In this work, we have examined an electrochemical behavior of the ephedrine at the polarized liquid-liquid interface (water/1,2-dichloroethane). In this respect, we first designed and then 3D printed polyamide-based electrochemical cell that was used as the liquid-liquid interface support during electroanalytical measurements. The protonated ephedrine undergoes a reversible ion transfer reaction with the standard Galvani potential difference equal to +0.269 V. This value was used to calculate the water - 1,2-dichloroethane logP equal to -4.6. Ion transfer voltammetry was used to build the calibration curve and allowed for the ephedrine detection from concentration equal to 20 μM. By varying the pH of the aqueous phase from 2 up to 12 we were able to plot the ion partition diagram that was further analyzed and provided several pharmacochemical information. To further push this work towards practical utility, we have formulated the artificial urine and studied the interfacial behavior of all its components at the polarized liquid-liquid interface. Ephedrine detection from real spiked urine samples was also performed.
Rational enzyme design presents a major challenge that has not been overcome by computational approaches. One of the key challenges is the difficulty in assessing the magnitude of the maximum possible catalytic activity. In an attempt to overcome this challenge, we introduce a strategy that takes an active enzyme (assuming that its activity is close to the maximum possible activity), design mutations that reduce the catalytic activity, and then try to restore that catalysis by mutating other residues. Here we take as a test case the enzyme haloalkane dehalogenase (DhlA), with a 1,2-dichloroethane substrate. We start by demonstrating our ability to reproduce the results of single mutations. Next, we design mutations that reduce the enzyme activity and finally design double mutations that are aimed at restoring the activity. Using the computational predictions as a guide, we conduct an experimental study that confirms our prediction in one case and leads to inconclusive results in another case with 1,2-dichloroethane as substrate. Interestingly, one of our predicted double mutants catalyzes dehalogenation of 1,2-dibromoethane more efficiently than the wild-type enzyme.
- MeSH
- Models, Chemical * MeSH
- Ethylene Dichlorides chemistry MeSH
- Hydrolases chemistry MeSH
- Catalytic Domain MeSH
- Models, Molecular * MeSH
- Computer Simulation * MeSH
- Substrate Specificity MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Research Support, N.I.H., Extramural MeSH
Haloalkane dehalogenases catalyze the hydrolysis of halogen-carbon bonds in organic halogenated compounds and as such are of great utility as biocatalysts. The crystal structures of the haloalkane dehalogenase DhlA from the bacterium from Xanthobacter autotrophicus GJ10, specifically adapted for the conversion of the small 1,2-dichloroethane (DCE) molecule, display the smallest catalytic site (110 Å3) within this enzyme family. However, during a substrate-specificity screening, we noted that DhlA can catalyze the conversion of far bulkier substrates, such as the 4-(bromomethyl)-6,7-dimethoxy-coumarin (220 Å3). This large substrate cannot bind to DhlA without conformational alterations. These conformational changes have been previously inferred from kinetic analysis, but their structural basis has not been understood. Using molecular dynamic simulations, we demonstrate here the intrinsic flexibility of part of the cap domain that allows DhlA to accommodate bulky substrates. The simulations displayed two routes for transport of substrates to the active site, one of which requires the conformational change and is likely the route for bulky substrates. These results provide insights into the structure-dynamics function relationships in enzymes with deeply buried active sites. Moreover, understanding the structural basis for the molecular adaptation of DhlA to 1,2-dichloroethane introduced into the biosphere during the industrial revolution provides a valuable lesson in enzyme design by nature.
- MeSH
- Ethylene Dichlorides metabolism MeSH
- Halogenation MeSH
- Hydrolases chemistry metabolism MeSH
- Catalytic Domain MeSH
- Kinetics MeSH
- Protein Conformation MeSH
- Crystallography, X-Ray MeSH
- Coumarins chemistry metabolism MeSH
- Methylation MeSH
- Molecular Dynamics Simulation MeSH
- Molecular Docking Simulation MeSH
- Substrate Specificity MeSH
- Xanthobacter chemistry enzymology metabolism MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Recent advances in polarizable force fields have revealed that major reparameterization is necessary when the polarization energy is treated explicitly. This study is focused on the torsional parameters, which are crucial for the accurate description of conformational equilibria in biomolecules. In particular, attention is paid to the influence of polarization on the (i) transferability of dihedral terms between molecules, (ii) transferability between different environments, and (iii) additivity of dihedral energies. To this end, three polarizable force fields based on the induced point dipole model designed for use in AMBER are tested, including two recent ff02 reparameterizations. Attention is paid to the contributions due to short range interactions (1-2, 1-3, and 1-4) within the four atoms defining the dihedral angle. The results show that when short range 1-2 and 1-3 polarization interactions are omitted, as for instance in ff02, the 1-4 polarization contribution is rather small and unlikely to improve the description of the torsional energy. Conversely, when screened 1-2 and 1-3 interactions are included, the polarization contribution is sizeable and shows potential to improve the transferability of parameters between different molecules and environments as well as the additivity of dihedral terms. However, to reproduce intramolecular polarization effects accurately, further fine-tuning of the short range damping of polarization is necessary.
Chlorinated hydrocarbons are very often used and are relatively dangerous substances from healthy risk point of view. While manipulating with them, mainly in large volumes, individual protective equipment (IPE) must be used in a protection position. Users are supposed to know the construction material breakthrough time especially in case of long-term usage of personal IPE and in the situation when contamination of them is real. Studying connections between a chemical compound structure and the structure of IPE characterised by barrier materials enables us to understand present body protective devices protection quality and gives us an option to choose barrier materials with targeted properties. In this article there are results of breakthrough time of isolating protection folio with a butyl rubber barrier layer in relation to chlorinated ethanes. This material is used for protection of specialists of both Fire Rescue Brigades and the Czech Armed Forces Chemical Corps. The PIEZOTEST device has been used for detection of permeated chemicals. The Quartz Crystal Microbalance (QCM) sensor is a part of PIEZOTEST device.
- Keywords
- lag-time, butyl rubber, steady state permeation rate, breakthrough time,
- MeSH
- Time Factors MeSH
- Hydrocarbons, Chlorinated * chemistry MeSH
- Elastomers chemistry MeSH
- Ethane analogs & derivatives chemistry MeSH
- Ethylene Dichlorides chemistry MeSH
- Quartz Crystal Microbalance Techniques statistics & numerical data MeSH
- Hazardous Substances chemistry MeSH
- Protective Clothing * MeSH
- Permeability * MeSH
- Solubility MeSH
- Materials Testing methods statistics & numerical data MeSH
- Trichloroethanes chemistry MeSH
- Publication type
- Research Support, Non-U.S. Gov't MeSH
Environmental health criteria ; No. 176
2nd ed. 148 s. : tab. ; 23 cm
- Conspectus
- Veřejné zdraví a hygiena
- NML Fields
- environmentální vědy
- environmentální vědy
- NML Publication type
- publikace WHO
Health and Safety Guide, ISSN 0259-7268 No. 55
32 s. : tab., lit.
- Conspectus
- Chemie. Mineralogické vědy
- NML Fields
- chemie, klinická chemie
- toxikologie
- NML Publication type
- publikace WHO
- MeSH
- Chromatography utilization MeSH
- Adult MeSH
- Ethylene Dichlorides poisoning MeSH
- Humans MeSH
- Adolescent MeSH
- Autopsy MeSH
- Aged MeSH
- Forensic Medicine methods MeSH
- Check Tag
- Adult MeSH
- Humans MeSH
- Adolescent MeSH
- Male MeSH
- Aged MeSH
- Female MeSH
- Publication type
- Case Reports MeSH
