Maria Teresa Caccamo

Thermal Analysis on Bioprotectant Disaccharides by Elastic Incoherent Neutron Scattering

In this work the attention is focused on the thermal properties of trehalose, a glass-forming disaccharide which is very effective as a shelf-life extending compound in food industry. A wavelet analysis of Elastic Incoherent Neutron Scattering (EINS) intensity data as a function of the exchanged wavevector on trehalose and its homologous, maltose and sucrose, is presented. This analysis, which allows to highlight the correlation between the signal and the set of the scaled and translated mother functions, reveals the existence of different kinds of protons dynamics which cover different spatial scales. Differently from previous analyses, it emerges that the energy distribution as a function of the exchanged wavevector for trehalose mixture is less sensitive to temperature changes. Furthermore, the application of a new fitting model to the partial and global EINS intensity data as a function of temperature allows to put into evidence both the different wavevector dependence of the system relaxation times, extracted from the intensity vs temperature inflection point, and the higher thermal resistance of trehalose in respect to the other investigated disaccharides.

Ethylene Glycol - Polyethylene Glycol (EG-PEG) Mixtures: Infrared Spectra Wavelet Cross-Correlation Analysis.

Infrared spectra were collected on mixtures of ethylene glycol (EG) and polyethylene glycol 600 (PEG600) as a function of weight fraction from pure EG to pure PEG600. In this paper, it will be shown that while the OH vibrational contribution drastically reduces its center frequency from 3450 cm−1 to 3300 cm−1 in the weight fraction range 0–25%, the displacement of the mixture spectral features of the mixtures from ideal behavior, i.e., in the absence of interaction, shows the presence of a non-ideal mixing process. Furthermore, wavelet cross-correlation analysis of the registered pairs of spectra and of the intramolecular O–H stretching contributions reveals how the addition of a small amount of pure EG to PEG600 dramatically influences the structural properties of the polymeric matrix, owing to an increase the intermolecular connectivity. In particular, the wavelet cross-correlation parameters, evaluated between each pair of the registered data as a function of weight fraction, in a linear–logarithmic plot, reveals an inflection point for a weight fraction of about 25% of EG, which confirms that, within the three-dimensional networks of hydrogen-bonded EG-PEG600 molecules, a key role is played by EG in determining an increase in the hydrogen-bond network density.

Thermal restraint of a bacterial exopolysaccharide of shallow vent origin

To dynamically characterize the thermal properties of the fructose-rich exopolysaccharide (EPS1-T14), produced by the marine thermophilic Bacillus licheniformis T14, the Attenuated Total Reflectance Fourier Transform Infra-Red spectroscopy was coupled to variable temperature ranging from ambient to 80°C. The spectra were analyzed by the following innovative mathematical tools: i) non-ideal spectral deviation, ii) OH-stretching band frequency center shift, iii) spectral distance, and iv) wavelet cross-correlation analysis. The thermal restraint analysis revealed that the whole EPS1-T14 system possessed high stability until 80°C, and suggested that fucose was mainly involved in the EPS1-T14 thermal stability, whereas glucose was responsible for its molecular flexibility. Our results provide novel insights into the thermal stability properties of the whole EPS1-T14 and into the role of its main monosaccharidic units. As a new biopolymer, the thermostable EPS1-T14 could be used in traditional biotechnology fields and in new biomedical areas, as nanocarriers, requiring high temperature processes.