Identification of six new photoactive yellow proteins--diversity and structure-function relationships in a bacterial blue light photoreceptor

Photoactive yellow proteins (PYP) are bacterial photoreceptors with a Per-Arnt-Sim (PAS) domain fold. We report the identification of six new PYPs, thus nearly doubling the size of this protein family. This extends the taxonomic diversity of PYP-containing bacteria from photosynthetic to nonphotosynthetic bacteria, from aquatic to soil-dwelling organisms, and from Proteobacteria to Salinibacter ruber from the phylum Bacteriodetes. The new PYPs greatly increase the sequence diversity of the PYP family, reducing the most prevalent pair-wise identity from 45% to 25%. Sequence alignments and analysis indicate that all 14 PYPs share a common structure with 13 highly conserved residues that form the chromophore binding pocket. Nevertheless, the functional properties of the PYPs vary greatly--the absorbance maximum extends from 432 to 465 nm, the pK(a) of the chromophore varies from pH 2.8 to 10.2, and the lifetime of the presumed PYP signaling state ranges from 1 ms to 1 h. Thus, the PYP family offers an excellent opportunity to investigate how functional properties are tuned over a wide range, while maintaining the same overall protein structural fold. We discuss the implications of these results for structure-function relationships in the PYP family.     

Redox reaction characteristics of ferritin-immobilized onto poly(l-lysine)-modified indium oxide electrodes

Ferritin-immobilized poly(l-lysine)-modified electrodes showed well-defined redox waves representing ferritin. Cathodic and anodic peak currents obtained from cyclic voltammograms were proportional to potential sweep rates. From charge flow values during oxidation or reduction reactions calculated by peak areas in cyclic voltammograms, and the surface coverage of ferritin, reacted iron atoms per ferritin molecule were calculated. Obtained numbers of reacted iron atoms were significantly smaller than expected values from iron atoms at ferrihydrite core surfaces of ferritin, which would be caused by the rate-determining ion flow through ion channels of ferritin to compensate for charges in the ferritin cavity. Anodic and cathodic peak potentials in cyclic voltammograms were significantly dependent on cationic species in the solution, though voltammetric shapes and peak currents were independent of cations. From the obtained results that structural changes in ferritin were not detected by fluorescent spectra, it is thought that the cationic dependence on ferritin redox peak potentials is caused by ferritin cores.     

Evaluation of interaction forces between profilin and designed peptide probes by atomic force microscopy

We evaluated the binding affinity of peptide probes for profilin (protein) using force curve measurement techniques and atomic force microscopy (AFM). The peptide probes designed and synthesized for this investigation were H-A3GP5GP5GP5G-OH (1), H-A3GP5G-OH (2), H-A3G7-OH (3), and H-A3G-OH (4). Each peptide probe was immobilized on a cantilever tip, and the interaction force to profilin, immobilized on a mica substrate, was examined by force curve measurements. The retraction forces obtained showed a sequence-dependent affinity of the peptide probe for profilin. The retraction force for peptide probe 1 was the largest of the four probes examined, and it confirmed that peptide probe 1 has high affinity for profilin. The single molecular retraction force between peptide probe 1 and profilin was estimated to be 96 pN, as determined by Gaussian fitting to the histogram of the retraction forces.     

Complex formation between cationic beta-1,3-glucan and hetero-sequence oligodeoxynucleotide and its delivery into macrophage-like cells to induce cytokine secretion

A cationic polysaccharide bearing a beta-1,3-glucan main-chain structure (CUR-N(+)) forms a complex with a hetero-sequence oligonucleotide, that is, a CpG ODN, and facilitates the transportation of the resultant complex into a murine macrophage-like cell J774.A1, which induces an efficient secretion of a cytokine (IL-12) as compared with that induced by conventional carriers such as poly(ethyleneimine) (PEI) and poly(L-lysine) (PLL).     

Cerium complexes of cyclodextrin dimers as efficient catalysts for luminol chemiluminescence reactions

The chemiluminescence of a luminol-H(2)O(2) system is found to be remarkably enhanced by the Ce(IV) complexes of EDTA-bridged cyclodextrin dimers. The dimers were proved to work much more efficiently than the corresponding monomer. The cavity shape of cyclodextrin moieties and their cooperation displayed an important role in amplifying the chemiluminescence. Further modification of either the cyclodextrin rims or the EDTA linker altered significantly the catalytic abilities of the cyclodextrin dimers, and the examination of the effect of substituents on the chemiluminescence outputs suggested that the proximity between the cyclodextrin cavity and the metallic center might account for the amelioration of the chemiluminescence output.     

Palladium-catalysed regioselective addition reaction of ethyl phenylphosphinate with terminal acetylenes: ligand- and solvent-dependent regioselectivity

Palladium-1,2-bis(diphenylphosphino)ethane complex catalyses regioselective Markovnikov addition of ethyl phenylphosphinate to terminal alkynes in toluene, while the use of tri-tert-butylphosphine as the ligand or ethanol as the solvent leads to regioselectivity reversal.     

Linear metal-metal-bonded tetranuclear M-Mo-Mo-M complexes (M = Ir and Rh): oxidative metal-metal bond formation in a tetrametallic system and 1,4-addition reaction of alkyl halides

Reaction of Mo2(pyphos)4 (1) with [MCl(CO)2]2 (M = Ir and Rh) afforded linear tetranuclear complexes of a formula Mo2M2(CO)2(Cl)2(pyphos)4 (2, M = Ir; 3, M = Rh). X-ray diffraction studies confirmed that two "MCl(CO)" fragments are introduced into both axial sites of the Mo2 core in 1 and coordinated by two PPh2 groups in a trans fashion, thereby forming a square-planar geometry around each M(I) metal. Treatment of 2 and 3 with an excess amount of tBuNC and XylNC induced dissociation of the carbonyl and chloride ligands to yield the corresponding dicationic complexes [Mo2M2(pyphos)4(tBuNC)4](Cl)2 (5a, M = Ir; 6a, M = Rh) and [Mo2M2(pyphos)4(XylNC)4](Cl)2 (7, M = Ir; 8, M = Rh). Their molecular structures were characterized by spectroscopic data as well as X-ray diffraction studies of BPh4 derivatives [Mo2M2(pyphos)4(tBuNC)4](BPh4)2 (5b, M = Ir; 6c, M = Rh), which confirmed that there is no direct sigma-bonding interaction between the M(I) atom and the Mo2 core. The M(I) atom in 5 and 6 can be oxidized by either 2 equiv of [Cp2Fe][PF6] or an equimolar amount of I2 to afford Mo(II)2M(II)2 complexes, [Mo2M2(X)2(tBuNC)4(pyphos)4]2+ in which two Mo-M(II) single bonds are formed and the bond order of the Mo-Mo moiety has been decreased to three. The Ir(I) complex 5a reacted not only with methyl iodide but also with dichloromethane to afford the 1,4-oxidative addition products [Mo2Ir2(CH3)(I)(tBuNC)4(pyphos)4](Cl)2 (13) and [Mo2Ir2(CH2Cl)(Cl)(tBuNC)4(pyphos)4](Cl)2 (15), respectively, although the corresponding reactions using the Rh(I) analogue 6 did not proceed. Kinetic analysis of the reaction with CH3I suggested that the 1,4-oxidative addition to the Ir(I) complex occurs in an SN2 reaction mechanism.     

An efficient oxidative lactonization of 1,4-diols catalyzed by Cp*Ru(PN) complexes

[reaction: see text] An efficient oxidative lactonization of 1,4-diols in acetone is accomplished by the well-defined ruthenium catalyst, whose bifunctional nature underlies the high efficiency as well as unique chemo- and regioselectivity of the reaction which provides a rapid access to gamma-butyrolactones including flavor lactones hinokinin, and muricatacin.