Structure and enantioselective synthesis of polyamine toxin MG30 from the venom of the spider Macrothele gigas

A novel polyamine toxin, named MG30, was isolated from the venom of the spider, Macrothele gigas, and its structure was elucidated by two-dimensional NMR and mass analysis. In addition, the enantioselective synthesis of MG30 was achieved to assign its absolute stereochemistry.     

Preconcentration Systems Using Polyurethane Foam/Me-BDBD for Determination of Copper in Food Samples

A new reagent, 6-[2′-(6′-methyl-benzothiazolylazo)]-1,2-dihydroxy-3,5-benzenedisulfonic acid (Me-BDBD), was synthesised and used in on-line and off-line systems for copper preconcentration by solid-phase extraction. Spectrophotometry and Flame Atomic Absorption Spectrometry (FAAS) were the detection techniques. Polyurethane foam loaded with Me-BDBD packed in a minicolumn was used as sorbent in both systems. The spectral characteristics of Me-BDBD were investigated. The optimum pH values for maximum sorption of the metal are between 7.0 and 8.5. Copper was desorbed with 0.05 and 0.50 mol L⁻¹ hydrochloric acid solutions, for on-line and off-line systems, respectively. The effects of several foreign substances on the adsorption of copper are reported. The enrichment factors obtained were 7 (on-line) and 26 (off-line) for the systems. The proposed procedures allowed the determination of copper with detection limits of 3.4 and 1.4 μg L⁻¹ (0.85 and 0.35 μg per gram of sample) for on-line and off-line systems, respectively. The precision of the procedures was also calculated: 3.2 (on-line) and 1.9% (off-line). The validation of the procedures was carried out by analysis of certified reference material. The copper contents in corn and rice flour and black tea samples were determined by applying the proposed procedures.     

Nanoanalysis of the arthropod neuro-toxins

Many kinds of venomous principles modulate physiological responses of mammalian signal transduction systems, on which they act selectively as enhancers, inhibitors or some other kind of effectors. These toxins become useful tools for physiological research. We have employed and characterized paralyzing toxins from the venom of spiders, insects and scorpions with a limited supply. We have developed rapid and sensitive mass spectrometric technology and applied for the identification of these toxins. Venom profiles are screened by MALDI-TOF fingerprinting analysis prior to purification of venomous components, then marked target toxins of small molecular mass (1000–5000) are characterized directly by means of mass spectrometric techniques such as Frit-FAB MS/MS, CID/PSD-TOF MS, Capil.-HPLC/Q-TOF MS/MS etc.     

Generalized Fourier transform and its application to the volume integral equation for elastic wave propagation in a half space

In the present study, a generalized Fourier transform for time harmonic elastic wave propagation in a half space is developed. The generalized Fourier transform is obtained from the spectral representation of the operator derived from the elastic wave equation. By means of the generalized Fourier transform, a volume integral equation method for the analysis of scattered elastic waves is presented. The proposed method is based on the Krylov subspace iteration technique. During the iterative process, the discrete generalized Fourier transform is used, where the derivation of a huge and dense matrix from the volume integral equation is not necessary.     

A fast volume integral equation method for the direct/inverse problem in elastic wave scattering phenomena

A fast method for solving the volume integral equation is introduced for the solution of forward and inverse multiple scattering problems in an elastic 3-D full space. For both forward and inverse scattering analysis, the volume integral equation in the wavenumber domain is used. By means of the discrete Fourier transform, the volume integral equation in the wavenumber domain can be dealt with as a Fredholm equation of the 2nd kind with respect to a non-Hermitian operator on a finite dimensional vector space. The Bi-CGSTAB method is employed to construct the Krylov subspace in the wavenumber domain. The current procedure establishes a fast and simplified method without requiring the derivation of a coefficient matrix. Several numerical results validate the accuracy and effectiveness of the current method for both forward and inverse scattering analysis. According to the numerical results, the reconstruction of inhomogeneities of the wave field is successful, even for multiple scattering of several cubes.     

Complete eigenfunction expansion form of the Green's function for elastic layered half-space

Summary  The complete eigenfunction expansion form of the Green's function for a 3-D elastic layered half-space in the frequency domain is derived in this paper. The expression of the Green's function presented here is an extension of that represented by the residue terms and the branch line integrals given by Lamb [1]. The present expression, however, clarifies the mathematical common frame between the residue terms and the branch line integrals with respect to the eigenfunctions and energy integrals. For the derivation, the concept of an energy integral for the improper eigenfunctions is newly developed. The improper eigenfunctions, which can be found in the wavenumbers for the branch cuts, are not in L ₂ space, so the definition of the energy integral requires some treatment. The energy integral is defined as the limit of the inner product of the improper eigenfunction and the definition function of the improper eigenfunction, for which the inner product remains finite. Via the definition of the energy integral, the kernel of the branch line integral is decomposed into the improper eigenfunction, and the complete eigenfunction expansion form of the Green's function is derived. The Green's function can thus be expressed by summation of normal modes, complex modes pointed out in [2], the integral of the improper eigenfunction and the residue at k=0 due to the singularity of the horizontal wavefunction. Received 3 May 2001; accepted for publication 23 August 2001     

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and high-performance liquid chromatography study of quantitative and qualitative variation in tarantula spider venoms

Animal venoms are important sources of novel pharmacological tools, useful in biochemical characterization of their receptors. Venom quality control, batch-to-batch homogeneity and high reproducibility of venom fractionation and toxin purification are crucial issues for biochemical and pharmacological studies. To address these issues, a study of the variability of tarantula spider venom samples was undertaken. Venom profiles of samples collected from individuals of different age and sex, and from sibling spiders of the same species, were generated by high-performance liquid chromatography (HPLC) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and analyzed to assess venom variability and method accuracy. Sex-linked venom variation was studied on eight species. Clear qualitative differences were observed for six out of eight species, as well as quantitative differences. Age-related variation studied in Poecilotheria rufilata showed essentially age-related quantitative differences between adults of both sexes and immature juveniles. The venoms of nine siblings and three wild-collected Pterinochilus murinus were studied for individual variation, showing only very minor quantitative differences. On the same samples, the quality of MALDI-TOFMS venom fingerprinting was demonstrated to be highly reproducible. Our results show that tarantula venom peptide fingerprinting is a highly reliable identification method, that pooled batches of venom from several animals can be used for venom purification, that venom composition does not appear to be qualitatively related to ontogenesis in the spiders studied, and that qualitative sex-linked variation occurs across most species and may be important in activity studies.