1,720,978 research outputs found
Raman Spectroscopy of Insulin under Ambient and Extreme Conditions
Full text linkRaman spectroscopy has been used to investigate different conformational states of bovine pancreatic insulin: the native form
and several structurally modified states with different extent of denaturation induced by thermo-chemical treatment and by
applying very high pressure (up to 8 GPa) using a diamond anvil cell. High-pressure results confirm the peculiar strength-tovolume
compression of insulin and largely extend the pressure range of its structural stability (0–4.2 GPa). Above 4.2 GPa,
insulin undergoes an irreversible structural transition that, once pressure is released, leaves the sample in a new conformational
state. The protein secondary structure after the pressure treatment results to be somehow intermediate between the native and
the thermo-chemical fibrillar samples. The analysis of the pressure dependence of the Raman spectrum and of several specific
spectroscopic markers allows us to follow the path from the native to new pressure-denatured protein conformation. Morover a refolding studies has been conducted on fibrillar samples of insulin and lysozyme by means of ammonium based ionic liquids
A new CLT system for masonry construction refurbishment
No full textIn Italy about 50% of the building heritage has a masonry structure. The refurbishment of these buildings is a delicate issue. The complexity of the problem lies in the presence of a widespread panorama behind the category masonry construction because their characteristics depend on different techniques related to local traditions. The current conditions are often the result of a large number of subsequent interventions and of their natural decay. The complex scenery requires a diversified range of solutions in order to find an ‘ad hoc’ answer for each case. Nowadays energy efficiency requirements need a multidisciplinary approach, as structure safety oriented strategies are no longer sufficient. An environmental performance upgrade is needed. In this panorama there are some buildings with a so advanced decay that trying to preserve the whole building envelope could lead to lose it. The façadism allows the construction of a new building within the historic façades. This paper proposes a method for the refurbishment of these buildings based on the use of Cross Laminated Timber technology. The research focuses on the study of a standard process that ensures the highest building quality
Role of ionic liquids in protein refolding: native/fibrillar versus treated lysozyme
No full textSeveral ionic liquids (ILs) are known to revert aggregation processes and to improve the in vitro refolding of denatured/fibrillar proteins. Here, Raman spectroscopy is exploited to verify the refolding capability of several ammonium-based ILs and to identify the microscopic signatures of the structural rearrangements induced by the interaction of ILs with fibrillar lysozyme. We collected and carefully analyzed spectra from native, fibrillar and ILs-treated Several ionic liquids (ILs) are known to revert aggregation processes and to improve the in vitro refolding of denatured/fibrillar proteins. Here, Raman spectroscopy is exploited to verify the refolding capability of several ammonium-based ILs and to identify the microscopic signatures of the structural rearrangements induced by the interaction of ILs with fibrillar lysozyme. We collected and carefully analyzed spectra from native, fibrillar and ILs-treated fibrillar lysozyme to follow the microscopic process induced by ILs. These allowed us to identify different mechanisms of interaction depending on the length of the cation alkyl chain. A clear refolding effect was observed with EAN, as well as a tendency of the longer alkyl chain (PAN and BAN) of dissolving the fibril packing. A specific interaction mainly affecting the aromatic residues was identified for MEOAN (a long chain ILs with an ether group). The whole of the results, thus, provides new and detailed information on the ILs–protein interaction and shows Raman spectroscopy as a simple, reliable and effective diagnostic technique in this field.to follow the microscopic process induced by ILs. These allowed us to identify different mechanisms of interaction depending on the length of the cation alkyl chain. A clear refolding effect was observed with EAN, as well as a tendency of the longer alkyl chain (PAN and BAN) of dissolving the fibril packing. A specific interaction mainly affecting the aromatic residues was identified for MEOAN (a long chain ILs with an ether group). The whole of the results, thus, provides new and detailed information on the ILs–protein interaction and shows Raman spectroscopy as a simple, reliable and effective diagnostic technique in this field
Unravelling the structure of protic ionic liquids with theoretical and experimental methods: ethyl-, propyl- and butylammonium nitrate explored by raman spectroscopy and DFT calculations
No full textWe present an analysis of gas-phase structures of small clusters of n-alkylammonium nitrates (ethyl, propyl, and butyl) together with vibrational Raman spectroscopy of their respective liquid phases. The assignment and interpretation of the resonant frequencies have been performed by comparison with high-quality ab initio (DFT) computations. The theoretical spectra are in excellent agreement with the measured ones and allow the interpretation and assignment of almost all the spectral features. A careful analysis of the vibrational frequencies and of the electronic structure of the compounds has provided additional information on various structural features and on the rather complex hydrogen bonding network that exists in such compounds. A geometric structure of the short-range local arrangement in the bulk phases is also proposed. © 2012 American Chemical Society
Raman Spectroscopy in Ionic Liquids Under Variable Thermodynamic and Environmental Conditions.
No full textA prototypical ionic liquid explored by ab initio molecular dynamics and Raman spectroscopy
No full textWe present an analysis of the liquid and of a small isolated cluster of n-ethyl ammonium nitrate based on "first principles" molecular dynamics. We discover that the peculiar properties of ionic liquids make such compounds ideal candidates for such an analysis. We have been able to characterize some important features of the liquid structure and we have validated our simulations by comparing our findings with experimental vibrational spectra of the liquid phase. Theoretical spectra, which present a remarkable agreement with the measurements, besides the assignment of the main spectra features, allow an interpretation of the spectra at high frequencies where the vibrational motions involve the hydrogen-bonded atoms, thus providing a picture of the hydrogen bonding network that exists in such compounds. (C) 2013 AIP Publishing LLC
Evolution of past enamel technology and metal conservation issues: the case of two Byzantine style bindings
No full textThe results of a Raman spectroscopic study of the cloisonne' and basse-taille enamels, which beautify two Byzantine style bindings from the Marciana Library (Venice), namely the Lat. III, 111 and the MsGR.I.53 codexes, are presented in this work. The first binding dates back to the 13th century and was subject to an early restoration work in the 14th century, when new enamels substituted four originals. The second binding, from the 15th century, shows a lower number of enamels, all originals, and with a larger color palette. The white and yellow enamels of both codexes were successfully characterized and the red ones, where hematite was not used. Interestingly the white and yellow color of the 13th century enamels of the Lat. III, 111 codex has been obtained by an ancient technique of the glass technology, which was already obsolete in the 13th century, and is based on the use of calcium antimonate and Naples yellow. The white color in the other binding's enamels have been instead obtained by using cassiterite, according to the tradition of the time. Cassiterite was also mixed to Naples yellow in the enamels of the MsGR.I.53 codex, to change the yellow hue. The identification of agents determining some colors is instead uncertain or not feasible by Raman spectroscopy. The transparency of the 14th century enamels of the Lat. III, 111 codex has allowed the comparison of metal degradation below the enamels and in regions exposed to the atmosphere. Copyright (C) 2012 John Wiley & Sons, Ltd
Pathological Biominerals: Raman and Infrared Studies of Bioapatite Deposits in Human Heart Valves
No full textWe studied pathological bioapatite from patients undergoing valvular replacement due to severe aortic and mitral stenosis. Three different types of mineralized human cardiac valves were analyzed. We used infrared and Raman spectroscopy to infer the presence of the carbonate group and evaluate the carbonate substitution in bioapatite structure. The Raman spectra showed that the pathological bioapatite is a B-type "carbonate-apatite" (CO32- for PO43-) similar to the major mineralized products derived from normal biomineralization processes occurring in the human body. Fourier transform infrared spectra (FT-IR) confirmed the B-type carbonate substitution (CO32- for PO43-) and showed evidence for the partial replacement of [OH] by [CO3] (A-type substitution). The carbonate content of the samples inferred by the spectroscopic measurements is in good agreement with the range of values estimated for biological apatite. On the contrary, the crystal size of the pathological apatite estimated using the percentage area of the component at 1059 cm(-1) of the infrared spectrum is in the nanometer range and it is significantly smaller than the crystal size of normal mineralized tissues
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