Reactive Labels:

Square, Seta, and SeTau dyes are a series of dyes that span the whole visible spectrum and the NIR. They are available with various functionalities: carboxylic acids, as amine-reactive NHS esters for labeling of amino groups on peptides, proteins or amino-modified DNA, as maleimides for coupling to thiol-groups in proteins and thiol-modified oligos and as-amino-modified labels (on request).

With a few exceptions all these reagents are available in either 0.5 mg, 1 mg or 5 mg Pack Sizes. Please do inquire about the availability of bulk quantities.

Among all these functionalities N-hydroxysuccinimide (NHS) ester are the preferred reactive functionality for labeling of amino-groups due to the formation of highly stable amide bonds with amines. Sulfonyl chlorides also form stable sulfamide bonds but the reaction also generates HCl, which is a not so desirable by-product. In addition sulfonyl chlorides are more difficult to synthesize.



Labelling of Thiol-groups:




Maleimides are the preferred functionality for labeling of small molecules such as peptide and oligo-nucleotides. Maleimides form bonds with thiols at relatively mild conditions and with reasonable yields. Maleimides are less susceptible to hydrolysis in comparison with NHS esters.

We would like to refer you to our labeling procedures for specific guidance on how to label with NHS-esters or maleimides.