Polymerization of cyclic derivatives of uracil and thymine

Cyclic derivatives of uracil and thymine were synthesized from their corresponding 1-(2′-chloroethyl) derivatives by dehydrochlorination. These compounds were found to undergo a variety of reactions, giving many valuable derivatives of uracil and thymine. The cyclic derivatives, as monomers, were polymerized with a cationic initiator by a unique ring-opening process. The polymerization proceeded by ring opening with isomerization of the pyrimidine ring to give a polymer in which pyrimidine rings were connected with ethylene between N-1 and N-3 or O-4 in the pyrimidine ring. The structure of these polymers was determined by nuclear magnetic resonance (NMR), ultraviolet (UV), infrared (IR), and mass spectra. The structure was affected by polymerization temperature.     

Interfacial and micellar properties of binary mixtures of surfactant and phospholipid in an aqueous medium

Mixed micelles formed by zwitterionic surfactant dimethyldodecylammniopropane sulfonate and short-chain phospholipid 1,2-diheptanoyl-sn-glycero-3-phosphocholine in different proportions in an aqueous medium have been studied physicochemically at an air/water interface and in the bulk by using interfacial tension and pyrene fluorescence intensity measurements, respectively. The critical micellar concentration and free energies of micellization and of interfacial adsorption have been determined. The interfacial study reveals that a mixed monolayer is formed at the air/water interface by the adsorption of surfactant and phospholipid monomers. This has been confirmed by evaluating the interfacial parameters; the maximum surface excess, the minimum area per molecule of a surface-active compound, and the Gibbs surface excess related to surface pressure. The nonideality of mixing, expressed in the terms of the regular solution interaction parameter, #, has negative values over the whole mole fraction range. The negative # values indicate the mutual synergism between the surfactant and phospholipid monomers. The equilibrium distribution of components between micelle and monomer phases was evaluated using a theoretical treatment based on excess thermodynamics quantities evaluated by Motomura's formulation.     

1,6,11,16‐Tetra­oxacyclo­eicosane‐2,5,12,15‐tetra­one

The 20‐membered ring of the title compound, C₁₆H₂₄O₈, adopts an approximately flat rectangular structure with three‐ and seven‐bond sides and lies across a crystallographic center of inversion. The corners of the ring occur at both ends of one of the planar ester segments. All of the carbonyl O atoms are involved in inter­molecular C—H⋯O hydrogen bonds.     

Synthesis of stable and cell-type selective analogues of cyclic ADP-ribose, a Ca(2+)-mobilizing second messenger. Structure--activity relationship of the N1-ribose moiety

We previously developed cyclic ADP-carbocyclic ribose (cADPcR, 2) as a stable mimic of cyclic ADP-ribose (cADPR, 1), a Ca(2+)-mobilizing second messenger. A series of the N1-ribose modified cADPcR analogues, designed as novel stable mimics of cADPR, which were the 2"-deoxy analogue 3, the 3"-deoxy analogue 4, the 3"-deoxy-2"-O-(methoxymethyl) analogue 5, the 3"-O-methyl analogue 6, the 2",3"-dideoxy analogue 7, and the 2",3"-dideoxydidehydro analogue 8, were successfully synthesized using the key intramolecular condensation reaction with phenylthiophosphate-type substrates. We investigated the conformations of these analogues and of cADPR and found that steric repulsion between both the adenine and N9-ribose moieties and between the adenine and N1-ribose moieties was a determinant of the conformation. The Ca(2+)-mobilizing effects were evaluated systematically using three different biological systems, i.e., sea urchin eggs, NG108-15 neuronal cells, and Jurkat T-lymphocytes. The relative potency of Ca(2+)-mobilization by these cADPR analogues varies depending on the cell-type used: e.g., 3"-deoxy-cADPcR (4) > cADPcR (2) > cADPR (1) in sea urchin eggs; cADPR (1) > cADPcR (2) approximately 3"-deoxy-cADPcR (4) in T-cells; and cADPcR (2) > cADPR (1) > 3"-deoxy-cADPcR (4) in neuronal cells, respectively. These indicated that the target proteins and/or the mechanism of action of cADPR in sea urchin eggs, T-cells, and neuronal cells are different. Thus, this study represents an entry to cell-type selective cADPR analogues, which can be used as biological tools and/or novel drug leads.     

Tris(porphyrinyl-oxinato)Ga Complexes as a Photosynthetic Antenna Miniature

Two oxinylporphyrins, 5-(8-hydroxy-5-quinolinyl)-10,15,20-( p -tolyl)- porphyrin ( 1 ) and 5,15-bis(8-hydroxy-5-quinolinyl)-10,20-bis( n -heptyl)-porphyrin ( 2 ), were prepared and coordinated with Ga(III) to afford tris(oxinato) complex 3 and poly(oxinato) complex 4 , respectively. The structure of 3 was analyzed by variable temperature NMR study with referring to tris(8-hydroxy-5-quinolinyl)Ga(III) complex 5 to be in a meridional form. Oxinato ligands of 3 and 5 were exchanged with one another, with keeping the meridional structure. UV-Vis and fluorescence spectra of tris(oxinato)complex 3 and poly(oxinato)complex 4 were compared with each monomeric compound 1 and 2 . The absorption spectra showed only a slight broadening of the Soret band, suggesting trivial electronic and excitonic interactions. The fluorescence intensity was increased significantly compared with each monomeric compound 1 and 2 . At the same time, efficient excitation energy transfer among three porphyrins has been observed.     

Influence of β‐Cyclodextrin on the Mixed Micellization Process of Sodium Dodecyl Sulfate and Sodium Lauroyl Sarcosine and Formation of Inclusion Complexes

In this work, we have studied the influence of different concentrations of β‐Cyclodextrin (β‐CD) on the mixed micellization of anionic surfactants sodium dodecyl sulfate (SDS) and sodium lauroyl sarcosine (SLAS) at different SDS mole fractions (α_SDS). From conductivity data, the critical micellar concentration (cmc), the equivalent ionic conductivities of the monomeric species (Λ_m), the associated species (Λ_assc) and the micelle (Λ_mic), the degree of counterion dissociation (α) in the presence of β‐CD were evaluated from the slope of the conductivity versus concentration plots for the pure and binary mixtures. The apparent cmc of the surfactants vary linearly with the β‐CD concentrations. From the dependence of cmc of the surfactants on β‐CD concentration, we have deduced the association constant (K) of surfactant‐β‐CD inclusion complexes assuming 1∶1 stoichiometry. Theories of Clint, Regular solution, and Motomura's have been used for the evaluation of ideality or nonideality of the mixed system. Mixed micelles were found to be rich in SDS content at the cmc in the presence and the absence of β‐CD. The cmc values have been used to evaluate the transfer of standard free energy of micelles (ΔG⁰ _M,tr) from the aqueous medium to additive medium.     

Interactions of γ-Cyclodextrin with the Mixed Micelles of Anionic Surfactants and Their Inclusion Complexes Formation

Interactions of γ-cyclodextrin (γ-CD) with the single and mixed micelles of sodium dodecyl sulfate (SDS) and sodium lauroyl sarcosine (SLAS) have been studied at different concentrations of γ-CD by using conductivity measurements. From conductivity data, the pure and mixed critical micellar concentration (cmc), the equivalent ionic conductivities of the monomeric species (Λ _m), the associated species (Λ _assc) and the micelle (Λ _mic), the degree of counterion dissociation (χ) in the presence of γ-CD have been evaluated from the slope of the conductivity versus concentration plots for the pure and binary mixture of surfactants. From the dependence of cmc of the surfactantson γ-CD concentration, we have deduced the association constant (K) of surfactant-γ-CD inclusion complexes assuming 2:1 stoichiometry. Theories of Clint, regular solution, and Motomura's have been used for the evaluation of ideality or nonideality of the mixed system. Mixed micelles were found to be rich in SDS content in the presence and the absence of γ-CD. The cmc values have been used to evaluate the transfer of standard free energy of micelles (ΔG⁰ _M,tr) from the aqueous medium to additive medium.     

Synthesis of core-shell structured Au@Bi2S3 nanorod and its application as DNA immobilization matrix for electrochemical biosensor construction

The core-shell structured Au@Bi2S3 nanorods have been prepared through direct in-situ growth of Bi2S3 at the surface of pre-synthesized gold nanorods.The product was characterized by X-ray diffraction,transmission electron microscopy and energy-dispersive X-ray spectroscopy.Then the obtained Au@Bi2S3 nanorods were coated onto glassy carbon electrode to act as a scaffold for fabrication of electrochemical DNA biosensor on the basis of the coordination of-NH2 modified on 5’-end of probe DNA and Au@Bi2S3.Electrochemical characterization assays demonstrate that the Au@Bi2S3 nanorods behave as an excellent electronic transport channel to promote the electron transfer kinetics and increase the effective surface area by their nanosize effect.The hybridization experiments reveal that the Au@Bi2S3 matrix-based DNA biosensor is capable of recognizing complementary DNA over a wide concentration ranging from 10 fmol/L to 1 nmol/L.The limit of detection was estimated to be 2 fmol/L(S/N=3).The biosensor also presents remarkable selectivity to distinguish fully complementa ry sequences from basemismatched and non-complementary ones,showing great promising in practical application.     

Enzymatic silicone oligomerization catalyzed by a lipid-coated lipase

A lipid (1)-coated lipase can catalyze the oligomerization of diethoxydimethylsilane (DEDMS) in isooctane containing 2wt% water, where the polymerization occurs at the OH group of the coating lipid (1) in the enzyme cavity.     

Magnetic field generation from cosmological perturbations

In this Letter, we discuss the generation of magnetic field from cosmological perturbations. We consider the evolution of three component plasma (electron, proton, and photon) evaluating the collision term between electrons and photons up to the second order. The collision term is shown to induce electric current, which then generates magnetic field. There are three contributions, two of which can be evaluated from the first-order quantities, while the other one is fluid vorticity, which is purely second order. We estimate the magnitudes of the former contributions and show that the amplitude of the produced magnetic field is about approximately 10(-19) G at 10 Mpc comoving scale at the decoupling. Compared to astrophysical and inflationary mechanisms for seed-field generation, our study suffers from much less ambiguities concerning unknown physics and/or processes.