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Two identical polyamine peptide conjugate libraries were screened against the parasitic enzyme trypanothione reductase. One of these libraries was in a solution format, while the other was resin-based and was used in two resin-based screens (a diminution assay and a direct bead screening). Potent inhibitors (100 nM) of trypanothione reductase were identified both in the solution screen and in the resin-based screens when using the PEGA resin of Meldal. Resin screening of both types failed to work with TentaGel resin. Importantly there was excellent agreement between the solution and resin-based assays, suggesting both methods are reliable for the screening of combinatorial libraries.

Highly cross-linked azlactone functional supports were prepared by dispersion polymerization of 2-vinyl-4,4-dimethylazlactone (VDM), 2-hydroxyethyl methacrylate (HEMA), and trimethylolpropane trimethacrylate (TMPTMA). The supports were recovered in high yield and possessed high surface areas. Individual particles, which ranged from 10 to 300 μm in diameter, were irregularly shaped and comprised of filamentous strands. Support polarity was tailored through increases in the HEMA level in the polymer formulations and was quantified by a lipophilicity index derived from solvent partition data collected on the constituent monomers. Support reactivity, as determined by azlactone aminolysis and measured by IR, was found to increase linearly with increasing support polarity. This effect was shown to be independent of the support cross-link density.

We have developed a system for temperature-inducible killing of specific cells in the fruitfly Drosophila melanogaster. The system overcomes many of the limitations of existing cell ablation methods and is in principle applicable to any non-homeothermic eukaryote. Temperature-sensitive and cold-sensitive mutations in the ricin toxin A chain (RTA) of castor bean were generated in yeast. One cold-sensitive mutation, RAcs2, produced temperature-dependent ablation of eye cells in Drosophila when expressed under control of the eye-specific sev enhancer. At 29 degrees C, cell death was observed within 7 hours in the developing eye and no obvious toxic effects were observed elsewhere; at 18 degrees C, extremely low toxicity was observed. DNA sequencing of RAcs2 revealed a single amino acid substitution in the RTA active site cleft.