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Related Concept Videos

Electron Transport Chain: Complex III and IV01:43

Electron Transport Chain: Complex III and IV

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During the electron transport chain, electrons from NADH and FADH2 are first transferred to complexes I and II, respectively. These two complexes then transfer the electrons to ubiquinol, which carries them further to complex III. Complex III passes the electrons across the intermembrane space to Cyt c, which carries them further to complex IV. Complex IV donates electrons to oxygen and reduces it to water. As electrons pass through complexes I, III, and IV, the energy released aids the pumping...
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Oxidation of Phenols to Quinones01:17

Oxidation of Phenols to Quinones

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In the presence of oxidizing agents, phenols are oxidized to quinones. Quinones can be easily reduced back to phenols using mild reducing agents. The electron-donating hydroxyl group enhances the reactivity of the aromatic ring, enabling oxidation of the ring even in the absence of an α hydrogen.
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox...
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Photochemical Electrocyclic Reactions: Stereochemistry01:26

Photochemical Electrocyclic Reactions: Stereochemistry

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The absorption of UV–visible light by conjugated systems causes the promotion of an electron from the ground state to the excited state. Consequently, photochemical electrocyclic reactions proceed via the excited-state HOMO rather than the ground-state HOMO. Since the ground- and excited-state HOMOs have different symmetries, the stereochemical outcome of electrocyclic reactions depends on the mode of activation; i.e., thermal or photochemical.
Selection Rules: Photochemical Activation
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Oxidation of Alkenes: Syn Dihydroxylation with Osmium Tetraoxide02:44

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Alkenes are converted to 1,2-diols or glycols through a process called dihydroxylation. It involves the addition of two hydroxyl groups across the double bond with two different stereochemical approaches, namely anti and syn. Dihydroxylation using osmium tetroxide progresses with syn stereochemistry.
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Preparation and Reactions of Thiols02:33

Preparation and Reactions of Thiols

7.2K
Thiols are prepared using the hydrosulfide anion as a nucleophile in a nucleophilic substitution reaction with alkyl halides. For instance, bromobutane reacts with sodium hydrosulfide to give butanethiol.
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Drug Metabolism: Phase I Reactions01:17

Drug Metabolism: Phase I Reactions

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A phase I reaction is a biochemical process that introduces a functionally reactive polar group to a substance. This transformation predominantly occurs in the liver, facilitated by the cytochrome P450 system of hemoproteins situated in the lipophilic endoplasmic reticulum of cells. The metabolite generated through this process can have varying polarities. If it is sufficiently polar, it can be easily excreted in the urine due to its water compatibility. However, if the metabolite is nonpolar,...
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Benchtop Immobilized Metal Affinity Chromatography, Reconstitution and Assay of a Polyhistidine Tagged Metalloenzyme for the Undergraduate Laboratory
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Cytochrome P450. The Dioxygen-Activating Heme Thiolate.

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    Cytochromes P450 (CYPs) are versatile heme enzymes crucial for life, detoxifying harmful chemicals. Their catalytic cycle involves high-valent iron-oxo species essential for activating dioxygen and breaking chemical bonds.

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    Area of Science:

    • Biochemistry
    • Enzymology
    • Molecular Biology

    Background:

    • Cytochromes P450 (CYPs) are heme-binding enzymes found across all life domains.
    • They play vital roles in essential life processes and are key targets in pharmacology and toxicology.
    • CYPs detoxify xenobiotics, including drugs, plant toxins, and environmental pollutants, through dioxygen modification.

    Purpose of the Study:

    • To elucidate the fundamental catalytic mechanisms of Cytochromes P450.
    • To detail the structural and electronic properties of the active site in different redox states.
    • To understand the role of high-valent intermediates in dioxygen activation and substrate metabolism.

    Main Methods:

    • Spectroscopic analysis (UV/Vis, EPR) to characterize heme iron states (Fe(III), Fe(II)).
    • Investigation of enzyme flexibility and substrate-binding dynamics (open/closed conformations).
    • Characterization of catalytic intermediates (Compound I, Compound II) and their properties.

    Main Results:

    • The active form features a thiolate-coordinated heme iron, with characteristic spectral signatures.
    • The Fe(II) state forms a complex with carbon monoxide, leading to the P450 designation (λmax 450 nm).
    • CYPs exhibit conformational flexibility, transitioning between open and closed states.
    • The catalytic cycle involves high-valent iron-oxo species (Compound I and II) crucial for oxidation.

    Conclusions:

    • CYPs are essential, versatile catalysts with a complex catalytic cycle involving unique heme intermediates.
    • Their structural flexibility and sophisticated chemistry enable the metabolism of a wide range of substrates.
    • Understanding CYP mechanisms is critical for drug development, toxicology, and biotechnology.