CUBIC, Department of Biochemistry and Molecular Biophysics, Columbia University 650 West 168th Street BB217, New York, NY 10032, USA. punta@cubic.bioc.columbia.edu|CUBIC, Department of Biochemistry and Molecular Biophysics, Columbia University 650 West 168th Street BB217, New York, NY 10032, USA. punta@cubic.bioc.columbia.edu