Use of Gold Nanoparticles as Additives in Protein Crystallization

Gold nanoparticles (AuNPs) exhibit unique properties that have made them a very attractive material for application in biological assays. Given the potentially interesting interactions between AuNPs and biological macromolecules, we investigated AuNPs-induced protein crystal growth. Differently functionalized AuNPs were tested as additives in cocrystallization studies with model proteins (hen egg white lysozyme (HEWL), ribonuclease A (RNase A), and proteinase K) as well as with case studies where there were problems in obtaining well-diffracting crystals. Trials were performed considering different crystallization drawbacks, from total absence of crystals to improvement of crystal morphology, size, twinning, and number of crystals per drop. Improvement of some of these factors was observed in the cases of HEWL, RNase A, phenylalanine hydroxylase (PAH), myoglobin, native aldehyde oxidase (AOH), and human albumin. In these proteins, the presence of the AuNPs promoted an increase in the size and/or better cr...