title: The Authors Reply.
authors.affiliation: Structural Biology Unit, NIDA IRP, NIH, Baltimore, Maryland, USA.
authors.forename: Ludovic
authors.initials: L
authors.lastname: Muller
authors.affiliation: Structural Biology Unit, NIDA IRP, NIH, Baltimore, Maryland, USA.
authors.forename: Shelley N
authors.initials: SN
authors.lastname: Jackson
authors.affiliation: Structural Biology Unit, NIDA IRP, NIH, Baltimore, Maryland, USA. Electronic address: awoods@mail.nih.gov.
authors.forename: Amina S
authors.initials: AS
authors.lastname: Woods