Biotin-dT is a deoxythymidine nucleotide base attached to biotin through a long-chain alkyl spacer arm. Biotin-dT is typically used to label an oligonucleotide with biotin at an internal base position, though it can also be used for 5’- and 3’-end labeling as well. Internal biotin-labeling is necessary when an oligo needs to be captured or immobilized, but both ends are unavailable. A good example of this is the use of internal biotin-labeling to facilitate the immobilization of a molecular beacon on a glass slide (1). The internal labeling strategy can also be used to label a hybridization detection probe with several biotins to enhance detection of a target sequence with anti-biotin antibodies attached to colored particles (2), fluorescent dyes, or enzymes.