When copper is in excess, it can cause oxidative stress and damage to cells, which increases the demand for glutathione to neutralize the free radicals produced
Peptide Therapy Cellular regeneration from the inside out
Arsova B, Hoja U, Wimmelbacher M, Greiner E, stn , Melzer M, Petersen K, Lein W, Bornke F (2010) Plastidial thioredoxin z interacts with two fructokinase-like proteins in a thiol-dependent manner: evidence for an essential role in chloroplast development in Arabidopsis and Nicotiana benthamiana
If your diet isnt providing you with enough vitamin B12 and you choose to supplement, consider opting for a B-complex or multivitamin formulated with methyl- or adenosylcobalamin
These are thin enough that most people describe the injection as nearly painless
Campo, G