Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P50583 (asymmetrical)
 12,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Highly accurate rate parameters for H-abstraction reactions by HO2 radicals are needed for development of predictive chemical kinetic models for ignition. In this article, we report the rate coefficients for reaction of hydroperoxyl radical (HO2) with 2-methyltetrahydrofuran (MTHF) and 2,5-dimethyltetrahydrofuran (DMTHF) computed employing CBS-QB3 and CCSD(T)/cc-pVTZ//B3LYP/cc-pVTZ level of theory in the temperature range of 500-2000 K. Conventional transition state theory (CTST) with hindered rotor approximation for low frequency torsional modes and RRHO (rigid-rotor harmonic oscillator) approximation for all other vibrational modes is employed to evaluate the high pressure rate constants as a function of temperature. Rate constant of each individual hydrogen abstraction channel is taken into account to calculate the overall rate constant. Three-parameter Arrhenius expressions have been obtained by fitting to the computed rate constants of all abstraction channels between 500 and 2000 K. Eight transition states have been identified for MTHF and four for slightly more stable trans-DMTHF. Intrinsic reaction coordinates (IRC) calculations were performed to verify the connectivity of all the transition states (TSs) with reactants and products. One dimensional Eckart's asymmetrical method has been used to calculate quantum mechanical tunneling effect. Results of the theoretically calculated rate coefficients indicate that the hydrogen abstraction by HO2 from the C2 carbon of both MTHF and DMTHF is the most dominant path among all reaction pathways attributed to its lowest barrier height. The total rate coefficients of the MTHF and DMTHF with HO2 at CCSD(T)/cc-pVTZ//B3LYP/cc-pVTZ level of theory are k(T) = 8.60T(3.54) exp(-8.92/RT) and k(T)= 3.17T(3.63) exp(-6.59/RT) cm(3) mol(-1) s(-1), respectively. At both the level of theories, the predicted total abstraction rate constant for DMTHF is found to be higher as compared to that of MTHF over an entire temperature range of investigation. The overall rate constant calculated at CCSD(T)/cc-pVTZ//B3LYP/cc-pVTZ level of theory is lower by 1.43 and 3.44 times at 2000 K than the CBS-QB3 level for MTHF and DMTHF, respectively.
...
PMID:Reaction kinetics of hydrogen abstraction reactions by hydroperoxyl radical from 2-methyltetrahydrofuran and 2,5-dimethyltetrahydrofuran. 2371 83

Roots normally grow in darkness, but they may be exposed to light. After perceiving light, roots bend to escape from light (root light avoidance) and reduce their growth. How root light avoidance responses are regulated is not well understood. Here, we show that illumination induces the accumulation of flavonols in Arabidopsis thaliana roots. During root illumination, flavonols rapidly accumulate at the side closer to light in the transition zone. This accumulation promotes asymmetrical cell elongation and causes differential growth between the two sides, leading to root bending. Furthermore, roots illuminated for a long period of time accumulate high levels of flavonols. This high flavonol content decreases both auxin signaling and PLETHORA gradient as well as superoxide radical content, resulting in reduction of cell proliferation. In addition, cytokinin and hydrogen peroxide, which promote root differentiation, induce flavonol accumulation in the root transition zone. As an outcome of prolonged light exposure and flavonol accumulation, root growth is reduced and a different root developmental zonation is established. Finally, we observed that these differentiation-related pathways are required for root light avoidance. We propose that flavonols function as positional signals, integrating hormonal and reactive oxygen species pathways to regulate root growth direction and rate in response to light.
 ...
PMID:Flavonols Mediate Root Phototropism and Growth through Regulation of Proliferation-to-Differentiation Transition. 2662 43