A dendron-like nanostructure of silver was grown in solution using a water-soluble tetrapeptide Tyr-Aib-Tyr- Val( Aib, alpha-amino isobutyric acid), silver nitrate, and methanol. These structures are composed of silver nanoparticles having a bimodal size distribution with the median diameters around 2.0 and 19.5 nm, respectively. The dendron-like growth is ascribed to the effect of the local electric field generated by the dipoles associated with the peptide molecules. The optical absorption spectra have been analyzed by Mie scattering theory, which shows that there is a metal-nonmetal transition in silver particles having diameters less than similar to 2.0 nm.