High Magnetic Field Laboratory, Chinese Academy of Sciences, Hefei, P. R. China.|The Graduate Center, The City University of New York, New York, USA.|Department of Chemistry, Hunter College, The City University of New York, New York, USA.|Office of the Director, National Institutes of Health, Bethesda, MD, USA.|The Graduate Center, The City University of New York, New York, USA. lxie@iscb.org.