Dipeptide-assisted growth of uniform gallium oxohydroxide spindles

The catalytic dipeptide His-Ser was used as an additive in mineralizing gallium ions to form GaOOH, a solid precursor of Ga2O3. This dipeptide was chosen to mimic the enzyme structure of silicatein, similar to the well-known catalytic triad of chymotrypsin. The dipeptide promoted formation of spindle-structured GaOOH under acidic conditions by behaving as a heterogeneous nucleation seed. In contrast, no well-defined, structured gallium species were produced in the absence of dipeptide. The catalytic function of the dipeptide was most pronounced at pH values in the range 3-5, which are lower than the pKa of imidazole in the His side chain. These results suggest that the catalytic role of dipeptide influences the gallium hydroxide conversion and growth. This study suggests that a designed peptide with active functionality can be further exploited to produce inorganic compounds with controlled nucleation and growth. (C) 2010 Elsevier B.V. All rights reserved.