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Odorant binding proteins (OBPs) transport hydrophobic odor molecules across the sensillar lymph to trigger a neuronal response. Herein, the Minus-C OBP (DhelOBP21) was characterized from Dastarcus helophoroides, the most important natural parasitic enemy insect that targets Monochamus alternatus. Homology modeling and molecular docking were conducted on the interaction between DhelOBP21 and 17 volatile molecules (including volatiles from pine bark, the larva of M. alternatus, and the faeces of the larva). The predicted three-dimensional structure showed only two disulfide bridges and a hydrophobic binding cavity with a short C-terminus. Ligand-binding experiments using N-phenylnaphthylamine (1-NPN) as a fluorescent probe showed that DhelOBP21 exhibited better binding affinities against those ligands with a molecular volume between 100 and 125 ų compared with ligands with a molecular volume between 160 and 185 ų. Molecules that are too big or too small are not conducive for binding. We mutated the amino acid residues of the binding cavity to increase either hydrophobicity or hydrophilia. Ligand-binding experiments and cyber molecular docking assays indicated that hydrophobic interactions are more significant than hydrogen-bonding interactions. Although hydrogen-bond interactions could be predicted for some binding complexes, the hydrophobic interactions had more influence on binding following hydrophobic changes that affected the cavity. The orientation of ligands affects binding by influencing hydrophobic interactions. The binding process is controlled by multiple factors. This study provides a basis to explore the ligand-binding mechanisms of Minus-C OBP.

The commercially readily available alkyl aluminums, such as AlMe 3 , AlEt 3 , and AlEt 2 Cl, can serve as excellent catalyst precursors for the catalytic addition of amines to carbodiimides, yielding quantitatively their corresponding trisubstituted guanidines. Aromatic C-X (X ) F, Cl, Br, and I) bonds, nitro NO 2 , and terminal alkyne units can survive the reaction conditions. An aluminum guanidinate species has been characterized by single-crystal X-ray structural analysis and has been confirmed to be a true catalyst species.

A diode-end-pumped dual-wavelength mode-locked laser based on Nd:LuYSiO5 crystal is demonstrated. With a SESAM, simultaneous mode locking at the 1075.8 nm and 1078.1 nm is achieved and the dual-wavelength mode locked pulses have a pulse width of 8.9 ps. Due to frequency beating, ultrahigh repetition rate ultrafast pulses with 997 fs pulse width and 0.59 THz repetition rate are further formed. Under 12.7 W absorbed pump power 1.7 W mode-locked output power was obtained, the slope efficiency of the mode locked laser was 24.3%.

Odorant binding proteins (OBPs) transport hydrophobic odorants from the environment to odorant receptors and play an important role in specific recognition of volatiles. Here, we expressed and purified a minus-C OBP, BhorOBPm2, from Batocera horsfieldi, a major pest of Popolus, to determine its binding characteristics with 58 candidate volatiles using a fluorescence competition-binding assay. We showed that BhorOBPm2 exhibited high binding affinity with chain volatiles and that ligands were selected based on chain length. In order to elucidate the binding mechanism, homology modeling and molecular-docking experiments were performed to investigate interactions between BhorOBPm2 and volatiles. The predicted structure with only two disulfide bonds showed one continuous channel for ligand binding, similar to classic OBPs AgamOBP1 and CquiOBP1. Unexpectedly, we observed a larger binding pocket for BhorOBPm2 and broader specificity for ligands than classic OBPs due to the expansive flexibility of BhorOBPm2 resulting from a lack of disulfide bonds. These findings suggested that BhorOBPm2 might present an intermediate structure in the evolution of OBPs. Furthermore, we designed two mutant proteins to simulate and verify functions of the C-terminal region. The changes in binding affinity observed here indicated a novel action differing from that of the “lid” described in previous studies.

In light of reverse chemical ecology, the fluorescence competitive binding assays of functional odorant binding proteins (OBPs) is a recent advanced approach for screening behaviorally active compounds of insects. Previous research on Dastareus helophoroides identified a minus-C OBP, DhelOBP21, which preferably binds to several ligands. In this study, only (+)-β-pinene proved attractive to unmated adult beetles. To obtain a more in-depth explanation of the lack of behavioral activity of other ligands we selected compounds with high (camphor) and low (β-caryophyllene) binding affinities. The structural transformation of OBPs was investigated using well-established approaches for studying binding processes, such as fluorescent quenching assays, circular dichroism, and molecular dynamics. The dynamic binding process revealed that the flexibility of DhelOBP21 seems conducive to binding specific ligands, as opposed to broad substrate binding. The compound (+)-β-pinene and DhelOBP21 formed a stable complex through a secondary structural transformation of DhelOBP21, in which its amino-terminus transformed from random coil to an α-helix to cover the binding pocket. On the other hand, camphor could not efficiently induce a stable structural transformation, and its high binding affinities were due to strong hydrogen-bonding, compromising the structure of the protein. The other compound, β-caryophyllene, only collided with DhelOBP21 and could not be positioned in the binding pocket. Studying structural transformation of these proteins through examining the dynamic binding process rather than using approaches that just measure binding affinities such as fluorescence competitive binding assays can provide a more efficient and reliable approach for screening behaviorally active compounds.

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A new CaF2-YAG:Ce phosphor ceramic was fabricated at 700 °C, which shows excellent luminescence performance, and thus it is suitable for use in high-power WLEDs.