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排序方式: 共有68条查询结果,搜索用时 15 毫秒
1.
Sabatino Nacson Alex. G. Harrison William R. Davidson 《Journal of mass spectrometry : JMS》1986,21(6):317-319
The collision-induced dissociation (CID) mass spectra of protonated cocaine and protonated heroin have been measured using a triple quadrupole mass spectrometer at 50 eV ion/neutral collision energy for protonated molecules prepared by different protonating agents. The CID mass spectra of protonated cocaine using H+(H2O)n, H+(NH3)n and H+((CH3)2NH)n as protonating agents are essentially identical and it is concluded that, regardless of the initial site of protonation, the fragmentation reactions occurring on collisional activation are identical. By contrast, protonated heorin prepared with H+(H2O)n and H+(NH3)n as protonating agents show substantial differences. That formed by reaction of H+(H2O)n shows a much more abundant peak corresponding to loss of CH3CO2H. From a comparison with model compounds, and from a consideration of the three-dimensional structure of heroin, it is concluded that with H+(H2O)n as protonating agent significant protonation occurs at the acetate group attached to the alicyclic ring, leading to acetic acid loss on collisional activation, but that reaction of H+(NH3)n leads to protonation at the nitrogen function. The proton attached to nitrogen cannot interact with the acetate group and, consequently, the probability of loss of acetic acid on collislional activation is greatly reduced. 相似文献
2.
Generic applications of 13C‐detected NMR diffusion to formulated systems with suppression of thermal convection induced by proton decoupling 下载免费PDF全文
Jianbo Hou Yiyong He Paolo Sabatino Ling Yuan David Redwine 《Magnetic resonance in chemistry : MRC》2016,54(7):584-591
Fast and effective structural/compositional analysis on formulated systems represents one of the major challenges encountered in analytical science. 13C‐detected diffusion represents a promising tool to tackle the aforementioned challenges, particularly in industry. Toward exploring the generic applications of 13C‐detected diffusion, thermal convection induced by 1H decoupling has been identified as a key factor that resulted in significantly reduced resolution in the diffusion dimension. Optimization of experimental parameters and utilization of double‐stimulated echo‐based pulse sequence both can effectively suppress the thermal convection caused by the 1H decoupling, the success of which allows robust and generic applications of 13C‐detected diffusion to systems from mixtures of small molecules, polymer blends, and copolymers to actual complex formulated systems. The method is particularly powerful in differentiating small molecules from polymers, polymer blends from copolymers, and end‐group analysis. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
3.
Mariangela Potenza Giuseppina Sabatino Francesca Giambi Luca Rosi Anna Maria Papini Luigi Dei 《Analytical and bioanalytical chemistry》2013,405(2-3):691-701
The chemical analysis of egg-based wall paintings—the mezzo fresco technique—is an interesting topic in the characterisation of organic binders. A revised procedure for a dot-enzyme-linked immunosorbent assay (dot-ELISA) able to detect protein components of egg-based wall paintings is reported. In the new dot-ELISA procedure we succeeded in maximizing the staining colour by adjusting the temperature during the staining reaction. Quantification of the colour intensity by visible reflectance spectroscopy resulted in a straight line plot of protein concentration against reflectance in the wavelength range 380–780 nm. The modified dot-ELISA procedure is proposed as a semi-quantitative analytical method for characterisation of protein binders in egg-based paintings. To evaluate its performance, the method was first applied to standard samples (ovalbumin, whole egg, egg white), then to model specimens, and finally to real samples (Giotto’s wall paintings). Moreover, amino acid analysis performed by innovative ultra-performance liquid chromatography was applied both to standards and to model samples and the results were compared with those from the dot-ELISA tests. In particular, after protein hydrolysis (24 h, 114 °C, 6 mol L?1 HCl) of the samples, amino acid derivatization by use of 6-aminoquinolyl-N-hydroxysuccinimidyl carbamate enabled reproducible analysis of amino acids. This UPLC amino acid analysis was rapid and reproducible and was applied for the first time to egg-based paintings. Because the painting technique involved the use of egg-based tempera on fresh lime-based mortar, the study enabled investigation of the effect of the alkaline environment on egg-protein detection by both methods. Figure
Model wall paintings specimens and typical dot-ELISA stains for egg proteins. 相似文献
4.
Caruso R Gambino GL Scordino M Sabatino L Traulo P Gagliano G 《Natural product communications》2011,6(12):1939-1943
The influence of the wine distillation process on methanol content has been determined by quantitative analysis using gas chromatographic flame ionization (GC-FID) detection. A comparative study between direct injection of diluted wine and injection of distilled wine was performed. The distillation process does not affect methanol quantification in wines in proportions higher than 10%. While quantification performed on distilled samples gives more reliable results, a screening method for wine injection after a 1:5 water dilution could be employed. The proposed technique was found to be a compromise between the time consuming distillation process and direct wine injection. In the studied calibration range, the stability of the volatile compounds in the reference solution is concentration-dependent. The stability is higher in the less concentrated reference solution. To shorten the operation time, a stronger temperature ramp and carrier flow rate was employed. With these conditions, helium consumption and column thermal stress were increased. However, detection limits, calibration limits, and analytical method performances are not affected substantially by changing from normal to forced GC conditions. Statistical data evaluation were made using both ordinary (OLS) and bivariate least squares (BLS) calibration models. Further confirmation was obtained that limit of detection (LOD) values, calculated according to the 3sigma approach, are lower than the respective Hubaux-Vos (H-V) calculation method. H-V LOD depends upon background noise, calibration parameters and the number of reference standard solutions employed in producing the calibration curve. These remarks are confirmed by both calibration models used. 相似文献
5.
6.
Pietro Sabatino 《Archiv der Mathematik》2005,84(3):233-238
Let V be a reduced and irreducible hypersurface of degree k 3. In this paper we prove that if the singular locus of V consists of 2 ordinary double points, 3 ordinary triple points and if 2 + 43 < (k – 1)2, then any smooth surface contained in V is a complete intersection on V.Received: 7 January 2004 相似文献
7.
Andrea Sabatino Emanuele Penocchio Giulio Ragazzon Alberto Credi Diego Frezzato 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14479-14486
The first study in which stochastic simulations of a two‐component molecular machine are performed in the mass‐action regime is presented. This system is an autonomous molecular pump consisting of a photoactive axle that creates a directed flow of rings through it by exploiting light energy away from equilibrium. The investigation demonstrates that the pump can operate in two regimes, both experimentally accessible, in which light‐driven steps can be rate‐determining or not. The number of photons exploited by an individual molecular pump, as well as the precision of cycling and the overall efficiency, critically rely on the operating regime of the machine. This approach provides useful information not only to guide the chemical design of a self‐assembling molecular device with desired features, but also to elucidate the effect of the environment on its performance, thus facilitating its experimental investigation. 相似文献
8.
Stefania Garzoli Mijat Božović Anna Baldisserotto Manuela Sabatino Stefania Cesa Federico Pepi 《Natural product research》2018,32(11):1254-1259
A comprehensive study on essential oil samples of Foeniculum vulgare Miller from Tarquinia (Italy) is reported. A 24-h systematic steam distillation was performed on different harvested samples applying different extraction times. The GC-MS analysis of the residue outcome showed o-cymene, α-phellandrene, α-pinene and estragole as the major constituents. The predominance and continued presence of o-cymene makes this fennel oil a rather unique chemotype. An evident correlation between the antifungal activity and phenological stage is demonstrated. The most active fractions were particularly rich in estragole, as well as a significant amount of fenchone that possibly exerts some additive effect in the expression of overall antifungal potency. Pre-fruiting material produced oil particularly rich in o-cymene. With reference to the duration of the extraction, the maximum amount of oil was released within the first 3 h, whereas the reproductive phase material needed at least 6 h for the extraction. 相似文献
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10.
Ismaela Foltran Elisabetta Foresti Bruna Parma Piera Sabatino Norberto Roveri 《Macromolecular Symposia》2008,269(1):111-118
The possibility to prepare bioinspired collagen nanofibers by electrospinning from aqueous suspension of telopeptide-free collagen molecules avoiding both organic solvents and blends with any synthetic and natural polymers has been investigated. The results have highlighted the need for a basic atmosphere between the needle and the ground collector in order to increase the environmental pH during the collagen molecules self-assembly along the electrostatic force lines. Morphological, spectroscopic and calorimetric analyses carried out on the electrospun collagen nanofibers have opened the possibility to take advantage of this new approach in order to prepare an ideal biomimetic reinforcing component of new biomedical and surgical biomaterials. 相似文献