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Related Concept Videos

Chemiosmosis01:32

Chemiosmosis

Oxidative phosphorylation is a highly efficient process that generates large amounts of adenosine triphosphate (ATP), the basic unit of energy that drives many cellular processes. Oxidative phosphorylation involves two processes— the electron transport chain and chemiosmosis.
Electron Transport Chain
The electron transport chain involves a series of protein complexes on the inner mitochondrial membrane that undergo a series of redox reactions. At the end of this chain, the electrons reduce...
Electron Transport Chain Components01:29

Electron Transport Chain Components

The electron transport chain (ETC) is a crucial metabolic pathway that facilitates energy conversion in prokaryotic and eukaryotic cells. In eukaryotes, the ETC comprises four membrane-associated protein complexes in the inner mitochondrial membrane. In prokaryotes, the ETC in the plasma membrane can vary in composition, with fewer or different complexes depending on the organism and environmental conditions. These complexes transfer electrons from electron donors, such as NADH and FADH2, to...
Energy to Drive Translocation01:37

Energy to Drive Translocation

Mitochondrial protein import is powered by two distinct energy sources: ATP hydrolysis and electrochemical potential across the inner membrane. Newly synthesized precursors are bound by cytosolic chaperones of the Hsp70 family, which guide them to the import receptors on the mitochondrial surface. Utilizing the energy of ATP hydrolysis, Hsp70 chaperones transfer these precursors to the TOM receptors on the mitochondrial outer membrane.
Generally, polypeptides are unfolded by two distinct...
Chemiosmosis and ATP Synthesis01:22

Chemiosmosis and ATP Synthesis

The electron transport chain is a critical component of cellular respiration, occurring in the inner mitochondrial membrane. It facilitates the transfer of high-energy electrons from reduced cofactors NADH and FADHâ‚‚ to molecular oxygen, the final electron acceptor. This transfer of electrons through a series of protein complexes is tightly coupled to the translocation of protons across the membrane, generating a proton gradient essential for ATP synthesis.Electron Flow and Proton...
Translocation of Proteins into the Mitochondria01:19

Translocation of Proteins into the Mitochondria

Mitochondrial precursors are translocated to the internal subcompartments via independent mechanisms involving distinct protein machineries called translocases.
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
Protein Transport into the Inner Mitochondrial Membrane01:34

Protein Transport into the Inner Mitochondrial Membrane

Nuclear encoded mitochondrial precursors are imported to the inner membrane in a multistep process involving two separate translocons, TIM22 and TIM23. TIM23 is a cation-selective pore that remains closed by the N terminal segment of the protein. Negative charges on the TIM23 act as a receptor for the incoming precursor, pulling the positively charged matrix-targeting sequence for peptide insertion and translocation.
Transport of mitochondrial precursors across the TIM23 channel is driven by...

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Related Experiment Video

Updated: May 20, 2026

Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method
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Published on: July 19, 2019

Parallel proton transfer pathways in a metallopeptide artificial hydrogenase.

Ji Won Han1, Jose L Alvarez-Hernandez1, Afsar Ali1

  • 1Department of Chemistry, University of Rochester, Rochester, NY 14627-0216, USA.

Journal of Inorganic Biochemistry
|May 18, 2026
PubMed
Summary

Cobalt-peptide catalysts show enhanced hydrogen evolution activity. Lysine side chains and buffer species facilitate distinct proton transfer pathways, crucial for efficient catalysis in proton-requiring reactions.

Keywords:
Hydrogen evolution catalysisProton inventoryProton shuttlesProton transfer

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Related Experiment Videos

Last Updated: May 20, 2026

Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method
05:51

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Published on: July 19, 2019

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Analyzing Protein Dynamics Using Hydrogen Exchange Mass Spectrometry
11:37

Analyzing Protein Dynamics Using Hydrogen Exchange Mass Spectrometry

Published on: November 29, 2013

Area of Science:

  • Catalysis research
  • Coordination chemistry
  • Electrochemistry

Background:

  • Proton transfer is vital for many catalytic reactions.
  • Developing efficient catalysts for proton-requiring reactions requires a deeper understanding of proton transfer mechanisms.
  • Cobalt-peptide complexes offer a promising platform for studying these processes.

Purpose of the Study:

  • To investigate the impact of outer coordination sphere modifications and exogenous acid/base species on the hydrogen evolution activity of cobalt-peptide catalysts.
  • To elucidate the role of lysine side chains in proton transfer and catalytic activity.
  • To differentiate proton transfer pathways in the presence and absence of buffering agents.

Main Methods:

  • Synthesis and characterization of cobalt complexes with tripeptides: glycyl-glycyl-histidine (CoGGH), lysyl-lysyl-histidine (CoKKH), and trimethyllysyl-trimethyllysyl-histidine (CoTmlTmlH).
  • Electrochemical studies including cyclic voltammetry (CV) to assess hydrogen evolution activity.
  • pH dependence studies and proton inventory experiments to analyze proton transfer mechanisms.

Main Results:

  • CoKKH exhibited superior catalytic current and rate compared to CoGGH and CoTmlTmlH in water, attributed to lysine side chain facilitation of proton transfer.
  • CoKKH's cyclic voltammogram showed pH independence up to pH 11 without buffers, highlighting the role of lysine side chains in proton availability.
  • Addition of buffering agents enhanced catalytic current for all derivatives, indicating proton delivery by these species, while CoKKH maintained a buffer-independent pathway.
  • Proton inventory studies confirmed distinct proton transfer pathways with and without buffers, revealing multiple protonatable sites in the presence of buffers.

Conclusions:

  • Lysine side chains in cobalt-peptide catalysts play a significant role in facilitating proton transfer and enhancing hydrogen evolution activity.
  • Exogenous buffering agents provide alternative proton delivery pathways, leading to improved catalytic performance.
  • The CoKKH catalyst demonstrates the existence of multiple, parallel proton transfer pathways, underscoring the complexity and tunability of catalytic mechanisms.