Unleashing radical sites in non‐covalent complexes: The case of the protonated <i>S</i>‐nitrosocysteine/18‐crown‐6 complex

Osburn, Sandra; O’Hair, Richard A. J.

doi:10.1002/rcm.6745

Cited by 5 publications

(5 citation statements)

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“…Each of the amine thiols (2-amino-1-ethanethiol; 3-amino-1-propanethiol, and 4-amino-1-butanethiol) were separately nitrosylated in 1:1 methanol–water solution with tert -butyl nitrite as described previously. − The resultant reaction solutions containing the S -nitrosoamines were diluted to a 0.5 mM 1:1 methanol–water solution and directly infused into the electrospray ionization (ESI) source of a modified hybrid LTQ FT-ICR mass spectrometer at a flow rate of 5.0 μL min –1 . In the positive ion mode, the S -nitrosoammonium ions, H 3 N + (CH 2 ) n SNO were formed and the source conditions were tuned to optimize their signal.…”

Section: Experimental and Theoretical Methodsmentioning

confidence: 99%

“…For example, intramolecular hydrogen bonding of the side chains of serine and threonine constrains free radical reaction dynamics at these residues . As part of a series of studies on the structure and reactivity of thiyl distonic ions − derived from cysteine, its derivatives, and peptides, − we discovered that the thiyl radical of cysteine, 1a (Scheme ), is more reactive with respect to atom abstraction reactions than homocysteine, 1b . We speculated that this may be due to differences in the strength of intramolecular hydrogen bonding …”

Section: Introductionmentioning

confidence: 99%

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Role of Hydrogen Bonding on the Reactivity of Thiyl Radicals: A Mass Spectrometric and Computational Study Using the Distonic Radical Ion Approach

et al. 2016

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Experimental and computational quantum chemistry investigations of the gas-phase ion-molecule reactions between the distonic ions HN(CH)S (n = 2-4) and the reagents dimethyl disulfide, allyl bromide, and allyl iodide demonstrate that intramolecular hydrogen bonding can modulate the reactivity of thiyl radicals. Thus, the 3-ammonium-1-propanethiyl radical (n = 3) exhibits the lowest reactivity of these distonic ions toward all substrates. Theoretical calculations on this distonic ion highlight that its most stable conformation involves a six-membered ring configuration, and that it has the strongest intramolecular hydrogen bond. In addition, the calculations indicate that the barrier heights for radical abstraction by this hydrogen-bond-stabilized 3-ammonium-1-propanethiyl radical are the highest among the systems examined, consistent with the experimental observations.

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Section: Experimental and Theoretical Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Role of Hydrogen Bonding on the Reactivity of Thiyl Radicals: A Mass Spectrometric and Computational Study Using the Distonic Radical Ion Approach

et al. 2016

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“…Recently, we have shown that all three requirements can indeed be met [19]. As a "proof of concept", the non-covalent complex between protonated S-nitrosocysteine and 18-crown-6 (18-C-6) was formed by ESI and shown to fragment via NO loss to produce the radical cation non-covalent complex (Eq.…”

Section: Introductionmentioning

confidence: 98%

Formation of sugar radical cations from collision-induced dissociation of non-covalent complexes with S-nitroso thiyl radical precursors

Osburn

Williams

O’Hair

2015

International Journal of Mass Spectrometry

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A B S T R A C TA 'bio-inspired' method has been developed for generating sugar radical cations by multistage mass spectrometry (MS 4 ) experiments involving collision-induced dissociation (CID) of protonated non-covalent complexes between a sugar and an S-nitrosylated thiol amine, [H 3 NXSNO + M] + (where X = (CH 2 ) 2 , (CH 2 ) 3 , (CH 2 ) 4 , CH(CO 2 H)CH 2 and CH(CO 2 CH 3 )CH 2 ). In the first stage of CID (MS 2 ), homolysis of the S-NO bond unleashes a thiyl radical to give the non-covalent radical cation, [H 3 NXS + M] + . It was found that complexes containing S-nitroso cysteamine (X = (CH 2 ) 2 ) produced the most abundant radical cations for monosaccharides, while for larger sugars, the most abundant radical cations were generated from the S-nitroso derivatives of 3-amino-1-propanethiol (X = (CH 2 ) 3 ) and 4-amino-1-butanethiol (X = (CH 2 ) 4 ). CID (MS 3 ) of the radical cation complex resulted in the dissociation of the non-covalent complex to generate the sugar radical cation [M ] + . Deuterium labelling studies reveal that this process involves abstraction of a hydrogen atom from a C-H bond of the sugar coupled with proton transfer to the sugar. The fragmentation reactions of the radical cation, [M ] + , were studied by another stage of CID (MS 4 ). In this work, the scope of the method was established, particularly for the S-NO bond homolysis (MS 2 ) and [M ] + formation (MS 3 ) steps. Twenty-six different sugars were examined and radical cations could be generated for polysaccharides of varying lengths, as well as for the methyl pyranosides of a range of monosaccharides.

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“…Inspired by Nature"s use of enzyme radical chemistry to biocatalytically transform carbohydrate-based substrates [25][26][27][28][29][30][31], we have previously described an approach that utilizes a charged non-covalent complex between a sugar and a radical to generate a charged sugar radical [32,33]. The method (Scheme 1) involves: (i) transfer to the gas phase of a charged non-covalent complex containing a sugar and a radical precursor (an Snitrosoamine); (ii) formation of the radical cation non-covalent complex by unleashing the radical site from the precursor in preference to dissociation of the non-covalent complex (step (a) of Scheme 1); and (iii) transfer of both the radical and charge sites to the sugar upon dissociation of the radical cation non-covalent complex (step (b) of Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

Gas-Phase Intercluster Thiyl-Radical Induced C–H Bond Homolysis Selectively Forms Sugar C2-Radical Cations of Methyl D-Glucopyranoside: Isotopic Labeling Studies and Cleavage Reactions

Osburn

Speciale

Williams

et al. 2017

J. Am. Soc. Mass Spectrom.

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A suite of isotopologues of methyl D-glucopyranosides is used in conjunction with multistage mass spectrometry experiments to determine the radical site and cleavage reactions of sugar radical cations formed via a recently developed 'bio-inspired' method. In the first stage of CID (MS), collision-induced dissociation (CID) of a protonated noncovalent complex between the sugar and S-nitrosocysteamine, [HNCHCHSNO + M], unleashes a thiyl radical via bond homolysis to give the noncovalent radical cation, [HNCHCHS + M]. CID (MS) of this radical cation complex results in dissociation of the noncovalent complex to generate the sugar radical cation. Replacement of all exchangeable OH and NH protons with deuterons reveals that the sugar radical cation is formed in a process involving abstraction of a hydrogen atom from a C-H bond of the sugar coupled with proton transfer to the sugar, to form [M - H + D]. Investigation of this process using individual C-D labeled sugars reveals that the main site of H/D abstraction is the C2 position, since only the C2-deuterium labeled sugar yields a dominant [M - D + H] product ion. The fragmentation reactions of the distonic sugar radical cation, [M - H+ H], were studied by another stage of CID (MS). C-labeling studies revealed that a series of three related fragment ions each contain the C1-C3 atoms; these arise from cross-ring cleavage reactions of the sugar. Graphical Abstract ᅟ.

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Unleashing radical sites in non‐covalent complexes: The case of the protonated S‐nitrosocysteine/18‐crown‐6 complex

Cited by 5 publications

References 24 publications

Role of Hydrogen Bonding on the Reactivity of Thiyl Radicals: A Mass Spectrometric and Computational Study Using the Distonic Radical Ion Approach

Role of Hydrogen Bonding on the Reactivity of Thiyl Radicals: A Mass Spectrometric and Computational Study Using the Distonic Radical Ion Approach

Formation of sugar radical cations from collision-induced dissociation of non-covalent complexes with S-nitroso thiyl radical precursors

Gas-Phase Intercluster Thiyl-Radical Induced C–H Bond Homolysis Selectively Forms Sugar C2-Radical Cations of Methyl D-Glucopyranoside: Isotopic Labeling Studies and Cleavage Reactions

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