The adsorption of bovine serum albumin BSA on gold nanoparticles is influenced by the pH of the solution. BSA is a globular protein with a molecular weight of approximately 66 kDa and contains both acidic and basic amino acid residues. The isoelectric point pI of BSA is around 4.7, which is the pH at which the protein carries no net charge.The effect of pH on the adsorption of BSA on gold nanoparticles can be understood by considering the electrostatic interactions between the protein and the nanoparticles. Gold nanoparticles are typically negatively charged due to the presence of stabilizing agents or the adsorption of ions on their surface.1. At pH values below the pI of BSA pH < 4.7 , the protein carries a net positive charge. In this case, the electrostatic attraction between the positively charged BSA and the negatively charged gold nanoparticles will promote adsorption of the protein on the nanoparticle surface.2. At pH values above the pI of BSA pH > 4.7 , the protein carries a net negative charge. In this case, the electrostatic repulsion between the negatively charged BSA and the negatively charged gold nanoparticles will hinder the adsorption of the protein on the nanoparticle surface.3. At pH values close to the pI of BSA pH 4.7 , the protein carries no net charge. In this case, the electrostatic interactions between BSA and gold nanoparticles are minimized, and other factors such as hydrophobic interactions, hydrogen bonding, and van der Waals forces may play a more significant role in the adsorption process.In summary, the adsorption of BSA on gold nanoparticles is affected by the pH of the solution, with higher adsorption occurring at pH values below the pI of BSA due to favorable electrostatic interactions. However, it is important to note that other factors, such as protein concentration, temperature, and ionic strength, can also influence the adsorption process.