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In plants and microorganisms, aspartate kinase (AK) catalyzes an initial commitment step of the aspartate family amino acid biosynthesis. Owing to various structural organizations, AKs from different species show tremendous diversity and complex allosteric controls. We report the crystal structure of AK from Pseudomonas aeruginosa (PaAK), a typical α2β2 hetero-tetrameric enzyme, in complex with inhibitory effectors. Distinctive features of PaAK are revealed by structural and biochemical analyses. Essentially, the open conformation of Lys-/Thr-bound PaAK structure clarifies the inhibitory mechanism of α2β2-type AK. Moreover, the various inhibitory effectors of PaAK have been identified and a general amino acid effector motif of AK family is described.

Background ScPrx1 is a yeast mitochondrial 1-Cys peroxiredoxins (Prx), a type of Prx enzyme which require thiol-containing reducing agents to resolve its peroxidatic cysteine. ScPrx1 plays important role in protection against oxidative stress. Mitochondrial thioredoxin ScTrx3 and glutathione have been reported to be the physiological electron donor for ScPrx1. However, the mechanism underlying their actions, especially the substrate recognition of ScPrx1 requires additional elucidation. METHODS: The structure of ScPrx1 was obtained through crystallization experiments. The oligomeric state of ScPrx1 was monitored by Blue-Native PAGE. Mutations were generated by the QuikChange PCR-based method. The ScPrx1 activity assay was carried out by measuring the change of 340 nm absorption of the NADPH oxidation. Results ScPrx1 exist as a homodimer in solution. The structure adopts a typical Prx-fold core which is preceded by an N-terminal β-hairpin and has a C-terminal extension. Mutations (Glu94Ala, Arg198Ala and Trp126) close to the active site could enhance the catalytic efficiency of ScPrx1 while His83Ala and mutations on α4-β6 region exhibited reduced activity. The biochemical data also show that the deletion or mutations on ScPrx1 C-terminal have 2–4.56 fold increased activity. Conclusion We inferred that conformational changes of ScPrx1 C-terminal segment were important for its reaction, and the α4-β6 loop regions around the ScPrx1 active sites were important for the catalytic function of ScPrx1. Collectively, these structural features provides a basis for understanding the diverse reductant species usage in different 1-Cys Prxs.

Glover’s linearization technique is revisited for solving the binary quadratic programming problem with a budget constraint (BBQP). When compared with the recent two linearizations for (BBQP), it not only provides a tighter relaxation at the root node, but also has a much better computational performance for globally solving (BBQP).

In plants and microorganisms, aspartate kinase (AK) catalyzes an initial commitment step of the aspartate family amino acid biosynthesis. Owing to various structural organizations, AKs from different species show tremendous diversity and complex allosteric controls. We report the crystal structure of AK from

A novel approach to the synthesis of 4-phenylethynylphthalic anhydride has been described. The target compound was synthesized by Pd/Cu catalyzed Sonogashira coupling reaction between phenylacetylene and 4-bromophthalic acid which was for the first time employed as start material, followed by dehydration of 4-phenylethynylphthalic acid. Compared with traditional synthetic routes, this method provides several advantages such as readily available raw materials, convenient manipulation and high yield. The products were characterized by IR, 1H NMR, 13C NMR, MS and elemental analysis, respectively.

A series of novel monomers of oligomers or polymers based on linear 1,4-phenylethynyl or 1,5-naphthylethynyl subunits, 1,4-bis(naphthalen-1-ylethynyl)benzene (8a) and its derivatives (8b–8i), has been synthesized and characterized. The UV absorption and fluorescence emission properties of these compounds were analyzed and discussed through the energy gap ( E ) between HOMO and LUMO orbitals, the orbital diagrams and the charge densities of related carbon atoms. It is evident from these results that the introduction of the electron-donating substituent (–OR) to the central phenylene ring of 8a and the introduction of electron-withdrawing substituent (–NO2) to the end of the conjugated system can efficiently improve its solubility, give rise to red-shift of maximum absorption and emission wavelength. But the introduction of electron-withdrawing substituent (–NO2) will lead dramatically decrease in fluorescence efficiency. The novel synthesized compounds 8b–8e have potential prospects as the monomers of olig...

Hydrolysis and bromination of phthalic anhydride in water gave a mixture of the monosodium salt of 4-bromo-phthalic acid. These were reacted with phenylacetylene under Sonogashira coupling reaction...

The title compound, C16H8O3, was synthesized by the Pd-coupling reaction of phenylacetylene with 4-bromophthalic anhydride. The phenyl and isobenzofurane rings are nearly coplanar, forming a dihedral angle of 6.70 (10)°. In the crystal structure, centrosymmetrically related molecules are linked into dimers by C—H...O hydrogen bonds.

Hydrolysis and bromination of phthalic anhydride in water gave a mixture of the monosodium salt of 4-bromo-phthalic acid. These were reacted with phenylacetylene under Sonogashira coupling reaction conditions in an aqueous medium. Acidification afforded 4-phenylethynylphthalic acid and then dehydration of this gave 4-phenylethynylphthalic anhydride in 76% overall yield. Compared with traditional synthetic methods, this method has the advantage of low cost, convenient manipulation and is environmentally friendly.

In the title compound, C18H20, the five-membered ring of the indane fragment adopts an envelope conformation, with the flap atom deviating by 0.399 (3) Å from the plane of the remaining four atoms. The dihedral angle between the phenyl ring and the indane benzene ring is 79.58 (7)°.