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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 × 10 4  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 (ΔG 25°C 0 =-29.35 kJ mol -1 ), and the binding constant was 1.39 × 10 5  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., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Characterizing the energetics and molecular dynamics of binding between proteins and bioactive compounds is strategic. Using surface plasmon resonance, we demonstrated that β-casein (β-cas) and quercetin (Qct) form supramolecular complexes driven by an increase in entropy (ΔH° = 25.86 and TΔS° =53.49 kJ∙mol -1 at 25 °C). It was possible to infer that the β-cas/Qct complex was formed via an activated complex synthesized by an entropic reduction (TΔS ‡ (a) = -15.31 kJ mol -1 and TΔS ‡ (d) = -68.80 kJ mol -1 at 25 °C) and an enthalpic increase (ΔH ‡ (a) = 30.87 and ΔH ‡ (d) =5.0 kJ∙mol -1 at 25 °C). Independent of the nature of the Hofmeister ions, the salts KCl or KSCN increased complex stability by decreasing both the kinetic and thermodynamic enthalpy values, through shielding of the electrostatic interactions at the electric double layer of the interacting molecules. An increase in temperature favored both the association of the free interacting molecules and the dissociation of the thermodynamically stable β-cas/Qct complexes. These results provide insights into the β-cas/Qct interaction process and contribute to the understanding of how Hofmeister ions can modulate intermolecular interactions between proteins and small molecules., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Determine the thermodynamic and kinetic parameters of interaction between micellar casein (MC) and curcumin (CUR) is useful for the application of MC-CUR systems in food products. We used surface plasmon resonance (SPR) and ultraviolet-visible spectrophotometry (UV-vis) to study the complex formation between MC obtained from skimmed milk and CUR, MC carrying capacity, and thermal protection for CUR at a pH of 6.6. An MC could carry about 18,000 molecules of CUR. SPR suggested an enthalpy-driven process (∆H° = -64.63 kJ∙mol -1 and T∆S° ranging from -42.45 to -44.46 kJ∙mol -1 ). Temperature increased reduced the rate of MC-CUR complex formation and increased its dissociation rate. The activation energy for the formation of MC-CUR activated complexes was negative for association of free MC and CUR molecules (-62.8 kJ mol -1 ) and positive for dissociation of the thermodynamically stable complexes (1.80 kJ mol -1 ). MC protected the CUR against its thermal degradation when it was subjected to different temperatures (30, 40, 50, and 60 °C for 5.5 h). This study shows the importance of characterizing MC-small molecules interactions for better application of MC as a nanocarrier., (Copyright © 2019. Published by Elsevier B.V.)

To improve the efficiency of cyclodextrins as carotenoid carriers, the kinetics and thermodynamics of the inclusion complex formation between modified β-cyclodextrin (βCD-NH2) and β-carotene (βCT) were studied using surface plasmon resonance (SPR) at pH 7.4 and theoretical calculations. The observed dissociation rate of the [βCD-NH2/βCT]° inclusion complex is small (2.59 × 1 0 - 1 s - 1 ), indicating that βCD-NH2 only interacted with the βCT ionone group to form inclusion complex. The βCD-NH2/βCT binding constant is 2.80 × 1 0 4 Lmol - 1 (at 298.15 K), and its temperature dependence indicates that the [βCD-NH2/βCT]° formation is driven by hydrophobic interactions ( Δ H ∘ = 28.83 kJ l - 1 and T Δ S ∘ = 54.21 kJ l - 1 ) caused mainly by the βCT end group desolvation. In contrast, the formation of the [βCD-NH2/βCT]‡ activated complex via association between free molecules and dissociation of [βCD-NH2/βCT]° occurred with the overcoming of an energy barrier ( E a ‡ = 40.77 kJ mol - 1 and E d ‡ = 11.94 kJ l - 1 ) and decrease in entropy ( T Δ S a ‡ = - 11.70 kJ l - 1 and T Δ S d ‡ = - 65.92 kJ l - 1 ). [ABSTRACT FROM AUTHOR]

Abstract Structural, morphological and spectroscopic characterization of the Eu3+-doped Y 2 (MoO 4) 3 red phosphor incorporated with Au nanoparticles (Au NPs) synthesized via Pechini's method is reported in the present study. In order to evaluate the Au NPs and Eu3+ ions influence on the molybdate structure, the Y 2 (MoO 4) 3 , Y 2 (MoO 4) 3 :Eu3+, Y 2 (MoO 4) 3 /Au and Y 2 (MoO 4) 3 :Eu3+/Au samples were produced and fully investigated. All samples obtained at relatively low temperature, i.e., 650 °C, show molybdate as the unique phase with high crystallinity assisted by both Eu3+ ions and Au NPs. Water molecules detected in the molybdate structure probably are distorting MoO 4 , YO 6 and EuO 6 polyhedra similarly to the Au NPs incorporated in the same lattice. These Au NPs are spherical-shaped with a diameter near to 46 nm and they are located on the molybdate particle surface. The Eu3+-doped phosphors, with or without the presence of Au NPs, exhibit intense red luminescence characteristic of the Eu3+ ion inserted in low-symmetry sites. However, the Au NPs increase the radiative emission rate and absolute quantum yield of the Eu3+ 5D 0 emitter state due to the excitation field enhancement caused by the local surface plasmon resonance absorption effect of gold nanoparticles, which was confirmed by diffuse reflectance measurements. Finally, the Eu3+ quantum efficiency enhancement to 92% played by the gold nanoparticles and the high red color purity qualify the obtained phosphor for photonic applications. Graphical abstract Image 1 Highlights • Eu3+ ions and Au nanoparticles favor the Y 2 (MoO 4) 3 phase formation. • Spherical Au NPs incorporated on the Y 2 (MoO 4) 3 surface during the calcination step. • Eu3+ ions and Au NPs are leading to distortions in the MoO 4 and YO 6 polyhedra. • Eu3+ quantum efficiency (η Eu) enhancement to 92% played by the Au NPs. • The high η Eu and color purity qualify the phosphor for photonic applications. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Lactoferrin-Brij58 interaction form a entropically driven complex, [bLF-Brij58]○. • Stability of [bLF-Brij58]○ increases at elevated temperatures. • [bLF-Brij58]○ is formed via the transition state intermediate [bLF-Brij58]‡. • [bLF-Brij58]‡.enthalpic barrier is higher in the adsorption step. • Transition state entropic barrier is dominated by conformation change. [ABSTRACT FROM AUTHOR]

To explore in vivo application of quantum dots (QDs), it is essential to understand the dynamics and energetics of interactions between QDs and proteins. Here, surface plasmon resonance (SPR) and molecular docking were employed to investigate the kinetics and thermodynamics of interactions between human serum albumin (HSA) and CdTe QDs (~3 nm) functionalized with mercaptopropionic acid (MPA) or thioglycolic acid (TGA). Kinetic analysis showed that HSA–QD interactions involved transition-complex formation. Despite the structural similarities between MPA and TGA, the [HSA−CdTe@TGA]‡ formation by association of free HSA and QDs demanded 70% more energy and higher entropic gain (E a − TGA ‡= 65.10 and T ∆ S a − TGA ‡= 28.62 kJ mol−1) than the formation of [HSA−CdTe@MPA]‡ (E a − MPA ‡ = 38.13 and T ∆ S a − MPA ‡ = 0.53kJ mol−1). While the [HSA−CdTe@MPA]° dissociation required higher energy and lower entropy loss (E d − MPA ‡ = 49.96 and T ∆ S d − MPA ‡ = − 32.18kJ mol−1) than the [HSA−CdTe@TGA]° dissociation (E d − TGA ‡= 30.78 and T ∆ S d − TGA ‡= − 51.12 kJ mol−1). The stability of [HSA−QDs]° was independent of the temperature and functionalizing group. However, the enthalpic and entropic components were highly affected by the substitution of MPA (ΔH ° = − 11.83 and TΔS ° = 32.72 kJ mol−1) with TGA (ΔH ° = 34.31 and TΔS ° = 79.73 kJ mol−1). Furthermore, molecular docking results indicated that the metal site on the QDs contributes to the stabilization of [HSA−QDs]°. Therefore, differences in QD functionalization and surface coverage densities can alter the HSA–QD interaction, thus their application. [Display omitted] • Human serum albumin (HSA) binds to CdTe quantum dots (QD) with high affinity. • [HSA − CdTe @ MPA]° stable complex formation was enthalpic and entropically favorable. • [HSA − CdTe @ TGA]° stable complex formation was entropically driven. • The QD surface coverage highly affects the thermodynamic and kinetic parameters. • The HSA-QD interaction mechanism is altered by the QD surface coverage density. [ABSTRACT FROM AUTHOR]

The complexation between protein and polyphenol affects their biological functions. A complete understanding of such interactions requires comprehensive thermodynamic and kinetic characterizations. Surface plasmon resonance (SPR) and fluorescence spectroscopy (FS) described similarly the thermodynamic of interaction between bovine lactoferrin (bLF) and epigallocatechin-3-gallate (EGCG). The formation of the bLF-EGCG complex is spontaneous (Δ G S P R o ≈ -29.00 kJ mol−1, Δ G F S o ≈ -26.00 kJ mol−1) and entropically driven (Δ H S P R o = 14.26, Δ H F S o = 10.20 kJ mol−1 and T Δ S S P R o ≈ 43.00, T Δ S F S o ≈ 36.00 kJ mol−1). The kinetic parameters obtained by SPR showed that the reaction occurs through an activated complex, whose energetic formation parameters from the association of free molecules ( E a c t (a) = 49.5 kJ mol−1, Δ H a ‡ = 47.0 kJ mol−1, and T Δ S a ‡ = −2.10 kJ mol−1) were higher than those in the opposite direction (namely the dissociation of the stable complex, E a c t (d) = 17.4 kJ mol−1, Δ H d ‡ = 32.8 kJ mol−1, and T Δ S d ‡ = −45.10 kJ mol−1), except for Δ G ‡ (Δ G a ‡ = 49.1 kJ mol−1 and Δ G d ‡ = 77.9 kJ mol−1). This study provides useful information for optimizing the use of bLF – EGCG complex as a bioactive compound in different systems, such as medical, food, cosmetic, and pharmaceutical formulations. Image 1 • Epigallocatechin-3-gallate (EGCG) and bovine lactoferrin (bLF) form a stable complex. • bLF – EGCG complex formation was driven by enthalpic and entropic interactions. • bLF – EGCG complex formation proceeded through an intermediate complex. • Intermediate formation from free EGCG and bLF was accompanied by an entropy decrease. • Fluorescence spectroscopy supported SPR thermodynamic binding parameters. [ABSTRACT FROM AUTHOR]

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 (ΔG AZA o = −30.50 and ΔH AZA o = 10.8 (kJ·mol−1)) were higher in magnitude than those of the BLF-MB systems (ΔG MB o = −27.3 and ΔH MB o = 5.72 (kJ·mol−1)). To increase the systems' entropy (TΔS AZA o = 41.3 and TΔS MB o = 33.0 (kJ·mol−1)), the hydrophobic interactions must outweigh the electrostatic repulsion, thereby promoting BLF-dye binding. The activation complex formation (E ac , a MB = 33, E ac , a AZA = 32, ∆H a, MB ‡ = 31, ∆H a, AZA ‡ = 30, ∆G a, MB ‡ = 51.84, ∆G a, AZA ‡ = 50.7, T∆S a, MB ‡ = −21, T∆S a, 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 (E ac , d MB = 16, E ac , d AZA = 6.4, ∆H d, MB ‡ = 14, ∆H d, AZA ‡ = 3.9, ∆G d, MB ‡ = 81.4, ∆G d, AZA ‡ = 74.93, T∆S d, MB ‡ = −68, T∆S d, 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. Unlabelled Image • Lactoferrin interacts with methylene blue or azure A dyes. • Kinetic and thermodynamic binding parameters are dye chemical structure dependent. • Entropic factors were the driving forces for apo-BLF/phenothiazine dye interaction. • Holo-BLF/phenothiazine dye interaction was enthalpy driven. • Dye (-CH 3) groups number decrease make BLF/phenothiazine dye interaction stronger. [ABSTRACT FROM AUTHOR]

To optimize the therapeutic applications of Congo red (CR), a potential inhibitor of protein aggregation, the kinetics and thermodynamics of the interactions between CR and a model protein need to be understood. We used surface plasmon resonance (SPR) and fluorescence techniques to determine the dynamics and thermodynamic parameters for the formation of complexes between CR and bovine serum albumin (BSA). CR interacts with BSA through a transition complex; the activation energy for association (E act(a) ) was determined to be 35.88 kJ mol −1 , while the activation enthalpy (ΔH ‡ ), entropy (ΔS ‡ ), and Gibbs free energy (ΔG ‡ ) are 33.41 kJ mol −1 , 0.18 J mol −1 K −1 , and 33.35 kJ mol −1 , respectively. When this intermediate transforms into the final CR-BSA complex, the entropy of the system increases and part of the absorbed energy is released; this process is associated with a reverse activation energy (E act(d) ) of 20.17 kJ mol −1 , and values of ΔH ‡ , ΔS ‡ , and ΔG ‡ of 17.69 kJ mol −1 , −162.86 J mol −1 K −1 , and 66.25 kJ mol −1 , respectively. A comparison of the SPR and fluorescence results suggests that there is more than one site where BSA interacts with CR. [ABSTRACT FROM AUTHOR]

Ponceau 4R (P4R) and bovine serum albumin (BSA) may interact changing food properties. We compared fluorescence spectroscopy and surface plasmon resonance (SPR) for studying, in vitro , the interactions between BSA and P4R at pH 7.4 and 3.5 in different temperatures. Fluorescence data pointed to the formation of a complex where P4R was bound on site I or II of BSA, with a stoichiometry around one and a binding constant (K b ) ranging from 1.37 × 10 5 to 20.15 × 10 6 L mol −1 . The complex formation at both pH was enthalpically driven (standard enthalpy change, ΔH° F = −60.69 and −63.06 kJ mol −1 , for pH 7.4 and 3.5, respectively). Using SPR, we also found the formation of 1:1 BSA-P4R complexes, but the calculated K b values were much smaller, on the order of 10 3 L mol −1 . Again, we found that the formation of BSA-P4R complex was driven by enthalpy decreasing; however the standard enthalpy change was less negative than that found by fluorescence (ΔH° SPR = −15.05 and −40.55 kJ mol −1 , at pH 7.4 and 3.5, respectively). Our results show that these distinct techniques provided different thermodynamic binding parameters for the BSA-P4R interaction, especially regarding ΔH° values, indicating that BSA-P4R binding was a multisite phenomenon, and that sites far from tryptophan residues were the main responsible by electrostatic interaction. Thus, this work clearly shows the importance of using complementary techniques for a complete thermodynamic characterization of complexes formed between azo-colorants and proteins; which is directly related to physicochemical properties of systems containing both molecules together. [ABSTRACT FROM AUTHOR]

Although toxic and dangerous, Phenylmethane (PhM) dyes have a variety of medicinal functions. To optimize the use of these dyes, it is essential to understand their interaction mechanism with proteins. Through surface plasmon resonance, we investigated the kinetics and thermodynamics of interaction between bovine lactoferrin (BLF) and PhM dyes at pH 7.4, which allowed elucidate the effect of the dyes' functional groups on the binding process. Negative ΔG° revealed that at thermodynamic equilibrium the formed [BLF-PhM]° complex was more stable than the free BLF and PhM molecules. The increase in the number of methyl groups in the PhM structure led to an increase in the rates of association (k a) and dissociation (k d) and the binding constant (K b). A similar effect was observed when comparing methyl violet B (MVB) and methyl violet 6 B (MV6B), in which the charged MV6B structure promoted an increase in the k a , k d , and K b values. By contrast, an increase in the number of phenyl groups (2–3 rings) led to a decrease in the K b values. The [BLF-PhM]° formation was entropically driven, indicating that hydrophobic interactions are critical for stabilizing these complexes These results are beneficial for understanding the molecular dynamics of protein-dye interactions. [Display omitted] • Bovine Lactoferrin (BLF) and phenylmethane dyes (PhM) formed stable complexes. • The interaction of PhM molecules occurs at the BLF hydrophobic sites. • Increase of –CH 3 number in the PhM structure led to strong changes at BLF site. • Increase of phenyl groups in the PhM structure led to higher ΔH° and TΔS° values. • The formation of stable [BLF-PhM]°complexes was more favorable at high temperatures. [ABSTRACT FROM AUTHOR]

• Peanut proteins (ARA or CON) interact with Congo red (CR) to form stable complexes. • CON has a higher binding affinity toward CR than does ARA. • Hydrophilic interactions were the main driving forces for [ A R A - C R ] 0 formation process. • The formation of [ C O N - C R ] 0 was enthalpically and entropically driven. • Transition complexes had a more structured conformation than their stable form. The thermodynamics and kinetics of arachin-Congo red (ARA - C R) and conarachin-Congo red (CON - C R) interactions were studied using surface plasmon resonance. KCl led to a reduction of up to 55% in the values of the associated kinetic constants, but it had less influence on the dissociation rates (less than 12%). The change in ionic strength had little effect on the thermodynamic stability of the complexes, but it did reduce their affinities (K b ( 25 ° C) [ A R A - C R ] 0 from 3.52 to 2.44 × 103 M−1 and K b (25 ° C) [ C O N - C R ] 0 from 15.1 to 12.5 × 103 M−1). The shielding of the electrical double layer favored ARA - C R hydrophilic interactions (Δ H [ A R A - C R ] 0 0 decreased from −30.60 to −42.98 kJ mol−1). On the other hand, hydrophobic interactions came to dominate during the formation of [ C O N - C R ] 0 (Δ H [ C O N - C R ] 0 0 increased from −11.21 to 28.34 kJ mol−1 and T Δ S 25 ° C [ C O N - C R ] 0 0 increased from 12.64 to 51.73 kJ.mol−1). The data presented here improve our understanding of plant-based protein nanocarriers of small bioactive molecules. [ABSTRACT FROM AUTHOR]

[Display omitted] • Thermodynamically stable complexes are formed through activated complexes. • The water molecules of the desolvation layer influence the association. • The interaction causes a conformational change at the beta-lactoglobulin site. • At the low temperature (285.15 K) the hydrophobic interaction prevails. • At high temperatures (301.15 K), hydrophilic interactions are dominant. Despite some thermodynamics studies about β-lactoglobulin (βLG) and resveratrol (RES) interactions, there is a gap regarding kinetics data about βLG-RES complex formation. Here, we determined the kinetic and thermodynamic parameters of βLG-RES interactions by using surface plasmon resonance (SPR). The kinetic association parameters were dependent on the 3D water structure present on the solvation shell of both interacting molecules. At lower temperature (285.15 K), all activation energies were positive (E a c t a ‡ = 82.86 kJ.mol−1, T Δ S a ‡ = 32.26 kJ.mol−1, and Δ C p a ‡ = 4.15 kJ.mol−1K−1) due to the higher water structuration on the RES and βLG solvation shell. All these energetic barriers become mainly from the energetic cost for the desolvation process of RES and βLG. At higher temperature (301.15 K), the solvation water structure decreases and all the above activation energies become negative (E a c t a ‡ = - 121.58 kJ.mol−1, T Δ S a ‡ = - 173.59 kJ.mol−1, and Δ C p a ‡ = - 29.92 kJ.mol−1K−1) because the direct interaction between desolvated RES and βLG molecules released more energy than it is absorbed by desolvation process. However, kinetic dissociation parameters were not dependent on the hydrogen bond density of the water solvation shell as showed by the temperature independence of dissociation energetic parameters. This non-dependence of the dissociation process from the desolvation step probably is because the water molecules interacting with the βLG-RES complex is not concentrated around/inside the protein site of interaction. The association of free molecules was 1.5 times faster than the dissociation of the thermodynamically stable complex (Δ G (a) ‡ ≅ 48.15 kJ.mol−1, Δ G (d) ‡ ≅ 73.10 kJ.mol−1). The lower free energy barrier observed for the association came from an isokinetic process where entropic and enthalpic parameters compensated for each other. The ΔG° values indicate that the thermodynamically stable complex predominates over free molecules. At low temperature (285.15 K), the hydrophobic interaction (Δ H° = 73.06 kJ.mol−1; T Δ S° = 99.60 kJ.mol−1) drove the βLG-RES complex formation while at high temperature (301.15 K), hydrophilic interactions became dominant (Δ H° = −142.50 kJ.mol−1; T Δ S° = −118.18 kJ.mol−1). [ABSTRACT FROM AUTHOR]

[Display omitted] • Quantum dots (QD) and lactoferrin (LF) formed a 1:1 [ L F - C d T e @ T G A ] ° stable complex. • [ L F - C d T e @ T G A ] ° formation was exothermic and entropically favorable at 298.15 K. • LF-QD binding is driven mainly by conformational and desolvation processes. • The [ L F - C d T e @ T G A ] ° formation passes by an [ L F - C d T e @ T G A ] ‡ intermediate state. • The [ L F - C d T e @ T G A ] ‡ formation occurred with iso -kinetic compensation. The kinetic and energetic characterization of interactions between quantum dots (QDs) and proteins is fundamental for understanding the toxicity and effectiveness of these nanoparticles in therapeutic applications. In this study, we combined kinetic and thermodynamic data from surface plasmon resonance (SPR) and isothermal titration microcalorimetry (ITC) to explore the complexation mechanism between thioglycolic acid-capped cadmium telluride QD (CdTe@TGA) and bovine lactoferrin (LF) under physiological conditions. The SPR results demonstrated that QD binds to LF forming a 1:1 [ L F - C d T e @ T G A ] ° thermodynamically stable complex, whose binding constant (K b SPR) ranged from 7.18 × 104 to 6.75 × 104 M−1. The association rate constant (k a) values were in the order of 103 M−1 s−1 while the complex residence time (t R) was ∼70 s. The formation of both [ L F - C d T e @ T G A ] ° and [ L F - C d T e @ T G A ] ‡ activated complexes occurred with the compensation of the enthalpic and entropic terms with the increase in temperature, characterizing enthalpy–entropy compensation (EEC), and iso -kinetic (IC) compensation, respectively. Using ITC, we also found the formation of a 1:1 [ L F - C d T e @ T G A ] ° complex, but the calculated K b ITC values were on the order of 107 L mol−1. Again, we found that the formation of [ L F - C d T e @ T G A ] °was exothermic and entropically favorable at 298.15 K, although Δ H ITC ° (−20.46 kJ mol−1) and T Δ S ITC ° (24.13 kJ mol−1) values were higher in magnitude than those found by SPR (Δ H SPR ° =−17.35 kJ mol−1 and T Δ S SPR ° = 10.39 kJ mol−1). We believe that this fundamental study will provide new insights into the safe and effective application of QDs in biological and medical fields. [ABSTRACT FROM AUTHOR]

[Display omitted] • β-cyclodextrin/resveratrol inclusion kinetic differs from β-cyclodextrin/RESAn1. • This kinetic difference become from desolvation process of interacting molecules. • Desolvation process affected mainly the kinetic entropic parameters. • Chemical structural differences effect occurs mainly on the association step. • Isokinetic compensation was observed only for the free molecules' association. The determination of the kinetics of inclusion processes is significant for the application of inclusion complexes as carriers for bioactive molecules. We determined the kinetic parameters of inclusion between modified β-cyclodextrin (β-CD- N H 2) and the polyphenols resveratrol (RES) and its structural analog (RESAn1), using the real-time analysis of surface plasmon resonance. The association and dissociation rate constants (k a and k d) showed that RESAn1 inclusion and its dissociation from β-CD- N H 2 were faster than a similar process for RES (k a β - C D - NH 2 / R E S A n 1 = 3.10∙104 ± 0.14 M−1s−1, k a β - C D - NH 2 / R E S =1.87∙103 ± 0.11 M−1s−1; k d β - C D - NH 2 / R E S A n 1 =0.39 ± 0.02 s−1, k d β - C D - NH 2 / R E S =0.30 ± 0.02 s−1, at 25 °C). The activated complex formation was also affected by the structural differences between the polyphenols, as showed by the activation energies of the association step (E act , a β - C D - NH 2 / R E S = 14.81 ± 0.64 kJ∙mol−1, E act , a β - C D - NH 2 / R E S A n 1 = −15.01 ± 0.75 to 82.35 ± 4.47 kJ∙mol−1). These effects of polyphenol structural differences are due to the desolvation process of interacting molecules. These results elucidate the role of small group to the dynamics of the molecular inclusion of β-CD. [ABSTRACT FROM AUTHOR]

[Display omitted] β-Carotene (β C A R) is a pro-vitamin A carotenoid with powerful antioxidant properties. However, it has low aqueous solubility, light and heat stability, and bioavailability. An interesting strategy to improve β C A R incorporation in food matrices while preserving its properties is the use of proteins as nanocarriers. Lysozyme (LYS) is a protein capable of carrying bioactive molecules and has antitumor, antiviral, and antimicrobial activities. To enable the use of LYS with β C A R , it is important to understand the dynamics of LYS - β C A R binding. Here, a thermodynamic and kinetic investigation of LYS - β C A R ° complex formation at physiological pH was carried out using fluorescence spectroscopy (FS), differential scanning nanocalorimetry (nanoDSC), molecular docking, and surface plasmon resonance (SPR). The binding constants were found to be on the order of 105 to 103 L mol−1 by FS and SPR, respectively, revealing that the interaction between LYS and β C A R is entropically driven. In addition, kinetic parameters related to intermediate complex formation were obtained, and we found that the rate of intermediate complex formation was higher on the free molecules association than on the LYS - β C A R ° dissociation based on the lower Δ G a ‡ values than Δ G d ‡. In addition, the occurrence of an isokinetic relationship indicates that intermediate complex formation results in changes in LYS binding sites, and both desolvation of the free molecules and conformational changes are temperature dependent. Thus, we have elucidated the dynamics of LYS - β C A R ° complex formation and provided important evidence that LYS can be used to carry β C A R , which will improve its application and functionality in food. [ABSTRACT FROM AUTHOR]

The formation of nanocomplexes between lutein (Lut) and lysozyme (Lys) is an alternative method of transporting Lut and improving its chemical stability. To optimize the formation of the Lut-Lys complex, binding assays were performed in the temperature range of 12–28 °C using real-time label-free surface plasmon resonance (SPR). Kinetics analysis showed that about 2000 Lut-Lys complexes are formed per second, of which 36% dissociate per second. The speed of formation of the activated complex was not affected by temperature because the Gibbs free energy barriers were almost constant (∆ ‡ G a 0 ≅ 53 and ∆ ‡ G d 0 ≅ 74 kJ.mol−1). There was a critical temperature (T ≅ 18.36 °C), below it the hydrophobic forces dominated (∆ ‡ H a 0 and ∆ ‡ H d 0 > 0) and above it hydrophilic interactions (∆ ‡ H a 0 and ∆ ‡ H d 0 < 0), such as van der Waals and hydrogen bonds, determined the activated complex formation. The stability of the thermodynamic complex was temperature-independent (∆G 0 ≅ − 21 kJ mol−1); however, the relative hydrophobic/hydrophilic contributions to the enthalpy and entropy change for the formation of this complex were dependent on the temperature (∆H 0 = 11.72 to − 36.71 kJ.mol−1 and T∆S 0 = 32.11 to − 15.54 kJ.mol−1). The SPR data provide useful insight for the discovery of potential lutein-protein nanocarriers. Unlabelled Image • Lutein (Lut) and Lysozyme (Lys) formed a stable complex via activated complex (AC). • The Gibbs free energy barrier of the AC formation is temperature independent. • Lut-Lys AC formation promoted the entropy system reduction. • Lut-Lys stable complex occurred through enthalpic-entropic compensation. • The Lut-Lys hydrophobic/hydrophilic interaction balance is temperature dependent. [ABSTRACT FROM AUTHOR]

The incorporation of bioactive molecules is important to improve food functionality. Despite the low solubility of some bioactive molecules, e.g., flavonoids, their binding with proteins contribute to their incorporation. There are some studies regarding globular proteins as flavonoid nanocarriers, but binding between flavonoids and βCN monomers, which are flexible proteins, is less reported. Here, the thermodynamics and kinetics of naringin–β-casein (NR–βCN) binding were determined by fluorescence spectroscopy (FS) and surface plasmon resonance (SPR). FS indicated that NR binds with βCN close to Trp 143 with K b 24 ° C = 2.71 × 104 m −1 and a key role of desolvation. SPR revealed that NR also binds far from Trp 143 (K b 24 ° C = 7.01 × 103 m −1) with small enthalpic and entropic temperature dependencies. We also present the kinetic parameters related to an intermediate complex formation, which was formed with minimal conformation and desolvation changes. Our results demonstrate βCN monomers as potential nanocarriers for NR. [ABSTRACT FROM AUTHOR]

The thermodynamics of curcumin (CUR) binding with bovine lactoferrin (bLF) was investigated by employing fluorescence spectroscopy (FS) and surface plasmon resonance (SPR) and comparing the results. Moreover, the kinetics of bLF-CUR binding was studied using SPR. FS data showed that with an increase in temperature (from 293.15 to 306.15 K), more complexes were formed (K b ranged from 2.07 × 104 to 6.68 × 104 M−1) owing to an increase in the entropy (Δ H ° = 66.70 kJ mol−1; T Δ S ° ranged from 90.93 to 94.98 kJ mol−1), demonstrating the role of hydrophobic interactions. However, the bLF-CUR complex formation detected through the SPR technique was entropically and enthalpically driven below and above 293.75 K, respectively. SPR also demonstrated that an enthalpy increase is compensated by an entropy increase for both stable and activated complex formation, characterizing enthalpy-entropy compensation and iso-kinetic compensation, respectively. These results are helpful to better understand the dynamics of complex formation between proteins and small bioactive molecules. Image 1 • Curcumin (CUR) and bovine lactoferrin (bLF) formed a stable complex. • SPR showed that bLF has more sites for CUR binding than those close to tryptophan. • The stable bLF-CUR complex formation passes through an intermediate state. • The bLF-CUR interaction occurred with enthalpy-entropy compensation. • bLF-CUR binding is driven mainly by the conformational and desolvation processes. [ABSTRACT FROM AUTHOR]

• Resveratrol (RES) and its analog RESAn1 form complexes with human serum albumin (HSA). • Polyphenol structure influenced the thermodynamic and kinetic binding parameters. • RESAn1 has a higher binding affinity toward HSA than does RES. • The RES-HSA and RESAn1-HSA complex formation was entropically driven. • Formation of the activated complex from the association was faster than dissociation. The thermodynamics and kinetics of binding between human serum albumin (HSA) and resveratrol (RES) or its analog (RESAn1) were investigated by surface plasmon resonance (SPR). The binding constant and the kinetic constants of association and dissociation indicated that RESAn1 has higher affinity toward HSA than does RES. The formation of these complexes was entropically driven ( T Δ S 0 HSA - R E S ≅ 33.8 , T Δ S 0 HSA - R E S A n 1 ≅ 56.4 KJ mol−1). However, for both polyphenols, the activation energy (E act ) of association (a) of free molecules was higher than that for dissociation (d) of the stable complex (E a c t a H S A - R E S = 11.37 , E a c t d H S A - R E S = - 3.06 , E a c t a H S A - R E S A n 1 = 30.76 , E a c t d H S A - R E S A n 1 = - 5.24 KJ mol−1), and the rate of association was faster than that of dissociation since the activation Gibbs free energy ( Δ G ‡) was lower for the former (Δ G aHSA - R E S ‡ ≅ 54.73 , Δ G dHSA - R E S ‡ ≅ 73.83 , Δ G aHSA - R E S A n 1 ‡ ≅ 54.14 , Δ G dHSA - R E S A n 1 ‡ ≅ 73.97 KJ mol−1). This study showed that small differences in the structure of polyphenols such as RES and RESAn1 influenced the thermodynamics and kinetics of the complex formation with HSA. [ABSTRACT FROM AUTHOR]