The species-specific chemical shifts determined for the additional compounds studied (beyond cysteine and cystine) bearing thiolate moiety.

The uncertainty of determination for chemical shift on the ppm scale is 0.001 and 0.01 for 1H and 13C chemical shift values, respectively. The thiolate protonation constants of glutathione were determined previously in [14], while the protonation constants of the peptides were determined as described in the Materials and Methods section and are reported in logk ± standard deviation of the regression fit.以ppm为计量单位的化学位移测定不确定度，对于¹H化学位移值为0.001，¹³C化学位移值则为0.01。谷胱甘肽的硫醇盐质子化常数此前已在文献[14]中完成测定；本研究中肽类的质子化常数则按照“材料与方法”部分所述方法进行测定，结果以logk ± 回归拟合标准偏差的形式予以报告。