Chemical binding

About: Chemical binding is a research topic. Over the lifetime, 1822 publications have been published within this topic receiving 52516 citations.

Cell and molecular biology of chemical allergy

Abstract: Objective The objective of this review is to provide current approaches to gain increased understanding of the molecular basis of chemical allergenicity. Chemical allergy refers to an allergic reaction to a low molecular weight agent (ie, Data Sources Data were obtained from published clinical reports and from the Documentation of Threshold Limit Values (1998) published by the American Congress of Governmental Industrial Hygienists. Results In vitro studies indicate the stoichiometric reaction of some chemical allergens with glutathione and the subsequent transfer of the allergen from glutathione to other nucleophiles. Computer-generated structure-activity relationship models have been developed for chemicals that induce respiratory allergy. The models, based on physicochemical properties of the agents, have high sensitivity and specificity. Conclusions The structure-activity relationship model suggests that chemical binding is the essential feature of chemical allergens. Their in vivo reactions with thiols may result in glutathione deficiency with consequent alteration in cellular reduction-oxidation (redox) status, release of cytokines, and promotion of the T helper cell 2 phenotype. Prevention of permanent disease is dependent on periodic medical surveillance of affected workers. When detected early, the disease can frequently be reversed.

Effect of additives on particulate matter formation of solid biofuel blends from wood and straw

Abstract: The combustion of solid biofuels is characterized by the formation of particulate matter emissions harmful to humans and the environment. Inorganic elements which are volatile under high temperatures (∼600–1200 °C) are emitted as vapor, then cooling down in the flue gas, and are re-sublimated and emitted as solid particulate matter emissions (fly ash). Thus, the objective of this paper is it to summarize the current knowledge of the forming mechanism of these particulate matter emissions taking place during the combustion of wood and straw, and bring the elements in particulate matter with the help of additive in a stable solid phase, so they stay in the bottom ash and are not emitted. Here, two different additives are tested, based on Al, Mg and Ca. Important in this respect is the knowledge of the chemical formations during the combustion process of the different ash-forming elements contained within solid biofuels. Therefore, the chemical binding forms of the ash-forming elements (Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S, and Cl) within the solid biofuel are presented. Based on this, possible conversion products are discussed including theoretical calculated intermediates; this includes the chemical conversion pathway. On this basis, additives are identified based on the difference of the elemental composition of wood/straw blends to wood and the results of the formation of particulate matter during combustion are assessed in lab scale. The additives are composed of Al2O3, CaHPO4, and CaCO3 or Al2O3, MgHPO4, and MgCO3. The results from the characterization techniques TGA, AAS, IC, and XRD show that the formation of particulate matter during a complete thermo-chemical conversion can be suppressed to certain extend.

Metal Ion Reactivity with 1,4-Benzenedimethanethiol Monolayers on Gold

Abstract: Exposure of Cu2+ ions to 1,4-benzenedimethanethiol (BDMT) monolayers on Au in solution results in the formation of copper functionalized monolayers which have been investigated in detail by surface-enhanced Raman spectroscopy (SERS), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV). Upon exposure to copper ions, the free thiol groups at the surface of the monolayer disappear indicating the replacement of protons with copper ions. The reaction leads to a red shift in the C−S stretching frequency, but most of the other features are unaffected. Relative intensities of the peaks are largely the same; however, some new features are observed suggesting minor changes in the adsorbate structure that makes additional modes observable. Thermal stability of the monolayers has been reduced substantially as a result of reaction with metal ions, indicating that the chemical binding at the Au−monolayer interface is affected. XPS shows that copper is present at the surface. Electrochemical behavior bef...

Binding, tuning and mechanical function of the 4-hydroxy-cinnamic acid chromophore in photoactive yellow protein.

Abstract: The bacterial photoreceptor protein photoactive yellow protein (PYP) covalently binds the chromophore 4-hydroxy coumaric acid, tuning (spectral) characteristics of this cofactor. Here, we study this binding and tuning using a combination of pointmutations and chromophore analogs. In all photosensor proteins studied to date the covalent linkage of the chromophore to the apoprotein is dispensable for light-induced catalytic activation. We analyzed the functional importance of the covalent linkage using an isosteric chromophore-protein variant in which the cysteine is replaced by a glycine residue and the chromophore by thiomethyl-p-coumaric acid (TMpCA). The model compound TMpCA is shown to weakly complex with the C69G protein. This non-covalent binding results in considerable tuning of both the pKa and the color of the chromophore. The photoactivity of this system, however, was strongly impaired, making PYP the first known photosensor protein in which the covalent linkage of the chromophore is of paramount importance for the functional activity of the protein in vitro. We also studied the influence of chromophore analogs on the color and photocycle of PYP, not only in WT, but especially in the E46Q mutant, to test if effects from both chromophore and protein modifications are additive. When the E46Q protein binds the sinapinic acid chromophore, the color of the protein is effectively changed from yellow to orange. The altered charge distribution in this protein also results in a changed pKa value for chromophore protonation, and a strongly impaired photocycle. Both findings extend our knowledge of the photochemistry of PYP for signal generation.