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61.
Sanna C La Mesa C Mannina L Stano P Viel S Segre A 《Langmuir : the ACS journal of surfaces and colloids》2006,22(14):6031-6041
We investigated the aggregation properties of two classes of aromatic and hydrophobic compounds, namely chloroacetamides and ethyl 3-phenyl-2-nitropropionates, in moderately concentrated aqueous solution (millimolar range). The identification of all species present in solution under specific experimental conditions was performed by 1D and 2D NMR, pulsed gradient spin-echo NMR, and dynamic light scattering techniques. Some physical-chemical properties (viscosity, surface tension, and colligative properties) of the aqueous solutions were also determined. Both classes of compounds behave quite similarly: in solution, three distinct species, namely a monomeric species, small and mobile aggregates, and large and stiff aggregates, are observed. The results give insight into a new class of aggregates, held together by pi-pi interactions, which show an unusual associative behavior in water. 相似文献
62.
Cabras T Inzitari R Fanali C Scarano E Patamia M Sanna MT Pisano E Giardina B Castagnola M Messana I 《Journal of separation science》2006,29(17):2600-2608
In the present study the analytical potential of HPLC-MS/MS was utilized for the structural characterization of a post-translational modification of statherin. Human salivary statherin (M(av)5380.0 +/- 0.3 Da) is transformed by the action of transglutaminase 2 into a cyclic derivative with an average molecular mass of 5363.0 +/- 0.3 Da. The intra-molecular bridge is generated by the loss of an ammonia molecule between the unique Ione-pair donating nucleophile Lys-6 and one acceptor among the seven glutamine residues of statherin. Digestion of the cyclic derivative with chymotrypsin, proteinase K, and carboxypeptidase Y, monitored by HPLC-electrospray ionization-ion trap-mass spectrometric analysis, demonstrated that cyclization involved almost specifically Gln-37 (> 95%), with the percentage of Gln-39 implicated in the cross-linkiing being less than 5%. The main derivative was named cyclostatherin Q37. Guineapig transglutaminase 2 showed high affinity for statherin in vitro (Km = 0.65 +/- 0.06 microM). Cyclo-statherin was detected in vivo by HPLC-electrospray ionization ion trap-mass spectrometry analysis of whole human saliva and it accounted for about 1% of total statherin. Detection of cyclo-statherin in whole saliva is suggestive of a putative role of this molecule in the formation of the "oral protein pellicle". 相似文献
63.
Sanna Mönkölä 《Journal of Computational and Applied Mathematics》2010,234(6):1904-1911
The classical way of solving the time-harmonic linear acousto-elastic wave problem is to discretize the equations with finite elements or finite differences. This approach leads to large-scale indefinite complex-valued linear systems. For these kinds of systems, it is difficult to construct efficient iterative solution methods. That is why we use an alternative approach and solve the time-harmonic problem by controlling the solution of the corresponding time dependent wave equation.In this paper, we use an unsymmetric formulation, where fluid-structure interaction is modeled as a coupling between pressure and displacement. The coupled problem is discretized in space domain with spectral elements and in time domain with central finite differences. After discretization, exact controllability problem is reformulated as a least-squares problem, which is solved by the conjugate gradient method. 相似文献
64.
Ruohola AM Koissi N Andersson S Lepistö I Neuvonen K Mikkola S Lönnberg H 《Organic & biomolecular chemistry》2004,2(13):1943-1950
Reactions of 9-ethylguanine, 2'-deoxyguanosine and guanosine with bromomalondialdehyde in aqueous buffers over a wide pH-range were studied. The main products were isolated and characterized by (1)H and (13)C NMR and mass spectroscopy. The final products formed under acidic and basic conditions were different, but they shared the common feature of being derived from glyoxal. Among the 1 : 1 adducts, 1,N(2)-(trans-1,2-dihydroxyethano)guanine adduct (6) predominated at pH < 6 and N(2)-carboxymethylguanine adduct (10a,b) at pH > 7. In addition to these, an N(2)-(4,5-dihydroxy-1,3-dioxolan-2-yl)methylene adduct (11a,b) and an N(2)-carboxymethyl-1,N(2)-(trans-1,2-dihydroxyethano)guanine adduct (12) were obtained at pH 10. The results of kinetic experiments suggest that bromomalondialdehyde is significantly decomposed to formic acid and glycolaldehyde under the conditions required to obtain guanine adducts. Glycolaldehyde is oxidized to glyoxal, which then modifies the guanine base more readily than bromomalondialdehyde. Besides the glyoxal-derived adducts, 1,N(2)-ethenoguanine (5a-c) and N(2),3-ethenoguanine adducts (4a-c) were formed as minor products, and a transient accumulation of two unstable intermediates, tentatively identified as 1,N(2)-(1,2,2,3-tetrahydroxypropano)(8) and 1,N(2)-(2-formyl-1,2,3-trihydroxypropano)(9) adducts, was observed. 相似文献
65.
A liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) method based on time-of-flight (TOF) MS with polarity switching and continuous exact mass measurement using a LockSpray ion source was developed for fast evaluation of the total flavonoid content in plants and foodstuffs. No complicated sample preparation was needed, but only a dilution of the extracts. A fast generic gradient elution and wide mass range acquisition was used with good sensitivity. The total analysis time was only 23 min. The ion chromatograms for flavonoid compounds were automatically extracted, and the fragmentation patterns obtained using positive ion mode and exact mass data for both polarities were used for the tentative identification of compounds. Software-based automated searching of molecular ions for flavonoids and their glycosides (xylosides/arabinosides, rhamnosides, glucosides/galactosides) from total ion chromatograms was used. The compounds were quantified using quercetin, quercitrin, rutin and kuromanine as external standards and dextromethorphan as an internal standard. The detection limits ranged from 0.01-0.04 microg/mL, while the quantitation ranges obtained were 0.2-10 microg/mL for anthocyanins and 0.2-4 microg/mL for the other flavonoids. The accuracies within these ranges varied between 80-120% and precision was in the range 0-14% (relative standard deviation). Flavonoid contents of two medicinal plants (Hypericum perforatum and Rhodiola rosea), two grape red wines, two orange juices and two green teas were evaluated using the method, and the results obtained were in good agreement with those published previously. 相似文献
66.
Morgenstern B Steinhauser S Hegetschweiler K Garribba E Micera G Sanna D Nagy L 《Inorganic chemistry》2004,43(10):3116-3126
The complex formation of vanadium(IV) with 1,3,5-triamino-1,3,5-trideoxy-cis-inositol (taci) and 1,3,5-trideoxy-1,3,5-tris(dimethylamino)-cis-inositol (tdci) was studied in aqueous solution and in the solid state. The formation constants of [V(IV)O(taci)](2+), [V(IV)O(tdci)](2+), and [V(IV)(tdci)(2)](4+) and of the deprotonation product [V(IV)(tdci)(2)H(-)(1)](3+) were determined (25 degrees C, 0.1 M KNO(3)). Cyclic voltammetry measurements established a reversible one-electron transfer for the [V(IV)(tdci)(2)H(-)(m)]((4)(-)(m))/[V(III)(tdci)(2)H(-)(n)]((3)(-)(n)) couple (0 相似文献
67.
Anne-Marja Uusitalo Tuula T. Pakkanen Minna Krger-Laukkanen Lauri Niinist Kimmo Hakala Santeri Paavola Barbro Lfgren 《Journal of molecular catalysis. A, Chemical》2000,160(2):343-356
Heterogeneous metallocene catalysts were prepared by adsorbing rac-Et(Ind)2ZrCl2 on a modified silica surface in solution. The modification of silica was conducted in gas phase with atomic layer chemical vapor deposition (ALCVD) technique, where the silica, preheated at either 350 or 600°C, was allowed to react with vaporized trimethylaluminum (TMA) at 250°C. Modified carriers and heterogeneous catalysts were characterized with FTIR, 1H MAS (magic-angle spinning) NMR, 13C, and 29Si CP (cross-polarization) MAS NMR spectroscopies and elemental analyses. In the reaction of TMA with silica, a saturated surface was formed consisting of different (---O)4−nSi(CH3)n (n=1, 2 or 3) and ---AlCH3 groups. The ratio of ---SiMe to ---AlMe groups was approximately 1.5 in the TMA/SiO2 carriers. When the metallocene was adsorbed onto the carrier it seemed to react with the surface ---AlCH3 groups and possibly ---ZrCH3 groups were formed. Heterogeneous catalysts were tested in the polymerization of ethylene and propylene in the presence of methylalumoxane (MAO). And they produced similar polymer as the homogeneous rac-Et(Ind)2ZrCl2 catalyst, but with lower activity. A catalyst with the best activity was achieved from silica that was preheated at 600°C. Moreover, leaching of catalyst was examined whereupon a part of zirconium was observed to desorb from the carrier. 相似文献
68.
K. Helariutta J.F.C. Cocks T. Enqvist P.T. Greenlees P. Jones R. Julin S. Juutinen P. Jämsen H. Kankaanpää H. Kettunen P. Kuusiniemi M. Leino M. Muikku M. Piiparinen P. Rahkila A. Savelius W.H. Trzaska S. Törmänen J. Uusitalo R.G. Allatt P.A. Butler R.D. Page M. Kapusta 《The European Physical Journal A - Hadrons and Nuclei》1999,6(3):289-302
Prompt and delayed γ-rays have been observed from very neutron deficient 192–195Po nuclei by using the recoil-decay tagging (RDT) and recoil gating techniques. The yrast levels up to the (10+) state in the 192Po were identified for the first time. Comprehensive data for 194Po rendered it possible to extend the yrast line and to observe several positive and negative parity non-yrast states. In
the odd-mass isotopes 193Po and 195Po, favoured and unfavoured states on top of the 13/2+ state have been identified. The results are discussed within the simple vibrator and rotor pictures as well as in the framework
of coexisting spherical and deformed-intruder structures.
Received: 5 July 1999 / Revised version: 7 September 1999 相似文献
69.
D. R. Wiseman A. N. Andreyev R. D. Page M. B. Smith I. G. Darby S. Eeckhaudt T. Grahn P. T. Greenlees P. Jones R. Julin S. Juutinen H. Kettunen M. Leino A. -P. Leppänen M. Nyman J. Pakarinen P. Rahkila M. Sandzelius J. Sarén C. Scholey J. Uusitalo 《The European Physical Journal A - Hadrons and Nuclei》2007,34(3):275-281
γ -ray transitions in the neutron-deficient nuclei 190, 197Po have been identified using the JUROGAM Ge detector array coupled to the RITU gas-filled separator and the GREAT spectrometer.
The yrast band of 190Po has been firmly established through γ -γ coincidences and extended up to a spin and parity of 14+. It displays similar behaviour to its isotones 186Hg and 188Pb above the 4+ level, thus confirming its prolate nature. In 197Po the band built upon the 13/2+ isomer has been extended up to a spin and parity of 33/2+, while the non-yrast band has been observed for the first time. The behaviour of 197Po is found to be similar to that of the nearby even-mass isotopes, which is consistent with the model in which the i
13/2 neutron is weakly coupled to the states in the even-even core. 相似文献
70.
S. Hofmann D. Ackermann S. Antalic H. G. Burkhard V. F. Comas R. Dressler Z. Gan S. Heinz J. A. Heredia F. P. Heßberger J. Khuyagbaatar B. Kindler I. Kojouharov P. Kuusiniemi M. Leino B. Lommel R. Mann G. Münzenberg K. Nishio A. G. Popeko S. Saro H. J. Schött B. Streicher B. Sulignano J. Uusitalo M. Venhart A. V. Yeremin 《The European Physical Journal A - Hadrons and Nuclei》2007,32(3):251-260
The fusion reaction of 48Ca projectiles with 238U target nuclei was studied at the velocity filter SHIP of GSI in Darmstadt. Two decay chains were measured, which fully confirm
data that were previously assigned to the isotope 283112 in experiments at the Flerov Laboratory in Dubna. Two other events are consistent with a 50% spontaneous-fission (SF)
branch of this isotope. The mean value obtained for the half-life of 283112 is (6.9 +6.9
-2.3 s, the α energy is (9.520±0.015) MeV, and the total kinetic energy (TKE) of SF is (238±14) MeV. The half-life of the α decay
daughter nucleus 279Ds is (0.18 +0.32
-0.07 s, and the TKE of SF is (210 +32
-11 MeV. The cross-section deduced from all four events is (0.72 +0.58
-0.35 pb , measured at an excitation energy of 34.6MeV of the compound nucleus 286112. 相似文献