Infrared nanospectroscopy depth-dependent study of modern materials: morpho-chemical analysis of polyurethane/fibroin binary meshes.

Infrared scattering-type scanning near-field optical microscopy (IR s-SNOM) and imaging is here exploited together with attenuated total reflection (ATR) IR imaging and scanning electron microscopy (SEM) to depict the chemical composition of fibers in hybrid electrospun meshes. The focus is on a recently developed bio-hybrid material for vascular tissue engineering applications, named Silkothane®, obtained in the form of nanofibrous matrices from the processing of a silk fibroin-polyurethane (SFPU) blend via electrospinning. Morphology and chemistry of single fibers, at both surface and subsurface level, have been successfully characterized with nanoscale resolution, taking advantage of the IR s-SNOM capability to portray the nanoscale depth profile of this modern material working at diverse harmonics of the signal. The applied methodology allowed to describe the superficial characteristics of the mesh up to a depth of about 100 nm, showing that SF and PU do not tend to co-aggregate to form hybrid fibers, at least at the length scale of hundreds of nanometers, and that subdomains other than the fibrillar ones can be present. More generally, in the present contribution, the depth profiling capabilities of IR s-SNOM, so far theoretically predicted and experimentally proven only on model systems, have been corroborated on a real material in its natural conditions with respect to production, opening the room for the exploitation of IR s-SNOM as valuable technique to support the production and the engineering of nanostructured materials by the precise understanding of their chemistry at the interface with the environment.

A Nanofocused Light on Stradivari Violins: Infrared s-SNOM Reveals New Clues Behind Craftsmanship Mastery.

It is well-known that all the phases of the manufacturing influence the extraordinary aesthetic and acoustic features of Stradivari's instruments. However, these masterpieces still keep some of their secrets hidden by the lack of documentary evidence. In particular, there is not a general consensus on the use of a protein-based ground coating directly spread on the wood surface by the Cremonese Master. The present work demonstrates that infrared scattering-type scanning near-fields optical microscopy (s-SNOM) may provide unprecedented information on very complex cross-sectioned microsamples collected from two of Stradivari's violins, nanoresolved chemical sensitivity being the turning point for detecting minute traces of a specific compound, namely proteins, hidden by the matrix when macro or micro sampling approaches are exploited. This nanoresolved chemical-sensitive technique contributed new and robust evidence to the long-debated question about the use of proteinaceous materials by Stradivari.

A multidisciplinary study unveils the nature of a Roman ink of the I century AD.

A multi-instrumental approach combining highly sensitive Synchrotron Radiation-based techniques was used to provide information on the real composition of a dry black ink powder found in a bronze inkwell of the first century AD. The presence of Pb, Cu and Fe in the powder, revealed by XRF and ICP-OES data, leads to raise several hypotheses on their origin. The inkpot and its lid were also investigated by Hand-Held XRF, revealing a bronze alloy (Cu-Sn) with a certain amount of Fe and Pb. The lid was found to be particularly enriched in lead. XRPD, XAS and FTIR measurements showed a substantial presence of silicates and common clay minerals in the ink along with cerussite and malachite, Pb and Cu bearing-carbonates, respectively. These evidences support the hypothesis of an important contamination of the ink sample by the burial environment (soil) and the presence of degradation products of the bronze inkpot. The combined use of IR, Raman, and GC-MS evidenced that the black ink is mainly composed of amorphous carbon deriving from the combustion of organic material mixed with a natural binding agent, Arabic gum.

Reflection FTIR spectroscopy for the study of historical bowed string instruments: Invasive and non-invasive approaches.

A micro-sample detached from a historical bowed string instrument represents a valuable record of the materials used by the great Masters of violin-making art. It allows researchers to collect a wealth of information and to disclose - at least partially - their procedures for finishing and varnishing. In the present work, a set of four cross-sectioned micro-samples - collected from well-preserved bowed string instruments made by Antonio Stradivari and Lorenzo Storioni - are investigated by Synchrotron Radiation (SR) FTIR micro-spectroscopy in reflection mode. SR-FTIR spectra are discussed both as point analysis and as univariate and multivariate chemical maps. The same cross-sections are also investigated by optical microscopy under UV light and SEM-EDX. Moreover, data obtained directly from the musical instruments by a non-invasive approach employing a portable reflection FTIR spectrometer are also considered. FTIR investigation of the cross-sections is a challenging task for such brittle and complex layered micro-samples. Nevertheless, the high intensity of the analytical SR beam used in reflection geometry allowed us to obtain informative FTIR spectra and to fully preserve the integrity of the samples. Both the non-invasive and the micro-invasive reflection FTIR approaches can reveal the materials spread on the wood surface to finish the musical instruments. The fingerprint of Lorenzo Storioni's production around 1790 emerged from the study of the cross-sectioned samples, definitely different from the technique of Stradivari.

Iron-mediated interaction of alpha synuclein with lipid raft model membranes.

The aberrant misfolding and aggregation of alpha synuclein (αS) into toxic oligomeric species is one of the key features associated with the pathogenesis of Parkinson's disease (PD). It involves different biochemical and biophysical factors as plasma membrane binding and interaction with heavy metal ions. In the present work, atomic force microscopy (AFM) is combined with Fourier Transform Infrared Spectroscopy (FTIR) measurements to investigate the interaction of wild-type (WT) and A53T mutated alpha synuclein with artificial lipid bilayers mimicking lipid raft (LR) domains, before and after ferrous cations (Fe2+) treatment. In the absence of iron, protein monomers produce a thinning of the membrane, targeting the non-raft phase of the bilayer preferentially. On the contrary, iron actively promotes the formation of globular protein aggregates, resembling oligomers, targeted to LR domains. In both aggregation states, monomer and oligomer, the mutated A53T protein exhibits a greater and faster membrane-interaction. These results underlie a new mechanism of membrane-protein interaction in PD. The targeting of Fe2+-promoted αS oligomers to LRs might be functional for the disease and be helpful for the development of new therapeutic strategies.

FTIR investigation of the secondary structure of type I collagen: New insight into the amide III band.

This work presents a thorough study on the Amide III band in fibrous proteins using Fourier Transformed Infrared Spectroscopy (FTIR). Type I collagen was chosen as a model for this family of proteins, not only because of its important role in mammalian tissues, but also for its involvement in several pathologies. In order to disclose the conformational information contained in the collagen bands, the spectral characteristics of Amide III of type I collagen were related to the ones of Amide I band, performing experiments of thermal denaturation of the protein in acidic solution. Data acquired allowed to observe the protein unfolding and retrieve information about its structural arrangements during the thermal cycle. Taking as guideline the well-known behaviour of the Amide I band, we correlated the structural changes deducible from Amide I analysis with the ones detectable for Amide III band, by exploiting three spectral analysis techniques, namely 2D-correlation analysis, second derivative analysis, and peak-fitting. This approach enabled us to jointly support the obtained results and finally to assign the components of the Amide III of a typical fibrous protein, such as type I collagen, to its characteristic secondary structure.

The earliest evidence for mechanically delivered projectile weapons in Europe.

Microscopic analysis of backed lithic pieces from the Uluzzian technocomplex (45-40 thousand yr ago) at Grotta del Cavallo (southern Italy) reveals their use as mechanically delivered projectile weapons, attributed to anatomically modern humans. Use-wear and residue analyses indicate that the lithics were hunting armatures hafted with complex adhesives, while experimental and ethnographic comparisons support their use as projectiles. The use of projectiles conferred a hunting strategy with a higher impact energy and a potential subsistence advantage over other populations and species.