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1.
Nurminen TA Holopainen JM Zhao H Kinnunen PK 《Journal of the American Chemical Society》2002,124(41):12129-12134
Sphingomyelinase, SMase (EC 3.1.4.12), was coupled onto amino-derivatized acrylate microspheres and was shown to retain its catalytic activity. The immobilized enzyme allows one to carry out topical enzymatic reaction in a controlled manner. Accordingly, these spheres were held with a micropipet and using micromanipulator brought into contact with a giant liposome membrane composed of phosphatidylcholine and sphingomyelin (SOPC/C16:0-SM, 0.75:0.25, molar ratio), representing the substrate for the immobilized enzyme. The macroscopic consequences of the enzyme reaction were visualized using fluorescence microscopy as well as differential interference contrast microscopy. The surface contact of the giant vesicle and immobilized enzyme causes membrane microdomain formation and domain clustering (capping) in the membrane and subsequent shedding of small vesicles from the membrane into the interior of the giant liposome. The method described represents a novel approach to study enzymatic reactions and allows manipulating giant vesicles as well as cultured cells in a spatially controlled manner. 相似文献
2.
The investigation of europium(III) sulphate hydrate and samarium(III) sulphate hydrate was performed by thermal analysis (TG-DTG) and simultaneous infrared evolved gas analysis-Fourier transformed infrared (EGA-FTIR) spectroscopy. The TG, DTG and DTA curves were recorded at the 25–1400 °C in the dynamic air atmosphere by TG/DTA analyser. The infrared evolved gas analysis was obtained on the FTIR spectrometer. Eu2(SO4)3·nH2O (n = 3.97) and Sm2(SO4)3·nH2O (n = 8.11) were analysed, the dehydration and decomposition steps were investigated and the water content was calculated. The formation of different oxysulphates was studied.
The trace rare earth elements in Eu and Sm sulphates were determined by ICP-MS. The concentration of trace Eu, Sm, La, Gd, Y and Ce ranged from 3.9 × 10−6 to 1.5 × 10−4% (m/m). 相似文献
3.
Paavo?Mansikkam?ki Manu?Lahtinen Kari?RissanenEmail author 《Cellulose (London, England)》2005,12(3):233-242
The completeness of mercerisation can be evaluated by investigating the changes in the crystalline regions of cellulose from
cellulose I (C-I) to cellulose II (C-II) by the X-ray powder diffraction method. Mercerisation experiments in four different
solution systems: ethanol/water, acetone, DMSO and xylene, are reported. Also the effect of some additives, external pressure,
treatment time and alkalisation temperature were studied. In two-phase solvent systems, structural changes of cellulose crystallites
depended primarily on the distribution and solubility of sodium hydroxide in the solvent phases. The sodium hydroxide concentration
in the hydrophilic phase must exceed 7–8 w/w-% before complete crystal change from C-I to C-II can occur. The precipitation
of sodium hydroxide due to high concentration prevents the successful use of one-phase ethanol/water system in slurry process.
On the contrary, the 2-propanol/water/sodium hydroxide system separates into two layers; to the water-rich lower layer and
the 2-propanol-rich upper layer, where the sodium hydroxide remains mainly in the water-rich lower layer. This prevents the
precipitation of sodium hydroxide and promotes the alkalisation of cellulose. Ammonium chloride and ammonium hydroxide clearly
had a positive effect by promoting the crystal changes, however, the urea concentration used in this study was obviously too
small. In the advantageous two-phase 2-propanol/water systems, the alkalisation time was only 15 min when the treatment temperature
was kept between 0 and 10 °C. Reduced external pressure was found to have a small but still detectable positive effect on
cellulose alkalisation while over-pressure prevented crystal changes. 相似文献
4.
The allomerization of chlorophyll b in methanol produced 132(S)-hydroxy-10-methoxychlorophyll b in a yield of ca. 8%. The formation of this allomer was totally unexpected, as 10-substituted chlorophylls have never been reported before. The structure of the new chlorophyll b derivative was determined on the basis of UV/Vis, FAB-MS, 1H NMR and 2D ROESY NMR spectra. This letter focuses on the NMR analysis. 相似文献
5.
The mass spectral fragmentation patterns of 1,3-oxathiane and several of its alkyl derivatives have been recorded. Of the nine possible modes of ring cleavage yielding fragments containing two to four atoms, only six modes were actually observed and, moreover, two of them clearly predominated. The modes of fragmentation of 1,3-oxathianes differ from those of 1,3-dioxanes, but resemble closely those observed for 1,3-oxathiolanes when the different ring sizes are taken into account. 相似文献
6.
The enolate anion of chlorophyll b (Chl b) has been synthesized under deoxygenated conditions and its electronic structure characterized for the first time by 1H NMR and electronic absorption spectroscopy. The formation of the enolate anion caused a marked perturbation to the 18 π-electron [18]diazaannulene aromatic pathway of Chl b. This perturbation appeared as noticeable upfield shifts, exceeding 1 ppm, for the meso-CH protons of the Chl b enolate anion. Nevertheless, the enolate anion remained diatropic, maintaining aromaticity in its delocalized macrocycle. 相似文献
7.
Carbonyl carbon (13)C NMR chemical shifts delta(C)(C[double bond]O) measured in this work for a wide set of substituted phenyl benzoates p-Y-C(6)H(4)CO(2)C(6)H(4)-p-X (X = NO(2), CN, Cl, Br, H, Me, or MeO; Y = NO(2), Cl, H, Me, MeO, or NMe(2) ) have been used as a tool to study substituent effects on the carbonyl unit. The goal of the work was to study the cross-interaction between X and Y in that respect. Both the phenyl substituents X and the benzoyl substituents Y have a reverse effect on delta(C)(C[double bond]O). Electron-withdrawing substituents cause shielding while electron-donating ones have an opposite influence, with both inductive and resonance effects being significant. The presence of cross-interaction between X and Y could be clearly verified. Electronic effects of the remote aromatic ring substituents systematically modify the sensitivity of the C[double bond]O group to the electronic effects of the phenyl or benzoyl ring substituents. Electron-withdrawing substituents in one ring decrease the sensitivity of delta(C)(C[double bond]O) to the substitution of another ring, while electron-donating substituents inversely affect the sensitivity. It is suggested that the results can be explained by substituent-sensitive balance of the contributions of different resonance structures (electron delocalization, Scheme 1). 相似文献
8.
Mikko Keränen Marcin Gnyba Paavo Raerinne Terho Kololuoma Arto Maaninen Juha T. Rantala 《Journal of Sol-Gel Science and Technology》2004,31(1-3):369-372
Sol–gel adhesive material for isostatic hotpressing lamination process was synthesized using 3-aminopropyltrimethoxysilane (APTES), 3-glycidyloxypropyltrimethoxysilane (GPTS) and methacryloxypropyltrimethoxysilane (MPTS) as precursors. Reaction dynamics between APTES and GPTS was followed on-line with Raman spectroscopy. The lamination process was optimized by varying hotpressing times and pressures at the constant temperature. Mechanical shear strength properties were found to be excellent for studied composition, 25–30 kg/cm2 at its best. One possible application of laminated polycarbonate (PC) structure is a soldier helmet visor. Therefore, the ballistic protection properties were tested by shooting with 1.1 gram standard fragment, and determining the v50 velocity value, which corresponds to 50% perforation. The laminated structure gave 5.7% better protection compared with the solid polycarbonate. The laminated components were found to have high optical transparency at the visible wavelengths as well as high environmental stability. 相似文献
9.
Yohannes G Wiedmer SK Tuominen EK Kinnunen PK Riekkola ML 《Analytical and bioanalytical chemistry》2004,380(5-6):757-766
Lipid membranes are well recognized ligands that bind peripheral and integral proteins in a specific manner and regulate their function. Cytochrome c (cyt c) is one of the partner peripheral protein that binds to the lipid membranes via electrostatic and hydrophobic interactions. In this study, asymmetrical flow field-flow fractionation (AsFlFFF) was used to compare the interactions of cyt c with the acidic phospholipid 1,2-dimyristoyl-sn-glycero-3-phospho-rac-glycerol (DMPG), oleic acid (OA), and sodium dodecyl sulfate (SDS). The influence of pH and the cyt c–lipid molar mass ratios were evaluated by monitoring the diffusion coefficients and particle diameter distributions obtained for the free and lipid-bound protein. The hydrodynamic particle diameter of cyt c (pI 10) was 4.1 nm at pH 11.4 and around 4.2 nm at pH 7.0 and 8.0. Standard molar mass marker proteins were used for calibration to obtain the molar masses of free cyt c and its complexes with lipids. AsFlFFF revealed the binding of cyt c to DMPG and to OA to be mainly electrostatic. In the absence of electrostatic interactions, minor complex formation occurred, possibly due to the extended lipid anchorage involving the hydrophobic cavity of cyt c and the hydrocarbon chains of DMPG or SDS. The possibility of the formation of the molten globule state of cyt c, induced by the interaction between cyt c and lipids, is discussed.Electronic Supplementary Material Supplementary material is available for this article at 相似文献
10.
Three non-specific methods for the extraction of total petroleum hydrocarbons (TPH) from soil into organic solvent were compared.
The techniques used for sample preparation were Soxhlet extraction, closed-vessel microwave-assisted extraction, and CEN shake
extraction. The total concentrations of extracted compounds in the boiling point range of C10–C40 were determined by gas chromatography
with flame ionization detection. The best recovery (99%) and repeatability (±3%) from standard oil mixtures were obtained
with microwave-assisted extraction. However, the different extraction methods exhibited different behaviour when spiked soil
samples were extracted. The best repeatability was obtained with CEN shake extraction (±6%) but the repeatability values for
Soxhlet and microwave-assisted methods were quite high (>20%). However, the larger uncertainties of the latter extraction
methods does not necessarily limit the applicability of these methods to the determination of petroleum hydrocarbons in soil,
as in the assessment of soil contamination the expanded uncertainty of the result is usually not limited by analytical uncertainty,
but rather by the uncertainty of the primary sampling stage. However, distinctive variation found in the chromatographic profiles
illustrates that discretion should be obeyed when chromatograms obtained after application of different extraction methods
on petroleum contaminated samples are to be used in the fingerprinting or age dating studies. Otherwise, misleading conclusions
concerning the age of spillage could be drawn. 相似文献