αs-Casein–PE6400 mixtures: a fluorescence study

Abstract

Micelles are a potential encapsulation system for bioactive compounds. In previous studies we were able to show that the triblock copolymer PEO13-PPO30-PE013 and alphas-casein are miscible within distinct temperature and concentration ranges. In this study, we wanted to test our hypothesis that mixed micelles are formed which, in turn, are able to solubilize hydrophobic compounds. Additionally we want to gain insight into the specific arrangement of individual molecules in these micelles. For that purpose, mixtures containing increasing mole fractions of casein (alphacas = 4.3 x 10(-4) to alphacas = 7.2 x 10(-3)) were examined at 30 degreeC. The hydrophobic fluorescence probe pyrene was used as a model solute. Emission spectra were recorded and I1/I3 and lex/I1 ratios were evaluated. Furthermore, the emission spectra of tryptophan were recorded and the maximum emission wavelength was evaluated. The determined parameters showed that micelles are formed in all solutions and that the solubilization of pyrene occurred. The calculated interaction parameter betaindicated that the mixing was antagonistic, possibly due to steric hindrances between the casein and the polymer. It seems that the mixed micelles are formed in such a way that the hydrophobic part of the polymer is attached to the hydrophobic parts of the caseins (a necklace and bead model) since the tryptophan residues are located in a hydrophobic environment above the CMC. We suggest a first structural arrangement model, recognizing that further studies will be required to prove and refine it.

Water solubilization of paclitaxel using polypeptides for cancer therapy

“…To address the mechanism of complex formation between hydrophobic PTX and polypeptides, we investigated the hydrophobicity of the polymer matrix in polypeptides using pyrene. 40,41 The ratio of fluorescence intensity at 375 (I 375 ) and 386 nm (I 386 ) is known as the polarity indicator of the microenvironment established by polymer chains. Pyrene encapsulated by polypeptides was prepared via HSVM, and the fluorescence spectrum of each complex was measured using a fluorometer (excitation wavelength, 336 nm; Fig.…”

Insights on Health and Food Applications of Equus asinus (Donkey) Milk Bioactive Proteins and Peptides—An Overview

“…These micelles are made up of different proteins (94%) and colloidal calcium phosphate, made of calcium, phosphate, magnesium, and nitrate, comprises 6%. These different caseins have hydrophilic regions and other hydrophobic regions that are different from one casein to another [13]. Besides, the caseins are phosphoproteins.…”

“…The proline residues, uniformly distributed into the casein structure, prevent secondary structures such as α helices or β sheets, hence the so-called open or “random coil” conformation of casein [ 14 ]. κ-caseins have a particular role, they are first of all glycoproteins and have only one phosphoserine group, but above all, they are stable in the presence of calcium ions and thus protect all of the caseins against precipitation and stabilize the micelles [ 13 , 15 ].…”

Untitled

“…Due to this structural establishment, αS-casein can also be used as structure formers such as stabilizers. Furthermore, αS-casein is able to develop mixed micellar structures, in which active substances can be entrapped [10]. κ-casein is a source of physiologically active compounds, caseinomacropeptides, which occurs during hydrolysis of κ-casein with chymosin [11].…”