structural models, Ab peptides are arranged in a parallel fashion. An antiparallel arrangement is only observed for the Iowa mutant Ab-D23N, 15 and for truncated forms of the peptide such as Ab [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] . 16 The fibril structure is stabilized in particular by hydrogen bonding interactions. Therefore, observation of exchangeable and titratable groups is of particular interest to identify hydrogen bonding patterns. We and others could show in the past that high resolution proton spectra can be obtained for...

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Section: Discussionmentioning

confidence: 90%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 97%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Hydrogen bonding involving side chain exchangeable groups stabilizes amyloid quarternary structure

Agarwal

Linser

Dasari

et al. 2013

Phys. Chem. Chem. Phys.

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Mapping the Binding Interface of PET Tracer Molecules and Alzheimer Disease Aβ Fibrils by Using MAS Solid‐State NMR Spectroscopy

et al. 2020

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Positron emission tomography (PET) tracer molecules like thioflavin T specifically recognize amyloid deposition in brain tissue by selective binding to hydrophobic or aromatic surface grooves on the β‐sheet surface along the fibril axis. The molecular basis of this interaction is, however, not well understood. We have employed magic angle spinning (MAS) solid‐state NMR spectroscopy to characterize Aβ‐PET tracer complexes at atomic resolution. We established a titration protocol by using bovine serum albumin as a carrier to transfer hydrophobic small molecules to Aβ(1‐40) fibrillar aggregates. The same Aβ(1‐40) amyloid fibril sample was employed in subsequent titrations to minimize systematic errors that potentially arise from sample preparation. In the experiments, the small molecules 13C‐methylated Pittsburgh compound B (PiB) as well as a novel Aβ tracer based on a diarylbithiazole (DABTA) scaffold were employed. Classical 13C‐detected as well as proton‐detected spectra of protonated and perdeuterated samples with back‐substituted protons, respectively, were acquired and analyzed. After titration of the tracers, chemical‐shift perturbations were observed in the loop region involving residues Gly25‐Lys28 and Ile32‐Gly33, thus suggesting that the PET tracer molecules interact with the loop region connecting β‐sheets β1 and β2 in Aβ fibrils. We found that titration of the PiB derivatives suppressed fibril polymorphism and stabilized the amyloid fibril structure.

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Enantiospecific, Regioselective Cross‐Coupling Reactions of Secondary Allylic Boronic Esters

Chausset‐Boissarie

Ghozati

LaBine

et al. 2013

Chemistry A European J

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An original syn: The first enantioselective Suzuki–Miyaura cross‐coupling of chiral, enantioenriched secondary allylic boronic esters is described (see scheme; DME=dimethoxyethane, Bpin = pinacolboryl, dba = dibenzylideneacetone). Mechanistic studies show that the reactions proceed via γ‐selective transmetalation followed by reductive elimination. The reaction provides the first independent confirmation that the transmetalation of boronic esters proceeds via a syn pathway.

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Identification of Hydroxyl Protons, Determination of Their Exchange Dynamics, and Characterization of Hydrogen Bonding in a Microcrystallin Protein

Cited by 39 publications

References 73 publications

Hydrogen bonding involving side chain exchangeable groups stabilizes amyloid quarternary structure

Hydrogen bonding involving side chain exchangeable groups stabilizes amyloid quarternary structure

Mapping the Binding Interface of PET Tracer Molecules and Alzheimer Disease Aβ Fibrils by Using MAS Solid‐State NMR Spectroscopy

Enantiospecific, Regioselective Cross‐Coupling Reactions of Secondary Allylic Boronic Esters

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