Viscoelastic and small angle neutron scattering studies of concentrated protein solutions

Effective Long-Range Attraction between Protein Molecules in Solutions Studied by Small Angle Neutron Scattering

“…Recent measurements of small angle neutron scattering (SANS) intensity distribution in protein solutions show interesting results [5,6,10]. Beside the normal first diffraction peak, it is present a peak (cluster peak) appearing at a much smaller scattering wave vector, Q, due to the formation of ordered clusters.…”

“…It has been shown that the crystallization curves of some globular proteins appear to coincide with the phase diagrams of a hard sphere system interacting with a short range attraction [1,2,3]. Small angle neutron and X-ray scattering investigations of proteins suggest the presence of a short-range attractive interaction between protein molecules besides the electrostatic repulsion induced by the residual charges [4,5,6]. The DLVO potential has been successfully applied to many colloidal systems and protein solutions [3,4].…”

“…However, it does not seem to fully explain the rich behaviour of proteins [4,7,8,9], and due to the complexity of these systems (anisotropic property, irregular shape, distributed charge patches, etc. ), a complete understanding of the properties of the effective interactions between protein molecules in solutions remains a challenge [8].Recent measurements of small angle neutron scattering (SANS) intensity distribution in protein solutions show interesting results [5,6,10]. Beside the normal first diffraction peak, it is present a peak (cluster peak) appearing at a much smaller scattering wave vector, Q, due to the formation of ordered clusters.…”

Theoretical description of cluster formation in two-Yukawa competing fluids

“…[24,25], by means of a mesoscopic, coarse-grain theory for soft materials combining density functional and statistical field theory; more recently, the same formalism was used to investigate the general features of microscopic interaction potentials leading to inhomogeneous structures [26]. Investigations in this area attracted increasing attention also because they may shed light on aggregation phenomena that can precede arrested states [27][28][29][30][31][32][33][34]; more generally, the control of aggregation processes constitutes a crucial step in disparate realms of science and technology, e.g. in colloid and polymer science, in the study of human diseases caused by the formation of fibrillar aggregates, in the protein structure determination, in the production of photonic crystals, in food science.…”

“…In this work, we focus on the phenomenon of cluster formation, particularly regarding the temperature threshold whereupon clusters start to develop out of the fluid phase, giving rise to what we term in the rest of the paper "cluster fluid". The onset of aggregation is experimentally signalled by the appearance of a lowwavevector peak in the static structure factor of the fluid (cluster peak), beside the main particle-particle correlation peak [1,27,30]. Theoretical studies interpreted the development of such low-k peak in terms of enhanced density fluctuations that, at variance with the purely attractive case, do not evolve into a fully developed macroscopic phase separation [6,14,17]; therefore, the formation of aggregates in the fluid phase results from an appropriate balance between attraction, favouring the cluster growth at low enough temperature, and long-range repulsion, preventing a complete phase separation.…”