Kinetic Isotope Effect
Kinetic Isotope Effect - Related Videos
02:31
Measuring the Kinetic Isotope Effect on Microbial Electron Transport Using Deuterium Oxide
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2025
Source: Tokunou, Y., et al, Electrochemical Detection of Deuterium Kinetic Isotope Effect on Extracellular Electron Transport in Shewanella oneidensis MR-1. J. Vis. Exp. (2018)This video demonstrates a whole-cell electrochemical method to assess how proton transfer affects extracellular electron transport (EET) in electroactive bacteria. By replacing protons with deuterons using deuterium oxide, the method measures changes in current to reveal a kinetic isotope effect, highlighting the role of...
02:31
Elements: Chemical Symbols and Isotopes
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2020
A chemical symbol is an abbreviation used to indicate an element or an atom of an element. For example, the symbol for mercury is Hg. The same symbol is used to indicate one atom of mercury (microscopic domain) or to label a container of many atoms of the element mercury (macroscopic domain). Some symbols are derived from the common English name of the element; others are abbreviations of the name in another language — Latin, Greek or German. For example, the symbol for aluminum (common name)...
09:00
Electrochemical Detection of Deuterium Kinetic Isotope Effect on Extracellular Electron Transport in Shewanella oneidensis MR-1
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Cited by 8 •
2018
Here we present a protocol of whole-cell electrochemical experiments to study the contribution of proton transport to the rate of extracellular electron transport via the outer-membrane cytochromes complex in Shewanella oneidensis MR-1.
01:12
Isotopes
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2026
Elements have a set number of protons that determines their atomic number (Z). For example, all atoms with eight protons are oxygen; however, the number of neutrons can vary for atoms of the same element. The sum of the number of protons and the number of neutrons is the mass number (A). Atoms with the same atomic number but different mass numbers are called isotopes. Elements can have multiple isotopes, for example, carbon-12, carbon-13, and carbon-14.An element's atomic mass, or weight, is a...
03:07
Kinetic Molecular Theory: Molecular Velocities, Temperature, and Kinetic Energy
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2020
The kinetic molecular theory qualitatively explains the behaviors described by the various gas laws. The postulates of this theory may be applied in a more quantitative fashion to derive these individual laws. Collectively, the molecules in a sample of gas have average kinetic energy and average speed; but individually, they move at different speeds. Molecules frequently undergo elastic collisions in which the momentum is conserved. Since the colliding molecules are deflected off at different...
FAQs
A primary kinetic isotope effect provides evidence that the bond to the labeled atom is involved in bond breaking or formation during the reaction. A secondary effect arises when isotope substitution helps reveal mechanistic changes without directly involving that bond event. Comparing these two patterns helps chemists locate which structural changes accompany a proposed reaction pathway.
Hydrogen and deuterium have different masses, so bonds containing them have different vibrational energies. When a reaction breaks or forms such a bond, those energy differences can change the activation energy required to reach the reactive state. The resulting rate difference connects isotopic substitution with the energetic features of the reaction mechanism.
Different pathways may involve different bond-making or bond-breaking events, so they can respond differently to isotope substitution. Measuring the rate change after labeling helps distinguish which pathway is more consistent with the observed behavior. This comparison gives mechanistic evidence beyond the overall reaction rate and can indicate which steps control the competing processes.
Chemists compare the rates of reactions using reactants that differ only in the isotope placed at a selected atom. They then relate the observed rate change to the bonds and energetic changes implicated in the proposed mechanism. This approach supplies experimental evidence for identifying bond events and evaluating whether a suggested pathway includes the relevant rate-determining step.
A rate difference associated with a particular isotope label indicates that the labeled atom is connected to an energetically important bond event in the reacting system. Chemists use that evidence to assess which proposed step most strongly influences the reaction rate. The result can support or challenge a mechanistic assignment in organic, biochemical, or physical chemistry.
The method is useful wherever researchers need evidence about how a reaction proceeds, including organic, biochemical, and physical chemistry. In organic chemistry, labeling can clarify bond changes; in biochemical chemistry, it can help examine reaction steps involving labeled atoms; and in physical chemistry, it can connect rate behavior with activation-energy changes.