Department of Biology, Theoretical Biophysics, Humboldt-Universität zu Berlin, 10115 Berlin, Germany and Chemical Engineering Department, Indian Institute of Technology Bombay, Mumbai 400 076, India.|Department of Biology, Theoretical Biophysics, Humboldt-Universität zu Berlin, 10115 Berlin, Germany and Chemical Engineering Department, Indian Institute of Technology Bombay, Mumbai 400 076, India.|Department of Biology, Theoretical Biophysics, Humboldt-Universität zu Berlin, 10115 Berlin, Germany and Chemical Engineering Department, Indian Institute of Technology Bombay, Mumbai 400 076, India.|Department of Biology, Theoretical Biophysics, Humboldt-Universität zu Berlin, 10115 Berlin, Germany and Chemical Engineering Department, Indian Institute of Technology Bombay, Mumbai 400 076, India.