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We present a high-pressure investigation of the semiconductor-to-metal transition in MoS2 and WS2 carried out by synchrotron-based far-infrared spectroscopy, to reconcile the controversial estimates of the metallization pressure found in the literature and gain new insight into the mechanisms ruling this electronic transition. Two spectral descriptors are found indicative of the onset of metallicity and of the origin of the free carriers in the metallic state: the absorbance spectral weight, whose abrupt increase defines the metallization pressure threshold, and the asymmetric lineshape of the E1u peak, whose pressure evolution, interpreted within the Fano model, suggests the electrons in the metallic state originate from n-type doping levels. Combining our results with those reported in the literature, we hypothesize a two-step mechanism is at work in the metallization process, in which the pressure-induced hybridization between doping and conduction band states drives an early metallic behaviour, while the band-gap closes at higher pressures., Comment: 8 pages, 3 figures

During the Lower Paleolithic, the interaction between hominins and elephants through the medium of lithic tools is testified by numerous sites in Africa, Europe, and Asia. This interaction ensured hominins a large source of food and of knappable raw material, bone. The availability of the huge package of resources represented by these animals had a deep impact on hominins behavior and their strategies of exploitation of the landscape. This article, for the first time, documents this behavior with a spatial and chronological viewpoint. At the Late Lower Paleolithic site of La Polledrara di Cecanibbio (Rome), the outstanding in situ find of a quite entire carcass of Palaeoloxodon antiquus surrounded by lithic tools of small dimensions allowed us to explore the relation between the elephant, fatally entrapped in muddy sediments, and the hominins that exploited its carcass with their lithic toolkit. The application of an integrated approach including technology, refitting, use-wear, residues, and spatial analyses to the study of the small tools allowed us to unveil the activities carried out around the elephant in a timeline. As a result, hominins exploited the carcass for meat and fat possibly in more than one time and selected the area of the carcass as an atelier to knap and possibly cache their lithic products for future use. These data introduce the intriguing suggestion that the carcass was, besides a source of food and raw material, also a landmark for humans in the landscape.

Microplastics (MPs) have recently emerged as a new major and ubiquitous environmental pollutant with still undefined, yet potentially high risks for human health and ecosystems. This has prompted growing public concern along with an increasing number of scientific studies. In particular, recent research has highlighted the need for a standardized methodology to monitor microplastics in different media, particularly in water. This study reports on the use of a new particle counter for the quantitative detection of MPs in water samples based on real-time analysis of fluorescence emissions. The instrument was calibrated using two types of plastic particles, i.e., polyvinyl chloride and high-density polyethylene, selected as examples of high- and low-density plastics, respectively. Specific solvents were used to match the different plastic densities. Measurements were also carried out on particles obtained from wastewater samples collected at the inlet and outlet of specific units of a municipal wastewater treatment plant after sieving, filtering, digestion with hydrogen peroxide to remove degradable organic matter and resuspension in the solvents employed during the calibration step. A Fourier transform infrared spectroscopy analysis performed on the same wastewater samples confirmed the presence of MPs, and, in particular, of polyethylene, in some of the samples in which the highest concentrations were measured applying the proposed method. Therefore, the novel particle counter described in this paper could represent a promising method to quantitatively measure MP concentrations in water samples.

Tholu Bommalu are typical leather puppets of the traditional Indian shadow theatre. Two of these objects are part of a collection in the International Puppets Museum “Antonio Pasqualino” (Palermo, Sicily, Italy), which can count on one hundred-seventy-three of artifacts. These Indian puppets were investigated to obtain information related to the use of dyes for their manufacturing through a multi-technical approach exploiting the combination of highly sensitive spectroscopic techniques. Wet cotton stubbons were used to entrap small particles of dyes on the fibers from the art objects for the consequent analyses. Visible Light Micro-Reflectance spectroscopy was employed for the preliminary identification of the molecular class of dyes directly on the swabs, while Surface Enhanced Raman Scattering allowed the identification of the specific dye. Several synthetic dyes belonging to different typologies of coloring compounds were identified. The study resulted in an interesting overview of dyes used in recent Tholu Bommalata manufacturing through the combination of micro-invasive techniques directly on the sampling substrate.

The growing need for new and reliable surface sensing methods is arousing interest in the electromagnetic excitations of ultrathin films, i.e., to generate electromagnetic field distributions that resonantly interact with the most significant quasi-particles of condensed matter. In such a context, Bloch surface waves turned out to be a valid alternative to surface plasmon polaritons to implement high-sensitivity sensors in the visible spectral range. Only in the last few years, however, has their use been extended to infrared wavelengths, which represent a powerful tool for detecting and recognizing molecular species and crystalline structures. In this work, we demonstrate, by means of high-resolution reflectivity measurements, that a one-dimensional photonic crystal can sustain Bloch surface waves in the infrared spectral range from room temperature down to 10 K. To the best of our knowledge, this is the first demonstration of infrared Bloch surface waves at cryogenic temperatures. Furthermore, by exploiting the enhancement of the surface state and the high brilliance of infrared synchrotron radiation, we demonstrate that the proposed BSW-based sensor has a sensitivity on the order of 2.9 cm

Amyloid-beta peptide (A beta) aggregates are known to be correlated with pathological neurodegenerative diseases. The fibril formation process of such peptides in solution is influenced by several factors, such as the ionic strength of the buffer, concentration, pH, and presence of other molecules, just to mention a few. In this paper, we report a detailed analysis of in vitro A beta 42 fibril formation in the presence of cortisol at different relative concentrations. The thioflavin T fluorescence assay allowed us to monitor the fibril formation kinetics, while a morphological characterization of the aggregates was obtained by atomic force microscopy. Moreover, infrared absorption spectroscopy was exploited to investigate the secondary structure changes along the fibril formation path. Molecular dynamics calculations allowed us to understand the intermolecular interactions with cortisol. The combined results demonstrated the influence of cortisol on the fibril formation process: indeed, at cortisol-A beta 42 concentration ratio (rho) close to 0.1 a faster organization of A beta 42 fragments into fibrils is promoted, while for rho = 1 the formation of fibrils is completely inhibited. De två första författarna delar förstaförfattarskapet.

Extrinsic chemiluminescence can be an efficient tool for determining pesticides and fungicides, which do not possess any intrinsic fluorescent signal. On this basis, (3-aminopropyl) trimethoxysilane (APTMS)-coated ZnO (APTMS@ZnO) was synthesized and tested as an extrinsic probe for the fungicide penconazole. Several synthetic routes were probed using either a one-pot or two-steps method, in order to ensure both a green synthetic pathway and a good signal variation for the penconazole concentration. The synthesized samples were characterized using X-ray diffraction (XRD), infrared (IR), Raman and ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM) imaging and associated energy-dispersive X-ray (EDX) analysis. The average size of the synthesized ZnO nanoparticles (NPs) is 54 ± 10 nm, in line with previous preparations. Of all the samples, those synthesized in two steps, at temperatures ranging from room temperature (RT) to a maximum of 40 °C, using water solvent (G-APTMG@ZnO), appeared to be composed of nanoparticles, homogeneously coated with APTMS. Chemiluminescence tests of G-APTMG@ZnO, in the penconazole concentration range 0.7–1.7 ppm resulted in a quenching of the native signal between 6% and 19% with a good linear response, thus indicating a green pathway for detecting the contaminant. The estimated detection limit (LOD) is 0.1 ± 0.01 ppm.

Telomeric G-quadruplexes (G4s) are promising targets in the design and development of anticancer drugs. Their actual topology depends on several factors, resulting in structural polymorphism. In this study, we investigate how the fast dynamics of the telomeric sequence AG3(TTAG3)3 (Tel22) depends on the conformation. By using Fourier transform Infrared spectroscopy, we show that, in the hydrated powder state, Tel22 adopts parallel and mixed antiparallel/parallel topologies in the presence of K+ and Na+ ions, respectively. These conformational differences are reflected in the reduced mobility of Tel22 in Na+ environment in the sub-nanosecond timescale, as probed by elastic incoherent neutron scattering. These findings are consistent with the G4 antiparallel conformation being more stable than the parallel one, possibly due to the presence of ordered hydration water networks. In addition, we study the effect of Tel22 complexation with BRACO19 ligand. Despite the quite similar conformation in the complexed and uncomplexed state, the fast dynamics of Tel22-BRACO19 is enhanced compared to that of Tel22 alone, independently of the ions. We ascribe this effect to the preferential binding of water molecules to Tel22 against the ligand. The present results suggest that the effect of polymorphism and complexation on the G4 fast dynamics is mediated by hydration water.

We report on the design, fabrication, and spectroscopic characterization of a 1D Photonic Cristal (1DPC) sustaining Bloch Surface Waves (BSWs) in the mid-infrared. The reported all-dielectric 1DPC structure shows potential for label-free biosensing applications to medical diagnostics.

In the last decades, the working methods of late medieval illuminators have been widely discussed by art historians and codicologists. Non-invasive analyses are able to characterise the painting methods of illuminators as well as investigate artistic collaborations among them. The aim of this study was to characterise the painting palettes and techniques of different artists who illuminated two leaves from an early fourteenth century manuscript. The analyses were carried out with non-invasive and portable techniques such as Energy Dispersive X-ray Fluorescence (ED-XRF) spectrometry, Fiber Optics Reflectance Spectroscopy (FORS) and Raman spectroscopy. The paper highlights the differences among three rich and varied palettes and examines the pigments ultramarine, azurite, verdigris, earths, orpiment, red lead, vermillion, lead white, yellow lake, indigo, brazilwood and lac, used independently or in mixtures. We have demonstrated the effectiveness of non-invasive analyses as a tool to differentiate hands of artists who have worked on the same page. Furthermore, the comparison with analyses carried out on leaves attributed to the workshop of Pacino di Bonaguida allows to investigate in-depth the production of the main illuminators active in Florence at the dawn of the Renaissance.

Amorphous SiO2 thin films are one of the two components of the highly reflective mirror coatings of gravitational-wave detectors. For this study, layers of amorphous SiO2 on crystalline Si substrates were produced by ion-beam sputtering (IBS), using accelerated neutralized argon ions as sputtering particles, as is the case for the actual mirror coatings of gravitational-wave detectors. The aim of this study is to investigate the possible presence of various defects in the materials in order to improve the coating quality. We provide evidence that, due to the synthesis method, about 0.2 wt.% of Ar is present in the coatings, and it can be released by means of thermal treatments, starting around 400 °C. The time and temperature to obtain the total release of Ar increases with the coating thickness; for a thickness of 100 nm, all argon is released below 600 °C, while an isotherm of one hour at 900 °C is necessary for a coating 5 μm thick. Besides the Ar atoms left from the synthesis, other defects, such as Si clusters and silicon dangling bonds, are present in the coatings. The concentration of both of them is strongly reduced by thermal treatments either in vacuum or in air. The overall thickness of the coating is slightly increased after thermal treatments, as witnessed by the change of the period of interference fringes.

International audience; We investigate the effects of thermal treatments in vacuum or air on amorphous Ta 2 O 5 deposited on crystalline Si by Ion Beam Sputtering, mimicking the coatings of the mirrors of the gravitational-wave revealers of the Advanced Virgo and Advanced LIGO detectors. Argon is present in the whole thickness of the coating, likely introduced during the synthesis, and it can be released above 200°C in vacuum, while less discharge of Ar is detected during heating in air. Formation of sub-stoichiometric Ta oxides is evidenced in the surface layers, after in-vacuum annealing. The macroscopic structure of the samples is not affected by the thermal treatments. However, the length of the interference fringes, due to the coating, decreases after thermal treatments both in air and in vacuum, suggesting an increase of the Ta 2 O 5 thickness of ~1-2%, caused by an increase of the volume of the pores present in the structure.

In the current climate of food security, quality aspects of legume crops have primary market economic and health impact. Legume proteins and peptides have been discovered to have a role far beyond supplying amino acids for growth and maintenance of body tissues. Several proteins (enzymatic inhibitors, lectins, storage globulins) and peptides derived from them (lunasin, hydrophobic peptides) have shown anticarcinogenic, hypocholesterolemic, glucose-lowering, antioxidant, antimicrobial, and immunostimulant properties. Further understanding of how structural features of legume proteins affect in vivo digestion and production of bioactive sequences represents a key step in the valorization of nutraceutical potentiality of legume proteins and peptides derived from them. In this work, the relationship between structure and bioavailability of protein and peptides are reviewed and discussed.

The reliability in using chemical techniques for the characterization of organic and inorganic ancient residues has been proved by several scientific works in the archeological literature. Among the different proposed approaches, Fourier Transform InfraRed Spectroscopy (FTIR) demonstrated to be a valuable method to detect and interpret the use-related residues entrapped in lithic chipped stone tools after their use. However, FTIR is affected by some restrictions that could be partially overcome thorough a statistical treatment of its results. With this contribution, we propose a methodological study based on Principal Component Analysis (PCA) as a statistical method to analyze infrared spectra collected on experimental residues on stone tools used to process vegetal materials. Here we show the ability of the PCA multivariate analysis to cluster samples with similar characteristics and to mine subtle spectral differences. According to our results, we proved the technique to be very suitable to discriminate vegetal materials, especially if belonging to herbaceous plants and underground storage organs (USOs) species where the likelihood to be recognized account for about 86% of possibilities. Our results demonstrate how the application of statistical methods such as PCA may amplify the interpretative capacity of the InfraRed Spectroscopy, especially when applied to archeological materials. Moreover, we contribute to build a representative spectral database of vegetal residues useful for scholars dealing with infrared measurements focused on the interpretation of the function of the archaeological artefacts.

Deep Eutectic Solvents (DESs) are gathering growing attention as sustainable solvents in different fields ranging from synthesis to electrochemical devices. Albeit DES are widely employed, the fundamental knowledge on their interspecies relations is still partial. Understanding the chemistry of this class of green solvent is an essential step to further tune their properties. In this study, we report a detailed experimental and theoretical investigation of two choline-chloride glycerol mixtures using electrochemical, spectroscopic (Raman/Far Infrared), diffraction (X-ray) and molecular simulation methods. Remarkably different Far-infrared spectra have been surprisingly collected for the two mixtures. Differences are attributed to the deconstruction of the extended hydrogen bond network characteristic of pure glycerol and of the 1:2 mixture and absent in the glycerol-richer mixture 1:3. From the analysis of X-ray profiles, that are very well reproduced by molecular dynamics, it was found that the lack of the glycerol H-bond interactions in the glycerol-richer mixture (Ch:Gly 1:3) can be attributed to the establishment of a full coordination shell of polyalcohol molecules around the chloride anion. In the 1:2 composition the coordination is probably defective, as signaled by the FIR spectrum that significantly maintains the features observed for the precursor glycerol, and the chloride stabilization is ensured by interaction with both choline hydroxyl and electrostatic interactions.

Recent efforts in the field of surface-enhanced spectroscopies have focused on the paradigm of "superchirality", entailing the engineering of the local electromagnetic fields to boost the enantiospecific interaction between light and chiral molecules. In this framework, approaches based on both metallic and dielectric nanostructures have been proposed and have also recently been extended to vibrational circular dichroism in the mid-infrared. In this work, we design, fabricate, and characterize a lattice of chiral plasmonic slits featuring enhanced chiral fields in the mid-infrared. We exploit collective lattice resonances to further enhance the local intensity and to generate sharp features in the circular dichroism spectra of the platform. Such features are ideally suited to test the superchiral coupling with the vibrational resonances of chiral molecules.

We present SEM, ThT fluorescence and circular dichroism (CD) data of amyloidogenic aggregates of cytochrome c (cyt c).This protein is of outmost relevance in many biochemical processes, such as respiratory chain in mitochondria and cells apoptosis. The present data focus on polymorphism of the protein aggregates obtained at the isoelectric point (IP) and by changing the environmental pH above and below the IP, the protein concentration and the base. The SEM images provide evidence for a large variety of structures, depending on the pH and on protein concentration: mature amyloid fibrils and overstructured platelets are distinguishable in the aggregates below IP, and relatively high cyt c concentration, whereas inhomogeneous amyloid formations are observed above it. At pH 10, i.e. close to IP, only characteristic protein particulates at the micrometric scale are observed. SEM and Fluorescence data have been acquired in dried drops of protein solution, prepared in different bases: TRIS-HCl, at the different pH values, or NaOH (pH 13). Along with this, at relatively low cyt c concentration compact layered structures are visible below the IP, though still made of a thin fibrils reticulate, whereas above the IP, also at low cyt c concentration, granulates structures are present, merging into compact layer, alongside with platelets and mature fibers. These areas are characterized by diffuse ThT-fluorescence and typical fibrils. The loss of the predominant alpha helix secondary structure was verified by CD spectra. Besides the intrinsic scientific relevance, this data collection provides a set of images useful for spectroscopists to discriminate among different morphologic protein formations and suggests pathways for the achievement of different kinds of cytochrome c aggregates. These data are add-ons of the paper published in the International Journal of Biomacromolecules, 138 (2019) 106–115, https://doi.org/10.1016/j.ijbiomac.2019.07.060.

A new optical setup is described that allows the reflectivity at grazing incidence to be measured, including ultrathin films and two-dimensional electron systems (2DES) down to liquid-helium temperatures, by exploiting the Berreman effect and the high brilliance of infrared synchrotron radiation. This apparatus is well adapted to detect the absorption of a 2DES of nanometric thickness, namely that which forms spontaneously at the interface between a thin film of LaAlO3 and its SrTiO3 substrate, and to determine its Drude parameters.

Cytochrome c is a metalloprotein with primary physiological functions in the respiratory chain and in the regulation of cell death signals. Investigating the mechanisms leading to cytochrome c fibril formation is of primary importance for understanding its misfunctioning and, in a wider perspective, for its technologic applications in the field of bio-nanoscience. In this work, we analyzed the morphology and the spectroscopic properties of cytochrome c aggregates, combining the outcomes from electron microscopy, fluorescence, infrared and Raman spectroscopies and making use of statistical tools for the data analysis. The morphology scenario is quite complex, as it points out the presence of aggregates in the shape of platelets as well as fibers at micrometric scale. By infrared and Raman spectroscopy we analyzed the secondary and tertiary structures of unordered aggregates and fibrils, drawing a pathway for their formation at the timescales from tents to hundreds of minutes. Dependence of the fibrillation route on environmental pH, above and below the isoelectric point, and on protein concentration has also been explored. We found that it is possible to direct the process towards the formation of superstructures with different morphologies and different sizes along with fibrils, after destabilization of the native fold and the formation of β-sheet rich structures. A different mechanism characterizes aggregate/fibril elongation of cyt c in Tris-HCl, in comparison with NaOH environment.

The unambiguous quantification of the proton transfer in Protic Ionic Liquids (PILs) and its differentiation from the concept of ionicity are still unsolved questions. Albeit researchers awfully quickly treat them as synonyms, the two concepts are intrinsically different and imply a dramatic modification in the expected chemical and physical properties of a PIL. Some attempts have been made to shed light on this discrimination, but single-technique-based approaches fail in giving a clear answer. Aiming at definitively figuring out the differentiation between proton transfer and ionicity, we performed a multi-technique analysis (NMR, Raman, IR, thermal and electrochemical analyses, among others). Indeed, thermal and spectroscopic analyses are employed to determine the acid strength's role in ions' complete formation. To overcome the ambiguity between ionicity and formation degree, we introduce a new paradigm where Reduced Ionicity accounts for both the quantities mentioned above. The reduced ionicity directly affects the thermal stability, the phase behavior, and the spectroscopic observations, resulting in particular features in NMR and vibrational spectra. The combination of physical-chemical analyses and Pulsed-Gradient Spin-Echo (PGSE) NMR allows determining the reduced ionicity (and not the ionicity, as reported so far) of the investigated systems. In this context, being the proton transfer not quantitatively accessible directly, the reduced ionicity of a reference series of triethylamine-based PILs is investigated through transport properties as a function of temperature. Our findings point towards a substantial dependence of the reduced ionicity by the acid strength and the anion's coordination power. Furthermore, some interesting insights about the proton transfer are obtained, combining all the findings collected.

The interaction of cytochrome c (cyt c) with natural and synthetic membranes is known to be a complex phenomenon, involving both protein and lipid conformational changes. In this paper, we combined infrared and fluorescence spectroscopy to study the structural transformation occurring to the lipid network of cardiolipin-containing large unilamellar vesicles (LUVs). The data, collected at increasing protein/lipid ratio, demonstrate the existence of a multi-phase process, which is characterized by: (i) the interaction of cyt c with the lipid polar heads, (ii) the lipid anchorage of the protein on the membrane surface, and (iii) a long-distance order/disorder transition of the cardiolipin acyl chains. Such effects have been quantitatively interpreted introducing specific order parameters and discussed in the frame of the models on cyt c activity reported in literature.

We have used grazing-angle infrared spectroscopy with polarized radiation to detect the Berreman effect (BE) in the two-dimensional electron systems (2DES) which form spontaneously at two interfaces: one between an amorphous film LaAlO3 and its SrTiO3 substrate (LAO/STO), and another at the interface between the topological insulator (TI) Bi2Se3 and its sapphire substrate. In both systems we have thus extracted the 2DES parameters at different temperatures. In the quasi-2DES under amorphous LAO, the surface density ns is higher than under crystalline LAO, while the mobility is nearly the same and the thickness d is 7 nm. In ultrapure Bi2Se3 on sapphire, preliminary data provided d < 1 nm and ns ≈ 1013 cm−2, indicating, by comparison with existing estimates, that the BE indeed detects the topological surface states.

We apply mid-infrared absorption microspectroscopy to investigate the light-induced conformational changes of bacteriorhodopsin embedded in native purple membranes deposited on gold substrates. The difference spectra (visible light ON-visible light OFF) obtained on thin films of bacteriorhodopsin display main spectral features connected to the light-induced proton pump process, representing a promising preliminary step towards the investigation of light-sensitive proteins by means of mid-IR tip-enhanced nanospectroscopy.

The Berreman effect (BE) allows one to study the electrodynamics of ultrathin conducting films at the surface of dielectrics by use of grazing-angle infrared spectroscopy and polarized radiation. Here, we first apply the BE to the two-dimensional electron system (2DES) at the interface between a high-purity film of the topological insulator Bi_{2}Se_{3} and its sapphire substrate. We determine for the 2DES a charge density n_{s}=(8±1)×10^{12} cm^{-2}, a thickness d=0.6±0.2 nm, and a mobility μ^{IR}=290±30 cm^{2}/V s. Within errors, all of these parameters result in being independent of temperature between 300 and 10 K. These findings consistently indicate that the 2DES is formed by topological surface states, whose infrared response is then directly observed here.

We have used grazing-angle infrared spectroscopy to detect the Berreman effect (BE) in the quasi-two-dimensional electron system (q-2DES) which forms spontaneously at the interface between SrTiO 3 (STO) and a thin film of LaAlO 3 (LAO). From the BE, which allows one to study longitudinal optical excitations in ultrathin films like the q-2DES, we have extracted at different temperatures its thickness, the charge density and mobility of the carriers under crystalline LAO (sample A), and the charge density under amorphous LAO (sample B). The latter quantity turns out to be higher than in sample A, but a comparison with Hall measurements shows that under amorphous LAO the charges are partly localized at low T with a low activation energy (about 190 K in units of kB) and are thermally activated according to a model for large polarons. The thickness of the q-2DES extracted from our spectra turns out to be 4±1 nm for crystalline LAO and 7±2 nm for amorphous LAO.

Proton caged compounds exhibit a characteristic behavior when directly dosed into cells or being coupled to gold nanoparticles prior to the dosing. When irradiated in the near ultraviolet region, they release protons that interact with intracellular HCO3− to yield H2CO3. The dissociation of carbonic acid, then, releases CO2 that can be distinctively singled out in infrared spectra.In the process of searching a pathway to augment the intracellular uptake of proton caged compounds, we probed the association of 1-(2-nitrophenyl)-ethylhexadecyl sulfonate (HDNS) with DMSO, an agent to enhance the membrane permeability. We found out a different UV-induced protonation mechanism that opens up to new conduits of employing of proton caged compounds. Here, we report the infrared data we collected in this set of experiments. Keywords: Proton caged compounds, DMSO, Intracellular proton release

Photo-Thermal Induced Resonance (PTIR) nanospectroscopy, tuned towards amide-I absorption, was used to study the distribution of proteic material in 34 different HeLa cells, of which 18 were chemically stressed by oxidative stress with Na3AsO3. The cell nucleus was found to provide a weaker amide-I signal than the surrounding cytoplasm, while the strongest PTIR signal comes from the perinuclear region. AFM topography shows that the cells exposed to oxidative stress undergo a volume reduction with respect to the control cells, through an accumulation of the proteic material around and above the nucleus. This is confirmed by the PTIR maps of the cytoplasm, where the pixels providing a high amide-I signal were identified with a space resolution of ∼300 × 300 nm. By analyzing their distribution with two different statistical procedures we found that the probability to find protein clusters smaller than 0.6 μm in the cytoplasm of stressed HeLa cells is higher by 35% than in the control cells. These results indicate that it is possible to study proteic clustering within single cells by label-free optical nanospectroscopy.

The Berreman effect (BE) allows one to study the electrodynamics of ultrathin conducting films at the surface of dielectrics by use of grazing-angle infrared spectroscopy and polarized radiation. Here, we first apply the BE to the two-dimensional electron system (2DES) at the interface between a high-purity film of the topological insulator ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ and its sapphire substrate. We determine for the 2DES a charge density ${n}_{s}=(8\ifmmode\pm\else\textpm\fi{}1)\ifmmode\times\else\texttimes\fi{}{10}^{12}\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}2}$, a thickness $d=0.6\ifmmode\pm\else\textpm\fi{}0.2\text{ }\text{ }\mathrm{nm}$, and a mobility ${\ensuremath{\mu}}^{\mathrm{IR}}=290\ifmmode\pm\else\textpm\fi{}30\text{ }\text{ }{\mathrm{cm}}^{2}/\mathrm{V}\text{ }\mathrm{s}$. Within errors, all of these parameters result in being independent of temperature between 300 and 10 K. These findings consistently indicate that the 2DES is formed by topological surface states, whose infrared response is then directly observed here.

Fibrillogenesis of monomeric human insulin in the presence or absence of (-)-epigallocatechin-3-gallate and melatonin was here investigated using a multi-technique approach. Results from Raman and Infrared spectroscopy pointed out that a high content of intermolecular β-sheet aggregates is formed after long-term incubation. However, near UV experiments, Dynamic Light Scattering, Thioflavin-T fluorescence measurements and Atomic Force Microscopy revealed that the kinetics from native-to-fibrillar state of insulin is hampered only in the presence of (-)-epigallocatechin-3-gallate. Molecular dynamic simulations indicated that this compound binds near the B11–B18 protein segment, where hydrophobic residues responsible for the beginning of cooperative aggregation are located. Such a preferential binding region is not recognized by melatonin, a highly mobile molecule, which indeed does not affect fibril formation. The results of the present study demonstrate that (-)-epigallocatechin-3-gallate interferes with the insulin nucleation phase, giving rise to amorphous aggregates in the early stages of the aggregation process.

SrRuO3 (SRO) is a perovskite increasingly used in oxide-based electronics both for its intrinsic metallicity, which remains unaltered in thin films and for the ease of deposition on dielectric perovskites like SrTiO3, (STO) to implement SRO/STO microcapacitors and other devices. In order to test the reliability of SRO/STO also as high-current on-chip conductor, when the SRO dimensions are pushed to the nanoscale, here we have measured the electrodynamic properties of arrays of nanoribbons, fabricated by lithography starting from an ultrathin film of SRO deposited on a STO substrate. The nanoribbons are 6 or 4 nm thick, 400, 200 and 100 nm wide and 5 mm long. The measurements have been performed by infrared spectroscopy, a non-contact weakly perturbing technique which also allows one to separately determine the carrier density and their scattering rate or mobility. Far-infrared reflectivity spectra have been analyzed by Rigorous Coupled-Wave Analysis (RCWA) and by an Effective Medium Theory, obtaining consistent results. With the radiation polarized along the nanoribbons, we obtain a carrier density similar to that of a flat film used as reference, which in turn is similar to that of bulk SRO. Moreover, in the nanoribbons the carrier scattering rate is even smaller than in the unpatterned film by about a factor of 2. This shows that the transport properties of SRO deposited on STO remain at least unaltered down to nanometric dimensions, with interesting perspectives for implementing on-chip nano-interconnects in an oxide-based electronics. When excited in the perpendicular direction, the nanoribbons appear instead virtually transparent to the radiation field, as predicted by RCWA.

Legume crops represent a low input cultivation system, especially suitable to grow in organic farming conditions. We report here on chemico-physical, technological and nutritional evaluation of traditional lentils (Lens culinaris L.) and grass peas (Lathyrus sativus L.), consisting in local ecotypes at high risk of extinction. Lentils and grass peas were grown either under certified organic agriculture in the National Park of Alta Murgia in the Apulia region (Altamura) or under traditional practices in internal hill areas of the National Park of Cilento (Castelcivita) and in the High Sele Valley (Colliano), in the Campania region. Results indicate that lentils and grass pea from organic and traditional farming are characterized by peculiar properties, suggesting a high nutritional quality. In particular, it was possible to point out differences among ecotypes (i) in major building elements (α-helix, β-sheet) responsible for protein functionality and (ii) in the composition of phenolic (p-coumaric, ferulic, caffeic, vanillic) acid fractions with high bioavailability.

Cell membranes are intrinsically heterogeneous, as the local protein and lipid distribution is critical to physiological processes. Even in template systems embedding a single protein type, like purple membranes, there can be a different local response to external stimuli or environmental factors, resulting in heterogeneous conformational changes. Despite the dramatic advances of microspectroscopy techniques, the identification of the conformation heterogeneity is still a challenging task. Tip-enhanced infrared nanospectroscopy is here used to identify conformational changes connected to the hydration state of the transmembrane proteins contained in a 50 nm diameter cell membrane area, without the need for fluorescent labels. In dried purple membrane monolayers, areas with fully hydrated proteins are found among large numbers of molecules with randomly distributed hydration states. Infrared nanospectroscopy results are compared to the spectra obtained with diffraction-limited infrared techniques based on the use of synchrotron radiation, in which the diffraction limit still prevents the observation of nanoscale heterogeneity.

We present SEM, ThT fluorescence and circular dichroism (CD) data of amyloidogenic aggregates of cytochrome c (cyt c).This protein is of outmost relevance in many biochemical processes, such as respiratory chain in mitochondria and cells apoptosis. The present data focus on polymorphism of the protein aggregates obtained at the isoelectric point (IP) and by changing the environmental pH above and below the IP, the protein concentration and the base. The SEM images provide evidence for a large variety of structures, depending on the pH and on protein concentration: mature amyloid fibrils and overstructured platelets are distinguishable in the aggregates below IP, and relatively high cyt c concentration, whereas inhomogeneous amyloid formations are observed above it. At pH 10, i.e. close to IP, only characteristic protein particulates at the micrometric scale are observed. SEM and Fluorescence data have been acquired in dried drops of protein solution, prepared in different bases: TRIS-HCl, at the different pH values, or NaOH (pH 13). Along with this, at relatively low cyt c concentration compact layered structures are visible below the IP, though still made of a thin fibrils reticulate, whereas above the IP, also at low cyt c concentration, granulates structures are present, merging into compact layer, alongside with platelets and mature fibers. These areas are characterized by diffuse ThT-fluorescence and typical fibrils. The loss of the predominant alpha helix secondary structure was verified by CD spectra. Besides the intrinsic scientific relevance, this data collection provides a set of images useful for spectroscopists to discriminate among different morphologic protein formations and suggests pathways for the achievement of different kinds of cytochrome c aggregates. These data are add-ons of the paper published in the International Journal of Biomacromolecules, 138 (2019) 106–115, https://doi.org/10.1016/j.ijbiomac.2019.07.060 .

We present mid-infrared vibrational spectroscopy and imaging at the nanoscale of individual cell membranes deposited on ultraflat gold substrate by use of resonantly-enhanced mechanical photoexpansion technique. This platform allows one to measure the energy absorbed by the sample by monitoring its local thermal expansion with a nanometer atomic force microscope tip. The observed Amide-I and Amide-II bands of proteins in the spectrum acquired on individual purple membrane flakes, filled with bacteriorhodopsin (bR) molecules, are in good agreement with the far-field infrared spectrum collected on large numbers of membranes. Differences among the relative intensity of the two Amide bands in the near- and far-field spectra are attributed to different orientation of bR protein molecules in the two samples. Strong vibrational contrast imaging at the Amide-I of proteins with a lateral resolution of around 50 nm is reported for individual flakes of both purple membranes and artificial lipid vesicles loaded with channelrhodospin molecules.

By use of resonantly-enhanced mechanical photoexpansion technique we have performed mid-infrared vibrational spectroscopy and imaging on the nanoscale of individual purple membranes deposited on ultraflat gold substrate. The observed Amide I and Amide II bands of proteins are in good agreement with the far-field infrared transmission spectra previously collected on large numbers of membranes. A comparison between the near-field signal of single purple membranes and that of two overlapping membranes is presented. The results are discussed by adopting simple thermal and electromagnetic considerations.

The low-temperature softening of the TO1 phonon of SrTiO3 (STO), which determines its incipient ferroelectricity, is known to be partially hindered either in the bulk under strong electric fields, or in thin STO films. Here we show, by terahertz (THz) reflectivity measurements, that a similar effect is produced in bulk STO and at zero static field by ultrathin metallic films on its surface, like a 10-nm-thick film of SrRuO3 (SRO), or the two-dimensional electron system (2DES) present at the interface with LaAlO3. In SRO/STO, the observed hardening is well explained by the depolarizing action of the SRO free electrons which follow adiabatically the ion motion. In LAO/STO, a weaker TO1 hardening could be detected by patterning the 2DES in the form of microstripes and using a polarized THz field parallel (E-) or orthogonal (E-) to the stripes. At 10 K, when TO1 is excited together with the free electrons by E-, its absorbance is harder by about 7 cm-1 than that measured when TO1 is coupled to the plasmon-polariton confined within the stripes, being excited by E-.

We report on the electromagnetic response in metamaterials constituted by 2-dimensional array of metallic elements. The metamaterial transmittance presents a single dipolar resonance which can be easily shifted in the spectral region from 1 to 5 THz through the invariance properties of Maxwell equations under a scale transformation. Basing on these studies, we have designed and tested both direct (bandstop) and complementary (bandpass) filters fabricated by electron beam lithography, investigating the behavior of their figures of merit under the scale transformation. (C) 2010 Elsevier B.V. All rights reserved.

We measure the transmittance of LaMnO3 (LMO) thin films in the spectral range from 10 000 to 38 000 cm-1 as a function of temperature. The optical conductivity obtained from the transmittance data is decomposed into five Drude-Lorentz contributions: three of them show evident changes below the Neel temperature T N $\simeq$ 140 K. We discuss the band assignment in the framework of the tight-binding and of the orbitally degenerate Hubbard models. Our results ascribe the overall low-frequency spectrum of LMO to charge-transfer mechanisms involving the t 2g and e g electrons of the Mn ions, without invoking the presence of excitonic contributions. This finding definitely promotes a Mott-Hubbard scenario for LMO and provides an estimate of the Hamiltonian parameters.

The pressure effects on the Jahn–Teller (JT) distortion of three representative compounds belonging to the LaMn1−xGaxO3 (x = 0.2, 0.3, 0.4) family were widely investigated by means of X-ray diffraction and Raman spectroscopy. A compound with a fully coherent JT distorted structure (x = 0.2), one with regular octahedra (x = 0.6) and one in an intermediate configuration (x = 0.3) were selected. A pressure induced transition from the orthorhombic Pbnm phase towards structures with higher symmetry was observed in all the samples. Both Raman and X-ray data confirm that the most important structural effect of pressure is that of reducing the octahedral distortion. The appearance of a feature in the lattice parameter behavior connected to a structural instability was also detected, pointing out the key role of the JT distortion in stabilizing the manganite structures. On the other hand, the complete suppression of the JT distortion in the high-pressure phases cannot be claimed. The Raman spectra collected on the more distorted compounds (x = 0.2, 0.3) reveal clearly the coexistence of domains of distorted and more regular octahedra in a certain pressure range. The first sketch of the pressure vs. Ga-content phase diagram was drawn.

The optical conductivity of La–Ca, Nd–Sr, and Bi–Sr manganites with commensurate charge order (CO) has been first observed in the sub-THz region. Below, the ordering temperature TCO well-defined peaks are observed, associated with side bands. They are assigned to pinned phasons, and to combinations of phasons and amplitudons, respectively. In La1−n/8Can/8MnO3 with n=5, 6, one can thus determine the electron-phonon coupling, the effective mass of the CO system, and its contribution to the dielectric constant. Their values support a description of the CO in La–Ca manganites in terms of a CDW approach. In Bi0.5Sr0.5MnO3, where TCO> 500 K and the coupling is stronger, only the combination bands are clearly detected.

The secondary structure of legume (Phaseolus vulgaris L. and Lens culinaris L.) proteins was investigated by studying the amide I infrared absorption band in whole seed flours, before and after dry heating and autoclaving thermal treatments. The analysis procedure, set up on 7S and different model proteins, shows that the content of beta-sheet structures in lentil is higher than in common bean (47% vs. 32%). The dry heating does not appreciably affect secondary structures in lentil, while it causes a reduction of beta-sheets (to 13%), an increase of aggregates, and the appearance of random coil structures in common bean. The autoclaving treatment produces high amounts of aggregates in both legumes. However, in lentil, random coil structures are lower than in common bean and some beta-sheet structures are still detectable. These results indicate that multimeric heat-induced complexes of legume proteins have a high stability because of the high content in beta-sheet structures, in particular in lentil, which may adversely affect protein utilization. (C) 2007 Elsevier Ltd. All rights reserved.

Infrared (IR) nanospectroscopy performed in conjunction with atomic force microscopy (AFM) is a novel, label-free spectroscopic technique that meets the increasing request for nano-imaging tools with chemical specificity in the field of life sciences. In the novel resonant version of AFM-IR, a mid-IR wavelength-tunable quantum cascade laser illuminates the sample below an AFM tip working in contact mode, and the repetition rate of the mid-IR pulses matches the cantilever mechanical resonance frequency. The AFM-IR signal is the amplitude of the cantilever oscillations driven by the thermal expansion of the sample after absorption of mid-IR radiation. Using purposely nanofabricated polymer samples, here we demonstrate that the AFM-IR signal increases linearly with the sample thickness t for t > 50 nm, as expected from the thermal expansion model of the sample volume below the AFM tip. We then show the capability of the apparatus to derive information on the protein distribution in single cells through mapping of the AFM-IR signal related to the amide-I mid-IR absorption band at 1660 cm(-1). In Escherichia Coli bacteria we see how the topography changes, observed when the cell hosts a protein over-expression plasmid, are correlated with the amide I signal intensity. In human HeLa cells we obtain evidence that the protein distribution in the cytoplasm and in the nucleus is uneven, with a lateral resolution better than 100 nm.

A proton caged compound, the 1-(2-nitrophenyl)- ethylhexadecyl sulfonate (HDNS), was dosed into HEK-293 at different incubation times. Samples were irradiated with filtered UV light for inducing photolysis of the HDNS and then probed by infrared spectroscopy. The intracellular acidification reaction can be followed by monitoring the consequent CO2 peak intensity variation. The total CO2 produced is similar for all the samples, hence it is only a function of the initial HDNS concentration. The way it is achieved, though, is different for the different incubation times and follows kinetics, which results in a combination of a linear CO2 increase and a steep CO2 increase followed by a decay. This is interpreted in terms of confinement of the HDNS into intracellular vesicles of variable average size and sensitive to UV light when they reach critical dimensions.