The comprehension of molecular recognition phenomena demands the understanding of the energetic and kinetic processes involved. General equations valid for the thermodynamic analysis of any ...observable that is assessed as a function of the concentration of the involved compounds are described, together with their implementation in the AFFINImeter software. Here, a maximum of three different molecular species that can interact with each other to form an enormous variety of supramolecular complexes are considered. The corrections currently employed to take into account the effects of dilution, volume displacement, concentration errors and those due to external factors, especially in the case of ITC measurements, are included. The methods used to fit the model parameters to the experimental data, and to generate the uncertainties are described in detail. A simulation tool and the so called kinITC analysis to get kinetic information from calorimetric experiments are also presented. An example of how to take advantage of the AFFINImeter software for the global multi-temperature analysis of a system exhibiting cooperative 1:2 interactions is presented and the results are compared with data previously published. Some useful recommendations for the analysis of experiments aimed at studying molecular interactions are provided.
•General equations for thermodynamic analysis of competitive molecular interactions are derived.•“Stoichiometric equilibria” (SE) and “independent sets of sites” (ISS) models are explained.•The implementation of thermodynamics and kinetic models in the AFFINImeter software is described.•Useful recommendations for the analysis of molecular interaction measurements are provided.
Our current understanding of thalamocortical (TC) circuits is largely based on studies investigating so‐called ‘specific’ thalamic nuclei, which receive and transmit sensory‐triggered input to ...specific cortical target areas. TC neurons in these nuclei have a striking point‐to‐point topography and a stereotyped laminar pattern of termination in the cortex, which has made them ideal models to study the organization, plasticity, and development of TC circuits. However, despite their experimental importance, neurons within these nuclei only represent a fraction of all thalamic neurons and do not reflect the diversity of the TC neuron population. Here we review the distinct subtypes of projection neurons that populate the thalamus, both within and across anatomically‐defined nuclei, with regard to differences in their morphology, input/output connectivity and target specificity, as well as more recent findings on their neuron type‐specific gene expression and development. We argue that a detailed understanding of the biology of TC neurons is critical to understand the role of the thalamus in normal and pathological perception, voluntary movement, cognition and attention.
Our current understanding of thalamocortical (TC) circuits is largely based on studies investigating so‐called ‘specific’ thalamic nuclei, which receive and transmit sensory‐triggered input to specific cortical target areas. TC neurons in these nuclei have a striking point‐to‐point topography and a stereotyped laminar pattern of termination in the cortex, which has made them ideal models to study the organization, plasticity, and development of TC circuits.
Whereas synthetically catalyzed nitrogen reduction (N2R) to produce ammonia is widely studied, catalysis to instead produce hydrazine (N2H4) has received less attention despite its considerable ...mechanistic interest. Herein, we disclose that irradiation of a tris(phosphine)borane (P3B) Fe catalyst, P3BFe+, significantly alters its product profile to increase N2H4 versus NH3; P3BFe+ is otherwise known to be highly selective for NH3. We posit a key terminal hydrazido intermediate, P3BFe=NNH2, as selectivity‐determining. Whereas its singlet ground state undergoes protonation to liberate NH3, a low‐lying triplet excited state leads to reactivity at Nα and formation of N2H4. Associated electrochemical and spectroscopic studies establish that N2H4 lies along a unique product pathway; NH3 is not produced from N2H4. Our findings are distinct from the canonical mechanism for hydrazine formation, which proceeds via a diazene (HN=NH) intermediate and showcase light as a tool to tailor selectivity.
Light irradiation of a tris(phosphine)borane iron (P3BFe) catalyst system during nitrogen reduction (N2R) catalysis alters its product selectivity profile, producing significant N2H4 alongside NH3. Only trace N2H4 is otherwise produced. This study provides insight into the dominant factors determining the selectivity of this catalysis and implicates dual reactivity from a singlet ground versus a triplet excited state hydrazido (Fe=NNH2) intermediate.
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The injection of air into the sample cell of an isothermal titration calorimeter containing a liquid provides a rich-in-information signal, with a periodic contribution arising from ...the creation, growing and release of bubbles. The identification and analysis of such contributions allow the accurate determination of the surface tension of the target liquid.
Air is introduced at a constant rate into the sample cell of the calorimeter containing either a pure liquid or a solution. The resulting calorimetric signal is analyzed by a new algorithm, which is implemented into a computational code.
The thermal power generated by our experiments is often noisy, thus hiding the periodic signal arising from the bubbles’ formation and release. The new algorithm was tested with a range of different types of calorimetric raw data, some of them apparently being just noise. In all cases, the contribution of the bubbles to the signal was isolated and the corresponding period was successfully determined in an automated way. It is also shown that two reference measurements suffice to calibrate the instrument at a given temperature, regardless the injection rate, allowing the direct determination of surface tension values for the liquid contained in the sample cell.
Fluid interface calorimetry Garrido, Pablo F.; Bastos, Margarida; Velázquez-Campoy, Adrián ...
Journal of colloid and interface science,
08/2021, Volume:
596
Journal Article
Peer reviewed
Open access
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Amphiphilic molecules spontaneously adsorb to fluid polar-nonpolar interfaces. The timescale of such adsorption depends on the molecular size and structure of the solute. This process ...should be accompanied by a power heat exchange that could be detected by commercial isothermal calorimeters.
Air is injected in the bulk of different aqueous solutions contained in the sample cell of an isothermal titration calorimeter. The formation of the resulting bubbles leads to a liquid/air interface to which the solute molecules spontaneously adsorb. Continuous injection experiments to produce multiple bubbles as well as experiments with static bubbles stand from the capillary tip, aiming to observe slow adsorption processes, were performed.
The power associated with the formation, growth and release of air bubbles in different liquids was measured. Different independent contributions that can be associated to the pressure change in the gas phase, the evaporation-condensation of the solvent, the increase of interfacial area, the change in the heat capacity of the sample cell content, and the release of the bubble were observed. The periodic pattern produced by the continuous injection of air at a constant rate is used to determine the surface tension of different liquids, including solutions of different molecules and (bio)macromolecules.
Maternal mortality is a critical indicator of healthcare quality, and in Mexico, this has become increasingly concerning due to the stagnation in its decline, alongside a concurrent increase in ...cesarean section (C-section) rates. This study characterizes maternal deaths in Mexico, focusing on estimating the association between obstetric risk profiles, cause of death, and mode of delivery.
Utilizing a retrospective observational design, 4,561 maternal deaths in Mexico from 2010-2014 were analyzed. Data were sourced from the Deliberate Search and Reclassification of Maternal Deaths database, alongside other national databases. An algorithm was developed to extract the Robson Ten Group Classification System from clinical summaries text, facilitating a nuanced analysis of C-section rates. Information on the reasons for the performance of a C-section was also obtained. Logistic regression and multinomial logistic regression models were used to estimate the relation between obstetric risk factors, mode of delivery and causes of maternal death, adjusting for covariates.
Among maternal deaths in Mexico from 2010-2014, 47.1% underwent a C-section, with a significant history of previous C-sections observed in 31.4% of these cases, compared to 17.4% for vaginal deliveries (p<0.001). Early prenatal care in the first trimester was more common in C-section cases (46.8%) than in vaginal deliveries (38.3%, p<0.001). A stark contrast was noted in the place of death, with 82.4% of post-C-section deaths occurring in public institutions versus 69.1% following vaginal births. According to Robson's classification, the highest C-section rates were in Group 4 (67.2%, p<0.001) and Group 8 (66.9%, p<0.001). Logistic regression analysis revealed no significant difference in the odds of receiving a C-section in private versus other settings after adjusting for Robson criteria (OR: 1.21; 95% CI: 0.92, 1.60). A prior C-section significantly increased the likelihood of another (OR: 2.38; CI 95%: 2.01, 2.81). The analysis also indicated C-sections were significantly tied to deaths from hypertensive disorders (RRR = 1.25, 95% CI 1.12, 1.40). In terms of indications, 6.3% of C-sections were performed under inadequate indications, while the indication was not identifiable in 33.1% of all C-sections.
This study highlights a significant overuse of C-sections among maternal deaths in Mexico (2010-2014), revealed through the Robson classification and ana analysis of the reported indications for the procedure. It underscores the need for revising clinical decision-making to promote evidence-based guidelines and favor vaginal deliveries when possible. High C-section rates, especially noted disparities between private and public sectors, suggest economic and non-clinical factors may be at play. The importance of accurate data systems and further research with control groups to understand C-section practices' impact on maternal health is emphasized.
Water oxidation to dioxygen is one of the key reactions that need to be mastered for the design of practical devices based on water splitting with sunlight. In this context, water oxidation catalysts ...based on first‐row transition metal complexes are highly desirable due to their low cost and their synthetic versatility and tunability through rational ligand design. A new family of dianionic bpy‐amidate ligands of general formula H2LNn− (LN is 2,2′‐bipyridine‐6,6′‐dicarboxamide) substituted with phenyl or naphthyl redox non‐innocent moieties is described. A detailed electrochemical analysis of (L4)Cu2− (L4=4,4′‐((2,2′‐bipyridine‐6,6′‐dicarbonyl)bis(azanediyl))dibenzenesulfonate) at pH 11.6 shows the presence of a large electrocatalytic wave for water oxidation catalysis at an η=830 mV. Combined experimental and computational evidence, support an all ligand‐based process with redox events taking place at the aryl‐amide groups and at the hydroxido ligands.
A family of Cu‐based complexes bearing dianionic bpy‐amidate ligands have been prepared and characterized by spectroscopic and electrochemical techniques. The new complexes are capable of performing water oxidation catalysis at overpotentials between 557–830 mV pH 11.6. A detailed electrocatalytic study in combination with computational calculations revealed the all ligand‐based nature of the electron transfer processes involved in the catalytic cycle.
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A handful of singular structures and laws can be observed in nature. They are not always evident but, once discovered, it seems obvious how to take advantage of them. In chemistry, ...the discovery of reproducible patterns stimulates the imagination to develop new functional materials and technological or medical applications. Two clear examples are helical structures at different levels in biological polymers as well as ring and spherical structures of different size and composition. Rings are intuitively observed as holes able to thread elongated structures. A large number of real and fictional stories have rings as inanimate protagonists. The design, development or just discovering of a special ring has often been taken as a symbol of power or success. Several examples are the Piscatory Ring wore by the Pope of the Catholic Church, the NBA Championship ring and the One Ring created by the Dark Lord Sauron in the epic story The Lord of the Rings. In this work, we reveal the power of another extremely powerful kind of rings to fight against the pandemic which is currently affecting the whole world. These rings are as small as ~1 nm of diameter and so versatile that they are able to participate in the attack of viruses, and specifically SARS-CoV-2, in a large range of different ways. This includes the encapsulation and transport of specific drugs, as adjuvants to stabilize proteins, vaccines or other molecules involved in the infection, as cholesterol trappers to destabilize the virus envelope, as carriers for RNA therapies, as direct antiviral drugs and even to rescue blood coagulation upon heparin treatment.
“One ring to rule them all. One ring to find them. One ring to bring them all and in the darkness bind them.” J. R. R. Tolkien.
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