Kinetic and thermodynamic of lactoferrin - Ethoxylated-nonionic surfactants supramolecular complex formation.

Understanding nonionic surfactant-protein interactions is fundamental from both technological and scientific points of view. However, there is a complete absence of kinetic data for such interactions. We employed surface plasmon resonance (SPR) to determine the kinetic and thermodynamic parameters of bovine lactoferrin-Brij58 interactions at various temperatures under physiological conditions (pH 7.4). The adsorption process was accelerated with increasing temperature, while the desorption rate decreased, resulting in a more thermodynamically stable complex. The kinetic energetic parameters obtained for the formation of the activated complex, [bLF-Brij58]‡, indicated that the potential energy barrier for [bLF-Brij58]‡ formation arises primarily from the reduction in system entropy. [bLF-Brij58]○ formation was entropically driven, indicating that hydrophobic interactions play a fundamental role in bLF interactions with Brij58.

Naringenin-lactoferrin binding: Impact on naringenin bitterness and thermodynamic characterization of the complex.

Naringenin (NG) is a flavonoid with many bioactive properties, however, its bitterness limits its use in foods. It is known that complex formation with proteins can mask this undesirable sensory property. Therefore, a trained panel evaluated the effect of bovine lactoferrin (LF) on NG bitterness using time-intensity analysis. LF reduced the maximum bitterness intensity and overall bitterness perception for NG by 27% and 33%, respectively. Isothermal titration nanocalorimetry (ITC), molecular docking (DC), and molecular dynamics (MD) were used to characterize NG-LF binding. These techniques provided similar values of ΔG° for binding ( [Formula: see text]  = -33.42 kJ mol-1; [Formula: see text]  = -32.22 kJ mol-1; [Formula: see text]  = -31.84 kJ mol-1). ITC showed that the complex formation is primarily entropy driven and DC suggested that NG binds at a hydrophobic site in LF. Here are presented strategic tools for promoting NG incorporation in food and health products.

Surface plasmon resonance study of interaction between lactoferrin and naringin.

Lactoferrin (LF) is a glycoprotein that serves as a potential vehicle for small bioactive molecules in food. In an effort to improve this functionality, the kinetic and thermodynamic interaction of LF with naringin (NR) was studied by surface plasmon resonance (SPR). The results demonstrated that the association rate constant between LF and NR was 5.00 × 104 M-1 s-1, while the dissociation rate of the complex was 0.36 s-1, at 25 °C. The stable complex predominated over free molecules (ΔG25°C0=-29.35 kJ mol-1), and the binding constant was 1.39 × 105 M-1, at 25 °C. The association of LF and NR to form an intermediate complex occurred in multi-steps. Nevertheless, the intermediate complex formation from the dissociation of the stable complex occurred in a single step with the activation energy independent of temperature. This study provides an important basis to explore LF as a vehicle for bioactive molecules.

Lactoferrin-phenothiazine dye interactions: Thermodynamic and kinetic approach.

Life manifestation is mainly based on biopolymer-ligand molecular recognition; therefore, the elucidation of energy and speed associated with protein-ligand binding is strategic in understanding and modulating biological systems. In this study, the interactions between methylene blue (MB) or azure A (AZA) dyes and bovine lactoferrin (BLF) were investigated by surface plasmon resonance, fluorescence spectroscopy, and isothermal titration microcalorimetry. Despite the molecular similarities between the dyes, the BLF-AZA binding thermodynamic parameters (ΔGAZAo = -30.50 and ΔHAZAo = 10.8 (kJ·mol-1)) were higher in magnitude than those of the BLF-MB systems (ΔGMBo = -27.3 and ΔHMBo = 5.72 (kJ·mol-1)). To increase the systems' entropy (TΔSAZAo = 41.3 and TΔSMBo = 33.0 (kJ·mol-1)), the hydrophobic interactions must outweigh the electrostatic repulsion, thereby promoting BLF-dye binding. The activation complex formation (Eac, aMB = 33, Eac, aAZA = 32, ∆Ha, MB‡ = 31, ∆Ha, AZA‡ = 30, ∆Ga, MB‡ = 51.84, ∆Ga, AZA‡ = 50.7, T∆Sa, MB‡ = -21, T∆Sa, AZA‡ = -21 (kJ·mol-1)), owing to free BLF and MB (or AZA) associations, was not affected by the dye chemical structure, while for the thermodynamically stable BLF-dye complex dissociation, the same energetic parameters (Eac, dMB = 16, Eac, dAZA = 6.4, ∆Hd, MB‡ = 14, ∆Hd, AZA‡ = 3.9, ∆Gd, MB‡ = 81.4, ∆Gd, AZA‡ = 74.93, T∆Sd, MB‡ = -68, T∆Sd, AZA‡ = -71.0 (kJ·mol-1)) were considerably affected by the number of methyl groups. Our results may be very useful to determine binding processes controlled by kinetic parameters, as well as to optimize the application of these photosensitive dyes in biological systems.

Effects of nisin on Staphylococcus aureus count and physicochemical properties of Minas Frescal cheese.

The aim of this work was to evaluate the effects of nisin on in vitro and in situ Staphylococcus aureus counts. For in vitro experiment, milk was inoculated with 5.0 log cfu·mL(-1) of S. aureus and nisin was added at concentrations of 0, 100, 200, 400, and 500 IU mL(-1). The main effect of the bacteriocin was lag phase extension from 0h, for 0 and 100 IU·mL(-1) to 8h, when 200, 400, and 500 IU·mL(-1) of nisin were used; however, log phase was not affected. Microbial growth rate was found to be exponential and around 0.11 log cfu·mL(-1)·h(-1) for all treatments. For in situ experiments, 0, 400, and 500 IU·mL(-1) of nisin were directly added to pasteurized milk previously inoculated with 5.0 log cfu·g(-1) of S. aureus. Milk, curd, and whey were analyzed to S. aureus counts. Nisin at concentration of 500 IU·mL(-1) was able to reduce S. aureus count in curd and whey, demonstrating nisin partition between both phases. Throughout storage at 4°C, S. aureus count increased for all treatments, but the bacterial grew slower when nisin was added in both concentrations, maintaining S. aureus count about 1.5 log cycles lower than the control, despite abusive initial S. aureus count. Therefore, nisin seems to play an important role in reducing S. aureus initial count in cheese made with highly contaminated milk. Nisin showed potential to be used as an additional, important hurdle to improve Minas Frescal cheese safety, without replacing good manufacturing practices.

Thermodynamic study of colorimetric transitions in polydiacetylene vesicles induced by the solvent effect.

We report the synthesis of 10,12-pentacosadyinoic acid (PCDA) and PCDA + cholesterol (CHO) + sphingomyelin (SPH) vesicles dispersed in water and the determination of their colorimetric response induced by small amount of organic solvents. In the absence of solvent, PCDA and PCDA/CHO/SPH vesicles showed an intense blue color. The addition of CHCl(3), CH(2)Cl(2), and CCl(4) caused a colorimetric transition (CT) in both structures with the following efficiency: CHCl(3) > CH(2)Cl(2) ≅ CCl(4). However, CH(3)OH did not cause a blue-to-red transition. By microcalorimetric technique we also determined, for the first time, the enthalpy change associated with the CT process and the energy of interaction between solvent molecules and vesicle self-assembly. We observed that the chloride solvents induced a colorimetric transition, but the thermodynamic mechanism was different for each of them. CT induced by CHCl(3) was enthalpically driven, while that caused by CH(2)Cl(2) or CCl(4) was entropically driven.

Effect of active packaging incorporated with triclosan on bacteria adhesion.

Antimicrobial polyethylene and cellulose based films incorporated with triclosan were studied. The antimicrobial efficacy, the hydrophobicity, microscopic and the mechanical characteristics of the films, as well free energy of adhesion between bacteria and antimicrobial films were evaluated. It was observed that both polyethylene and cellulose based films incorporated with the antimicrobial were homogeneous. Furthermore, the addition of triclosan did not affect mechanical characteristics of the films (P > 0.05). However, triclosan incorporated into polyethylene films reduced its hydrophobicity while antimicrobial cellulose based films became more hydrophobic. The adhesion was thermodynamically favorable between tested bacteria and polyethylene films. On the other hand, the adhesion to triclosan cellulose based film was thermodynamically unfavorable to Staphylococcus aureus and Escherichia coli and favorable to Listeria innocua and Pseudomonas aeruginosa. Polyethylene and cellulose based films showed inhibitory effect against S. aureus and E. coli, being the inhibition halo higher for polyethylene films. This study improves the knowledge about antimicrobial films.

Recent patents on active packaging for food application.

Active packaging, a new concept in the field of food packaging, has been developed in order to meet the new demands of consumers and the diverse goals existing in the food industry. There are several types of active packaging, including gas, moisture, and UV absorbers, as well as flavor, antioxidant, and antimicrobial releasers. In this review, we aim to highlight recent patents and developments in active packaging, as well as the principles of action for each of these technologies. Active packaging is an innovative area, which allows the production of food products with better sensorial features and extended shelf-life, thus ensuring enhanced food quality and safety. It is important to inform consumers about this new technology, since it may be a revolutionary tool in the food technology area.