Decorated Core-Shell Architectures: Influence of the Dimensional Properties on Hybrid Resonances

Emerging nanoplasmonics utilizing asymmetric core-shell architectures present opportunities to precisely control the plasmon position and signal amplification within a single particle. In particular, asymmetric gold nanorods, assembled into a “matryoshka” structure (gold nanorod core, silica spacer shell, and outer gold shell) have the unique ability to enhance and precisely manipulate the plasmonic signature when compared to single gold nanorods via the generation of hybridized plasmonic modes. Currently, the fundamental understanding of the impact of the gold nanorod matryoshka dimensional parameters on the subsequent resonance behavior is incomplete. In this work, we elucidate the structural-hybridized resonance relationship of gold nanorod nanomatryoshka designs by experimentally varying the key geometrical properties; including silica spacer thickness, gold nanorod core size, and gold shell thickness/continuity.     

Bifunctional glycosyltransferases catalyze both extension and termination of pectic galactan oligosaccharides

Pectins are the most complex polysaccharides of the plant cell wall. Based on the number of methylations, acetylations and glycosidic linkages present in their structures, it is estimated that up to 67 transferase activities are involved in pectin biosynthesis. Pectic galactans constitute a major part of pectin in the form of side‐chains of rhamnogalacturonan‐I. In Arabidopsis, galactan synthase 1 (GALS1) catalyzes the addition of galactose units from UDP‐Gal to growing β‐1,4‐galactan chains. However, the mechanisms for obtaining varying degrees of polymerization remain poorly understood. In this study, we show that AtGALS1 is bifunctional, catalyzing both the transfer of galactose from UDP‐α‐d ‐Gal and the transfer of an arabinopyranose from UDP‐β‐l ‐Ara_p to galactan chains. The two substrates share a similar structure, but UDP‐α‐d ‐Gal is the preferred substrate, with a 10‐fold higher affinity. Transfer of Ara_p to galactan prevents further addition of galactose residues, resulting in a lower degree of polymerization. We show that this dual activity occurs both in vitro and in vivo. The herein described bifunctionality of AtGALS1 may suggest that plants can produce the incredible structural diversity of polysaccharides without a dedicated glycosyltransferase for each glycosidic linkage.     

Identification of a Gene (GPR30) with Homology to the G-Protein-Coupled Receptor Superfamily Associated with Estrogen Receptor Expression in Breast Cancer

Using the technique of differential cDNA library screening, a cDNA clone was isolated from an estrogen receptor (ER)-positive breast carcinoma cell line (MCF7) cDNA library based upon the overexpression of this gene compared to an ER-negative cell line (MDA-MB-231). Sequence analysis of this clone determined that it shared significant homology to G-protein-coupled receptors. This receptor, GPCR-Br, was abundantly expressed in the ER-positive breast carcinoma cell lines MCF7, T-47D, and MDA-MB-361. Expression was absent or minimal in the ER-negative breast carcinoma cell lines BT-20, MDA-MB-231, and HBL-100. GPCR-Br was ubiquitously expressed in human tissues examined but was most abundant in placenta. GPCR-Br expression was examined in 11 primary breast carcinomas. GPCR-Br was detected in all 4 ER-positive tumors and only 1 of 7 ER-negative tumors. Based upon PCR analysis in hybrid cell lines, the gene for GPCR-Br (HGMW-approved symbol GPR30) was mapped to chromosome 7p22. The pattern of expression of GPCR-Br indicates that this receptor may be involved in physiologic responses specific to hormonally responsive tissues.     

Quantitative analysis of CryIA(b) expression in Bt maize plants,tissues, and silage and stability of expression over successive generations

The range and stability of expression of the transgenic CryIA(b) protein was examined in Ciba Seeds Bt maize plants derived from Event 176. Specifically, CryIA(b) levels were determined for: (1) various plant tissues and developmental stages in three maize lines from 1993 field tests; (2) pollen and leaves from plants representing four backcross generations of two genotypes; (3) leaves of 6 precommercial hybrids; and (4) silage from one Bt maize hybrid. Significant levels were found only in pollen and leaves. Genetic background did not greatly impact the level seen in either tissue. CryIA(b) expression in maize plants derived from transformation Event 176 was stable over at least four successive generations. On a per acre basis, the highest amount of CryIA(b) protein (estimated to be 2-4 g CryIA(b) protein/acre) was found to occur at anthesis, consistent with the stage at which maximum plant vegetative biomass is reached. CryIA(b) was not detected in silage prepared from CryIA(b)-expression plants. The maize-expressed CryIA(b) protein was found to have the expected size and to be immunoreactive with antibodies prepared against crystals from Bacillus thuringiensis subsp. kurstaki.     

Carbon-13 Nuclear Magnetic Resonance Study of Metabolism of Propionate by Escherichia coli

We have evaluated the use of [1,2-13C2]propionate for the analysis of propionic acid metabolism, based on the ability to distinguish between the methylcitrate and methylmalonate pathways. Studies using propionate-adapted Escherichia coli MG1655 cells were performed. Preservation of the 13C-13C-12C carbon skeleton in labeled alanine and alanine-containing peptides involved in cell wall recycling is indicative of the direct formation of pyruvate from propionate via the methylcitrate cycle, the enzymes of which have recently been demonstrated in E. coli. Additionally, formation of 13C-labeled formate from pyruvate by the action of pyruvate-formate lyase is also consistent with the labeling of pyruvate C-1. Carboxylation of the labeled pyruvate leads to formation of [1,2-13C2]oxaloacetate and to multiply labeled glutamate and succinate isotopomers, also consistent with the flux through the methylcitrate pathway, followed by the tricarboxylic acid (TCA) cycle. Additional labeling of TCA intermediates arises due to the formation of [1-13C]acetyl coenzyme A from the labeled pyruvate, formed via pyruvate-formate lyase. Labeling patterns in trehalose and glycine are also interpreted in terms of the above pathways. The information derived from the [1, 2-13C2]propionate label is contrasted with information which can be derived from singly or triply labeled propionate and shown to be more useful for distinguishing the different propionate utilization pathways via nuclear magnetic resonance analysis.     

The KRAS-regulated kinome identifies WEE1 and ERK coinhibition as a potential therapeutic strategy in KRAS-mutant pancreatic cancer

Oncogenic KRAS drives cancer growth by activating diverse signaling networks, not all of which have been fully delineated. We set out to establish a system-wide profile of the KRAS-regulated kinase signaling network (kinome) in KRAS-mutant pancreatic ductal adenocarcinoma (PDAC). We knocked down KRAS expression in a panel of six cell lines and then applied multiplexed inhibitor bead/MS to monitor changes in kinase activity and/or expression. We hypothesized that depletion of KRAS would result in downregulation of kinases required for KRAS-mediated transformation and in upregulation of other kinases that could potentially compensate for the deleterious consequences of the loss of KRAS. We identified 15 upregulated and 13 downregulated kinases in common across the panel of cell lines. In agreement with our hypothesis, all 15 of the upregulated kinases have established roles as cancer drivers (e.g., SRC, TGF-β1, ILK), and pharmacological inhibition of one of these upregulated kinases, DDR1, suppressed PDAC growth. Interestingly, 11 of the 13 downregulated kinases have established driver roles in cell cycle progression, particularly in mitosis (e.g., WEE1, Aurora A, PLK1). Consistent with a crucial role for the downregulated kinases in promoting KRAS-driven proliferation, we found that pharmacological inhibition of WEE1 also suppressed PDAC growth. The unexpected paradoxical activation of ERK upon WEE1 inhibition led us to inhibit both WEE1 and ERK concurrently, which caused further potent growth suppression and enhanced apoptotic death compared with WEE1 inhibition alone. We conclude that system-wide delineation of the KRAS-regulated kinome can identify potential therapeutic targets for KRAS-mutant pancreatic cancer.     

Pathogens promote plant diversity through a compensatory response

Pathogens are thought to promote diversity in plant communities by preventing competitive exclusion. Previous studies have focussed primarily on single-plant, single-pathogen interactions, yet the interactions between multiple pathogens and multiple hosts may have non-additive impacts on plant community composition. Here, we report that both a bacterial and a fungal pathogen maintained the diversity of a four-species plant community across five generations; however, significant interactions between the pathogens resulted in less plant diversity when the two pathogens were present than when the fungal pathogen was present alone. Standard models predict that pathogens will maintain plant diversity when they cause a disproportionate loss of fitness in the dominant plant species. In our experiment, however, pathogens maintained plant diversity because the rare species produced more seeds through a compensatory response to pathogen infection. Finally, we found that the influence of pathogens on maintaining plant diversity was 5.5 times greater than the influence of nutrient resource heterogeneity. Pathogens may be a major factor in maintaining plant diversity, and our findings emphasize the importance of investigating the roles of pathogens in natural plant communities.