To determine whether nitration at Y33 or Y56 was relevant to the proliferative activity of nitrated Hsp90 in schwannoma cells, we used genetic code expansion (GCE) to incorporate the noncanonical amino acid nitrotyrosine site-specifically as the sole oxidative modification in the recombinant protein at positions 33 (Hsp90NY33), 56 (Hsp90NY56), or 276 (Hsp90NY276, used as a nitrated control). Here, HSP90AB1 is linked to schwannoma.