Descripción: The phytochemical study of two species of Jaborosa caulescens (var. caulescens and var. bipinnatifida) yielded the four new withanolides 1-4. The structures of the new compounds were determined using a combination of spectroscopic techniques (including 1D and 2D NMR) and Molecular Modeling.

Descripción: We present a detailed structural and surface-enhanced Raman scattering (SERS) study of poly(allylamine) modified with Os (byp)2 ClPyCHO (PAH-Os) and gold nanoparticles self-assembled multilayers [PAH-Os+ (Au-nanoparticlesPAH-Os)n, n=1 and 5]. Atomic force microscopy and variable-angle spectroscopic ellipsometry measurements indicate that the first nanoparticle layer grows homogenously by partially covering the substrate without clustering. Analyzing the sample thickness and roughness we infer that the growth process advances thereafter by filling with nanoparticles the interstitial spaces between the previously adsorbed nanoparticles. After five immersion steps the multilayers reach a more compact structure. The interaction between plasmons of near-gold nanoparticles provides a new optical absorption around 650 nm which, in addition, allows a more effective SERS process in that spectral region than at the single-plasmon resonance (∼530 nm). We compare the electronic resonance Raman and SERS amplification mechanisms in these self-assembled multilayers analyzing Raman resonance scans and Raman intensity micromaps. As a function of nanoparticle coverage we observe large changes in the Raman intensity scans, with maxima that shift from the electronic transitions, to the plasmon resonance, and finally to the coupled-plasmon absorption. The Raman micromaps, on the other hand, evidence huge intensity inhomogeneities which we relate to "hot spots." Numerical discrete dipole approximation calculations including the interaction between gold nanoparticles are presented, providing a qualitative model for the coupled-plasmon absorption and redshifted Raman hot spots in these samples. © 2005 American Institute of Physics.

Descripción: The title compounds, tetraphenylphosphonium chlorobis(diethyldithiocarbamato-S,S)cadmium(II), (C24H20P)-[CdCl(C5H10NS 2)2], (1), and tetraphenylphosphonium bromobis(diethyldithiocarbamato-S,S)cadmium(II), (C24-H20P)[CdBr(C5H10NS 2)2], (2), are isomorphous. The compexes are mononuclear with coordination spheres of the types S4Cl and S4Br, respectively. The central Cd atom is linked to four S atoms and two bidentate dithiocarbamate ligands and to the halide atom. The resulting Cd-atom coordination geometry is halfway between trigonal bipyrimidal and square pyramidal. Principal dimensions include: Cd-S 2.573 (1)-2.682 (1) in (1) and 2.571 (3)-2.736 (2) Å in (2); Cd-Cl and Cd-Br 2.462 (1) and 2.626 (1) Å, respectively.

Descripción: By taking advantage of the extreme stability of a protein-DNA complex, we have obtained two highly specific monoclonal antibodies against a predetermined palindromic DNA sequence corresponding to the binding site of the E2 transcriptional regulator of the human papillomavirus (HPV-16). The purified univalent antibody fragments bind to a double-stranded DNA oligonucleotide corresponding to the E2 binding site in solution with dissociation constants in the low and subnanomolar range. This affinity matches that of the natural DNA binding domain and is severalfold higher than the affinity of a homologous bovine E2 C-terminal domain (BPV-1) for the same DNA. These antibodies discriminate effectively among a number of double- and single-stranded synthetic DNAs with factors ranging from 125-to 20,000-fold the dissociation constant of the specific DNA sequence used in the immunogenic protein-DNA complex. Moreover, they are capable of fine specificity tuning, since they both bind less tightly to another HPV-16 E2 binding site, differing in only 1 base pair in a noncontact flexible region. Beyond the relevance of obtaining a specific anti-DNA response, these results provide a first glance at how DNA as an antigen is recognized specifically by an antibody. The accuracy of the spectroscopic method used for the binding analysis suggests that a detailed mechanistic analysis is attainable.

Descripción: Aims: To evaluate the antagonistic activity of Fusarium oxysporum nonpathogenic fungal strain S6 against the phytopathogenic fungus Sclerotinia sclerotiorum and to identify the antifungal compounds involved. Methods and Results: The antagonistic activity of Fusarium oxysporum strain S6 was determined in vitro by dual cultures. The metabolite responsible for the activity was isolated by chromatographic techniques, purified and identified by spectroscopic methods as cyclosporine A. The antifungal activity against the pathogen was correlated with the presence of this metabolite by a dilution assay and then quantified. Cyclosporine A caused both growth inhibition and suppression of sclerotia formation. In a greenhouse assay, a significant increase in the number of surviving soybean (Glycine max) plants was observed when S. sclerotiorum and F. oxysporum (S6) were inoculated together when compared with plants inoculated with S. sclerotiorum alone. Conclusion: Fusarium oxysporum (S6) may be a good fungal biological control agent for S. sclerotiorum and cyclosporine A is the responsible metabolite involved in its antagonistic activity in vitro. Significance and Impact of the Study: Cyclosporine A has not been previously described as an inhibitor of S. sclerotiorum. Its minimum inhibitory concentration (MIC) of 0·1 μg disc-1 makes it suitable to use as a biofungicide. In vivo experiments showed that F. oxysporum (S6) is a good candidate for the biocontrol of S. sclerotiorum in soybean. © 2006 The Society for Applied Microbiology.