46,872 research outputs found
Accurate first principles prediction of O-17 NMR parameters in SiO2: Assignment of the zeolite ferrierite spectrum
No full textO-17 NMR parameters, both the chemical shifts and the quadrupolar parameters, are calculated for SiO2 polymorphs using density functional theory with the generalized gradient-corrected PBE functional. The gauge including projector augmented wave (GIPAW) method (Pickard, C. J.; Mauri, F. Phys. Rev. B 2001, 63, 245101) ensures the reproduction of all electron results while using computationally efficient pseudopotentials. The use of plane-waves permits fully converged calculations to be performed on structures containing 144 atoms in the unit cell, without the need to resort to the cluster approximation. The calculated NMR parameters of cristobalite, quartz, coesite, and faujasite are in excellent agreement with experimental data. This demonstrates that density functional theory is able to reproduce with high accuracy the O-17 NMR parameters in SiO2 systems. This precision is used to assign the spectrum of the zeolite ferrierite. The data calculated for SiO2 are used to confirm that no simple correlation between the chemical shift and Cq NMR parameters and Si-O-Si angle exists, emphasizing the importance of predictive theories in this field
Synthesis of photoactivable probes for the study of glycosphingolipid-protein interactions
No full textSYNTHESIS OF PHOTOACTIVABLE PROBES FOR THE STUDY OF GLYCOSPHINGOLIPID-PROTEIN INTERACTIONS
Giuseppina Brasile,1 Federica Compostella,1 Laura Mauri,2Sandro Sonnino2 and Fiamma Ronchetti1
Dipartimento di Chimica, Biochimica e Biotecnologie per la Medicina, Università di Milano
1Via Saldini 50, 20133-Milano, Italy; 2Via Fratelli Cervi 93, 20190- Segrate (Milano), Italy
E-mail:[email protected]
It is widely accepted that glycosphingolipids (GSLs) at the level of the plasma membrane can affect the biological functions of protein molecules, such as cell surface receptors or transporters. The interactions between GSLs and proteins belonging to specific membrane microdomains, called lipid rafts, could be responsible for the modulation of the functional properties of membrane proteins participating in signal transduction. GSL-protein interactions can be investigated by cell photolabelling experiments using radioactive photoactivable GSLs, which yield, when illuminated, a very reactive intermediate that covalently binds to the molecules in the environment, i.e. proteins.1,2
In this context, we have designed a fatty acid probe with two nitrophenylazide photoactivable groups, one at position 2 and the other at the end of the acyl chain. The conjugation of the fatty acid to a radioactive sphingoglycolipid generates a species to be used for photolabelling experiments. In this way, the simultaneous identification of the proteins belonging to both the leaflets of the plasma membrane, the cytoplasmatic and the extracellular one, will be realized.
Herein we describe a general synthetic strategy to obtain not commercially available α,ω-diamino acids, the synthetic precursors of the labelled fatty acids, which we have applied to the synthesis of a C-18 derivative. Furthermore, it will be described the preparation of a photolabelled radioactive GSL as a case study.
1. Aureli M., Prioni S., Mauri L. Loberto N., Casellato R., Ciampa M.G., Chigorno V., Prinetti, A.; Sonnino S. J. Lipid Res. 2010, 51, 798-808
2. Mauri L., Prioni S., Loberto N., Chigorno V., Prinetti A., Sonnino S. Glycoconj. J. 2004, 20, 11-23
First-principles calculation of vibrational Raman spectra in large systems: Signature of small rings in crystalline SiO2
No full textWe present an approach for the efficient calculation of vibrational Raman intensities in periodic systems within density functional theory. The Raman intensities are computed from the second order derivative of the electronic density matrix with respect to a uniform electric field. In contrast to previous approaches, the computational effort required by our method for the evaluation of the intensities is negligible compared to that required for the calculation of vibrational frequencies. As a first application, we study the signature of 3- and 4-membered rings in the Raman spectra of several polymorphs of SiO2, including a zeolite (H-ZSM-18) having 102 atoms per unit cell
The Impact of the Loop Electrosurgical Excisional Procedure for Cervical Intraepithelial Lesions on Female Sexual Function
No full textIntroduction. Very limited knowledge exists concerning the impact of Loop Electrosurgical Excisional Procedure (LEEP) on female sexual function in women with cervical intraepithelial neoplasia Aim. To investigate sexual function in women who underwent LEEP for the treatment of cervical intraepithelial lesions, using a validated questionnaire (Female Sexual Function Index [FSFI]). Main Outcome Measures. FSFI questionnaire on six domains of female sexuality (desire, arousal, lubrication, orgasm, satisfaction, and pain). Methods. Consecutive sexually active women, who underwent LEEP for the treatment of cervical intraepithelial neoplasia were enrolled in this study. All women were asked to complete a copy of FSFI questionnaire, at the time of LEEP and after 6 months. We finally compared the results of the pre-LEEP questionnaire and the post-LEEP questionnaire for each patient. Results. A total of 67 sexually active women undergoing LEEP for the treatment of cervical intraepithelial lesions were enrolled. Nine of these patients (13.4%) completed only the questionnaire regarding their sexual function before LEEP; thus we did not include them for final analysis. In our study population, data showed a sexual function overall unchanged after LEEP; only the variable "desire" (sexual interest) became significantly worse (P = 0.02). Conclusions. LEEP for the treatment of cervical intraepithelial lesions doesn't affect women's sexuality, when compared with sexual function before surgery. In our study, all FSFI sexual function domains but desire, did not show significant change after LEEP. Serati M, Salvatore S, Cattoni E, Zanirato M, Mauri S, Siesto G, Cromi A, Ghezzi F, and Bolis P. The impact of the Loop Electrosurgical Excisional Procedure for cervical intraepithelial lesions on female sexual function. J Sex Med 2010;7:2267-2272
Prevention of arthritis by interleukin 10-producing B cells
No full textIn this study we have shown that activation of arthritogenic splenocytes with antigen and agonistic anti-CD40 gives raise to a B cell population that produce high levels of interleukin (IL)-10 and low levels of interferon (IFN)-{gamma}. Transfer of these B cells into DBA/1-TcR-ß-Tg mice, immunized with bovine collagen (CII) emulsified in complete Freund's adjuvant inhibited T helper type 1 differentiation, prevented arthritis development, and was also effective in ameliorating established disease. IL-10 is essential for the regulatory function of this subset of B cells, as the B cells population isolated from IL-10 knockout mice failed to mediate this protective function. Furthermore, B cells isolated from arthritogenic splenocytes treated in vitro with anti–IL-10/anti–IL-10R were unable to protect recipient mice from developing arthritis. Our results suggest a new role of a subset of B cells in controlling T cell differentiation and autoimmune disorders
Superconductivity in metal-coated graphene
No full textIn this work we explore, by first-principles density functional theory (DFT) calculations, the possibility of inducing electronphonon mediated superconductivity in a graphene sheet by doping its surface with alkaline metal adatoms. We demonstrate that, contrary to what could be naively believed, simple exfoliation to one layer of superconducting graphite intercalated compounds (GICs) does not necessarily lead to superconducting graphene, as it is the case in CaC6. On the contrary, it is meaningful to look for superconductivity in monolayers obtained by exfoliating non-superconducting GICs. In particular, we demonstrate that Li coating and double-coating of graphene leads to superconductivity in graphene with T-c that could be as large as 18 K. (C) 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhei
Erratum to: Effect of moderate red wine intake on cardiac prognosis after recent acute myocardial infarction of subjects with Type 2 diabetes mellitus (Diabetic Medicine, (2006), 23, 9, (974-981), 10.1111/j.1464-5491.2006.01886.x)
No full textIn an article by Marfella et al, the author name C. Saron is incorrect and should be listed as C. Sardu. Therefore the correct author list is: R. Marfella, F. Cacciapuoti, M. Siniscalchi, F. C. Sasso, F. Marchese, F. Cinone, E. Musacchio, M. A. Marfella, L. Ruggiero, G. Chiorazzo, D. Liberti, G. Chiorazzo, G. F. Nicoletti, C. Sardu, F. D'Andrea, C. Ammendola, M. Verza and L. Coppola.In an article by Marfella et al, the author name C. Saron is incorrect and should be listed as C. Sardu. Therefore the correct author list is: R. Marfella, F. Cacciapuoti, M. Siniscalchi, F. C. Sasso, F. Marchese, F. Cinone, E. Musacchio, M. A. Marfella, L. Ruggiero, G. Chiorazzo, D. Liberti, G. Chiorazzo, G. F. Nicoletti, C. Sardu, F. D'Andrea, C. Ammendola, M. Verza and L. Coppola
Phonon-mediated superconductivity in graphene by lithium deposition
No full textGraphene(1) is the physical realization of many fundamental concepts and
phenomena in solid-state physics(2). However, in the list of graphene's
many remarkable properties(3-6), superconductivity is notably absent. If
it were possible to find a way to induce superconductivity, it could
improve the performance and enable more efficient integration of a
variety of promising device concepts including nanoscale superconducting
quantum interference devices, single-electron superconductor-quantum dot
devices(7,8), nanometre-scale superconducting transistors(9) and
cryogenic solid-state coolers(10). To this end, we explore the
possibility of inducing superconductivity in a graphene sheet by doping
its surface with alkaline metal adatoms, in a manner analogous to which
superconductivity is induced in graphite intercalated compounds(11,12)
(GICs). As for GICs, we find that the electrical characteristics of
graphene are sensitive to the species of adatom used. However, contrary
to what happens in GICs, Li-covered graphene is superconducting at a
much higher temperature with respect to Ca-covered graphene
Heavy metal in sediments and bioaccumulation in the bivalve Corbula gibba in a drilling discharge area
No full textThe longterm bioavailability of heavy metals in sediments of a Northern Adriatic Sea shelf area affected by drilling mud and Cutting discharges was discussed. Levels of Mn, Cu, Cr, Zn and Pb in different geochemical phases of the sediment and in soft tissues of the bivalve Corbula gibba were recorded and the relationships between biological and geochemical metal investigated. Total metal content, acetic acid extractable-, exchangeable-, carbonate-, easily reducible-, moderately reducible-, oxidable- and residual-fractions were determined oil sediment samples. Corbula gibba was collected from wet sediments at the same times and sites, and the soft-tissue metal contents were determined. Correlations show that the fractions with greatest bioavailability are the exchangeable and carbonate for Cr and the exchangeable, carbonate, easily and moderately reducible fractions for Zn. Data also show a possible bioavailability of Pb only from the residual fraction, consisting of very resistant matter of more recent anthropogenic origin. Near the platform, total Mn content in sediments and in C. gibba tissues show a strong correlation suggesting that this organism is sensitive to variations of the Mn-oxi-hydroxides superficial film. No relationships were found between biological and sediment-bound Cu, however the discharged muds did not cause Cu enrichment. The metal fraction determined by weak acetic acid extraction at no point seems related to metal levels in Corbula gibba
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