Supporting Information S-Nitrosothiol Detection via Amperometric Nitric Oxide Sensor with Surface Modified Hydrogel Layer Containing Immobilized Organoselenium Catalyst Wansik Cha and Mark E. Meyerhoff* Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, Michigan 48109-1055 Figure 1S. Influence of oxygen concentration in sample solution on the calibration curves of RSe-based RSNO sensor in response of NO and GSNO in the presence of GSH. Figure 2S. Influence of the concentration of oxygen and GSH in sample solution on the amperometric signal of RSe-based RSNO sensor in response of GSNO. Figure 3S. Real-time RSNO detection profiles in sheep plasma and sheep blood. Figure 4S. Influence of sample media (PBS, plasma and blood) on the amperometric sensitivities of the Se-based RSNO sensor in the absence or presence of GSH for the detection of GSNO. Figure 5S. Influence of sample media (PBS, plasma and blood) on the amperometric sensitivities of the Se-based RSNO sensor in the absence or presence of GSH for the detection of SNAP. *To whom correspondence should be addressed. Email: mmeyerho@umich.edu