Plants as bioindicators of natural and anthropogenically derived contamination

Plants occupy an important position in the ecosystem, being directly in contact with underlying soil, and providing food for animals, including humans, at higher trophic levels. Their use as indicators in studies of both natural and anthropogenically derived contamination is diverse. The visual appearance of plants, in combination with the presence of particular key species or assemblages, may provide clues to the occurrence of contaminants in the underlying strata. Chemical analysis of plant material, either collected from the field or from laboratory-based plant growth trials, can also provide a measure of the environmental mobility of a contaminant. This article discusses the role of plants as bioindicators with reference to examples of preliminary contaminated land assessment; air pollution monitoring, and studies into the environmental significance of contaminants in domestic and codisposed refuse.     

Newborns' head orientation toward trains of brief sounds

Four experiments assessed the importance of stimulus number, repetition rate, and duration for newborns' head orientation toward brief sounds and related those parameters to the critical ones found for adults. Infants' responses to various trains of repeated 14-ms rattle sounds were compared with those to a 10-s rattle sound, known to elicit head orientation. Directional responses did not differ from the standard when rattle bursts were repeated at a rate of 20 per second for 1 s (experiment 1). Responding did differ from the standard and deteriorated to chance levels when either the number of moderately paced (6/s) stimulus bursts was decreased to six or fewer (experiments 2 and 3) or the duration of rapidly repeated (24/s) bursts was shortened to 500 ms (experiments 4A and 4B). These results suggest that newborns' head orientation depends, in part, upon the number of stimulus bursts and stimulus duration.     

Isopenicillin N synthase mediates thiolate oxidation to sulfenate in a depsipeptide substrate analogue: implications for oxygen binding and a link to nitrile hydratase?

Isopenicillin N synthase (IPNS) is a nonheme iron oxidase that catalyzes the central step in the biosynthesis of beta-lactam antibiotics: oxidative cyclization of the linear tripeptide delta-L-alpha-aminoadipoyl-L-cysteinyl-D-valine (ACV) to isopenicillin N (IPN). The ACV analogue delta-L-alpha-aminoadipoyl-L-cysteine (1-(S)-carboxy-2-thiomethyl)ethyl ester (ACOmC) has been synthesized as a mechanistic probe of IPNS catalysis and crystallized with the enzyme. The crystal structure of the anaerobic IPNS/Fe(II)/ACOmC complex was determined to 1.80 A resolution, revealing a highly congested active site region. By exposing these anaerobically grown crystals to high-pressure oxygen gas, an unexpected sulfenate product has been observed, complexed to iron within the IPNS active site. A mechanism is proposed for formation of the sulfenate-iron complex, and it appears that ACOmC follows a different reaction pathway at the earliest stages of its reaction with IPNS. Thus it seems that oxygen (the cosubstrate) binds in a different site to that observed in previous studies with IPNS, displacing a water ligand from iron in the process. The iron-mediated conversion of metal-bound thiolate to sulfenate has not previously been observed in crystallographic studies with IPNS. This mode of reactivity is of particular interest when considered in the context of another family of nonheme iron enzymes, the nitrile hydratases, in which post-translational oxidation of two cysteine thiolates to sulfenic and sulfinic acids is essential for enzyme activity.     

Self-assembly of Peptide nanotubes in an organic solvent

The self-assembly of a modified fragment of the amyloid beta peptide, based on sequence Abeta(16-20), KLVFF, extended to give AAKLVFF is studied in methanol. Self-assembly into peptide nanotubes is observed, as confirmed by electron microscopy and small-angle X-ray scattering. The secondary structure of the peptide is probed by FTIR and circular dichroism, and UV/visible spectroscopy provides evidence for the important role of aromatic interactions between phenylalanine residues in driving beta-sheet self-assembly. The beta-sheets wrap helically to form the nanotubes, the nanotube wall comprising four wrapped beta-sheets. At higher concentration, the peptide nanotubes form a nematic phase that exhibits spontaneous flow alignment as observed by small-angle neutron scattering.     

Structural study of BSA/poly(ethylene glycol) lipid conjugate complexes

In this work we report the structural characteristics of bovine serum albumin/poly(ethylene glycol) lipid conjugate (BSA/PEG(2000)-PE) complexes under physiological conditions (37 degrees C and pH 7.4) for particular fractions of BSA to PEG-lipid concentration, c(BSA)/c(PEG)(2000)-PE. Ultraviolet fluorescence spectroscopy (UV) results shown that PEG(2000)-PE is associated to BSA, leading to protein unfolding for fixed c(BSA) = 0.01 wt % and variable c(PEG)(2000)-PE = 0.0015-0.6 wt %. Tryptophan groups on the BSA surface are in contact with the PEG-lipid at c(PEG)(2000)-PE = 0.0015 wt %, while they are exposed to water at c(PEG)(2000)-PE > 0.0015 wt %. Dynamic and static light scattering (DLS and SLS) and small-angle neutron scattering (SANS) point out the existence of individual BSA/PEG-lipid complexes in the system for fixed c(BSA) = 1 wt % and variable c(PEG)(2000)-PE = 0.15-2 wt %. DLS shows that there is only one BSA molecule per protein/PEG-lipid complex, while SLS shows that the PEG-lipid associates to the BSA without promoting aggregation between adjacent protein/polymer-lipid conjugate complexes. SANS was used to show that BSA/PEG(2000)-PE complexes adopt an oblate ellipsoidal shape. Partially unfolded BSA is contained in the core of the oblate ellipsoid, which is surrounded by an external shell containing the PEG(2000)-PE.     

Reagent Precoated Targets for Rapid In-Tissue Derivatization of the Anti-Tuberculosis Drug Isoniazid Followed by MALDI Imaging Mass Spectrometry

Isoniazid (INH) is an important component of front-line anti-tuberculosis therapy with good serum pharmacokinetics but unknown ability to penetrate tuberculous lesions. However, endogenous background interferences hinder our ability to directly analyze INH in tissues. Chemical derivatization has been successfully used to measure isoniazid directly from tissue samples using matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS). MALDI targets were pretreated with trans-cinnamaldehyde (CA) prior to mounting tissue slices. Isoniazid present in the tissues was efficiently derivatized and the INH-CA product measured by MS/MS. Precoating of MALDI targets allows the tissues to be directly thaw-mounted and derivatized, thus simplifying the preparation. A time-course series of tissues from tuberculosis infected/INH dosed animals were assayed and the MALDI MS/MS response correlates well with the amount of INH determined to be in the tissues by high-performance liquid chromatography (HPLC)-MS/MS.     

Therapeutic plasma proteins--application of proteomics in process optimization, validation, and analysis of the final product

An overview is given on the application of proteomic technology in the monitoring of different steps during the production of therapeutic proteins from human plasma. Recent advances in this technology enable the use of proteomics as an advantageous tool for the validation of already existing processes, the development and fine tuning of new production steps, the characterization and quality control of final products, the detection of both harmful impurities and modifications of the therapeutic protein and the auditing of batch-to-batch variations. Further, use of proteomics for preclinical testing of new products, which can be either recombinant or plasma-derived, is also discussed.     

Lipid binding interactions of antimicrobial plant seed defence proteins: puroindoline-a and β-purothionin

The indolines and thionins are basic, amphiphilic and cysteine-rich proteins found in cereals; puroindoline-a (Pin-a) and β-purothionin (β-Pth) are members of these families in wheat (Triticum aestivum). Pin-a and β-Pth have been suggested to play a significant role in seed defence against microbial pathogens, making the interaction of these proteins with model bacterial membranes an area of potential interest. We have examined the binding of these proteins to lipid monolayers composed of 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (DPPG) using a combination of neutron reflectometry, Brewster angle microscopy, and infrared spectroscopy. Results showed that both Pin-a and β-Pth interact strongly with condensed phase DPPG monolayers, but the degree of penetration was different. β-Pth was shown to penetrate the lipid acyl chain region of the monolayer and remove lipids from the air/liquid interface during the adsorption process, suggesting this protein may be able to both form membrane spanning ion channels and remove membrane phospholipids in its lytic activity. Conversely, Pin-a was shown to interact mainly with the head-group region of the condensed phase DPPG monolayer and form a 33 ? thick layer below the lipid film. The differences between the interfacial structures formed by these two proteins may be related to the differing composition of the Pin-a and β-Pth hydrophobic regions.     

Bisubstrate adenylation inhibitors of biotin protein ligase from Mycobacterium tuberculosis

The mycobacterial biotin protein ligase (MtBPL) globally regulates lipid metabolism in Mtb through the posttranslational biotinylation of acyl coenzyme A carboxylases involved in lipid biosynthesis that catalyze the first step in fatty acid biosynthesis and pyruvate coenzyme A carboxylase, a gluconeogenic enzyme vital for lipid catabolism. Here we describe the design, development, and evaluation of a rationally designed bisubstrate inhibitor of MtBPL. This inhibitor displays potent subnanomolar enzyme inhibition and antitubercular activity against multidrug resistant and extensively drug resistant Mtb strains. We show that the inhibitor decreases in?vivo protein biotinylation of key enzymes involved in fatty?acid biosynthesis and that the antibacterial activity is MtBPL dependent. Additionally, the gene encoding BPL was found to be essential in M.?smegmatis. Finally, the X-ray cocrystal structure of inhibitor bound MtBPL was solved providing detailed insight for further structure-activity analysis. Collectively, these data suggest that MtBPL is a promising target for further antitubercular therapeutic development.