skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.


Title: Dithioesters: simple, tunable, cysteine-selective H 2 S donors
Dithioesters have a rich history in polymer chemistry for RAFT polymerizations and are readily accessible through different synthetic methods. Here we demonstrate that the dithioester functional group is a tunable motif that releases H 2 S upon reaction with cysteine and that structural and electronic modifications enable the rate of cysteine-mediated H 2 S release to be modified. In addition, we use (bis)phenyl dithioester to carry out kinetic and mechanistic investigations, which demonstrate that the initial attack by cysteine is the rate-limiting step of the reaction. These insights are further supported by complementary DFT calculations. We anticipate that the results from these investigations will allow for the further development of dithioesters as important chemical motifs for studying H 2 S chemical biology.  more » « less
Award ID(s):
1625529
PAR ID:
10309016
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  
Date Published:
Journal Name:
Chemical Science
Volume:
10
Issue:
6
ISSN:
2041-6520
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. Li–S batteries have attracted great attention for their combined advantages of potentially high energy density and low cost. To tackle the capacity fade from polysulfide dissolution, we have developed a confinement approach by in situ encapsulating sulfur with a MOF-derived CoS 2 in a carbon framework (S/Z-CoS 2 ), which in turn was derived from a sulfur/ZIF-67 composite (S/ZIF-67) via heat treatment. The formation of CoS 2 was confirmed by X-ray absorption spectroscopy (XAS) and its microstructure and chemical composition were examined through cryogenic scanning/transmission electron microscopy (Cryo-S/TEM) imaging with energy dispersive spectroscopy (EDX). Quantitative EDX suggests that sulfur resides inside the cages, rather than externally. S/hollow ZIF-67-derived CoS 2 (S/H-CoS 2 ) was rationally designed to serve as a control material to explore the efficiency of such hollow structures. Cryo-STEM-EDX mapping indicates that the majority of sulfur in S/H-CoS 2 stays outside of the host, despite its high void volumetric fraction of ∼85%. The S/Z-CoS 2 composite exhibited highly improved battery performance, when compared to both S/ZIF-67 and S/H-CoS 2 , due to both the efficient physical confinement of sulfur inside the host and strong chemical interactions between CoS 2 and sulfur/polysulfides. Electrochemical kinetics investigations revealed that the CoS 2 could serve as an electrocatalyst to accelerate the redox reactions. The composite could provide an areal capacity of 2.2 mA h cm −2 after 150 cycles at 0.2C and 1.5 mA h cm −2 at 1C. This novel material provides valuable insights for further development of high-energy, high-rate and long-life Li–S batteries. 
    more » « less
  2. Abstract H2S is a gaseous signaling molecule that modifies cysteine residues in proteins to form persulfides (P‐SSH). One family of proteins modified by H2S are zinc finger (ZF) proteins, which contain multiple zinc‐coordinating cysteine residues. Herein, we report the reactivity of H2S with a ZF protein called tristetraprolin (TTP). Rapid persulfidation leading to complete thiol oxidation of TTP mediated by H2S was observed by low‐temperature ESI‐MS and fluorescence spectroscopy. Persulfidation of TTP required O2 , which reacts with H2S to form superoxide, as detected by ESI‐MS, a hydroethidine fluorescence assay, and EPR spin trapping. H2S was observed to inhibit TTP function (binding to TNFα mRNA) by an in vitro fluorescence anisotropy assay and to modulate TNFα in vivo. H2S was unreactive towards TTP when the protein was bound to RNA, thus suggesting a protective effect of RNA. 
    more » « less
  3. Similar to hydrogen sulfide (H 2 S), its chalcogen congener, Hydrogen selenide (H 2 Se), is an emerging molecule of interest given its endogenous expression and purported biological activity. However, unlike H 2 S, detailed investigations into the chemical biology of H 2 Se are limited and little is known about its innate physiological functions, cellular targets, and therapeutic potential. The obscurity surrounding these fundamental questions is largely due to a lack of small molecule donors that can effectively increase the bioavailability of H 2 Se through their continuous liberation of the transient biomolecule under physiologically relevant conditions. Driven by this unmet demand for H 2 Se-releasing moieties, we report that γ-keto selenides provide a useful platform for H 2 Se donation via an α-deprotonation/β-elimination pathway that is highly dependent on both pH and alpha proton acidity. These attributes afforded a small library of donors with highly variable rates of release (higher alpha proton acidity = faster selenide liberation), which is accelerated under neutral to slightly basic conditions—a feature that is unique and complimentary to previously reported H 2 Se donors. We also demonstrate the impressive anticancer activity of γ-keto selenides in both HeLa and HCT116 cells in culture, which is likely to stimulate additional interest and research into the biological activity and anticancer effects of H 2 Se. Collectively, these results indicate that γ-keto selenides provide a highly versatile and effective framework for H 2 Se donation. 
    more » « less
  4. We report a new terpyridine-based FeN3O catalyst, Fe(tpytbupho)Cl2, which reduces O2 to H2O. Variable concentration and variable temperature spectrochemical studies with decamethylferrocene as a chemical reductant in acetonitrile solution enabled the elucidation of key reaction parameters for the catalytic reduction of O2 to H2O by Fe(tpytbupho)Cl2. These mechanistic studies suggest that a 2 + 2 mechanism is operative, where hydrogen peroxide is produced as a discrete intermediate, prior to further reduction to H2O. Consistent with this proposal, the spectrochemically measured first-order rate constant k (s−1) value for H2O2 reduction is larger than that for O2 reduction. Further, significant H2O2 production is observed under hydrodynamic conditions in rotating ring-disk electrode measurements, where the product can be swept away from the cathode surface before further reduction occurs. 
    more » « less
  5. null (Ed.)
    Functional small molecules afford opportunities to direct solid-state inorganic reactions at low temperatures. Here, we use catalytic amounts of organosilicon molecules to influence the metathesis reaction: FeCl 2 + Na 2 S 2 → 2NaCl + FeS 2 . Specifically, hexaphenyldisiloxane ((C 6 H 5 ) 6 Si 2 O) is shown to increase pyrite yields in metathesis reactions performed at 150 °C. In situ synchrotron X-ray diffraction (SXRD) paired with differential scanning calorimetry (DSC) reveals that diffusion-limited intermediates are circumvented in the presence of (C 6 H 5 ) 6 Si 2 O. Control reactions suggest that the observed change in the reaction pathway is imparted by the Si–O functional group. 1 H NMR supports catalytic behavior, as (C 6 H 5 ) 6 Si 2 O is unchanged ex post facto . Taken together, we hypothesize that the polar Si–O functional group coordinates to iron chloride species when NaCl and Na 2 S 4 form, forming an unidentified, transient intermediate. Further exploration of targeted small molecules in these metathesis reaction provides new strategies in controlling inorganic materials synthesis at low-temperatures. 
    more » « less