Fullerenes are a class of nanomaterials with unique electronic properties that can be harnessed for use in various applications. We have found their biologic function critically depends on the structure of the side chain moieties added to the core carbon cage. A therapeutic candidate termed C70-Tetraglutamate (TGA), previously shown to have potent anti-inflammatory properties, was selected to determine the molecular interactions in human serum and in resting or FcεRI-activated human mast cells (MC). The identity of TGA- binding molecules was analyzed using NanoLC-MS/MS peptide sequencing technology. We found that TGA predominately bound to alpha-2-macroglobulin precursor, Serpin peptidase inhibitor, and serum albumin in human serum. In non-activated MC, TGA interacted predominantly with aminopeptidase N precursor, dipeptidyl peptidase 4, and human fibroblast activation. In MC activated through FcεRI, predominant interactions were observed between TGA and annexin A5, superoxide dismutase, and lysosomal membrane glycoprotein. These studies for the first time identify serum and cellular substrates of a fullerene-based anti-inflammatory compound which serves as a starting point for determining the mechanism of action of this therapeutic candidate.