Schematic depiction of the differences in the availability/recovery of a putative chemical to a competing species from a given amount of chemical produced and released from a plant in <i>in vitro</i> assays as compared to <i>in situ</i> assays that include soil and the associated microbial (bulk and rhizosphere) communities.

<p>Sorption of chemicals onto soil particles, chemical decomposition and/or microbial degradation of chemicals are major mechanisms that influence their ability to accumulate to phytotoxic levels and influence the growth of neighboring target plants <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004700#pone.0004700-Huang1" target="_blank">[13]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004700#pone.0004700-Inderjit7" target="_blank">[40]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004700#pone.0004700-Inderjit8" target="_blank">[41]</a>. Sometimes physical sorption of a chemical on soil particles can actually concentrate the chemical to a level that may become physiologically active. Therefore, sorption may affect allelopathy both negatively and positively.</p

m-Tyrosine recovery (%) from m-tyrosine treated non-sterile soil with seedlings of lettuce, littleseed canarygrass or bamboo.

<p>Shared letters indicate no significant differences in mean m-tyrosine recovery from the soils of the three assay species as determined by one-way ANOVAs, and post ANOVA Tukey test (P<0.05).</p

Microbial activity as indicated by CO₂ release (µg CO₂ released/g soil/h) of soil treated with 0, 4.25, 8.5, 17, 34, 68 or 136 µg m-tyrosine/g soil, incubated at 22 or 30°C.

<p>Error bars indicate 1 SE. Values in parenthesis indicate % recovery of m-tyrosine in soil.</p

m-Tyrosine (µg/g soil) recovery from non-sterile or sterile soil treated with 0, 4.25, 8.5, 17, 34, 68 or 136 µg m-tyrosine/g soil and incubated at 22 or 30°C.

<p>Error bars indicate 1 SE.</p

Self-Association Behavior of a <i>Novel</i> Nonproteinogenic β‑Strand-<i>Mimic</i> in an Organic Solvent

The self-association behavior of a newly characterized β-strand-<i>mimic</i>, presented by an achiral nonproteinogenic model system Boc-γ-Abz-NHMe (<b>1</b>: Boc = <i>tert</i>-butyloxycarbonyl; γ-Abz = γ-aminobenzoic acid; NHMe = <i>N</i>-methylamide), have been investigated using ¹H NMR and FT-IR absorption spectroscopy, in combination with computational ab initio calculations. The concentration dependence of ¹H NMR chemical shifts of the amide-NHs in CDCl₃ exhibited noncooperative behavior of self-association, whereas the variable temperature ¹H NMR chemical shifts data of the amide-NHs, i.e., temperature-coefficient (Δδ/Δ<i>T</i>) values, could be accounted for by significant enhancement of self-association, i.e., aggregates higher than dimers. In the absence of N–H···O intramolecular H-bond in <b>1</b>, the intense FT-IR absorption bands in informative amide-A region, i.e., N–H stretches at ∼3465 and 3438 cm^–1 in chloroform solution, could be interpreted in terms of intermolecular H-bonding. The ab initio quantum mechanical calculations performed on two discrete isolated antiparallel H-bonded duplexes with a face-to-face and an edge-to-edge aromatic–aromatic interaction provided strong support for their relative importance to stabilize favorable dimeric structures. The thermodynamic parameters deduced from van’t Hoff plots, constructed from variable temperature ¹H NMR data of the amide-NHs in CDCl₃, also substantiated the effectiveness of aromatic–aromatic interactions for dimer formation and higher-order self-association. In view of the enormous structural importance of β-strand-<i>like</i> building blocks in peptide design, we highlight intrinsic self-associating potentials of the readily available γ-Abz moiety, besides the fact that such planar secondary structural <i>mimics</i> are presumed to offer greater prospective for constructing <i>peptidomimetics</i> and therapeutically relevant small molecules

Confirmation of adherent GBM BTIC cultures.

<p>Adherent GBM BTICs were prepared and subjected to (A) immunoassays, (B and C) immunocytochemistry, and (D) plating on non-adherent conditions to confirm their stem cell properties. GBM BTICs strongly expressed neural stem cell markers, nestin and Sox-2, by both (A) immunoblotting and (B and C) immunocytochemistry. BTICs formed neurospheres when plated in non-adherent conditions (D).</p

Intracellular calcium imaging in GBM BTICs in response to AMPA receptor stimulation.

<p>AMPA stimulation results in increased intracellular calcium levels in GBM BTICs. Cell morphology in 1.2 mM Ca⁺² HBSS before and 10 minutes after AMPA and CYTZ stimulation showed no changes in cell morphology (A and B, respectively). Calcium levels 10 minutes after 100 µM AMPA and 100 µM CYTZ stimulation showed increase in intracellular calcium concentrations well exceeding 500 µM, suggesting that surface AMPA receptors on GBM BTICs are functional and conduct calcium currents (C and D, false color calcium images before and 10 minutes after calcium stimulation, respectively). The calcium concentrations color-coding is provided by the color scale on the right.</p

Expression of calcium-permeable AMPA receptor subunits in GBM BTICs.

<p>GBM BTICs strongly express calcium-permeable subunits of AMPA receptor (GluR1 and GluR4) compared to non-stem tumor cells (Primary GBM Cultures) and established GBM cell line U251 (A). Normal mouse brain homogenate (postive control) expressed both GluR1 and GluR4. To confirm that these calcium-permeable AMPA receptors are expressed on the surface membrane, GBM BTICs were stained with N-terminus GluR1 antibody under non-permeabilized condition (B). Compared to negative controls (C), GluR1 stained the surface membranes of BTICs. α-tubulin was stained after permeabilizing the membrane as a postive control (D).</p

Community Impacts of <em>Prosopis juliflora</em> Invasion: Biogeographic and Congeneric Comparisons

<div><p>We coordinated biogeographical comparisons of the impacts of an exotic invasive tree in its native and non-native ranges with a congeneric comparison in the non-native range. <em>Prosopis juliflora</em> is taxonomically complicated and with <em>P. pallida</em> forms the <em>P. juliflora</em> complex. Thus we sampled <em>P. juliflora</em> in its native Venezuela, and also located two field sites in Peru, the native range of <em>Prosopis pallida.</em> Canopies of <em>Prosopis juliflora</em>, a native of the New World but an invader in many other regions, had facilitative effects on the diversity of other species in its native Venezuela, and <em>P. pallida</em> had both negative and positive effects depending on the year, (overall neutral effects) in its native Peru. However, in India and Hawaii, USA, where <em>P. juliflora</em> is an aggressive invader, canopy effects were consistently and strongly negative on species richness. <em>Prosopis cineraria</em>, a native to India, had much weaker effects on species richness in India than <em>P. juliflora</em>. We carried out multiple congeneric comparisons between <em>P. juliflora</em> and <em>P. cineraria</em>, and found that soil from the rhizosphere of <em>P. juliflora</em> had higher extractable phosphorus, soluble salts and total phenolics than <em>P. cineraria</em> rhizosphere soils. Experimentally applied <em>P. juliflora</em> litter caused far greater mortality of native Indian species than litter from <em>P. cineraria</em>. <em>Prosopis juliflora</em> leaf leachate had neutral to negative effects on root growth of three common crop species of north-west India whereas <em>P. cineraria</em> leaf leachate had positive effects. <em>Prosopis juliflora</em> leaf leachate also had higher concentrations of total phenolics and L-tryptophan than <em>P. cineraria,</em> suggesting a potential allelopathic mechanism for the congeneric differences. Our results also suggest the possibility of regional evolutionary trajectories among competitors and that recent mixing of species from different trajectories has the potential to disrupt evolved interactions among native species.</p> </div

<i>Prosopis juliflora</i> in its native range of Venezuela (A); the invaded range of Haryana, India (B), along the National Highway to Rajasthan (C), at the boundaries of an agricultural field in India (D), and in Hawaii, USA (E); <i>Prosopis cineraria</i> in its native range, Rajasthan, India (F).

<p>Photo credits: Pascual J. Soriano (A); Inderjit (B, C, D and F) and Timothy J. Gallaher (E).</p