Free Water Protons
Free Water Protons - Related Videos
09:40
Proton Exchange Membrane Fuel Cells
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2023
Source: Laboratories of Margaret Workman and Kimberly Frye - Depaul University The United States consumes a large amount of energy – the current rate is around 97.5 quadrillion BTUs annually. The vast majority (90%) of this energy comes from non-renewable fuel sources. This energy is used for electricity (39%), transportation (28%), industry (22%), and residential/commercial use (11%). As the world has a limited supply of these non-renewable sources, the United States (among others) is...
02:30
Water: A Bronsted-Lowry Acid and Base
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2020
The reaction between a Brønsted-Lowry acid and water is called acid ionization. For example, when hydrogen fluoride dissolves in water and ionizes, protons are transferred from hydrogen fluoride molecules to water molecules, yielding hydronium ions and fluoride ions: Base ionization of a species occurs when it accepts protons from water molecules. In the example below, pyridine molecules, C5NH5, undergo base ionization when dissolved in water, yielding hydroxide and pyridinium ions: The...
01:07
Proton (¹H) NMR: Chemical Shift
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2024
Organic molecules primarily contain carbon and hydrogen atoms. While all the hydrogen isotopes are NMR-active, protium or hydrogen-1 is the most abundant. It has a significant energy separation between its nuclear spin states due to its large gyromagnetic ratio. As per Boltzmann's distribution, an increase in the energy separation implies a greater excess population of nuclei available for excitation, resulting in a strong NMR absorption signal. Absorption signals of all the protium nuclei in a...
07:38
Functional Characterization of Na+/H+ Exchangers of Intracellular Compartments Using Proton-killing Selection to Express Them at the Plasma Membrane
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Cited by 4 •
2015
The first part of this article shows how to select mutant cell lines expressing vesicular Na+/H+ exchangers at their plasma membrane. The second part provides protocols based on intracellular pH measurements and fast ion uptake, which are used to determine the ion selectivity and the kinetic parameters of these exchangers.
01:23
States of Water
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2019
Water exists in any one of the three classical states: solid (ice), liquid (water), and gas (steam or water vapor). The state of water depends on i) the intermolecular forces that draw molecules together and ii) the kinetic energy that leads to movements that pull them apart. Water freezes when the intermolecular forces are greater than the kinetic energy. Unlike most other substances, water is less dense in its solid state than in its liquid state. This is because each water molecule can form...
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T1 and T2 relaxation describe different aspects of how perturbed proton magnetization returns toward equilibrium. Their measured behavior is influenced by the local water content and molecular environment, so the resulting MRI signal contains more information than proton abundance alone. Considering both relaxation processes helps researchers characterize tissue conditions associated with structural or physiological change.
Protons in mobile water respond differently from protons associated with tissue structures because their molecular environments constrain motion to different degrees. This distinction affects the measured MRI signal and helps separate relatively unrestricted extracellular water from tissue-bound water. The resulting contrast provides a window into changes in brain microstructure and local tissue organization.
Free-water measurements can separate relatively unrestricted extracellular water from water more closely associated with tissue, adding context to diffusion MRI findings. This distinction helps determine whether an apparent diffusion change may reflect altered tissue microstructure, increased extracellular water, or both. As a result, free-water analysis can improve interpretation of subtle brain abnormalities.
The signal depends on the alignment of protons in the applied magnetic field, the effect of the radiofrequency pulse, and the subsequent T1 and T2 relaxation behavior. Local water content and the surrounding molecular environment also shape the measured response. Together, these factors determine how sensitively MRI reflects regional tissue conditions.
MRI first places the hydrogen nuclei in an applied magnetic field, where their alignment establishes the starting magnetization. A radiofrequency pulse then perturbs that alignment, and the scanner measures the signal produced as the protons relax through T1 and T2 processes. Analysis of this response provides measurements related to water content and molecular surroundings.
These measurements are useful when researchers need to examine brain microstructure or detect tissue changes that may not be apparent from structure alone. Applications described for neuroscience include studying edema, inflammation, aging, and neurodegenerative disease. They can also provide biomarkers of subtle changes and strengthen the interpretation of diffusion MRI results.