Abstract
Small-angle x-ray scattering and quasi-elastic light scattering measurements were conducted to analyze correlations between the structure and short-time dynamics of tyrocidine B·hydrochloride (TrcB) in ethanol, acetonitrile, and (R,S)-2-methylbutanol dispersions in the presence of 20.0% (v/v) water at 278 K and 298 K. The three TrcB dispersions exhibited peak position shifts that varied with the volume fraction. The experimental data were fitted to a model that considered the effective interaction potential, short-range attraction, and long-range repulsion. This model of repulsively interacting single TrcB particles is incompatible with the presence of equilibrium aggregate phases. The self-diffusion coefficient at the short-time limit (Dsh) decreased more as the TrcB concentration increased than one would expect for a corresponding hard-sphere or charged particle at the same volume fraction. At low volume fractions, the system consisted of monomers, dimers, and trimers. At high TrcB volume fractions, the main particles were larger aggregates. The collective diffusion coefficient, Dc, was constant when Q > Qc, where Qc is the position of the interference peak, which implies that there were no inter-monomer TrcB oligomer dynamics. This is because Dsh/D0 decayed much more quickly than the TrcB monomer as a function of the volume fraction. In vitro experiments revealed that antimicrobial activities were preserved at all volume fractions notwithstanding the presence of various oligomers.
Highlights
Physical studies on colloidal aggregates and oligomers in solutions provide valuable practical and theoretical information on equilibrium and non-equilibrium phase properties, which has important applications in drug-delivery systems,1–8 pharmaceutical formulations, e.g., lozenges,9 micelles,10 the stability of nanomaterials like colloidal quantum dots and other nanomaterials,11 and 2D and 3D crystallization.12 the stabilizing effect of the formed aggregates can be associated with a small amount of charge on the dispersed particle
At Qm 0.208 normalized averaged scattered intensity I(Q)/c is related to the form factor, ⟨P(Q)⟩, the averaged particle scattering over the ensemble of sizes and orientations, which is correlated with the tyrocidine B⋅hydrochloride (TrcB)
The occurrence of TrcB dispersion interference in ACN, ETN, and 2-MeB in the presence of 20% (v/v) water at 298 K and 278 K could be consistently described via the form factors and structure factors of individual TrcB particles, as modulated by an interaction potential with short-range attraction and long-range repulsion
Summary
Physical studies on colloidal aggregates and oligomers in solutions provide valuable practical and theoretical information on equilibrium and non-equilibrium phase properties, which has important applications in drug-delivery systems, pharmaceutical formulations, e.g., lozenges, micelles, the stability of nanomaterials like colloidal quantum dots and other nanomaterials, and 2D and 3D crystallization. the stabilizing effect of the formed aggregates (oligomers) can be associated with a small amount of charge on the dispersed particle. These forces influence a wide range of antimicrobial Trcs activities, including interactions with various intercellular structures and intracellular components, e.g., cell envelopes or sugars.. Both solvents ETN and methanol are widely used in the pharmaceutical industry, whereas ACN is commonly used for recording CD spectra because of its ability to solvate more in ACN than in ETN or methanol in the presence of water, but less in pharmaceutical formulations This is especially noteworthy because the spectral properties of Trcs dispersions can be monitored quantitatively due to the formation of Trcs aggregates that are governed by β-sheet secondary structures as a function of the Trcs concentration when this concentration is high..
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