FIGURE 2.

Compound 1 protects nanogold from aggregation better than compound 3. (A, B) Representative photographs of nanogold (25-nm, ∼1 U/ml at A₅₂₀ nm) mixed with the indicated amount of compound 3 or 1 before and after the addition of sodium chloride (5% final). Marked color change from red to gray is an indication of nanoparticle aggregation. (C) UV-Vis spectra of gold nanoparticles uncoated (dashed line) or coated (solid red line) with the indicated amounts of compound 1 and human serum albumin (HSA, added as a second stabilizer). (D) Effect of sodium chloride (5% final concentration) on aliquots of the products shown in (C). Note that all products display similar colors, suggesting good nanoparticle stability.