Oligonucleotide synthesis is performed on solid support that is predominantly controlled pore glass of various pore size (500 Angstrom to 300 Angstrom)or at Gene Link using membrane support as well. For standard unmodified oligos a solid support is used that has the 3' base attached to it. Universal supports do not have any base attached to it and can be used to initiate oligo synthesis. These solid supports are specifically designed to allow coupling of any phosphoramidite to it and at Gene Link used to initiate oligo synthesis for specialty modified bases that can be placed at the 3’-end of an oligonucleotide (1).

The universal support group is removed during deprotection scheme and the 3' base will have a hydroxyl group or the modified base is at the 3' end when supplied to the customer.