Bromoacetamido-dPEG®₁₂-Tris(-dPEG®₁₁-bromoacetamide)₃

Bromoacetamido-dPEG®12-Tris(-dPEG®11-amido-bromoacetamide)3, product number QBD-11434, is a branched, single molecular weight, thiol-reactive, discrete polyethylene glycol (dPEG®) product. It is designed to join up to four molecules via a thiol-bromoacetyl reaction. Each of the four arms attaches to a central tris core and terminates with a thiol-reactive bromoacetyl group. The dPEG® spacer length from between the bromoacetyl groups through the tris core is 87 atoms (100.0 Å).

Like the thiol-maleimide reaction, the thiol-bromoacetyl reaction forms stable thioether bonds with free thiols. However, maleimides react optimally at pH 6.5 – 7.5, while bromoacetyl groups react with thiols chemoselectively at pH ≥8.0. Moreover, thioether bonds formed from a thiol-maleimide reaction can sometimes undergo a reverse Michael addition, undoing the thioether bond. This does not happen with thioether bonds formed by a thiol-bromoacetyl reaction. The thiol-bromoacetyl reaction is chemoselective for thiols but slightly less selective than the thiol-maleimide reaction.

Unlike traditional polyethylene glycol (PEG), which are non-uniform, dispersed polymers, Vector Laboratories’ dPEG® products are single molecular weight PEGs with discrete chain lengths, hence the dPEG® name. The four arms of MAL-dPEG®12-Tris(-dPEG®11-amido-MAL)3 are built around a core of tris(hydroxymethyl)aminomethane (“”tris””). Although one arm is structured a little differently than the other three arms (one dPEG®12 arm vs. three dPEG®11 arms), the product is essentially symmetrical through the tris core. This precise construction of Bromoacetamido-dPEG®12-Tris(-dPEG®11-amido-bromoacetamide)3 is possible because of Vector Laboratories’ dPEG® technology. This product can link multiple peptides or proteins together for drug delivery. It could also be used as a core unit for constructing dendrimers with precisely defined spacer lengths.