1.
A computational chemistry investigation of the mechanism of the water-assisted decomposition of trichloroethylene oxide.
Huang, J, Yeung, CS, Ma, J, Gayner, ER, Phillips, DL
The journal of physical chemistry. A. 2014;(9):1557-67
Abstract
Trichloroethylene oxide is a downstream product in the oxidative metabolism of trichloroethylene (TCE) and it may be involved in cytochrome P450 inactivation, protein function destruction, and nucleic acid base alkalization. To explore the hydrolysis mechanism of the decomposition of TCE oxide, an investigation using Second-order Møller-Plesset perturbation theory in conjunction with density functional theory has been conducted to analyze the effect of the water solvation shell on probable reaction steps. The decomposition of TCE oxide is accelerated by coordinated water molecules (up to seven), which reveals that water molecules can help to solvate the TCE oxide molecule and activate the release of the Cl(-) leaving group. After the opening of the epoxide ring, several pathways are proposed to account for the dehalogenation step along with the formation of CO as well as three carboxylic acids (formic acid, glyoxylic acid, and dichloroacetic acid). The predominant pathways were examined by comparing the computed activation energies for the formation of the products to each other for the possible reaction steps examined in this work. After rationally analyzing the computational results, the ring-opening reaction has been identified as the rate-determining step. The rate constant estimated for the TCE oxide decomposition from the calculations performed here was found to be reasonably consistent with previous experimental observations reported in the literature.
2.
Hydraulic signals in long-distance signaling.
Christmann, A, Grill, E, Huang, J
Current opinion in plant biology. 2013;(3):293-300
Abstract
Higher plants are sessile organisms that continuously adapt their metabolism and development in response to a changing environment. Control of water uptake and the maintenance of water status are key for the survival and optimal growth of plants. Environmental factors such as radiation, air temperature, rainfall, and humidity have a high impact on plant water relations. Hence, plants require a coordinated and timely response in above-ground and below-ground organs to cope with the changing need to take up and preserve water. In this review we will focus on changes in plant water availability and on how information on the water status is communicated to remote plant organs. We will summarize the current knowledge of long-distance signaling by hydraulic cues and of potential sensors required to convert a physical signal into a chemical messenger, namely the plant hormone abscisic acid (ABA).