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Chemical binding
About: Chemical binding is a research topic. Over the lifetime, 1822 publications have been published within this topic receiving 52516 citations.
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19 May 2020
TL;DR: In this paper, the authors used intact soil cores (0.2m depth) from beech (Fagus sylvatica) forests to trace the fate of 33P in soil, plant and microbial fractions.
Abstract: Phosphorus (P) availability shows large differences among different soil types, affecting P nutrition of forest trees. Chemical binding of P to soil moieties affects partitioning of P between soil particles and solution, influencing soluble P concentrations upon which plants, their associated mycorrhizal symbionts, and microbes feed. The goal of this study was to characterize root P uptake by mycorrhizal and non-mycorrhizal root tips in competition with microbes in situ in the organic and mineral layer of a P-rich and a P-poor forest. We used intact soil cores (0.2m depth) from beech (Fagus sylvatica) forests to tracing the fate of 33P in soil, plant and microbial fractions. We used the dilution of 33P in the rhizosphere of each soil layer to estimate the enrichment with new P in mycorrhizal and non-mycorrhizal root tips and root P uptake. In soil cores from P-rich conditions, 25% and 75% of root P uptake occurred in the organic and mineral layer, respectively, whereas in the P-poor forest, 60% occurred in the organic and 40% in the mineral layer. Mycorrhizal P efficiency, determined as enrichment of new P in mycorrhizal root tips, differed between soil layers. Root P uptake was correlated with mycorrhizal P efficiency and root tip abundance but not with root tip abundance as a single factor. This finding underpins the importance of the regulation of mycorrhizal P acquisition for root P supply. The composition of mycorrhizal assemblages differed between forests but not between soil layers. Therefore, differences in P efficiencies resulted from physiological adjustments of the symbionts. Non-mycorrhizal root tips were rare and exhibited lower enrichment with new P than mycorrhizal root tips. Their contribution to root P supply was negligible. Microbes were strong competitors for P in P-poor but not in P-rich soil. Understory roots were present in the P-rich soil but did not compete for P. Our results uncover regulation of mycorrhizal P efficiencies and highlight the complexity of biotic and abiotic factors that govern P supply to trees in forest ecosystems.
23 citations
TL;DR: The hypothesis that four water molecules are present in the binding cavity of thapsigargin in sarco/endoplasmic reticulum calcium ATPase (SERCA) and mediate an extensive hydrogen-bonding network is verified by measuring the affinity of newly synthesized model compounds, which are prevented from participating in such water-mediated interactions as hydrogen- bond donors.
Abstract: A crystal structure suggests four water molecules are present in the binding cavity of thapsigargin in sarco/endoplasmic reticulum calcium ATPase (SERCA). Computational chemistry indicates that three of these water molecules mediate an extensive hydrogen-bonding network between thapsigargin and the backbone of SERCA. The orientation of the thapsigargin molecule in SERCA is crucially dependent on these interactions. The hypothesis has been verified by measuring the affinity of newly synthesized model compounds, which are prevented from participating in such water-mediated interactions as hydrogen-bond donors.
23 citations
TL;DR: The main assumption of this theory is the mutual saturation of a definite number of valences, that is, short range forces emerging from neutral atoms and acting between nearest neighbors only as discussed by the authors.
Abstract: AT THE Chicago meeting of the AMERICAN CHEMICAL SOCIETY in April 1948, several papers relating to the physical nature of chemical binding were presented by the author and his associates, Theodore Berlin, Beth Cook, and Peter A. S. Smith. The problem of chemical binding was approached from a point of view which differs considerably from the classical valence bond theory and its usual electronic interpretations ( 1 ). Although the current theories have been extremely useful for the representation of a great number of compounds, it is sufficient to mention carbon monoxide in order to demonstrate that the valence bond theory was not completely satisfactory from the very outset (ca. 1860). The main assumption of this theory is the mutual saturation of a definite number of valences, that is, short range forces emerging from neutral atoms and acting between nearest neighbors only. This idea appears to apply satisfactorily ...
23 citations
TL;DR: In this paper, the surface roughness of the Ni and Cu sputtered deposition layers and the crystal structure of the electrodeposited Cu layer changed according to the pre-treatment atmosphere and times of PI.
Abstract: In microelectronics packaging, the reliability of the metal/polymer interface is an important issue because the adhesion strength between dissimilar materials is often inherently poor. This paper reports the peel strength and surface morphology of a Cu/Ni/PI structure flexible copper clad laminate (FCCL) based on polyimide(PI) according to the pre-treatment atmosphere and times. Field emission scanning electron microscopy (FESEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS) were used to analyze the surface morphology, crystal structure and interface binding structure, respectively, of the sputtered Ni, Cu, and electrodeposited copper foil layers. The surface roughness of the Ni and Cu sputtered deposition layers and the crystal structure of the electrodeposited Cu layer changed according to the pre-treatment atmosphere and times of PI. The PI surface etching speeds and surface shapes differed according to the gas used in plasma preprocessing. The highest peel strength (mean 15.8 gf/mm) can be obtained in a preprocessing process for 400 seconds in an O2 atmosphere due to the increase in mechanical binding force and change in chemical binding structure caused by the increase in polyimide surface roughness.
23 citations
TL;DR: The cytotoxic effect of silver ions seems to be muted by silver ions by being: (1) taken up by undamaged cells, neutralised by glutathione (GSH) and accumulated in lysosomal vesicles, (2) bound extracellularly to SH-groups of the collagen fibres.
Abstract: Organotypic cultures of human breast skin incubated with silver bandage or treated with silver sulfadiazine accumulated silver in epithelial cells and in macrophages, fibroblasts and collagen fibrils and fibres of underlying connective tissue. Ultrastructurally, the accumulated silver was found in lysosome-like vesicles of the different cells and evenly spread along collagen structures. Apoptotic nuclei were present but few. Autometallographic amplification of 2D-PAGE gels revealed that glutathione S-transferase and glutathion detoxify silver ions in the epidermal cell by binding them in silver-sulphur nanocrystals. Thus, the cytotoxic effect of silver ions seems to be muted by silver ions by being: (1) taken up by undamaged cells, neutralised by glutathione (GSH) and accumulated in lysosomal vesicles, (2) bound extracellularly to SH-groups of the collagen fibres.
22 citations