A novel one-pot pseudo five-component isocyanide-based reaction: synthesis of 2,6-bis(alkylamino)-benzofuro[5,6-b]furan-4,8-dione derivatives

A novel one-pot pseudo five-component reaction of isocyanides with 2,5-dihydroxycyclohexa-2,5-diene-1,4-dione and various aliphatic and aromatic aldehydes in ethanol at room temperature has been studied. 2,6-Bis(alkylamino)-benzofuro[5,6-b]furan-4,8-dione derivatives were isolated as the products in good yields after 24 h.     

Electrochemical study of the thionine dye incorporated into ZSM-5 and HZSM-5 zeolites

The electrochemical properties of thionine dye adsorbed into ZSM-5 and HZSM-5 zeolites (TH/ZSM-5, TH/HZSM-5) are studied in 0.5 M KCl solution. The dye is strongly retained and not easily leached from the zeolites matrix. The samples are incorporated into the carbon paste electrode (TH/ZSM-5/P, TH/HZSM-5/P) for cyclic voltammetric measurements. The redox reactions of thionine incorporated into ZSM-5 zeolite contain a quasi-reversible, two-electron one proton in the pH range 1 to 10, but thionine-loaded HZSM-5 zeolite undergoes a quasi-reversible two-electron two-protons redox reaction under acidic conditions and a one proton two-electron redox reaction takes place under basic conditions. The separation of the anodic and cathodic potentials (E _p) is high in thionine-loaded zeolites (>100) with respect to the solution of thionine (E _p = 34 for ZSM-5/P and 36 mV for HZSM-5/P), indicating that there are strong interaction between thionine molecules and the zeolites. The midpoint potentials (E _m) for TH/ZSM-5/P and TH/HZSM-5/P are −0.203 and −0.381 V, respectively. However, the midpoint potentials for the solution of thionine for the electrode system of ZSM-5/P and HZSM-5/P are −0.335 and −0.407 V, respectively. Thus, thionine dye molecules incorporated into the zeolites can be reduced more easily with respect to solution of thionine. In various electrolyte solutions, the midpoint potentials remains constant, but the midpoint potential of the thionine-zeolite electrodes depends on the solution pH. Influence of the pH of the solution on the midpoint potential of an immobilized dye reveals that thionine molecules are accessible to protons. This property is ascribed to the formation of mesopores in the structure of our zeolites suffering from a calcination step. Published in Russian in Elektrokhimiya, 2007, Vol. 43, No. 7, pp. 794–800. The text was submitted by the authors in English     

Minimization and optimization of designed beta-hairpin folds

Minimized beta hairpins have provided additional data on the geometric preferences of Trp interactions in TW-loop-WT motifs. This motif imparts significant fold stability to peptides as short as 8 residues. High-resolution NMR structures of a 16- (KKWTWNPATGKWTWQE, DeltaG(U)(298) >or= +7 kJ/mol) and 12-residue (KTWNPATGKWTE, DeltaG(U)(298) = +5.05 kJ/mol) hairpin reveal a common turn geometry and edge-to-face (EtF) packing motif and a cation-pi interaction between Lys(1) and the Trp residue nearest the C-terminus. The magnitude of a CD exciton couplet (due to the two Trp residues) and the chemical shifts of a Trp Hepsilon3 site (shifted upfield by 2.4 ppm due to the EtF stacking geometry) provided near-identical measures of folding. CD melts of representative peptides with the -TW-loop-WT- motif provided the thermodynamic parameters for folding, which reflect enthalpically driven folding at laboratory temperatures with a small DeltaC(p) for unfolding (+420 J K(-)(1)/mol). In the case of Asx-Pro-Xaa-Thr-Gly-Xaa loops, mutations established that the two most important residues in this class of direction-reversing loops are Asx and Gly: mutation to alanine is destabilizing by about 6 and 2 kJ/mol, respectively. All indicators of structuring are retained in a minimized 8-residue construct (Ac-WNPATGKW-NH(2)) with the fold stability reduced to DeltaG(U)(278) = -0.7 kJ/mol. NMR and CD comparisons indicate that -TWXNGKWT- (X = S, I) sequences also form the same hairpin-stabilizing W/W interaction.     

Time-gated luminescence microscopy with responsive nonmetal probes for mapping activity of protein kinases in living cells

A photoluminescence probe ARC-1185, possessing both high affinity towards basophilic protein kinases (PKs) and microsecond-scale luminescence lifetime when associated with a kinase, was used for the mapping of ARC-1185-PK complexes in living cells with time-gated luminescence microscopy.     

Cell-penetrating peptides as delivery vehicles for a protein-targeted terbium complex

Release after transmission: Arginine-rich, cell-penetrating peptides (CPPs) mediate cytoplasmic delivery of trimethoprim (TMP)-terbium complex conjugates and selective, intracellular labeling of E.?coli dihydrofolate reductase (eDHFR) fusion proteins. A disulfide bond linking CPP and cargo is reduced following uptake. CPP conjugation can be used to deliver otherwise cell-impermeable, ligand-fluorophore conjugates.     

Study of catalytic reduction and photodegradation of methylene blue by heterogeneous catalyst

The photocatalytic degradation of methylene blue is investigated in aqueous solution containing CoS/nanoAl-MCM-41 photocatalyst under visible light. The catalyst is characterized by X-ray diffraction (XRD), UV-vis diffused reflectance spectra (UV-vis DRS) and transmission electron microscopy (TEM) techniques. The effect of CoS, nanoAl-MCM-41 support and different wt% of CoS over the support on the photocatalytic degradation and influence of parameters such as CoS loading, catalyst amount, pH and initial concentration of methylene blue on degradation are evaluated. Hypsochromic effects (i.e. blue shifts of spectral bands) resulting from N-demethylation of the dimethylamino group in methylene blue occurs in presence of CoS/nanoAl-MCM-41 under ambient condition. Meanwhile, the bleaching of methylene blue MB, by sulfide ion, in an aqueous solution is studied in the presence nanoAl-MCM-41 catalyst. In the presence of sulfide ions, MB is bleached to its colorless leuco (LMB) and MBH(2)(+) forms. In an acidified solution (pH<2) the bleaching process generates LMB and by changing pH between 2.0 and 7.0 bleaching of MB dye to MBH(2)(+) form is observed. Using nanoAl-MCM-41 with encapsulated CoS nanoparticles only causes demethylation of MB in aqueous solution.