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11
result(s) for
"Armijo, Victor"
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Low Financial Risk of Default and Productive Use of Assets Through Hidden Markov Models
by
Vasquez, William
,
Sandoval Genaro
,
Rodríguez María
in
Asset allocation
,
bank solvency
,
Capital requirements
2025
This paper analyzes solvency dynamics in Ecuador’s mutualist segment by modeling the joint behavior of the productive-assets-to-total-assets ratio (PATR) and portfolio-specific delinquency rates. Using monthly supervisory data from the Superintendencia de Economía Popular y Solidaria (SEPS) for the full universe of four mutualist institutions (2022–2025), we estimate a multivariate Gaussian Hidden Markov Model on system-level aggregates. The model identifies latent regimes that summarize configurations of asset productivity and segmented credit risk, distinguishing relatively sound conditions from episodes of heightened vulnerability. Model selection is based on information criteria, complemented by convergence checks, distributional diagnostics, and alternative covariance specifications to assess robustness. The approach is explicitly framed as diagnostic rather than causal or prescriptive: it does not replace simple thresholds nor calibrate capital buffers, but organizes supervisory information into interpretable solvency states with associated frequencies and expected durations. The framework is transparent and reproducible and provides a baseline for future extensions with longer samples and richer covariates.
Journal Article
Advancing macromolecular structure determination with microsecond X-ray pulses at a 4th generation synchrotron
by
Basu, Shibom
,
Oscarsson, Marcus
,
Beteva, Antonia
in
631/535
,
631/535/1266/1265
,
Biochemistry, Molecular Biology
2025
Serial macromolecular crystallography has become a powerful method to reveal room temperature structures of biological macromolecules and perform time-resolved studies. ID29, a flagship beamline of the ESRF 4th generation synchrotron, is the first synchrotron beamline in the world capable of delivering high brilliance microsecond X-ray pulses at high repetition rate for the structure determination of biological macromolecules at room temperature. The cardinal combination of microsecond exposure times, innovative beam characteristics and adaptable sample environment provides high quality complete data, even from an exceptionally small amount of crystalline material, enabling what we collectively term serial microsecond crystallography (SµX). After validating the use of different sample delivery methods with various model systems, we applied SµX to an integral membrane receptor, where only a few thousands diffraction images were sufficient to obtain a fully interpretable electron density map for the antagonist istradefylline-bound A
2A
receptor conformation, providing access to the antagonist binding mode. SµX, as demonstrated at ID29, will quickly find its broad applicability at upcoming 4th generation synchrotron sources worldwide and opens a new frontier in time-resolved SµX.
Serial macromolecular crystallography has become a powerful method to reveal room-temperature structures of biological macromolecules and perform time-resolved studies, however, the experiments remain complex and challenging for broader applications. Here, the authors develop serial microsecond crystallography using high-brilliance, high-repetition-rate X-ray pulses at the newly constructed ID29 beamline of the ESRF-EBS 4th generation synchrotron, featuring microsecond exposure times, innovative beam characteristics, adaptable sample environment, and high-quality complete data.
Journal Article
EasyGrid: A versatile platform for automated cryo-EM sample preparation and quality control
by
Deckers, Thibault
,
Eustermann, Sebastian
,
Babenko, Anastasiia
in
Automation
,
Electron microscopy
,
Freezing
2024
Imaging biological macromolecules in their native state with single-particle cryo-electron microscopy (cryo-EM) or in situ cryo-electron tomography (cryo-ET) requires optimized approaches for the preparation and vitrification of biological samples. Here, we describe EasyGrid, a versatile technology enabling systematic, tailored and advanced sample preparation for cellular and structural biology. This automated, standalone platform combines in-line plasma treatment, microfluidic dispensing, blot-less sample spreading, jet-based vitrification and on-the-fly grid quality control using light interferometry to streamline cryo-EM sample optimization. With EasyGrid, we optimized grid preparation for different purified macromolecular complexes and subsequently determined their structure with cryo- EM. We also demonstrated how the platform allows better vitrification of large, mammalian cells compared to standard plunge-freezing. Automated sample preparation with EasyGrid establishes an advanced, high-throughput platform for both single-particle cryo-EM and cellular cryo-ET sample preparation.Competing Interest StatementGergely Papp, Florent Cipriani - pending patent WO 2020/058140 Gergely Papp - European patent application 23 209 700.6
Optimization of the Extraction of Antioxidant Compounds from Roselle Hibiscus Calyxes (Hibiscus sabdariffa), as a Source of Nutraceutical Beverages
by
Villalobos-Vega, María José
,
Álvarez-Valverde, Víctor
,
Jiménez-Bonilla, Pablo
in
Acids
,
Aging
,
Antioxidants
2023
Secondary metabolites from Hibiscus sabdariffa have been used to prevent different diseases. Roselle Hibiscus is known for being rich in phenolic bioactive compounds. The extraction conditions are directly related to the chemical composition and then to the overall bioactivity of the extract. In this study, a Box-Behnken experimental design has been used to optimize the antioxidant activity, considering four variables: ethanol:water ratio, temperature, extraction time, and solvent:solid ratio. The experiment comprises 27 experiments and 3 repetitions at the central point. The results are described by surface response analysis and a second-degree polynomial equation. The model explains 87% of the variation in the response. The maximum antioxidant activity is yielded when 1% solids are extracted in 35.5% ethanol at 60 °C for 33 min. Finally, a nutritional functional supplement of 495 µmol Trolox Equivalent (TE) antioxidant capacity was prepared with the optimized extract.
Journal Article
Altered microbial bile acid metabolism exacerbates T cell-driven inflammation during graft-versus-host disease
2024
Microbial transformation of bile acids affects intestinal immune homoeostasis but its impact on inflammatory pathologies remains largely unknown. Using a mouse model of graft-versus-host disease (GVHD), we found that T cell-driven inflammation decreased the abundance of microbiome-encoded bile salt hydrolase (BSH) genes and reduced the levels of unconjugated and microbe-derived bile acids. Several microbe-derived bile acids attenuated farnesoid X receptor (FXR) activation, suggesting that loss of these metabolites during inflammation may increase FXR activity and exacerbate the course of disease. Indeed, mortality increased with pharmacological activation of FXR and decreased with its genetic ablation in donor T cells during mouse GVHD. Furthermore, patients with GVHD after allogeneic hematopoietic cell transplantation showed similar loss of BSH and the associated reduction in unconjugated and microbe-derived bile acids. In addition, the FXR antagonist ursodeoxycholic acid reduced the proliferation of human T cells and was associated with a lower risk of GVHD-related mortality in patients. We propose that dysbiosis and loss of microbe-derived bile acids during inflammation may be an important mechanism to amplify T cell-mediated diseases.
Graft-versus-host disease, a T cell-driven inflammatory condition, is associated with altered microbial bile acid metabolism in both mice and humans and this is linked to outcomes.
Journal Article
Functionalization of stable fluorescent nanodiamonds towards reliable detection of biomarkers for Alzheimer’s disease
by
Alvarez, Alejandra R.
,
Rodriguez, Enrique
,
Bhuyan, Heman
in
Aggregates
,
Alzheimer Disease - diagnosis
,
Alzheimer's disease
2018
Background
Stable and non-toxic fluorescent markers are gaining attention in molecular diagnostics as powerful tools for enabling long and reliable biological studies. Such markers should not only have a long half-life under several assay conditions showing no photo bleaching or blinking but also, they must allow for their conjugation or functionalization as a crucial step for numerous applications such as cellular tracking, biomarker detection and drug delivery.
Results
We report the functionalization of stable fluorescent markers based on nanodiamonds (NDs) with a bifunctional peptide. This peptide is made of a cell penetrating peptide and a six amino acids long β-sheet breaker peptide that is able to recognize amyloid β (Aβ) aggregates, a biomarker for the Alzheimer disease. Our results indicate that functionalized NDs (fNDs) are not cytotoxic and can be internalized by the cells. The fNDs allow ultrasensitive detection (at picomolar concentrations of NDs) of in vitro amyloid fibrils and amyloid aggregates in AD mice brains.
Conclusions
The fluorescence of functionalized NDs is more stable than that of fluorescent markers commonly used to stain Aβ aggregates such as Thioflavin T. These results pave the way for performing ultrasensitive and reliable detection of Aβ aggregates involved in the pathogenesis of the Alzheimer disease.
Journal Article
Interaction of heat shock protein 70 with membranes depends on the lipid environment
by
Armijo, Gabrielle
,
Cauvi, David M.
,
Kim, Judy
in
Amino Acid Sequence
,
Biochemistry
,
Biomedical and Life Sciences
2014
Heat shock proteins (hsp) are well recognized for their protein folding activity. Additionally, hsp expression is enhanced during stress conditions to preserve cellular homeostasis. Hsp are also detected outside cells, released by an active mechanism independent of cell death. Extracellular hsp appear to act as signaling molecules as part of a systemic response to stress. Extracellular hsp do not contain a consensus signal for their secretion via the classical ER-Golgi compartment. Therefore, they are likely exported by an alternative mechanism requiring translocation across the plasma membrane. Since Hsp70, the major inducible hsp, has been detected on surface of stressed cells, we propose that membrane interaction is the first step in the export process. The question that emerges is how does this charged cytosolic protein interact with lipid membranes? Prior studies have shown that Hsp70 formed ion conductance pathways within artificial lipid bilayers. These early observations have been extended herewith using a liposome insertion assay. We showed that Hsp70 selectively interacted with negatively charged phospholipids, particularly phosphatidyl serine (PS), within liposomes, which was followed by insertion into the lipid bilayer, forming high-molecular weight oligomers. Hsp70 displayed a preference for less fluid lipid environments and the region embedded into the lipid membrane was mapped toward the Cterminus end of the molecule. The results from our studies provide evidence of an unexpected ability of a large, charged protein to become inserted into a lipid membrane. This observation provides a new paradigm for the interaction of proteins with lipid environments. In addition, it may explain the export mechanism of an increasing number of proteins that lack the consensus secretory signals.
Journal Article
Diversity and effective population size of four horse breeds from microsatellite DNA markers in South-Central Mexico
by
Arellano-Vera, Williams
,
Velazquez, Miguel Abraham
,
Parra-Bracamonte, Gaspar Manuel
in
Animal breeding
,
Animal populations
,
Animals
2017
The South-Central region of Mexico has experienced a sizeable introduction of purebred horses for recreational aims. A study was designed to assess effective population sizes and genetic diversity and to verify the genetic integrity of four horse breeds. Using a 12-microsatellite panel, Quarter Horse, Azteca, Thoroughbred and Creole (CRL) horses were sampled and analysed for diversity and genetic structure. Genetic diversity parameters showed high numbers of heterozygous horses but small effective population sizes in all breeds. Population structure results suggested some degree of admixture of CRL with the other reference breeds. The highly informative microsatellite panel allowed the verification of diversity in introduced horse populations and the confirmation of small effective population sizes, which suggests a risk for future breed integrity.
Journal Article