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Haidar Y, Konermann L. Effects of Hydrogen/Deuterium Exchange on Protein Stability in Solution and in the Gas Phase. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2023. [PMID: 37314114 DOI: 10.1021/jasms.3c00130] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Mass spectrometry (MS)-based techniques are widely used for probing protein structure and dynamics in solution. H/D exchange (HDX)-MS is one of the most common approaches in this context. HDX is often considered to be a "benign" labeling method, in that it does not perturb protein behavior in solution. However, several studies have reported that D2O pushes unfolding equilibria toward the native state. The origin, and even the existence of this protein stabilization remain controversial. Here we conducted thermal unfolding assays in solution to confirm that deuterated proteins in D2O are more stable, with 2-4 K higher melting temperatures than unlabeled proteins in H2O. Previous studies tentatively attributed this phenomenon to strengthened H-bonds after deuteration, an effect that may arise from the lower zero-point vibrational energy of the deuterated species. Specifically, it was proposed that strengthened water-water bonds (W···W) in D2O lower the solubility of nonpolar side chains. The current work takes a broader view by noting that protein stability in solution also depends on water-protein (W···P) and protein-protein (P···P) H-bonds. To help unravel these contributions, we performed collision-induced unfolding (CIU) experiments on gaseous proteins generated by native electrospray ionization. CIU profiles of deuterated and unlabeled proteins were indistinguishable, implying that P···P contacts are insensitive to deuteration. Thus, protein stabilization in D2O is attributable to solvent effects, rather than alterations of intraprotein H-bonds. Strengthening of W···W contacts represents one possible explanation, but the stabilizing effect of D2O can also originate from weakened W···P bonds. Future work will be required to elucidate which of these two scenarios is correct, or if both contribute to protein stabilization in D2O. In any case, the often-repeated adage that "D-bonds are more stable than H-bonds" does not apply to intramolecular contacts in native proteins.
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Affiliation(s)
- Yousef Haidar
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
| | - Lars Konermann
- Department of Chemistry, The University of Western Ontario, London, Ontario N6A 5B7, Canada
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Raefsky SM, Furman R, Milne G, Pollock E, Axelsen P, Mattson MP, Shchepinov MS. Deuterated polyunsaturated fatty acids reduce brain lipid peroxidation and hippocampal amyloid β-peptide levels, without discernable behavioral effects in an APP/PS1 mutant transgenic mouse model of Alzheimer's disease. Neurobiol Aging 2018; 66:165-176. [PMID: 29579687 PMCID: PMC5924637 DOI: 10.1016/j.neurobiolaging.2018.02.024] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2017] [Revised: 02/23/2018] [Accepted: 02/24/2018] [Indexed: 01/14/2023]
Abstract
Alzheimer's disease (AD) involves progressive deposition of amyloid β-peptide (Aβ), synapse loss, and neuronal death, which occur in brain regions critical for learning and memory. Considerable evidence suggests that lipid peroxidation contributes to synaptic dysfunction and neuronal degeneration, both upstream and downstream of Aβ pathology. Recent findings suggest that lipid peroxidation can be inhibited by replacement of polyunsaturated fatty acids (PUFA) with isotope-reinforced (deuterated) PUFA (D-PUFA), and that D-PUFA can protect neurons in experimental models of Parkinson's disease. Here, we determined whether dietary D-PUFA would ameliorate Aβ pathology and/or cognitive deficits in a mouse model of AD (amyloid precursor protein/presenilin 1 double mutant transgenic mice). The D-PUFA diet did not ameliorate spatial learning and memory deficits in the AD mice. Compared to mice fed an hydrogenated-PUFA control diet, those fed D-PUFA for 5 months exhibited high levels of incorporation of deuterium into arachidonic acid and docosahexaenoic acid, and reduced concentrations of lipid peroxidation products (F2 isoprostanes and neuroprostanes), in the brain tissues. Concentrations of Aβ40 and Aβ38 in the hippocampus were significantly lower, with a trend to reduced concentrations of Aβ42, in mice fed D-PUFA compared to those fed hydrogenated-PUFA. We conclude that a D-PUFA diet reduces the brain tissue concentrations of both arachidonic acid and docosahexaenoic acid oxidation products, as well as the concentration of Aβs.
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Affiliation(s)
- Sophia M Raefsky
- Laboratory of Neurosciences, National Institute on Aging, Baltimore, MD
| | - Ran Furman
- Departments of Pharmacology, Biochemistry and Biophysics, and Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA
| | - Ginger Milne
- Eicosanoid Core Laboratory, Vanderbilt University Medical Center, Nashville, TN
| | - Erik Pollock
- Stable Isotope Laboratory, University of Arkansas, Fayetteville, AR
| | - Paul Axelsen
- Departments of Pharmacology, Biochemistry and Biophysics, and Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA
| | - Mark P Mattson
- Laboratory of Neurosciences, National Institute on Aging, Baltimore, MD; Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD.
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Liu L, Siuda I, Richards MR, Renaud J, Kitova EN, Mayer PM, Tieleman DP, Lowary TL, Klassen JS. Structure and Stability of Carbohydrate-Lipid Interactions. Methylmannose Polysaccharide-Fatty Acid Complexes. Chembiochem 2016; 17:1571-8. [PMID: 27253157 DOI: 10.1002/cbic.201600123] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Indexed: 11/07/2022]
Abstract
We report a detailed study of the structure and stability of carbohydrate-lipid interactions. Complexes of a methylmannose polysaccharide (MMP) derivative and fatty acids (FAs) served as model systems. The dependence of solution affinities and gas-phase dissociation activation energies (Ea ) on FA length indicates a dominant role of carbohydrate-lipid interactions in stabilizing (MMP+FA) complexes. Solution (1) H NMR results reveal weak interactions between MMP methyl groups and FA acyl chain; MD simulations suggest the complexes are disordered. The contribution of FA methylene groups to the Ea is similar to that of heats of transfer of n-alkanes from the gas phase to polar solvents, thus suggesting that MMP binds lipids through dipole-induced dipole interactions. The MD results point to hydrophobic interactions and H-bonds with the FA carboxyl group. Comparison of collision cross sections of deprotonated (MMP+FA) ions with MD structures suggests that the gaseous complexes are disordered.
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Affiliation(s)
- Lan Liu
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada
| | - Iwona Siuda
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, Alberta, T2N 1N4, Canada
| | - Michele R Richards
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada
| | - Justin Renaud
- Chemistry Department, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada
| | - Elena N Kitova
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada
| | - Paul M Mayer
- Chemistry Department, University of Ottawa, Ottawa, Ontario, K1N 6N5, Canada
| | - D Peter Tieleman
- Centre for Molecular Simulation, Department of Biological Sciences, University of Calgary, Calgary, Alberta, T2N 1N4, Canada
| | - Todd L Lowary
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada
| | - John S Klassen
- Alberta Glycomics Centre, Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada.
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Zekavat B, Miladi M, Al-Fdeilat AH, Somogyi A, Solouki T. Evidence for sequence scrambling and divergent H/D exchange reactions of doubly-charged isobaric b-type fragment ions. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2014; 25:226-236. [PMID: 24346960 DOI: 10.1007/s13361-013-0768-9] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Revised: 10/07/2013] [Accepted: 10/08/2013] [Indexed: 06/03/2023]
Abstract
To date, only a limited number of reports are available on structural variants of multiply-charged b-fragment ions. We report on observed bimodal gas-phase hydrogen/deuterium exchange (HDX) reaction kinetics and patterns for substance P b10(2+) that point to presence of isomeric structures. We also compare HDX reactions, post-ion mobility/collision-induced dissociation (post-IM/CID), and sustained off-resonance irradiation-collision induced dissociation (SORI-CID) of substance P b10(2+) and a cyclic peptide with an identical amino acid (AA) sequence order to substance P b10. The observed HDX patterns and reaction kinetics and SORI-CID pattern for the doubly charged head-to-tail cyclized peptide were different from either of the presumed isomers of substance P b10(2+), suggesting that b10(2+) may not exist exclusively as a head-to-tail cyclized structure. Ultra-high mass measurement accuracy was used to assign identities of the observed SORI-CID fragment ions of substance P b10(2+); over 30% of the observed SORI-CID fragment ions from substance P b10(2+) had rearranged (scrambled) AA sequences. Moreover, post-IM/CID experiments revealed the presence of two conformer types for substance P b10(2+), whereas only one conformer type was observed for the head-to-tail cyclized peptide. We also show that AA sequence scrambling from CID of doubly-charged b-fragment ions is not unique to substance P b10(2+).
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Affiliation(s)
- Behrooz Zekavat
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX, 76798, USA
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Affiliation(s)
- Katarzyna Swiderek
- Institute of Applied Radiation Chemistry, Faculty of Chemistry, Lodz University of Technology , Zeromskiego 116, 90-924 Lodz, Poland
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