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The larvicidal activity of a number of 1‐(substituted benzoyl)‐2‐benzoyl–1 ‐ten‐butylhydrazines against the rice stem borer (Chilo suppressalis Walk.) was measured. Variations in the activity were examined quantitatively using physico‐chemical substituent and molecular parameters and regression analysis. The results indicated that the molecular hydrophobicity and the electron‐withdrawing inductive/ field effect of ontho substituents are favourable to larvicidal activity. The bulkiness of substituents at the meta and para positions was unfavourable to activity, substitution at the para position being more unfavourable than that at the meta position in terms of van der Waals' volume. The 2,3–, 2,5‐ and 2,6‐disubstitution patterns were also unfavourable to activity. Reductions in larvicidal activity caused by the 2,6‐,‐ 2,3,5‐ and 2,3,4,5‐substitutions were greater than those induced by the 2,3‐ and 2,5‐disubstitutions. When the sum of contributions from favourable effects is greater than that from unfavourable effects, the larvicidal activity is expected to be superior to that of the unsubstituted compound.

The binding activity of imidacloprid and related compounds to nicotinic acetylcholine receptors (nAChR) of house flies was measured by use of radioactive α‐bungarotoxin as a ligand. Variations in the activity were examined three‐dimensionally using comparative molecular field analysis (CoMFA). The CoMFA results suggest that one conformer among the four stable ones is active and provide support for one of the proposed binding models for this class of compound, in which the nitrogen atom of the pyridine ring and the nitrogen atom at the 1‐position of the imidazolidine ring interact with the hydrogen‐donating and electron‐rich sites of nAChR, respectively. The CoMFA field map showed that the nitroimino moiety and a portion of the imidazolidine ring were mainly surrounded by a sterically and electrostatically sensitive region of nAChR. © 1998 Society of Chemical Industry

The metabolism of polyethylene glycol (PEG) was investigated with a synergistic, mixed culture of Flavobacterium and Pseudomonas species, which are individually unable to utilize PEGs. The PEG dehydrogenase linked with 2,6dichlorophenolindophenol was found in the particulate fraction of sonic extracts and catalyzed the formation of a 2,4-dinitrophenylhydrazine-positive compound, possibly an aldehyde. The enzyme has a wide substrate specificity towards PEGs: from diethylene glycol to PEG 20,000. Km values for tetraethylene glycol (TEG), PEG 400, and PEG 6,000 were 11, 1.7, and 15 mM, respectively. The metabolic products formed from TEG by intact cells were isolated and identified by combined gas chromatography-mass spectrometry as triethylene glycol and TEGmonocarboxylic acid plus small amounts of TEG-dicarboxylic acid, diethylene glycol, and ethylene glycol. From these enzymatic and analytical data, the following metabolic pathway was proposed for PEG: HO(CH2CH20)nCH2CH20H-+ HO(CH2CH20)nCH2CHO-* HO(CH2CH20)nCH2COOH-HO(CH2CH2-O),-0CH2CH20H.