The chemokine receptor CXCR7 is an attractive target for a variety of diseases. While several small-molecule modulators of CXCR7 have been reported, peptidic macrocycles may provide advantages in terms of potency, selectivity, and reduced off-target activity. We produced a series of peptidic macrocycles that incorporate an N-linked peptoid functionality where the peptoid group enabled us to explore side-chain diversity well beyond that of natural amino acids. At the same time, theoretical calculations and experimental assays were used to track and reduce the polarity while closely monitoring the physicochemical properties. This strategy led to the discovery of macrocyclic peptide-peptoid hybrids with high CXCR7 binding affinities (K < 100 nM) and measurable passive permeability (P > 5 × 10 cm/s). Moreover, bioactive peptide 25 (K = 9 nM) achieved oral bioavailability of 18% in rats, which was commensurate with the observed plasma clearance values upon intravenous administration.

The isolation of sequences flanking integrated transposable elements is an important step in gene tagging strategies. We have demonstrated that sequences flanking transposons integrated into complex genomes can be simply and rapidly obtained using the polymerase chain reaction. Amplification of such sequences was established in a model system, a transgenic tobacco plant carrying a single Ac element, and successfully applied to the cloning of a specific Spm element from a maize line carrying multiple Spm hybridizing sequences. The described utilization of methylation sensitive restriction enzymes (including those with degenerate recognition sequences) in the generation of templates for amplification will simplify the cloning and mapping of genomic sequences adjacent to transposable elements.

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Using our recently reported method of electroporation to transform Bacillus thuringiensis [Bone & Ellar (1989) FEMS Microbiol. Lett. 58, 171-178], cloned B. thuringiensis entomocidal delta-endotoxin genes have been introduced into several native B. thuringiensis strains. In many cases the resulting transformants expressed both their native toxins and the cloned toxin, producing strains with broader toxicity spectra. The introduction of the var. tenebrionis toxin gene into B. thuringiensis var. israelensis resulted in a strain with activity against Pieris brassicae (cabbage white butterfly), an activity which neither parent strain possesses. We discuss further the possibility of synergism and also the problems associated with introducing cloned DNA by this method.

The possible presence of protein δ‐endotoxins with homology to a cloned mosquitocidal Bacillus thuringiensis var. israelensisδ‐endotoxin was investigated in two other mosquitocidal B. thuringiensis strains. Antiserum raised against the var. israelensis 27‐kDa toxic polypeptide cross‐reacted strongly with a 27‐kDa crystal polypeptide of var. PG14 (serotype 8a:8b, a serotype more usually associated only with lepidopteran toxicity). In addition hybridisation studies using a DNA probe derived from the cloned var. israelensis 27‐kDa δ‐endotoxin gene located a homologous region on a 72–74‐MDa plasmid of PG14. A less toxic strain, var. Kyushuensis, showed neither immunological cross‐reaction with the antiserum nor DNA hybridization with the probe.