Periodic table
The concept of peptide resonance is fundamental to understanding the structure and behavior of peptides and proteins. This phenomenon, arising from the delocalization of electrons within the peptide bond, significantly influences its properties, including its planarity and restricted rotation2022年8月16日—Allpeptideshaveresonancecontributors where the lone pair on the nitrogen isresonancedelocalized into the carbonyl group, leaving negative .... By examining the resonance structures of the peptide bond, we can gain insight into why this crucial linkage is rigid and planar, a characteristic that dictates the overall three-dimensional folding of polypeptide chains.
A peptide bond is formed through a dehydration reaction between the carboxyl group of one amino acid and the amino group of another. Chemically, it's an amide bond, characterized by a carbon-nitrogen linkage. However, the presence of the adjacent carbonyl group (C=O) leads to a unique electronic arrangement.Resonance in the Peptide Bond The lone pair of electrons on the nitrogen atom can delocalize into the pi system of the carbonyl group.Resonance in the Peptide Bond This electron delocalization is the essence of peptide resonance.
This resonance effect results in a partial double-bond character for the carbon-nitrogen bond within the peptide linkage. Consequently, the bond is shorter and stronger than a typical single bond, and rotation around it is significantly hindered. This restricted rotation is a critical factor in determining the conformational possibilities of a peptide chain.
The resonance stabilization of the peptide bond has several crucial implications for peptide and protein structure:
* Planarity: The partial double-bond character forces the atoms involved in the peptide bond—the carbonyl carbon, carbonyl oxygen, alpha-carbon, and the amide nitrogen—to lie in the same plane. This planarity is a defining feature of the peptide backbone.
* Rigidity: The restricted rotation around the C-N bond due to resonance contributes to the overall rigidity of the peptide backbone. While rotation is still possible around the bonds connecting the alpha-carbon to the carbonyl carbon and the alpha-carbon to the nitrogen, the peptide bond itself remains relatively fixed.
* Bond Order: Resonance increases the bond order of the C-N bond from approximately 1 (for a single bond) to about 1.Thepeptidebond is the amide bond formed between the carbonyl group (C=O) of one amino acid and the amine group (NH) of another amino acid.2-1.Interestingly, peptide bonds have a second resonance form, as demonstrated below. This means that the peptide bond (the C=O. and N-H) all reside in a single ...3. This enhanced bond order explains its increased strength and reduced bond length compared to a typical C-N single bondResonance contributors for the peptide bonds.
* Polarity: The delocalization of electrons also results in a partial positive charge on the carbonyl carbon and a partial negative charge on the nitrogen atom, contributing to the polar nature of the peptide bond. This polarity plays a role in intermolecular interactions, such as hydrogen bonding, which are vital for protein folding.
To visualize peptide resonance, chemists draw resonance contributors2022年8月16日—Allpeptideshaveresonancecontributors where the lone pair on the nitrogen isresonancedelocalized into the carbonyl group, leaving negative .... The primary resonance structure depicts a single bond between the carbon and nitrogen, with a double bond between the carbon and oxygen. However, a significant contributing resonance structure shows a double bond between the carbon and nitrogen and a single bond between the carbon and oxygen, with the nitrogen carrying a formal positive charge and the oxygen carrying a formal negative charge.作者：DG Fedorov·2024·被引用次数：5—Thepeptidebond order (1.2) for the σ(C−N) bond is enhanced by aresonancecoupling of the π(C−O) bond and the lone pair of N. To usepeptide... The actual peptide bond is a hybrid of these structures, with delocalized electrons shared across these atoms.
The properties conferred by peptide resonance have been investigated using various spectroscopic techniques. For instance, UV Resonance Raman spectroscopy has been employed to study the vibrational modes of peptide bonds in proteins, providing insights into their electronic structure and conformational states. Nuclear Magnetic Resonance (NMR) spectroscopy, particularly techniques like rotational resonance NMR, has also been instrumental in characterizing the structural dynamics and conformation of peptides and proteins, indirectly confirming the implications of resonance on bond characteristics and molecular motion.
In summary, peptide resonance is a critical electronic phenomenon that underpins the structural integrity and conformational behavior of peptides and proteins. The delocalization of electrons within the peptide bond leads to its partial double-bond character, resulting in planarity, rigidity, and increased bond strength. These characteristics are foundational to the formation of secondary structures like alpha-helices and beta-sheets, ultimately dictating the complex three-dimensional architecture and function of biological macromoleculesPeptide Conformations. I. Nuclear Magnetic Resonance .... Understanding peptide resonance is therefore essential for comprehending protein chemistry, molecular biology, and related fields.
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