Bio-Synthesis offers a complete array of fluorescent reporters and quenchers. Our product offering includes common dye modifiers such as 6-FAM, HEX and TET, as well as exotic modifications. We can directly attach fluorescent dyes to oligos at the 5'-end, 3'-end and even internal positions of an oligonucleotides during synthesis. When certain modifications (such as Digoxigenin and some fluorescent dyes) are not available for direct incorporation, cross-linking two molecules by using a specific functional group such as an amine, thiol modified oligonucleotide with an certain cross linkers are employed. See Chemistry behind cross linking Post-synthetic chemical modifications made to an oligonucleotide result in lower yields than modifications introduced during synthesis. Further, all post synthetic conjugation require HPLC purification. PAGE purification is not offered for post synthetic conjugation as yields are further decreased and certain modifications can be damaged during PAGE purification.