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Guanine-quadruplexes (G4) are stable tetra-stranded DNA structures that may cause DNA replication stress and inhibit gene expression. Defects in unwinding these structures by DNA helicases may result in telomere shortening and DNA damage. Furthermore, due to mutations in WRN helicase genes in Werner syndrome, G4 motifs are likely to be key elements in the expression of premature aging phenotypes. The methylation of DNA plays a significant role in the stability and occurrence of G4. Thus, G4 frequency and DNA methylation mechanisms may be affected by excesses or deficiencies in methyl donors such as folate. B-Lymphocytes from Werner patients (n = 5) and healthy individuals (n = 5) were cultured in RPMI medium under condition of folate deficiency (20 nM) or sufficiency (200 nM) for 14 days. Cells were fixed on microscope slides for immunofluorescent staining to measure G4 frequency and γH2AX (a marker of DNA strand breaks) intensity, using automated quantitative imaging fluorescent microscopy. There was a significant increase (p < 0.05) in G4 levels in Werner syndrome patients compared to healthy controls. Werner and control cells grown in 20 nM folate media also showed significant increases in G4 (p < 0.001) and γH2AX (p < 0.01) signals compared with the same cells grown in 200 nM folate. Control cells grown in 20 nM folate also showed a significant reduction in DNA methylation levels (P < 0.05). The results of this study suggest that the occurrence of DNA G4 structures can be modulated in vitro via nutrients with important roles in methylation. [ABSTRACT FROM AUTHOR]

Guanine-quadruplexes (G4) are highly stable DNA secondary structures known to mediate gene regulation and to trigger genomic instability events during replication. G4 are known to be associated with DNA damage and we propose that G4 are involved in the ageing disorder mild cognitive impairment (MCI). Lymphocytes were obtained from healthy controls and individuals with MCI. The intensity and frequency of G4 foci as well as γH2AX (a marker of DNA damage) intensity were measured by quantitative immunofluorescence and were correlated with cognitive function and cytokinesis-block micronucleus cytome markers of DNA damage. γH2AX intensity as well as G4 frequency and intensity were significantly elevated in MCI lymphocytes compared to controls. The combined biomarker panel was tested in a predictive statistical model, which improved the demarcation of MCI from controls with 80.3% accuracy. The results obtained from this pilot study showed for the first time that G4 levels are increased with cognitive impairment and thus, may be involved in the early development of Alzheimer’s disease possibly via an association with chromosomal DNA damage and DNA double strand breaks. [ABSTRACT FROM AUTHOR]

G-quadruplexes (G4) are highly stable tetra-stranded DNA secondary structures known to mediate gene regulation and to trigger genomic instability events during replication. G4 structural stability can be affected by DNA methylation and oxidation modifications; thus nutrients such as folate that have the ability to alter these processes could potentially modify the genomic occurrence of G4 elements. Hela cells were cultured in a range of folate concentrations or in the presence or absence of 5-aza-2'-deoxycytidine, a DNA-methyltransferase inhibitor. G4 structures were then quantified by immunofluorescence using an automated quantitative imaging system. G4 frequency in Hela cells and nuclei area mean were increased in 20 nM folate medium compared with 2000 nM folate, as well as in the presence of 5-aza-2'-deoxycytidine when compared to cells non-exposed to 5-aza- 2'-deoxycytidine. These changes were exacerbated when pyridostatin, a G4 stabilising ligand, was added to the culture medium. G4 intensity in Hela cells cultured in deficient folate condition with pyridostatin was highly correlated with DNA damage as measured by γH2AX immunofluorescence (r = 0.71). This study showed for the first time that cellular G4 balance is modifiable by low folate concentrations and that these changes may occur as a consequence of DNA hypomethylation. Although the exact mechanism by which these changes occur is unclear, these findings establish the possibility that nutrients could be utilised as a tool for sustaining genome integrity by modifying G4 frequency at a cellular level. [ABSTRACT FROM AUTHOR]

Paul Crutzen received his doctorate in meteorology from the University of Stockholm in 1968 and was awarded the Nobel Prize in Chemistry in 1995. In addition to chemistry and atmospheric science, however, the breadth of his accomplishments has also been recognized by biologists, Earth system scientists, and geologists. This tribute provides some insight into Crutzen's career and how it contributed to so many scientific disciplines. In addition, we offer a road map showing how these diverse contributions were woven together over the course of more than five decades of research. The citation for the 1995 Nobel Prize reads that it was given for "work in atmospheric chemistry, particularly concerning the formation and decomposition of ozone." The inclusion of the wording "formation ... of ozone" applies only to him among the three laureates (Crutzen, Mario Molina, and F. Sherwood Rowland). His research on tropospheric chemistry led to seminal studies of tropical biomass burning, which eventually evolved into the concept later known as "nuclear winter," a topic in the forefront of far-ranging popular discussions in the 1980s. Last, Crutzen's proposal for the emergence of the "Anthropocene" as a new geological epoch that would terminate the 11,700-yr-old Holocene is considered by the Earth system science community to be the most pronounced trademark of his remarkable career. Crutzen also received American Meteorological Society's Battan Award for his coauthorship of Atmosphere, Climate, and Change, recognized by the organization as the best book for general audiences. In the later years of his career, as a member of the Pontifical Academy of Sciences, Crutzen was a key player in the formulation of Laudato Si', Pope Francis's encyclical on climate change, which was released in advance of the Conference of Parties (COP 21) meeting that announced the formulation of the Paris Climate Accords in 2015. [ABSTRACT FROM AUTHOR]

Experimental difficulties sometimes force modellers to use predicted rate coefficients for reactions of oxygenated volatile organic compounds (oVOCs). We examine here methods for making the predictions for reactions of atmospheric initiators of oxidation, NO3, OH, O3 and O(3P), with unsaturated alcohols and ethers. Logarithmic correlations are found between measured rate coefficients and calculated orbital energies, and these correlations may be used directly to estimate rate coefficients for compounds where measurements have not been performed. To provide a shortcut that obviates the need to calculate orbital energies, structure–activity relations (SARs) are developed. Our SARs are tested for predictive power against compounds for which experimental rate coefficients exist, and their accuracy is discussed. Estimated atmospheric lifetimes for oVOCs are presented. The SARs for alkenols successfully predict key rate coefficients, and thus can be used to enhance the scope of atmospheric models incorporating detailed chemistry. SARs for the ethers have more limited applicability, but can still be useful in improving tropospheric models. [Copyright &y& Elsevier]

Gas-phase rate coefficients for the atmospherically important reactions of NO3, OH and O3 are predicted for 55 α,β-unsaturated esters and ketones. The rate coefficients were calculated using a correlation described previously [Pfrang, C. , King, M. D. , C. E. Canosa-Mas, C. E. , Wayne, R. P. , 2006. Atmospheric Environment 40, 1170–1179]. These rate coefficients were used to extend structure–activity relations for predicting the rate coefficients for the reactions of NO3, OH or O3 with alkenes to include α,β-unsaturated esters and ketones. Conjugation of an alkene with an α,β-keto or α,β-ester group will reduce the value of a rate coefficient by a factor of ∼110, ∼2. 5 and ∼12 for reaction with NO3, OH or O3, respectively. The actual identity of the alkyl group, R, in −C(O)R or −C(O)OR has only a small influence. An assessment of the reliability of the SAR is given that demonstrates that it is useful for reactions involving NO3 and OH, but less valuable for those of O3 or peroxy nitrate esters. [Copyright &y& Elsevier]

The night-time tropospheric chemistry of two stress-induced volatile organic compounds (VOCs), (Z)-pent-2-en-1-ol and pent-1-en-3-ol, has been studied at room temperature. Rate coefficients for reactions of the nitrate radical (NO3) with these pentenols were measured using the discharge-flow technique. Because of the relatively low volatility of these compounds, we employed off-axis continuous-wave cavity-enhanced absorption spectroscopy for detection of NO3 in order to be able to work in pseudo first-order conditions with the pentenols in large excess over NO3. The rate coefficients were determined to be (1. 53±0. 23)×10−13 and (1. 39±0. 19)×10−14 cm3 molecule−1 s−1 for reactions of NO3 with (Z)-pent-2-en-1-ol and pent-1-en-3-ol. An attempt to study the kinetics of these reactions with a relative-rate technique, using N2O5 as source of NO3 resulted in significantly higher apparent rate coefficients. Performing relative-rate experiments in known excesses of NO2 allowed us to determine the rate coefficients for the N2O5 reactions to be (5. 0±2. 8)×10−19 cm3 molecule−1 s−1 for (Z)-pent-2-en-1-ol, and (9. 1±5. 8)×10−19 cm3 molecule−1 s−1 for pent-1-en-3-ol. We show that these relatively slow reactions can indeed interfere with rate determinations in conventional relative-rate experiments. [Copyright &y& Elsevier]

Abstract: The gas-phase rate coefficient for the reaction between OH radicals and CH3SCH2Cl (MCDMS) was determined to be (2.5±1.3)×10−12 cm3 molecule−1 s−1 using the discharge–flow kinetic technique. An estimate of ≈10−10 cm3 molecule−1 s−1 was obtained for the rate coefficient for reaction of Cl with MCDMS. It would appear that the reaction with OH is not the main loss process for CH3SCH2Cl in the marine boundary layer. The possible implications for the MBL of halogen-promoted oxidation of dimethylsulphide are considered. [Copyright &y& Elsevier]

The kinetics of the reactions of the atoms O(3P), S(3P), Se(3P), and Te(3P) with a series of alkenes are examined for correlations relating the logarithms of the rate coefficients to the energies of the highest occupied molecular orbitals (HOMOs) of the alkenes. These correlations may be employed to predict rate coefficients from the calculated HOMO energy of any other alkene of interest. The rate coefficients obtained from the correlations were used to © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 38: 351–356, 2006 [ABSTRACT FROM AUTHOR]

Abstract: We present updated structure–activity relations (SARs) for the prediction of rate coefficients for gas-phase reactions with alkenes of the major atmospheric oxidants NO3, OH and O3. Such SARs provide one way of incorporating essential information about reactivity into atmospheric models. Rate coefficients obtained from correlations relating the logarithms of the rate coefficients to the energies of the highest occupied molecular orbitals (HOMOs) of the alkenes were used to refine the SARs. SARs have an advantage for the user over the direct application of the correlations in that knowledge of the structure of the alkene of interest is sufficient to estimate rate coefficients, and no quantum-mechanical calculations need to be performed. A comparison of the values predicted by the SARs with experimental data where they exist allowed us to assess the reliability of our method. [Copyright &y& Elsevier]

Abstract: Methods are developed for predicting rate coefficients for reactions of initiators of tropospheric oxidation with unsaturated compounds that are abundant in the atmosphere; prognostic tools of this kind are essential for atmospheric chemists and modellers. To pursue the aim of exploring such tools, the kinetics of reactions of NO3, OH and O3 with a series of alkenes are examined for correlations relating the logarithms of the rate coefficients to the energies of the highest occupied molecular orbitals (HOMOs) of the alkenes. A comparison of the values predicted by the correlations with experimental data (where the latter exist) allowed us to assess the reliability of our method. We used a series of theoretical methods to calculate the HOMO energies, and found that higher computational effort improves the agreement of the predicted rate coefficients with experimental values, especially for reactions of NO3 with alkenes that possess vinyllic halogen substituents. As a consequence, it is expedient to suggest new correlations to replace those presented by us and others that were based on the lower level of theory. We propose the following correlations for the reactions of NO3, OH and O3 with alkenes: ln(/cm3 molecule−1 s−1)=6.40(E HOMO/eV)+31.69, ln(k OH/cm3 molecule−1 s−1)=1.21(E HOMO/eV)−12.34 and ln(/cm3 molecule−1 s−1)=3.28(E HOMO/eV)−6.78. These new correlations have been developed using the larger experimental data sets now available, and the impact of the extended data on the quality of the correlations is examined in the paper. Atmospheric lifetimes have been calculated from both experimental and estimated rate coefficients to provide an overview of removal efficiencies for different classes of alkenes with respect to oxidative processes initiated by NO3, OH and O3. A figure is presented to show the spatial scales over which alkenes may survive transport in competition with attack by NO3, OH and O3. Removal by NO3 or OH is always more important than removal by O3, and reactions with NO3 dominate for scales up to a few hundred metres. [Copyright &y& Elsevier]

Abstract: Rate coefficients for reactions of nitrate radicals (NO3) with the anthropogenic emissions 2-methylpent-2-ene, (Z)-3-methylpent-2-ene, ethyl vinyl ether, and the stress-induced plant emission ethyl vinyl ketone (pent-1-en-3-one) were determined to be (9.3±1.1)×10−12, (9.3±3.2)×10−12, (1.7±1.3)×10−12 and (9.4±2.7)×10−17 cm3 molecule−1 s−1. We performed kinetic experiments at room temperature and atmospheric pressure using a relative-rate technique with GC–FID analysis. Experiments with ethyl vinyl ether required a modification of our established procedure that might introduce additional uncertainties, and the errors suggested reflect these difficulties. Rate coefficients are discussed in terms of electronic and steric influences. Atmospheric lifetimes with respect to important oxidants in the troposphere were calculated. NO3-initiated oxidation is found to be the strongly dominating degradation route for 2-methylpent-2-ene, (Z)-3-methylpent-2-ene and ethyl vinyl ether. Atmospheric concentrations of the alkenes and their relative contribution to the total NMHC emissions from trucks can be expected to increase if plans for the introduction of particle filters for diesel engines are implemented on a global scale. Thus more kinetic data are required to better evaluate the impact of these emissions. [Copyright &y& Elsevier]

The evolution from print to electronic resources and services continues to pose significant challenges for academic libraries. This article presents a systematic, evidence-based approach to guide this transition, which resulted in an exhaustive reorganization of library staffing and services. The approach begins with the necessity of accumulating and then evaluating data on staff workloads and responsibilities. At the University of Texas Southwestern Medical Center at Dallas Library, this evaluation revealed that a preponderant amount of time was still spent on print-related activities that were no longer considered to be library priorities. The corrective actions taken to remedy this misalignment are then discussed. [ABSTRACT FROM AUTHOR]

The atmospheric fate of biogenic species such as the alkyl iodides is controlled mainly by photolysis, and by oxidation initiated by attack of Cl atoms and/or OH radicals. In order to assess the contribution made by OH attack on the simpler alkyl iodides, the absolute second-order rate coefficients for the reactions(1)OH+CH3I→ products,(2)OH+C2H5I→ products,(3)OH+1-C3H7I→products,(4)OH+2-C3H7I→products. were determined. These reactions were studied at P=1.5 and 5 Torr and at room temperature (298±2 K) using a fast-flow discharge system with resonance-fluorescence detection of OH radicals. The absolute second-order rate coefficients are k1=(0.99±0.20)×10−13 cm3 molecule−1 s−1, k2=(7.7±1.0)×10−13 cm3 molecule−1 s−1, k3=(25.0±3.0)×10−13 cm3 molecule−1 s−1and k4=(16.0±2.0)×10−13 cm3 molecule−1 s−1. The reactions were pressure independent over the range measured. The major atmospheric global degradation pathway is photolysis, with OH-initiated oxidation gaining importance for the propyl iodides. The effects of variable [Cl] on a local scale are discussed. [Copyright &y& Elsevier]

Methyl salicylate is one of a number of semiochemicals, signal molecules, emitted by herbivore-infested plants. These signal molecules attract predators of the herbivore, and the chemicals thus act indirectly as part of the defence mechanism of the plant. Previous studies have shown that ozone damage to plants can also elicit the emission of signal molecules. The fate of these signal molecules in the atmosphere is not known. Preliminary studies have been undertaken to examine the atmospheric chemistry of methyl salicylate for the first time. Rate coefficients for the reaction of methyl salicylate with atomic chlorine and with ozone have been determined; the values are (2.8±0.3) × 10[sup -12] and ∼4 × 10[sup -21]cm³ molecule[sup -1]s[sup -1]. These results suggest that neither reaction with atomic chlorine nor reaction with ozone will provide important loss routes for methyl salicylate in the atmosphere. The possible importance of photolysis of methyl salicylate in the atmosphere is considered. [ABSTRACT FROM AUTHOR]

A novel macroscale calorimeter has been designed and fabricated for the purpose of evaluating the thermodynamic and kinetic properties of chemical reactions, especially those associated with industrial manufacturing processes. This calorimeter includes provisions for isothermal and temperature-programmed operation over a wide range of temperatures, simultaneous or sequential addition of several reagents, and variable-rate agitation. The metal reaction vessel can be removed from the main housing of the calorimeter, permitting the use of vessels made from various materials for optimum corrosion resistance. Heat transfer takes place only through the base of the vessel, ensuring that the thermal efficiency remains independent of the sample volume. A novel computer control algorithm provides precise control of the reaction temperature, as well as low-noise measurement of heat flux. The observed detection threshold is 50 mW and a heat flux of several hundred watts can be dissipated. Provisions for simultaneous measurement of other properties, such as pH, make the calorimeter especially useful for small scale piloting of chemical processes. [ABSTRACT FROM AUTHOR]

• The "science-softCon UV/Vis+ photochemistry database" contains EUV-VUV-UV–Vis-NIR spectral data. • The database also contains quantum yields and photolysis related data. • The database provides valuable information for astrophysics, earth and planetary sciences, medical and pharmaceutical sciences. The "science-softCon UV/Vis+ Photochemistry Database" (www.photochemistry.org) is a large and comprehensive collection of EUV-VUV-UV–Vis-NIR spectral data and other photochemical information assembled from published peer-reviewed papers. The database contains photochemical data including absorption, fluorescence, photoelectron, and circular and linear dichroism spectra, as well as quantum yields and photolysis related data that are critically needed in many scientific disciplines. This manuscript gives an outline regarding the structure and content of the "science-softCon UV/Vis+ Photochemistry Database". The accurate and reliable molecular level information provided in this database is fundamental in nature and helps in proceeding further to understand photon, electron and ion induced chemistry of molecules of interest not only in spectroscopy, astrochemistry, astrophysics, Earth and planetary sciences, environmental chemistry, plasma physics, combustion chemistry but also in applied fields such as medical diagnostics, pharmaceutical sciences, biochemistry, agriculture, and catalysis. In order to illustrate this, we illustrate the use of the UV/Vis+ Photochemistry Database in four different fields of scientific endeavor. [ABSTRACT FROM AUTHOR]

Presents a chemistry classroom demonstration on the formation of aerosols from biogenic hydrocarbons. Identification of biogenic hydrocarbon content in volatile organic compounds; Reaction of ozone with terpenes found in oranges; Creation of ozone through the photolysis of molecular oxygen in air.

Objective To estimate the cumulative incidence of infertility for men and women in a population-based sample. Design Longitudinal study of a birth cohort. Setting Research unit. Patient(s) A population-based birth cohort of 1,037 men and women born in Dunedin, New Zealand, between 1972 and 1973. Intervention(s) None. Main Outcome Measure(s) Cumulative incidence of infertility by age 32 and 38, distribution of causes and service use for infertility, live birth subsequent to infertility, and live birth by age 38. Result(s) The cumulative incidence of infertility by age 38 ranged from 14.4% to 21.8% for men and from 15.2% to 26.0% for women depending on the infertility definition and data used. Infertility, defined as having tried to conceive for 12 months or more or having sought medical help to conceive, was experienced by 21.8% (95% confidence interval [CI], 17.7–26.2) of men and 26.0% (95% CI, 21.8–30.6) of women by age 38. For those who experienced infertility, 59.8% (95% CI, 48.3–70.4) of men and 71.8% (95% CI, 62.1–80.3) of women eventually had a live birth. Successful resolution of infertility and entry into parenthood by age 38 were much lower for those who first experienced infertility in their mid to late thirties compared with at a younger age. Conclusion(s) Comparison of reports from two assessments in this cohort study suggests infertility estimates from a single cross-sectional study may underestimate lifetime infertility. The lower rate of resolution and entry into parenthood for those first experiencing infertility in their mid to late thirties highlights the consequences of postponing parenthood and could result in involuntary childlessness and fewer children than desired. [ABSTRACT FROM AUTHOR]