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Biochimica Et Biophysica Acta.... Apr 2023
Topics: Protons; Hydrogen-Ion Concentration; Electron Transport
PubMed: 36775006
DOI: 10.1016/j.bbamem.2023.184139 -
Pflugers Archiv : European Journal of... Apr 2024
Topics: Protons
PubMed: 38460007
DOI: 10.1007/s00424-024-02942-z -
FEMS Microbiology Reviews Nov 2022The Earth is home to environments characterized by low pH, including the gastrointestinal tract of vertebrates and large areas of acidic soil. Most bacteria are... (Review)
Review
The Earth is home to environments characterized by low pH, including the gastrointestinal tract of vertebrates and large areas of acidic soil. Most bacteria are neutralophiles, but can survive fluctuations in pH. Herein, we review how Escherichia, Salmonella, Helicobacter, Brucella, and other acid-resistant Gram-negative bacteria adapt to acidic environments. We discuss the constitutive and inducible defense mechanisms that promote survival, including proton-consuming or ammonia-producing processes, cellular remodeling affecting membranes and chaperones, and chemotaxis. We provide insights into how Gram-negative bacteria sense environmental acidity using membrane-integrated and cytosolic pH sensors. Finally, we address in more detail the powerful proton-consuming decarboxylase systems by examining the phylogeny of their regulatory components and their collective functionality in a population.
Topics: Animals; Protons; Bacteria; Acids; Adaptation, Physiological; Cell Membrane; Hydrogen-Ion Concentration
PubMed: 35906711
DOI: 10.1093/femsre/fuac037 -
Nature Reviews. Cancer Dec 2023Cancers undergo sequential changes to proton (H) concentration and sensing that are consequences of the disease and facilitate its further progression. The impact of... (Review)
Review
Cancers undergo sequential changes to proton (H) concentration and sensing that are consequences of the disease and facilitate its further progression. The impact of protonation state on protein activity can arise from alterations to amino acids or their titration. Indeed, many cancer-initiating mutations influence pH balance, regulation or sensing in a manner that enables growth and invasion outside normal constraints as part of oncogenic transformation. These cancer-supporting effects become more prominent when tumours develop an acidic microenvironment owing to metabolic reprogramming and disordered perfusion. The ensuing intracellular and extracellular pH disturbances affect multiple aspects of tumour biology, ranging from proliferation to immune surveillance, and can even facilitate further mutagenesis. As a selection pressure, extracellular acidosis accelerates disease progression by favouring acid-resistant cancer cells, which are typically associated with aggressive phenotypes. Although acid-base disturbances in tumours often occur alongside hypoxia and lactate accumulation, there is now ample evidence for a distinct role of H-operated responses in key events underpinning cancer. The breadth of these actions presents therapeutic opportunities to change the trajectory of disease.
Topics: Humans; Protons; Neoplasms; Hydrogen-Ion Concentration; Lactic Acid; Tumor Microenvironment
PubMed: 37884609
DOI: 10.1038/s41568-023-00628-9 -
Clinical Oncology (Royal College of... Apr 2022
Topics: Humans; Protons; Radiation, Ionizing
PubMed: 35123851
DOI: 10.1016/j.clon.2022.01.038 -
Blood Jan 2022
Topics: Bacterial Proteins; Cell Proliferation; Protein Transport; Protons
PubMed: 35084476
DOI: 10.1182/blood.2021014237 -
Physiological Reviews Jan 2023The protonation state of soluble and membrane-associated macromolecules dictates their charge, conformation, and functional activity. In addition, protons (H or their... (Review)
Review
The protonation state of soluble and membrane-associated macromolecules dictates their charge, conformation, and functional activity. In addition, protons (H or their equivalents) partake in numerous metabolic reactions and serve as a source of electrochemical energy to drive the transmembrane transport of both organic and inorganic substrates. Stringent regulation of the intracellular pH is therefore paramount to homeostasis. Although the regulation of the cytosolic pH has been studied extensively, our understanding of the determinants of the H concentration ([H]) of intracellular organelles has developed more slowly, limited by their small size and inaccessibility. Recently, however, targeting of molecular probes to the organellar lumen together with advances in genomic, proteomic, and electrophysiological techniques have led to the identification and characterization of unique pumps, channels, and transporters responsible for the establishment and maintenance of intraorganellar pH. These developments and their implications for cellular function in health and disease are the subject of this review.
Topics: Humans; Hydrogen-Ion Concentration; Molecular Probes; Organelles; Proteomics; Protons; Vacuolar Proton-Translocating ATPases
PubMed: 35981302
DOI: 10.1152/physrev.00009.2022 -
The Journal of Physical Chemistry. B Nov 2021The pathway of activationless proton transfer induced by an electron-transfer reaction is studied theoretically. Long-range electron transfer produces highly...
The pathway of activationless proton transfer induced by an electron-transfer reaction is studied theoretically. Long-range electron transfer produces highly nonequilibrium medium polarization that can drive proton transfer through an activationless transition during the process of thermalization, dynamically altering the screening of the electron-proton Coulomb interaction by the medium. The cross electron-proton reorganization energy is the main energy parameter of the theory, which exceeds in magnitude the proton-transfer reorganization energy roughly by the ratio of the electron-transfer to proton-transfer distance. This parameter, which can be either positive or negative, is related to the difference in p values in two electron-transfer states. The relaxation time of the medium is on the (sub)picosecond time scale, which establishes the characteristic time for activationless proton transfer. Microscopic calculations predict substantial retardation of the collective relaxation dynamics compared to the continuum estimates due to the phenomenology analogous to de Gennes narrowing. Nonequilibrium medium configuration promoting proton transfer can be induced by either thermal or photoinduced charge transfer.
Topics: Electron Transport; Electrons; Protons
PubMed: 34714656
DOI: 10.1021/acs.jpcb.1c06949 -
Journal of the American Chemical Society Sep 2022The odyssey of photochemistry is accompanied by the journey to manipulate "electrons" and "protons" in time, in space, and in energy. Over the past decades,... (Review)
Review
The odyssey of photochemistry is accompanied by the journey to manipulate "electrons" and "protons" in time, in space, and in energy. Over the past decades, single-electron (1e) photochemical transformations have brought marvelous achievements. However, as each photon absorption typically generates only one exciton pair, it is exponentially challenging to accomplish multielectron and proton photochemical transformations. The multistep differences in thermodynamics and kinetics urgently require us to optimize light harvesting, expedite consecutive electron transfer, manipulate the interaction of catalysts with substrates, and coordinate proton transfer kinetics to furnish selective bond formations. Tandem catalysis enables orchestrating different photochemical events and catalytic transformations from subpicoseconds to seconds, which facilitates multielectron redox chemistries and brings consecutive, value-added reactivities. Joint efforts in molecular and material design, mechanistic understanding, and theoretical modeling will bring multielectron and proton synthetic opportunities for fuels, fertilizers, and chemicals with enhanced versatility, efficiency, selectivity, and scalability, thus taking better advantage of photons (i.e., sunlight) for our sustainable society.
Topics: Electron Transport; Electrons; Oxidation-Reduction; Photochemistry; Protons
PubMed: 36054091
DOI: 10.1021/jacs.2c02341 -
Physics in Medicine and Biology Nov 2020Proton computed tomography (CT) is an imaging modality investigated mainly in the context of proton therapy as a complement to x-ray CT. It uses protons with high enough...
Proton computed tomography (CT) is an imaging modality investigated mainly in the context of proton therapy as a complement to x-ray CT. It uses protons with high enough energy to fully traverse the imaged object. Common prototype systems measure each proton's position and direction upstream and downstream of the object as well as the energy loss which can be converted into the water equivalent thickness. A reconstruction algorithm then produces a map of the relative stopping power in the object. As an alternative to energy-loss proton CT, it has been proposed to reconstruct a map of the object's scattering power based on the protons' angular dispersion which can be estimated from the measured directions. As in energy-loss proton CT, reconstruction should best be performed considering the non-linear shape of proton trajectories due to multiple Coulomb scattering (MCS), but no algorithm to achieve this is so far available in the literature. In this work, we propose a filtered backprojection algorithm with distance-driven binning to account for the protons' most likely path. Furthermore, we present a systematic study of scattering proton CT in terms of inherent noise and spatial resolution and study the artefacts which arise from the physics of MCS. Our analysis is partly based on analytical models and partly on Monte Carlo simulations. Our results show that the proposed algorithm performs well in reconstructing relative scattering power maps, i.e. scattering power relative to that of water. Spatial resolution is improved by almost a factor of three compared to straight line projection and is comparable to energy-loss proton CT. Image noise, on the other hand, is inherently much higher. For example, in a water cylinder of 20 cm diameter, representative of a human head, noise in the central image pixel is about 40 times higher in scattering proton CT than in energy-loss proton CT. Relative scattering power in dense regions such as bone inserts is systematically underestimated by a few percent, depending on beam energy and phantom geometry.
Topics: Algorithms; Artifacts; Humans; Image Processing, Computer-Assisted; Monte Carlo Method; Phantoms, Imaging; Protons; Scattering, Radiation; Tomography, X-Ray Computed; Water
PubMed: 32998114
DOI: 10.1088/1361-6560/abbd18