Biosynthesis of psilotin from [2′,3′-13C2,1′-14C,4-3H]phenylalanine studied with 13C-NMR

The 6-phenyl-dihydro-α-pyrone moiety of psilotin is formed from [2′,3′-¹³C₂,1′-¹⁴C,-4-³H]phenylalanine in the plant $\text{Psilotum}$$\text{nudum}$ with retention of all the isotopes.     

Chromatography as a reference technique for the determination of clinically important steroids

Chromatographic methods (paper chromatography, thin layer chromatography, high performance liquid chromatography, gas chromatography and gas chromatography-mass spectrometry) for the determination of clinically important steroids in biological specimens are reviewed. The emphasis is on the use of gas chromatography, gas chromatography-mass spectrometry and high performance liquid chromatography as reference rather than routine techniques. Chromatographic methods are compared with colorimetric, fluorimetric and radioimmunoassay procedures in terms of simplicity of operation, cost and ability to analyse large numbers of specimens. The importance of correct specimen collection and storage are discussed. Sample preparation techniques for the various analytical methods are described. These include extraction of free and conjugated steroids from serum, plasma, urine and saliva by solvent partition, with polymer-based resins such as Amberlite XAD-2, DEAE-Sephadex and Sephadex resins bonded with various other function groups and, more recently, with chemically bonded reversed-phase silicas.     

Interrogating functions

Two functions are considered where the goal is to find the roots of those functions. In neither case is an exact non-trivial solution possible. It is demonstrated that with basic mathematical techniques a great deal of information can be gained about the function and that good approximations can be made for the roots involved.     

LIGHT-MEDIATED ACTIVITIES OF THIARUBRINES AGAINST HUMAN IMMUNODEFICIENCY VIRUS

Abstract— Two thiarubrines (dithiacylohexadienes), which werw isolated recently species of Astreraceae, were investigated for light-mediated antiviral activity aginst human immunodeficiency virus(HIV–1). Both compounds (thiarubrines A and D) showed good anti-HIV activity, in micromolar concentrations, which was dependent upon UVA radiation, They showed no anti-viral activity in the darjm ad only weak visiblke light-mediated activity, despite the significant absorbance of these compounds in th e480 nm region. the resulting inactivated virus was unable to replicate in cell cultures, as indicated by loss of cytopathogenicity, the absence of cells expressingHIV–1 antigens and lack of production ofHIV–1 p24 protein. although this antiviral was not as efficient as that shown by the photoactive plant thiopene, α-terthienyl, both thiarubrines demonstrated increased activity when the serum component of the virus stock was reduced. This suggested that a component of bovine serum unterfered to some extent with the anti-HIV ativity.     

Absolute metrology by phase and frequency modulation for multiwavelength interferometry

A fiber interferometer for absolute distance measurements is presented whereby wavelength variation is achieved via a sinusoidal strain modulation of a fiber Bragg grating to generate a series of beat wavelengths. The interferometer employs fiber laser sources where the design is based on the use of narrow-bandwidth fiber Bragg gratings. The accuracy of the beat wavelengths is improved compared to the use of multiple wavelengths measured with conventional optical spectrum analyzers or available wavemeters. Initial measurements are presented for beat wavelengths of 254.74 mm and 27.4 m over an optical path difference of 200 mm and 3.8 m, respectively. Combined with a two (or three) wavelength interferometer, this technique has the potential for ultrahigh dynamic range metrology ranging over several meters while preserving subfringe resolution and a low system complexity.     

UV-A-MEDIATED ACTIVITY OF p-METHOXYMETHYLCINNAMATE

Abstract— Methyl esters of hydroxycinnamic acids are photobiologically active. Cis(Z) and trans(E)p-methoxymethyl-cinnamate photosensitize Escherichia coli and Chinese hamster ovary cells. They also produce sister chromatid exchanges. Photosensitization is oxygen independent, and the cinnamates are not genetically active in the absence of light in the Ames Salmonella typhimurium test.     

Properties of combustion waves in a model with competitive exothermic reactions

We study the properties of travelling combustion waves in a diffusional thermal model with a two-step competitive exothermic-exothermic reaction mechanism. This investigation considers the system in one spatial dimension under adiabatic conditions. Based on the notion of the crossover temperature, the model is examined analytically using the activation energy asymptotic method to predict travelling combustion wave behaviour in the limit of large activation energies. The model is then studied numerically using a shooting-relaxation method over a wide range of parameter values, such as those describing the ratios of enthalpies, pre-exponential factors and activation energies. It is demonstrated that the flame speed as a function of these parameters is a single-valued monotonic function and there are two flame regimes identified—each region representing parameter values when one reaction dominates the other.     

Two methods for discretizing a delta function supported on a level set

This paper presents two new methods for discretizing a Dirac delta function which is concentrated on the zero level set of a smooth function u: Rⁿ  R. The function u is only known at the discrete set of points belonging to a regular mesh covering Rⁿ. These two methods are used to approximate integrals over the manifold defined by the level set. Both methods are conceptually simple and easy to implement. We present the results of numerical experiments indicating that as the mesh size h goes to zero, the rate of convergence is at least O(h) for the first method, and O(h²) for the second method. We perform a limited analysis of the proposed algorithms, including a proof of convergence for both methods.     

Antiviral properties of photosensitizers

Abstract— We have studied the antiviral properties of three different groups of photo-sensitizers, viz. (i) various furyl compounds; (ii) β-carboline alkaloids; (iii) thiophenes and their acetylene derivatives. In general the antiviral potency of the furyl compounds correlated with their ability to produce DNA photoadducts. Among the naturally occurring β-carboline alkaloids, harmine was considerably more potent (in the presence of long wavelength UV radiation, UVA) than several other harmane-related compounds. Slight alterations in chemical structure had profound effects on their antiviral activities. Harmine was shown to inactivate the DNA-virus murine cytomegalovirus (MCMV) by inhibiting viral gene expression, although other targets may also exist. Several eudistomins, carboline derivatives isolated from a tunicate, were also photoactive against viruses. Various plant thiophenes and polyacetylenes were studied in detail. These compounds also required UVA for antiviral activity, and some of them were extremely potent against viruses with membranes, e.g. α-terthienyl, which showed significant activity at only 10^-5μg/ml. When MCMV had been treated with α-terthienyl plus UVA, the virus retained its integrity and penetrated cells normally; but the virus did not replicate. More than 30 additional thiophenes have recently been evaluated, including many synthetic ones, and some of these are even more potent than a-terthienyl. We believe that certain thiophenes possess potential therapeutic value and should be tested against model virus infections in animals.