You should apply to the Tri-institutional program in chemical biology at Rockefeller/Cornell Weill/Sloan-Kettering. You can work for any of the 500 or so faculty in those three universities. Columbia is nice too though. I know people with <50% Chem GRE but got into Columbia, so I'm sure you have a shot. Amazing faculty, no TAing, nice stipend, live on the upper east side. You should check it out. They have a collaboration with Takeda and Cornell's tech campus is being built up so lots of money and excitement there.