By live-monitoring Cu and Cu2O Bragg peaks from the surface of a polycrystalline Cu electrode while scanning from open-circuit potential to CO reduction potentials, we show that the near-surface ...region is fully converted to the metallic phase at approximately +0.3 V vs RHE.
4-Hydroxyphenylpyruvate dioxgenase (HPPD) enzymes from rat and from several plants contained only about a single inhibitor-binding active site per dimer which matched the content of iron in the ...purified Arabidopsis thaliana and Avena sativa enzymes. The dimeric HPPDs were about 10 fold more catalytically active than the tetrameric P. fluorescens enzyme with kcat/KmHPP values ranging from 0.8 to 2.5 s-1 μM-1. Most were also highly sensitive to herbicides with, for example, Ki values for mesotrione ranging from 25 to 100 pM. Curiously HPPDs from cool climate grasses were much less herbicide-sensitive. When likewise expressed in Nicotinia tabacum, Avena sativa HPPD, Ki value of 11 nM for mesotrione, conferred far greater tolerance to mesotrione (CallistoTM) than did any of the more sensitive HPPDs. Targeted mutagenesis of the Avena HPPD led to the discovery of 4 mutations imparting improved inherent tolerance, defined as the ratio of Ki to KmHPP, by about 16 fold without any loss of catalytic activity. The Nicotinia line with the highest expression of this quadruple mutant exhibited substantial resistance even up to a 3 kg/ha post-emergence application of mesotrione. The maximum observed expression level of heterologous plant HPPDs in tobacco was ca. 0.35% of the total soluble protein whereas the endogenous tobacco HPPD constituted only ca. 0.00075%. At such high expression even HPPDs with impaired catalytic activity could be effective. A quintuple mutant Avena sativa HPPD conferred substantial tolerance across a broad range of HPPD herbicide chemistries despite being only ca. 5 % as catalytically active as the wild type enzyme. Testing various wild type and mutant HPPDs in tobacco revealed that tolerance to field rates of herbicide generally requires about two order of magnitude increases in both inherent herbicide tolerance and expression relative to endogenous levels. This double hurdle may explain why target-site based resistance to HPPD-inhibiting herbicides has been slow to evolve in weeds.
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•HPPD enzymes were found to contain only a single inhibitor-binding site per dimer.•Ki values for mesotrione of dimeric HPPDs generally ranged from 25 to 100 pM.•The Ki value for mesotrione of the HPPD from Avena sativa was 11 nM.•A mutant Avena HPPD conferred high level transgenic mesotrione tolerance.•HPPD transgenes expressed in tobacco hundreds of fold above endogenous levels.
In Arabidopsis thaliana we demonstrate that dying root hairs provide an easy and rapid in vivo model for the morphological identification of apoptotic-like programmed cell death (AL-PCD) in plants. ...The model described here is transferable between species, can be used to investigate rates of AL-PCD in response to various treatments and to identify modulation of AL-PCD rates in mutant/transgenic plant lines facilitating rapid screening of mutant populations in order to identify genes involved in AL-PCD regulation.
We present a joint theoretical–experimental study of CO coverage and facet selectivity on Au under electrochemical conditions. With in situ attenuated total reflection surface-enhanced IR ...spectroscopy, we investigate the CO binding in an electrochemical environment. At 0.2 V versus SHE, we detect a CO band that disappears upon facet-selective partial Pb underpotential deposition (UPD), suggesting that Pb blocks certain CO adsorption sites. With Pb UPD on single crystals and theoretical surface Pourbaix analysis, we eliminate (111) terraces as a possible adsorption site of CO. Ab initio molecular dynamics simulations of explicit water on the Au surface show the adsorption of CO on (211) steps to be significantly weakened relative to the (100) terrace due to competitive water adsorption. This result suggests that CO is more likely to bind to the (100) terrace than (211) steps in an electrochemical environment, even though Au steps under gas-phase conditions bind CO* more strongly. The competition between water and CO adsorption can result in different binding sites for CO* on Au in the gas phase and electrochemical environments.
The establishment of the legume-rhizobia symbiosis between Medicago spp. and Sinorhizobium meliloti is dependent on the production of sulfated lipo-chitooligosaccharidic nodulation (Nod) factors by ...the bacterial partner. In this article, using a biochemical approach to characterize putative Nod factor receptors in the plant host, we describe a high-affinity binding site (Ksubscript d = 0.45 nM) for the major Nod factor produced by S. meliloti. This site is termed Nod factor-binding site 3 (NFBS3). NFBS3 is associated to a high-density fraction prepared from roots of Medicago truncatula and shows binding specificity for lipo-chitooligosaccharidic structures. As for the previously characterized binding sites (NFBS1 and NFBS2), NFBS3 does not recognize the sulfate group on the S. meliloti Nod factor. Studies of Nod factor binding in root extracts of early symbiotic mutants of M. truncatula reveals that the new site is present in Nod factor perception and does not make infections 3 (dmi3) mutants but is absent in dmi1 and dmi2 mutants. Roots and cell cultures of all these mutants still contain sites similar to NFBS1 and NFBS2, respectively. These results suggest that NFBS3 is different from NFBS2 and NFBS1 and is dependent on the common symbiotic genes DMI1 and DMI2 required for establishment of symbioses with both rhizobia and arbuscular mycorrhizal fungi. The potential role of this site in the establishment of root endosymbioses is discussed.
Purpose
Laparoscopic hiatal hernia repair with additional fundoplication is a commonly recommended standard surgical treatment for symptomatic large hiatal hernias with paraesophageal involvement ...(PEH). However, due to the risk of persistent side effects, this method remains controversial. Laparoscopic mesh-augmented hiatoplasty without fundoplication (LMAH), which combines hiatal repair and mesh reinforcement, might therefore be an alternative.
Methods
In this retrospective study of 55 (25 male, 30 female) consecutive PEH patients, the perioperative course and symptomatic outcomes were analyzed after a mean follow-up of 72 months.
Results
The mean DeMeester symptom score decreased from 5.1 to 1.8 (
P
< 0.001) and the gas bloating value decreased from 1.2 to 0.5 (
P
= 0.001). The dysphagia value was 0.7 before surgery and 0.6 (
P
= 0.379) after surgery. The majority of the patients were able to belch and vomit (96 and 92 %, respectively). Acid-suppressive therapy on a regular basis was discontinued in 68 % of patients. In 4 % of patients, reoperation was necessary due to recurrent or persistent reflux. A mesh-related stenosis that required endoscopic dilatation occurred in 2 % of patients.
Conclusions
LMAH is feasible, safe and provides an anti-reflux effect, even without fundoplication. As operation-related side effects seem to be rare, LMAH is a potential treatment option for large hiatal hernias with paraesophageal involvement.
Cu is the only monometallic electrocatalyst to produce highly reduced products from CO2 selectively because of its intermediate binding of CO. We investigate the performance of polycrystalline Cu for ...the electroreduction of CO in alkaline media (0.1 M KOH) at low overpotentials (−0.4 to −0.6 V vs RHE). We find that polycrystalline Cu is highly active at these potentials. The overall CO reduction rates are comparable to those of the nanostructured forms of the material, albeit with a distinct product distribution. While nanostructured forms of Cu favor alcohols, polycrystalline Cu produces greater amounts of C2 and C3 aldehydes, as well as ethylene.
One of the most devastating armed conflicts in history, World War I completely transformed the social and political landscape of the world in four short years. It also marked the appearance of the ...new modern lifestyle, one that always contained the grim prospect of the possible recurrence of war. Ian V. Hogg's The A to Z of World War I provides a dual approach to the study of this historically significant event.
A detailed protocol for PEG-mediated plastid transformation of Lactuca sativa cv. Flora, using leaf protoplasts, is described. Successful plastid transformation using protoplasts requires a large ...number of viable cells, high plating densities, and an efficient regeneration system. Transformation was achieved using a vector that targets genes to the trnI/trnA intergenic region of the lettuce plastid genome. The aadA gene, encoding an adenylyltransferase enzyme that confers spectinomycin resistance, was used as a selectable marker. With the current method, the expected transformation frequency is 1-2 spectinomycin-resistant cell lines per 10(6) viable protoplasts. Fertile, diploid, homoplasmic, plastid-transformed lines were obtained. Transmission of the plastid-encoded transgene to the T1 generation was demonstrated.
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