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Related Concept Videos

Preparation and Reactions of Thiols02:33

Preparation and Reactions of Thiols

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.
Sulfur Assimilation01:20

Sulfur Assimilation

Sulfur is an essential element in biological systems, contributing to synthesizing key biomolecules, including amino acids such as cysteine and methionine, and cofactors such as coenzyme A and biotin. Microorganisms primarily assimilate sulfur as sulfate (SO₄²⁻) from the environment, which must undergo a series of biochemical transformations before it can be incorporated into cellular components. As sulfate is highly oxidized, it must undergo assimilatory sulfate reduction to become...
Structure and Nomenclature of Thiols and Sulfides02:17

Structure and Nomenclature of Thiols and Sulfides

Thiols and sulfides are sulfur analogs of alcohols and ethers, respectively, where the sulfur atom takes the place of the oxygen atom. Thus, thiols are generally represented as RSH, where R is an alkyl substituent and —SH is the functional group. On the other hand, in sulfides, the central sulfur atom is bonded to two hydrocarbon groups on either side. Depending upon the type of group, sulfides can be either symmetrical or asymmetrical. Both thiols and sulfides display a bent geometry, similar...
Redox Titration: Other Oxidizing and Reducing Agents01:26

Redox Titration: Other Oxidizing and Reducing Agents

Besides iodine, other oxidizing or reducing agents can serve as titrants in redox titrations. Common oxidizing titrants include KMnO4, cerium(IV), and K2Cr2O7. The choice of oxidizing titrants depends on factors like stability, cost, analyte strength, and reaction rate between the analyte and titrant. KMnO4 is a strong oxidizing titrant that reduces from Mn(VII) to Mn(II) in a highly acidic solution, simultaneously oxidizing the analyte to a higher oxidation state. In this case, KMnO4 acts as a...
Preparation and Reactions of Sulfides02:26

Preparation and Reactions of Sulfides

Sulfides are the sulfur analog of ethers, just as thiols are the sulfur analog of alcohol. Like ethers, sulfides also consist of two hydrocarbon groups bonded to the central sulfur atom. Depending upon the type of groups present, sulfides can be symmetrical or asymmetrical. Symmetrical sulfides can be prepared via an SN2 reaction between 2 equivalents of an alkyl halide and one equivalent of sodium sulfide.
Protein Modifications in the RER01:26

Protein Modifications in the RER

Modification of secretory and transmembrane proteins entering the rough ER begins in the ER lumen. These modifications aid in protein folding and stabilize the acquired tertiary structure. Protein modifications in the rough ER co-occur at different stages of protein folding.
Broadly, these modifications can be categorized into four main categories — glycosylation, formation of disulfide bonds, assembly of protein subunits, and specific proteolytic cleavages like removal of signal sequences.

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Related Experiment Video

Updated: Jul 3, 2026

A Rapid and Specific Microplate Assay for the Determination of Intra- and Extracellular Ascorbate in Cultured Cells
11:56

A Rapid and Specific Microplate Assay for the Determination of Intra- and Extracellular Ascorbate in Cultured Cells

Published on: April 11, 2014

Is ascorbate able to reduce disulfide bridges? A cautionary note.

Daniela Giustarini1, Isabella Dalle-Donne, Roberto Colombo

  • 1Department of Evolutionary Biology, Laboratory of Pharmacology and Toxicology, University of Siena, via A. Moro 4, I-53100 Siena, Italy.

Nitric Oxide : Biology and Chemistry
|August 5, 2008
PubMed
Summary
This summary is machine-generated.

The biotin switch assay identifies S-nitrosated proteins but requires validation. Ascorbate, used in the assay, can non-selectively cleave disulfide bonds, impacting protein analysis.

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Resin-Assisted Capture Coupled with Isobaric Tandem Mass Tag Labeling for Multiplexed Quantification of Protein Thiol Oxidation
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Combining Non-reducing SDS-PAGE Analysis and Chemical Crosslinking to Detect Multimeric Complexes Stabilized by Disulfide Linkages in Mammalian Cells in Culture
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Combining Non-reducing SDS-PAGE Analysis and Chemical Crosslinking to Detect Multimeric Complexes Stabilized by Disulfide Linkages in Mammalian Cells in Culture

Published on: May 2, 2019

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Last Updated: Jul 3, 2026

A Rapid and Specific Microplate Assay for the Determination of Intra- and Extracellular Ascorbate in Cultured Cells
11:56

A Rapid and Specific Microplate Assay for the Determination of Intra- and Extracellular Ascorbate in Cultured Cells

Published on: April 11, 2014

Resin-Assisted Capture Coupled with Isobaric Tandem Mass Tag Labeling for Multiplexed Quantification of Protein Thiol Oxidation
07:16

Resin-Assisted Capture Coupled with Isobaric Tandem Mass Tag Labeling for Multiplexed Quantification of Protein Thiol Oxidation

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Combining Non-reducing SDS-PAGE Analysis and Chemical Crosslinking to Detect Multimeric Complexes Stabilized by Disulfide Linkages in Mammalian Cells in Culture
09:37

Combining Non-reducing SDS-PAGE Analysis and Chemical Crosslinking to Detect Multimeric Complexes Stabilized by Disulfide Linkages in Mammalian Cells in Culture

Published on: May 2, 2019

Area of Science:

  • Biochemistry
  • Proteomics

Background:

  • The biotin switch assay is widely used for identifying S-nitrosated proteins.
  • Concerns exist regarding the thorough validation of this assay, particularly the role of ascorbate.
  • Ascorbate's selectivity in cleaving S-nitrosothiols at higher concentrations is not well-characterized.

Purpose of the Study:

  • To validate the biotin switch assay by characterizing ascorbate's cleavage activity.
  • To assess the selectivity of ascorbate as a cleaving agent for S-N bonds.
  • To investigate the influence of pH, concentration, and light on ascorbate's reactions.

Main Methods:

  • Investigated ascorbate's reaction with various disulfide bonds (DTNB, cystine, glutathione disulfide, etc.) and biotin-HPDP.
  • Determined the pH and concentration dependence of these reactions.
  • Assessed the effect of indirect sunlight on ascorbate-mediated cleavage.

Main Results:

  • Ascorbate non-selectively reduces disulfide bridges in a pH- and concentration-dependent manner.
  • Ascorbate also cleaves S-nitrosothiols.
  • Sunlight can influence these cleavage reactions.

Conclusions:

  • The biotin switch assay's reliance on ascorbate may lead to non-specific cleavage of disulfide bonds.
  • Further validation is needed to ensure the accuracy of S-nitrosated protein identification using this method.
  • Careful control of experimental conditions, including light exposure, is crucial.