I am trying to pulldown my GFP fused protein of interest using ChromoTek GFP-Trap® Magnetic Agarose. My protein is not binding to the beads. Expression of the GFP-fusion protein has been confirmed by input lane as well as by microscopy. I have tried different salt concentrations (100 to 150 mM NaCl), 50mM Tris pH 7.5, 0.5% Triton X-100. Nothing is working and all the protein is going in the flowthrough instead of binding to the beads. My protein size is 140 kDa, is it too large for those beads? Should I look into some other manufacturer's product? I really appreciate any suggestions that you may have.