Energy

Distribution by Scientific Domains
Distribution within Chemistry

Kinds of Energy

  • Gibb energy
  • Gibb free energy
  • acoustic energy
  • activation energy
  • adsorption energy
  • apparent activation energy
  • aromatic stabilization energy
  • association energy
  • atomization energy
  • available energy
  • available potential energy
  • band gap energy
  • band-gap energy
  • bandgap energy
  • beam energy
  • bending energy
  • binding energy
  • binding free energy
  • bond dissociation energy
  • bond energy
  • bonding energy
  • calculated activation energy
  • calculated energy
  • cavitation energy
  • cellular energy
  • chemical energy
  • cohesive energy
  • collision energy
  • complexation energy
  • conformational energy
  • core-excitation energy
  • correlation energy
  • coulomb energy
  • daily energy
  • dark energy
  • detachment energy
  • dietary energy
  • different energy
  • digestible energy
  • dissipated energy
  • dissipation energy
  • dissociation energy
  • effective activation energy
  • elastic energy
  • electric energy
  • electrical energy
  • electromagnetic energy
  • electron binding energy
  • electron energy
  • electronic energy
  • electrostatic energy
  • electrostatic free energy
  • electrostatic interaction energy
  • emission energy
  • excess Gibb energy
  • excess energy
  • exchange energy
  • excitation energy
  • exciton binding energy
  • exciton energy
  • fermi energy
  • flow activation energy
  • formation energy
  • fracture energy
  • free energy
  • gap energy
  • geothermal energy
  • gravitational potential energy
  • gross energy
  • ground state energy
  • h bond dissociation energy
  • heat energy
  • helmholtz free energy
  • high activation energy
  • high energy
  • high triplet energy
  • homo energy
  • hydration free energy
  • hydrogen bonding energy
  • impact energy
  • incident energy
  • increased energy
  • input energy
  • interaction energy
  • interface energy
  • interfacial energy
  • intermolecular interaction energy
  • internal energy
  • ion energy
  • ionization energy
  • kinetic energy
  • laser energy
  • lattice energy
  • light energy
  • little energy
  • low activation energy
  • low collision energy
  • low energy
  • low surface energy
  • lower activation energy
  • lower energy
  • lowest energy
  • lumo energy
  • magnetic energy
  • mean energy
  • mechanical energy
  • metabolizable energy
  • microwave energy
  • minimum energy
  • molecular energy
  • molecular orbital energy
  • net energy
  • new energy
  • orbital energy
  • peak energy
  • phonon energy
  • photon energy
  • polarization energy
  • potential energy
  • primary energy
  • pulse energy
  • radiation energy
  • radiofrequency energy
  • reaction energy
  • relative energy
  • renewable energy
  • reorganization energy
  • resonance energy
  • rf energy
  • same energy
  • similar energy
  • social energy
  • solar energy
  • solvation energy
  • solvation free energy
  • solvent reorganization energy
  • specific energy
  • specific mechanical energy
  • stabilization energy
  • state energy
  • stored energy
  • strain energy
  • sufficient energy
  • surface energy
  • surface free energy
  • thermal energy
  • threshold energy
  • total energy
  • transition energy
  • triplet energy
  • turbulent kinetic energy
  • ultrasonic energy
  • vertical detachment energy
  • vertical excitation energy
  • vertical ionization energy
  • vibrational energy
  • wave energy
  • wind energy
  • x-ray energy
  • zero-point energy

  • Terms modified by Energy

  • energy absorption
  • energy acquisition
  • energy agency
  • energy allocation
  • energy analysis
  • energy application
  • energy approach
  • energy availability
  • energy available
  • energy balance
  • energy balance equation
  • energy balance model
  • energy band
  • energy band gap
  • energy bands
  • energy barrier
  • energy budget
  • energy calculation
  • energy carrier
  • energy change
  • energy charge
  • energy component
  • energy concentration
  • energy conformation
  • energy conformer
  • energy conservation
  • energy conservation equation
  • energy constraint
  • energy consumption
  • energy content
  • energy contribution
  • energy conversion
  • energy conversion efficiency
  • energy conversion system
  • energy cosmic ray
  • energy cost
  • energy crisis
  • energy criterion
  • energy crop
  • energy curve
  • energy cycle
  • energy decay
  • energy decomposition analysis
  • energy decomposition scheme
  • energy decrease
  • energy decreased
  • energy deficiency
  • energy delivery
  • energy demand
  • energy density
  • energy density analysis
  • energy density material
  • energy dependence
  • energy dependent
  • energy depletion
  • energy deposition
  • energy deprivation
  • energy development
  • energy diagram
  • energy difference
  • energy digestibility
  • energy dispersion
  • energy dispersive analysis
  • energy dispersive spectroscopy
  • energy dispersive x-ray
  • energy dispersive x-ray analysis
  • energy dispersive x-ray diffraction
  • energy dispersive x-ray spectrometry
  • energy dispersive x-ray spectroscopy
  • energy dissipation
  • energy dissipation rate
  • energy distribution
  • energy donor
  • energy drink
  • energy dynamics
  • energy e
  • energy efficiency
  • energy efficient
  • energy eigenvalue
  • energy electron diffraction
  • energy equation
  • energy estimate
  • energy estimation
  • energy evaluation
  • energy exchange
  • energy expenditure
  • energy expression
  • energy extraction
  • energy failure
  • energy field
  • energy flow
  • energy fluctuation
  • energy flux
  • energy form
  • energy function
  • energy functional
  • energy gain
  • energy gap
  • energy generation
  • energy harvesting
  • energy homeostasi
  • energy imbalance
  • energy industry
  • energy input
  • energy intake
  • energy intake rate
  • energy intensity
  • energy landscapes
  • energy level
  • energy limitation
  • energy loss
  • energy loss spectroscopy
  • energy malnutrition
  • energy management
  • energy market
  • energy material
  • energy metabolism
  • energy method
  • energy methods
  • energy migration
  • energy minimization
  • energy minimum
  • energy model
  • energy norm
  • energy optimization
  • energy option
  • energy output
  • energy parameter
  • energy partitioning
  • energy path
  • energy penalty
  • energy performance
  • energy policy
  • energy potential
  • energy prediction
  • energy price
  • energy principle
  • energy production
  • energy products
  • energy profile
  • energy radiation
  • energy range
  • energy ratio
  • energy recovery
  • energy refinement
  • energy regulation
  • energy relationship
  • energy relationships
  • energy relaxation
  • energy release
  • energy release rate
  • energy requirement
  • energy reserve
  • energy resolution
  • energy resource
  • energy restriction
  • energy retention
  • energy retention efficiency
  • energy saving
  • energy savings
  • energy scale
  • energy sector
  • energy security
  • energy sensor
  • energy separation
  • energy shift
  • energy shortage
  • energy side
  • energy site
  • energy source
  • energy source used
  • energy spectrum
  • energy splitting
  • energy state
  • energy states
  • energy status
  • energy storage
  • energy storage material
  • energy storage system
  • energy store
  • energy strategy
  • energy stress
  • energy structure
  • energy substrate
  • energy supply
  • energy surface
  • energy system
  • energy technology
  • energy term
  • energy transduction
  • energy transfer
  • energy transfer cassette
  • energy transfer efficiency
  • energy transfer mechanism
  • energy transfer process
  • energy transfer rate
  • energy transformation
  • energy turnover
  • energy usage
  • energy use
  • energy used
  • energy utilization
  • energy utilization efficiency
  • energy value
  • energy x-ray absorptiometry
  • energy yield

  • Selected Abstracts


    EXTRUSION COOKING OF BLENDS OF SOY FLOUR AND SWEET POTATO FLOUR ON SPECIFIC MECHANICAL ENERGY (SME), EXTRUDATE TEMPERATURE AND TORQUE

    JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 4 2001
    M. O. IWE
    Defatted soy flour and sweet potato flour containing 18% moisture were mixed in a pilot mixer, and extruded in an Almex-Bettenfeld single-screw extruder operated at varying rotational speed and die diameter. A central composite, rotatable nearly orthogonal design, which required 23 experiments for three factors (feed composition (fc), screw speed (ss) and die diameter (dd)) was developed and used for the generation of response surfaces. Effects of the extrusion variables on specific mechanical energy (SME), extrudate temperature (ET), and torque (T) were evaluated using response surface analysis. Results showed that product temperature increased with increases in die diameter, screw speed and feed composition. However, the effect of die diameter was greater than those of screw speed and feed composition. Decrease in die diameter with increase in sweet potato content increased torque. Screw speed exhibited a linear effect on torque. [source]


    JOURNAL of FOOD PROCESSING and PRESERVATION SEP 2000 Vol-24.4. DEVELOPMENT of A PROCESS FOR DETECTING NONTHERMAL EFFECTS of MICROWAVE ENERGY ON MICROORGANISMS AT LOW TEMPERATURE,

    JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 4 2000
    MICHAEL KOZEMPEL
    We developed an experimental process capable of isolating thermal and nonthermal effects of microwave energy relative to the destruction of microorganisms at low temperature. the concept combines instantaneous energy input to the food system by microwaves with rapid removal of thermal energy. the process used a double tube heat exchanger inside a continuous microwave dryer. the outer tube was transparent to microwaves, whereas the inner tube was stainless steel and was used for cooling the system. the microwave energy, 5,6 kW power, was absorbed by the process fluid in the annulus. the cooling water flowing in the inner tube removed the thermal energy from the process fluid to control temperature at or below 45C. the process was at turbulent flow to assure a uniform temperature and dwell time. There were no detected nonthermal effects from microwave energy for yeast, Pediococcus sp., Escherichia coli, Listeria innocua, or Enterobacter aerogenes in various test fluids, such as water, liquid egg, beer, apple juice, apple cider, and tomato juice. [source]


    SEAWEED ABUNDANCE AND DIVERSITY IN HIGH ENERGY AND LOW ENERGY AREAS AT PORT ARANSAS, TEXAS JETTIES

    JOURNAL OF PHYCOLOGY, Issue 3 2001
    Article first published online: 24 SEP 200
    Agan, J. C. & Lehman, R. L. Department of Physical and Life Sciences, Texas A&M University-Corpus Christi 6300 Ocean Dr., Corpus Christi, TX 78412 USA Benthic algal sampling from high and low energy zones at a selected site on the south jetty at Port Aransas, Texas was completed between April 1999 and February 2000. Species composition and seasonal periodicity in relation to temperature and salinity fluctuations were determined. Dominant plants throughout the year included Bryocladia cuspidata, Bryocladia thyrsigera, Gelidium pusillum, Centroceras clavulatum, Ulva fasciata, and Padina gymnospora. The Rhodophyta dominated species coverage, along with biomass accumulation, although Chlorophyta species accrued the greatest biomass on the high energy side in April and June sampling. Chlorophyta are important to benthic coverage and biomass in the shallowest of waters, despite being fewer in species richness. Phaeophyta species including Petalonia fascia, Hincksia mitchelliae, and Ectocarpus siliculosus were found only during the cooler months. Padina gymnospora was the one exception as it was collected year-round. Results indicate that a greater Rhodophyta abundance was found on the channel side (low energy), where as, the surf side (high energy) contained a greater Chlorophyta abundance. Phaeophyta abundance for both high and low energy sites were comparable possibly due to the greater depth of water in which they are located. Little variance occurred in average biomass accumulation throughout the year. Highest biomass was in August (216.613g dry weight) with lowest occurring in April (107.4205g dry weight). [source]


    SEAWEED ABUNDANCE AND DIVERSITY IN HIGH ENERGY AND LOW ENERGY AREAS AT PORT ARANSAS, TEXAS JETTIES

    JOURNAL OF PHYCOLOGY, Issue 2001
    Article first published online: 9 OCT 200
    Agan, J. C. & Lehman, R. L. Department of Physical and Life Sciences, Texas A&M University-Corpus Christi 6300 Ocean Dr., Corpus Christi, TX 78412 USA Benthic algal sampling from high and low energy zones at a selected site on the south jetty at Port Aransas, Texas was completed between April 1999 and February 2000. Species composition and seasonal periodicity in relation to temperature and salinity fluctuations were determined. Dominant plants throughout the year included Bryocladia cuspidata, Bryocladia thyrsigera, Gelidium pusillum, Centroceras clavulatum, Ulva fasciata, and Padina gymnospora. The Rhodophyta dominated species coverage, along with biomass accumulation, although Chlorophyta species accrued the greatest biomass on the high energy side in April and June sampling. Chlorophyta are important to benthic coverage and biomass in the shallowest of waters, despite being fewer in species richness. Phaeophyta species including Petalonia fascia, Hincksia mitchelliae, and Ectocarpus siliculosus were found only during the cooler months. Padina gymnospora was the one exception as it was collected year-round. Results indicate that a greater Rhodophyta abundance was found on the channel side (low energy), where as, the surf side (high energy) contained a greater Chlorophyta abundance. Phaeophyta abundance for both high and low energy sites were comparable possibly due to the greater depth of water in which they are located. Little variance occurred in average biomass accumulation throughout the year. Highest biomass was in August (216.613g dry weight) with lowest occurring in April (107.4205g dry weight). [source]


    EXCHANGES OF INFORMATION, ENERGY & MATERIALS IN SYMBIOSES

    JOURNAL OF PHYCOLOGY, Issue 2000
    J.A. Raven
    Symbiosis is important in the cell and environmental biology of algae. Some examples involving the author and numerous collaborators include: 1) chloroplasts of eukaryotic algae arose from endosymbioses. Plastids are incapable of independent existence; most of the genes of the cyanobacterial photobiont have been lost, and the majority of the rest have been transferred to the nuclear genome. Some of the genes retained by the plastid are those whose transcription is controlled by environmental cues transduced by the organelle. The general trend is for organelle genes to be transferred to the nucleus, escaping plastid redox activities generating mutagenic free radicals; 2) symbioses involving potentially free-living photobionts include marine lichens and sponges with cyanobacterial symbionts. For the lichen, Lichina, inorganic carbon acquisition appears to involve inorganic carbon transport by the mycobiont, and for the sponge, Cymbastella, the flagellar activity of the sponge is probably important for inorganic carbon supply to the photobiont; 3) the Australasian fucalean, Notheia, is an obligate epiphyte on the fucaleans, Hormosira and Xiphophora; the four species involved all contain the hexitol, altritol. Notheia anomala is known to be phyletically-distant from the other five altritol-containing species. Can Notheia synthesize altritol, or is it obtained from the phorophyte?; 4) Sacoglossan gastropods retain kleptoplastids (not strictly symbionts) from ulvophycean (or rhodophycean) marine algae. Analyses of the natural abundance of stable carbon isotopes suggest significant contribution of kleptoplastid photosynthesis to the carbon and energy budget of the mollusks. [source]


    Front and Back Covers, Volume 21, Number 3.

    ANTHROPOLOGY TODAY, Issue 3 2005
    June 200
    Front and back cover caption, volume 21 issue 3 ENERGY AND VERNACULAR ARCHITECTURE The photo on the front and back cover illustrates the article by Annette Henning in this issue. A solar collector is hoisted onto the roof of a Swedish house. In Sweden, the most common solar heating systems are those that supply hot water for both heating and general domestic hot water purposes. Contrary to popular belief, solar collectors are not dependent on a high air temperature, but produce heat throughout the year, whenever there is a clear sky. In her article, Annette Henning examines the actual and potential role of anthropology in energy studies. She reflects on her own experience of the trials of working as an anthropologist in the energy sector, where economists and technical expertise reign, and where production- and distribution-oriented approaches prevail. There is a great deal of resistance to anthropological contributions, in part because anthropologists have made so little effort to be heard in the public domain on this issue. In his editorial, Hal Wilhite makes the case for "energy anthropology". He argues that anthropologists have paid insufficient attention to one of the most urgent problems facing the world, namely our patterns of energy consumption and their economic and environmental consequences. Increasing consumerism in developing countries makes anthropological approaches indispensable, particularly in finding ways to moderate energy consumption and to help implement small-scale renewable energy initiatives. In his review of three of the latest books on vernacular architecture, Marcel Vellinga identifies architecture as a prominent cultural category and a major consumer of energy and resources, and thus a significant contributor to current environmental problems. Vellinga argues that anthropology should pay more attention to vernacular architecture as a locus of indigenous knowledge, to help the global community address the challenges of creating a sustainable built environment for all. ANTHROPOLOGY TODAY brings these contributions to your attention in the hope of stimulating discussion and promoting wider ethnographic research in areas of public concern. [source]


    Sulfur Dioxide and Water: Structures and Energies of the Hydrated Species SO2nH2O, [HSO3],nH2O, [SO3H],nH2O, and H2SO3nH2O (n = 0,8)

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2009
    Ralf Steudel
    Abstract The structures of a large number of hydrates of sulfur dioxide (SO2nH2O), of the sulfonate ion ([HSO3],nH2O), of the tautomeric hydrogensulfite anion ([SO3H],nH2O), and of sulfurous acid (H2SO3nH2O) with up to eight water molecules attached to these species have been optimized at the B3LYP/6-31G(2df,p) level of theory (DFT). The calculated vibrational frequencies allow the definite assignment of certain characteristic modes, and in this way a convincing interpretation of published spectra of aqueous SO2 as well as of SO2 adsorbed on very cold ice crystals has been achieved for the first time. Single-point calculations at the G3X(MP2) level of theory were used to calculate the binding energies of the water molecules in SO2nH2O as well as the relative stabilities of the isomeric anionic species [HSO3],nH2O and [SO3H],nH2O. Generally, the water molecules tend to stick together forming clusters, whereas the particular sulfur-containing molecule remains at the surface of the water cluster, but it is always strongly hydrogen-bonded. Only when there are more than six water molecules are the anions more or less completely surrounded by water molecules. DFT calculations erroneously predict that the gaseous hydrated sulfonate ions are more stable than the isomeric hydrogensulfite ions, even when hydrated with six water molecules. However, if these hydrated species are calculated as being embedded in a polar continuum simulating the aqueous phase, the hydrogensulfite ions are more stable than the sulfonate ions, in agreement with various spectroscopic observations on aqueous sulfite solutions. On the other hand, at the higher G3X(MP2) level, the gaseous hydrated hydrogensulfite anions are more stable than the corresponding sulfonate ions only if the number of water molecules is larger than four, whereas for the weakly hydrated anions the order of relative energies is reversed. The possible implications of these results for the enzymatic oxidation of "sulfite ions" ([HSO3], and [SO3H],) by sulfite oxidase are discussed. The conversion of SO26H2O into its isomer H2SO35H2O is predicted to be exothermic (,H298 = ,56.1 kJ,mol,1) and exergonic (,G298 = ,22.5 kJ,mol,1). ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]


    Theoretical studies of mechanisms of cycloaddition reaction between difluoromethylene carbene and acetone

    INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 2 2007
    Xiu Hui Lu
    Abstract Mechanisms of the cycloaddition reaction between singlet difluoromethylene carbene and acetone have been investigated with the second-order Mller,Plesset (MP2)/6-31G* method, including geometry optimization and vibrational analysis. Energies for the involved stationary points on the potential energy surface (PES) are corrected by zero-point energy (ZPE) and CCSD(T)/6-31G* single-point calculations. From the PES obtained with the CCSD(T)//MP2/6-31G* method for the cycloaddition reaction between singlet difluoromethylene carbene and acetone, it can be predicted that path B of reactions 2 and 3 should be two competitive leading channels of the cycloaddition reaction between difluoromethylene carbene and acetone. The former consists of two steps: (i) the two reactants first form a four-membered ring intermediate, INT2, which is a barrier-free exothermic reaction of 97.8 kJ/mol; (ii) the intermediate INT2 isomerizes to a four-membered product P2b via a transition state TS2b with an energy barrier of 24.9 kJ/mol, which results from the methyl group transfer. The latter proceeds in three steps: (i) the two reactants first form an intermediate, INT1c, through a barrier-free exothermic reaction of 199.4 kJ/mol; (ii) the intermediate INT1c further reacts with acetone to form a polycyclic intermediate, INT3, which is also a barrier-free exothermic reaction of 27.4 kJ/mol; and (iii) INT3 isomerizes to a polycyclic product P3 via a transition state TS3 with an energy barrier of 25.8 kJ/mol. 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source]


    Comparison of some representative density functional theory and wave function theory methods for the studies of amino acids

    JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 4 2009
    Wenbo Yu
    Abstract Energies of different conformers of 22 amino acid molecules and their protonated and deprotonated species were calculated by some density functional theory (DFT; SVWN, B3LYP, B3PW91, MPWB1K, BHandHLYP) and wave function theory (WFT; HF, MP2) methods with the 6-311++G(d,p) basis set to obtain the relative conformer energies, vertical electron detachment energies, deprotonation energies, and proton affinities. Taking the CCSD/6-311++G(d,p) results as the references, the performances of the tested DFT and WFT methods for amino acids with various intramolecular hydrogen bonds were determined. The BHandHLYP method was the best overall performer among the tested DFT methods, and its accuracy was even better than that of the more expensive MP2 method. The computational dependencies of the five DFT methods and the HF and MP2 methods on the basis sets were further examined with the 6-31G(d,p), 6-311++G(d,p), aug-cc-pVDZ, 6-311++G(2df,p), and aug-cc-pVTZ basis sets. The differences between the small and large basis set results have decreased quickly for the hybrid generalized gradient approximation (GGA) methods. The basis set convergence of the MP2 results has been, however, very slow. Considering both the cost and the accuracy, the BHandHLYP functional with the 6-311++G(d,p) basis set is the best choice for the amino acid systems that are rich in hydrogen bonds. 2008 Wiley Periodicals, Inc. J Comput Chem 2009 [source]


    Ab initio direct dynamics studies on the reactions of chlorine atom with CH3,nFnCH2OH (n = 1,3)

    JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 16 2007
    Ying Wang
    Abstract The hydrogen abstraction reactions of Cl atom with a series of fluorinated alcohols, i.e., CH3,nFnCH2OH + Cl (n = 1,3) (R1,R3) have been studied systematically by ab initio direct dynamics method and the canonical variational transition state theory (CVT). The potential energy surface information is calculated at the MP2/6-311G(d,p) level. Energies along the minimum energy paths are improved by a series of single-point calculations at the higher modified GAUSSIAN-2 (G2M) level of theory. Theoretical analysis shows that three kinds of hydrogen atoms can be abstracted from the reactants CH2FCH2OH and CHF2CH2OH, and for CF3CH2OH, two possible pathways are found. The rate constants for each reaction channel are evaluated by CVT with the small-curvature tunneling correction (SCT) over a wide range of temperature from 200 to 2000 K. The calculated CVT/SCT rate constants are in good agreement with the available experimental values for the reactions CHF2CH2OH + Cl and CF3CH2OH + Cl. However, for the reaction CH2FCH2OH + Cl, there is negative temperature dependence below 500 K, which is different from the experimental fitted. It is shown that in the low temperature ranges, the three reactions all proceed predominantly via H-abstraction from the methylene positions, and with the increase of the temperature the H-abstraction channels from the fluorinated-methyl positions should be taken into account, while the H-abstraction channels from the hydroxyl groups are negligible over the whole temperature ranges. Also, the reactivity decreases substantially with fluorine substitution at the methyl position of alcohol. 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [source]


    Energies, structures, and electronic properties of molecules in solution with the C-PCM solvation model

    JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 6 2003
    Maurizio Cossi
    Abstract The conductor-like solvation model, as developed in the framework of the polarizable continuum model (PCM), has been reformulated and newly implemented in order to compute energies, geometric structures, harmonic frequencies, and electronic properties in solution for any chemical system that can be studied in vacuo. Particular attention is devoted to large systems requiring suitable iterative algorithms to compute the solvation charges: the fast multipole method (FMM) has been extensively used to ensure a linear scaling of the computational times with the size of the solute. A number of test applications are presented to evaluate the performances of the method. 2003 Wiley Periodicals, Inc. J Comput Chem 24: 669,681, 2003 [source]


    Direct hydride transfer in the reaction mechanism of quinoprotein alcohol dehydrogenases: a quantum mechanical investigation

    JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 15 2001
    A. Jongejan
    Abstract Oxidation of alcohols by direct hydride transfer to the pyrroloquinoline quinone (PQQ) cofactor of quinoprotein alcohol dehydrogenases has been studied using ab initio quantum mechanical methods. Energies and geometries were calculated at the 6-31G(d,p) level of theory. Comparison of the results obtained for PQQ and several derivatives with available structural and spectroscopic data served to judge the feasibility of the calculations. The role of calcium in the enzymatic reaction mechanism has been investigated. Transition state searches have been conducted at the semiempirical and STO-3G(d) level of theory. It is concluded that hydride transfer from the C,-position of the substrate alcohol (or aldehyde) directly to the C(5) carbon of PQQ is energetically feasible. 2001 John Wiley & Sons, Inc. J Comput Chem 22: 1732,1749, 2001 [source]


    The Use of Atomic Charges and Orbital Energies as Hydrogen-bonding-donor Parameters for QSAR Studies: Comparison of MNDO, AM1 and PM3 Methods

    JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 6 2000
    TARAVAT GHAFOURIAN
    Hydrogen-bonding, important in drug-receptor interactions, also determines the solubility and partitioning of drugs between phases. It is, therefore, important to incorporate the effects of hydrogen-bonding in studies of quantitative structure-activity relationships (QSAR). In this study the atomic charge on the most positively charged hydrogen atom in a molecule and the energy of the lowest unoccupied molecular orbital (LUMO) have been used as a measure of hydrogen-bond-donor capacity. For several hydrogen-bonding acids the Mulliken atomic charges and the energy of the LUMO produced by use of three semi-empirical methods, AM1, PM3 and MNDO, and MNDO electrostatic-potential-derived atomic charges, have been compared in correlations with solvatochromic hydrogen-bonding acidity (,,2H). Atomic charges and LUMO energies, particularly those calculated by use of the AM1 and MNDO methods, were found to correlate well with ,,2H. They were also found to be good models of hydrogen-bonding in QSAR correlations. [source]


    Conjugation of two functional groups through an unsaturated system

    JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 1 2006
    Otto Exner
    Abstract Energies of 51 1-(E),4-(E)-disubstituted 1,3-butadienes (1), 36 1,4-disubstituted benzenes (2) and 36 (E)-1,2-disubstituted ethenes (3) with dipolar substituents were calculated at the B3LYP/6,311,+,G(d,p) level and evaluated in terms of isodesmic reactions expressing the interaction of substituents through the conjugated system. The energy of interaction reaches up to 40,kJ,mol,1, it is roughly similar in the three series and most regular in the series 1. While its correlation within the framework of dual substituent parameter analysis lacks physical meaning, it is possible to separate the conjugative (resonance) component by subtracting the inductive component with reference to 1,4-disubstituted bicyclo[2.2.2]octanes 4. The conjugative interaction is strongly stabilizing for the combination acceptor,donor and destabilizing for two donors; in these cases it is parallel to changes of geometry as they are predicted by the common resonance equations. Interaction of two acceptors is weak; in addition, there are groups that cannot be classified either as donors or as acceptors. Therefore, one can construct a scale of the resonance ability of donors in conjugation with an acceptor and vice versa, but it is not possible to express the interaction of two donors or of two acceptors on a unified scale for all substituents. The resonance description is certainly appropriate for the typical examples (interaction of NO2 and NH2) but should not be generalized to all possible structures. Copyright 2005 John Wiley & Sons, Ltd. [source]


    Nonstoichiometry in A2B2O7 Pyrochlores

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 11 2002
    Christopher R. Stanek
    Energies associated with deviations from stoichiometry for an extensive series of A2B2O7 pyrochlores have been predicted. A3+ cations range in size from Lu to La and B4+ cations from Ti to Pb. Results are presented in the form of contour maps as a means of conveying large quantities of data as well as predicting characteristics for pyrochlore compounds not explicitly modeled. These contour maps indicate that the BO2 excess nonstoichiometry in the pyrochlore structure is distinct from solid-solution fluorite. Within the limitations of this methodology, the contour maps provide a means to understand and predict distinct compositional variations. Defect cluster formation is discussed. [source]


    Upper electron-excited states in bioluminescence: experimental indication

    LUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 3 2001
    N. S. Kudryasheva
    Abstract The involvement of upper electron-excited states in bacterial bioluminescence process was studied with excitation energy-accepting molecules. The fluorescent aromatic compounds, anthracene and 1.4-bis(5-phenyloxazol-2-yl)benzene, were chosen. Energies of their lowest excited singlet states are higher than the energy of the analogous state of the bioluminescence emitter; their absorption spectra and bioluminescence do not overlap. Hence, the excitation of these molecules by singlet,singlet energy transfer or by light absorption is excluded. Sensitized fluorescence of these compounds in the bioluminescence systems has been recorded, indicating the activity of upper electron-excited states in the bioluminescent process. Copyright 2001 John Wiley & Sons, Ltd. [source]


    Topological Electronegativity Index and Its Application , I. Ionization Potentials of Alkyl Groups and Alkyl Halides

    MOLECULAR INFORMATICS, Issue 9 2007
    Chenzhong Cao
    Abstract A Topological Electronegativity Index (TEI) for alkyl group was developed, based on the bond adjacency matrix of the radical atom. Taking the radical atom and the adjacency atoms (or groups) as the vertices of molecular graph of the alkyl group, the bond adjacency matrix was constructed, in which the diagonal elements were assigned the Pauling electronegativity of the atom (or group), and the off-diagonal elements were assigned values 1 or 0. The off-diagonal elements represent the bond connections: that is when the two atoms (or groups) connect with each other, it is 1; otherwise is 0. From the matrix, the eigenvalues were obtained and its geometric mean value was considered as the TEI of an alkyl. The calculated TEI has good correlation with its experimental ionization potential. Further, the TEI was applied to correlate with the ionization potentials of alkyl halides and substituted ethenes, and to correlate with the Bond Dissociation Energies (BDEs) of the CiH bonds in alkanes. [source]


    Strain Energies as a Steric Descriptor in QSAR Calculations

    MOLECULAR INFORMATICS, Issue 7 2004
    Catherine
    Abstract The difference between the calculated heats of formation of gauche and anti conformers of monosubstituted propanes was determined and used as a new steric parameter (AG60 value) in QSAR calculations. The dihedral angle of the gauche conformation was fixed at 60 during the calculation to force interaction of the gauche groups. AG60 values are a thermodynamically determined steric measure in contrast to the Taft steric parameter, which is based upon kinetic measurements of ester hydrolyses. In comparisons to published QSAR studies, AG60 values correlated steric effects and biological activities very similarly to the Taft parameter. The average of r2 values from five QSAR studies for the Taft parameter was 0.887, while AG60 values averaged 0.883. Direct comparison of the Taft parameter and AG60 values showed a poor correlation (r2=0.300), indicating the two parameters are fundamentally different methods of measuring steric bulk. [source]


    Fully relativistic analysis of the absorption spectra of Ca3Sc2Ge3O12:Ni2+

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 12 2006
    M. G. Brik
    Abstract Systematic analysis of the energy level schemes, ground state absorption (GSA) and covalency effects for the Ni2+ ion in Ca3Sc2Ge3O12 was performed. The recently developed first-principles approach to the analysis of the absorption spectra of impurity ions in crystals based on the discrete variational multi-electron method (DV-ME) [K. Ogasawara et al., Phys. Rev. B 64, 115413 (2001)] was used in the calculations. As a result, complete energy level schemes of Ni2+ and its absorption spectra at both possible crystallographic positions (distorted octahedral Sc3+ and tetrahedral Ge4+ positions) were calculated, assigned and compared with experimental data. Energies of the charge transfer (CT) transitions for both positions are estimated. Numerical contributions of all possible electron configurations into the calculated energy states were determined. By performing analysis of the molecular orbitals (MO) population, it was shown that the covalency of the chemical bonds between the Ni2+ and O2, ions increases in passing from the hexa- to the tetra-coordinated complex. ( 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]


    Scientific Highlights from the ,k Network: Towards Atomistic Materials Design

    PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 11 2006
    P. H. Dederichs
    The ,k network aims at encompassing the whole community of European groups working in the area of ab - initio materials modelling, including very many small groups and isolated researchers. Historically, the activities started in the 1980s in Trieste with the workshop series entitled "Total Energies and Forces". Since then, it has operated on the European level in various forms, with funding from various EC/EU and ESF sources, beginning more than 10 years ago with the EC's Human Capital and Mobility Programme. In that time, ,k has done much to make Europe the leading area in the world for research in atomic-scale ab - initio computer simulation of all types of materials, their structures, properties, and processes. To a large extent, this has been done by nurturing scientific excellence and collaboration in what might be called "the ,k family". The ,k Network is presently organized around 15 topical working groups. Over the years, the ,k network organized three large scale conferences in Schwbisch Gmnd, Germany (1996, 2000, 2005), attended by hundreds of scientists from all over the world. The next ,k Conference is to be organized in Berlin in 2010. These ,k Conferences are unique events fully dedicated to the ab - initio research. In addition, the network organizes a variety of meetings and topical workshops every year. The core activities of the ,k network involve editing every two months a ,k newsletter with typically more than 100 pages, which contains a "Scientific Highlight", announcements of conferences, workshops and vacant positions, news of various ESF and EU funded networks, including reports on workshops, and abstracts of submitted papers. The ,k has its own web pages (http://psi-k.dl.ac.uk) which inform about the Network, its structure, and how to get involved in ,k activities. These web pages are also the repository of the ,k newsletters and Scientific Highlights and details about the ,k Workshops of the most recent years. The ,k mailing list contains about 1700 e-mail addresses from across the world, and all the important information about a variety of activities of the network is distributed across this list on a daily basis. The "Scientific Highlights" of the ,k newsletters reflect the scientific activities of the network and aim at presenting reviews and current developments in the field. This special issue of physica status solidi (b) gives a collection of some of the most recent Highlight contributions to the ,k newsletter. All manuscripts originally posted on the ,k server were peer-reviewed by two referees and accepted according to the standards of pss. They are published here partly in revised or updated version. We hope that the readership of the journal will benefit from the quality of the research they report on and the high level of the presentations. [source]


    Distance dependence and salt sensitivity of pairwise, coulombic interactions in a protein

    PROTEIN SCIENCE, Issue 5 2002
    Kelly K. Lee
    Abstract Histidine pKa values were measured in charge-reversal (K78E, K97E, K127E, and K97E/K127E) and charge-neutralization (E10A, E101A, and R35A) mutants of staphylococcal nuclease (SNase) by 1H-NMR spectroscopy. Energies of interaction between pairs of charges (,Gij) were obtained from the shifts in pKa values relative to wild-type values. The data describe the distance dependence and salt sensitivity of pairwise coulombic interactions. Calculations with a continuum electrostatics method captured the experimental ,Gij when static structures were used and when the protein interior was treated empirically with a dielectric constant of 20. The ,Gij when rij , 10 were exaggerated slightly in the calculations. Coulomb's law with a dielectric constant near 80 and a Debye-Hckel term to account for screening by the ionic strength reproduced the salt sensitivity and distance dependence of ,Gij as well as the structure-based method. In their interactions with each other, surface charges behave as if immersed in water; the Debye length describes realistically the distance where interactions become negligible at a given ionic strength. On average, charges separated by distances (rij) ,5 interacted with ,Gij , 0.6 kcal/mole in 0.01 M KCl, but ,Gij decayed to ,0.10 kcal/mole when rij = 20 . In 0.10 M KCl, ,Gij , 0.10 kcal/mole when rij = 10 . In 1.5 M KCl, only short-range interactions with rij , 5 persisted. Although at physiological ionic strengths the interactions between charges separated by more than 10 are extremely weak, in situations where charge imbalance exists many weak interactions can cumulatively produce substantial effects. [source]


    ChemInform Abstract: Sulfur Dioxide and Water: Structures and Energies of the Hydrated Species SO2nH2O, [HSO3] - nH2O, [SO3H] - nH2O, and H2SO3nH2O (n = 0,8)

    CHEMINFORM, Issue 25 2009
    Ralf Steudel
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


    ChemInform Abstract: Predicted Energies and Structures Associated with the Mixed Calcium Strontium Fluorapatites

    CHEMINFORM, Issue 11 2009
    Emily M. Michie
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


    ChemInform Abstract: Benchmark Calculations on the Electron Detachment Energies of MO3 - and M2O6 - (M: Cr, Mo, W)

    CHEMINFORM, Issue 8 2008
    Shenggang Li
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


    Simultaneous Determination of Gibbs Free Energies of Formation of Sr2RhO4(s) and Sr4RhO6(s) Using Solid-State Electrochemical Cells.

    CHEMINFORM, Issue 1 2005
    Aparna Banerjee
    No abstract is available for this article. [source]


    Lattice Energies of Apatites and the Estimation of ,Hf(PO43- , g).

    CHEMINFORM, Issue 22 2004
    Natalie J. Flora
    No abstract is available for this article. [source]


    Ab initio Calculations for the 2s and 2p Core Level Binding Energies of Atomic Zn, Zn Metal, and Zn Containing Molecules.

    CHEMINFORM, Issue 45 2003
    Norbert Roessler
    No abstract is available for this article. [source]


    Al3O4 and Al3O4 - Clusters: Structure, Bonding, and Electron Binding Energies

    CHEMINFORM, Issue 26 2003
    Ana Martinez
    Abstract For Abstract see ChemInform Abstract in Full Text. [source]


    ChemInform Abstract: Gas-Phase Vanadium Oxide Anions: Structure and Detachment Energies from Density Functional Calculations.

    CHEMINFORM, Issue 7 2001
    Sergei F. Vyboishchikov
    Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]


    Progress in the Understanding of Drug,Receptor Interactions, Part,2: Experimental and Theoretical Electrostatic Moments and Interaction Energies of an Angiotensin II Receptor Antagonist (C30H30N6O3S)

    CHEMISTRY - A EUROPEAN JOURNAL, Issue 24 2007
    Raffaella Soave Dr.
    Abstract A combined experimental and theoretical charge density study of an angiotensin II receptor antagonist (1) is presented focusing on electrostatic properties such as atomic charges, molecular electric moments up to the fourth rank and energies of the intermolecular interactions, to gain an insight into the physical nature of the drug,receptor interaction. Electrostatic properties were derived from both the experimental electron density (multipole refinement of X-ray data collected at T=17,K) and the ab initio wavefunction (single molecule and fully periodic calculations at the DFT level). The relevance of S,,,O and S,,,N intramolecular interactions on the activity of 1 is highlighted by using both the crystal and gas-phase geometries and their electrostatic nature is documented by means of QTAIM atomic charges. The derived electrostatic properties are consistent with a nearly spherical electron density distribution, characterised by an intermingling of electropositive and -negative zones rather than by a unique electrophilic region opposed to a nucleophilic area. This makes the first molecular moment scarcely significant and ill-determined, whereas the second moment is large, significant and highly reliable. A comparison between experimental and theoretical components of the third electric moment shows a few discrepancies, whereas the agreement for the fourth electric moment is excellent. The most favourable intermolecular bond is show to be an NH,,,N hydrogen bond with an energy of about 50,kJ,mol,1. Key pharmacophoric features responsible for attractive electrostatic interactions include CH,,,X hydrogen bonds. It is shown that methyl and methylene groups, known to be essential for the biological activity of the drug, provide a significant energetic contribution to the total binding energy. Dispersive interactions are important at the thiophene and at both the phenyl fragments. The experimental estimates of the electrostatic contribution to the intermolecular interaction energies of six molecular pairs, obtained by a new model proposed by Spackman, predict the correct relative electrostatic energies with no exceptions. [source]