Photo-induced cross-linking of unmodified proteins

[2] In 2001, Gal Bitan, Aleksey Lomakin, and David B. Teplow applied PICUP to study amyloid β-protein (Aβ) oligomerization, which is observed in Alzheimer's disease.

[3] Coupling PICUP with sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), the distribution of oligomers in rapid equilibrium was quantified.

The mechanism of PICUP require the tris(bipyridyl)Ru(II) complex, an electron acceptor, ammonium persulfate (APS), and reactive amino acid side chains.

[4] The reaction can proceed in the absence of an electron acceptor, but it will have a much lower efficiency, producing byproducts resulting from the excited Ru(Bpy)3 reacting with oxygen.

[2] In the PCR tube that the reaction takes place in, numerous unstable protein radicals come in contact with each other through simple diffusion and react both intra- and intermolecularly to achieve a more stable state.

The monomeric protein radicals are able to achieve a lower energy state through forming a covalent bond to produce a dimer and releasing a hydrogen atom.

Previous experiments have shown that for amyloid β-protein (Aβ), the peptide assumed to cause toxicity in Alzheimer's disease, the ratio of protein: Ru(Bpy)3: APS is 1:2:40.

[1] PICUP is extremely important when possible prevention and treatment procedures for these diseases are explored, as it is necessary to investigate the aggregation propensity of the respective amyloidogenic proteins.