Energetics of β-lactoglobulin-flavor compounds interactions.

Interaction of bovine β-lactoglobulin (BLG) with several flavor compounds (FC) (2-methylpyrazine, vanillin, 2-acetylpyridine, 2- and 3-acetylthiophene, methyl isoamyl ketone, heptanone, octanone, and nonanone) was studied by high-sensitivity differential scanning calorimetry. The denaturation temperature, enthalpy, and heat capacity increment were determined at different FC concentrations. It was found that the denaturation temperature and heat capacity increment do not depend on the FC concentration, while the denaturation enthalpy decreases linearly with the FC concentration.

Chitosan polyplexes: Energetics of formation and conformational changes in DNA upon binding and release.

Energetics of chitosan (CS) polyplexes and conformational stability of bound DNA were studied at pH 5.0 by ITC and HS-DSC, respectively. The CS-DNA binding isotherm was well approximated by the McGhee-von Hippel model suggesting the binding mechanism to be a cooperative attachment of interacting CS ligands to the DNA matrix.

Effect of Chitosan on the Activity of Water-Soluble and Hydrophobic Porphyrin Photosensitizers Solubilized by Amphiphilic Polymers.

In this work, we studied the photocatalytic activity of photosensitizers (PSs) of various natures solubilized with polyvinylpyrrolidone (PVP) and ternary block copolymer ethylene and propylene oxide Pluronic F127 (F127) in a model reaction of tryptophan photo-oxidation in water in the presence of chitosan (CT). Water-soluble compounds (dimegin and trisodium salt of chlorin e6 (Ce6)) and hydrophobic porphyrins (tetraphenylporphyrin (TPP) and its fluorine derivative (TPPF20)) were used as PSs. It was shown that the use of chitosan (Mw ~100 kDa) makes it possible to obtain a system whose activity is comparable to that of the photosensitizer-amphiphilic polymer systems.

Biodegradable thermoresponsive oligochitosan nanoparticles: Mechanisms of phase transition and drug binding-release.

Oligochitosan, a low molecular weight derivative of the cationic biopolymer, chitosan, currently shows a great potential of application as a biodegradable non-toxic stimuli-sensitive drug carrier. This paper aimed to elucidate the thermoresponsive potential of oligochitosan and the temperature-controlled drug binding and release to shed light on oligochitosan potential in stimuli-responsive drug delivery. Mechanisms of thermoresponsive behavior of oligochitosan induced by β-glycerophosphate (GP) were investigated using ITC, DSC, and DLS.

Cryostructuring of Polymeric Systems. 49. Unexpected "Kosmotropic-Like" Impact of Organic Chaotropes on Freeze⁻Thaw-Induced Gelation of PVA in DMSO.

Urea (URE) and guanidine hydrochloride (GHC) possessing strong chaotropic properties in aqueous media were added to DMSO solutions of poly(vinyl alcohol) (PVA) to be gelled via freeze⁻thaw processing. Unexpectedly, it turned out that in the case of the PVA cryotropic gel formation in DMSO medium, the URE and GHC additives caused the opposite effects to those observed in water, i.e.

Salt-Induced Thermoresponsivity of Cross-Linked Polymethoxyethylaminophosphazene Hydrogels: Energetics of the Volume Phase Transition.

Biodegradable hydrogels of cross-linked polymethoxyethylaminophosphazenes (PMOEAPs) of various cross-linking density and apparent subchain hydrophobicity were investigated by high-sensitivity differential scanning calorimetry and equilibrium swelling measurements. The volume phase transition of the hydrogels was found to be induced by salts of weak polybasic acids. The transition parameters were determined depending on the pH, phosphate concentration, cross-linking density, and apparent hydrophobicity of the gels.

Interactions of Non-Phosphorous Glycerolipids with DNA: Energetics, Molecular Docking and Topoisomerase I Attenuation.

The phosphorus-containing glycerolipid based antitumor drugs (edelfosine as a prototype) are currently in clinical trials. To avoid the use of potentially harmful phosphoric reagents in the preparation of biologically active glycerolipids, and to obtain the compounds without the phosphoester bond cleavable inside the cells, we developed the synthesis of non-phosphorous glycerolipids (NPGLs) with neutral or cationic polar 'heads'. In this study, we analyzed the ability of novel NPGLs L1-L5 to interact with duplex DNA and interfere with the DNA modifying enzyme topoisomerase I (topo I).

Binding affinity of thermoresponsive polyelectrolyte hydrogels for charged amphiphilic ligands. A DSC approach.

Controlled drug binding and release stand among top requirements postulated for targeted drug delivery systems of the new generations. "Smart" polymers and gels are highly suitable for the controlled delivery due to their structural sensitivity to minor environmental variations. The aim of this work was to study thermoresponsive polyanionic and polycationic hydrogels of N-isopropylacrylamide copolymers with acrylic acid and N-aminopropylmethacrylamide in terms of their interaction with two widely used drugs, propranolol and ibuprofen.

Ternary interpolyelectrolyte complexes insulin-poly(methylaminophosphazene)-dextran sulfate for oral delivery of insulin.

Ternary interpolyelectrolyte complexes of insulin with biodegradable synthetic cationic polymer, poly(methylaminophosphazene) hydrochloride (PMAP), and dextran sulfate (DS) were investigated by means of turbidimetry, dynamic light scattering, phase analysis, and high-sensitivity differential scanning calorimetry. Formation of ternary insoluble stoichiometric Insulin-PMAP-DS complexes was detected under conditions imitating the human gastric environment (pH 2, 0.15 M NaCl).

Polyplexes of poly(methylaminophosphazene): energetics of DNA melting.

The interaction of DNA with a synthetic biocompatible and biodegradable cationic polymer, poly(methylaminophosphazene) hydrochloride (PMAP·HCl), was investigated by high-sensitivity differential scanning calorimetry under conditions of strong and weak electrostatic interactions of the macroions. Thermodynamic parameters of the DNA double-helix melting were determined as a function of pH and the PMAP·HCl/DNA weight ratio. PMAP·HCL was shown to reveal two functions with respect to DNA: the polyelectrolyte function and the donor-acceptor one.

Conformational energetics of interpolyelectrolyte complexation between ι-carrageenan and poly(methylaminophosphazene) measured by high-sensitivity differential scanning calorimetry.

The interaction of poly(methylaminophosphazene) hydrochloride (PMAP·HCl) of varying degrees of ionization (f) with the potassium salt of ι-carrageenan was studied by high-sensitivity differential scanning calorimetry at a KCl concentration of 0.15 M, which is included for the purpose of stabilizing the helix conformation of the polysaccharide up to 55 °C. The conditions of strong (pH 3.

Temperature-sensitive chitosan-poly(N-isopropylacrylamide) interpenetrated networks with enhanced loading capacity and controlled release properties.

Interpenetrated polymer networks (IPN) of poly(N-isopropylacrylamide) (PNIPA) and chitosan (two grades) were prepared by free radical polymerisation and cross-linking of PNIPA (700 mM) with bis(acrylamide) (20 mM) in chitosan solutions (1.5 wt.% in acetic acid), and subsequent immersion in glutaraldehyde solutions (0 to 0.