3 research outputs found
Chemiluminescent Detection of Enzymatically Produced Hydrogen Sulfide: Substrate Hydrogen Bonding Influences Selectivity for H<sub>2</sub>S over Biological Thiols
Hydrogen sulfide (H<sub>2</sub>S)
is now recognized as an important
biological regulator and signaling agent that is active in many physiological
processes and diseases. Understanding the important roles of this
emerging signaling molecule has remained challenging, in part due
to the limited methods available for detecting endogenous H<sub>2</sub>S. Here we report two reaction-based ChemiLuminescent Sulfide Sensors,
CLSS-1 and CLSS-2, with strong luminescence responses toward H<sub>2</sub>S (128- and 48-fold, respectively) and H<sub>2</sub>S detection
limits (0.7 ± 0.3, 4.6 ± 2.0 μM, respectively) compatible
with biological H<sub>2</sub>S levels. CLSS-2 is highly selective
for H<sub>2</sub>S over other reactive sulfur, nitrogen, and oxygen
species (RSONS) including GSH, Cys, Hcy, S<sub>2</sub>O<sub>3</sub><sup>2–</sup>, NO<sub>2</sub><sup>–</sup>, HNO, ONOO<sup>–</sup>, and NO. Despite its similar chemical structure, CLSS-1
displays lower selectivity toward amino acid-derived thiols than CLSS-2.
The origin of this differential selectivity was investigated using
both computational DFT studies and NMR experiments. Our results suggest
a model in which amino acid binding to the hydrazide moiety of the
luminol-derived probes provides differential access to the reactive
azide in CLSS-1 and CLSS-2, thus eroding the selectivity of CLSS-1
for H<sub>2</sub>S over Cys and GSH. On the basis of its high selectivity
for H<sub>2</sub>S, we used CLSS-2 to detect enzymatically produced
H<sub>2</sub>S from isolated cystathionine γ-lyase (CSE) enzymes
(<i>p</i> < 0.001) and also from C6 cells expressing
CSE (<i>p</i> < 0.001). CLSS-2 can readily differentiate
between H<sub>2</sub>S production in active CSE and CSE inhibited
with β-cyanoalanine (BCA) in both isolated CSE enzymes (<i>p</i> < 0.005) and in C6 cells (<i>p</i> < 0.005).
In addition to providing a highly sensitive and selective reaction-based
tool for chemiluminescent H<sub>2</sub>S detection and quantification,
the insights into substrate–probe interactions controlling
the selectivity for H<sub>2</sub>S over biologically relevant thiols
may guide the design of other selective H<sub>2</sub>S detection scaffolds
Understanding Hydrogen Sulfide Storage: Probing Conditions for Sulfide Release from Hydrodisulfides
Hydrogen sulfide (H<sub>2</sub>S)
is an important biological signaling
agent that exerts action on numerous (patho)Âphysiological processes.
Once generated, H<sub>2</sub>S can be oxidized to generate reductant-labile
sulfane sulfur pools, which include hydrodisulfides/persulfides. Despite
the importance of hydrodisulfides in H<sub>2</sub>S storage and signaling,
little is known about the physical properties or chemical reactivity
of these compounds. We report here the synthesis, isolation, and characterization
(NMR, IR, Raman, HRMS, X-ray) of a small-molecule hydrodisulfide and
highlight its reactivity with reductants, nucleophiles, electrophiles,
acids, and bases. Our experimental results establish that hydrodisulfides
release H<sub>2</sub>S upon reduction and that deprotonation results
in disproportionation to the parent thiol and S<sup>0</sup>, thus
providing a mechanism for transsulfuration in the sulfane sulfur pool
The Intersection of NO and H<sub>2</sub>S: Persulfides Generate NO from Nitrite through Polysulfide Formation
Hydrogen sulfide (H<sub>2</sub>S)
and nitric oxide (NO) are important biosignaling molecules, and their
biochemistries are increasingly recognized to be intertwined. Persulfides
are an oxidized product of biological H<sub>2</sub>S and have emerged
as important species involved in the biological action of reactive
sulfur species. Using isolated persulfides, we employed a combination
of experimental and computational methods to investigate the contribution
of persulfides to H<sub>2</sub>S/NO crosstalk. Our studies demonstrate
that isolated persulfides react with nitrite to produce NO via polysulfide
and perthionitrite intermediates. These results highlight the importance
of persulfides, polysulfides, and perthionitrite as intertwined reactive
nitrogen and sulfur species