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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Flux in non-aqueous-phase liquid (NAPL)-contaminated systems containing active microbial populations (including Dehalococcoides sp.) was investigated using a quantitative mass balance and phase distribution approach. Batch systems containing mixed NAPL with an initial tetrachloroethene (PCE) mole fraction ranging from 0.1 to 0.4 provided a means for comparing systems where mass transfer and aqueous concentration were controlled by the initial NAPL composition. Although the use of mixed NAPL with increasing PCE mole fractions introduced a mass-transfer variable on the abiotic dissolution rate, it was determined that biological systems produced flux rates that were similar to each other regardless of the initial PCE mole fraction. Thus, organisms appeared to be dechlorinating near their maximum conversion rates, and the result was the accumulation of cis-1,2-dichloroethene (cDCE) followed by slow conversion to vinyl chloride (VC). Increases in the initial PCE mole fractions in the NAPL had a negative impact on product distribution due to the presence of a larger concentration of a more favorable electron acceptor. Because the mass converted to cDCE was present largely in the dissolved phase in all systems, the production of this metabolite was a favorable outcome in terms of NAPL dissolution. The pH dropped as low as 4.9 in active systems, indicating that the amount of HCl released during the reductive dechlorination process was large enough to overwhelm the buffering capacity. This pH effect was more pronounced in systems that exhibited extensive dechlorination to VC, further suggesting that rapid dechlorination of PCE NAPL can alter chemical characteristics in source zone regions.
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PMID:Flux and product distribution during biological treatment of tetrachloroethene dense non-aqueous-phase liquid. 1511 2

We have examined the folding and unfolding of the caspase recruitment domain of procaspase-1 (CP1-CARD), a member of the alpha-helical Greek key protein family. The equilibrium folding/unfolding of CP1-CARD is described by a two-state mechanism, and the results show CP1-CARD is marginally stable with a DeltaG(H2O) of 1.1 +/- 0.2 kcal/mole and an m-value of 0.65 +/- 0.06 kcal/mole/M (10 mM Tris-HCl at pH 8.0, 1 mM DTT, 25 degrees C). Consistent with the equilibrium folding data, CP1-CARD is a monomer in solution when examined by size exclusion chromatography. Single-mixing stopped-flow refolding and unfolding studies show that CP1-CARD folds and unfolds rapidly, with no detectable slow phases, and the reactions appear to reach equilibrium within 10 msec. However, double jump kinetic experiments demonstrate the presence of an unfolded-like intermediate during unfolding. The intermediate converts to the fully unfolded conformation with a half-time of 10 sec. Interrupted refolding studies demonstrate the presence of one or more nativelike intermediates during refolding, which convert to the native conformation with a half-time of about 60 sec. Overall, the data show that both unfolding and refolding processes are slow, and the pathways contain kinetically trapped species.
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PMID:Kinetic traps in the folding/unfolding of procaspase-1 CARD domain. 1527 13

The chemical kinetic description of time evolution where the phase is random but the states are discrete is discussed as a basis for a computational approach. This proposed scheme uses numbers in the entire range of 0 to 1 to represent Boolean propositions. In the implementation by chemical kinetics these numbers are the mole fractions of different species. Vibrational relaxation in a mixture of HCl and DCI is the physical system that is used to illustrate the approach. Energy exchange in such a mixture corresponds to two strongly coupled two-level systems. A search problem, previously discussed in the quantum computing literature, is solved as an example. The solution requires the same number of function evaluations as in the quantal case. The action of the oracle is described in detail.
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PMID:Quasiclassical computation. 1529 13

Bikunin is a glycosylated protein that aggregates extensively during mammalian cell culture, resulting in loss of activity, loss of native secondary structure, and the formation of nonnative disulfide bonds. We investigated the use of high hydrostatic pressure (1000-3000 bar) for the refolding of bikunin aggregates. The refolding yield obtained with pressure-modulated refolding at 2000 bar was 70 (+/-5%) by reverse-phase chromatography (RP-HPLC), significantly higher than the value of 55 (+/-6%) (RP-HPLC) obtained with traditional guanidine HCl "dilution-refolding." In addition, we determined the thermodynamics of pressure-modulated refolding. The change in volume for the transition of aggregate to monomer DeltaV(refolding) was calculated to be -28 (+/-5) mL/mole. Refolding was accompanied by a loss of hydrophobic exposure, resulting in a positive contribution to the DeltaV(refolding). These findings suggest that the disruption of electro-static interactions or the differences in size of solvent-free cavities between the aggregate and the monomer are the prevailing contributions to the negative DeltaV(refolding).
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PMID:High-pressure refolding of bikunin: efficacy and thermodynamics. 1538 59

In 0.01 mol x L(-1) HCl medium, there is an absorption peak at 350 nm for [AuI4]-. The association particle system of CTMAB-[AuI4]- exhibits violet-red color. It has a new absorption peak at 520 nm. The CTMAB concentration cCTMAB in the range of 0-7.0 x 10(-5) mol x L(-1) is linear to the A(520 nm) value. Its regression equation is A(520 nm) = 0.989 x 10(4) cCTMAB + 0.0138, regression coefficient is 0.9995, and the mole absorption coefficient is 1.059 x 10(4) L x mol(-1) x cm(-1). A new spectrophotometry has been proposed for the determination of cation surfactant. The resonance scattering spectra show that the CTMAB+ and [AuI4]- combine to form (AuI4-CTMAB) association molecule with hydrophobicity by means of attraction forces. The association molecules automatically aggregate to form (AuI4-CTMAB)n association particles. So, the particles exhibit two resonance scattering peaks at 580 and 470 nm, and the system exhibits violet-red.
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PMID:[Absorption spectra study of cation surfactant-[AuI4]- association particle system and its analytical application]. 1582 45

In 0.01 mol x L(-1) HCl medium, red color [PtI6]2- and quinine combine to form association molecule. The molecules aggregate automatically owing to strong hydrophobic and molecular forces. And PtI6-quinine association particles with violet-red color formed. It exhibits three resonance scattering peaks at 310 nm, 400 nm and 610 nm, and a Rayleigh scattering peak at 470 nm. The absorption values all increase in the wavelength range of 350-740 nm, and the fluorescence peak at 450 nm was quenched. Under the conditions chosen, the quinine concentration in the range of 0-40 x 10(-6) mol x L(-1) is linear to the A(620 nm) value. The mole absorption coefficient epsilon(620 nm) is 1.31 x 10(4) L x mol(-1) x cm(-1). The results show that the association particles produce the resonance scattering effect, fluorescence quenching and the violet-red color.
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PMID:[Spectral properties of the association particle system of quinine-[PtI6]2- and its analytical application]. 1582 46

Intact and treated biomass can remove heavy metals from water and wastewater. This study examined the ability of the activated, semi-intact and inactivated Azolla filiculoides (a small water fern) to remove Pb(2+), Cd(2+), Ni(2+) and Zn(2+) from the aqueous solution. The maximum uptake capacities of these metal ions using the activated Azolla filiculoides by NaOH at pH 10.5 +/- 0.2 and then CaCl(2)/MgCl(2)/NaCl with total concentration of 2 M (2:1:1 mole ratio) in the separate batch reactors were obtained about 271, 111, 71 and 60 mg/g (dry Azolla), respectively. The obtained capacities of maximum adsorption for these kinds of the pre-treated Azolla in the fixed-bed reactors (N(o)) were also very close to the values obtained for the batch reactors (Q(max)). On the other hand, it was shown that HCl, CH(3)OH, C(2)H(5)OH, FeCl(2), SrCl(2), BaCl(2) and AlCl(3) in the pre-treatment processes decreased the ability of Azolla to remove the heavy metals in comparison to the semi-intact Azolla, considerably. The kinetic studies showed that the heavy metals uptake by the activated Azolla was done more rapid than those for the semi-intact Azolla.
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PMID:Pre-treatment processes of Azolla filiculoides to remove Pb(II), Cd(II), Ni(II) and Zn(II) from aqueous solution in the batch and fixed-bed reactors. 1611 10

A solvent-extraction system comprising toluene/ter-butanol (ter-BuOH) mixed solvent as the organic phase was developed to selectively extract Cr(VI) from acidic chloride media in the presence of divalent metals, namely Cd(II), Co(II), Cu(II), Ni(II) and Zn(II) under 5 M CaCl2 salting-out conditions. Chromium(VI) was selectively extracted as a solvated ion-pair of [ter-BuOH2+ x CrO3Cl-] at ter-BuOH mole fractions of between 0.1 and 0.6 (9.0-57.2% in volume). Divalent metals were extracted at ter-BuOH mole fraction over 0.6 with extraction percents of Co (< 20%), Cu (< 15%), Ni (< 10%) and Zn (< 20%). The concentrations of Ca2+, water and ter-BuOH in the organic phase and ter-BuOH in the aqueous phase were determined to find out the effects on the extraction of Cr(VI). The chemical species of Cr(VI) in acidic chloride media containing 5 M CaCl2 and 0.1 M HCl was confirmed to be the CrO3Cl- species. The effects of the acid, salt concentrations in the aqueous phase and the solvent composition of a mixed organic solvent on the extraction of Cr(VI) were evaluated. Based on the above studies, the extraction mechanism was elucidated and the optimum extraction conditions were determined.
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PMID:Toluene/ter-butanol mixed solvent for the selective extraction of Cr(VI) from divalent heavy metals. 1636 76

A double-tail amine oxide surfactant, di-n-decylmethylamine oxide (2C10MAO), was prepared, and the effects of protonation on aggregate structure were examined by small-angle neutron scattering (SANS), cryo-transmission electron microscopy (cryo-TEM), turbidity, electric conductivity, and solubilization of an oil-soluble dye at various degrees of neutralization, X, defined as the mole ratio of HCl/2C10MAO. The surfactant makes an L(2) phase in the nonprotonated state (X = 0) in water. The L(2) phase is in equilibrium with an aqueous L(1) phase. On protonation, unilamellar vesicles (ULVs) are formed over a wide range of compositions (0.05 < X< 0.4-0.5 at C = 10 mM) as observed by cryo-TEM. At X = 0.2, the ULV is stable over a wide concentration range (3 mM < or = C < 0.1 M), but an L(alpha) phase replaces the vesicle phase at C > 0.1 M. SANS results show that the mean radius of the ULV is about 25 nm and the bilayer thickness is about 2 nm, consistent with the extended configuration of the alkyl chains of the surfactant. An important contribution to the enhanced stability of the bilayer structures over the L(2) phase is suggested to be the translational entropy of the counterions. The enhanced stability of the bilayers diminishes as the counterion concentration increases either by an increase of X or by the addition of a salt. When the counterion concentration exceeds a critical value, the ULV solutions transform into the L(2) phase (or L(2)/L(1) two-phase system at low surfactant concentrations). The critical composition X is about 0.4-0.5 in water, but it is below 0.4 in D(2)O. The critical NaCl concentration is below 5 mM at X = 0.2. The stability of ULVs against multilamellar vesicles is ascribed partly to undulation forces and partly to the adjustable nature of the spontaneous curvature of amine oxide monolayers. The characteristics of the ULV of the surfactant remain the same within a temperature range 25-50 degrees C at X = 0.2. An iridescent lamellar phase and possibly an L(3) phase were observed in a very narrow X range (0 < X < 0.02) prior to the vesicle phase.
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PMID:Charge-induced unilamellar vesicle formation and phase separation in solutions of Di-n-decylmethylamine oxide. 1670 80

The interaction of hen egg-white lysozyme with sodium n-dodecyl sulfate (SDS) as an anionic surfactant was investigated by UV-vis spectrophotometry at different pHs at 25 degrees C using HCl/glycine and NaOH/glycine for acidic and basic pH ranges, respectively. Analysis of the spectral data using chemometric method gave the evidence for the existence of intermediate components during the cited interaction. Results also indicated a connection between turbidity of the protein solution upon interaction with SDS and distribution of our newly found intermediates. As intermediates are important in aggregation of proteins, beta-cyclodextrin was employed as an anti-aggregation agent and the results obtained for the lysozyme-SDS-beta-cyclodextrin ternary system were compared with those obtained in the absence of beta-cyclodextrin on distribution and mole fraction of intermediates with. It is also shown that as the distribution of intermediates broadens in a range of SDS concentrations, the turbidity and aggregation state of solution are reduced.
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PMID:Chemometric studies of lysozyme upon interaction with sodium dodecyl sulfate and beta-cyclodextrin. 1683 51


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