Intermolecular interactions between supramolecular structures and molecules of interest in the food

• Ano de defesa: 2019
• Autor(a) principal: Rezende, Jaqueline de Paula
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Universidade Federal de Viçosa; Ciência e Tecnologia de Alimentos
• Palavras-chave em Português: Forças intermoleculares; Nanoestruturas; Detectores; Proteínas transportadoras; Química, Física, Físico-Química e Bioquímica dos Alim. e das Mat.-Primas Alimentares
• Link de acesso: https://locus.ufv.br//handle/123456789/30194

Faced with the constitutional diversity and dynamism of these structures. It S possible to develop new structures with functional characteristics and properties of interest to the food area. The present work was divided into 3 scientific articles and aimed to develop three supramolecular structures, one with sensing capacity and two as nanocarriers of hydrophobic molecules. In the first article, polydiacetylene (PDA) was used in the development of sensors to detect the presence of the antibiotic enrofloxacin (ENRO) in aqueous medium at 30 º C. Sensor nanostructures, so-called nanoblends (NB), were produced from the mixture of PDA, triblock copolymers (TC) and sodium dodecy] sulfate surfactant (SDS). The PDA/ TC/ SDS NBs were able to detect ENRO at a concentration five times lower than the maximum limit allowed by the European Union. The increased sensitivity of the nanosensor containing SDS was attributed to the energy released from the intermolecular interaction between ENRO and SDS, favoring the blue- red colorimetric transition process of the PDA. The response surface methodology showed that both ENRO concentration and SDS influence the colorimetric response (CR) of the sensor, with the maximum CR obtained in [ENRO] = 2 uM and [SDS] = 14.6 mM. The colorimetric transition rate was also evaluated, and NB containing 11.6 mM SDS required only 22 min to reach 40% RC, which is easily visible. The second article presented the thermodynamics and kinetics of formation of bovine lactoferrin (bLF) - epigallocatechin-3-gallate (EGCG) complex obtained by surface plasmon resonance technique (SPR). Fluorescence spectroscopy (FS) was also used to obtain thermodynamic data. Formation of the thermodynamically stable bLF-EGCG complex (AG°spr ≈ -29.00 kJ mol-¹, AG°fs ≈ -26.00 kJ mol-¹) at pH = 7.0 was entropically driven (AH°spr = 14.26, AH°fs = 10.20 kJ mol-¹ and TΔS°spr ≈ 43.00, TΔS°fs ≈ 36.00 kJ mol-¹). As the thermodynamic data of the two techniques were similar, itis suggested that the interaction between the biomolecules occurred in regions close to the tryptophan present in the protein. The increase in temperature favored the stability of the bLF-EGCG complexcausing an increase in the association (ka) and dissociation (ka) constants of the complex. In the third article, the effect of the chemical structure of polyphenol resveratrol (RES) on interaction with human serum albumin (HSA) was evaluated. Thus, the Kinetic and thermodynamic parameters of complex formation between HSA and RES and one of its analogs (RESAn1) were evaluated by SPR. The binding constant (Kb) and kinetic constants of association (ka) and dissociation (kd) showed that the HSA-ResAn1 interaction (Kb(hsa-Resan1)~ 3.94 x 10³ L mol-¹, ka(hsa-Resan1)~1.70 x 10³ M-¹ s-¹, kd(hsa-Resan1)~ 0.43 S-¹) was more intense than HSA-Res (Kb(hsa-Res) ~2.60 x 10³ L mol-¹, ka(sa-Res) ~ 1.20 x 10³M-¹s-¹, kd (hsa-Res)~ 0.46 s-¹). The less polar structure of ResAn1 relative to Res contributes to its access to the hydrophobic regions within the HSA. The formation of both complexes was entropically driven (TΔS° hsa-res ~33.8 and TΔS° hsa-resan1~ 56.4 KJ mol-¹) and favored with increasing temperature. This study showed that small changes in the structure of a bioactive may influence its interaction with the HSA. Regardless of the purpose of the supramolecular structures, the works sought to evaluate and understand the interactions between the molecules that make up the system, as well as between the system and molecules present in their environment. Therefore, the objective of these works was to provide data that contribute to the optimization of the use and application of the developed structures. Keywords: Optical nanosensor. Antibiotic detection. Thermodynamic binding. Kinetic constants. Complex activated.