Non radio active labeling for oligonuleotides include:
Biotin-labelled oligonucleotides - this biotin can be used to link the oligonucleotide to streptavidin-protein conjugates, streptavidin affinity columns, or labelled streptavidin. Attachment of a biotin molecule to the 3' terminus can also be used to prevent 3' exonuclease digestion and 3' extension during amplification reactions.
Digoxigenin (DIG) is mainly used as a non-isotopic label for DNA and oligonucleotides in a wide range of applications: diagnostics, sequencing, blot applications, and in situ hybridization. The digoxigenin label can be detected with enzyme-linked immunoassays for anti-digoxigenin protein conjugates, and visualized through a chemiluminescent reaction.
DNP means 2,4-Dinitrophenyl. DNP can be introduced anywhere in the sequence and on either terminus.DNP is an alternative to digoxigenin in cases where two different genes must be detected together. Oligonucleotides labelled with DNP can therefore be used in analytical tests based on anti-DNP antibodies.
For other non radioactive labeling, check this site: www.biosyn.com, they offer various oligonucleotide modifications and labelings.