Dynamics and energetics of bovine lactoferrin and phenylmethane dyes interaction followed by surface plasmon resonance.

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 (ka) and dissociation (kd) and the binding constant (Kb). 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 ka, kd, and Kb values. By contrast, an increase in the number of phenyl groups (2-3 rings) led to a decrease in the Kb 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.

ß-lactoglobulin and resveratrol nanocomplex formation is driven by solvation water release.

Despite some thermodynamics studies about ß-lactoglobulin (ßLG) and resveratrol (RES) interactions, there is a gap regarding kinetics data about ßLG-RES complex formation. Here, we determined the kinetic and thermodynamic parameters of ßLG-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 (Eacta‡= 82.86 kJ.mol-1,TΔSa‡= 32.26 kJ.mol-1, and ΔCpa‡= 4.15 kJ.mol-1K-1) due to the higher water structuration on the RES and ßLG solvation shell. All these energetic barriers become mainly from the energetic cost for the desolvation process of RES and ßLG. At higher temperature (301.15 K), the solvation water structure decreases and all the above activation energies become negative (Eacta‡=-121.58 kJ.mol-1,TΔSa‡=-173.59 kJ.mol-1, and ΔCpa‡=-29.92 kJ.mol-1K-1) because the direct interaction between desolvated RES and ßLG 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 ßLG-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 (ΔG(a)‡â€¯â‰… 48.15 kJ.mol-1, ΔG(d)‡â€¯â‰… 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 (ΔH° = 73.06 kJ.mol-1; TΔS° = 99.60 kJ.mol-1) drove the ßLG-RES complex formation while at high temperature (301.15 K), hydrophilic interactions became dominant (ΔH° = -142.50 kJ.mol-1; TΔS° = -118.18 kJ.mol-1).

Application of Congo red dye as a molecular probe to investigate the kinetics and thermodynamics of the formation processes of arachin and conarachin nanocomplexes.

The thermodynamics and kinetics of arachin-Congo red (ARA-CR) and conarachin-Congo red (CON-CR) 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 ( [Formula: see text] from 3.52 to 2.44 × 103 M-1 and [Formula: see text] from 15.1 to 12.5 × 103 M-1). The shielding of the electrical double layer favored ARA-CR hydrophilic interactions ( [Formula: see text] decreased from -30.60 to -42.98 kJ mol-1). On the other hand, hydrophobic interactions came to dominate during the formation of [CON-CR]0 ( [Formula: see text] increased from -11.21 to 28.34 kJ mol-1 and [Formula: see text] 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.

The kinetics of formation of resveratrol-ß-cyclodextrin-NH2 and resveratrol analog-ß-cyclodextrin-NH2 supramolecular complexes.

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 ß-cyclodextrin (ß-CD-NH2) 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 (ka and kd) showed that RESAn1 inclusion and its dissociation from ß-CD-NH2 were faster than a similar process for RES ( [Formula: see text]  = 3.10∙104 ± 0.14 M-1s-1, [Formula: see text] =1.87∙103 ± 0.11 M-1s-1; [Formula: see text] =0.39 ± 0.02 s-1, [Formula: see text] =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 ( [Formula: see text] 14.81 ± 0.64 kJ∙mol-1, [Formula: see text] -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 ß-CD.

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.

Thermodynamic and kinetic insights into the interactions between functionalized CdTe quantum dots and human serum albumin: A surface plasmon resonance approach.

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 (Ea-TGA‡= 65.10 and T∆Sa-TGA‡= 28.62 kJ mol-1) than the formation of [HSA-CdTe@MPA]‡ (Ea-MPA‡ = 38.13 and T∆Sa-MPA‡ = 0.53kJ mol-1). While the [HSA-CdTe@MPA]° dissociation required higher energy and lower entropy loss (Ed-MPA‡ = 49.96 and T∆Sd-MPA‡ = - 32.18kJ mol-1) than the [HSA-CdTe@TGA]° dissociation (Ed-TGA‡= 30.78 and T∆Sd-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.

Application of pyridine-modified chitosan derivative for simultaneous adsorption of Cu(II) and oxyanions of Cr(VI) from aqueous solution.

The bioadsorbent C1, which is a chitosan derivative prepared in a one-step synthesis, was successfully used to adsorb Cr(VI) and Cu(II) simultaneously. Here, for the first time the simultaneous adsorption of a cation and an anion was modeled using the Corsel model for kinetics and the Real Adsorbed Solution Theory model for equilibrium data. Batch studies of the adsorption of Cu(II) and Cr(VI) in single and binary aqueous solutions were performed as a function of initial solute concentration, contact time, and solution pH. The maximum adsorption capacities of C1 in single and binary aqueous solutions were 1.84 and 1.13 mmol g-1 for Cu(II) and 3.86 and 0.98 mmol g-1 for Cr(VI), respectively. The reuse of C1 was investigated, with Cu(II) ions being almost completely desorbed and fully re-adsorbed. For Cr(VI), the desorption was incomplete resulting in a lower re-adsorption. Energy-dispersive X-ray spectroscopy was used for mapping the distributions of Cr(VI) and Cu(II) adsorbed on the C1 surface in single and binary adsorption systems. Isothermal titration calorimetry experiments were performed for Cr(VI) and Cu(II) adsorption in single solutions. The thermodynamic parameters of adsorption showed that the adsorption of both metal ions was enthalpically driven, but entropically unfavorable.

Energetic parameters of ß-casein/quercetin activated and thermodynamically stable complex formation accessed by Surface Plasmon Resonance.

Characterizing the energetics and molecular dynamics of binding between proteins and bioactive compounds is strategic. Using surface plasmon resonance, we demonstrated that ß-casein (ß-cas) and quercetin (Qct) form supramolecular complexes driven by an increase in entropy (ΔH°â€¯= 25.86 and TΔS° =53.49 kJ∙mol-1 at 25 °C). It was possible to infer that the ß-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 ß-cas/Qct complexes. These results provide insights into the ß-cas/Qct interaction process and contribute to the understanding of how Hofmeister ions can modulate intermolecular interactions between proteins and small 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.

Polydiacetylene/triblock copolymer/surfactant nanoblend: A simple and rapid method for the colorimetric screening of enrofloxacin residue.

Colorimetric nanosensors formed of polydiacetylene (PDA), triblock copolymer (L64 or F68), and sodium dodecyl sulfate (SDS), so-called nanoblends, were developed to detect enrofloxacin (ENRO) in aqueous media. The nanosensors show hydrodynamic diameter ranging from 234.2 ±â€¯3.5 to 801.6 ±â€¯17.8 nm for SDS concentrations of 13.0-21.0 mM, respectively. The lowest limit of detection was 0.054 µM, which is five times smaller than the maximum limit allowed by the European Union. The response surfaces showed that both the SDS and ENRO concentrations influenced the colorimetric response (p < 0.05), and kinetic rate of colorimetric transition (RCT). SDS concentration between 11.0 and 14.0 mM in the nanoblend yielded the most sensitive nanosensors for detecting ENRO. When L64 was replaced by F68, the colorimetric response of the nanoblends was similar, but PDA/F68/SDS showed a slower RCT than PDA/L64/SDS. The developed nanosensor is a sensitive and simple device for the fast detection of ENRO.

Kinetics and thermodynamics of bovine serum albumin interactions with Congo red dye.

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 (Eact(a)) was determined to be 35.88kJmol-1, while the activation enthalpy (ΔH‡), entropy (ΔS‡), and Gibbs free energy (ΔG‡) are 33.41kJmol-1, 0.18Jmol-1K-1, and 33.35kJmol-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 (Eact(d)) of 20.17kJmol-1, and values of ΔH‡, ΔS‡, and ΔG‡ of 17.69kJmol-1, -162.86Jmol-1K-1, and 66.25kJmol-1, respectively. A comparison of the SPR and fluorescence results suggests that there is more than one site where BSA interacts with CR.