Diffusion of Dioxygen in <i>n</i>-Alkanes

Kowert, Bruce A.; Dang, Nhan C.

doi:10.1021/jp984025k

Cited by 44 publications

(62 citation statements)

References 23 publications

(34 reference statements)

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“…These small molecules do not follow Stokes-Einstein law, meaning that their diffusion is not inversely related to the viscosity of the solvent (44). This property was previously evidenced for O 2 diffusion in water and n-alkanes (45,46) as well as for small non-electrolyte diffusion through lipid membranes (47). For instance, the viscosity at the core of LDL is expected to be higher than at the interior of membranes, and hence more than 100-times greater than water (0.89 versus 60 -100 mPas for water (30) and membranes (48 -50), respectively).…”

Section: Discussionmentioning

confidence: 84%

Direct Measurement of Nitric Oxide and Oxygen Partitioning into Liposomes and Low Density Lipoprotein

Möller

Botti

Batthyány

et al. 2005

Journal of Biological Chemistry

133

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Nitric oxide ( ⅐ NO) has been proposed to play a relevant role in modulating oxidative reactions in lipophilic media like biomembranes and lipoproteins. Two factors that will regulate ⅐ NO reactivity in the lipid milieu are its diffusion and solubility, but there is no data concerning the actual diffusion (D) and partition coefficients (K P ) of ⅐ NO in biologically relevant hydrophobic phases. Herein, a "equilibrium-shift" method was designed to directly determine the ⅐ NO and O 2 partition coefficients in liposomes and low density lipoprotein (LDL) relative to water. It was found that ⅐ NO partitions 4.4-and 3.4-fold in liposomes and LDL, respectively, whereas O 2 behaves similarly with values of 3.9 and 2.9, respectively. In addition, actual diffusion coefficients in these hydrophobic phases were determined using fluorescence quenching and found that ⅐ NO diffuses ϳ2 times slower ). The influence of ⅐ NO and O 2 partitioning and diffusion in membranes and lipoproteins on ⅐ NO reaction with lipid radicals and auto-oxidation is discussed. Particularly, the 3-4-fold increase in O 2 and ⅐ NO concentration within biological hydrophobic phases provides quantitative support for the idea of an accelerated auto-oxidation of ⅐ NO in lipid-containing structures, turning them into sites of enhanced local production of oxidant and nitrosating species.Nitric oxide produced by the oxidation of L-arginine to Lcitrulline by ⅐ NO 1 synthases accomplishes important physiological regulatory functions related to vasodilation, neurotransmission, immune response, and regulation of cell respiration (1, 2). Despite being a free radical, ⅐ NO is a weak redox intermediate, and its reactivity is restricted to paramagnetic species, including metals, metalloproteins (3, 4), and other radical molecules (5, 6).The reactions of ⅐ NO with other radicals can be classified as oxidant or antioxidant, depending on the reactivity of the products. Nitric oxide reacts with the superoxide anion radical (O 2 . ) at diffusion-controlled rates to yield peroxynitrite, a strong oxidant that can induce lipid and protein oxidation and nitration (6, 7). Similarly, the reaction with O 2 yields nitrogen dioxide ( ⅐ NO 2 ) and dinitrogen trioxide (N 2 O 3 ), strong oxidant and nitrosating species (8, 9). Although the reaction with O 2 is complex and not completely understood (8, 9), the rate law is second-order in ⅐ NO and first-order in O 2 , with a third-order rate constant k ϭ 0.8 -1.2 ϫ 10 7 M Ϫ2 s Ϫ1 (8, 9). On the other hand, ⅐ NO has been proposed as an important antioxidant in vivo (10 -12), mainly because it reacts with organic peroxyl radicals at near diffusion-limited rates (k ϭ 1-3 ϫ 10 9 M Ϫ1 s Ϫ1 , see Refs. 5 and 13) effectively inhibiting lipid peroxidation chain reactions (7, 10 -12, 14 -17). This antioxidant activity may be specially relevant in low density lipoprotein (LDL), because oxidatively modified lipoproteins can be recognized by scavenger receptors on macrophages and lead to macrophage lipid loading and eventually to atherosclerosis...

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Section: Discussionmentioning

confidence: 84%

Direct Measurement of Nitric Oxide and Oxygen Partitioning into Liposomes and Low Density Lipoprotein

Möller

Botti

Batthyány

et al. 2005

Journal of Biological Chemistry

133

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“…Except for macromolecules, however, numerous experimental studies 3,[57][58][59][60][61][62][63][64][65][66] have shown that tracer diffusivity is inversely proportional to a fractional power of the viscosity of the solvent instead. This fractional power dependence of viscosity on diffusion is often referred to in the literature as the fractional Stokes-Einstein (FSE) relation, (D 12 /T) ∝ η −t , where t is known to be normally less than unity and generally around 2/3.…”

Section: B Solvent Dependencementioning

confidence: 99%

Diffusion of aromatic compounds in nonaqueous solvents: A study of solute, solvent, and temperature dependences

Chan

Tang

2013

The Journal of Chemical Physics

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Tracer diffusivities (limiting mutual diffusion coefficients) of nonassociated aromatic compounds in n-hexane and cyclohexane have been measured at 298.2 K by Taylor's dispersion method. These new data, together with other diffusivities of nonassociated pseudoplanar solutes reported in the literature, are used to determine the separate effects of solute and solvent on tracer diffusion. The data show that for a given pseudoplanar solute diffusing in different solvents at 298.2 K, the tracer diffusivity is dependent not only on the fractional viscosity of the solvent but also on a function of the solvent's molar density, molecular mass, and free volume fraction. For different pseudoplanar aromatic solutes diffusing in a particular solvent at a constant temperature, there is a linear relationship between the reciprocal of the tracer diffusivity and the molecular volume of the solutes. The results are discussed in respect to relevant theories and experimental studies in the literature. An idealized relation, developed on the basis of the Einstein equation by incorporating the newly found solute and solvent dependences, is capable of describing a total of 176 diffusivities of nonassociated pseudoplanar solutes in various solvents at different temperatures to within an average error of ±2.8%. © 2013 AIP Publishing LLC. [http://dx

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“…As the chain length (and viscosity) of the n-alkanes increased, the value of r for O 2 from eq 1 became smaller, 4 i.e., the diffusion of O 2 became progressively faster than predicted by a constant molecular "size." A possible explanation is that the n-alkanes, which on average are relatively extended, provide regions of increasing length in which the interactions between O 2 and the hydrocarbon are relatively weak and through which diffusion is relatively rapid.…”

Section: Introductionmentioning

confidence: 97%

Diffusion of Dioxygen in Alkanes and Cycloalkanes

et al. 2000

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The translational diffusion constant, D, of dioxygen, O 2 , has been measured in the odd n-alkanes n-C 7 H 16 to n-C 15 H 32 , two branched alkanes (isooctane and squalane), and several cycloalkanes (cyclohexane, methylcyclohexane, n-butylcyclohexane, dicyclohexyl, cis-decalin, and trans-decalin). The D values were determined using Taylor-Aris dispersion theory in solutions drawn through a microcapillary by reduced pressure. The initial analysis of the data was in terms of the Stokes-Einstein relation (D ) k B T/6πηr). In both the n-alkanes and cycloalkanes, the values of the hydrodynamic radius r for O 2 are smaller than its known dimensions and decrease as the viscosity η increases, i.e., O 2 is diffusing faster than predicted by a constant solute "size." The data can be fitted to D/T ) A/η p with p < 1 (p ) 1 for the Stokes-Einstein relation). When the data for the odd n-alkanes are combined with our earlier results for O 2 in the even n-alkanes (n-C 6 H 14 to n-C 16 H 34 , Kowert, B. A.; Dang, N. C. J. Phys. Chem. 1999, 103, 779), we find p ) 0.553 ( 0.009. For O 2 in the cycloalkanes the fit gives p ) 0.632 ( 0.017. The data for isooctane and squalane are in approximate agreement with the n-alkane fit. The D values are also discussed in terms of computer simulations for small penetrants in hydrocarbons, the molar volumes of the solvents, and free volume approaches. A correlation between the p values and results of the free volume analyses is noted and discussed.

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Diffusion of Dioxygen in n-Alkanes

Cited by 44 publications

References 23 publications

Direct Measurement of Nitric Oxide and Oxygen Partitioning into Liposomes and Low Density Lipoprotein

Direct Measurement of Nitric Oxide and Oxygen Partitioning into Liposomes and Low Density Lipoprotein

Diffusion of aromatic compounds in nonaqueous solvents: A study of solute, solvent, and temperature dependences

Diffusion of Dioxygen in Alkanes and Cycloalkanes

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