A paper on p. 58 stretches the possibilities for molecular evolution. Urabe and colleagues provide the first description of an approach—termed random elongation mutagenesis—in which peptide tails containing randomized sequences are appended to the C terminus of enzymes. Using catalase I enzyme from Bacillus stearothermophilus as a test system, they isolated 15 Escherichia coli clones from 58 clones that had higher thermostability than the wild type, a significant achievement given that catalase was considered to be "optimized" (see also p. 21).