1. Contribution from the School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, 35 Stirling Highway, Crawley, Perth WA 6009 Australia, Centre of Microscopy and Microanalysis, University of Western Australia, 35 Stirling Highway, Crawley, Perth WA 600,9 Australia, and Department of Chemistry, Faculty of Science, Mahidol University, Bangkok 10400, Thailand