Using resonance synchronous spectroscopy to characterize the reactivity and electrophilicity of biologically relevant sulfane sulfur
Huanjie Li,
Huaiwei Liu,
Zhigang Chen,
Rui Zhao,
Qingda Wang,
Mingxue Ran,
Yongzhen Xia,
Xin Hu,
Jihua Liu,
Ming Xian,
Luying Xun
Affiliations
Huanjie Li
State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao, 266237, People's Republic of China
Huaiwei Liu
State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao, 266237, People's Republic of China; Corresponding author.
Zhigang Chen
State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao, 266237, People's Republic of China
Rui Zhao
State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao, 266237, People's Republic of China
Qingda Wang
State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao, 266237, People's Republic of China
Mingxue Ran
State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao, 266237, People's Republic of China
Yongzhen Xia
State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao, 266237, People's Republic of China
Xin Hu
Institute of Marine Science and Technology, Shandong University, 72 Binhai Road, Qingdao, 266237, People's Republic of China
Jihua Liu
Institute of Marine Science and Technology, Shandong University, 72 Binhai Road, Qingdao, 266237, People's Republic of China
Ming Xian
Department of Chemistry, Washington State University, Pullman, WA, 99164-4630, USA
Luying Xun
State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao, 266237, People's Republic of China; School of Molecular Biosciences, Washington State University, Pullman, WA, 99164-7520, USA; Corresponding author. State Key Laboratory of Microbial Technology, Shandong University, 72 Binhai Road, Qingdao, 266237, People's Republic of China.
Sulfane sulfur is common inside cells, playing both regulatory and antioxidant roles. However, there are unresolved issues about its chemistry and biochemistry. We report the discovery that reactive sulfane sulfur such as polysulfides and persulfides could be detected by using resonance synchronous spectroscopy (RS2). With RS2, we showed that inorganic polysulfides at low concentrations were unstable with a half-life about 1 min under physiological conditions due to reacting with glutathione. The protonated form of glutathione persulfide (GSSH) was electrophilic and had RS2 signal. GSS− was nucleophilic, prone to oxidation, but had no RS2 signal. Using this phenomenon, pKa of GSSH was determined as 6.9. GSSH/GSS− was 50-fold more reactive than H2S/HS− towards H2O2 at pH 7.4, supporting reactive sulfane sulfur species like GSSH/GSS− may act as antioxidants inside cells. Further, protein persulfides were shown to be in two forms: at pH 7.4 the deprotonated form (R-SS-) without RS2 signal was not reactive toward sulfite, and the protonated form (R-SSH) in the active site of a rhodanese had RS2 signal and readily reacted with sulfite to produce thiosulfate. These data suggest that RS2 of sulfane sulfur is likely associated with its electrophilicity. Sulfane sulfur showed species-specific RS2 spectra and intensities at physiological pH, which may reveal the relative abundance of a reactive sulfane sulfur species inside cells.