Western blot was performed using OPRM1 Polyclonal Antibody (Product # PA1-24628) and ~53 kDa band corresponding to OPRM1 was observed across cell lines and tissue extracts tested except in Mouse Kidney and Mouse Heart which are reported to be negative. An uncharacterized band (*) at ~110, ~15 kDa was observed in the Rat Brain and Mouse Lungs respectively. Whole cell extracts (30 µg lysate) of (Fig. a) SH-SY5Y (Lane 1), SK-N-AS (Lane 2), IMR-32 (Lane 3), U-2 OS (Lane 4), MCF7 (Lane 5), Neuro-2a (Lane 6), A549 (Lane 7), tissue extracts (30 µg lysate) of Mouse Testis (Lane 8), Mouse Brain (Lane 9), Rat Brain (Lane 10) and Mouse Lungs (Lane 11); (Fig. b) tissue extracts (30 µg lysate) of Mouse Brain (Lane 1), Rat Brain (Lane 2), Mouse Testis (Lane 3), Rat Testis (Lane 4), Mouse Lungs (Lane 5), Mouse Kidney (Lane 6) and Mouse Heart (Lane 7) were electrophoresed using NuPAGE® 10% Bis-Tris gel (Product # NP0302BOX). Resolved proteins were then transferred onto a nitrocellulose membrane (Product # IB23001) by iBlot® 2 Dry Blotting System (Product # IB21001).The blot was probed with the primary antibody (1:1,000 dilution) and detected by chemiluminescence with Goat anti-Rabbit IgG (Heavy Chain) Superclonal™ Recombinant Secondary Antibody, HRP (Product # A27036, 1:4,000 dilution) using the iBright FL 1000 (Product # A32752). Chemiluminescent detection was performed using Novex® ECL Chemiluminescent Substrate Reagent Kit (Product # WP20005).