1. Department of Chemistry and Center for Protein Structure and Function, Faculty of Science, Mahidol University, Rama VI Road, Bangkok 10400, Thailand, Department of Microbiology, Faculty of Pharmaceutical Sciences, Chulalongkorn University, Phyathai Road, Bangkok 10300, Thailand, and Department of Microbiology, Faculty of Science, Mahidol University, Rama VI Road, Bangkok 10400, Thailand