Proton and Li-Ion Permeation through Graphene with Eight-Atom-Ring Defects

Defect-free graphene is impermeable to gases and liquids but highly permeable to thermal protons. Atomic-scale defects such as vacancies, grain boundaries and Stone-Wales defects are predicted to enhance graphene's proton permeability and may even allow small ions through, whereas larger species such as gas molecules should remain blocked. These expectations have so far remained untested in experiment. Here we show that atomically thin carbon films with a high density of atomic-scale defects continue blocking all molecular transport, but their proton permeability becomes ~1,000 times higher than that of defect-free graphene. Lithium ions can also permeate through such disordered graphene. The enhanced proton and ion permeability is attributed to a high density of 8-carbon-atom rings. The latter pose approximately twice lower energy barriers for incoming protons compared to the 6-atom rings of graphene and a relatively low barrier of ~0.6 eV for Li ions. Our findings suggest that disordered graphene could be of interest as membranes and protective barriers in various Li-ion and hydrogen technologies

Un examen actualizado de la percepción de las barreras para la implementación de la farmacogenómica y la utilidad de los pares fármaco/gen en América Latina y el Caribe

La farmacogenómica (PGx) se considera un campo emergente en los países en desarrollo. La investigación sobre PGx en la región de América Latina y el Caribe (ALC) sigue siendo escasa, con información limitada en algunas poblaciones. Por lo tanto, las extrapolaciones son complicadas, especialmente en poblaciones mixtas. En este trabajo, revisamos y analizamos el conocimiento farmacogenómico entre la comunidad científica y clínica de ALC y examinamos las barreras para la aplicación clínica. Realizamos una búsqueda de publicaciones y ensayos clínicos en este campo en todo el mundo y evaluamos la contribución de ALC. A continuación, realizamos una encuesta regional estructurada que evaluó una lista de 14 barreras potenciales para la aplicación clínica de biomarcadores en función de su importancia. Además, se analizó una lista emparejada de 54 genes/fármacos para determinar una asociación entre los biomarcadores y la respuesta a la medicina genómica. Esta encuesta se comparó con una encuesta anterior realizada en 2014 para evaluar el progreso en la región. Los resultados de la búsqueda indicaron que los países de América Latina y el Caribe han contribuido con el 3,44% del total de publicaciones y el 2,45% de los ensayos clínicos relacionados con PGx en todo el mundo hasta el momento. Un total de 106 profesionales de 17 países respondieron a la encuesta. Se identificaron seis grandes grupos de obstáculos. A pesar de los continuos esfuerzos de la región en la última década, la principal barrera para la implementación de PGx en ALC sigue siendo la misma, la "necesidad de directrices, procesos y protocolos para la aplicación clínica de la farmacogenética/farmacogenómica". Las cuestiones de coste-eficacia se consideran factores críticos en la región. Los puntos relacionados con la reticencia de los clínicos son actualmente menos relevantes. Según los resultados de la encuesta, los pares gen/fármaco mejor clasificados (96%-99%) y percibidos como importantes fueron CYP2D6/tamoxifeno, CYP3A5/tacrolimus, CYP2D6/opioides, DPYD/fluoropirimidinas, TMPT/tiopurinas, CYP2D6/antidepresivos tricíclicos, CYP2C19/antidepresivos tricíclicos, NUDT15/tiopurinas, CYP2B6/efavirenz y CYP2C19/clopidogrel. En conclusión, aunque la contribución global de los países de ALC sigue siendo baja en el campo del PGx, se ha observado una mejora relevante en la región. La percepción de la utilidad de las pruebas PGx en la comunidad biomédica ha cambiado drásticamente, aumentando la concienciación entre los médicos, lo que sugiere un futuro prometedor en las aplicaciones clínicas de PGx en ALC.Pharmacogenomics (PGx) is considered an emergent field in developing countries. Research on PGx in the Latin American and the Caribbean (LAC) region remains scarce, with limited information in some populations. Thus, extrapolations are complicated, especially in mixed populations. In this paper, we reviewed and analyzed pharmacogenomic knowledge among the LAC scientific and clinical community and examined barriers to clinical application. We performed a search for publications and clinical trials in the field worldwide and evaluated the contribution of LAC. Next, we conducted a regional structured survey that evaluated a list of 14 potential barriers to the clinical implementation of biomarkers based on their importance. In addition, a paired list of 54 genes/drugs was analyzed to determine an association between biomarkers and response to genomic medicine. This survey was compared to a previous survey performed in 2014 to assess progress in the region. The search results indicated that Latin American and Caribbean countries have contributed 3.44% of the total publications and 2.45% of the PGx-related clinical trials worldwide thus far. A total of 106 professionals from 17 countries answered the survey. Six major groups of barriers were identified. Despite the region’s continuous efforts in the last decade, the primary barrier to PGx implementation in LAC remains the same, the “need for guidelines, processes, and protocols for the clinical application of pharmacogenetics/pharmacogenomics”. Cost-effectiveness issues are considered critical factors in the region. Items related to the reluctance of clinicians are currently less relevant. Based on the survey results, the highest ranked (96%–99%) gene/drug pairs perceived as important were CYP2D6/tamoxifen, CYP3A5/tacrolimus, CYP2D6/opioids, DPYD/fluoropyrimidines, TMPT/thiopurines, CYP2D6/tricyclic antidepressants, CYP2C19/tricyclic antidepressants, NUDT15/thiopurines, CYP2B6/efavirenz, and CYP2C19/clopidogrel. In conclusion, although the global contribution of LAC countries remains low in the PGx field, a relevant improvement has been observed in the region. The perception of the usefulness of PGx tests in biomedical community has drastically changed, raising awareness among physicians, which suggests a promising future in the clinical applications of PGx in LAC

On the Chemistry and Diffusion of Hydrogen in the Interstitial Space of Layered Crystals h-BN, MoS₂, and Graphite

Recent experiments have demonstrated transport and separation of hydrogen isotopes in layered materials, such as hexagonal boron nitride and molybdenum disulphide. Here, based on first-principles calculations combined with well-tempered metadynamics simulations, we report the chemical interactions and mobility of protons (H+) and protium (H atoms) in the interstitial space of these layered materials. We show that both H+ and H can be transported between the layers of h-BN and MoS2 with low free energy barriers, while they are immobilized in graphite, in accordance with the experimental observations. In h-BN and MoS2, the transport mechanism involves a hopping process between the adjacent layers, which is assisted by the low- energy phonon shear modes. Defects present in MoS2 suppress the transport and act as traps for H species.</div

On the Chemistry and Mobility of Hydrogen in the Interstitial Space of Layered Crystals H-BN, MoS2 and Graphite

Recent experiments have demonstrated transport and separation of hydrogen isotopes in layered materials, such as hexagonal boron nitride and molybdenum disulphide. Here, based on first-principles calculations combined with well-tempered metadynamics simulations, we report the chemical interactions and mobility of protons (H+) and protium (H atoms) in the interstitial space of these layered materials. We show that both H+ and H can be transported between the layers of h-BN and MoS2 with low free energy barriers, while they are immobilized in graphite, in accordance with the experimental observations. In h-BN and MoS2, the transport mechanism involves a hopping process between the adjacent layers, which is assisted by the low- energy phonon shear modes. Defects present in MoS2 suppress the transport and act as traps for H species.</div

Scalable and efficient separation of hydrogen isotopes using graphene-based electrochemical pumping

Thousands of tons of isotopic mixtures are processed annually for heavy-water production and tritium decontamination. The existing technologies remain extremely energy intensive and require large capital investments. New approaches are needed to reduce the industry's footprint. Recently, micron-size crystals of graphene were shown to act as efficient sieves for hydrogen isotopes pumped through graphene electrochemically. Here we report a fully-scalable approach, using graphene obtained by chemical vapor deposition, which allows a proton-deuteron separation factor of ca. 8, despite cracks and imperfections. The energy consumption is projected to be orders of magnitude smaller with respect to existing technologies. A membrane based on 30 m2 of graphene, a readily accessible amount, could provide a heavy-water output comparable to that of modern plants. Even higher efficiency is expected for tritium separation. With no fundamental obstacles for scaling up, the technology's simplicity, efficiency and green credentials call for consideration by the nuclear and related industries