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Related Concept Videos

Acid Halides to Esters: Alcoholysis01:12

Acid Halides to Esters: Alcoholysis

Alcoholysis is a nucleophilic acyl substitution reaction in which an alcohol functions as a nucleophile. Acid halides react with alcohol to produce esters. The mechanism proceeds in three steps:
Esters to Carboxylic Acids: Acid-Catalyzed Hydrolysis01:13

Esters to Carboxylic Acids: Acid-Catalyzed Hydrolysis

Hydrolysis of esters under acidic conditions proceeds through a nucleophilic acyl substitution. In the presence of excess water, the reaction proceeds in a reversible manner, forming carboxylic acids and alcohols.
During hydrolysis, the ester is first activated towards nucleophilic attack through the protonation of the carboxyl oxygen atom by the acid catalyst. The protonation makes the ester carbonyl carbon more electrophilic. In the next step, water acts as a nucleophile and adds to the...
Esters to β-Ketoesters: Claisen Condensation Mechanism01:08

Esters to β-Ketoesters: Claisen Condensation Mechanism

Regular Claisen condensation involves the synthesis of β-ketoesters by combining identical ester molecules bearing two α hydrogens in the presence of an alkoxide base. The reaction commences with the deprotonation of the acidic α hydrogen by the base to form a resonance stabilized ester enolate. This nucleophilic ion then attacks the carbonyl center of another ester molecule to generate a tetrahedral alkoxide intermediate. Next, the expulsion of the alkoxide group from the intermediate restores...
E2 Reaction: Kinetics and Mechanism02:45

E2 Reaction: Kinetics and Mechanism

SN2 substitutions and E2 eliminations of alkyl halides proceed via a concerted pathway. While the nucleophile attacks the alpha carbon in SN2 reactions, it functions as a strong base and abstracts a beta hydrogen in the E2 mechanism. The rate-limiting transition state in E2 elimination reactions is characterized by partially broken carbon–hydrogen and carbon–halogen bonds and a partially formed pi bond between the alpha and beta carbons. The beta hydrogen and halide are eliminated...
Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration02:34

Regioselectivity and Stereochemistry of Acid-Catalyzed Hydration

The rate of acid-catalyzed hydration of alkenes depends on the alkene's structure, as the presence of alkyl substituents at the double bond can significantly influence the rate.
Alkylation of β-Diester Enolates: Malonic Ester Synthesis01:14

Alkylation of β-Diester Enolates: Malonic Ester Synthesis

Malonic ester synthesis is a method to obtain α substituted carboxylic acids from ꞵ-diesters such as diethyl malonate and alkyl halides.

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Defining Substrate Specificities for Lipase and Phospholipase Candidates
08:59

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Published on: November 23, 2016

Trimethyl lock: a stable chromogenic substrate for esterases.

Michael N Levine1, Luke D Lavis, Ronald T Raines

  • 1Department of Biochemistry, University of Wisconsin-Madison, 433 Babcock Drive, Madison, WI 53706-1544, USA.

Molecules (Basel, Switzerland)
|February 29, 2008
PubMed
Summary
This summary is machine-generated.

Researchers developed a stable chromogenic substrate for detecting esterase activity. This new substrate overcomes the instability of p-nitrophenyl acetate in water, improving esterase assays and prodrug activation studies.

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Area of Science:

  • Biochemistry
  • Organic Chemistry
  • Enzyme Assays

Background:

  • p-Nitrophenyl acetate is a common esterase substrate but is unstable in aqueous solutions.
  • This instability limits its use in various biochemical and cellular assays.
  • Esterases play crucial roles in human cells, including the activation of prodrugs.

Purpose of the Study:

  • To develop a stable chromogenic substrate for esterase detection.
  • To overcome the limitations of existing unstable substrates like p-nitrophenyl acetate.
  • To create a versatile tool for various esterase-related assays.

Main Methods:

  • A novel substrate was synthesized by incorporating a trimethyl lock moiety to stabilize the acetyl ester and p-nitroaniline groups.
  • The substrate's stability in aqueous solution was evaluated.
  • The release of p-nitroaniline upon ester hydrolysis and subsequent lactonization was characterized.

Main Results:

  • The newly designed substrate demonstrated enhanced stability in aqueous environments compared to p-nitrophenyl acetate.
  • Esterase-catalyzed hydrolysis of the substrate led to rapid lactonization, forming a hydrocoumarin and releasing p-nitroaniline.
  • The released p-nitroaniline serves as a chromogenic indicator of esterase activity.

Conclusions:

  • A stable and effective chromogenic substrate for esterase activity has been developed.
  • This 'prochromophore' offers a significant improvement over unstable substrates, expanding the utility of esterase assays.
  • The substrate has potential applications in diverse research areas, including prodrug activation and enzyme kinetics.