1,721,070 research outputs found
IL CASTELLO DI VENERE A ERICE
No full textSperimentazione di metodologie innovative di rilievo e di restituzione grafica per la conoscenza di un sito, il castello di Venere a Erice, la cui complessa morfologia è caratterizzata dalla presenza di molteplici stratificazioni storiche
Exploring the stability of dimers through protein structure topology.
No full textProtein homodimers pose some intriguing questions about the relation between structure and stability. We approached the problem by means of a topological methodology based on protein contact networks. We correlated local interface descriptors with structure and energy global properties of the systems under analysis. We demonstrated that the graph energy, formerly applied to the analysis of unconjugated hydrocarbons structures, is the bridge between the topological and energetic description of protein complexes. This is a first step for the generation of a "protein structural formula", analogous to the molecular graphs in organic chemistry
Disclosing Allostery Through Protein Contact Networks
No full textProteins are located in the twilight zone between chemistry and biology, where a peculiar kind of complexity starts. Proteins are the smallest ‘devices’ showing a sensible adaptation to their environment by the production of appropriate behavior when facing a specific stimulus. This fact qualifies (from the ‘effector’ side) proteins as nanomachines working as catalysts, motors, or switches. However (from the sensor side), the need to single out the ‘specific stimulus’ out of thermal noise qualifies proteins as information processing devices. Allostery corresponds to the modification of the configuration (in a broad sense) of the protein molecule in response to a specific stimulus in a non-strictly local way, thereby connecting the sensor and effector sides of the nanomachine. This is why the ‘disclosing’ of allostery phenomenon is at the very heart of protein function; in this chapter, we will demonstrate how a network-based representation of protein structure in terms of nodes (aminoacid residues) and edges (effective contacts between residues) is the natural language for getting rid of allosteric phenomena and, more in general, of protein structure/function relationships
Dynamics of trypsin under pressure
No full textThe pressure dependence of the dynamics of a monomeric protein has been studied by quasielastic neutron scattering. The EISF shows a reduction in the volume sampled by the protons in going from 1 to 900 atm. A slight decrease of the quasielastic broadening with pressure is also observed. (C) 2000 Elsevier Science B.V. All rights reserved
Modellazione parametrica per la ricostruzione delle strutture di copertura del c.d. Tempio di Venere a Baia
No full textSi presentano a seguire i primi risultati relativi alla ricostruzione parametrico-informativa delle strutture di copertura del c.d. Tempio di Venere a Baia e delle relative particolari strutture annesse sul versante sudoccidentale sulla base della documentazione bibliografica e le acquisizioni digitali effettuate in situ. / We present in the following the first results of the parametric-informative reconstruction of the roof structures of the so-called Temple of Venus at Baia and of the peculiar adjoining structures located on the SW side, carried out on the basis of bibliographic documentation and digital acquisitions made in situ
The recovery of dipolar relaxation times from fluorescence decays as a tool to probe local dynamics in single tryptophan proteins
No full textConformation and stability of myoglobin in dilute and crowded organically modified media
No full textIn this study we investigated the structural features of myoglobin, a heme-containing enzyme, upon encapsulation in tetramethoxysilane and organically modified sol-gel glasses. Absorption and fluorescence spectroscopy have been employed to study the conformational changes of the protein embedded in these solid matrices. The slight decrease of the heme absorption value during gelation in all the different glasses indicates an irreversible change in the heme molar absorptivity consistent with the partial loss of native local structure caused by the changes in the hydrophobic forces. In particular, inorganic, aminopropyl-trimethoxysilane- and 3-glycidyloxypropyl-trimethoxysilane-doped monoliths showed blue-shifted, broadened absorbance and red-shifted fluorescence spectra with respect to those for dissolved native myoglobin (Mb), confirming the presence of Mb with altered heme environment in consequence of a partial loss of native structure. 3-trimethoxysilyl-propyl methacrylate-doped solutions and monoliths showed the absorbance spectra reduced in intensity but similar to that for native Mb while the fluorescence spectra were found to be blue-shifted, narrowed, and increased in intensity. The similarity between the fluorescence spectra for the bulk and the corresponding solution showed that the wrapping micelle formed by 3-trimethoxysilyl-propyl methacrylate is not dependent by the surrounding environment (dilute solution or crowded medium). In order to better investigate the effects of silica glasses on myoglobin stability, unfolding experiments of the protein, in solution or entrapped, were also performed in presence of guanidinium hydrochloride. Our results showed that the inorganic matrix protects myoglobin upon unfolding. Organic functionalities had different effects on the protein structure and its stability depending on if they are dissolved in dilute solutions or structured in a confining and crowed system. Particularly interesting was the case of 3-trimethoxysilyl-propyl methacrylate-doped samples. In this case the protein (dissolved and embedded) resulted to be protected by the action of denaturant agents. © 2004 Elsevier B.V. All rights reserved
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Resolution of the heterogeneous fluorescence in multi-tryptophan proteins: Ascorbate oxidase
Full text linkAscorbate oxidase is a copper-containing enzyme which catalyzes a redox reaction between vitamin C and molecular oxygen. The protein, which shows a complex tertiary structure, is an homodimer of monomers, each containing three domains and 14 tryptophan residues. Recently, we have demonstrated by spectroscopic and ultracentrifugation techniques the existence of a stable dimeric intermediate along the unfolding pathway of this enzyme [Mei, G., Di Venere, A., Buganza, M., Vecchini, P., Rosato, N. and Finazzi Agro, A. (1997) Biochemistry 36, 10917-10922]. In this study, the steady-state and dynamic fluorescence features of ascorbate oxidase have been exploited in order to find a way of monitoring the individual subsystems of the protein. The fluorescence intensity and anisotropy upon excitation at 295 nm are extremely sensitive functions of the emission wavelength, indicating a great heterogeneity of the system. The emission decay collected through a cut-off filter can be analyzed in terms of two continuous distributions of lifetimes. Using a monochromator in emission or an optical multichannel analyzer, the two distributions may be attributed to distinct components of the fluorescence spectrum. Differential quenching by cesium chloride also confirmed that the several tryptophan residues present in the protein structure may be grouped into two main classes, each with a different environment. Once the complex fluorescence decay of ascorbate oxidase was analyzed and resolved, a comparison with the crystallographic data allowed a first, approximate attribution of the protein spectroscopic properties to some of the tryptophan residues. This might provide a powerful tool of investigation about the role of definite segments of the protein in its three-dimensional structure and catalytic activity. Furthermore, the methodology set up for ascorbate oxidase can be usually extended to other multitryptophan proteins
Characterization of lipoxygenases interaction with model membranes: a fluorescence spectroscopy approach
No full textThe endocannabinoid 2-arachidonoylglicerol decreases calcium induced cytochrome c release from liver mitochondria
No full text2-Arachidonoylglicerol (2-AG) is an endocannabinoid that mimics the pharmacological effects of Delta(9) tetrahydrocannabinol, the psychoactive component of the plant Cannabis sativa. It is present in many mammalian tissues, such as brain, liver, spleen, heart and kidney, where it exerts different biological effects either receptor mediated or independently of receptor activation. This work analyzes the effects of 2-AG on liver mitochondrial functions. It is shown that 2-AG causes a relevant decrease of calcium induced cyclosporine A sensitive cytochrome c release from mitochondria, a process representing an early event of the apoptotic program. Cyclosporin sensitive matrix swelling and ROS production measured under the same conditions are, on the contrary, almost unaffected or even enhanced, respectively, by 2-AG. Furthemore, 2-AG is found to stimulate resting state succinate oxidase activity and to inhibit oligomycin sensitive FoF1 ATP synthase activity. All these effects are apparently associated with 2-AG dependent alteration in the fluidity of the mitochondrial membranes, which was measured as generalized polarization of laurdan fluorescence
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