Investigating and Applying Tools to Better Understand Biologically Relevant COS and H2S

Abstract

Hydrogen sulfide (H2S) is an endogenously produced signaling molecule important to a variety of physiological functions. H2S plays a role in functions like vasodilation, angiogenesis, neuromodulation, and antioxidant effects. Due to its importance in biology, quantification and delivery of H2S have become key methods to both understand this small molecule gas and also have impacts in longer-term therapeutic applications. The areas of detecting, quantifying, and delivering H2S have been well investigated, however there are key limitations in each of these areas that are topics of contemporary research. Carbonyl sulfide (COS) shares an intertwined history with H2S because the ubiquitous enzyme carbonic anhydrase (CA) rapidly converts COS to H2S. In addition to the enzymatic conversion by CA, COS has been detected in mammalian tissues and exhaled breath, further implicating its potential role in mammals. The specific physiological role of COS is not well understood, and current efforts in the field include detection and quantification of COS in various environments. Overall, improved tools are needed to better understand the biological chemistry of COS and H2S, and to improve strategic methods of donating COS/H2S for therapeutic applications.

In this dissertation two main areas of research are addressed: (1) Improving the mechanistic understanding of H2S probes and donors, and (2) increasing the fundamental understanding of COS in biological systems. Chapter I is a perspective on advancing tools for measurement and detection of H2S in chemical biology covering fluorescent probes, colorimetric assays, HPLC quantification, H2S-specific electrodes, and more. Chapter II focuses on the selectivity of thiophene-2-carboxylic acid ester probes and cautions their use in biological systems. Chapter III demonstrates COS release as the main pathway for H2S release for 1,2,4 thiadiazolidin-3,5-dione H2S donors. Chapter IV includes the investigation of COS kinetics with CA-II using more contemporary approaches. Additionally, this chapter includes preliminary results for comparing COS conversion to H2S by CA-II and CA-IX. Chapter V highlights the quantification of COS from Mo/W-Tp systems to assist in determining the pathway of COS release. Furthermore, this chapter quantifies COS from a COS-based H2S donor for the first time to our knowledge.

This dissertation includes previously published and un-published co-authored materials.