In vitro transcription and translation p2luc-BM2 reporter plasmids were linearised with HpaI and capped run-off transcripts generated using T7 RNA polymerase as described previously [25] . Messenger RNAs were recovered by a single extraction with phenol/chloroform (1:1 v/v) followed by ethanol precipitation. Remaining unincorporated nucleotides were removed by gel filtration through a NucAway spin column (Ambion). The eluate was concentrated by ethanol precipitation, the mRNA resuspended in water, checked for integrity by agarose gel electrophoresis and quantified by spectrophotometry.