MDM2 is an E3 ubiquitin ligase which is crucial for the degradation and inhibition of the key tumor-suppressor protein p53. In this work, we explored the stability and the conformational features of the N-terminal region of MDM2 (N-MDM2), through which it binds to the p53 protein as well as other protein partners. The isolated domain possessed a native-like conformational stability in a narrow pH range (7.0 to 10.0), as shown by intrinsic and 8-anilinonapthalene-1-sulfonic acid (ANS) fluorescence, far-UV circular dichroism (CD), and size exclusion chromatography (SEC). Guanidinium chloride (GdmCl) denaturation followed by intrinsic and ANS fluorescence, far-UV CD and SEC at physiological pH, and differential scanning calorimetry (DSC) and thermo-fluorescence experiments showed that (i) the conformational stability of isolated N-MDM2 was very low; and (ii) unfolding occurred through the presence of several intermediates. The presence of a hierarchy in the unfolding intermediates was also evidenced through DSC and by simulating the unfolding process with the help of computational techniques based on constraint network analysis (CNA). We propose that the low stability of this protein is related to its inherent flexibility and its ability to interact with several molecular partners through different routes.

We report on the solvent-free synthesis of the perfluorinated analogue of the well-known breathing metal-organic framework MIL-53(Al), i.e., F4-MIL-53(Al), featuring tetrafluoroterephthalic acid as linker. The crystal structure was solved and refined from powder X-ray diffraction data and confirmed to be isoreticular with MIL-53(Al). As already reported for the MIL-53(Al) analogue, F4-MIL-53(Al) displays a peculiar breathing effect solely induced by the temperature; however, in the latter case the transition occurs with almost no hysteresis and fast kinetics. This unique behavior is reported here for the first time and experimentally demonstrated using differential scanning calorimetry and variable temperature X-ray diffraction.

A priori knowledge of the shelf life of energetic materials (EMs) is relevant due to its direct association with safety and functionality. This paper proposes a quick and reliable approach to predicting the shelf life of EMs whose thermal decomposition is an autocatalytic process once their failure threshold has been defined as a function of the limiting extent of conversion. This approach is based on the assumption of a kinetic law consistent with the autocatalytic behavior and on the subsequent extraction, via a suitable procedure of parameter identification, of the kinetics of thermal decomposition from differential scanning calorimetry (DSC) data gathered under dynamic conditions at three different heating rates. Its reliability is proven for picric acid (PA) through the comparison of kinetic predictions with evaluations of conversion obtained by using high performance liquid chromatography (HPLC) analysis for samples subjected to isothermal and non-isothermal accelerated aging tests, as well as for a sample of naturally aged material, i.e., PA, stored at room temperature for more than 10 years.

In order to meet the environmental needs caused by large plastic waste accumulation, in the road construction sector, an effort is being made to integrate plastic waste with the function of polymer into asphalt mixtures; with the purpose of improving the mechanical performance of the pavement layers. This study focuses on the effect of a recycled mixture of plastic waste on the chemical, thermal, and rheological properties of designed asphalt blends and on the identification of the most suitable composition blend to be proposed for making asphalt mixture through a dry modification method. Thermo-gravimetric analysis, differential scanning calorimetry, and Fourier transform infrared spectroscopy analysis were carried out to investigate the effect of various concentrations and dimensions of plastic waste (PW) on the neat binder (NB). The frequency sweep test and the multiple stress creep and recovery test were performed to analyze the viscoelastic behavior of the asphalt blends made up of PW in comparison with NB and a commercial modified bitumen (MB). It has been observed that the presence of various types of plastic materials having different melting temperatures does not allow a total melting of PW powder at the mixing temperatures. However, the addition of PW in the asphalt blend significantly improved the aging resistance without affecting the oxidation process of the plastic compound present in the asphalt blend. Furthermore, when the asphalt blend mixed with 20% PW by the weight of bitumen is adopted into the asphalt mixture as polymer, it improves the elasticity and strengthens the mixture better than the mixture containing MB.

In this paper, two medusa-like ACyDs, modified at the primary rim bearing four (ACyD4) and eight carbons (ACyD8) acyl chain length, and one bouquet-like CyD, modified at primary side with thiohexyl and at secondary one with oligoethylene moiety (SC6OH), were investigated for their ability to assemble in nanostructures or to form hybrid dipalmitoylphosphatidylcholine (DPPC)/ACyDs systems. The lipophilicity of these molecules and the different preparation methods used in this study (thin layer evaporation and nanoprecipitation method) significantly affect the aggregation behaviour in aqueous medium. Except for the shortest medusa-like ACyD4, the other ACyDs formed stable nanoaggregates for at least 45 days. The effect of ACyDs on the thermotropic behaviour of DPPC liposomes was also studied by differential scanning calorimetry analysis, thus elucidating their interaction with liposomes to afford hybrid liposome/ACyDs systems. The medusa-like ACyD4 cannot be used to realize nanosystems because it quickly aggregates or it induces a complete destabilization of the liposomes. At the highest concentration investigated (0.01 molar fraction), both ACyD8 and SC6OH interacted with DPPC liposomes, forming ACyD/DPPC or SC6OH/DPPC hybrid vesicular carriers.

The aim of this review is to summarize studies conducted by temperature-modulated differential scanning calorimetry (TMDSC) on polymer crystallization. This technique can provide several advantages for the analysis of polymers with respect to conventional differential scanning calorimetry. Crystallizations conducted by TMDSC in different experimental conditions are analysed and discussed, in order to illustrate the type of information that can be deduced. Isothermal and non-isothermal crystallizations upon heating and cooling are examined separately, together with the relevant mathematical treatments that allow the evolution of the crystalline, mobile amorphous and rigid amorphous fractions to be determined. The phenomena of`'reversing' and 'reversible` melting are explicated through the analysis of the thermal response of various semi-crystalline polymers to temperature modulation.

Composites based on isotactic polypropylene (iPP) modified with a sorbitol derivative (NX8000) and siloxane-silsesquioxane resin containing reactive phenyl groups (SiOPh) were prepared by melt extrusion. These iPP-based formulations were investigated to evaluate the influence of such additives on the crystallization behavior and morphology, as well as on thermal and mechanical properties. The addition of sorbitol fastens crystallization kinetics of iPP and leads to higher transparency of iPP films. Upon the incorporation of siloxane-silsesquioxane resin, no further effect on iPP crystallization kinetics is evidenced by calorimetry, optical microscopy, and X-ray diffraction analysis. Transparency of iPP-based composites is improved upon the addition of sorbitol, but decreased when SiOPh is added to the formulation. The composites are also stiffer, compared to neat polypropylene with a decreased elongation at break and increased Young's modulus values, with increasing amounts of fillers. The effect of the siloxane-silsesquioxane resin on properties of iPP/NX8000/SiOPh composites was explained taking into account compatibility of the components and morphology of the composites.

The thermal decomposition of 3,5-dinitro-4-methylbenzoic acid is studied by means of differential calorimetric techniques (DSC). Its autocatalytic behaviour has been highlighted and the decomposition process has been described considering the generalized expression of the Sestak-Berggren model. A new procedure for the optimization of the initiation parameter along with the other Arrhenius constants and kinetic exponents starting from the knowledge of the classic Sestak-Berggren model is illustrated. Encouraging results point out the validity of the approach which has been verified considering both a series of numerical and real experiments. (C) 2015 American Institute of Chemical Engineers

In this work we present our recent results on three ionic liquids (ILs), which share bis(trifluoromethanesulfonyl) imide (TFSI) as anion and have different pyrrolidinium based cations. By means of a combination of mechanical spectroscopy and thermal analysis, many of the physical processes occurring during cooling down from the liquid phase, can be studied. Depending both on the diverse cation and the different thermal history, crystallization from the melt or glass transition, cold-crystallization, solid-solid phase transitions and thermally activated processes are observed. In one of the ILs, which could be easily undercooled, a prominent thermally activated peak could be observed above the glass transition. The temperature dependence of the relaxation time is approximated by a Vogel-Fulcher-Tamman equation, as usual for fragile glass forming liquids, and the apparent activation energy of W = 0.36 eV with a pre-exponential factor of the relaxation time tau(0) = 1.7.10(-13)s were derived supposing jumps between asymmetrical potential wells. The kinetics of the crystallization processes have been studied in the framework of the Johnson-Mehl-Avrami-Kolmogorov theory and the Avrami parameters have been derived for both the crystallization from the melt and for the cold crystallization observed on heating.

Shape memory alloys (SMAs) are active materials able to recover large strains over several thermo-mechanical cycles. In the actuation field, this strain recovery is principally exploited on the mini and micro scales at which SMAs exhibit their highest power density with respect to common lightweight technologies. During the repetitive actuation of a SMA element, certain events occur: strain drift at the beginning of cyclic testing, the accumulation of plastic deformation, and strain stabilisation. In this study, these events as well as the overall mechanical response of an articulated NiTi element were monitored through calorimetry and scanning electron microscopy. Fatigue and cyclic stability were tested under different loads and under different aging conditions. In addition, the surface morphology was continuously observed via scanning electron microscopy to monitor crack growth and propagation during the fatigue test. Finally, before and after the fatigue test, samples were tested through calorimetry to investigate the overall microstructural homogeneity. Results confirm the high potential of the proposed geometry for the development of NiTi non-conventional active elements in the miniature actuation field.

A set of new copolymers is here reported in which the repeating units are connected each other through Cu(II) metal centers. The coordination link is based on the bis-chelating properties of salicylaldiminate groups of two different monomers. Due to their chemical structure, the two monomers afford, respectively, flexible and rigid repeating units in the metallocopolymers constitution upon coordination to copper centers. All the copolymers were soluble and easily processable. As shown by XRD analysis, rigid units' rich copolymers adopt a ribbon-like structure in solid state in which highly planar strands of polymer stack thanks to ?-? interactions, similarly to the polymer composed exclusively by rigid units. This behavior can be justified assuming the existence of a partial block character in copolymer constitution where long sequences of rigid units are alternated to sequences of flexible units. This assumption is supported also by DSC and UV-Vis analysis. © 2014 Wiley Periodicals, Inc.

This study studied the phase transformations occurring at different continuous cooling rates in an air hardening steel used in the rock-crushing industry. Samples of this steel were submitted for calorimetric testing using the differential scanning calorimetry (DSC) technique. In the experimental run, the samples were heated at the rate of 0.33 °C/s from 50 to 1050 °C and equilibrated at this temperature for 900 s, then cooled at seven different cooling rates between 0.05 and 0.5 °C/s. For all the cooling rates, the DSC traces of the samples showed a first exothermic peak at about 500 °C and for samples cooled at rates higher than 0.15 °C/s, a second exothermic peak at about 295 °C was observed. From the microstructural investigations carried out by light microscopy (LM) and scanning electron microscopy (SEM), it was observed that all the samples after DSC treatment were characterized by the presence of bainite. In the samples cooled at rates higher than 0.15 °C/s, martensite was also detected. Comparing the results of DSC and SEM, it was concluded that the first peak at 500 °C corresponds to the austenite -> bainite transformation, while the second peak at 295 °C corresponds to the austenite -> martensite transformation. The experimentally determined bainite and martensite start temperatures were compared to the values derived from a number of well-known empirical equations.

Poly(ethylene glycol) (PEG2000) polymers containing one or two amine residues are linked to a-lipoamino acids (LAA) to produce mono- and homo-disubstituted PEGLAA conjugates as new materials for the surface coating of colloidal drug carriers. Conjugates are characterized by FT-IR, 1H-NMR, and MALDITOF mass spectrometry. Differential scanning calorimetry studies are performed to assess the interaction of PEG2000LAAs with a biomembrane model (dipalmitoylphosphatidylcholine multilamellar liposomes). Whereas the parent PEGs affect only the superficial structure of the bilayers, the amphiphilic PEGLAA conjugates exert a modulated perturbing effect on the thermotropic profile of liposomes. A molar concentration between 5% and 10% is individuated as the more suitable to produce stable vesicles.

The article investigates the possibility of obtaining reliable information on the adiabatic behavior of thermally unstable substances based on the thermokinetic data collected by differential scanning calorimetric experiments. In particular, it is developed a novel numerical algorithm which allows the estimation of the adiabatic onset temperature. Theoretical results are verified considering the thermal decomposition of dicumyl peroxide carried out under different calorimetric conditions. Encouraging results point out that the procedures developed allow the assessment of adiabatic critical parameters that are very close to the values determined during the experim

Orthodontic treatment is strongly dependent on the loads developed by metal wires, and the choice of an orthodontic archwire should be based on its mechanical performance. The desire of both orthodontists and engineers would be to predict the mechanical behavior of archwires. To this aim, Gum Metal (Toyota Central R&L Labs., Inc.), TMA (ORMCO), 35°C Copper NiTi (SDS ORMCO), Thermalloy Plus (Rocky Mountain), Nitinol SE (3M Unitek), and NiTi (SDS ORMCO) were tested according to dynamic mechanical analysis and differential scanning calorimetry. A model was also developed to predict the elastic modulus of superelastic wires. Results from experimental tests have highlighted that superelastic wires are very sensitive to temperature variations occurring in the oral environment, while the proposed model seems to be reliable to predict the Young's modulus allowing to correlate calorimetric and mechanical data. Furthermore, Gum Metal wire behaves as an elastic material with a very low Young's modulus, and it can be particularly useful for the initial stage of orthodontic treatments. © The Author(s), 2010.

Crosslinked isotactic polypropylene (iPP) was prepared by reactive blending using dicumyl peroxide and active sulfur. The modified material was characterized by means of several techniques: dynamic mechanical thermal analysis, differential scanning calorimetry, Fourier transform infrared spectroscopy, and nuclear magnetic resonance (13C solid state NMR). Analysis of results using the above techniques confirms that, during the crosslinking process, new ethylenic chains are generated at expenses of the initially present iPP. Furthermore, a balance between the amount of missing iPP and the proportion of newly created polyethylene (PE) is observed. The newly formed PE is semicrystalline, having a degree of crystallinity of about 30%. The amorphous component of the generated PE is thought to contribute to the high impact strength of the crosslinked samples when compared to the unmodified iPP. In light of the results obtained by the different techniques, an attempt to describe the emerging structure of the new crosslinked iPP material is proposed.

The role played by Ca2+ ions in the interaction of the human islet amyloid polypeptide (hIAPP) with model membranes has been investigated by differential scanning calorimetry (DSC) and circular dichroism (CD) experiments. In particular, the interaction of hIAPP and its rat isoform (rIAPP) with zwitterionic dipalmitoyl-phosphatidylcholine (DPPC), negatively charged dipalmitoyl-phosphatidylserine (DPPS) vesicles and with a 3:1 Mixtures of them, has been studied in the presence of Ca2+ ions. The experiments have evidenced that amorphous, Soluble NAPP assemblies interact with the hydrophobic core of DPPC bilayers. Conversely, the presence of Ca2+ ions is necessary to activate a preferential interaction of hIAPP with the hydrophobic core of DPPS membranes. These findings support the hypothesis that an impaired cellular homeostasis of Ca2+ ions may promote the insertion of NAPP into the hydrophobic core of carrier vesicles which is thought to contribute to an eventual intracellular accumulation of beta-sheet rich hIAPP aggregates.

The aim of this paper is to promote calorimetry for olive oil authentication. It is our belief that the melting and freezing curves by DSC of olive oil and other edible oils could be correlated with quality, origin and storage history of the oil in a simple way, suitable for oil industry and market. Nucleation, crystallization kinetics and transition enthalpies of oil are indeed strongly dependent on molecular interactions, that is any change of oil acidic composition and minor components can be detected, as we have recently demonstrated. In particular, addition of low-cost oils to extra virgin olive oil (EVOO) and thermal and/or mechanical treatments (refinement, deodorization, filtration, etc.) of EVOO can be assessed by a first-sight analysis of the thermograms. Protocols to obtain reproducible DSC thermograms and experiments to understand the origin of the often-observed non-reproducibility, which prevented until now the use of calorimetry for oil authentication, are here described. An explanation of the melting curves even limited to the main features is a hard task owing to the polymorphism of the numerous triacylglycerols (TAG), the main component of the oil, the complexity of their mutual interactions and the effects of the minority components. To outline the level of this challenge we report: (i) the evidence that thermodynamic and kinetic processes overlap during heating of solid EVOOs and (ii) the melting curve of one pure TAG with its polymorphic transitions.

Fusion and solid-to-solid transitions of a homologous series of 12 linear alkane-alpha,omega-diamides H2NCO-(CH2)((n-2))-CONH2, where n = (2 to 12 and 14), were investigated by differential scanning calorimetry (d.s.c.). The temperatures of fusion of even terms decreased from T-fus approximate to 572 K to about 460 K, whereas those of odd terms remained substantially constant at about 450 K. Solid-to-solid transitions were also detected for oxamide, malonamide, succinamide, adipamide, suberamide, and dodecanediamide. Regular odd-even alternation was displayed by the temperature, enthalpy, and entropy of fusion values, terms with even number of carbon atoms showing higher values than odd terms.This behaviour was attributed to different crystal packing allowing consonance between hydrogen bonding and dispersive interaction in even terms, which are characterised by multilayer structure, whereas in odd terms a strained three-dimensional network results in looser packing. Parallel alternation of densities in solid alkane-alpha,omega-diamides supports this interpretation. Comparison was made with literature values for temperatures, enthalpies, and entropies of fusion of isoelectronic linear alkanes, dicarboxylic acids, and alkyldiamines. (c) 2006 Published by Elsevier Ltd.

SCN- binds to the charged amino group of lysines, inducing local changes in the electrostatic free energy of hi stones. We exploited this property to selectively perturb the histone-DNA interactions involved in the stabilization of eu and heterochromatin. Differential scanning calorimetry (DSC) was used as leading technique in combination with trypsin digestion that selectively cleaves the histone end domains. Euchromatin undergoes progressive destabilization with increasing KSCN concentration from 0 to 0.3 M. Trypsin digestion in the presence of 0.2 M KSCN show that the stability of the linker decreases as a consequence of the competitive binding of SCN- to the amino groups located in the C and N-terminal domain of H1 and H3, respectively; likewise, the release of the N-terminal domain of H4 induces an appreciable depression in both the temperature and enthalpy of melting of core particle DNA. Unfolding of heterochromatin requires, in addition to further cleavage of H4, extensive digestion of H2A and H2B, strongly suggesting that these histones stabilize the higher order structure by forming a protein network which extends throughout the heterochromatin domain.