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Ionic liquids (ILs) represent promising working fluids to be used in thermal energy storage (TES) technologies thanks to their peculiar properties, such as low volatility, high chemical stability, and high heat capacity. Here, we studied the thermal stability of the IL N-butyl-N-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate ([BmPyrr]FAP), a potential working fluid for TES applications. The IL was heated at 200 °C for up to 168 h either in the absence or in contact with steel, copper, and brass plates to simulate the conditions used in TES plants. High-resolution magic angle spinning nuclear magnetic resonance spectroscopy was found to be useful for the identification of the degradation products of both the cation and the anion, thanks to the acquisition of 1 H, 13 C, 31 P, and 19 F-based experiments. In addition, elemental analysis was performed on the thermally degraded samples by inductively coupled plasma optical emission spectroscopy and energy dispersive X-ray spectroscopy. Our analysis shows a significant degradation of the FAP anion upon heating for more than 4 h, even in the absence of the metal/alloy plates; on the other hand, the [BmPyrr] cation displays a remarkable stability also when heated in contact with steel and brass.

The angiogenin protein (ANG) is one of the most potent endogenous angiogenic factors. In this work we characterized by means of potentiometric, spectroscopic and voltammetric techniques, the copper complex species formed with peptide fragments derived from the N-terminal domain of the protein, encompassing the sequence 1-17 and having free amino, Ang1-17, or acetylated N-terminus group, AcAng1-17, so to explore the role of amino group in metal binding and cellular copper uptake. The obtained data show that amino group is the main copper anchoring site for Ang1-17. The affinity constant values, metal coordination geometry and complexes redox-potentials strongly depend, for both peptides, on the number of copper equivalents added. Confocal laser scanning microscope analysis on neuroblastoma cells showed that in the presence of one equivalent of copper ion, the free amino Ang1-17 increases cellular copper uptake while the acetylated AcAng1-17 strongly decreases the intracellular metal level. The activity of peptides was also compared to that of the protein normally present in the plasma (wtANG) as well as to the recombinant form (rANG) most commonly used in literature experiments. The two protein isoforms bind copper ions but with a different coordination environment. Confocal laser scanning microscope data showed that the wtANG induces a strong increase in intracellular copper compared to control while the rANG decreases the copper signal inside cells. These data demonstrate the relevance of copper complexes' geometry to modulate peptides' activity and show that wtANG, normally present in the plasma, can affect cellular copper uptake.

Polyvinyl butyral (PVB) is an amorphous polymer employed in many technological applications. In order to highlight the relationships between macroscopic properties and dynamics at a microscopic level, motions of the main-chain and of the propyl side-chains were investigated between T g - 288 °C and T g + 55 °C, with T g indicating the glass transition temperature. To this aim, a combination of solid state Nuclear Magnetic Resonance (NMR) methods was applied to two purposely synthesized PVB isotopomers: one fully protonated and the other perdeuterated on the side-chains. 1 H time domain NMR and 1 H field cycling NMR relaxometry experiments, performed across and above T g , revealed that the dynamics of the main-chain corresponds to the α-relaxation associated to the glass transition, which was previously characterized by dielectric spectroscopy. A faster secondary relaxation was observed for the first time and ascribed to side-chains. The geometry and rate of motions of the different groups in the side-chains were characterized below T g by 2 H NMR spectroscopy.

Dielectric Spectroscopy (DS) and 1 H Fast Field-Cycling (FFC) NMR relaxometry were applied for understanding the dynamic behavior of the amorphous ter-polymer poly(vinyl butyral) (PVB) across the glass transition temperature (T g = 70 °C by Differential Scanning Calorimetry). Above T g , main chain segmental motions (α relaxation) were detected and characterized using both DS and FFC NMR relaxometry. The correlation times extracted by the analysis of DS and FFC NMR relaxometry data agreed within a factor of three and showed a Vogel-Fulcher-Tammann temperature dependence, with an associated T g of 69 °C and a fragility of 155 for PVB glass. Below T g , a secondary process (β relaxation) was revealed by DS, and was ascribed to reorientations of the vinyl alcohol dipoles due to local twisting motions with an associated activation barrier of 11 kcal mol -1 . The β process was also found to contribute to 1 H NMR relaxation above T g .

Copper(ii) complexes with short peptides based on the second cell binding site of fibronectin, PHSFN and PHSEN, have been characterized by potentiometric, UV-vis, CD, EPR and NMR spectroscopic methods. The histidine imidazole nitrogen is the anchoring site for the metal ion binding. Thermodynamic and spectroscopic evidence is given that the side chain oxygen donor atom of glutamyl residue in Ac-PHSEN-NH2 is also involved in the binding up to physiological pH. To determine ligand exchange kinetic parameters after the imidazole nitrogen anchoring, proton relaxation enhancement NMR data have been collected for the two hydrogen atoms of the imidazole ring in the temperature range 293-315 K at pH 5.2 and globally treated within different kinetic models for ligand exchange. The best fitting model involves two steps. In the first one, which is slow, a water molecule disengages a carbonyl or a carboxylate group coordinated to the metal ion in the complex formed by PHSFN or PHSEN, respectively. This stage is one order of magnitude slower for PHSEN, due to entropic effects. In the second step, which is fast, the complex just formed exchanges with the ligand. In this step, no appreciable differences are found for the two cases examined.

Combined computational and experimental techniques were employed to investigate at the microscopic level the structural and dynamic properties of ferro- and ferricyanide ions in aqueous solution. The characterization of the structural patterns and multiscale dynamics taking place within the first solvation spheres in water and heavy water solvents was first achieved through extensive molecular dynamics simulations, performed with refined force fields, specifically parametrized for the cyanide ions under investigation. The information gained about the solute-solvent interactions is then validated through the successful comparison of computed and measured waiting-time-dependent 2D IR spectra. The vibrational patterns resulting from 2D IR measurements were rationalized in terms of the interaction between the ion and the neighboring water molecules described by simulation. It was found that, within the first solvation sphere, the stronger interactions of the solvent with the ferro species are responsible for a delay in the relaxation dynamics, which becomes more and more evident on longer time scales.

Conformational properties of small, flexible peptides are a matter of ongoing interest since they can be considered as models for unfolded proteins. However, the investigation of the conformations of small peptides is challenging as they are ensembles of rapidly interconverting conformers; moreover, the different methods used are prone to different approximations and errors. In order to obtain more reliable results, it is prudent to combine different techniques; here, molecular dynamics (MD) simulations together with nuclear magnetic resonance (NMR), Fourier transform IR (FTIR), polarized Raman, and vibrational circular dichroism (VCD) measurements were used to study the conformational propensity of phenylalanine in the tripeptides AFA and GFG, motivated by the relevance of phenylalanine for the self-aggregation of peptides. The results of this analysis indicate that the F residue predominantly populates the beta-strand (beta) and polyproline II (PPII) conformations in both AFA and GFG. However, while phenylalanine exhibits a propensity for beta-strand conformations in GFG (0.40 < or = beta population < or = 0.69 and 0.29 < or = PPII population < or = 0.42), the substitution of terminal glycines with alanine residues induces a higher population of PPII (0.31 < or = beta population < or = 0.50 and 0.37 < or = PPII population < or = 0.57).

The interaction of glycyl-phenylalanyl-glycine (GFG) with bilayers formed by cesium perfluorooctanoate (CsPFO) in water was investigated in the isotropic phase by means of 1H NMR and molecular dynamics (MD) simulations. Details on the preferential location of the different residues of GFG were obtained from selective variations of chemical shift with peptide concentration and of line width in the presence of the paramagnetic ion Mn2+. The analysis of 1H NMR spectra recorded at different concentrations and temperatures allowed the association constant and the enthalpy change upon binding to be evaluated. MD simulations highlighted the hydrogen bonds formed between the different GFG functional groups and the micelle. Both NMR and MD gave indications of high affinity of GFG with the micelle, with the N-terminal residue anchoring on the surface via hydrogen bonds with the micelle COO(-) groups.

We have used a combination of FTIR, VCD, ECD, Raman, and NMR spectroscopies to probe the solution conformations sampled by H-(AAKA)-OH by utilizing an excitonic coupling model and constraints imposed by the 3JCalphaHNH coupling constants of the central residues to simulate the amide I' profile of the IR, isotropic Raman, anisotropic Raman, and VCD spectra in terms of a mixture of three conformations, i.e., polyproline II, beta-strand and right-handed helical. The representative coordinates of the three conformations were obtained from published coil libraries. Alanine was found to exhibit PPII fractions of 0.60 or greater, mixed with smaller fractions of helices and beta-strand conformations. Lysine showed no clear conformational propensity in that it samples polyproline II, beta-strand, and helical conformations with comparable probability. This is at variance with results obtained earlier for ionized polylysine, which suggest a high polyproline II propensity. We reanalyzed previously investigated tetra- and trialanine by combining published vibrational spectroscopy data with 3JCalphaHNH coupling constants and obtained again blends dominated by PPII with smaller admixtures of beta-strand and right-handed helical conformations. The polyproline II propensity of alanine was found to be higher in tetraalanine than in trialanine. For all peptides investigated, our results rule out a substantial population of turn-like conformations. Our results are in excellent agreement with MD simulations on short alanine peptides by Gnanakaran and Garcia [(2003) J. Phys. Chem. B 107, 12555-12557] but at variance with multiple MD simulations particularly for the alanine dipeptide.

ClPbis11BB and Pbis11BB, two banana-shaped mesogens differing by a chlorine substituent on the central phenyl ring, show a nematic and a B2 phase, respectively. To obtain information on the structural features responsible for their different mesomorphic behavior, a study of the preferred conformations of these mesogens has been performed by NMR spectroscopy in two nematic media (Phase IV and ZLI1167), which should mimic the environment of the molecules in their own mesophases, avoiding problems of sample alignment by a magnetic field. To this aim, 2H NMR experiments have been performed on selectively deuterated isotopomers of ClPbis11BB and Pbis11BB and of two parent molecules, ClPbisB and PbisB, assumed as models in previous theoretical and experimental conformational studies. We found that only a limited number of conformations is compatible with experimental data, often very different from those inferred from theoretical calculations in vacuo, indicating a strong influence of the liquid crystalline environment on molecular conformation. No significant differences between chlorinated and non-chlorinated molecules were found, this suggesting that chlorine does not change the molecular conformational equilibrium, as previously proposed.

A hydrofluoric acid (HF)-treated soil sample was studied by 13C NMR spectroscopy. Cross polarization (CP) Magic Angle Spinning (MAS) 13C spectral editing and relative CP peak quantitation, obtained through variable-contact-time experiments, were used to aid the interpretation of the spectrum. The combination of these two types of experiment allowed to obtain a higher degree of detail on the composition of the sample with respect to a standard CP MAS experiment.

The (1)H NMR spectra of two isotopomers of tetraalanine deuterated on the two external methyl groups and on the two internal ones, respectively, were recorded in the lyotropic solvent cesium pentadecafluorooctanoate (CsPFO)/water. Eight dipolar couplings could be estimated from the spectra. The set of dipolar couplings was fitted assuming that one rigid conformer is present. Of the four major conformers considered, selected on the basis of theoretical calculations, the one characterized by the two couples of internal dihedral angles in the Ramachandran region of PPII resulted to be the only one to fit the set of couplings within experimental error. The data indicate that the molecule is oriented with the long molecular axis tilted with respect to the surface of the micelles formed by CsPFO.

In this study we show how deuterium magic-angle spinning NMR spectroscopy can be used to investigate the adsorption-desorption kinetics of molecules in solution at surface-liquid interfaces. An aqueous solution of deuterium-labeled tetraalanine is inserted in the pores of MCM-41 mesoporous material, and its 2H MAS NMR spectrum is measured as a function of temperature and fraction of filling of the pores. Prior to this study, the different types of water in MCM-41 are characterized as a function of water loading of the pores. Analysis of 2H MAS sideband line shapes enabled the determination of the adsorption and desorption rates and the activation energies of desorption.