Cell
membranes are one of the main targets of oxidative processes
mediated by reactive oxygen species (ROS). These chemical species
interact with unsaturated fatty acids of membrane lipids, triggering
an autocatalytic chain reaction, producing lipid hydroperoxides (LOOHs)
as the first relatively stable product of the ROS-mediated lipid peroxidation
(LPO) process. Numerous biophysical and computational studies have
been carried out to elucidate the LPO impact on the structure and
organization of lipid membranes. However, although LOOHs are the major
primary product of LPO of polyunsaturated fatty acids (PUFAs), to
the best of our knowledge, there is no experimental evidence on the
effects of the accumulation of these LPO byproducts on the electrical
properties and the underlying dynamics of lipid membranes. In this
work, bilayer lipid membranes (BLMs) containing 1-palmitoyl-2–oleoyl-sn-glycero-3-phosphocoline (POPC) with increasing hydroperoxidized
POPC (POPC-OOH) molar proportions (BLMPC/PC‑OOH)
are used as model membranes to investigate the effect of LOOH-mediated
LPO propagation on the electrical behavior of lipid bilayers. Voltage-induced
ion current signals are analyzed by applying the fractal method of
power spectrum density (PSD) analysis. We experimentally prove that,
when certain LOOH concentration and energy threshold are overcome,
oxidized membranes evolve toward a critical state characterized by
the emergence of non-linear electrical behavior dynamics and the pore-type
metastable structures formation. PSD analysis shows that temporal
dynamics exhibiting “white” noise (non-time correlations)
reflects a linear relationship between the input and output signals,
while long-term correlations (β > 0.5) begin to be observed
closely to the transition (critical point) from linear (Ohmic) to
nonlinear (non-Ohmic) behavior. The generation of lipid pores appears
to arise as an optimized energy dissipation mechanism based on the
system’s ability to self-organize and generate ordered structures
capable of dissipating energy gradients more efficiently under stressful
oxidative conditions.
The RDL receptor
is one of the most relevant protein targets for
insecticide molecules. It belongs to the pentameric ligand-gated ion
channel (pLGIC) family. Given that the experimental structures of
pLGICs are difficult to obtain, homology modeling has been extensively
used for these proteins, particularly for the RDL receptor. However,
no detailed assessments of the usefulness of homology models for virtual
screening (VS) have been carried out for pLGICs. The aim of this study
was to evaluate which are the determinant factors for a good VS performance
using RDL homology models, specially analyzing the impact of the template
conformational state. Fifteen RDL homology models were obtained based
on different pLGIC templates representing the closed, open, and desensitized
states. A retrospective VS process was performed on each model, and
their performance in the prioritization of active ligands was assessed.
In addition, the three best-performing models among each of the conformations
were subjected to molecular dynamics simulations (MDS) in complex
with a representative active ligand. The models showed variations
in their VS performance parameters that were related to the structural
properties of the binding site. VS performance tended to improve in
more constricted binding cavities. The best performance was obtained
with a model based on a template in the closed conformation. MDS confirmed
that the closed model was the one that best represented the interactions
with an active ligand. These results imply that different templates
should be evaluated and the structural variations between their channel
conformational states should be specially examined, providing guidelines
for the application of homology modeling for VS in other proteins
of the pLGIC family.
Fluralaner is a relatively new insecticide belonging to the isoxazoline group, whose action mechanism involves the blocking of GABA A -receptors in the insect nervous system. Because of its high hydrophobicity, fluralaner could bioaccumulate and reach toxic local concentrations. Since there are no data available about the penetration and persistence of isoxazolines in biological membranes, we intend to evaluate fluralaner permanence as a pollutant by using model membranes. We used experimental and in silico models to characterize the incorporation of fluralaner into the lipid phase at different packing states. We determined its impact in the membrane structure and organization. Our results confirm that fluralaner is capable of penetrating, holding, and accumulating in the lipid membrane and provide details on its precise location and orientation. These properties would allow fluralaner to reach high local concentrations in different membranes and organs, which could be dangerous for vertebrate organisms if its handling is not properly controlled.
Resumen: Los contenidos de naturaleza de la ciencia (NOS, por sus siglas en inglés) se pueden clasificar en tres ejes: epistemológico, histórico y sociológico. La investigación didáctica ha priorizado el eje epistemológico y persiste un debate sobre qué contenidos de NOS enseñar y cómo hacerlo. El objetivo del trabajo es analizar las concepciones y prácticas de enseñanza declaradas sobre aspectos sociológicos de la NOS en docentes de Metodología de la Investigación en Ciencias Naturales de la ciudad de Córdoba, Argentina. Se utilizó una metodología cualitativa con entrevistas semiestructuradas. Los docentes entrevistados/as enfatizan la enseñanza explícita del eje epistemológico. Reconocen las influencias mutuas entre ciencia y sociedad, aunque persisten algunas concepciones ingenuas, particularmente respecto a la imagen del científico/a. En cuanto a las prácticas de enseñanza, se evidenció que las temáticas sociológicas se trabajan en el aula, a veces de manera planificada y otras de manera espontánea.
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