Biomathematics and Statistics Scotland, JCMB, The Kings Buildings, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK.|Proteomics Facility Services, Moredun Research Institute, Pentland Science Park, Bush Loan, Penicuik, Mid Lothian, EH26 0PZ, UK.|Biomathematics and Statistics Scotland, JCMB, The Kings Buildings, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK.|Institute of Biological Chemistry, Biophysics and Bioengineering, Heriot-Watt University, Edinburgh, EH14 4AS, UK.