The reaction was followed spectrophotometrically by observing the appearance of purple color as a function of time at 570 nm (Fig. 1) using a single beam spectrophotometer (SHIMADZU-model UV mini 1240, Japan). A three-necked reaction vessel (fitted with double-walled condenser to prevent evaporation) containing Gly-Tyr solution, buffer, and CTAB (when required) was kept immersed in an oil-bath thermostated at the desired temperature.