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.     

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.     

The effect of substitution on protonation sites: evidence for protonation at N(3) in N(7)-substituted adenine

Several experimental and theoretical studies have shown that N(1) is the first site for protonation in adenine and N(9)-substituted adenine derivatives. N(7) is considered the site for the second protonation to yield dipositive cations. Results are reported here which indicate that this protonation pattern is altered in N(7)-substituted adenine derivatives. In particular, an X-ray diffraction analysis of the structure of 7-methyladenine dihydrochloride, [C₆N₅H₇]Cl₂, definitively shows that the sites for protonation are N(3), as opposed to N(1), and N(9). Theoretical calculations of the molecular electrostatic potential in various systems suggest that such changes in preferred protonation sites should be expected, in general, when a modification of the molecular structure creates adjacent sites with similar reactivity, such as the N(3) and N(9) sites in 7-methyladenine.     

VISUALIZATION OF ULTRAVIOLET LIGHT-INDUCED THYMINE DIMERS IN DNA BY IMMUNOELECTRON MICROSCOPY

Abstract— To see the damage of DNA due to ultravoilet-B more distinctly, immunoelectron microscopic studies using a monoclonal antibody against cyclobutane-type thymine dimers were performed. As a result, we could detect the existence of thymine dimers on human genomic DNA and _pUC18 plasmid DNA visually. This technique can be useful to locate the photoproducts formed on DNA.