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1.
Uwe Bhme Ines C. Foehn 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(11):o613-o616
TBPY‐5‐34‐(Butane‐1,4‐diyl)(2‐{[1‐(2‐oxidophenyl)ethylidene‐κO]amino‐κN}ethanolato‐κO)silicon, C14H19NO2Si, crystallizes in two modifications. The monoclinic form, (IIm), was obtained by crystallization over a period of 2 d at room temperature; the orthorhombic form, (IIo), crystallized overnight at 248 K. The main difference between the two molecular structures involves the angles in the equatorial plane of the trigonal bipyramid around silicon. Form (IIm) has an O—Si—O angle of ca 121° and O—Si—C angles of ca 121 and 116°. In form (IIo), the corresponding angles are ∼123, 124 and 111°. There are also significant differences in the packing: (IIm) shows π stacking, whereas (IIo) does not. 相似文献
2.
Alessandro D' Aprano Dorina Ines Donato Antonio Carrubba Doctor in Chemistry thesis of A. Carrubba 《Journal of solution chemistry》1983,12(3):209-220
Conductance measurements are reported for LiPi, NaPi, KPi, RbPi, CsPi, Bu4NPi, Bu4NBr, Bu4NClO4, Bu4NNO3, and Bu4NBBu4 at 25°C in -butyrolactone-sulfolane mixtures. In these mixtures of solvents that are practically homomorphous, isodielectic and with comparable dipole moments, the ion pair association and ionic mobilities of large ions conform to the expectations of the primitive model. Electrolytes containing lithium or sodium ions show anomalies indicating that other factors besides shape, dipole moment, and polarizability of the solvent molecules are involved in the association and transport processes of these ions. 相似文献
3.
Žydrė Šaltienė Natalija Jatulienė Mudis Šalkauskas Daiva Brukštienė Asta Ruzgytė Aušra Tarasevičiūtė Julius Kalibatas 《Accreditation and quality assurance》2005,10(8):444-451
The estimation scheme of uncertainty of determination of 1-hydroxypyrene (1-OHP) in urine was developed analysing the main
stages of the analytical procedure: (1) preparation of 1-OHP standards, (2) creation of the calibration curve for the high
performance liquid chromatography (HPLC) analysis method with the evaluation of recovery, (3) measuring procedure of aliquot
of urine, (4) adjusting the pH of aliquot and hydrolysis with enzyme, (5) solid phase extraction, (6) concentration of the
extract, (7) injection of the extract to chromatograph and analysing by the HPLC method, (8) calculation of 1-OHP mass from
the calibration curve, (9) calculation of 1-OHP concentration in urine. The evaluation of the uncertainty is based on quantification
of individual components. Combined uncertainty was calculated using the law of propagation of uncertainties according to the
EURACHEM/CITAC guidelines. Level dependence of the uncertainty arises from the calibration curve.
The limits of detection and quantification were found to be equal to 0.03 and 0.1 ng/mL, respectively. The calculated expanded
level-dependent uncertainty covers 47–27–25% within the concentration range 0.03–0.1–0.4 ng/mL with the materials and equipment
used. These parameters could easily be recalculated according to the proposed scheme if there are some changes in the analysis
procedure. 相似文献
4.
Batinić-Haberle I Spasojević I Stevens RD Hambright P Neta P Okado-Matsumoto A Fridovich I 《Dalton transactions (Cambridge, England : 2003)》2004,(11):1696-1702
Three new Mn(III) porphyrin catalysts of O2.-dismutation (superoxide dismutase mimics), bearing ether oxygen atoms within their side chains, were synthesized and characterized: Mn(III) 5,10,15,20-tetrakis[N-(2-methoxyethyl)pyridinium-2-yl]porphyrin (MnTMOE-2-PyP(5+)), Mn(III)5,10,15,20-tetrakis[N-methyl-N'-(2-methoxyethyl)imidazolium-2-yl]porphyrin (MnTM,MOE-2-ImP(5+)) and Mn(III) 5,10,15,20-tetrakis[N,N'-di(2-methoxyethyl)imidazolium-2-yl]porphyrin (MnTDMOE-2-ImP(5+)). Their catalytic rate constants for O2.-dismutation (disproportionation) and the related metal-centered redox potentials vs. NHE are: log k(cat)= 8.04 (E(1/2)=+251 mV) for MnTMOE-2-PyP(5+), log k(cat)= 7.98 (E(1/2)=+356 mV) for MnTM,MOE-2-ImP(5+) and log k(cat)= 7.59 (E(1/2)=+365 mV) for MnTDMOE-2-ImP(5+). The new porphyrins were compared to the previously described SOD mimics Mn(III) 5,10,15,20-tetrakis(N-ethylpyridinium-2-yl)porphyrin (MnTE-2-PyP(5+)), Mn(III) 5,10,15,20-tetrakis(N-n-butylpyridinium-2-yl)porphyrin (MnTnBu-2-PyP(5+)) and Mn(III) 5,10,15,20-tetrakis(N,N'-diethylimidazolium-2-yl)porphyrin (MnTDE-2-ImP(5+)). MnTMOE-2-PyP(5+) has side chains of the same length and the same E(1/2), as MnTnBu-2-PyP(5+)(k(cat)= 7.25, E(1/2)=+ 254 mV), yet it is 6-fold more potent a catalyst of O2.-dismutation , presumably due to the presence of the ether oxygen. The log k(cat)vs. E(1/2) relationship for all Mn porphyrin-based SOD mimics thus far studied is discussed. None of the new compounds were toxic to Escherichia coli in the concentration range studied (up to 30 microM), and protected SOD-deficient E. coli in a concentration-dependent manner. At 3 microM levels, the MnTDMOE-2-ImP(5+), bearing an oxygen atom within each of the eight side chains, was the most effective and offered much higher protection than MnTE-2-PyP(5+), while MnTDE-2-ImP(5+) was of very low efficacy. 相似文献
5.
Hair color changes and protein damage caused by ultraviolet radiation 总被引:12,自引:0,他引:12
Santos Nogueira AC Joekes I 《Journal of photochemistry and photobiology. B, Biology》2004,74(2-3):109-117
Ultraviolet and visible radiations are known to damage hair. However, quantitative data relating damage to hair type, proteins and color to the radiation wavelength are missing. We studied the effect of UV plus visible, UVA plus visible, visible mercury-vapor lamp radiation and sunlight on (blended) virgin dark-brown, blond and red hair and (one head) virgin black and curly dark-brown hair. All hair types showed a substantial increase in protein loss in water after lamp and sun irradiation. The damaging effect of UVB was about 2-5 times higher than that of UVA plus visible radiation, depending on the hair type. Significant color changes were also observed in every hair type, after lamp and sun irradiation, being more pronounced for the light colored hairs. The luminosity difference parameter was the major contributor to the hair color changes, but significant changes in the red-green and yellow-blue parameters of every hair were observed. In this case, the damaging effect is ascribable mainly to UVA radiation. No significant changes in the mechanical properties or topography were observed in any case. We discuss these results in terms of hair type and composition and melanin types. 相似文献
6.
Alessandro D'Aprano Ines Dorina Donato Vincenzo Turco Liveri 《Journal of solution chemistry》1989,18(8):785-793
Static dielectric constants, refractive indices and viscosities of 1-pentanol +2-methyl-2-butanol mixtures were measured at 5, 25 and 45°C. The results show that the mixing of the two isomers modifies the polarizability and the resistence of viscous flow of the system depending on the composition and temperature. Short range intermolecular interactions producing hetero-alcohol open dimers are considered. 相似文献
7.
Graziano Guella Ines Mancini Giuseppe Chiasera Francesco Pietra 《Helvetica chimica acta》1992,75(1):310-322
8.
Reported here are two novel quasi-racemic (bis)indole alkaloids, cycloaplysinopsin A (5) and cycloaplysinopsin B (6), isolated from tropical Indo-Pacific (Comoros, Philippines) scleractinian corals of the family Dendrophylliidae. Although their structures suggest a Diels-Alder cycloaddition origin from aplysinopsin-type precursors, neither experiments, nor theory allowed us to clearly distinguish an enzymatic process with scarce enantioselection from the intrusion of an adventitious catalyst in the coral extracts, where the chiral environment caused a slight asymmetric induction. 相似文献
9.
It is shown that an unidentified marine demosponge of Brittany contains two unique lipids consisting of glycerol etherified by a C12 trienic linear alcohol and esterified by 4-hydroxybenzoic acid. The latter is attached to the secondary position of glycerol in bretonin A (= 3-[((4E, 6E, 8E)-dodeca-4,6,8-trienyl)oxy]-2-(4-hydroxy-benzoyl)propan-1-ol; 1a ), and to the other primary position of glycerol in isobretonin A ( = (+)-3-[((4E, 6E, 8E)-dodeca-4,6,8-trienyl)oxy]-1-(4-hydroxybenzoyl)propan-2-ol; (+) -2 ). The structures are based on NMR and MS data, including the ones of the acetylation product (?)- 1b of 1a . 相似文献
10.
A review is given on optical means for single shot testing (probing) as well as continuous monitoring (sensing) of heavy metal ions (HMs). Following an introduction into indicator based approaches, we discuss the types of indicator dyes and polymeric supports used, as well as existing sensing schemes for HMs. The wealth of information is compiled in the form of tables and critically reviewed. Notwithstanding the tremendous work performed so far, it is obvious that still severe limitations do exist in terms of selectivity, limits of detection, dynamic ranges, applicability to specific problems, and reversibility. On the other hand, such sensors have found — and will find — their application whenever rapid and cost-effective testing is required, where personnel is scarce or unskilled, and in field tests. Despite their limitations, the number of such sensors (and of irreversible probes) for HMs is likely to increase in future. 相似文献