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Proceedings of the National Academy of... Apr 2007Metal-alkane binding energies have been calculated for [CpRe(CO)2](alkane) and [(CO)2M(C5H4)C[triple bond]C(C5H4)M(CO)2](alkane), where M = Re or Mn. Calculated binding...
Metal-alkane binding energies have been calculated for [CpRe(CO)2](alkane) and [(CO)2M(C5H4)C[triple bond]C(C5H4)M(CO)2](alkane), where M = Re or Mn. Calculated binding energies were found to increase with the number of metal-alkane interaction sites. In all cases examined, the manganese-alkane binding energies were predicted to be significantly lower than those for the analogous rhenium-alkane complexes. The metal (Mn or Re)-alkane interaction was predicted to be primarily one of charge transfer, both from the alkane to the metal complex (70-80% of total charge transfer) and from the metal complex to the alkane (20-30% of the total charge transfer).
Topics: Alkanes; Models, Chemical; Oxidation-Reduction; Rhenium; Thermodynamics; Transition Elements
PubMed: 17442751
DOI: 10.1073/pnas.0610295104 -
The Journal of Biological Chemistry Feb 1998An n-alkane-assimilating yeast Candida maltosa contains multiple n-alkane-inducible forms of cytochromes P450 (P450alk), which can be assumed to catalyze terminal...
An n-alkane-assimilating yeast Candida maltosa contains multiple n-alkane-inducible forms of cytochromes P450 (P450alk), which can be assumed to catalyze terminal hydroxylation of n-alkanes in the assimilation pathway. Eight structurally related P450alk genes have been identified. In the present study, the function of four major isoforms of P450alk (encoded by ALK1, ALK2, ALK3, and ALK5 genes) was investigated by sequential gene disruption. Auxotrophic markers used for the selection of disrupted strains were regenerated repeatedly through either mitotic recombination between heterozygous alleles of the diploid genome or directed deletion of the marker gene, to allow sequential gene disruptions within a single strain. The strain depleted of all four isoforms could not utilize n-alkanes for growth, providing direct evidence that P450alk is essential for n-alkane assimilation. Growth properties of a series of intermediate disrupted strains, plasmid-based complementation, and enzyme assays after heterologous expression of single isoforms revealed (i) that each of the four individual isoforms is alone sufficient to allow growth on long chain n-alkane; (ii) that the ALK1-encoding isoform is the most versatile and efficient P450alk form, considering both its enzymatic activity and its ability to confer growth on n-alkanes of different chain length; and (iii) that the ALK5-encoding isoform exhibits a rather narrow substrate specificity and thus cannot support the utilization of short chain n-alkanes.
Topics: Alkanes; Animals; Candida; Cytochrome P-450 Enzyme System; Enzyme Induction; Fungal Proteins; Gene Deletion; Genes, Fungal; Genetic Complementation Test; Genetic Markers; Hydroxylation; Isoenzymes; Rats; Substrate Specificity
PubMed: 9461581
DOI: 10.1074/jbc.273.7.3948 -
Journal of the American Chemical Society Jul 2006Density functional theory is used to explore the mechanisms of alkane hydroxylation for four synthetic non-heme iron(IV)-oxo complexes with three target substrates...
Density functional theory is used to explore the mechanisms of alkane hydroxylation for four synthetic non-heme iron(IV)-oxo complexes with three target substrates (Kaizer, J.; Klinker, E. J.; Oh, N. Y.; Rohde; J.-U.; Song, W. J.; Stubna, A.; Kim, J.; Münck, E.; Nam, W.; Que, L., Jr. J. Am. Chem. Soc. 2004, 126, 472-473; Rohde, J.-U.; Que, L., Jr. Angew. Chem. Int. Ed. 2005, 44, 2255-2258.). The iron-oxo reagents possess triplet ground states and low-lying quintet excited states. The set of experimental and theoretical reactivity trends can be understood if the reactions proceed on the two spin states, namely two-state reactivity (TSR); an appropriate new model is presented. The TSR model makes testable predictions: (a) If crossing to the quintet state occurs, the hydroxylation will be effectively concerted; however, if the process transpires only on the triplet surface, stepwise hydroxylation will occur, and side products derived from radical intermediates would be observed (e.g., loss of stereochemistry). (b) In cases of crossing en route to the quintet transition state, one expects kinetic isotope effects (KIEs) typical of tunneling. (c) In situations where the two surfaces contribute to the rate, one expects intermediate KIEs and radical scrambling patterns that reflect the two processes. (d) Solvent effects on these reactions are expected to be very large.
Topics: Alkanes; Computer Simulation; Ferric Compounds; Hydroxylation; Iron; Ligands; Models, Chemical; Molecular Structure; Oxygen; Quantum Theory
PubMed: 16802826
DOI: 10.1021/ja061609o -
Langmuir : the ACS Journal of Surfaces... Nov 2013The adsorption of members of the homologous series of alkyl trimethylammonium bromides (C(n)TAB) is studied at water/alkane interfaces by drop profile analysis...
The adsorption of members of the homologous series of alkyl trimethylammonium bromides (C(n)TAB) is studied at water/alkane interfaces by drop profile analysis tensiometry. The results are discussed in terms of a competitive adsorption process of alkane and surfactant molecules. A thermodynamic model, derived originally for the adsorption of surfactant mixtures, is adapted such that it describes a competitive adsorption of the surfactant molecules from the aqueous phase and alkane molecules from the oil phase. This new model involves the interspecies attraction coefficient, which mutually increases the adsorption activities of the alkane and C(n)TAB. The effects of the alkyl chain length n of C(n)TABs and the influence of the number of C atoms in the alkane chain are discussed, and the physical quantities are compared to those determined at the aqueous solution/air interface. The new theoretical model for aqueous solution/oil interfaces is also compared to a theory that does not consider the adsorption of alkane. The proposed new model demonstrates good agreement with the experimental data.
Topics: Adsorption; Alkanes; Quaternary Ammonium Compounds; Surface-Active Agents; Volatilization; Water
PubMed: 24111851
DOI: 10.1021/la402782e -
Natural Product Research Oct 2017Two new compounds a flavanolignan (1), and an alkane (2) along with four known compounds including two fatty acid esters (3-4) and two isocoumarins (5-6) were isolated...
Two new compounds a flavanolignan (1), and an alkane (2) along with four known compounds including two fatty acid esters (3-4) and two isocoumarins (5-6) were isolated from the methanolic extract of the stem bark of Newtonia griffoniana. Their structures were elucidated using spectroscopic methods including extensive 1-D and 2-D NMR experiments.
Topics: Alkanes; Fabaceae; Fatty Acids; Flavonolignans; Isocoumarins; Magnetic Resonance Spectroscopy; Molecular Structure; Plant Bark; Plant Extracts
PubMed: 28287276
DOI: 10.1080/14786419.2017.1299725 -
Natural Product Research 2014The present communication is a first-time report on the analyses of n-alkane profile of epicuticular wax extracted from the mature leaves of Nyctanthes arbor-tristis L....
The present communication is a first-time report on the analyses of n-alkane profile of epicuticular wax extracted from the mature leaves of Nyctanthes arbor-tristis L. during a calender year. The composition of n-alkanes revealed hentriacontane (n-C31), tritriacontane (n-C33), tetratriacontane (n-C35) and nonacosane (n-C29) as the major constituents with tritriacontane (n-C33) being the dominant constituent. The cumulative percentage of these four odd-numbered alkanes also showed phenological variation being highest during the fruit ripening stage (average value 63.29%) followed by the flowering stage (mean value 60.74%). The values remained moderate on an average of 54.31% for the rest of the year. This study also confirms the xerophytic feature of the plant having higher proportion of longer carbon chain n-alkanes greater than C31 (dominant peaks are of C33 and C35).
Topics: Alkanes; Carbon; Chromatography, Gas; Hydrocarbons; India; Oleaceae; Plant Leaves; Waxes
PubMed: 24144021
DOI: 10.1080/14786419.2013.850689 -
Journal of Medicinal Chemistry Jul 2008Partition coefficients were measured for 47 compounds in the hexadecane/water ( P hxd) and 1-octanol/water ( P oct) systems. Some types of hydrogen bond acceptor...
Partition coefficients were measured for 47 compounds in the hexadecane/water ( P hxd) and 1-octanol/water ( P oct) systems. Some types of hydrogen bond acceptor presented by these compounds to the partitioning systems are not well represented in the literature of alkane/water partitioning. The difference, DeltalogP, between logP oct and logP hxd is a measure of the hydrogen bonding potential of a molecule and is identified as a target for predictive modeling. Minimized molecular electrostatic potential ( V min) was shown to be an effective predictor of the contribution of hydrogen bond acceptors to DeltalogP. Carbonyl oxygen atoms were found to be stronger hydrogen bond acceptors for their electrostatic potential than heteroaromatic nitrogen or oxygen bound to hypervalent sulfur or nitrogen. Values of V min calculated for hydrogen-bonded complexes were used to explore polarization effects. Predicted logP hxd and DeltalogP were shown to be more effective than logP oct for modeling brain penetration for a data set of 18 compounds.
Topics: Alkanes; Central Nervous System; Molecular Structure; Static Electricity; Surface Properties; Water
PubMed: 18558667
DOI: 10.1021/jm701549s -
The Journal of Physical Chemistry. B Nov 2015The flash point is one of the most important characteristics used to assess the ignition hazard of mixtures of flammable liquids. To determine the flash points of...
The flash point is one of the most important characteristics used to assess the ignition hazard of mixtures of flammable liquids. To determine the flash points of mixtures of secondary alcohols with n-alkanes, it is necessary to calculate the activity coefficients. In this paper, we use a model that allows us to obtain enthalpy of fusion and enthalpy of vaporization data of the pure components to calculate the liquid-solid equilibrium (LSE) and vapor-liquid equilibrium (VLE). Enthalpy of fusion and enthalpy of vaporization data of secondary alcohols in the literature are limited; thus, the prediction of these characteristics was performed using the method of thermodynamic similarity. Additionally, the empirical models provided the critical temperatures and boiling temperatures of the secondary alcohols. The modeled melting enthalpy and enthalpy of vaporization as well as the calculated LSE and VLE flash points were determined for the secondary alcohol and n-alkane mixtures.
Topics: Alcohols; Alkanes; Models, Chemical; Thermodynamics
PubMed: 26491811
DOI: 10.1021/acs.jpcb.5b04872 -
The Journal of Physical Chemistry. B Dec 2008The liquid-liquid interface between semifluorinated alkane diblock copolymers of the form F3C(CF2)n-1-(CH2)m-1CH3 and water, protonated alkanes, and perfluorinated...
The liquid-liquid interface between semifluorinated alkane diblock copolymers of the form F3C(CF2)n-1-(CH2)m-1CH3 and water, protonated alkanes, and perfluorinated alkanes are studied by fully atomistic molecular dynamics simulations. A modified version of the OPLS-AA (Optimized Parameter for Liquid Simulation All-Atom) force field of Jorgensen et al. has been used to study the interfacial behavior of semifluorinated diblocks. Aqueous interfaces are found to be sharp, with correspondingly large values of the interfacial tension. Due to the reduced hydrophobicity of the protonated block compared to the fluorinated block, hydrogen enhancement is observed at the interface. Water dipoles in the interfacial region are found to be oriented nearly parallel to the liquid-liquid interface. A number of protonated alkanes and perfluorinated alkanes are found to be mutually miscible with the semifluorinated diblocks. For these liquids, interdiffusion follows the expected Fickian behavior, and concentration-dependent diffusivities are determined.
Topics: Alkanes; Computer Simulation; Fluorine Compounds; Models, Molecular; Polymers; Protons; Time Factors; Water
PubMed: 19367794
DOI: 10.1021/jp805574f -
Journal of the American Chemical Society Aug 2008In this computational work we explore metal-organic frameworks (MOFs) for separating alkanes according to the degree of branching. We show that the structure MOF-1 shows...
In this computational work we explore metal-organic frameworks (MOFs) for separating alkanes according to the degree of branching. We show that the structure MOF-1 shows an adsorption hierarchy for a 13-component light naphtha mixture precisely as desired for increasing the research octane number of gasoline. In addition we report an unusual molecular-level segregation of molecules based on their degree of branching.
Topics: Adsorption; Alkanes; Molecular Structure; Nanostructures; Porosity; Silicates; Surface Properties; Zeolites
PubMed: 18651737
DOI: 10.1021/ja804039c