A new microbial electrode for BOD estimation

A new microbial electrode using immobilizedClostridium butyricum was prepared for biochemical oxygen demand (BOD) estimation of wastewaters. The current of the electrode was decreased with time until a steady state was reached. The steady state current was in all cases attained within 30-40 min at 37°C, and the maximum current output was obtained at 37°C and pH between 6.2 and 7.0. A linear relationship was obtained between the steady state current and BOD. The steady state current values were reproducible within ±7% of the relative error. The BOD of industrial wastewaters can be estimated by using the microbial electrode. Relative error of the BOD estimation of industrial wastewaters was within ± 10%. The current output of the microbial electrode was almost constant for 30 days.     

Template-directed dynamic synthesis of mechanically interlocked dendrimers

The versatility and efficiency of dynamic covalent chemistry (DCC) has been exploited in the convergent synthesis of mechanically interlocked dendrimers that are based upon the mutual recognition expressed between secondary dialkylammonium ions and crown ether-like macrocycles. Reversible imine bond formation is employed to clip two acyclic fragments, one of them a diformylpyridine unit bearing a dendritic side chain, and the other a complementary dianiline in the shape of the di(o-aminophenyl)ether of tetraethylene glycol, around each arm of a tritopic trisammonium ion core, thereby affording a branched [4]rotaxane. This template-directed strategy has been demonstrated to work in very high yields (>90%) with successive generations (G0-G2) of a modified Fréchet-type dendritic wedge attached to the 4-position of the diformylpyridine unit. Reduction of these dynamic dendritic systems is achieved upon treatment with borane.THF and results in kinetically stable compounds. The inherent modularity of the overall process should allow for the rapid and straightforward access to many other analogous mechanically interlocked systems in which either the branched core or the dendritic periphery can be modified to suit the needs of any given application of these molecules. Indeed, the dynamic nature of the initial thermodynamically mediated assembly could be utilized in order to amplify particular products from a potential library as a result of a selective recognition process.     

Dynamic capillary coatings with zwitterionic surfactants for capillary isoelectric focusing

The use of surfactants as additives was demonstrated for the first time in capillary isoelectric focusing (CIEF) to dynamically modify the surfaces of bare fused silica capillaries. These surfactants were zwitterionic sulfobetaines: dodecyldimethyl (3-sulfopropyl) ammonium hydroxide (C12N3SO3), hexadecyldimethyl (3-sulfopropyl) ammonium hydroxide (C16N3SO3) and coco (amidopropyl)hydroxyldimethylsulfobetaine (Rewoteric AM CAS U). They were added directly to the protein-ampholyte mixture, and remained in the capillary during isoelectric focusing and mobilization. The C16N3SO3 and CAS U coatings were shown effective in CEF. Separation of seven IEF protein standards was obtained, with significantly improved resolution compared to that from an uncoated silica capillary. The effect of these surfactants on the electroosmotic flow (EOF) in CIEF was determined. CAS U was effective in suppressing the EOF at neutral and alkaline pH conditions, C16N3SO3 was effective in suppressing EOF at acidic and neutral pH conditions. C12N3SO3 however had little effect on the EOF. The pH gradients formed inside these surfactant coated capillaries were recta-linear at pH 6 to 9 (R2 approximately equal to 0.99). Reproducibility of migration time and peak area was determined. For all three coatings, the migration time standard deviations were less than 1.6 min, and the relative standard deviations of area were below 10%. The protein recovery in the CAS U-modified capillary was quantitative or near-quantitative for five of the seven proteins studied.     

Polytheonamides A and B, highly cytotoxic, linear polypeptides with unprecedented structural features, from the marine sponge, Theonella swinhoei

Polytheonamides A and B are highly cytotoxic polypeptides with 48 amino acid residues isolated from the marine sponge, Theonella swinhoei. The structure of polytheonamide B was determined by spectral and chemical methods, especially extensive 2D NMR experiments, which resulted in the unprecedented polypeptide structure; the N-terminal glycine blocked with a 5,5-dimethyl-2-oxo-hexanoyl group, the presence of eight tert-leucine, three beta-hydroxyvaline, six gamma-N-methylasparagine, two gamma-N-methyl-beta-hydroxyasparagine, and beta,beta-dimethymethionine sulfoxide residues. More significantly, it has the sequence of alternating D- and L-amino acids. Polytheonamide A is an epimer of polytheonamide B differing only in the stereochemistry of the sulfoxide of the 44(th) residue.     

A simple and stereoselective synthesis of 7-azabicyclo[2.2.1]-heptane-1,2,3,4-tetracarboxylates

The photoinitiated reaction of 1,1′-bis(methoxycarbonyl)divinylamine with various maleates and fumarates afforded novel 7-azabicyclo[2.2.1]heptane-1,2,3,4-tetracarboxylates. The spectral investigation of the products showed that the reaction proceeded stereoselectively, retaining the original configuration of the reagents.     

Synthesis and properties of polymeric azine and thiazine dyes

Some polymeric azine or thiazine dyes were prepared by radical polymerization of dye monomers or by polymer reactions between dyes and suitable prepolymers, and their photoredox reactivities were studied. The thionine polymers containing labile ? OH groups exhibited photochromism and thermochromism, which were extremely sensitive to the moisture content of the polymer film. The reversibility of the photochromism and thermochromism increased with the water content in the film. The water-soluble polymeric dyes were photobleached under the influence of suitable reducing agents. The degree of photobleaching was smaller than for the monomeric systems except for the dye polymers containing ? OH groups, probably because of the large steric hindrance of the polymers.     

Non empirical quantum mechanical calculations of the1H,13C,15N and17O magnetic shielding constants and of the spin-spin coupling constants in formamide,hydrated formamide and N-methylformamide

The magnetic shielding constants of the different atoms of formamide, hydrated formamide and N-methylformamide are calculated by anab initio method. For the protons of formamide the measured differences between their chemical shifts are correctly reproduced by theory, provided that the molecular geometry used as input is carefully chosen. The differences between the values of the magnetic shielding constants calculated for formamide and hydrated formamide show that intermolecular hydrogen bonding produces variations of chemical shifts for all the atoms of the molecule except the formyl proton. The calculated chemical shift variations between formamide and N-methylformamide are compared to the experimental values and discussed in relation with different hydrogen bonding possibilities of the two molecules. The calculation of the contact term of the spin-spin coupling constants of formamide and hydrated formamide shows that in most cases the measured trends are satisfactorily reproduced and that the variations of these terms upon hydration are less than 3%.     

A proposal for the mechanism-of-action of diazoparaquinone natural products

Treatment of the representative diazoparaquinone prekinamycin dimethyl ether with Bu3SnH/AIBN in aromatic solvents furnishes moderate-to-good yields of formal aryl adducts wherein a molecule of solvent is attached to the carbon (C(11)) previously bearing the diazo function. Substituent studies provide evidence in support of a radical aromatic substitution mechanism, in which radical addition to the diazoparaquinone function generates an intermediate C(11) vinylic radical.     

SEASONAL TRENDS IN ERYTHEMAL and CARCINOGENIC ULTRAVIOLET RADIATION AT MID-SOUTHERN LATITUDES1989–1991

A network of solar carcinogenic/erythemal ultraviolet radiometers has been established in New Zealand. Daily integrated irradiances of this biologically harmful ultraviolet radiation for 1989, 1990 and 1991 are reported from radiometers located at Wellington (41°S) and Christchurch (43.5°S) and for 1990 and 1991 from the Auckland (37°S) radiometer. Although the monitoring program has not been running sufficiently long to discern any long-term changes in levels of solar ultraviolet radiation, shorter term trends are apparent, which are attributed to a seasonal cycle in levels of ozone at midlatitudes and changes in atmospheric aerosols.     

A catalytic immuno-reactor for the amperometric determination of human serum albumin

A catalytic immuno-reactor for the determination of human serum albumin (HSA) was constructed by using immobilized antibody and an amperometric detector. A sandwich assay with hemin-labeled antibody to catalyze the decomposition of hydrogen peroxide was used, the catalytic activity of the hemin-antibody conjugate being determined by measuring the decrease in hydrogen peroxide concentration. The reaction of hemin-labeled antibody with antigen was complete within 30 min and the current decrease was correlated with the HSA concentration. The relative standard deviation was about 9% at an HSA concentration of 1 mg ml^?1.