Revisiting the conformational transition model for the pH dependence of BSA structure using photoluminescence, circular dichroism, and ellipsometric Raman spectroscopy.

Changes in pH affect metabolic pathways, primarily by modulating enzyme conformations, which is why a detailed analysis of pH-driven conformational transitions is required to understand the underlying biochemistry of diseases and biological organisms. In this work, we examined the pH-driven conformational dynamics of Bovine Serum Albumin (BSA), within the framework of the Foster Model. Circular Dichroism and Raman Optical Activity showed the conversion of helical into β-rich structures in the acid and basic regions, while an opening of BSA tertiary structure was shown by the upsurging of accessibility of ANS-BSA binding sites and the increasing of random contributions at regions F and B.

Photoluminescent ellipsometric circular dichroism.

A novel spectroscopic technique, photoluminescent ellipsometric circular dichroism (PECD), which distinguishes all radiative electronic transitions related to molecular chiral centers. Additionally, it is proposed as complementary to the ellipsometric Raman spectroscopy (ERS) technique, thus establishing a relationship between vibrational modes and electronic transitions, associated with molecular chiral centers. In this way, PECD turns into a powerful technique for chiral material characterization.

A fingerprint of amyloid plaques in a bitransgenic animal model of Alzheimer's disease obtained by statistical unmixing analysis of hyperspectral Raman data.

The global prevalence of Alzheimer's disease (AD) points to endemic levels, especially considering the increase of average life expectancy worldwide. AD diagnosis based on early biomarkers and better knowledge of related pathophysiology are both crucial in the search for medical interventions that are able to modify AD progression. In this study we used unsupervised spectral unmixing statistical techniques to identify the vibrational spectral signature of amyloid β aggregation in neural tissues, as early biomarkers of AD in an animal model.

Conjugation Length Distribution in Poly(p-phenylenevinylene) (PPV) Films.

We studied the absorption line-shape of poly(p-phenylenevinylene) (PPV) films deposited via spin coating and Langmuir-Blodgett techniques with the intent of identifying the conjugation length distribution in these two types of films, a key morphological aspect of conjugated polymer films. We treated the excitons in the polymer as independent oligomer excitons and modeled the absorption spectra of the individual oligomers using simple expressions for the oligomer size dependence of the gap energy, the line-broadening factor, the transition dipole moment and the Huang-Rhys parameter. We validated these expressions by independent measurements on phenyl-based oligomers and Density Functional Theory calculations.

Modeling adsorption processes of poly-p-phenylenevinylene precursor and sodium acid dodecylbenzenesulfonate onto layer-by-layer films using a Langmuir-type metastable equilibrium model.

The adsorption kinetics curves of poly(xylylidene tetrahydrothiophenium chloride) (PTHT), a poly-p-phenylenevinylene (PPV) precursor, and the sodium salt of dodecylbenzene sulfonic acid (DBS), onto (PTHT/DBS)n layer-by-layer (LBL) films were characterized by means of UV-vis spectroscopy. The amount of PTHT/DBS and PTHT adsorbed on each layer was shown to be practically independent of adsorption time. A Langmuir-type metastable equilibrium model was used to adjust the adsorption isotherms data and to estimate adsorption/desorption coefficients ratios, k=kads/kdes, values of 2x10(5) and 4x10(6) for PTHT and PTHT/DBS layers, respectively.