Theoretical Studies on the Unimolecular Decomposition of Ethylene Glycol

The unimolecular decomposition processes of ethylene glycol have been investigated with the QCISD(T) method with geometries optimized at the B3LYP/6-311++G(d,p) level. Among the decomposition channels identified, the H₂O-elimination channels have the lowest barriers, and the C–C bond dissociation is the lowest-energy dissociation channel among the barrierless reactions (the direct bond cleavage reactions). The temperature and pressure dependent rate constant calculations show that the H₂O-elimination reactions are predominant at low temperature, whereas at high temperature, the direct C–C bond dissociation reaction is dominant. At 1 atm, in the temperature range 500–2000 K, the calculated rate constant is expressed to be 7.63 × 10⁴⁷<i>T</i>^–10.38 exp(−42262/<i>T</i>) for the channel CH₂OHCH₂OH → CH₂CHOH + H₂O, and 2.48 × 10⁵¹<i>T</i>^–11.58 exp(−43593/<i>T</i>) for the channel CH₂OHCH₂OH → CH₃CHO + H₂O, whereas for the direct bond dissociation reaction CH₂OHCH₂OH → CH₂OH + CH₂OH the rate constant expression is 1.04 × 10⁷¹<i>T</i>^–16.16 exp(−52414/<i>T</i>)

Thermal Decomposition of 1‑Pentanol and Its Isomers: A Theoretical Study

Pentanol is one of the promising “next generation” alcohol fuels with high energy density and low hygroscopicity. In the present work, dominant reaction channels of thermal decomposition of three isomers of pentanol: 1-pentanol, 2-methyl-1-butanol, and 3-methyl-1-butanol were investigated by CBS-QB3 calculations. Subsequently, the temperature- and pressure-dependent rate constants for these channels were computed by RRKM/master equation simulations. The difference between the thermal decomposition behavior of pentanol and butanol were discussed, while butanol as another potential alternative alcohol fuel has been extensively studied both experimentally and theoretically. Rate constants of barrierless bond dissociation reactions of pentanol isomers were treated by the variational transition state theory. The comparison between various channels revealed that the entropies of variational transition states significantly impact the rate constants of pentanol decomposition reactions. This work provides sound quality kinetic data for major decomposition channels of three pentanol isomers in the temperature range of 800–2000 K with pressure varying from 7.6 to 7.6 × 10⁴ Torr, which might be valuable for developing detailed kinetic models for pentanol combustion

Theoretical Studies on the Unimolecular Decomposition of Propanediols and Glycerol

Polyols, a typical type of alcohol containing multiple hydroxyl groups, are being regarded as a new generation of a green energy platform. In this paper, the decomposition mechanisms for three polyol molecules, i.e., 1,2-propanediol, 1,3-propanediol, and glycerol, have been investigated by quantum chemistry calculations. The potential energy surfaces of propanediols and glycerol have been built by the QCISD­(T) and CBS-QB3 methods, respectively. For the three molecules studied, the H₂O-elimination and C–C bond dissociation reactions show great importance among all of the unimolecular decomposition channels. Rate constant calculations further demonstrate that the H₂O-elimination reactions are predominant at low temperature and pressure, whereas the direct C–C bond dissociation reactions prevail at high temperature and pressure. The temperature and pressure dependence of calculated rate constants was demonstrated by the fitted Arrhenius equations. This work aims to better understand the thermal decomposition process of polyols and provide useful thermochemical and kinetic data for kinetic modeling of polyols-derived fuel combustion

Online Characterization of Isomeric/Isobaric Components in the Gas Phase of Mainstream Cigarette Smoke by Tunable Synchrotron Radiation Vacuum Ultraviolet Photoionization Time-of-Flight Mass Spectrometry and Photoionization Efficiency Curve Simulation

A newly developed, qualitative and quantitative method based on tunable synchrotron radiation vacuum ultraviolet photoionization time-of-flight mass spectrometry (SR-VUV-PI-TOFMS) and photoionization efficiency (PIE) curve simulation was applied for the online analysis of isomers and isobaric compounds in the gas phase of mainstream cigarette smoke. After blocking the particulate phase components by the Cambridge filter pad, a puff of fresh gas-phase cigarette smoke was immediately introduced into a vacuum ionization chamber through a heated capillary, then was photoionized, and analyzed by a TOF mass spectrometer. The PIE curves for the mass peaks up to <i>m</i>/<i>z</i> = 106 were measured between 8.0 and 10.7 eV. Some components could be directly identified by their discriminated ionization energies (IEs) on the PIE curve. By simulating the PIE curve with the sum of scaled absolute photoionization cross sections (PICSs), complex isomeric/isobaric compounds along with their mole fractions could be obtained when the best-fitting was realized between experimental and simulated PIE curves. A series of reported toxic compounds for quantification, such as 1,3-butadiene (<i>m</i>/<i>z</i> = 54), 1,3-cyclopentadiene (<i>m</i>/<i>z</i> = 66), benzene (<i>m</i>/<i>z</i> = 78), xylene (<i>m</i>/<i>z</i> = 106), 2-propenal (<i>m</i>/<i>z</i> = 56), acetone and propanal (<i>m</i>/<i>z</i> = 58), crotonaldehyde (<i>m</i>/<i>z</i> = 70), furan and isoprene (<i>m</i>/<i>z</i> = 68), were all found to have other isomers and/or isobaric compounds with considerable abundances. Some isomers have never been reported previously in cigarette smoke, like C₅H₆ isomers 1-penten-3-yne, 3-penten-1-yne, and 1-penten-4-yne at <i>m</i>/<i>z</i> = 66. Isomeric/isobaric compounds characterization for the mass peaks and mole fraction calculations were discussed in detail below 10.7 eV, an energy value covering several conventional used VUV light sources

Major clinical manifestations of the affected individuals.

<p>Major clinical manifestations of the affected individuals.</p

Compound heterozygous mutations and genomics structure of the exons of <i>ERCC6</i>.

<p>A) Pedigree of this family. Black symbols denote affected individuals, and open symbols denote unaffected individuals. B) The region of UTR (green) and coding (red) are listed in the <i>ERCC6</i> gene (upper panel). Sanger sequencing analysis of c.1607T->G (p.Leu536Trp) and c.1595A->G (p.Asp532Gly) mutations in five family members. The heterozygous missense mutation c.1607T->G was identified in proband’s father (Parent I:1), another heterozygous missense mutation c.1595A->G in proband’s mother (Parent I:2) and three affected sisters carried (Affected II:1, II:2, II:3) the compound heterozygous mutations.</p

The conservation and domain structure of excision repair protein ERCC-6.

<p>A) Multiple sequence alignment of ERCC6 ATP-binding domain amino acids among homologous genes in mammals, reptile, nematode, oyster and insects both 532D and 536L heterozygous missense mutations are at a highly conserved position in <i>ERCC6</i>. B) The structure of CSB protein indicated that the two mutations D532G and L536W are located in motif I of the helicase domain. A, acidic amino acid stretch; G, glycine rich region; S, serine phosphorylation site preceded by a nuclear location signal; N, nucleotide binding fold; NTB, nucleotide binding fold; I, IA, and II-VI refer to the corresponding helicase motifs.</p

Autophagy and Apoptosis in Hepatocellular Carcinoma Induced by EF25-(GSH)₂: A Novel Curcumin Analog

<div><p>Curcumin, a spice component as well as a traditional Asian medicine, has been reported to inhibit proliferation of a variety of cancer cells but is limited in application due to its low potency and bioavailability. Here, we have assessed the therapeutic effects of a novel and water soluble curcumin analog, 3,5-bis(2-hydroxybenzylidene)tetrahydro-4<i>H</i>-pyran-4-one glutathione conjugate [EF25-(GSH)₂], on hepatoma cells. Using the MTT and colony formation assays, we determined that EF25-(GSH)₂ drastically inhibits the proliferation of hepatoma cell line HepG2 with minimal cytotoxicity for the immortalized human hepatic cell line HL-7702. Significantly, EF25-(GSH)₂ suppressed growth of HepG2 xenografts in mice with no observed toxicity to the animals. Mechanistic investigation revealed that EF25-(GSH)₂ induces autophagy by means of a biphasic mechanism. Low concentrations (<5 µmol/L) induced autophagy with reversible and moderate cytoplasmic vacuolization, while high concentrations (>10 µmol/L) triggered an arrested autophagy process with irreversible and extensive cytoplasmic vacuolization. Prolonged treatment with EF25-(GSH)₂ induced cell death through both an apoptosis-dependent and a non-apoptotic mechanism. Chloroquine, a late stage inhibitor of autophagy which promoted cytoplasmic vacuolization, led to significantly enhanced apoptosis and cytotoxicity when combined with EF25-(GSH)₂. Taken together, these data imply a fail-safe mechanism regulated by autophagy in the action of EF25-(GSH)₂, suggesting the therapeutic potential of the novel curcumin analog against hepatocellular carcinoma (HCC), while offering a novel and effective combination strategy with chloroquine for the treatment of patients with HCC.</p></div

Morphology of autophagosomes in EF25-(GSH)₂-treated HepG2 cells.

<p>HepG2 cells were treated with 20 µmol/L EF25-(GSH)₂ for 16 h and observed under transmission electron microscopy. (A) and (B), multimembranous autophagic vacuoles engulfing cytoplasmic components are indicated with black arrowheads. (C) and (D), autophagic vacuoles containing a mitochondrion are indicated with black asterisk.</p

The morphological appearance of EF25-(GSH)₂-treated HepG2 cells.

<p>(A) HepG2 cells treated with increasing concentrations of EF25-(GSH)₂ for 16 h were observed under a light microscope and representative images were visualized. EF25-(GSH)₂-treated cells underwent vacuolization, the extent of which varied when treated with different concentrations of EF25-(GSH)₂. At 20 µmol/L, apoptotic-like cell membrane blebbing was observed (arrowheads). (B) A representative transmission electron microscopy (TEM) image of untreated HepG2 cells. (C) In 5 µmol/L EF25-(GSH)₂-treated cells, most vacuolated cells regained normal morphology at 32 h post-treatment (arrows, 1-4) while some did not (arrow heads, 5 and 6). (D) Representative TEM images of cells treated with 10 µmol/L EF25-(GSH)₂ for 16 h. *, large empty vacuoles with varying size. (E) Representative TEM images of cells treated with 20 µmol/L EF25-(GSH)₂ for 16 h. *, large empty vacuoles; arrows, autophagic vacuoles.</p