Log Correlation Research Articles

Reactivity trends of surface-confined Co-tetraphenyl porphyrins and vitamin B 12 for the oxidation of 2-aminoethanethiol: Comparison with Co-phthalocyanines and oxidation of other thiols

We have investigated the electrocatalytic activity of tetraphenyl porphyrin, of substituted tetraphenyl porphyrins and of vitamin B 12 for the electro-oxidation of 2-aminoethanethiol, with the catalysts confined on graphite electrodes. Several N4-macrocyclic were used in order to have a great variety of formal potentials of the catalysts and compare this parameter with the catalytic activity. The electrocatalytic activity, measured as current at constant potential, increases with the formal potential of the catalysts as follows: Co-pentafluorotetraphenylporphyrin < Co-tetrahydroxytetraphenylporphyrin < Co-tetraphenylporphyrin < Co-tetrasulfophenylporphyrin < 2,2′,2′′,2′′′-tetra-aminotetraphenylporphyrin < tetramethoxytetraphenylporphyrin < vitamin B 12. Vitamin B 12 exhibits the maximum activity. A correlation of log I (at constant potential) vs. the formal potential E′ of the catalysts gives a volcano correlation when data of Co-phthalocyanines studied in previous work is included in the comparison. This clearly shows that the search for better catalysts for this reaction point to those N 4-macrocyclic complexes with Co(II)/(I) formal potentials close to −1.0 V vs. SCE which corresponds to an optimum situation for the interaction of the thiol with the active site. When comparing reactivity trends of similar catalysts for the oxidation of other thiols ( l-cysteine, mercaptoacetate and 2-mercaptoethanol) E′ max correlates linearly with the p Ka of the thiol.

Prediction of the thermodynamic properties of metal–chromate aqueous complexes to high temperatures and pressures and implications for the speciation of hexavalent chromium in some natural waters

Abstract Log–log correlation plots between the dissociation constants of known metal–chromate complexes and those of corresponding metal–sulfate complexes at 25 °C, 1 bar were used to derive the standard partial molal Gibbs free energies of formation of unknown metal–chromate complexes involving either (i) monovalent cations, divalent cations, and trivalent lanthanides or (ii) trivalent cations (excluding those of rare earth elements, REE) and tetravalent cations. For each of these two classes of ionic associations, empirical relationships between the standard partial molal volumes, isobaric heat capacities and entropies of known metal–chromate complexes and the corresponding thermodynamic properties of metal ions have been found. These data were utilized to evaluate the solute-characteristic parameters of the revised Helgeson–Kirkham–Flowers equation of state and to compute the thermodynamic properties of the dissociation reactions of metal–chromate complexes at high temperatures and pressures. Speciation of Cr(VI) in seawater and in shallow groundwaters interacting with serpentinites and ultramafites shows the importance of the NaCrO 4 - , MgCrO 4 ° , and CaCrO 4 ° aqueous complexes.

The influence of long-range transport on atmospheric mercury on Jeju Island, Korea

The concentrations of total gaseous mercury (TGM) and relevant environmental parameters were measured at a remote area on Jeju Island, Korea from May 2006 to May 2007. The hourly mean concentration of Hg for the entire study period was 3.85 ± 1.68 ng m − 3 (range of 0.10–17.9: n = 7450). The temporal patterns of Hg at the island site were characterized by the relative dominance in spring/fall over summer/winter and in daytime over nighttime. The possible impact of Asian dust (AD) on Hg distribution was examined by assessing its relationship with PM 10 data. Because of a strong inverse log–log correlation between Hg and PM 10 levels (above 200 µg m − 3 ), a direct relationship between the two parameters is difficult to account for. However, the analysis of air mass movement patterns confirmed that the Hg levels on Jeju Island were affected most by the combined effects of major source processes in the surrounding areas: industrial and AD (China), industrial (Korea), and volcanic activity (Japan).

Integrated description and evaluation of reservoirs based on seismic, logging, and geological data: Taking Dongying Formation Member 1 oil reservoir of No. 1 structure, Nanpu Sag as an example

Abstract Taking the Member 1 oil reservoir of Dongying Formation in Nanpu Sag as an example, this article puts forward an integrated study method for oil reservoir description and evaluation. First, with the correlation of seismic, log, and geological data, the isochronous stratigraphic framework of the oil reservoir is built up, sequence boundaries are interpreted, the sequence constrained prestack seismic inversion is processed, and a geological conceptual model of reservoir is established. Second, with the results of prestack seismic inversion and the Petrel software, the structure model of the isochronous stratigraphic framework and the quantitative geological database are built up. Third, through contrasting and selecting the most reasonable method of stochastic modeling, the reservoir facies modeling and the petrophysical modeling with the constraint of facies models are processed, the oil geological reserves are computed and evaluated, and some oil reservoirs are described finely. The study shows that the Member 1 oil reservoir is a layered, structure-controlled, edge water drive reservoir. It has thick sands, good properties, and complicated oil–water systems. The geological reserves estimated by the nine designed implementation models are the realization of Monte Carlo methods and conform to a certain probability distribution. The models are favorable for the reasonable evaluation of reserves.

Late Pleistocene coastal evolution of San Giovanni di Sinis, west Sardinia (Western Mediterranean)

The Upper Pleistocene succession of coastal deposits outcropping at San Giovanni di Sinis (west Sardinia) has been studied since the 1960s. However, the absence of consistent radiometric ages has allowed the production of competing stratigraphic subdivisions of these deposits with different Isotopic Stage (OIS/MIS) attributions. The succession is composed of sandy to gravelly shallow-marine, coastal aeolian and alluvial fan/plain deposits. Facies analysis and log correlations show the presence of three unconformities (T1, T2, T3) always overlain by shallow-marine deposits, cutting through the substrate, alluvial fan or aeolian sediments. We have collected three samples for Optically Stimulated Luminescence (OSL) dating at the top of each shallow-marine deposit. The succession is composed of four unconformity-bounded units (U1, U2, U3, U4), and the new OSL dates indicate the presence of three different sea-level highstands. The first Unit (U1), which is composed of shallow-marine to aeolian deposits and overlies transgressive surface T1, is related to a marine transgression during OIS 7 (186 ± 13 ky). Unit 2 is composed of continental deposits and formed during OIS 6. Unit 3 represents OIS 5 and overlies a transgressive surface (T2). More precisely, Subunit U3a is related to OIS 5e (120 ± 10 ky; Eu-Tyrrhenian or Eemian sensu strictu) and is characterized by shallow-marine to aeolian deposits developed during both transgressive and highstand phases. The following bay deposits of Subunit 3b are associated with OIS 5c (100 ± 5 ky) and record a second transgressive event (T3) and highstand phase occurred during the Neo-Tyrrhenian. The succession of San Giovanni di Sinis ends with continental deposits of Unit 4 associated to a sea-level fall that took place at the beginning of the last glacial phase (OIS 4).

Two-photon excited red upconversion luminescence of thulium ions doped GeS 2–In 2S 3–CsI glass

We report a novel phenomenon in GeS 2–In 2S 3–CsI chalcohalide glass doped with Tm 3+ ions. Under irradiation with an 808 nm laser diode, a bright red emission centered at 700 nm is observed for the first time in this glass. The log–log correlation between integrated emission intensity and pump power reveals that a two-photon absorption process is involved in the phenomenon, suggesting that the 3F 3,2 → 3H 6 transition of Tm 3+ ions is responsible for the appearance of the red emission. The results indicate that the indium (In) based chalcohalide glass containing Tm 3+ ions is expected to find applications in visible lasers, high density optical storage and three-dimensional color displays.

The Permian–Triassic boundary in Western Australia: evidence from the Bonaparte and Northern Perth basins—exploration implications

Several sedimentary basins in Western Australia contain petroleum reservoirs of Late Permian or older age that are overlain by thick shaly sequences (400–2,000 m) that have been assigned an Early Triassic age. The age of the base of the Triassic shales has been, and continues to be, contentious with strata being variously ascribed to the latest Permian (Changhsingian Stage) or wholly in the earliest Triassic (Induan Stage). In the Perth Basin the Permian-Triassic boundary appears to be located somewhere in the Hovea Member of the Kockatea Shale. In the Bonaparte Basin, the boundary would appear to be either in the uppermost Penguin Formation or at the boundary between the Penguin and Mairmull formations. The uncertainty of the boundary placement relates to the interpretation of the sedimentological, biostratigraphic and geochemical record in individual sections and basins. Major problems relate to the recognition, or even the presence of unconformities, complications related to the presence of reworked sediments and paleontological material (both conodonts and spore-pollen) and to the significance of geochemical shifts. The age of the basal Kockatea Shale (northern Perth Basin) and the basal Mt Goodwin Sub-group (Bonaparte Basin) is reassessed using palaeontological data, augmented by carbon isotopic measurements and geochemical analyses, supported by wireline log correlations and seismic profiles. The stratigraphy of the latest Permian to Early Triassic succession in the Bonaparte Basin is also revised, as is the nomenclature for the Early Triassic Arranoo Member of the Kockatea Shale in the northern Perth Basin. The Mt Goodwin Sub-group (new rank) is composed of the latest Permian Penguin Formation overlain by the Early Triassic Mairmull, Ascalon and Fishburn formations (all new).

Estimation of amorphous organic carbon/water partition coefficients, subcooled liquid aqueous solubilities, and n-octanol/water partition coefficients of nonpolar chlorinated aromatic compounds from chlorine fragment constants

This study aims to derive the relation between the number of chlorine atoms in chlorobenzenes, polychlorinated biphenyls (PCBs), dibenzo- p-dioxins (PCDDs), and dibenzofurans (PCDFs) and log K oc for linear partitioning between water and average amorphous organic carbon in soils or sediments. Because reliable determinations of log K oc are relatively sparse for chlorobenzenes and PCBs, and are even absent for PCDDs and PCDFs, a work-around solution was developed: First, the relation of n-octanol/water partitioning ( K ow) and (subcooled) liquid solubility ( S l) to the number of chlorines was investigated. Slopes for the linear correlation of log K ow with the number of chlorines (corrected for the number of ortho-chlorines in the case of PCBs) appeared identical for chlorobenzenes, PCBs, PCDDs, and PCDFs. Such was also the case for log S l. Slopes for the linear relation of chlorobenzenes and PCB log K oc values with the number of chlorines were similar for the various soils and sediments, though intercepts were different. The ortho-chlorine correction factor for PCB log K oc was equal to the ortho-chlorine correction factor for PCB log K ow and log S l. For PCDDs and PCDFs, a relation between log K oc and the number of chlorine atoms was derived by combining the chlorobenzenes/PCB log K oc − log K ow and log K oc − log S l relationships with log K ow (or S l)-chlorine number relations for PCDDs and PCDFs.

A NewFUSESurvey of Interstellar HD

We have used archival FUSE data to complete a survey of interstellar HD in 41 lines of sight with a wide range of extinctions. This follow up to an earlier survey was made to further assess the utility of HD as a cosmological probe; to analyze the HD formation process; and to see what trends with other interstellar properties were present in the data. We employed the curve-of-growth method, supported by line profile fitting, to derive accurate column densities of HD. We find that the N(HD)/2N(H2) ratio is substantially lower than the atomic D/H ratio and conclude that the molecular ratio has no bearing on cosmology, because local processes are responsible for the formation of HD. Based on correlations with E(B-V), H2, CO, and iron depletion, we find that HD is formed in the densest portion of the clouds; the slope of the logN(HD)/log(H2) correlation is greater than 1.0, caused by the destruction rate of HD declining more slowly than that of H2; and, as a sidelight, that the depletions are density dependent.

Correlation between Air Permeability and Saturated Hydraulic Conductivity: Unburned and Burned Soils

Prior research has shown a log–log correlation between ex situ air permeability (ka) measured at a matric potential of −50 and −100 cm H2O and saturated hydraulic conductivity (Ksat) in agricultural soils. We examined the applicability of a previously established log ka vs. log Ksat predictive relation in unburned and burned woodland–chaparral and coniferous soils. Specifically, we measured in situ ka in the field using the soil corer air permeameter (SCAP) and measured laboratory Ksat on soil cores. To determine postfire soil physical changes, Ksat was transformed into water permeability, kw Then ka and kw were compared in unburned and burned soils. The median ka was lower and median kw was higher in burned than unburned woodland–chaparral soils. The median ka and kw were both lower in burned than unburned coniferous soils. Despite these effects, the 95% prediction interval of the predictive relation includes 80% of the burned soils and 83% of all desert soils. The RMSE values of the predicted log Ksat and measured log Ksat were 0.371, 0.552, 0.588, and 0.511 m d−1 for unburned and burned woodland–chaparral and unburned and burned coniferous soils, respectively. In comparison, the RMSE for the predicted and measured log Ksat was 0.654 m d−1 for an agricultural data set. The overall RMSE for unburned and burned soils including the agricultural soils was 0.551 m d−1 This suggests that the predictive relation is applicable for unburned and burned desert soils for in situ ka measurements.

Marine transgressions in the mid-Cretaceous of the Cordilleran foreland basin re-interpreted as orogenic unloading deposits

Abstract A detailed stratigraphic and sedimentologic study of the Early Cenomanian Fish Scales Formation and the Barons Sandstone in southern Alberta, based on detailed core measurement and well log correlation, was undertaken in order to assess the principal controlling factors on the mid-Cretaceous stratigraphic fill of the Cordilleran foreland basin. Fine-grained units in the basin, such as the Fish Scales Formation (Mowry equivalent) and the Early Turonian Second White Specks Formation (Greenhorn equivalent), have traditionally been attributed to deposition during episodes of high eustatic sea levels. However, facies, allostratigraphy, and isopach patterns of the latest Albian Westgate, Fish Scales, mid–late Cenomanian Belle Fourche and Second White Specks formations in southern Alberta suggest that strata were deposited alternately during orogenic loading periods and unloading periods. We interpreted the Fish Scales Formation, a deposit formed during the marine transgression of the Mowry Seaway in the latest Albian–earliest Cenomanian, to have been deposited in a wide shallow interior seaway during an orogenic unloading period. The Barons Sandstone, interbedded with the mudstone of the Fish Scales Formation, is interpreted as a regressive shoreface, distributary channel and barrier island sandstone deposited during the unloading period. We also tentatively interpreted the Second White Specks Formation, a regional stratigraphic marker deposited during the so-called peak eustatic sea level in the Early Turonian, to have been deposited in a wide shallow interior seaway during a period of regional orogenic unloading. This study questions the significance of the Mowry Shale and Greenhorn Formation as indicators of eustatic highstands of sea level, and suggests regional tectonism as the primary control on basin evolution.

Thyroid-Stimulating Hormone and Free Thyroxine Levels in Persons with HFE C282Y Homozygosity, a Common Hemochromatosis Genotype: The HEIRS Study

Relationships of thyroid and iron measures in large cohorts are unreported. We evaluated thyroid-stimulating hormone (TSH) and free thyroxine (T4) in white participants of the primary care-based Hemochromatosis and Iron Overload Screening (HEIRS) Study. We measured serum TSH and free T4 in 176 HFE C282Y homozygotes without previous hemochromatosis diagnoses and in 312 controls without HFE C282Y or H63D who had normal serum iron measures and were matched to C282Y homozygotes for Field Center, age group, and initial screening date. We defined hypothyroidism as having TSH >5.00 mIU/L and free T4 <0.70 ng/dL, and hyperthyroidism as having TSH <0.400 mIU/L and free T4 >1.85 ng/dL. Multivariate analyses were performed using age, sex, Field Center, log(10) serum ferritin (SF), HFE genotype, log(10) TSH, and log(10) free T4. Prevalences of hypothyroidism in C282Y homozygotes and controls were 1.7% and 1.3%, respectively, and of hyperthyroidism 0% and 1.0%, respectively. Corresponding prevalences did not differ significantly. Correlations of log(10) SF with log(10) free T4 were positive (p = 0.2368, C282Y homozygotes; p = 0.0492, controls). Independent predictors of log(10) free T4 were log(10) TSH (negative association) and age (positive association); positive predictors of log(10) SF were age, male sex, and C282Y homozygosity. Proportions of C282Y homozygotes and controls who took medications to supplement or suppress thyroid function did not differ significantly. Prevalences of hypothyroidism and hyperthyroidism are similar in C282Y homozygotes without previous hemochromatosis diagnoses and controls. In controls, there is a significant positive association of SF with free T4. We conclude that there is no rationale for routine measurement of TSH or free T4 levels in hemochromatosis or iron overload screening programs.

A new Neogene biostratigraphy for Denmark

In Denmark most of the water used in private households, in the industry and for irrigation in agriculture comes from subsurface aquifers. Some of the most important aquifers in Jylland, western Denmark, are sand layers deposited from 23 to 15 Ma ago, in the Early Neogene (Early to Middle Miocene). About 23 Ma ago, in the Early Miocene, the coastline ran NW–SE across present-day Jylland (Rasmussen 2004). Global climatic variations led to major sea-level changes (Zachos et al. 2001), which in combination with increased sediment transport from the north (the present Norway) resulted in deposition of several huge, fluvio-deltaic sand systems intercalated with marine clay (e.g. Rasmussen 1961; Rasmussen 2004; Rasmussen &amp; Dybkjær 2005). The Geological Survey of Denmark and Greenland (GEUS) and the regional Environment Centres (the former counties (amter)) in Jylland are working in close cooperation to study the Early Neogene succession; the main purposes are: (1) to find new aquifers, (2) to map the extent of known aquifers and clarify their mutual relationships, in order to evaluate the size of the water resources and optimise production, and (3) to protect the aquifers from pollution due to leaching from the surface. In order to map the complex sedimentary succession, it has been necessary to combine several geological disciplines, including seismic interpretation, sedimentology, correlation of geophysical logs, and biostratigraphy (e.g. Dybkjær 2004; Rasmussen 2004; Rasmussen et al. 2004; Piasecki 2005; Rasmussen &amp; Dybkjær 2005; Dybkjær &amp; Rasmussen 2007). This article shows some results of a detailed dinoflagellate cyst stratigraphy, which is based on an extensive database (Fig. 1). We present here for the first time a dinoflagellate cyst zonation for the complete Neogene succession in the Danish area.

Probing concerted proton–electron transfer in phenol–imidazoles

A series of seven substituted 4,6-di-tert-butyl-2-(4,5-diarylimidazolyl)-phenols have been prepared and characterized, along with two related benzimidazole compounds. X-ray crystal structures of all of the compounds show that the phenol and imidazole rings are close to coplanar and are connected by an intramolecular ArOHN hydrogen bond. One-electron oxidation of these compounds occurs with movement of the phenolic proton to the imidazole base by concerted proton-electron transfer (CPET) to yield fairly stable distonic radical cations. These phenol-base compounds are a valuable system in which to examine the key features of CPET. Kinetic measurements of bimolecular CPET oxidations, with E(rxn) between +0.04 and -0.33 V, give rate constants from (6.3 +/- 0.6) x 10(2) to (3.0 +/- 0.6) x 10(6) M(-1) s(-1). There is a good correlation of log(k) with DeltaG degrees , with only one of the 15 rate constants falling more than a factor of 5.2 from the correlation line. Substituents on the imidazole affect the (O-HN) hydrogen bond, as marked by variations in the (1)H NMR and calculated vibrational spectra and geometries. Crystallographic d(ON) values appear to be more strongly affected by crystal packing forces. However, there is almost no correlation of rate constants with any of these measured or computed parameters. Over this range of compounds from the same structural family, the dominant contributor to the differences in rate constant is the driving force DeltaG degrees .

Postmenstrual Age and CYP2D6 Polymorphisms Determine Tramadol O-demethylation in Critically Ill Neonates and Infants

To document determinants of O-demethylation in critically ill (pre)term neonates and infants, tramadol (M) and O-demethyl tramadol (M1) concentrations were quantified in eighty-six 24 h urine collections and 168 plasma samples. A significant correlation of urine log M/M1 (0.98, SD 0.66) and plasma log M/M1 (0.78, SD 0.45) with postmenstrual age (PMA) (r = -0.69 and -0.65) was observed. One-way analysis of variance documented a significant decrease in urine log and plasma log M/M1 with increasing CYP2D6 activity score (F value 11.6 and 22.55). PMA and CYP2D6 activity score determined the urine and plasma log M/M1 (R 0.59 and 0.64) in a forward multiple regression model. We therefore conclude that PMA and CYP2D6 polymorphisms determined O-demethylation activity in (pre)term neonates and young infants, illustrating the impact of pharmacogenetics on drug metabolism in neonates although a relevant part of the interindividual varaibility remained unexplained. Besides compound-specific relevance, CYP2D6 iso-enzyme specific data on in vivo ontogeny of O-demethylation can contribute to safer and more effective administration of drugs metabolized by the same route in this population.

Calcite cement in Permian deep-water sandstones, Delaware Basin, west Texas: Origin, distribution, and effect on reservoir properties

Calcite cement is the dominant control on reservoir quality in turbidite sandstones of the Upper Permian Bell Canyon Formation, Delaware Basin. These well-sorted, very fine-grained arkoses were deposited in a basin-floor setting by channel-levee systems terminating in broad lobes. Calcite cement distribution in the East Ford and Geraldine Ford fields was mapped using core, log, and thin-section data. Calcite is concentrated in tightly cemented zones that are mostly less than 1 ft (0.3 m) thick. Areas that have high percentages of calcite-cemented sandstone (20%) occur along the margins of the sandstone bodies, in overbank and lobe deposits, where sandstone pinches out into siltstone. Areas that have the lowest percentage of calcite-cemented sandstone (10%) occur where the sandstone is thickest, in the channel facies. Isotopic composition of the calcite (13C = 1.8 to 3.0 [relative to the Peedee belemnite, PDB], 18O = 4.6 to 6.3 [PDB]) is consistent with the source of calcium carbonate being from dissolution of detrital carbonate rock fragments and marine skeletal debris. Because internal sources of calcite were apparently insufficient to account for the cement volume, cement components are interpreted as having been transported into the sandstones from organic-rich basinal siltstones and limestones. Feldspars buffered acidic formation waters near where they entered the sandstone, resulting in calcite concentrated near the sandstone margins. The calcite formed near maximum burial depths of 4800 ft (1.5 km) and temperatures of 104F (40C) from marine pore waters with 18O of approximately 0 (relative to standard mean ocean water). Most of the calcite-cemented zones are interpreted as being concretions that extend no more than a few meters laterally. Production data and geophysical log correlations suggest that some cemented zones are laterally continuous at least 1000 ft (300 m) and cause vertical reservoir compartmentalization. Laterally extensive calcite layers may be associated with the base of turbidite deposits.

Comparison of Species Sensitivity Distributions Derived from Interspecies Correlation Models to Distributions used to Derive Water Quality Criteria

Species sensitivity distributions (SSD) require a large number of measured toxicity values to define a hazard level protective of multiple species. This investigation comprehensively evaluated the accuracy of SSDs generated from toxicity values predicted from interspecies correlation estimation (ICE) models. ICE models are log-log correlations of multiple chemical toxicity values for a pair of species that allow the toxicity of multiple species to be predicted from a single measured acute toxicity value for a surrogate species. ICE SSDs were generated using four surrogate species (fathead minnow, Pimephales promelas; rainbow trout, Oncorhynchus mykiss; sheepshead minnow, Cyprinodon varigatus; and water flea, Daphnia magna). ICE-based hazard concentrations (HC5s) from the 5th percentile of the log-logistic distribution of toxicity values were compared to HC5s determined from the acute toxicity of 55 chemicals from the United States Environmental Protection Agency Ambient Water Quality Criteria (AWQC). Measured fish and invertebrate acute toxicity data and HC5s from the AWQC data sets were compared to ICE-based HC5s. Surrogate species choice was found to be an important consideration in developing predictive HC5s. These results illustrated that fish predict fish betterthan invertebrates and D. magna predicted invertebrates better than most fish. For example, a mixed model of predicted fish and invertebrates from fathead minnow and D. magna as surrogate species provided predictive relationships with an average factor of 3.0 (+/- 6.7) over 7 orders of toxic magnitude and several chemical classes (HC5(predicted)/HC5(measured)). The application of ICE models is recommended as a valid approach for generating SSDs and hazard concentrations for chemicals with limited toxicity data.

Kinetic study of heterogeneous catalytic hydrogenation of cyclohexene to cyclohexane in ionic liquid–alcohols mixtures

Abstract Heterogeneous catalytic hydrogenation of cyclohexene, catalyzed by Pt/Al2O3, was carried out in solutions of 2-hydroxyethylammonium formate (a room temperature ionic liquid, RTIL) mixed with methanol, ethanol and propan-2-ol at 25 °C. The rate constants of the reaction in ionic liquid alcohol mixtures were higher than alcohol alone. First-order rate constant of the reaction in the RTIL relative to propan-2-ol is approximately 28. Furthermore, the rate constant of the reaction increases with the mole fraction of the ionic liquid. Single-parameter correlations of log k vs. normalized polarity parameter ( E T N ), hydrogen-bond acceptor basicity (β) and hydrogen-bond donor acidity (α) do not give acceptable results in the solutions. In addition, log k does not show an acceptable dual-parameter correlation with π* (dipolarity/polarizibility, one of the Kamlet–Taft parameters for solvent that shows the dipolarity of the solvent) and α, π* and β and E T N and β. However single-parameter correlation of log k vs. π* gives reasonable results. The increase of the reaction rate with π* is attributed to the non-polar nature of the reactants.

Evaluation of Coronary Calcium Score by Multidetector Computed Tomography in Relation to Endothelial Function and Inflammatory Markers in Asymptomatic Individuals

Coronary calcification has been correlated with the presence and extent of coronary artery disease (CAD), so in the present study the associations between coronary artery calcification score (CACS) and endothelial dysfunction, as well as the important inflammatory markers C-reactive protein (CRP), interleukin (IL)-6, and oxidized low-density lipoprotein (OxLDL), were studied in asymptomatic individuals at intermediate risk for CAD. The study group comprised 177 subjects (103 males) aged 50.6+/-5.9 years. CACS was measured by multidetector computed tomography using the Agatston method. Endothelium-dependent flow-mediated dilatation (FMD) and endothelium-independent nitroglycerin-mediated dilatation (NMD) were measured by high-resolution external brachial ultrasound. Coronary artery calcification (CAC) was detected in 82 subjects (52 males), and the median CACS was 143 [31-311.25] units. After adjusting for gender and body mass index, log (CACS +1) correlated positively with age (r=0.401, p<0.001) and IL-6 levels (r=0.442, p<0.001), and negatively with FMD (r=-0.511, p<0.001). The correlations of log (CACS +1) with CRP and OxLDL levels, and with NMD, were non-significant. In a multivariate-adjusted logistic regression model, age (odds ratio (OR) =1.083 [1.014-1.156]), serum IL-6 level (OR=3.837 [2.166-6.798]) and FMD (OR=0.851 [0.793-0.913]) were significantly and independently associated with CAC. Peripheral endothelial function inversely correlated with CACS, whereas IL-6 level was associated with CACS. Testing for endothelial function and IL-6 level may improve cardiovascular risk assessment and help target the therapeutic strategies in asymptomatic patients at intermediate CAD risk.

DNA Polymerase β Fidelity: Halomethylene-Modified Leaving Groups in Pre-Steady-State Kinetic Analysis Reveal Differences at the Chemical Transition State

The mechanism of DNA polymerase beta-catalyzed nucleotidyl transfer consists of chemical steps involving primer 3' OH deprotonation, nucleophilic attack, and pyrophosphate leaving-group elimination, preceded by dNTP binding which induces a large-amplitude conformational change for Watson-Crick nascent base pairs. Ambiguity in the nature of the rate-limiting step and active-site structural differences between correct and incorrect base-paired transition states remain obstacles to understanding DNA replication fidelity. Analogues of dGTP where the beta-gamma bridging oxygen is replaced with fluorine-substituted methylene groups have been shown to probe the contribution of leaving-group elimination to the overall catalytic rate (Biochemistry 46, 461-471). Here, the analysis is expanded substantially to include a broad range of halogen substituents with disparate steric and electronic properties. Evaluation of linear free energy relationships for incorporation of dGTP analogues opposite either template base C or T reveals a strong correlation of log(kpol) to leaving group pKa. Significantly different kpol behavior is observed with a subset of the analogues, with magnitude dependent on the identity of the nascent base pair. This observation, and the absence of an analogous effect on ground state analogue binding (Kd values), points to active-site structural differences at the chemical transition state. Reduced catalysis with bulky halo-containing substrates is manifested in the fidelity of T-G incorporation, where the CCl2-bridging analogue shows a 27-fold increase in fidelity over the natural dGTP. Solvent pH and deuterium isotope-effect data are also used to evaluate mechanistic differences between correct and mispaired incorporation.