Imidazolium-based ionic liquids binding to DNA: Mechanical effects and thermodynamics of the interactions.

We performed a robust characterization of the molecular interactions between the DNA molecule and two imidazolium-based ionic liquids (ILs): 1-Butyl-3-methylimidazolium chloride ([bmim]Cl) and 1-Octyl-3-methylimidazolium chloride ([omim]Cl), using single molecule approaches (optical and magnetic tweezers) and bulk techniques (isothermal titration calorimetry and conductivity measurements). Optical and magnetic tweezers allowed us to obtain the changes on the mechanical properties of the DNA complexes formed with both ILs, as well as the relevant physicochemical (binding) parameters of the interaction. Despite the weak binding measured between DNA and the two ILs, we identify a transition on the regime of polymer elasticity of the complexes formed, which results in a relevant DNA compaction for high IL concentrations. In addition, isothermal titration calorimetry and conductivity complemented the single molecule investigation, giving a complete thermodynamic characterization of the interactions and allowing the identification of the most relevant driving forces at various different concentration ranges of the ILs. Based on the results obtained with all the employed techniques, we propose a model for the binding schemes involving DNA and both [bmim]Cl and [omim]Cl.

Doxorubicin hinders DNA condensation promoted by the protein bovine serum albumin (BSA).

In this work, we have studied the interaction between the anticancer drug doxorubicin (doxo) and condensed DNA, using optical tweezers. To perform this task, we use the protein bovine serum albumin (BSA) in the working buffer to mimic two key conditions present in the real intracellular environment: the condensed state of the DNA and the abundant presence of charged macromolecules in the surrounding medium. In particular, we have found that, when doxo is previously intercalated in disperse DNA, the drug hinders the DNA condensation process upon the addition of BSA in the buffer. On the other hand, when bare DNA is firstly condensed by BSA, doxo is capable to intercalate and to unfold the DNA condensates at relatively high concentrations. In addition, a specific interaction between BSA and doxo was verified, which significantly changes the chemical equilibrium of the DNA-doxo interaction. Finally, the presence of BSA in the buffer stabilizes the double-helix structure of the DNA-doxo complexes, preventing partial DNA denaturation induced by the stretching forces.

Depletion interactions and modulation of DNA-intercalators binding: Opposite behavior of the "neutral" polymer poly(ethylene-glycol).

In this work we have investigated the role of high molecular weight poly(ethylene-glycol) 8000 (PEG 8000) in modulating the interactions of the DNA molecule with two hydrophobic compounds: Ethidium Bromide (EtBr) and GelRed (GR). Both compounds are DNA intercalators and are used here to mimic the behavior of more complex DNA ligands such as chemotherapeutic drugs and proteins whose domains intercalate DNA. By means of single-molecule stretching experiments, we have been able to show that PEG 8000 strongly shifts the binding equilibrium between the intercalators and the DNA even at very low concentrations (1% in mass). Additionally, microcalorimetry experiments were performed to estimate the strength of the interaction between PEG and the DNA ligands. Our results suggest that PEG, depending on the system under study, may act as an "inert polymer" with no enthalpic contribution in some processes but, on the other hand, it may as well be an active (non-neutral) osmolyte in the context of modulating the activity of the reactants and products involved in DNA-ligand interactions.

Adição de óleo de palma na dieta sobre a lipidemia e a qualidade do sêmen de bubalinos (Bubalus bubalis) / Addition of palm oil to diet on serum lipid profile and seminal quality of buffaloes (Bubalus bubalis)

O estudo visou investigar o efeito da suplementação dietética com óleo de palma sobre o perfil sérico lipídico e as características seminais de touros bubalinos (Bubalus bubalis), bem como suas correlações. Doze touros foram alocados no Grupo CONT (n=5) ou Grupo ÓLEO (n=7) e receberam alimentação isoproteica composta por silagem de milho e concentrado (milho triturado, farelo de trigo e ureia), com proporção volumoso/concentrado de 50%, durante 130 dias (Períodos 1 e 2). Diferencialmente, óleo de palma foi adicionado ao concentrado (2% MS) do Grupo ÓLEO. Sêmen e sangue foram colhidos quinzenalmente. Houve aumento nas concentrações séricas de colesterol, HDL e lipídios totais nos animais do Grupo ÓLEO, enquanto o período influenciou nas taxas de colesterol, LDL, lipídios totais e VLDL (P<0,05). Houve decréscimo no turbilhonamento e discreta redução na integridade de membranas nos animais do Grupo ÓLEO (P<0,05). Correlações significativas foram encontradas entre triglicerídeos e defeitos menores (r=-0,412; P=0,006), LDL e defeitos totais (r=-0,333; P=0,030), lipídios totais e defeitos menores (r=-0.366; P= 0,017), lipídios totais e defeitos totais (r=-0.309; P= 0,046), e VLDL e viabilidade espermática (r=0,381; P=0,012), apontando efeitos positivos da maior lipidemia na morfologia e na viabilidade espermática. O uso de óleo de palma alterou o perfil lipídico sérico, mas não favoreceu per se os parâmetros seminais relacionados com o potencial de fertilidade dos touros.

The study aimed to investigate the effect of dietary supplementation with palm oil on serum lipid profile, the seminal characteristics of buffaloes (Bubalus bubalis) and the correlations between them. Twelve bulls were divided into Group CONT (n = 5) or Group OIL (n = 7). Animals in both groups were fed with isoproteic diets composed of corn silage and concentrated (ground corn, wheat bran and urea), with 50% forage/concentrate ratio, during 130 days (Periods 1 and 2). Palm oil (2%DM) was added to diet offered to Group OIL. Semen and blood samples were collected every two weeks. Increased serum levels of cholesterol, HDL and total lipids were observed for Group OIL, while the period influenced on cholesterol, LDL, total lipids and VLDL (P<0,05). Treatment decreased gross motility (P<0.05) and slightly reduced sperm membrane integrity (P<0.05) in animals of Group OIL. There were significant correlations between triglycerides and minor defects (r=-0.412, P=0.006), LDL and total defects (r=-0.333, P=0.030), total lipids and minor defects (r=-0.366, P=0.017), VLDL and spermatic viability (r=0.381, P=0.012), and total lipids and totals defects (r=-0.309, P=0.046), highlighting positive effects of higher lipid serum levels on sperm morphology and viability. The incorporation of palm oil in the diet altered the serum lipid profile, but it showed no positive effect on seminal parameters related to the potential of bull fertility.

Microcalorimetric study of the adsorption of lactoferrin in supermacroporous continuous cryogel with immobilized Cu(2+) ions.

The adsorption affinity of lactoferrin from whey in monolithic supermacroporous cryogel was analyzed using equilibrium data adsorptive isothermal titration microcalorimetry to measure thermodynamic information governing the process. Isotherm data was obtained at temperatures of 20, 30 and 40°C, pH 6, 7 and 8, and ionic strength of 200, 600 and 1000mmolL(-1) NaCl. The Langmuir model was fitted to equilibrium data. The binding was tighter at higher temperatures. The adsorption of protein was observed as spontaneous in all cases analyzed. The microcalorimetric study indicated that, in most cases examined, the adsorption of the protein in the matrix was entropy and enthalpy favored and entropy driven. Results provide data to enable the improvement of technical processes for the affinity separation of proteins.