Biological Physics Group, School of Physics & Astronomy, The University of Manchester, Manchester, UK.|Biological Physics Group, School of Physics & Astronomy, The University of Manchester, Manchester, UK.|Biological Physics Group, School of Physics & Astronomy, The University of Manchester, Manchester, UK.|Biological Physics Group, School of Physics & Astronomy, The University of Manchester, Manchester, UK.|Biological Physics Group, School of Physics & Astronomy, The University of Manchester, Manchester, UK.