1. School of Chemistry; University of Birmingham; Edgbaston B15 2TT UK
2. Institute of Microbiology and Infection - School of Biosciences; University of Birmingham; Edgbaston B15 2TT UK
3. Department of Chemistry; University of Warwick; Coventry CV4 7AL UK
4. Current address: School of Chemistry and Biosciences; University of Bradford; Bradford BD7 1DP
5. Current address: Department of Microbiology and Molecular Genetics; University of Texas Health Science Center; Houston (TX) USA