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[56] Carbodiimide modification of proteins.
Methods in Enzymology
|September 28, 2012
Summary
This study introduces a carbodiimide-nucleophile method for protein carboxyl group modification under mild conditions. The versatile technique enables accurate carboxyl group quantification and targeted residue modification for activity studies.
Area of Science:
- Biochemistry
- Protein Chemistry
- Chemical Biology
Background:
- Carboxyl groups in proteins are crucial for structure and function.
- Modifying carboxyl groups is essential for understanding protein activity and for therapeutic applications.
- Existing methods for carboxyl group modification often require harsh conditions or lack specificity.
Purpose of the Study:
- To develop a mild and versatile method for modifying protein carboxyl groups.
- To enable quantitative determination of all carboxyl groups.
- To facilitate the modification of selected carboxyl residues for activity studies.
Main Methods:
- Utilizing a carbodiimide-nucleophile procedure.
- Employing mild reaction conditions.
- Allowing variations in carbodiimide activators and nucleophiles.
Main Results:
- The method allows for quantitative determination of all protein carboxyl groups.
- Selected carboxyl residues can be modified under mild conditions.
- The procedure offers flexibility through various carbodiimide and nucleophile choices.
- Side reactions were observed and methods for correction were identified.
Conclusions:
- The carbodiimide-nucleophile procedure is a valuable tool for protein carboxyl group modification.
- This method provides a mild, quantitative, and versatile approach for biochemical and biophysical studies.
- Further research can explore specific applications in protein engineering and drug development.
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01:29Preparation of Amides
Amides are synthesized by treating carboxylic acids with amines in the presence of dehydrating agents like dicyclohexylcarbodiimide (DCC).
The DCC-promoted synthesis of amides begins with the protonation of DCC by carboxylic acid. The protonation makes it a better acceptor. Next, the addition of carboxylate to the protonated carbodiimide gives a reactive acylating agent.
Subsequently, the amine acts as a nucleophile that attacks the acylating agent to form a tetrahedral intermediate. In the...
The DCC-promoted synthesis of amides begins with the protonation of DCC by carboxylic acid. The protonation makes it a better acceptor. Next, the addition of carboxylate to the protonated carbodiimide gives a reactive acylating agent.
Subsequently, the amine acts as a nucleophile that attacks the acylating agent to form a tetrahedral intermediate. In the...
02:10Carbocations
Carbocations are one of the reaction intermediates formed during several nucleophilic substitutions or elimination reactions. A carbocation is an electron-deficient species with the central carbon atom having six electrons and three bonded atoms. The central carbon in a carbocation is sp2 hybridized with trigonal planar geometry. It has an empty p orbital perpendicular to the plane of the structure that can accept electrons. Thus, carbocations act as strong electrophiles and may react with any...
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Primary amines react with carbonyl compounds—aldehydes and ketones—to generate imines. Imines consist of a C=N double bond and are named Schiff bases after its discoverer—the German chemist Hugo Schiff. On the other hand, secondary amines react with carbonyl compounds to give enamines. In enamines, the presence of a C=C double bond adjacent to the nitrogen atom leads to the delocalization of the lone pair.
01:28Amides to Carboxylic Acids: Hydrolysis
Amides can undergo either acid-catalyzed hydrolysis or base-promoted hydrolysis through a typical nucleophilic acyl substitution. Each hydrolysis requires severe conditions.
Acid-catalyzed hydrolysis:
Hydrolysis of amides under acidic conditions yields carboxylic acids. Since the reaction occurs slowly, hydrolysis requires the conditions of heat.
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Acid-catalyzed hydrolysis:
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