Kaja Fac Synthesis of biotin labelled cap analogue – incorporable into mRNA transcripts and promoting cap-dependent translation. All eukaryotic mRNAs have at their 5’-end a unique structure called cap, which consist of unusual 7-methylguanosine linked by a 5’,5’-triphosphate bridge to the first transcribed nucleotide. In the work, which I am going to present, a biotin-labelled dinucleotide cap analogue has been designed and prepared. One of the purposes was to obtain the analogue that can be incorporated into transcripts to produce 5’-capped and biotinylated mRNA in vitro which retains its biological functionality and allows the application for biotin-(strept)avidin interaction based experiments. Thus, the analogue was tested for its ability to bind initiation factor eIF4E and for its recognition by streptavidin. Moreover, the synthesized capped, full-length mRNA was tested for its translational efficiency.