Amino Linker C6 can be used to incorporate an active primary amino group onto the 5’-end of an oligonucleotide. The amino group is separated from the 5’-end nucleotide base by a 6-carbon spacer arm to reduce steric interaction between the amino group and the oligo. The presence of the amino group allows the user to end label the oligo with a variety of different affinity, reporter or protein moieties (as NHS esters or isothiocyanates), depending on the application. Examples include biotin, digoxigenin, and fluorescent dyes or quenchers, and enzymes (for example, alkaline phosphatase).