Changeable reactivity of ketyl radicals derived from 2-bromomethyl-2-(3-butenyl)benzocyclic-1-alkanones depending on electron transfer conditions employed

Photoinduced electron transfer reaction of 2-bromomethyl-2-(3-butenyl)benzocyclic-1-alkanones with amines afforded 5-exo radical cyclization products while electron transfer reaction with samarium diiodide produced cyclopropanols.     

Design and synthesis of highly sensitive and selective fluorescein-derived magnesium fluorescent probes and application to intracellular 3D Mg2+ imaging

The role of intracellular magnesium ions is of high interest in the fields of pharmacology and cellular biology. To accomplish the dynamic and three-dimensional imaging of intracellular Mg2+, there is a strong desire for the development of optimized Mg2+ fluorescent probes. In this paper we describe the design, synthesis, and cellular application of the three novel Mg2+ fluorescent probes KMG-101, -103, and -104. The compounds of this series feature a charged beta-diketone as a binding site specific for Mg2+ and a fluorescein residue as the fluorophore that can be excited with an Ar+ laser such as is widely used in confocal scanning microscopy. This molecular design leads to an intensive off-on-type fluorescent response toward Mg2+ ions. The two fluorescent probes KMG-103 and -104 showed suitable dissociation constants (Kd,Mg2+ = 2 mM) and nearly a 10-fold fluorescence enhancement over the intracellular magnesium ion concentration range (0.1-6 mM), allowing high-contrast, sensitive, and selective Mg2+ measurements. For intracellular applications, the membrane-permeable probe KMG-104AM was synthesized and successfully incorporated into PC12 cells. Upon application of the mitochondria uncoupler FCCP to the probe-incorporated cells, the resulting increase in the free magnesium ion concentration could be followed over time. By using a confocal microscope, the intracellular 3D magnesium ion concentration distributions were satisfactorily observed.     

Hydrolysis of DNA by cerium(IV)/EDTA complex

Homogeneous solutions are formed from equimolar amounts of Ce(NH₄)₂(NO₃)₆ and EDTA. These solutions hydrolyze single-stranded DNA far more efficiently than double-stranded DNA. In contrast, Ce(IV) hydroxide gel, obtained in the absence of EDTA, hydrolyzes both single-stranded and double-stranded DNAs at almost the same rates. In order to achieve this substrate-specificity sufficiently, the mole ratio of EDTA to Ce(NH₄)₂(NO₃)₆ must be 1.0 or greater. By using this remarkable specificity of Ce(IV)/EDTA complex, gap-site in substrate DNA is selectively hydrolyzed. The scission-site is modulated by use of appropriate combination of oligonucleotide additives. The reactions have been kinetically analyzed.     

Analysis to obtain precise density fluctuation of supercritical fluids by small-angle X-ray scattering

A procedure of analysis for small-angle X-ray scattering (SAXS) data has been established to obtain density fluctuation of supercritical fluids near the critical point. It is indispensable for the certain analysis to utilize both of high-quality SAXS data measured under stable thermodynamic condition and accurate P–ρ–T data in supercritical region. As a standard example, SAXS measurements have been performed for supercritical CO₂, which is a suitable sample satisfying the condition for both experiment and analysis. The measurements were carried out along four isothermal conditions at reduced temperature of T_r = T/T_c = 1.020, 1.022, 1.043 and 1.064. Comparing the experimental density fluctuation with calculated one from the most reliable equation of state, the differences are within 8% at most.     

Conformational structure of divinyl sulfide

The potential of internal rotation about the bond for vinyl methyl sulfide is applied with some modifications to rotation about the analogous bonds in the divinyl sulfide molecule. The potential energy map of divinyl sulfide is discussed with regard to the excited torsional vibrational states. Three stable conformers with approximately identical energies were established. For a complete picture of the rotational isomerism it is also necessary to take account of the torsional vibrational stationary states with large amplitude.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1531–1535, July, 1991.     

Solvation effects in near-critical binary mixtures

A Ginzburg-Landau theory is presented to investigate solvation effects in near-critical polar fluid binary mixtures. Concentration dependence of the dielectric constant gives rise to a shell region around a charged particle within which solvation occurs preferentially. As the critical point is approached, the concentration has a long-range Ornstein-Zernike tail representing strong critical electrostriction. If salt is added, strong coupling arises among the critical fluctuations and the ions. The structure factors of the critical fluctuations and the charge density are calculated and the phase transition behavior is discussed.     

Studies on the syntheses of analgesics. Part 50. Synthesis of optically active 2-[4-(1-oxo-2-isoindolinyl)phenyl]propanoic acid. [Studies on the syntheses of heterocyclic compounds. Part 742]

2-[4-(1-Oxo-2-isoindolinyl)phenyl]propanoic acid ( 1 ) having a potent analgesic and anti-inflammatory activity could be obtained by three methods, which were found to provide extremely useful ways for the synthesis of 1 from the industrial point of view. (E)- and (Z)-Isomers of 2-butenoic acid and oxiranecarboxylic acid derivatives as the intermedaites in the synthesis of 1 were separated and characterized. Furthermore, the optical resolution of (±)-2-[4-(1-oxo-2-isoindolinyl)phenyl]propanoic acid was successfully achieved using cinchonidine as a resolution reagent.     

Second-derivative spectrophotometric study on the interactions of chlorpromazine and triflupromazine with bovine serum albumin

The second-derivative spectra of chlorpromazine (CPZ) or triflupromazine (TFZ) in buffer solutions (pH 7.4) containing various amounts of BSA (the reference solutions contained the same amount of BSA) showed derivative isosbestic points. The residual background signals derived from incomplete suppression of BSA signals can be entirely eliminated in the second-derivative spectra and BSA has spectrophotometrically one kind of binding site for CPZ or TFZ. The fractions of the drugs bound to BSA were calculated from the derivative intensity differences (ΔD values) of CPZ or TFZ before and after the addition of BSA. Scatchard plot experiments suggested that the binding of the drugs to BSA could be explained as a partition like non-specific binding model. The association constants (K) of CPZ or TFZ with BSA were calculated from the ΔD values according to the non-specific binding model by a nonlinear least-squares method. The K values were almost constant for all of the drug concentrations studied, and good reproducibility was obtained. The fractions predicted by the K values were in good coincidence to the observed values. These results confirm the usefulness of the proposed derivative method which does not need any separation procedures.     

Molecule-Responsive Fluorescent Sensors of α-Helix Peptides Bearing α-Cyclodextrin, Pyrene and Nitrobenzene Units in Their Side Chains

-Helix peptides bearing one unit of -cyclodextrin (-CD), one unit of pyrene and one unit of nitrobenzene (NB) in their side chains have been designed and synthesized as novel molecule-responsive devices.In both the CD-peptides, -PR17 and -PL17, the NB unit is separated from the CD unit by two turns of the helix. Two reference peptides (PL17, and -P17,) have also been synthesized. The circular dichroism studies in the peptide absorption region (200–250 nm)of -PR17 and -PL17 suggestthat the CD-peptides form stable-helixstructures (83–77%), which was destabilized by accommodating guest molecules (e.g., n-pentanol) into the CD cavity. It suggests that formation of intramolecular host–guest(CD–NB) complex stabilized thehelical structure and exogenous guest molecule excluded the appending NB moiety from inside to outside of the CD cavity, thereby causing destabilization of the helical structure and increasing the random coil content. The ICD spectra of the peptides in the pyrene and nitrobenzene absorption region (250–40 nm) suggest that NB forms inclusion complex with CD. The fluorescence studies revealed that the fluorescence of the pyrene unit is quenched by the NB unit in -PR17 and -PL17. The fluorescence intensity increases with increasing guest concentration for the CD-peptides.This guest-responsiveenhancement in the fluorescence intensity can be explained in terms of increased distance between the pyrene and NB moieties, which is caused by exclusion of the NB moiety from the CD cavity by guest accommodation. Using the guest-responsive fluorescence quenching properties of the CD-peptides, we have obtained binding constants for various short chain alkanols. -PL17 has higher binding affinity to the guest molecules than its isomer, -PR17, indicating that the location of functional groups on the peptide scaffold is important in molecule detection.     

Pd-catalyzed selective addition of heteroaromatic C-H bonds to C-C triple bonds under mild conditions

Simple heteroarenes such as pyrroles and indoles undergo addition reactions to C-C triple bonds in the presence of a catalytic amount of Pd(OAc)(2) under very mild conditions, affording cis-heteroarylalkenes in most cases. The cleavage of aromatic C-H bonds is the possible rate-determining step in CH(2)Cl(2), and the addition of heteroaromatic C-H bonds to C-C triple bonds is in a trans-fashion.