Health & Environmental Research Online (HERO)


tert-Butanol

2,563 References Were Found:

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Antioxidant and antifungal activities of Smilax campestris Griseb. (Smilacaceae)

Authors: Morais, MI; Pinto, ME; Araújo, SG; Castro, AH; Duarte-Almeida, JM; Rosa, LH; Rosa, CA; Johann, S; Lima, LA (In Press) HERO ID: 2325014

[Less] Ethanol extract and fractions obtained from aerial parts of Smilax campestris were examined in order . . . [More] Ethanol extract and fractions obtained from aerial parts of Smilax campestris were examined in order to determine their phenolic composition, antioxidant capacity and antifungal activities. High-performance liquid chromatography coupled with DAD analysis indicated that quercetin and rutin were the main phenolic compounds present in butanol fraction and ethanol extract, respectively. The antioxidant activity assessed by the scavenging ability on 1,1-diphenyl-2-picrylhydrazyl radical was significantly more pronounced for the ethanol extract and butanol fraction than that of the commercial antioxidant 2,6-di-tert-butyl-4-methylphenol. The antifungal activity of extract and fractions was investigated by using microdilution method against five Candida and two Cryptococcus yeast strains. Ethanol extract and fractions exhibited antifungal activities against Candida albicans, Candida glabrata, Candida krusei, Candida parapsilosis, Candida tropicalis and Cryptococcus gattii. This work provides the knowledge of profile and content of flavonoids and their antioxidant and antifungal activities in the extract and fractions of aerial parts of S. campestris.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Photooxidation of arsenite under 254 nm irradiation with a quantum yield higher than unity

Authors: Ryu, J; Monllor-Satoca, D; Kim, D-H; Yeo, J; Choi, W (In Press) Environmental Science and Technology. HERO ID: 1797795

[Less] Arsenite (As(III)) in water was demonstrated to be efficiently oxidized to arsenate (As(V)) under 254 . . . [More] Arsenite (As(III)) in water was demonstrated to be efficiently oxidized to arsenate (As(V)) under 254 nm UV irradiation without needing any chemical reagents. Although the molar absorption coefficient of As(III) at 254 nm is very low (2.49±0.1 M(-1)cm(-1)), the photooxidation proceeded with a quantum yield over 1.0, which implies a chain of propagating oxidation cycles. The rate of As(III) photooxidation was highly enhanced in the presence of dissolved oxygen, which can be ascribed to its dual role as an electron acceptor of photo-excited As(III) and a precursor of oxidizing radicals. The in-situ production of H2O2 was observed during the photooxidation of As(III) and its subsequent photolysis under UV irradiation produced OH radicals. The addition of tert-butyl alcohol as OH radical scavengers significantly reduced (but not completely inhibited) the oxidation rate, which indicates that OH radicals as well as superoxide serve as an oxidant of As(III). Superoxide, H2O2, and OH radicals were all in situ generated from the irradiated solution of As(III) in the presence of dissolved O2 and their subsequent reactions with As(III) induce the regeneration of some oxidants, which makes the overall quantum yield higher than 1. The homogeneous photolysis of arsenite under 254 nm irradiation can be also proposed as a new method of generating OH radicals.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Regio- and Stereoselectivity in the Reactions of Organometallic Reagents with an Electron-Deficient and an Electron-Rich Vinyloxirane: Applications for Sequential Bis-Allylic Substitution Reactions in the Generation of Vicinal Stereogenic Centers

Authors: Dieter, RK; Huang, Y; Guo, F (In Press) Journal of Organic Chemistry. HERO ID: 1070851

[Less] Vinyloxiranes provide opportunities for bis-allylic substitution reactions and the generation of new . . . [More] Vinyloxiranes provide opportunities for bis-allylic substitution reactions and the generation of new vicinal stereogenic centers if regio- and stereocontrol can be achieved. Ethyl (E)-4,5-epoxy-2-hexenoate affords excellent S(N)2':S(N)2 regioselectivity and anti:syn product diastereoselectivity with dialkyzinc reagents in the presence of CuCN, and conversion of the resultant allylic alcohol to the acetate affords good syn:anti product diastereoselectivity in S(N)2'-selective allylic substitutions with alkylcyanocuprates in THF. (E)-1-(tert-Butyldimethylsilyloxy)-2,3-epoxy-4-hexenonate gives excellent S(N)2':S(N)2 regioselectivity and anti:syn product diastereoselectivity with dialkyzinc reagents in THF or DMF or Grignard reagents in Et(2)O/THF (10/1) in the presence of CuCN. Conversion of the product allylic alcohol into the allylic phosphate affords excellent S(N)2' regioselectivity and syn:anti product diastereoselectivity with lithium alkylcyanocuprates for primary and secondary alkyl transferable ligands, while S(N)2 regioselectivity is observed for the tert-butyl ligand. Reaction conditions have been developed for regio- and stereocontrolled bis-allylic substitution reactions on both electron-rich and electron-deficient alkenyloxiranes, providing a methodology for the generation of vicinal alkane stereogenic centers.

Journal Article
Journal Article

Simultaneous multiagent hyperpolarized (13) C perfusion imaging

Authors: von Morze, C; Bok, RA; Reed, GD; Ardenkjaer-Larsen, JH; Kurhanewicz, J; Vigneron, DB (In Press) HERO ID: 2325070

[Less] PURPOSE: To demonstrate simultaneous hyperpolarization and imaging of three (13) C-labeled . . . [More] PURPOSE: To demonstrate simultaneous hyperpolarization and imaging of three (13) C-labeled perfusion MRI contrast agents with dissimilar molecular structures ([(13) C]urea, [(13) C]hydroxymethyl cyclopropane, and [(13) C]t-butanol) and correspondingly variable chemical shifts and physiological characteristics, and to exploit their varying diffusibility for simultaneous measurement of vascular permeability and perfusion in initial preclinical studies.

METHODS: Rapid and efficient dynamic multislice imaging was enabled by a novel pulse sequence incorporating balanced steady state free precession excitation and spectral-spatial readout by multiband frequency encoding, designed for the wide, regular spectral separation of these compounds. We exploited the varying bilayer permeability of these tracers to quantify vascular permeability and perfusion parameters simultaneously, using perfusion modeling methods that were investigated in simulations. "Tripolarized" perfusion MRI methods were applied to initial preclinical studies with differential conditions of vascular permeability, in normal mouse tissues and advanced transgenic mouse prostate tumors.

RESULTS: Dynamic imaging revealed clear differences among the individual tracer distributions. Computed permeability maps demonstrated differential permeability of brain tissue among the tracers, and tumor perfusion and permeability were both elevated over values expected for normal tissues.

CONCLUSION: Tripolarized perfusion MRI provides new molecular imaging measures for specifically monitoring permeability, perfusion, and transport simultaneously in vivo. Magn Reson Med, 2013. © 2013 Wiley Periodicals, Inc.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Asymmetric Allylation of Ketones and Subsequent Tandem Reactions Catalyzed by a Novel Polymer-Supported Titanium-BINOLate Complex

Authors: Yadav, J; Stanton, GR; Fan, X; Robinson, JR; Schelter, EJ; Walsh, PJ; Pericas, MA (In Press) HERO ID: 2325016

[Less] By using a novel, simple, and convenient synthetic route, enantiopure 6-ethynyl-BINOL (BINOL=1,1-binaphthol) . . . [More] By using a novel, simple, and convenient synthetic route, enantiopure 6-ethynyl-BINOL (BINOL=1,1-binaphthol) was synthesized and anchored to an azidomethylpolystyrene resin through a copper-catalyzed alkyne-azide cycloaddition (CuAAC) reaction. The polystyrene (PS)-supported BINOL ligand was converted into its diisopropoxytitanium derivative in situ and used as a heterogeneous catalyst in the asymmetric allylation of ketones. The catalyst showed good activity and excellent enantioselectivity, typically matching the results obtained in the corresponding homogeneous reaction. The allylation reaction mixture could be submitted to epoxidation by simple treatment with tert-butyl hydroperoxide (TBHP), and the tandem asymmetric allylation epoxidation process led to a highly enantioenriched epoxy alcohol with two adjacent quaternary centers as a single diastereomer. A tandem asymmetric allylation/Pauson-Khand reaction was also performed, involving simple treatment of the allylation reaction mixture with Co2 (CO)8 /N-methyl morpholine N-oxide. This cascade process resulted in the formation of two diastereomeric tricyclic enones in high yields and enantioselectivities.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

The formation of amyloid-like fibrils of α-chymotrypsin in different aqueous organic solvents

Authors: Simona, LM; Laczkób, I; Demcsáka, A; Tótha, D; Kotormán, M; Fülöp, L (In Press) Protein and peptide letters. HERO ID: 1039177

[Less] The formation of amyloid-like fibrils of α-chymotrypsin was studied in aqueous ethanol, methanol, tert-butanol, . . . [More] The formation of amyloid-like fibrils of α-chymotrypsin was studied in aqueous ethanol, methanol, tert-butanol, dimethylformamide and acetonitrile. Thioflavin T (ThT), Congo red (CR) and 1-anilino-8-naphthalenesulfonic acid (ANS) binding, turbidity, intrinsic fluorescence and far-UV circular dichroism measurements were employed to characterize the amyloid fibril formation. The greatest extent of fibril formation after incubation for 24 h at pH 7.0 and at 24 °C was in ethanol at 55%, in methanol and dimethylformamide (DMF) at 60-70% and in tert-butanol at 60-80%. The ANS binding and intrinsic fluorescence results showed that the hydrophobic residues are more solvent-exposed in the aggregated form of α-chymotrypsin. The ThT, CR binding and far-UV CD measurements indicated that the formation of the cross- structure of α-chymotrypsin depends on the polarity of the organic solvent. To determine the role of surface charges in the aggregation, chemically modified forms of α-chymotrypsin were prepared. The citraconylated and succinylated enzymes exhibited a higher and the enzyme forms modified with aliphatic aldehydes a lower propensity for aggregation. These results suggest the important role of surface charges in the aggregation of α-chymotrypsin.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Three New Dimers and Two Monomers of Phenolic Amides from the Fruits of Lycium barbarum and Their Antioxidant Activities

Authors: Gao, K; Ma, D; Cheng, Y; Tian, X; Lu, Y; Du, X; Tang, H; Chen, J (2015) Journal of Agricultural and Food Chemistry. HERO ID: 2849831

[Less] The aims of this study were to complement the current knowledge on the antioxidative composition of . . . [More] The aims of this study were to complement the current knowledge on the antioxidative composition of alcohol extracts from the fruits of Lycium barbarum and to evaluate their antioxidant activities. Three new dimers of phenolic amides, named lyciumamides A (3), B (4), and C (5), together with two monomers, N-E-coumaroyl tyramine (1) and N-E-feruloyl tyramine (2), were isolated from the fruits for the first time with the help of activity-guided chromatography. Compounds 1-5 were evaluated for their antioxidant activities in scavenging 2,2-diphenyl-1-picrylhydrazyl free radical and inhibiting lipid peroxidation in rat liver microsomes induced by ascorbate/Fe(2+), cumine hydroperoxide, or CCl4/reduced form of nicotinamide-adenine dinucleotide phosphate, and the results showed that all of them exhibited strong activities, whereas compounds 1 and 2 were more potent than the reference tert-butyl-4-hydroxyanisole.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Allylic Alcohols: Ideal Radical Allylating Agents?

Authors: Debien, L; Quiclet-Sire, B; Zard, SZ (2015) Accounts of Chemical Research 48:1237-1253. HERO ID: 2849835

[Less] Radical allylations represent effective routes to various alkenes, but to date they have relied chiefly . . . [More] Radical allylations represent effective routes to various alkenes, but to date they have relied chiefly on organostannane derivatives and still suffer from significant limitations with respect to the substitution pattern of the starting allylating agent. Indeed, while substituents at the β-position relative to the radical leaving group are well-tolerated, introduction of α-substituents induces a major complication due to the rapid and usually irreversible isomerization of the starting allylating agents. Although a number of research groups have made substantial efforts to develop heavy-metal-free radical allylations, methods compatible with α-substitution of the allylating agent are still scarce. Furthermore, quite a few systems are limited by the relative inaccessibility of the substrates. This Account summarizes our sustained efforts regarding the development of allylic alcohols into "ideal" radical allylating agents and presents published as well as some unpublished results. The systems we have developed combine the use of readily available xanthates and allylic alcohol derivatives under metal-free conditions to furnish not only alkenes but also aldehydes and saturated and unsaturated ketones through the virtually unprecedented homolytic cleavage of the normally strong C-O or C-C bond. The former route hinges on first converting the allylic alcohol into a 2-fluoro-6-pyridoxy derivative by reacting the corresponding alcoholate with 2,6-difluoropyridine, while the latter relies on attaching a cumyl group to the carbon bearing the free allylic alcohol. Either substrate is then exposed to the action of a suitable xanthate in the presence of a stoichiometric amount of a peroxide, usually lauroyl peroxide (DLP) in refluxing ethyl acetate or di-tert-butyl peroxide (TBHP) in refluxing chlorobenzene for the more difficult cases. Even though C-O or C-C bond homolysis leads to a stabilized 2-fluoro-6-pyridinyloxyl radical or a cumyl radical, respectively, the β-scission in both cases is relatively slow and at the lower limit of useful elementary radical steps. The kinetic barrier of the fragmentation can nevertheless be overcome because of the long relative lifetime of radicals generated by the degenerate transfer of the xanthate group, and this is a key element for success. This novel technology offers numerous advantages. The starting activated allylic alcohol derivatives are readily accessible in two steps from aldehydes or ketones. They can also be obtained by base-induced opening of epoxides. Numerous functional groups are tolerated under the mild reaction conditions for the radical addition-elimination, as nicely illustrated by over 150 examples of radical allylations, not all of which can be included in the present Account. In addition, substitution at both the α- and β-positions of the allylating agent is possible, a rare feature in this area.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Iron-Doped Nickel Oxide Nanocrystals as Highly Efficient Electrocatalysts for Alkaline Water Splitting

Authors: Fominykh, K; Chernev, P; Zaharieva, I; Sicklinger, J; Stefanic, G; Döblinger, M; Müller, A; Pokharel, A; Böcklein, S; Scheu, C; Bein, T; Fattakhova-Rohlfing, D (2015) ACS Nano. HERO ID: 2849826

[Less] Efficient electrochemical water splitting to hydrogen and oxygen is considered a promising technology . . . [More] Efficient electrochemical water splitting to hydrogen and oxygen is considered a promising technology to overcome our dependency on fossil fuels. Searching for novel catalytic materials for electrochemical oxygen generation is essential for improving the total efficiency of water splitting processes. We report the synthesis, structural characterization, and electrochemical performance in the oxygen evolution reaction of Fe-doped NiO nanocrystals. The facile solvothermal synthesis in tert-butanol leads to the formation of ultrasmall crystalline and highly dispersible FexNi1-xO nanoparticles with dopant concentrations of up to 20%. The increase in Fe content is accompanied by a decrease in particle size, resulting in nonagglomerated nanocrystals of 1.5-3.8 nm in size. The Fe content and composition of the nanoparticles are determined by X-ray photoelectron spectroscopy and energy-dispersive X-ray spectroscopy measurements, while Mössbauer and extended X-ray absorption fine structure analyses reveal a substitutional incorporation of Fe(III) into the NiO rock salt structure. The excellent dispersibility of the nanoparticles in ethanol allows for the preparation of homogeneous ca. 8 nm thin films with a smooth surface on various substrates. The turnover frequencies (TOF) of these films could be precisely calculated using a quartz crystal microbalance. Fe0.1Ni0.9O was found to have the highest electrocatalytic water oxidation activity in basic media with a TOF of 1.9 s(-1) at the overpotential of 300 mV. The current density of 10 mA cm(-2) is reached at an overpotential of 297 mV with a Tafel slope of 37 mV dec(-1). The extremely high catalytic activity, facile preparation, and low cost of the single crystalline FexNi1-xO nanoparticles make them very promising catalysts for the oxygen evolution reaction.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Extraction and purification of beta-amylase from stems of Abrus precatorius by three phase partitioning

Authors: Sagu, ST; Nso, EJ; Homann, T; Kapseu, C; Rawel, HM (2015) Food Chemistry 183:144-153. HERO ID: 2849879

[Less] The stems of Abrus precatorius were used to extract a beta-amylase enriched fraction. A three phase . . . [More] The stems of Abrus precatorius were used to extract a beta-amylase enriched fraction. A three phase partitioning method and a Doehlert design with 3 variables (ratio of crude extract/t-butanol, the ammonium sulphate saturation and pH) were used. The data was fitted in a second-order polynomial model and the parameters were optimized to enrich beta-amylase. Experimental responses for the modulation were recovery of activity and the purification factor. The optimal conditions were: a ratio of crude extract/t-butanol of 0.87 (v/v), saturation in ammonium sulphate of 49.46% (w/v) and a pH of 5.2. An activity recovery of 156.2% and a purification factor of 10.17 were found. The enriched enzyme was identified as a beta-amylase and its molecular weight was 60.1kDa. Km and Vmax values were 79.37mg/ml and 5.13U/ml, respectively and the highest activity was registered at a temperature of 70°C and a pH between 6 and 6.5. A significant stabilization of the beta-amylase was observed up to 65°C.