Determination of cisplatin and related platinum complexes in plasma ultrafiltrate and urine by high-performance liquid chromatography with on-line radioactivity detection

A reversed-phase ion-pair chromatographic method with on-line radioactivity detection for the simultaneous determination of 195mPt-labelled cisplatin and related platinum complexes has been developed. With this system a good resolution of various radiolabelled platinum complexes can be achieved. The detection limit of the radioactivity detector is 10 ng of cisplatin (specific activity of 15 MBq/mg cisplatin) per millilitre of urine or plasma ultrafiltrate. The detector response is independent of both the chemical structure of the platinum complexes and the matrix composition of the samples. This method may serve as a reference system for other high-performance liquid chromatographic systems with less specific and sensitive detectors.     

Zwei neue pentacyclische dimere des cycloheptatriens

Titanium - catalyzed dimerization of cycloheptatriene affords pentacyclo[7.5.0.0^2,8.0^5,14.0^7,11]tetradeca-3,12-diene, $\text{3}$, and pentacyclo[8.4.0.0^3,7.0^4,14.0^6,11]tetradeca-8,12-diene, $\text{4}$. By heating, $\text{3}$ is converted quantitatively into $\text{4}$.     

An evaluation of cellulose as a substrate for room-temperature phosphorescence

Cotton-linter pulps, wood pulps and several filter papers have been evaluated as substrates for room-temperature phosphorescence. A variety of chemical treatments of one filter paper is discussed in terms of reducing the background phosphorescence of the cellulose and in evaluating possible trace contaminants in cotton fibres. In order to account for uniformity of filter paper used in room temperature phosphorescence, a final evaluation of several different lots of one type of filter paper is presented.     

Imaging the activity of nitrate reductase by means of a scanning electrochemical microscope

Scanning electrochemical microscopy (SECM) was used to characterize immobilized nitrate reductase (NaR) from Pseudonomonas stutzeri (E.C. 1.7.99.4). Nitrate reductase with membrane fragment was embedded in a polyurethane hydrogel in a capillary and solubilized NaR without membrane fragment was covalently coupled to a diaminoethyl-cellulose-carbamitate film on glass. After systematic studies of possible mediators, SECM feedback imaging of both forms of immobilized NaR was accomplished with methylviologen as redox mediator.     

Oxepinamides A-C and fumiquinazolines H--I: bioactive metabolites from a marine isolate of a fungus of the genus Acremonium

Three new oxepin-containing natural products (1-3) and two new fumiquinazoline metabolites (4-5) have been isolated from organic extracts of the culture broth and mycelia of an Acremonium sp., a fungus obtained from the surface of the Caribbean tunicate Ecteinascidia turbinata. The structures of the five compounds were determined through extensive analysis of 1D- and 2D-NMR data, and mass spectrometry. Compound 1 exhibited good anti-inflammatory activity in a topical RTX-induced mouse ear edema assay. Compounds 4 and 5 exhibited weak antifungal activity toward Candida albicans in a broth microdilution assay.     

On air entrainment in coatings

A series of experiments that clarify how air bubbles become entrained into coatings are described. The contact line dynamics at the air-liquid interface surrounding a fiber is characterized for a typical coating die operating under atmospheric and pressurized conditions. Glycerin and other viscous liquids are used to reveal that a critical fiber speed exists at which air entrainment begins. The observations confirm that the critical capillary number Ca(c) depends on the physical properties of the coating material, in the form of the Morton number. When the liquid supply is pressurized, the experiments show that adjusting the pressure can stabilize the displaced free surface interface at a prescribed location. Controlling the meniscus location in this way eliminates air entrainment. The threshold occurs when the applied pressure balances the shear exerted on the coating by the moving fiber. Using this approach it is possible to eliminate air entrainment and attain stable wetting at very large values of the capillary number, e.g., Ca congruent with 50.     

Sorption Concentration of Radiocesium on NaX Zeolite Modified with Cu2[Fe(CN)6]

Sorption of ¹³⁷Cs on NaX zeolite modified with Cu₂[Fe(CN)₆] was studied under dynamic conditions.     

Iodine(V) reagents in organic synthesis. Part 3. New routes to heterocyclic compounds via o-iodoxybenzoic acid-mediated cyclizations: generality, scope, and mechanism

The discovery and development of the o-iodoxybenzoic acid (IBX) reaction with certain unsaturated N-aryl amides (anilides) to form heterocycles are described. The application of the method to the synthesis of delta-lactams, cyclic urethanes, hydroxy amines, and amino sugars among other important building blocks and intermediates is detailed. In addition to the generality and scope of this cyclization reaction, this article describes a number of mechanistic investigations suggesting a single electron transfer from the anilide functionality to IBX and implicating a radical-based mechanism for the reaction.     

Post-column reaction detection of biotin in human plasma ultrafiltrate based on laser-induced fluorescence energy transfer in the far-red spectral region

High performance liquid chromatography followed by post-column reaction detection in the far-red spectral region provides added sensitivity and selectivity. A homogeneous fluorescence energy transfer assay in the competitive mode based on the binding of biotin and streptavidin was developed as an on-line post-column reaction detection system. The labels used for energy transfer were R-Phycoerythrin conjugated to biotin and Cyanine 5 labeled with streptavidin. The energy transfer peak was measured at 670 nm and excitation was achieved using the 488 nm line of an argon ion laser. The biotin concentration in plasma ultrafiltrate ranged from 0.024 to 6.12 ng/mL (n = 6). The precision of the two controls, 0.24 and 2. 44 ng/mL, was found to be 18.70% and 9.92% relative standard deviation respectively. Accuracy was 10.47% and 1.95% difference from spiked, respectively (n = 6). The limit of detection was 21.70 pg/mL (8.90 x 10(-11)M) calculated based on a factor of 2x the standard deviation of the blank (n = 6). The correlation coefficient for the calibration curve was found to be 0.9995. Recovery from plasma ultrafiltrate at 2.44 ng/mL was 103.40% (n = 6). Detection selectivity was indicated by the absence of background fluorescence in six different plasma samples collected from six individual donors. Endogenous levels were detected in two of the six pools of plasma ultrafiltrates.     

Biomimetic dyes as affinity chromatography tools in enzyme purification

Affinity adsorbents based on immobilized triazine dyes offer important advantages circumventing many of the problems associated with biological ligands. The main drawback of dyes is their moderate selectivity for proteins. Rational attempts to tackle this problem are realized through the biomimetic dye concept according to which new dyes, the biomimetic dyes, are designed to mimic natural ligands. Biomimetic dyes are expected to exhibit increased affinity and purifying ability for the targeted proteins. Biocomputing offers a powerful approach to biomimetic ligand design. The successful exploitation of contemporary computational techniques in molecular design requires the knowledge of the three-dimensional structure of the target protein, or at least, the amino acid sequence of the target protein and the three-dimensional structure of a highly homologous protein. From such information one can then design, on a graphics workstation, the model of the protein and also a number of suitable synthetic ligands which mimic natural biological ligands of the protein. There are several examples of enzyme purifications (trypsin, urokinase, kallikrein, alkaline phosphatase, malate dehydrogenase, formate dehydrogenase, oxaloacetate decarboxylase and lactate dehydrogenase) where synthetic biomimetic dyes have been used successfully as affinity chromatography tools.