Shaping substrate selectivity in a broad-spectrum metallo-β-lactamase

Metallo-β-lactamases (MBLs) are the major group of carbapenemases produced by bacterial pathogens. The design of MBL inhibitors has been limited by, among other issues, incomplete knowledge about how these enzymes modulate substrate recognition. While most MBLs are broad-spectrum enzymes, B2 MBLs are exclusive carbapenemases. This narrower substrate profile has been attributed to a sequence insertion present in B2 enzymes that limits accessibility to the active site. In this work, we evaluate the role of sequence insertions naturally occurring in the B2 enzyme Sfh-I and in the broad-spectrum B1 enzyme SPM-1. We engineered a chimeric protein in which the sequence insertion of SPM-1 was replaced by the one present in Sfh-I. The chimeric variant is a selective cephalosporinase, revealing that the substrate profile of MBLs can be further tuned depending on the protein context. These results also show that the stable scaffold of MBLs allows a modular engineering much richer than the one observed in nature.Fil: González, Lisandro J.. Instituto de Biologia Molecular y Celular de Rosario; ArgentinaFil: Stival, Cintia Estefanía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Puzzolo, Juan Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: Moreno, Diego M.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: Aguilar Vila, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; Argentin

Using theoretical calculations to predict the redox potential of mononuclear manganese complexes

The rational design of biomimetic complexes of metalloenzymes involved in redox processes is of great interest in bioinorganic chemistry. Its purpose is to utilize the redox properties of mimics and use them as redox-active catalysts. To obtain efficient artificial catalysts, it is necessary to model structurally and electronically the active site of the enzymes. In particular, for redox catalysis, it is necessary that the biomimetic complexes achieve a certain redox potential so their prediction is a valuable tool to improve the rational design of catalysts with specific properties. In this work we set out to predict the one electron redox potential for a series of mononuclear Mn models of Mn superoxide dismutase enzymes using density functional calculations of low computational cost. We obtained an excellent linear correlation between calculated and experimental redox potentials referenced against the ferrocene/ferrocenium (Fc/Fc+) couple, when solvation effects were included. Additionally, we validated the strategy predicting the redox potentials of two complexes synthesized in our laboratory.Fil: Puzzolo, Juan Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: Drusin, Salvador Iván. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Daier, Veronica Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Biología Molecular y Celular de Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Biología Molecular y Celular de Rosario; ArgentinaFil: Signorella, Sandra Rosanna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: Moreno, Diego Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentin

Versatile Activity of a Copper(II) Complex Bearing a N4‐Tetradentate Schiff Base Ligand with Reduced Oxygen Species

International audienceThe reactivity of the Cu(II) complex of N,N’-bis(pyridin-2-ylmethylene)propane-1,3-diamine (py2pn), [Cu(py2pn)(ClO4)2], toward O2.− and H2O2 has been examined. The complex reacts with O2.− with fast second order kinetics, kMcF=4.05×106 M−1 s−1, employing the Cu(II)/Cu(I) couple proved by spectroscopic detection of the reduced form at low temperature. At −40 °C in DMF, the reaction of the complex with H2O2/Et3N yields an stable end-on Cu(II)-hydroperoxide, with kOOH=0.31 min−1, the formation of which has been established by DFT calculations, electronic and EPR spectra. At room temperature, the end-on Cu(II)-hydroperoxide reacts with a second Cu(II) complex to evolve O2, with kCAT=83.2 M−2 s−1. The Cu(II)-hydroperoxide can mediate phenol oxidation, probably through a trigonal bipyramidal ternary transition state based on DFT analysis, favored over catalase activity when low proportion of catalyst is used. In these reactions, structural constraints imposed by the ligand distort the coordination geometry of the metal and controls reactivity

Designing a comprehensive behaviour change intervention to promote and monitor exclusive use of liquefied petroleum gas stoves for the Household Air Pollution Intervention Network (HAPIN) trial

Introduction Increasing use of cleaner fuels, such as liquefied petroleum gas (LPG), and abandonment of solid fuels is key to reducing household air pollution and realising potential health improvements in low-income countries. However, achieving exclusive LPG use in households unaccustomed to this type of fuel, used in combination with a new stove technology, requires substantial behaviour change. We conducted theory-grounded formative research to identify contextual factors influencing cooking fuel choice to guide the development of behavioural strategies for the Household Air Pollution Intervention Network (HAPIN) trial. The HAPIN trial will assess the impact of exclusive LPG use on air pollution exposure and health of pregnant women, older adult women, and infants under 1 year of age in Guatemala, India, Peru, and Rwanda.Methods Using the Capability, Opportunity, Motivation–Behaviour (COM–B) framework and Behaviour Change Wheel (BCW) to guide formative research, we conducted in-depth interviews, focus group discussions, observations, key informant interviews and pilot studies to identify key influencers of cooking behaviours in the four countries. We used these findings to develop behavioural strategies likely to achieve exclusive LPG use in the HAPIN trial.Results We identified nine potential influencers of exclusive LPG use, including perceived disadvantages of solid fuels, family preferences, cookware, traditional foods, non-food-related cooking, heating needs, LPG awareness, safety and cost and availability of fuel. Mapping formative findings onto the theoretical frameworks, behavioural strategies for achieving exclusive LPG use in each research site included free fuel deliveries, locally acceptable stoves and equipment, hands-on training and printed materials and videos emphasising relevant messages. In the HAPIN trial, we will monitor and reinforce exclusive LPG use through temperature data loggers, LPG fuel delivery tracking, in-home observations and behavioural reinforcement visits.Conclusion Our formative research and behavioural strategies can inform the development, implementation, monitoring and evaluation of theory-informed strategies to promote exclusive LPG use in future stove programmes and research studies.Trial registration number NCT02944682, Pre-results

Comparison of next-generation portable pollution monitors to measure exposure to PM2.5 from household air pollution in Puno, Peru

Assessment of personal exposure to PM2.5 is critical for understanding intervention effectiveness and exposure-response relationships in household air pollution studies. In this pilot study, we compared PM2.5 concentrations obtained from two next-generation personal exposure monitors (the Enhanced Children MicroPEM or ECM; and the Ultrasonic Personal Air Sampler or UPAS) to those obtained with a traditional Triplex Cyclone and SKC Air Pump (a gravimetric cyclone/pump sampler). We co-located cyclone/pumps with an ECM and UPAS to obtain 24-hour kitchen concentrations and personal exposure measurements. We measured Spearmen correlations and evaluated agreement using the Bland-Altman method. We obtained 215 filters from 72 ECM and 71 UPAS co-locations. Overall, the ECM and the UPAS had similar correlation (ECM rho = 0.91 vs UPAS rho = 0.88) and agreement (ECM mean difference of 121.7 mu g/m(3) vs UPAS mean difference of 93.9 mu g/m(3)) with overlapping confidence intervals when compared against the cyclone/pump. When adjusted for the limit of detection, agreement between the devices and the cyclone/pump was also similar for all samples (ECM mean difference of 68.8 mu g/m(3) vs UPAS mean difference of 65.4 mu g/m(3)) and personal exposure samples (ECM mean difference of -3.8 mu g/m(3) vs UPAS mean difference of -12.9 mu g/m(3)). Both the ECM and UPAS produced comparable measurements when compared against a cyclone/pump setup