0000000000560612
AUTHOR
F. Madonia
Photon scattering as a probe of microviscosity and channel size in gels such as sickle haemoglobin.
The aggregation of sickle-cell haemoglobin (HbS) is one of the most physiologically important and widely studied macromolecular gelation processes. Both the thermodynamics and kinetics of the process are important in determining the pathological consequences of deoxygenation of the red cells (and both must be understood if a rational strategy is to be developed for pharmacological intervention). We describe here a new and versatile technique for the study of the structure and formation of the HbS aggregates, that should be widely applicable to gel systems generally. We use laser autocorrelation spectroscopy to observe the diffusion of monodisperse polystyrene latex spheres in the interstice…
Spinodal demixing, percolation and gelation of biostructural polymers
We present a variety of new experiments which concern the self-assembly of a polymeric network from homogeneous solutions of Agarose, a representative biostructural polysaccharide used for previous studies at our laboratories. They allow deriving a semi-quantitative phase diagram in the T, C plane. The diagram includes both the spinodal and gelation lines. Below a value of about 2% w/v, concentration is not sufficient for direct gelation; however, quenching of the sol from high temperatures to below the spinodal line initiates the spinodal demixing. The latter generates two sets of regions having respectively, higher- and lower-than-average polymer concentrations. In the higher-concentratio…
Biomolecular-solvent stereodynamic coupling probed by deuteration.
Thermodynamic interpretation of experiments with isotopically perturbed solvent supports the view that solvent stereodynamics is directly relevant to thermodynamic stability of biomolecules. According with the current understanding of the structure of the aqueous solvent, in any stereodynamic configuration of the latter, connectivity pathways are identifiable for their topologic and order properties. Perturbing the solvent by isotopic substitution or, e.g., by addition of co-solvents, can therefore be viewed as reinforcing or otherwise perturbing these topologic structures. This microscopic model readily visualizes thermodynamic interpretation. In conclusion, the topologic stereodynamic str…