Solid-State 15N and 17O NMR Studies of S-Nitrosothiols - The Journal

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Solid-State N and O NMR Studies of S-Nitrosothiols Yin Gao, Yizhe Dai, and Gang Wu J. Phys. Chem. B, Just Accepted Manuscript • DOI: 10.1021/acs.jpcb.7b05685 • Publication Date (Web): 10 Jul 2017 Downloaded from http://pubs.acs.org on July 15, 2017

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The Journal of Physical Chemistry

Solid-State 15N and 17O NMR Studies of S-Nitrosothiols

Yin Gao,1,2 Yizhe Dai,1 and Gang Wu1*

1

Department of Chemistry, Queen’s University, 90 Bader Lane,

Kingston, Ontario, Canada K7L 3N6; 2The College of Life Sciences, Jilin University, 2699 Qianjin Street, Changchun, China 130012.

Running title: Solid-State 17O and 15N NMR of RSNO

*Corresponding author: [email protected]

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ACS Paragon Plus Environment


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Abstract We report a solid-state 15N and 17O NMR study of two representative S-nitrosothiols (RSNO): S-nitroso N-acetylpenicillamine (SNAP) and S-nitrosoglutathione (GSNO). The 15

N and

17

O NMR tensors are experimentally determined for the first time for this

important class of nitric oxide (NO)-related compounds. The observed NMR characteristics for RSNO include large 15N and 17O chemical shift anisotropies and large 17

O quadrupole coupling constants. Quantum chemical calculations are also performed

for the

15

N and

17

O NMR tensors in two simple RSNO models: t-BuSNO and MeSNO.

On the basis of computational results, we have identified the molecular orbitals that are responsible for the observed large chemical shift anisotropies in RSNO compounds.

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1. Introduction S-nitrosothiols (R-S-N=O or RSNO) are a class of organic molecules that play important roles in nitric oxide (NO) chemistry, potential therapeutic applications, and protein post-translational modification.1-10 Recently, the reactivity of RSNOs towards H2S under physiological conditions has attracted considerable attention11-15 and also generated controversies.16-21 This new reaction pathway adds further complication for possible “cross talks” between the two major gaseous signaling molecules, NO and H2S. Because RSNOs are generally unstable, only a limited number of X-ray structural22-26 and 15

N (I = 1/2) NMR spectroscopic studies23,27-29 have been reported in the literature. In

fact, all previous NMR studies of other NO-related compounds utilize 15N as a common NMR probe nucleus.30-32 Recently, we demonstrated the use

17

O (I = 5/2) as a

complementary NMR probe to study NO-related compounds.33-36 One of the advantages of

17

O NMR is that the fast quadrupolar

17

O relaxation in solution allows one to collect

data very rapidly so that some transient reaction intermediates can be potentially captured. For example, we used

17

O NMR to help identify molecular structures of the

elusive red-violet and blue intermediates in the Gmelin reaction between nitroprusside and sulfides in aqueous solution.34 We have also reported a complete multinuclear (1H, 13

C,

15

N,

17

O) NMR characterization of the so-called “red product” from the reaction

between nitroprusside and 2-mercaptosuccinic acid.35 This “red product” can be generally formulated as [FeII(CN)5N(O)SR]3– where a RSNO ligand is coordinated to the Fe(II) center via the nitrogen atom. To broaden our knowledge about NMR properties in RSNO compounds, we report herein a solid-state 15N and 17O NMR study of two representative RSNOs: S-nitroso N-acetylpenicillamine (SNAP) and S-nitrosoglutathione (GSNO); see

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Scheme 1. The primary goal of the study is to experimentally measure the

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15

N and

17

O

NMR tensors in RSNO compounds, since such fundamental information has not been reported in the literature.37-39 Several years ago, solid-state 15N and 17O NMR tensor data were reported for a class of RSNO-related compounds, C-nitrosoarenes (Ar-N=O).40-42 Because R-S-N=O exhibits some bonding properties similar to those seen in Ar-N=O, it 15

would be of interest to compare the

N and

compounds. In addition, characterizing

15

17

O NMR tensors in these two classes of

N and

17

O NMR tensors in RSNO will help

build a reasonable size of database for a variety of reaction intermediates encountered in the NO chemistry. In this study, we also perform quantum chemical calculations for two simple RSNO models, t-BuSNO and MeSNO (Scheme 1), to further understand the and

17

15

N

O magnetic shielding tensors in the S-N=O functional group. Common features

among the NMR tensor properties between RSNO and Ar-N=O compounds will be examined.

O

O

N

N

S

S

C

O

O

O

H2C

H3C

N H

HO O

N H

NH2

SNAP

O

H N

OH

OH O

GSNO O

O

N

N

S

S

C

O N S

CH3

CH3

anti t-BuSNO

syn MeSNO

Scheme 1. Molecular structures of S-nitroso N-acetylpenicillamine (SNAP), Snitrosoglutathione (GSNO), t-BuSNO, and MeSNO.

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2. Experimental section 2.1 Synthesis All chemicals were purchased from Sigma–Aldrich unless stated otherwise: NAcetyl-penicillamine, glutathione, sodium sulfide (Na2S), triphenylphosphine, Na15NO2, (98 % 15N, Cambridge Isotope Laboratories, Inc.), 17O-labeled water (H217O, 41.1 % 17O, CortecNet). Preparation of solution NMR samples was carried out under anaerobic conditions. [15N]-SNAP was prepared by following the literature method with minor modifications.22 N-Acetyl-penicillamine (191.2 mg) was mixed with 1.1 molar equivalents of Na15NO2 in 0.58 mL of 0.55 M HCl H2O. The reaction mixture was kept on ice for 40 min followed by addition of concentrated H2SO4, which induced precipitate formation. The solids were then collected by filtration, washed with ice-cold water (5 × 2 mL), dried under vacuum to give deep green solids (120 mg, 63%). The 15N enrichment in the product was 98%. 15N NMR (40.6 MHz, Acetone-d6): δ = 835 ppm (ref. to liquid NH3). [17O]-SNAP was prepared in the same way as for [15N]-SNAP, except that 0.5 mL 0.55 M HCl (in H217O, 41.1% 17O) was used. The 17O enrichment in the final product was 30 %. 17O NMR (54.3 MHz, Acetone-d6): δ = 1314 ppm (ref. to liquid H2O). [15N]-GSNO was synthesized by following the literature method with minor modifications.43 Glutathione (150 mg) was mixed with 1.1 molar equivalents of Na15NO2 in 1.0 mL of 0.48 M HCl(aq). The reaction mixture was kept on ice for 40 min. After addition of 3 mL ice-cold acetone, the solution was stirred for another 10 min. The solids formed were collected by centrifugation and dried under Ar to give pink solids (69 mg, 46 %). 15N NMR (40.6 MHz, D2O): δ = 768 ppm (ref. to liquid NH3). [17O]-GSNO was

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prepared in the same as for [15N]-GSNO, except that 0.58 mL 0.55 M HCl (in H217O, 41.1 %

17

O) was used. The

17

O enrichment in the product was 30 %.

17

O NMR (54.3

MHz, D2O): δ = 1211 ppm (ref. to liquid H2O).

2.2 Solid-state NMR Solid-state 15N NMR spectra were recorded on a Bruker Avance-600 spectrometer at 14.1 T. A Bruker 4-mm HX MAS probe was used. Caution! RSNO compounds are generally not stable and their thermal decomposition leads to production of gases (NO and NO2). Sample heating from fast MAS can produce enough gases that may potentially pop the rotor cap during sample spinning. Solid-state

17

O NMR experiments were

performed on both Avance-600 and Avance-II 900 NMR spectrometers. A Hahn-echo sequence was used for both static and MAS experiments to eliminate the acoustic ringing from the probe. Effective 90º pulses of 1.7 and 1.0 µs were used for the transition (CT) experiments at 14.1 and 21.1 T, respectively. The

17

17

O central

O static spectra at

14.1 T were recorded using a 4-mm Bruker MAS probe without sample spinning. To acquire static spectra at 21.1 T, a homebuilt 5-mm H/X solenoid probe was used with solid samples packed into a 5-mm Teflon tube to reduce the background signal. High power 1H decoupling (70 kHz) was applied in all static experiments. A liquid H2O sample was used for both RF power calibration and 17O chemical shift referencing (δ = 0 ppm). All spectral simulations were performed with DMfit.44

2.3 Quantum chemical calculations

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Calculations of

15

N and

17

O NMR (EFG and CS) tensors were performed using the

Amsterdam density functional (ADF) software package.45 The Vosko-Wilk-Nusair (VWN) exchange-correlation functional46 was used for the local density approximation (LDA) while the Perdew Burke Ernzerhof (PBE) exchange-correlation functional47 was applied for the generalized gradient approximation (GGA). The standard Slater-typeorbital (STO) basis set with triple-zeta quality plus polarization functions (TZ2P) was used for all the atoms. The spin orbital relativistic effect was incorporated in some calculations via either the Pauli-type Hamiltonian48 or the zero-order regular approximation (ZORA).49-52 All calculations were carried out at the Centre for Advanced Computing at Queen’s University on a Dell PowerEdge R410 Server with 2 sockets with a 6-core Intel® Xeon® processor (Intel x5675) running at 3.1 GHz.

3. Results and discussion Figure 1 shows the

15

N MAS NMR spectra recorded for [15N]-SNAP and [15N]-

GSNO at 14.1 T. The values of δiso(15N) for these two RSNOs are 840 and 765 ppm, which are comparable to those found for other RSNO compounds.28 These are also similar to those found in C-nitrosoarenes.40,41 We recently found that, upon Ncoordination to Fe(II), δiso(15N) of RSNO can change nearly 200 ppm.35 As seen from Figure 1, both RSNO compounds also exhibit very large 15N chemical shift anisotropies (span Ω = δ11 − δ33 = 1138 and 1170 ppm for [15N]-SNAP and [15N]-GSNO, respectively). These span values are also similar to those in C-nitrosoarenes.40,41 Another type of related compounds that have a considerable amount of

15

N solid-state NMR

literature are metal nitrosyls.32 While the 15N chemical shift anisotropies found in RSNOs

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are larger than those seen in linear nitrosyls, they are considerably smaller than the largest values found in bent nitrosyls (e.g., some Co(NO)(LL′) complexes exhibit Ω values on the order of 2000 ppm).32 Interestingly, the δiso(15N) values for RSNOs are also similar to those reported for a Fe(II)-bound nitroxyl (H-N=O). While free HNO has not yet been characterized by NMR, quantum chemical calculations suggest that δiso(15N) for HNO is about 1300 ppm. It is interesting to note in Figure 1 that the

15

N NMR signals for [15N]-SNAP are

quite broad. This broadness cannot be attributed to insufficient proton decoupling as the carbon atom attached to the S-N=O group in SNAP is quaternary whereas the corresponding carbon atom in GSNO is secondary. Both compounds are good crystalline materials, ruling out the possibility that any structural heterogeneity may contribute to the observed line broadening. The most likely reason for the broad signals observed in SNAP is the presence of both syn and anti conformers as static disorder. There are precedents in the literature where both syn and anti conformers of RSNO are simultaneously present in the crystal lattice.25,26 In addition, rapid interconversion between syn and anti conformations is also common for RSNO in solution.23 However, since the two conformers display similar δiso(15N) values, we assumed in our spectral analysis that a single set of principal tensor components are present for each of the

15

N and

17

O NMR

tensors for SNAP. Figure 2 shows the static

17

O NMR spectra of [17O]-SNAP and [17O]-GSNO. It is

well established that, to assess the interplay of magnetic shielding and second-order quadrupole interactions in static 17O NMR spectra, it is important to obtain static spectra at multiple magnetic fields.37 As seen in Figure 2, each static 17O NMR spectrum spans a

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range of over 3000 ppm. Interestingly, for a given compound, the total spectral breadth (if expressed on the ppm scale) does not seem to change between 14.1 and 21.1 T. As previously noted in the solid-state 17O NMR studies of C-nitrosoarenes42 and aldehydes,53 this apparent insensitivity of the line width to the applied magnetic field strength suggests that the second-order quadrupole interaction and chemical shift anisotropy are of the same magnitude in RNSOs. Ideally, one would wish to obtain 17O MAS NMR spectra as well for these compounds to aid spectral analysis. Unfortunately, because of the large magnitude of CQ(17O) in RSNO, very fast MAS (> 40 kHz) would be required at 21.1 T. Since RSNO compounds are not stable, their thermal decomposition leads to production of gases. In one instance, when a 4-mm rotor packed with GSNO was spun at 15 kHz over an extended period of time in our laboratory, the gases produced from GSNO thermal decomposition popped the rotor cap causing damage of the MAS stator. For this safety reason, we decided not to pursue very fast MAS (> 40 kHz) for these compounds at 21.1 T. Nonetheless, the static

17

O NMR spectra shown in Figure 2 were fitted using

the δiso(17O) values measured in solution and our previous knowledge about the relative orientation between the 17O chemical shift and quadrupole coupling tensors in analogous C-nitroso compounds.42 We further performed quantum chemical calculations of the 15N and 17O NMR tensors in two model RSNO compounds: t-BuSNO and MeSNO. There are two reasons for us to perform computations for these simplified model compounds rather than SNAP and GSNO themselves. First, while a low-quality crystal structure for SNAP was reported,22 no crystal structure of GSNO is available in the literature. Second, inspection of all crystal structures of RSNO compounds suggests that the S-N=O group in these compounds is not involved in any intermolecular interaction in the crystal lattice.

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For MeSNO, we carried out calculations for both syn and anti conformers. The calculations show that the syn and anti conformers of MeSNO indeed exhibit δiso(15N) values of 889 and 961 ppm, respectively. This is in agreement with that reported by Bartberger et al.24 As expected, the difference between the δiso(17O) values for syn and anti conformers is larger than that between the δiso(15N) values. Potentially, 17O NMR can be a better probe of the syn ↔ anti dynamic process in RSNO; to date, however, separate 17

O NMR signals for syn and anti conformers of RSNO have not been observed. Figure 3

shows that the general agreement between the experimental and computed

15

N and

17

O

chemical shift tensor components is reasonable. As noted previously,42 the discrepancy between experimental and computational results is largely due to overestimation of the paramagnetic shielding contribution (vide infra). The computational results once again confirmed the

17

O NMR tensor orientations used in the spectral simulations. All

experimental and computed 15N and 17O NMR tensor parameters are listed in Table 1 and the tensor orientations are depicted in Figure 4. For SNAP and GSNO, the values of CQ(17O) (ca. 12-14 MHz) are similar to those reported for C-nitroso compounds (ca. 15 MHz),42 but larger than those in carbonyl compounds (ca. 7-12 MHz).37 Another key difference between N=O and C=O compounds is that the

O quadrupole coupling tensor components χyy and χxx display

17

different orientations within the molecular frame of reference. In particular, as seen in Figure 4, χyy is along the N=O bond whereas in C=O compounds, χxx is along the C=O bond direction. As seen from Table 1, SNAP and GSNO exhibit very large

17

O chemical shift

anisotropies, which is similar to that reported for C-nitrosoarene compounds.42 Here it is

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also interesting to compare the common features in 17O NMR tensors observed for RSNO compounds with those recently reported for the N-O singly bonded compounds. In general, while both classes of compounds exhibit large CQ(17O) values, the signs of CQ(17O) are opposite (CQ(17O) > 0 in the N=O compounds but CQ(17O) < 0 in the N-O compounds). Another notable difference is that the N-O compounds have rather small 17

O chemical shift anisotropies (Ω = 100−250 ppm). To gain further insights into the origins of the large

15

N and

17

O chemical shift

anisotropies observed in RSNO, we performed a detailed analysis of the various contributions from individual molecular orbitals (MOs) to the

15

N and

17

O magnetic

shielding tensors. This type of MO-based analysis for magnetic shielding tensors has been well described in the literature.54,55 We chose anti-MeSNO as a representative model for this analysis. According to Ramsey’s theory of nuclear shielding,56 the total magnetic shielding tensor at a nucleus can be divided into diamagnetic and paramagnetic contributions:

σ = σ iid + σ iip

(1)

where the subscript ii indicates the individual principal components of the magnetic shielding tensor (i = x, y, z). Qualitatively, the diamagnetic shielding term in eq. 1 is dominated by the core electrons and consequently is essentially isotropic. On the other hand, the paramagnetic shielding contribution is responsible for the anisotropic nature of the shielding tensor. In general terms, the paramagnetic shielding term arises from a coupling between occupied and unoccupied MOs as a result of the applied magnetic field. The effectiveness of such a coupling between a particular pair of MOs to induce a paramagnetic shielding effect depends on several factors as will be discussed later. In the

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formulation implemented in the ADF software package, it is possible to further breakdown the total paramagnetic shielding σp into three different parts:45 σp = σp(gauge) + σp(occ-occ) + σp(occ-vir)

(2)

where σp(gauge), σp(occ-occ) and σp(occ-vir) describe paramagnetic shielding contributions from the gauge, coupling between occupied and occupied MOs, and coupling between occupied and virtual MOs, respectively. Several general trends have been well established from previous studies. First, σd is essentially isotropic (very little dependence on molecular orientation) and exhibits very little variation among closely related compounds. Second, σp(gauge) is generally very small, < 20 ppm. Third, σp(occocc) has slightly larger values/and variations than does σp(gauge), but generally does not exhibit any clear trend. Fourth, σp(occ-vir) is the predominant term that accounts for both the shielding anisotropy within each molecule and the large variations among different molecules. In Table 2, we list the most important contributions to the

15

N and

17

O

magnetic shielding tensors in anti-MeSNO. Indeed, both σd and σp(occ-occ)+σp(gauge) terms show rather small variations among the three tensor components. In the discussion that follows, we focus only on the σp(occ-vir) contributions. Furthermore, it is necessary to discuss σp(occ-vir) contributions for σ11 and σ22 directions, separately. We have identified 5 pairs of MOs that make the largest σp(occ-vir) contributions to both the 15N and 17O magnetic shielding tensors; see Table 2. Because the extent of magnetic coupling between two MOs depends inversely on the energy difference between them, the energy gaps are also provided in Table 2. To aid visualization of these important MOs, we display them in Figure 5 together with their relevant energies.

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As seen from Figure 5, the magnetic coupling between MO#20 (HOMO) and MO#21(LUMO) accounts for 89% of the paramagnetic shielding contribution in the σ11 direction of the 15N magnetic shielding tensor. In the molecular frame of reference, σ11 is roughly along the N=O bond as illustrated in Figure 4. The corresponding contribution from this pair of MOs for the

17

O magnetic shielding tensor is even higher, 92%. As

Jameson and Gutowsky showed,57 the degree of magnetic coupling between an occupied MO and a virtual/unoccupied MO depends critically on the extent of overlap between them after a 90° rotation of one of them about the direction of the magnetic field. For example, assume that the magnetic field is along the N=O bond (i.e., the σ11 component). Now the shape and orientation of MO#20 are such that, after a 90° rotation about the magnetic field, it will have a maximum overlap with MO#21. In other words, after a 90° rotation about the N=O bond, the “in-plane” MO#20 becomes “out-of-the-plane” thus overlapping significantly with the already “out-of-the-plane” MO#21. Combining this spatial relationship between MO#20 and MO#21 with the fact that the energy gap between MO#20 and MO#21 corresponds to the HOMO-LUMO gap (smallest among all possible pairs), it is understandable why this particular pair of MOs produces the largest paramagnetic contribution when the magnetic field is along the N=O bond direction. For the σ22 component, there is no single pair of MOs that dominates σp(occ-vir). As shown in Figure 5, for the 15N magnetic shielding tensor, there are three pairs of MOs (#17-#21, #15-#21, #13-#21) that account for 73% of σp(occ-vir). Similarly, for the σ22 component of the

17

O magnetic shielding tensor, 5 pairs of MOs (#20-#21, #18-#21, #17-#21, #15-

#21, #13-#21) contribute 81% of σp(occ-vir). It is interesting to note that the magnetic coupling between #18 and #21 makes a 6% contribution to the σ22 component of the 17O

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magnetic shielding tensor, but has no impact on the

15

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N magnetic shielding tensor.

Examination of the shape of MO#18 shown in Figure 5 reveals that within MO#18 electron density is concentrated on the O atom not the N atom of the N=O moiety.

4. Conclusions We have carried out solid-state NMR experiments to determine the

15

N and

17

O

NMR tensors in two representative S-nitrosothiols: SNAP and GSNO. Similar to a CN=O functional group examined previously, the S-N=O moiety exhibits very large quadrupolar coupling constants (ca. 12-14 MHz) as well as very large chemical shift anisotropies (15N: ∼1000 ppm and

17

15

N and

17

O

17

O

O: ∼3000 ppm). Quantum chemical

calculations suggest that these very large chemical shift anisotropies are largely due to the magnetic coupling between the HOMO and LUMO in RSNO. This work continues out effort to accumulate solid-state

17

O NMR data for important oxygen-containing

functional groups, especially in the field of NO chemistry. Possible extensions of the present work may include compounds. Potentially,

17

17

O isotopic labeling and NMR studies of N- and O-nitroso

O NMR can also be useful in probing posttranslational

nitrosation of proteins.

Acknowledgement This work was supported by the Natural Sciences and Engineering Research Council (NSERC) of Canada. Access to the 900 MHz NMR spectrometer was provided by the National Ultrahigh Field NMR Facility for Solids (Ottawa, Canada), a national research

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facility funded by a consortium of Canadian universities, National Research Council Canada

and

Bruker

BioSpin

and

managed

by

the

University

of

Ottawa

(http://nmr900.ca). We thank Dr. Victor Terskikh for assistance in obtaining the solidstate

17

O NMR spectra at 21.1 T. Y. G. thanks "Provincial Talent Development Fund”

(grant No. 802160100413) for support.

References (1) (2) (3) (4)

(5) (6)

(7) (8) (9) (10) (11)

(12) (13) (14)

Williams, D. L. H. The Chemistry of S-Nitrosothiols. Acc. Chem. Res. 1999, 32, 868-876. Stamler, J. S.; Toone, E. J. The Decomposition of Thionitrites. Curr. Opin. Chem. Biol. 2002, 6, 779-785. Hogg, N. The Biochemistry and Physiology of S-Nitrosothiols. Annu. Rev. Pharmacol. Toxicol. 2002, 42, 585–600. Wang, P. G.; Xian, M.; Tang, X.; Wu, X.; Wen, Z.; Cai, T.; Janczuk, A. J. Nitric Oxide Donors: Chemical Activities and Biological Applications. Chem. Rev. 2002, 102, 1091–1134. Stamler, J. S. S-Nitrosothiols in the Blood. Circ. Res. 2004, 94, 414–417. Liu, L.; Yan, Y.; Zeng, M.; Zhang, J.; Hanes, M. A.; Ahearn, G.; McMahon, T. J.; Dickfeld, T.; Marshall, H. E.; Que, L. G.; Stamler, J. S. Essential Roles of SNitrosothiols in Vascular Homeostasis and Endotoxic Shock. Cell 2004, 116, 617– 628. Hess, D. T.; Matsumoto, A.; Kim, S.-O.; Marshall, H. E.; Stamler, J. S. Protein SNitrosylation: Purview and Parameters. Nat. Rev. Mol. Cell Biol. 2005, 6, 150-166. Smith, B. C.; Marletta, M. A. Mechanisms of S-Nitrosothiol Formation and Selectivity in Nitric Oxide Signaling. Curr. Opin. Chem. Biol. 2012, 16, 498-506. Paulsen, C. E.; Carroll, K. S. Cysteine-Mediated Redox Signaling: Chemistry, Biology, and Tools for Discovery. Chem. Rev. 2013, 113, 4633-4679. Zaman, K.; Fraser-Butler, M.; Bennett, D. Novel S-Nitrosothiols Have Potential Therapeutic Uses for Cystic Fibrosis. Curr. Pharma. Des. 2013, 19, 3509-3520. Whiteman, M.; Moore, P. K. Hydrogen Sulfide and the Vasculature: A Novel Vasculoprotective Entity and Regulator of Nitric Oxide Bioavailability. J. Cell. Mol. Med. 2009, 13, 488-507. King, S. B. Potential Biological Chemistry of Hydrogen Sulfide (H2S) with the Nitrogen Oxides. Free Radic. Biol. Med. 2013, 55, 1-7. Li, Q.; Lancaster, Jr., J. R. Chemical Foundations of Hydrogen Sulfide Biology. Nitric Oxide 2013, 35, 21-34. Ono, K.; Akaike, T.; Sawa, T.; Kumagai, Y.; Wink, D. A.; Tantillo, D. J.; Hobbs, A. J.; Nagy, P.; Xian, M.; Lin, J.; Fukuto, J. M. Redox Chemistry and Chemical

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Biology of H2S, Hydropersulfides, and Derived Species: Implications of Their Possible Biological Activity and Utility. Free Radic. Biol. Med. 2014, 77, 82-94. Kolluru, G. K.; Yuan, S.; Shen, X.; Kevil, C. G. H2S Regulation of Nitric Oxide Metabolism. Methods Enzymol. 2015, 554, 271-297. Filipovic, M. R.; Miljkovic, J. L.; Nauser, T.; Royzen, M.; Klos, K.; Shubina, T.; Koppenol, W. H.; Lippard, S. J.; Ivanovic-Burmazovic, I. Chemical Characterization of the Smallest S-Nitrosothiol, HSNO; Cellular Cross-Talk of H2S and S-Nitrosothiols. J. Am. Chem. Soc. 2012, 134, 12016-12027. Cortese-Krott, M. M.; Fernandez, B. O.; Santos, J. L. T.; Mergia, E.; Grman, M.; Nagy, P.; Kelm, M.; Butler, A.; Feelisch, M. Nitrosopersulfide (SSNO–) Accounts for Sustained NO Bioactivity of S-Nitrosothiols Following Reaction with Sulfide. Redox. Biol. 2014, 2, 234-244. Berenyiova, A.; Grman, M.; Mijuskovic, A.; Stasko, A.; Misak, A.; Nagy, P.; Ondriasova, E.; Cacanyiova, S.; Brezova, V.; Feelisch, M.; Ondrias, K. The Reaction Products of Sulfide and S-Nitrosoglutathione Are Potent Vasorelaxants. Nitric Oxide 2015, 46, 123-130. Cortese-Krott, M. M.; Kuhnle, G. G. C.; Dyson, A.; Fernandez, B. O.; Grman, M.; DuMond, J. F.; Barrow, M. P.; McLeod, G.; Nakagawa, H.; Ondrias, K.; Nagy, P.; King, S. B.; Saavedra, J. E.; Keefer, L. K.; Singer, M.; Kelm, M.; Butler, A. R.; Feelish, M. Key Bioactive Reaction Products of the NO/H2S Interaction are S/NHybrid Species, Polysulfides, and Nitroxyl. Proc. Natl. Acad. Sci. U.S.A. 2015, 112, E4651-E4660. Wedmann, R.; Zahl, A.; Shubina, T. E.; Dürr, M.; Heinemann, F. W.; Bugenhagen, B. E. C.; Burger, P.; Ivanovic-Burmazovic, I.; Filipovic, M. R. Does Perthionitrite (SSNO–) Account for Sustained Bioactivity of NO? A (Bio)chemical Characterization. Inorg. Chem. 2015, 54, 9367-9380. Cortese-Krott, M. M.; Bulter, A. R.; Woollins, J. D.; Feelisch, M. Inorganic SulfurNitrogen Compounds: From Gunpowder Chemistry to the Forefront of Biological Signaling. Dalton Trans. 2016, 45, 5908-5919. Field, L.; Dilts, R. V.; Ravichandran, R.; Lenhert, P. G.; Carnahan, G. E. An Unusually Stable Thionitrite from N-Acetyl-D,L-Penicillamine; X-Ray Crystal and Molecular Structure of 2-(Acetylamino)-2-carboxy-1,1-dimenthylethyl Thionitrite. J. Chem. Soc. Chem. Comm. 1978, 249-250. Arulsamy, N.; Bohle, D. S.; Butt, J. A.; Irvine, G. J.; Jordan, P. A.; Sagan, E. Interrelationships between Conformational Dynamics and the Redox Chemistry of S-Nitrosothiols. J. Am. Chem. Soc. 1999, 121, 7115-7123. Bartberger, M. D.; Houk, K. N.; Powell, S. C.; Mannion J. D.; Lo, K. Y.; Stamler, J. S.; Toone, E. J. Theory, Spectroscopy, and Crystallographic Analysis of SNitrosothiols: Conformational Distribution Directs Spectroscopic Behavior. J. Am. Chem. Soc. 2000, 122, 5889-5890. Goto, K.; Hino, Y.; Kawashima, T.; Kaminaga, M.; Yano, E.; Yamamoto, G.; Takagi, N.; Nagase, S. Synthesis and Crystal Structure of a Stable S-Nitrosothiol Bearing a Novel Steric Protection Group and of the Corresponding S-Nitrothiol. Tetrahedron Lett. 2000, 41, 8479-8483.

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(26) Yi, J.; Khan, M. A.; Lee, J.; Richter-Addo, G. B. The Solid-State Molecular Structure of the S-Nitroso Derivative of L-Cysteine Ethyl Ester Hydrochloride. Nitric Oxide 2005, 12, 261-266. (27) Bonnett, R.; Holleyhead, R.; Johnson, B. L.; Randall, E. W. Reaction of Acidified Nitrite Solutions with Peptide Derivatives: Evidence for Nitrosamine and Thionitrite Formation from 15N NMR Studies. J. Chem. Soc. Perkin I 1975, 22612264. (28) Wang, K.; Hou, Y.; Zhang, W.; Ksebati, M. B.; Xian, M.; Cheng, J.-P.; Wang, P. G. 15N NMR and Electronic Properties of S-Nitrosothiols. Bioorg. Med. Chem. Lett. 1999, 9, 2897–2902. (29) Perissinotti, L. L.; Turjanski, A. G.; Estrin, D. A.; Doctorovich, F. Transnitrosation of Nitrosothiols: Characterization of an Elusive Intermediate. J. Am. Chem. Soc. 2005, 127, 486-487. (30) Bonner, F. T.; Degani, H.; Akhtar, M. J. Nitrogen-15 Magnetic Resonance Spectroscopy of Trioxodinitrate: N-Protonation of an Oxoanion. J. Am. Chem. Soc. 1981, 103, 3739-3742. (31) Akhtar, M. J.; Balschi, J. A.; Bonner, F. T. Nitrogen-15 NMR and Tracer Determination of Protonation Site and Mechanism of Decomposition of Aqueous Hyponitrite. Inorg. Chem. 1982, 21, 2216-2218. (32) Mason, J.; Larkworthy, L. F.; Moore, E. A. Nitrogen NMR Spectroscopy of Metal Nitrosyls and Related Compounds. Chem. Rev. 2002, 102, 913-934. (33) Gao, Y.; Toubaei, A.; Kong, X.; Wu, G. Acidity and Hydrogen Exchange Dynamics of Iron(II)-Bound Nitroxyl in Aqueous Solution. Angew. Chem. Int. Ed. 2014, 53, 11547-11551. (34) Gao, Y.; Toubaei, A.; Kong, X.; Wu, G. Solving the 170-Year-Old Mystery about Red-Violet and Blue Transient Intermediates in the Gmelin Reaction. Chem. Eur. J. 2015, 21, 17172-17177. (35) Gao, Y.; Mossing, B.; Wu, G. Direct NMR Detection of the Unstable “Red Product” from the Reaction between Nitroprusside and 2-Mercaptosuccinic Acid. Dalton Trans. 2015, 44, 20338-20343. (36) Lu, J.; Kong, X.; Terskikh, V.; Wu, G. Solid-State 17O NMR of Oxygen-Nitrogen Singly Bonded Compounds: Hydroxylammonium Chloride and Sodium Trioxodinitrate (Angeli’s Salt). J. Phys. Chem. A 2015, 119, 8133-8138. (37) Wu, G. Solid-State 17O NMR Studies of Organic and Biological Molecules. Prog. Nucl. Magn. Reson. Spectrosc. 2008, 52, 118-169. (38) Wong, A.; Poli, F. Solid-State 17O NMR Studies of Biomolecules. Annu. Rep. NMR Spectrosc. 2014, 83, 145-220. (39) Wu, G. Solid-State 17O NMR Studies of Organic and Biological Molecules: Recent Advances and Future Directions. Solid State Nucl. Magn. Reson. 2016, 73, 1-14. (40) Lumsden, M. D.; Wu, G.; Wasylishen, R. E.; Curtis, R. D. Solid-State 15N NMR Studies oft he Nitroso Group in the Nitrosobenzene Dimer and p-Nitroso-N,Ndimethylaniline. J. Am. Chem. Soc. 1993, 115, 2825-2832. (41) Salzmann, R.; Wojdelski, M.; McMahon, M.; Havlin, R. H.; Oldfield, E. A SolidState Nitrogen-15 Nuclear Magnetic Resonance Spectroscopic and Quantum Chemical Investigation of Nitrosoarene−Metal Interactions in Model Systems and in Heme Proteins. J. Am. Chem. Soc. 1998, 120, 1349-1356.

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(42) Wu, G.; Zhu, J. F.; Mo, X.; Wang, R. Y.; Terskikh, V. Solid-State 17O NMR and Computational Studies of C-Nitrosoarene Compounds. J. Am. Chem. Soc. 2010, 132, 5143-5155. (43) Hart, T. W. Some Observations Concerning the S-Nitroso and S-Phenylsulphonyl Derivatives of L-Cysteine and Glutathione. Tetrahedron Lett. 1985, 26, 2013. (44) Massiot, D.; Fayon, F.; Capron, M.; King, I.; Le Calve, S.; Alonso, B.; Durand, J.O.; Bujoli, B.; Gan, Z.; Hoatson, G. Modelling One- and Two-Dimensional SolidState NMR Spectra. Magn. Reson. Chem. 2002, 40, 70-76. (45) Te Velde, G.; Bickelhaupt, F. M.; Baerends, E. J.; Fonseca Guerra, C.; Van Gisbergen, S. J. A.; Snijders, J. G.; Ziegler, T. Chemistry with ADF. J. Comput. Chem. 2001, 22, 931-967. (46) Vosko, S. H.; Wilk, L.; Nusair, M. Accurate Spin-Dependent Electron Liquid Correlation Energies for Local Spin Density Calculations: A Critical Analysis. Can. J. Phys. 1980, 58, 1200-1211. (47) Perdew, J. P.; Burke, K.; Ernzerhof, M. Generalized Gradient Approximation Made Simple. Phys. Rev. Lett. 1996, 77, 3865-3868. (48) Schreckenbach, G.; Ziegler, T. Calculation of NMR Shielding Tensors Based on Density Functional Theory and a Scalar Relativistic Pauli-Type Hamiltonian. The Application to Transition Metal Complexes. Int. J. Quantum Chem. 1997, 61, 899918. (49) van Lenthe, E.; Baerends, E. J.; Snijders, J. G. Relativistic Regular Two‐ Component Hamiltonians. J. Chem. Phys. 1993, 99, 4597-4610. (50) van Lenthe, E.; Baerends, E. J.; Snijders, J. G. Relativistic Total Energy Using Regular Approximations. J. Chem. Phys. 1994, 101, 9783-9792. (51) van Lenthe, E.; Snijders, J. G.; Baerends, E. J. The Zero‐Order Regular Approximation for Relativistic Effects: The Effect of Spin–Orbit Coupling in Closed Shell Molecules. J. Chem. Phys. 1996, 105, 6505-6516. (52) Van Lenthe, E.; Van Leeuwen, R.; Baerends, E. J.; Snijders, J. G. Relativistic Regular Two-Component Hamiltonians. Int. J. Quantum Chem. 1996, 57, 281-293. (53) Wu, G.; Mason, P.; Mo, X.; Terskikh, V. Experimental and Computational Characterization of the 17O Quadrupole Coupling and Magnetic Shielding Tensors for p-Nitrobenzaldehyde and Formaldehyde. J. Phys. Chem. A 2008, 112, 10241032. (54) Widdifield, C. M.; Schurko, R. W. Understanding Chemical Shielding Tensors Using Group Theory, MO Analysis, and Modern Density-Functional Theory. Concepts Magn. Reson. A 2009, 34, 91-123. (55) Autschbach, J. Analyzing NMR Shielding Tensors Calculated with TwoComponent Relativistic Methods Using Spin-Free Localized Molecular Orbitals. J. Chem. Phys. 2008, 128, 164112. (56) Ramsey, N. F. Magnetic Shielding of Nuclei in Molecules. Phys. Rev. 1950, 78, 699-703. (57) Jameson, C. J.; Gutowsky, H. S. Calculation of Chemical Shifts. I. General Formulation and the Z Dependence. J. Chem. Phys. 1964, 40, 1714-1724.

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Figure Captions

δiso

(a)

δiso

(b)

2000

1500

1000 500 δ(15N)/ppm

0

-500

Figure 1. Experimental (black trace) and simulated (red trace) 15N MAS NMR spectra of (a) [15N]-SNAP and (b) [15N]-GSNO at 14.1 T. The sample spinning frequency was 14500 Hz. Other data acquisition parameters are: (a) 1 s recycle delay, 26000 transients; (b) 10 s recycle delay, 6000 transients.

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(a) 14.1 T

21.1 T

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4000

3000

2000 1000 δ(17O)/ppm

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-1000

(b) 14.1 T

21.1 T

5000

4000

3000

2000 1000 δ(17O)/ppm

0

-1000

Figure 2. Experimental (black trace) and simulated (red trace) 17O static NMR spectra of (a) [17O]-SNAP and (b) [17O]-GSNO at two magnetic fields, 14.1 and 21.1 T. The data acquisition parameters are: at 14.1 T, 1 s recycle delay, 30000 transients; 21.1 T, 2 s recycle delay, 40000 transients. The NMR parameters used in the simulations are summarized in Table 1.

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4000 Computed CS tensor component/ppm

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


17O

3000 15N

2000

1000

0

-1000 -1000

0 1000 2000 3000 Observed CS tensor component/ppm

4000

Figure 3. Comparison between observed and computed 15N (blue circles) and 17O (red circles) chemical shift tensor components for the RSNO compounds. Computational results from anti conformers are used in the plot. The dashed line has a slope of 1.

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(a)

(b)

σ22 σ11

σ11

25°

N=O

23°

S

N=O

χyy

S σ22 χzz

Figure 4. Orientations of (a) the 15N and 17O magnetic shielding (chemical shift) tensors and (b) the 17O quadrupole coupling tensor in the molecular frame of reference for RSNO compounds. The definitions of the tensor components are: σ11 < σ22 < σ33 and χzz > χyy>χxx.

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15N

σ11

#21 (LUMO)

17O

σ22

σ11

σ22

#21

89%

92%

#20 (HOMO) #20 22%

#18

6% #18 #17 9%

7% #17

#15

12%

22% #15 42%

#13

24%

#13

Figure 5. Selected molecular orbitals and their relative energies for anti-MeSNO. Each arrow indicates the magnetic coupling between a pair of MOs that the number shows its relative contribution to σp(occ-vir) along the σ11 and σ22 directions of the 15N and 17O magnetic shielding tensors.

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Page 24 of 33

Table 1. Experimental 15N and 17O NMR tensor parametersa for SNAP and GSNO and the corresponding computed valuesb for t-BuSNO and MeSNO. Compound 15

[ N]SNAP [15N]GSNO [15N]-t-BuSNO [15N]-anti-MeSNO [15N]-syn-MeSNO [17O]SNAP [17O]GSNO [17O]-t-BuSNO [17O]-anti-MeSNO [17O]-syn-MeSNO

Exptl. Exptl. ADF ADF ADF Exptl Exptl. ADF ADF ADF

δiso/ppm 840 765 970 961 889 1310 1060 1481 1473 1359

δ11/ppm 1490 1415 2022 1963 1823 3010 2610 3547 3469 3195

δ22/ppm 678 635 569 572 591 817 750 833 835 845

δ33/ppm 352 245 317 349 254 103 –180 79 115 38

CQ/MHz ηQ — — — — — — — — — — c 14.0 0.3 c 12.0 0.4 14.28 0.14 13.27 0.16 13.71 0.12

Estimated uncertainties in experimental data are: δiso(15N) ±1 ppm; δii(15N), ±5 ppm; δiso(17O) ±5 ppm; δii(17O), ±20 ppm; CQ, ±0.5 MHz; ηQ, ±0.2. b Computed chemical shifts (δ) were obtained from computed shielding values (σ) by using δ = σref – σ where σref(15N) and σref(17O) and were chosen to be 264 and 287 ppm for 15N and 17O, respectively. c The sign of CQ was assumed to be positive on the basis of computational results. a

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Table 2. A summary of individual MO contributions to the total 15N and 17O magnetic shielding tensors in anti-MeSNO. 15

Contribution σp(occ-vir)

σp(total) σp(occ-occ)+ σp(gauge) σd Total

MO mixing #20 → #21 #18 → #21 #17 → #21 #15 → #21 #13 → #21

∆E/eV 3.91 7.41 9.02 10.35 11.10

σ11/ppm −1842     −2061 46 331 −1699

25

N σ22/ppm   −61 −85 −290 −681 57 302 −308

17

σ33/ppm      −501 132 284 −85


σ11/ppm −3049     −3310 −28 416 −3182

O σ22/ppm −258 −70 −87 −264 −282 −1182 −14 388 −548

σ33/ppm      −265 47 390 172


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H 2C

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HO

N H

NH2

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O

H N

OH

OH

O

GSNO O

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N

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C CH ACS Paragon PlusCHEnvironment 3

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syn MeSNO

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The Journal of Physical Chemistry Page 28 of 33

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Computed CS tensor component/ppm

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15N

σ11

#21 (LUMO)

17O

σ22

σ11

σ22

#21

89%

92%

#20 (HOMO) #20 22% #18

6% #18 #17 9%

7% #17

#15

12%

22% #15 42%

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Solid-State 15N and 17O NMR Studies of S-Nitrosothiols - The Journal

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