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991.
Lucia Tamborini Diego Romano Andrea Pinto Martina Contente Maria C. Iannuzzi Paola Conti Francesco Molinari 《Tetrahedron letters》2013
Cell-bound lipases of dry mycelium of Aspergillus oryzae were used in organic solvent for the resolution of racemic flurbiprofen by direct esterification with ethanol in a flow-chemistry reactor. Under flow conditions a significant reduction of the reaction time and an increase of the enantioselectivity were achieved compared to the batch mode. Moreover, the process was implemented by adding an in-line purification step integrated with the racemization of the unreacted flurbiprofen directly into a polymer-supported resin. 相似文献
992.
Stefania Costa Pier Paolo Giovannini Giancarlo Fantin Alessandro Medici Paola Pedrini 《Helvetica chimica acta》2013,96(6):1062-1071
The biotransformations of hyodeoxycholic acid with various Rhodococcus spp. are reported. Some strains (i.e., Rhodococcus zopfii, Rhodococcus ruber, and Rhodococcus aetherivorans) are able to partially degrade the side chain at C(17) to afford 6α‐hydroxy‐3‐oxo‐23,24‐dinor‐5β‐cholan‐22‐oic acid ( 2 ; 23%) and 6α‐hydroxy‐3‐oxo‐23,24‐dinorchol‐1,4‐dien‐22‐oic acid ( 3 ; 23–30%), together with two new 9,10‐secosteroids 4 and 5 (10–45%), still bearing the partial side chain at C(17) and adopting an intramolecular hemiacetal form. In addition, the 9,10‐secosteroid 5 showed an unprecedented C(4)‐hydroxylation. The new secosteroids were fully characterized by MS, IR, NMR, and 2D‐NMR analyses. 相似文献
993.
994.
995.
Maria Chiara Aversa Anna Barattucci Paola Bonaccorsi Placido Giannetto 《Phosphorus, sulfur, and silicon and the related elements》2013,188(5-6):1203-1208
Abstract L-cysteine is a stimulating starting product for the generation of transient sulfenic acids that add to suitable acceptors, allowing formation of sulfoxides showing a biologically active residue. For instance, N-(tert-butoxycarbonyl)-L-cysteine methyl ester furnished in few steps (R)-2-tert-butoxycarbonylamino-2-methoxycarbonyl-ethanesulfenic acid, which was readily converted into (R,S S )-(2-tert-butoxycarbonylamino-2-methoxycarbonyl-ethylsulfinyl)ethene, the methyl ester of Boc-protected nor-alliin. 相似文献
996.
Carlo Santambrogio Paola Sperandeo Riccardo Villa Frank Sobott Alessandra Polissi Rita Grandori 《Journal of the American Society for Mass Spectrometry》2013,24(10):1593-1602
LptA is a periplasmic protein involved in the transport of lipopolysaccharide (LPS) from the inner membrane (IM) to the outer membrane (OM) of Gram-negative bacteria. Growing evidence supports a model in which LptA assembles into oligomers, forming a physical bridge connecting IM and OM. This work investigates assembly and architecture of LptA oligomers. Circular dichroism and “native” electrospray-ionization ion-mobility mass spectrometry (ESI-IM-MS) are employed to test concentration dependence of LptA structural features and to analyze the morphology of higher-order aggregates. The results show that LptA progressively assembles into rod-like oligomers without fixed stoichiometry, and grows by an n + 1 mechanism up to at least the pentamer. The oligomerization process induces disorder-to-order transitions in the polypeptide chain. Comparison with crystallographic and computational data suggests that these conformational changes likely involve short disordered regions at the N- and C-termini of monomeric LptA. The protein response to thermal denaturation displays strong concentration dependence, indicating that oligomerization increases protein stability. LptA conformational stability can also be enhanced by in vitro LPS binding. The genesis of these fibrillar structures could be relevant for the correct transport of LPS across the bacterial periplasm. 相似文献
997.
Maria Carmela Sacchi Simona Losio Paola Stagnaro Stefano Menichetti Caterina Viglianisi 《大分子反应工程》2013,7(2):84-90
The aim of this work is to search for innovative solutions to avoid physical migration of the stabilizers from plastic films. New families of macromolecular additives bearing tuned amounts of a selected functionality were explored, in particular, novel random copolymers of ethylene with 1‐olefin co‐units bearing an efficient antioxidant and/or anti‐UV moiety covalently bonded to a mono‐ or disubstituted olefinic bond. Polyolefin blends containing the novel macromolecular additives showed higher degradation temperatures with respect to the neat matrix and its blends with 2,6‐t‐butyl‐4‐methoxyphenol (BHA). Aging tests showed that the novel antioxidants also constitute a protection against photo‐oxidation.
998.
Francesca Rigano Marianna Oteri Giuseppe Micalizzi Domenica Mangraviti Paola Dugo Luigi Mondello 《Journal of separation science》2020,43(9-10):1773-1780
In a previous article, Rigano et al. established a new linear retention index system for the identification of triacylglycerols by liquid chromatography methods only on the basis of the retention behavior and independently from many experimental parameters. In that work, a database of 209 compounds was built, but only 54 of them, typical of vegetable oils, were confirmed by mass spectrometry. The aim of the present research is to extend the applicability of the novel approach to more complex samples, such as fish lipid extracts, and assess the complementarity between mass spectromtery and retention information to achieve univocal identification. With this purpose, a new software was implemented to make the identification process easy and automatic as in gas chromatography‐mass spectrometry where the retention index filter is added in the spectral search to discriminate between compounds with similar mass spectrometry spectra. A total of 69 species were identified and, thanks to their baseline separation obtained by an ultra high performance liquid chromatography method, a semiquantification was also performed. The species under investigation were Dicentrarchus labrax, coming from aquaculture and the wild. Some differences in their native lipid composition were observed, probably related to a different diet. A major number of samples would be necessary to confirm such a preliminary finding. 相似文献
999.
Paola Baile Juan Medina Lorena Vidal Antonio Canals 《Journal of separation science》2020,43(9-10):1808-1816
A novel approach is presented to determine four bisphenols in water and urine samples, employing magnetic dispersive solid‐phase extraction combined with liquid chromatography and diode array detection. A modified zeolite‐based magnetic composite was used as an efficient sorbent, combining the advantages of magnetic materials with the remarkable properties of zeolites. A multivariate optimization design was employed to optimize some experimental factors affecting magnetic dispersive solid‐phase extraction. The method was evaluated under optimized conditions (i.e., amount of sorbent, 50 mg; sample pH, unadjusted; NaCl concentration, 1.25%; extraction and elution time, 2 min; eluent solvent, ethanol; eluent solvent volume, 400 µL), obtaining good linearity with correlation coefficients ranging between 0.995 and 0.999 (N = 5) (from 2 to 250 µg/L for bisphenol A, bisphenol AP, and bisphenol P and from 5 to 250 µg/L for bisphenol AF). Method repeatability was assessed obtaining coefficients of variation between 3 and 11% (n = 6). Finally, the method was applied to spiked real samples, obtaining for water samples relative recoveries between 83 and 105%, and for urine samples between 81 and 108% for bisphenol A, bisphenol AP, and bisphenol AF, and between 47 and 59% for bisphenol P. 相似文献
1000.
Paola Sassi Silvia Caponi Maria Ricci Assunta Morresi Harriëtte Oldenhof Willem F. Wolkers Daniele Fioretto 《Journal of Raman spectroscopy : JRS》2015,46(7):644-651
In this study, Fourier transform infrared, Raman and Brillouin spectroscopy have been used to study lipid phase behavior of hydrated as well as dried multilamellar l ‐α‐phosphatidylcholine assemblies, in order to compare limitations and potentials of the different techniques. Dried lipid samples have been studied in the presence and absence of trehalose, which is known to affect the phase behavior of these systems. The methylene C‐H stretching (2800–3000 cm−1) region in infrared (IR) and Raman spectra provided mutually consistent information on the rearrangement of lipid acyl chains occurring at the lipid melting temperature. IR spectra have a higher signal‐to‐noise ratio, thus permitting a more precise evaluation of the melting temperature. In the hydrated lipid samples, the C‐H stretching region in the Raman spectra is less affected by the contribution of water compared with that in the IR spectra. Raman spectra are particularly suitable to simultaneously study both lipid and water contributions allowing to distinguish ice from non‐frozen water below 0 °C. Brillouin light scattering was used to probe the collective dynamics, i.e. the propagation velocity and the attenuation of longitudinal acoustic modes in the lipid samples. Lipid phase transitions are evident from a change in the temperature behavior of the acoustic velocity. Moreover, a strong relaxation process with a characteristic time of 14 ps was observed in the sample dried without trehalose with a maximum in acoustic attenuation at about 45 °C, which likely reflects the rearrangement of acyl chains. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献