Flexibility and Charge of Solutes as Factors That Determine Their Diffusion in Casein Suspensions and Gels

Abstract

This work explores the influence of both the physicochemical characteristics of solutes and the solute-matrix interactions on diffusion in casein systems. Diffusion coefficients of three solute groups (dextrans, proteins, and peptides) presenting different physicochemical characteristics, such as molecular flexibility and charge, were measured using the technique of fluorescence recovery after photobleaching (FRAP). The casein systems had the same casein concentration, but different microstructures (suspension or gel), and/or a different pH (5.2 or 6.6). Flexible solutes diffused more rapidly through the casein systems than the rigid ones. Electrostatic interactions between charged solute molecules and the casein matrix were partly screened due to the high ionic strength of the systems. As a consequence, it was the flexibility of the solute molecule (rather than its charge) that most influenced its diffusion through casein systems.

Grazing of dairy cows on pasture versus indoor feeding on total mixed ration: Effects on low-moisture part-skim Mozzarella cheese yield and quality characteristics in mid and late lactation

“…The increase in bulk whey protein with milk protein is consistent with the relatively high rate of whey expulsion during the early stages of stirring (following cutting), when the differences in protein content between gels (from milks with different protein concentrations) still persist and manifest in the whey. As stirring time progresses, the outwork migration of whey and, most likely, the diffusivity of whey components (e.g., protein) also diminish (Everard et al, 2008;Mateo et al, 2009;Silva et al, 2015), concomitant with dehydration and concentration of paracasein within the cheese curd particle matrix.…”

“…A similar trend was observed by Ong et al (2013), namely no change in the protein concentration of salty whey from Cheddar cheese curd on increasing milk protein concentration from 3.5 to 6.0% (wt/wt). Such a trend is expected, owing to the impedance of the concentrated cheese matrix to the passage and diffusion of relatively large macromolecular solutes such as lactose and whey proteins (Silva et al, 2015;Czárán et al, 2018).…”

Bladder cancer cells re-educate TAMs through lactate shuttling in the microfluidic cancer microenvironment

“…This finding is in agreement with the findings that diffusivity decreased monotonically with the MW of the solute in all ECM gels, as reported by Roland et.al [ 32 ]. The flexibility, hydrophobicity and charge distribution of the solute molecule can influence the solute diffusion rate in polymer systems [ 33 ]. The MW of lactate is only one-thousandth that of signaling proteins.…”

Biophysical exploration of protein–flavonol recognition: effects of molecular properties and conformational flexibility

“…Typically, molecular recognition of active ligands with different molecular structures by a biopolymer shall directly or indirectly cause conformational alterations of the biomacromolecule, which would result in further discrepancies or changes in the flexibility of the biological macromolecule. [54][55][56] Such conformational variations should be embodied in the aspects of spatial changes of substructures, which are the fundamental components of the biomacromolecule. Within a protein structure, the conformational changes of the amino acid residues, which are the elements of a protein, could be impacted by the ligand, and then give rise to the conformational alterations of the protein.…”