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11.
In this paper, we propose a structure for organo-mineral associations in soils based on recent insights concerning the molecular
structure of soil organic matter (SOM), and on extensive published evidence from empirical studies of organo-mineral interfaces.
Our conceptual model assumes that SOM consists of a heterogeneous mixture of compounds that display a range of amphiphilic
or surfactant-like properties, and are capable of self-organization in aqueous solution. An extension of this self-organizational
behavior in solution, we suggest that SOM sorbs to mineral surfaces in a discrete zonal sequence. In the contact zone, the formation of particularly strong organo-mineral associations appears to be favored by situations where either (i) polar
organic functional groups of amphiphiles interact via ligand exchange with singly coordinated mineral hydroxyls, forming stable
inner-sphere complexes, or (ii) proteinaceous materials unfold upon adsorption, thus increasing adhesive strength by adding
hydrophobic interactions to electrostatic binding. Entropic considerations dictate that exposed hydrophobic portions of amphiphilic
molecules adsorbed directly to mineral surfaces be shielded from the polar aqueous phase through association with hydrophobic
moieties of other amphiphilic molecules. This process can create a membrane-like bilayer containing a hydrophobic zone, whose components may exchange more easily with the surrounding soil solution than those in the contact zone, but which are
still retained with considerable force. Sorbed to the hydrophilic exterior of hemimicellar coatings, or to adsorbed proteins,
are organic molecules forming an outer region, or kinetic zone, that is loosely retained by cation bridging, hydrogen bonding, and other interactions. Organic material in the kinetic zone
may experience high exchange rates with the surrounding soil solution, leading to short residence times for individual molecular
fragments. The thickness of this outer region would depend more on input than on the availability of binding sites, and would
largely be controlled by exchange kinetics. Movement of organics into and out of this outer region can thus be viewed as similar
to a phase-partitioning process. The zonal concept of organo-mineral interactions presented here offers a new basis for understanding
and predicting the retention of organic compounds, including contaminants, in soils and sediments. 相似文献
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Wagner S Kufleitner J Zensi A Dadparvar M Wien S Bungert J Vogel T Worek F Kreuter J von Briesen H 《PloS one》2010,5(12):e14213
Background
Due to the use of organophosphates (OP) as pesticides and the availability of OP-type nerve agents, an effective medical treatment for OP poisonings is still a challenging problem. The acute toxicity of an OP poisoning is mainly due to the inhibition of acetylcholinesterase (AChE) in the peripheral and central nervous systems (CNS). This results in an increase in the synaptic concentration of the neurotransmitter acetylcholine, overstimulation of cholinergic receptors and disorder of numerous body functions up to death. The standard treatment of OP poisoning includes a combination of a muscarinic antagonist and an AChE reactivator (oxime). However, these oximes can not cross the blood-brain barrier (BBB) sufficiently. Therefore, new strategies are needed to transport oximes over the BBB.Methodology/Principal Findings
In this study, we combined different oximes (obidoxime dichloride and two different HI 6 salts, HI 6 dichloride monohydrate and HI 6 dimethanesulfonate) with human serum albumin nanoparticles and could show an oxime transport over an in vitro BBB model. In general, the nanoparticulate transported oximes achieved a better reactivation of OP-inhibited AChE than free oximes.Conclusions/Significance
With these nanoparticles, for the first time, a tool exists that could enable a transport of oximes over the BBB. This is very important for survival after severe OP intoxication. Therefore, these nanoparticulate formulations are promising formulations for the treatment of the peripheral and the CNS after OP poisoning. 相似文献14.
Maurer C Panahandeh S Jungkamp AC Moser M Müller M 《Molecular biology of the cell》2010,21(23):4151-4161
Twin-arginine-containing signal sequences mediate the transmembrane transport of folded proteins. The cognate twin-arginine translocation (Tat) machinery of Escherichia coli consists of the membrane proteins TatA, TatB, and TatC. Whereas Tat signal peptides are recognized by TatB and TatC, little is known about molecular contacts of the mature, folded part of Tat precursor proteins. We have placed a photo-cross-linker into Tat substrates at sites predicted to be either surface-exposed or hidden in the core of the folded proteins. On targeting of these variants to the Tat machinery of membrane vesicles, all surface-exposed sites were found in close proximity to TatB. Correspondingly, incorporation of the cross-linker into TatB revealed multiple precursor-binding sites in the predicted transmembrane and amphipathic helices of TatB. Large adducts indicative of TatB oligomers contacting one precursor molecule were also obtained. Cross-linking of Tat substrates to TatB required an intact twin-arginine signal peptide and disappeared upon transmembrane translocation. Our collective data are consistent with TatB forming an oligomeric binding site that transiently accommodates folded Tat precursors. 相似文献
15.
One of the puzzling phenomena in philanthropy is that people can show strong compassion for identified individual victims but remain unmoved by catastrophes that affect large numbers of victims. Two prominent findings in research on charitable giving reflect this idiosyncrasy: The (1) identified victim and (2) victim number effects. The first of these suggests that identifying victims increases donations and the second refers to the finding that people’s willingness to donate often decreases as the number of victims increases. While these effects have been documented in the literature, their underlying psychological processes need further study. We propose a model in which identified victim and victim number effects operate through different cognitive and affective mechanisms. In two experiments we present empirical evidence for such a model and show that different affective motivations (donor-focused vs. victim-focused feelings) are related to the cognitive processes of impact judgments and mental imagery. Moreover, we argue that different mediation pathways exist for identifiability and victim number effects. 相似文献
16.
Matthias Weiling Christian Lechtenfeld Felix Pfeiffer Lars Frankenstein Diddo Diddens Jian-Fen Wang Sascha Nowak Masoud Baghernejad 《Liver Transplantation》2024,14(5):2303568
The implementation of silicon (Si)-containing negative electrodes is widely discussed as an approach to increase the specific capacity of lithium-ion batteries. However, challenges caused by severe volume changes and continuous (re-)formation of the solid-electrolyte interphase (SEI) on Si need to be overcome. The volume changes lead to electrolyte consumption and active lithium loss, decaying the cell performance and cycle life. Herein, the additive 2-sulfobenzoic acid anhydride (2-SBA) is utilized as an SEI-forming electrolyte additive for SiOx-containing anodes. The addition of 2-SBA to a state-of-the-art carbonate-based electrolyte in high-voltage LiNi0.8Mn0.1Co0.1O2, NMC811||artificial graphite +20% SiOx pouch cells leads to improved electrochemical performance, resulting in a doubled cell cycle life. The origin of the enhanced cell performance is mechanistically investigated by developing an advanced experimental technique based on operando attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy. The operando ATR-FTIR spectroscopy results elucidate the degradation mechanism via anhydride ring-opening reactions after electrochemical reduction on the anode surface. Additionally, ion chromatography conductivity detection mass spectrometry, scanning electron microscopy, energy dispersive X-ray analysis, and quantum chemistry calculations are employed to further elucidate the working mechanisms of the additive and its degradation products. 相似文献
17.
Several studies demonstrated that visual filtering mechanisms might underlie both conflict resolution of the Flanker conflict and the control of the Garner effect. However, it remains unclear whether the mechanisms involved in the processing of both effects depend on similar filter mechanisms, such that especially the Garner effect is able to modulate filtering needs in the Flanker conflict. In the present experiment twenty-four subjects participated in a combined Garner and Flanker task during two runs of functional magnetic resonance imaging (fMRI) recordings. Behavioral data showed a significant Flanker but no Garner effect. A run-wise analysis, however, revealed a Flanker effect in the Garner filtering condition in the first experimental run, while we found a Flanker effect in the Garner baseline condition in the second experimental run. The fMRI data revealed a fronto-parietal network involved in the processing of both types of effects. Flanker interference was associated with activity in the inferior frontal gyrus, the anterior cingulate cortex, the precuneus as well as the inferior (IPL) and superior parietal lobule (SPL). Garner interference was associated with activation in middle frontal and middle temporal gyrus, the lingual gyrus as well as the IPL and SPL. Interaction analyses between the Garner and the Flanker effect additionally revealed differences between the two experimental runs. In the first experimental run, activity specifically related to the interaction of effects was found in frontal and parietal regions, while in the second run we found activity in the hippocampus, the parahippocampal cortex and the basal ganglia. This shift in activity for the interaction effects might be associated with a task-related learning process to control filtering demands. Especially perceptual learning mechanisms might play a crucial role in the present Flanker and Garner task design and, therefore, increased performance in the second experimental run could be the reason for the lack of behavioral Garner interference on the level of the whole experiment. 相似文献
18.
Myxozoan parasitism in waterfowl 总被引:2,自引:0,他引:2
Bartholomew JL Atkinson SD Hallett SL Lowenstine LJ Garner MM Gardiner CH Rideout BA Keel MK Brown JD 《International journal for parasitology》2008,38(10):1199-1207
Myxozoans are spore-forming, metazoan parasites common in cold-blooded aquatic vertebrates, especially fishes, with alternate life cycle stages developing in invertebrates. We report nine cases of infection in free-flying native and captive exotic ducks (Anseriformes: Anatidae) from locations across the United States and describe the first myxozoan in birds, Myxidium anatidum n. sp. We found developmental stages and mature spores in the bile ducts of a Pekin duck (domesticated Anas platyrhynchos). Spores are lens-shaped in sutural view, slightly sigmoidal in valvular view, with two polar capsules, and each valve cell has 14-16 longitudinal surface ridges. Spore dimensions are 23.1 microm x 10.8 microm x 11.2 microm. Phylogenetic analysis of the ssrRNA gene revealed closest affinity with Myxidium species described from chelonids (tortoises). Our novel finding broadens the definition of the Myxozoa to include birds as hosts and has implications for understanding myxozoan evolution, and mechanisms of geographical and host range extension. The number of infection records indicates this is not an incidental occurrence, and the detection of such widely dispersed cases suggests more myxozoans in birds will be encountered with increased surveillance of these hosts for pathogens. 相似文献
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