Experimental and theoretical investigations of circular dichroism of donor-acceptor 1,1'-binaphthyls: influence of substitution on the coupling amplitude and cotton effect of the charge-transfer band

The electronic circular dichroism (CD) spectra of donor-acceptor binaphthyls were investigated experimentally and theoretically. The enantiomerically pure forms of 1-(2-methoxy-1-naphthyl)- and 1-(2,3-dimethoxy-1-naphthyl)-2-methylisoquinolinium tetrafluoroborates (DA and D'A) were prepared, and their UV-vis and CD spectra were compared. The donor-acceptor interaction was apparent from the absorption at longer wavelengths, whereas its strength was not very different from each other. In addition, very similar structures were obtained for the two aromatic planes in DA and D'A when the geometry was optimized by the density functional theory. The additional methoxy group in the latter spices scarcely disturbed the UV-vis spectrum but significantly affected the CD spectrum. Thus, the observed CD spectra were considerably different from each other, especially in the (1) B(b) band couplet, where the amplitude was reduced to almost one-fourth in D'A. The theoretical investigations led to the following conclusions: (1) The potential curve associated with the central C-C dihedral angle of 1,1'-binaphthyl is fairly flat at the bottom for both DA and D'A and freely rotating at an ambient temperature. The potential curve of D'A is, however, significantly different from that of DA, in which the curve is much steeper and biased to the s-cis side. As the observed CD spectrum is an ensemble of conformers of various dihedral angles, such difference in potential certainly affects the overall spectrum; (2) The additional methoxy group introduced at the 3-position effectively altered the CD spectral pattern, which was theoretically supported by the calculation at the RI-CC2/TZVPP level; (3) Consequently, the classical coupled oscillator theory, in which the angle between the transition dipole moments of two aromatic planes is solely considered, is not applicable to the quantitative evaluation of the chiroptical properties of 1,1'-binaphthyls; rather, the quantum chemical approach is preferred, permitting a direct comparison with the experiment.     

Restriction and modification of SP10 phage by BsuM of Bacillus subtilis Marburg

Bacillus subtilis Marburg has only one intrinsic restriction and modification system BsuM that recognizes the CTCGAG (XhoI site) sequence. It consists of two operons, BsuMM operon for two cytosine DNA methyltransferases, and BsuMR operon for a restriction nuclease and two associated proteins of unknown function. In this communication, we analyzed the BsuM system by utilizing phage SP10 that possesses more than twenty BsuM target sequences on the phage genome. SP10 phages grown in the restriction and modification-deficient strain could not make plaques on the restriction-proficient BsuMR(+) indicator strain. An enforced expression of the wild type BsuMM operon in the BsuMR(+) indicator strain, however, allowed more than thousand times more plaques. DNA extracted from SP10 phages, thus, propagated became more but not completely refractory to XhoI digestion in vitro. Thus, the SP10 phage genome DNA is able to be nearly full-methylated but some BsuM sites are considered to be unmethylated.     

Structure-based functional identification of a novel heme-binding protein from <Emphasis Type="Italic">Thermus thermophilus</Emphasis> HB8

The TT1485 gene from Thermus thermophilus HB8 encodes a hypothetical protein of unknown function with about 20 sequence homologs of bacterial or archaeal origin. Together they form a family of uncharacterized proteins, the cluster of orthologous group COG3253. Using a combination of amino acid sequence analysis, three-dimensional structural studies and biochemical assays, we identified TT1485 as a novel heme-binding protein. The crystal structure reveals that this protein is a pentamer and each monomer exhibits a β-barrel fold. TT1485 is structurally similar to muconolactone isomerase, but this provided no functional clues. Amino acid sequence analysis revealed remote homology to a heme enzyme, chlorite dismutase. Strikingly, amino acid residues that are highly conserved in the homologous hypothetical proteins and chlorite dismutase cluster around a deep cavity on the surface of each monomer. Molecular modeling shows that the cavity can accommodate a heme group with a strictly conserved His as a heme ligand. TT1485 reconstituted with iron protoporphyrin IX chloride gave a low chlorite dismutase activity, indicating that TT1485 catalyzes a reaction other than chlorite degradation. The presence of a possible Fe–His–Asp triad in the heme proximal site suggests that TT1485 functions as a novel heme peroxidase to detoxify hydrogen peroxide within the cell.     

Prevalence of abnormal findings on brain magnetic resonance (MR) examinations in adult participants of brain docking

Background  

To determine the prevalence of abnormal findings on brain magnetic resonance (MR) examinations in adult participants of brain docking in order to assess its usefulness.     

Characterization of recombinant amyloidogenic chicken cystatin mutant I66Q expressed in yeast

Amyloidogenic chicken cystatin mutant I66Q (cC I66Q) was successfully secreted by yeasts Pichia pastoris and Saccharomyces cerevisiae. The soluble monomer and dimer forms of amyloidogenic cC I66Q were found in the culture medium, while large amounts of insoluble aggregate and polymeric form cC I66Q besides the monomer and dimer forms were secreted into the culture medium. The amyloidogenic cC I66Q showed a comparable circular dichroism spectrum to that of the wild cystatin, and the monomer form exhibited a similar level of inhibitory activity toward papain, but the dimmer form did not. During storage of amyloidogenic cC I66Q under physiological and acidic conditions, typical binding with Congo red and thioflavin T, and the formation of amyloid fibrils were observed, whereas the characteristic of similar amyloidosis was hardly detected for the wild recombinant cystatin.     

Sugar-binding properties of VIP36, an intracellular animal lectin operating as a cargo receptor

The vesicular integral protein of 36 kDa (VIP36) is an intracellular animal lectin that acts as a putative cargo receptor, which recycles between the Golgi and the endoplasmic reticulum. Although it is known that VIP36 interacts with glycoproteins carrying high mannose-type oligosaccharides, detailed analyses of the sugar-binding specificity that discriminates isomeric oligosaccharide structures have not yet been performed. In the present study, we have analyzed, using the frontal affinity chromatography (FAC) method, the sugar-binding properties of a recombinant carbohydrate recognition domain of VIP36 (VIP36-CRD). For this purpose, a pyridylaminated sugar library, consisting of 21 kinds of oligosaccharides, including isomeric structures, was prepared and subjected to FAC analyses. The FAC data have shown that glucosylation and trimming of the D1 mannosyl branch interfere with the binding of VIP36-CRD. VIP36-CRD exhibits a bell-shaped pH dependence of sugar binding with an optimal pH value of approximately 6.5. By inspection of the specificity and optimal pH value of the sugar binding of VIP36 and its subcellular localization, together with the organellar pH, we suggest that VIP36 binds glycoproteins that retain the intact D1 mannosyl branch in the cis-Golgi network and recycles to the endoplasmic reticulum where, due to higher pH, it releases its cargos, thereby contributing to the quality control of glycoproteins.     

Antiangiogenic photodynamic therapy (PDT) by using long-circulating liposomes modified with peptide specific to angiogenic vessels

For the improvement of therapeutic efficacy in photodynamic therapy (PDT) by using a photosensitizer, benzoporphyrin derivative monoacid ring A (BPD-MA), we previously prepared polyethylene glycol (PEG)-modified liposomes encapsulating BPD-MA (PEG-Lip BPD-MA). PEGylation of liposomes enhanced the accumulation of BPD-MA in tumor tissue at 3 h after injection of it into Meth-A-sarcoma-bearing mice, but, unexpectedly, decreased the suitability of the drug for PDT when laser irradiation was performed at 3 h after the injection of the liposomal photosensitizer. To improve the bioavailability of PEG-Lip BPD-MA, we endowed the liposomes with active-targeting characteristics by using Ala-Pro-Arg-Pro-Gly (APRPG) pentapeptide, which had earlier been isolated as a peptide specific to angiogenic endothelial cells. APRPG-PEG-modified liposomal BPD-MA (APRPG-PEG-Lip BPD-MA) accumulated in tumor tissue similarly as PEG-Lip BPD-MA and to an approx. 4-fold higher degree than BPD-MA delivered with non-modified liposomes at 3 h after the injection of the drugs into tumor-bearing mice. On the contrary, unlike the treatment with PEG-Lip BPD-MA, APRPG-PEG-Lip BPD-MA treatment strongly suppressed tumor growth after laser irradiation at 3 h after injection. Finally, we observed vasculature damage in the dorsal air sac angiogenesis model by APRPG-PEG-Lip BPD-MA-mediated PDT. The present results suggest that antiangiogenic PDT is an efficient modality for tumor treatment and that tumor neovessel-targeted, long-circulating liposomes are a useful carrier for delivering photosensitizer to angiogenic endothelial cells.