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.

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.

Technical note and clinical instructions for Acute Kidney Injury (AKI) in patients with Covid-19: Brazilian Society of Nephrology and Brazilian Association of Intensive Care Medicine.

We produced this document to bring pertinent information to the practice of nephrology, as regards to the renal involvement with COVID-19, the management of acute kidney injury cases, and practical guidance on the provision of dialysis support.As information on COVID-19 evolves at a pace never before seen in medical science, these recommendations, although based on recent scientific evidence, refer to the present moment. The guidelines may be updated when published data and other relevant information become available.

An optical sensor for the detection and quantification of lidocaine in cocaine samples.

An optical sensor (OS) was synthesized by mixing 10,12-pentacosadiinoic acid (PDA) with a triblock copolymer for use in the detection/quantification of lidocaine (LD) in seized cocaine hydrochloride (seized CH) samples. In the presence of LD, the OS presented a chromatic transition from blue to red, while no chromatic transition was observed for other typical cocaine adulterants or cocaine hydrochloride. Isothermal titration calorimetry analysis revealed specific interactions between the PDA molecules of the OS and the LD molecules, with these interactions being enthalpically favorable (-1.20 to -36.7 kJ mol-1). Therefore, the OS color change only occurred when LD was present in the sample, making the OS selective for LD. Consequently, LD was successfully detected in seized CH samples, irrespective of the type of adulteration. The OS was used for the quantification of LD in seized CH samples containing different adulterants, providing a linear range of 0.0959 to 0.225% (w/w), a precision of 7.2%, an accuracy ranging from -10 to 10%, and limits of detection and quantification of 0.0110% (w/w) and 0.0334% (w/w), respectively.

Technical note and clinical instructions for Acute Kidney Injury (AKI) in patients with Covid-19: Brazilian Society of Nephrology and Brazilian Association of Intensive Care Medicine / Nota técnica e orientações clínicas sobre a Injúria Renal Aguda (IRA) em pacientes com Covid-19: Sociedade Brasileira de Nefrologia e Associação de Medicina Intensiva Brasileira

ABSTRACT We produced this document to bring pertinent information to the practice of nephrology, as regards to the renal involvement with COVID-19, the management of acute kidney injury cases, and practical guidance on the provision of dialysis support.As information on COVID-19 evolves at a pace never before seen in medical science, these recommendations, although based on recent scientific evidence, refer to the present moment. The guidelines may be updated when published data and other relevant information become available.

RESUMO Este documento foi desenvolvido para trazer informações pertinentes à prática nefrológica em relação ao conhecimento sobre o acometimento renal da COVID-19, conduta frente aos casos de injúria renal aguda e orientações práticas sobre a provisão do suporte dialítico.Como as informações sobre a COVID-19 evoluem a uma velocidade jamais vista na ciência médica, as orientações apresentadas, embora baseadas em evidências científicas recentes, referem-se ao momento presente. Essas orientaços poderão ser atualizadas à medida que dados publicados e outras informações relevantes venham a ser disponibilizadas.

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.