Passive loss of hydrogen sulfide in biological experiments
Section snippets
H2S measurement
An amperometric H2S sensor was built in-house [11] or purchased (model HS-700, Innovative Instruments, Tampa, FL, USA) and used in conjunction with an Apollo free radical analyzer (World Precision Instruments, Sarasota, FL, USA). These sensors measure H2S gas that is in the equilibrium: H2S ⇄ HS− ⇄ S2−, with pKa1 = 6.9 and pKa2 > 11 [24]. At physiological pH (∼7.4 blood and ∼6.9 intracellular), the concentration of H2S ranges from 25% to 50% of the total dissolved sulfide. However, the equilibrium can
Formation of H2S on solvation
H2S gas is formed nearly instantaneously on solvation in buffer (Fig. 1). The reaction is nearly 80% complete within the first 10 s. By 20 s, H2S gas concentration reaches a maximum and falls exponentially thereafter. The t1/2 for H2S loss varied with the stirring rate but was not characterized further. Physical dissolution of H2S appears to be the rate-limiting step in formation of H2S gas within the time resolution of this method.
Muzaffar and coworkers [25] showed that when NaHS is placed in
Summary
Over the past 25 years, our concept of H2S has gone from a toxic gas to a signaling molecule with potential clinical relevance. Our knowledge of the effects of exogenous H2S on biological systems has outpaced our understanding of how these systems affect H2S. The development of H2S gas sensors capable of measuring H2S in real time and on unadulterated tissues has downgraded our estimates of endogenous H2S production and tissue concentrations. In this study, we have shown that even the residence
Acknowledgments
The authors thank K. Hurley for technical assistance. This work was supported in part by National Science Foundation Grants IOS 0641436 and IOS 1051627.
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