Phosphine is a small redox-active gas that is used to protect global grain reserves, which are threatened by the emergence of phosphine resistance in pest insects. We find that polymorphisms responsible for genetic resistance cluster around the redox-active catalytic disulfide or the dimerization interface of dihydrolipoamide dehydrogenase (DLD) in insects (Rhyzopertha dominica and Tribolium castaneum) and nematodes (Caenorhabditis elegans). DLD is a core metabolic enzyme representing a new class of resistance factor for a redox-active metabolic toxin. It participates in four key steps of core metabolism, and metabolite profiles indicate that phosphine exposure in mutant and wild-type animals affects these steps differently. Mutation of DLD in C. elegans increases arsenite sensitivity. This specific vulnerability may be exploited to control phosphine-resistant insects and safeguard food security.

The supramolecular interaction of curcumin and beta-cyclodextrin (beta-CD) has been studied by spectrophotometry. The mechanism of the inclusion was studied and discussed based on the variations of pK(a), absorption intensity, and infrared spectrograms. The results show that beta-CD reacts with curcumin to form a 2:1 host-guest complex with an apparent formation constant of 5.53 x 10(5) mol(-2) x L2. Based on the enhancement of the absorbance of curcumin produced through complex formation, a spectrophotometric method for the determination of curcumin in bulk aqueous solution in the presence of beta-CD was developed. The linear relationship between the absorbance and curcumin concentration was obtained in the range of 0-15 microg/mL, with a correlation coefficient (r) of 0.9991. The detection limit was 0.076 microg/mL. The proposed method was used to determine the curcumin in curry and mustard with satisfactory results.

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Viscoelastic properties of cheeses with and without 0.2% or 0.5% (w/w) lecithin were studied using oscillatory dynamic experiments and creep tests. Elastic and loss moduli of reduced-fat cheese with lecithin were greater (p Ͻ 0.01) than reduced-fat cheese without lecithin, but less (p Ͻ 0.01) than these values for full-fat cheese. In creep/recovery tests, the residual strain of full-fat cheese, reduced-fat cheese with 0.5% or 0.2% lecithin, and reduced-fat cheese without lecithin were 7.8, 7.9, 8.1, and 15.4%, respectively. There was good agreement in terms of compliance behavior of the four types of cheese between experimental data and prediction by the generalized Kelvin model with six elements.

The direction of electron flow through nitrogenase is generally believed to be from the Fe protein to the Pclusters to the FeMo cofactor and then to substrate. In order to examine oxidation states of the P-clusters that might be involved in this pathway, we have constructed a form of the MoFe protein that contains a species called the MoFe cluster Molybdenum nitrogenase is composed of two separate proteins whose complete structures have recently been determined by x-ray crystallography (1-7). The smaller of the two, designated the iron protein (Fe protein), is a dimer of two identical subunits encoded by the nifH gene (1, 8). It contains two binding sites for MgATP and has a single [4Fe-4S] 2ϩ/ϩ cluster. The larger of the two component proteins is designated the molybdenum-iron protein (MoFe protein) and is an a 2 ␤ 2 tetramer with the ␣ and ␤ subunits encoded by the nifD and nifK genes, respectively. It has two types of metal centers, the P-clusters (two per tetramer) that each contain 8Fe and 8S 2Ϫ atoms in the form of bridged [4Fe-4S] clusters and, the iron molybdenum cofactors (FeMo cofactor) (two per tetramer) that have the composition Mo:Fe 7