How stable are Alexa dyes ?
Most peptides are synthesized via solid-phase chemistry, where peptide chain is assembled on a resin. After completion of synthesis, peptide is cleaved most commonly using trifluoroacetic acid. Normally a dye is attached to a peptide during synthesis, while all side-chains on the peptide that can react with the dye are protected. Once the dye is coupled to the peptide, it is cleaved from the resin and all protecting groups are removed. However same approach can’t be applied to some dyes such as Alexa dyes, because they are not stable during cleavage of peptide from resin. These dyes can only be coupled to a peptide post synthesis where internal Lysines, arginines, and histadines can also react with the dye, therefore Cysteine is used with a dye that has a maleimide functional group.
Print
05/15/2014