Planar bond The peptide bond, the fundamental linkage connecting amino acids to form proteins, possesses a critical planar structure. This geometric arrangement is not an arbitrary feature; it arises directly from the electronic distribution within the amide group, specifically the partial double bond character between the nitrogen and carbonyl carbon atoms.作者：R Improta·2011·被引用次数：58—These indications are fully corroborated by a statistical survey of accurate protein/peptide structures. Orbital analysis shows that orbital interactions ... This inherent planarity is crucial for the stability and precise structure formation of proteins, dictating how polypeptide chains fold and interact to create functional biological molecules. Understanding this planar nature is key to appreciating the intricacies of protein architecture and function.
The planar geometry of the peptide bond is a direct consequence of resonance. In an amino acid, the nitrogen atom of the amino group has a lone pair of electronsRevisiting the concept of peptide bond planarity in an iron .... When this nitrogen forms a peptide bond with the carbonyl carbon of a carboxyl group, these electrons become delocalized. This delocalization results in a partial double bond character between the nitrogen and the carbonyl carbon, and a partial single bond character between the carbonyl carbon and the carbonyl oxygen. This phenomenon, often described as approximately 40% double bond character, means that the electron cloud is spread across the N-C(=O)-C system.The alpha carbons from each amino acid alternate with thepeptide bondsto form the “backbone” of the peptide. A similar linkage between a large number of amino ...
To accommodate this delocalization and maintain orbital overlap, the atoms involved in the peptide bond—the carbonyl carbon, the carbonyl oxygen, the nitrogen atom, and the alpha-carbon atoms attached to the nitrogen and carbonyl carbon—must lie in the same plane. This rigid, planar arrangement significantly restricts rotation around the N-C bond, unlike a typical single bond. This limitation on rotational freedom is a defining characteristic of the peptide bond and has profound implications for protein folding.2023年12月14日—Planar Structure. Theplanar structureof a protein chain refers to the geometric arrangement of atoms around thepeptide bond, which restricts ...
#### Key Aspects of Peptide Bond Planarity:
* Partial Double Bond Character: The sharing of electrons through resonance creates a partial double bond between the nitrogen and the carbonyl carbon.Peptide bond
* Resonance Structures: Two dominant resonance structures contribute to the overall electronic distribution, favoring the planar arrangement.
* Restricted Rotation: The partial double bond character prevents free rotation around the N-C bond, contributing to the rigidity of the peptide backbone.
The planarity of the peptide bond has far-reaching consequences for the overall structure of proteins. Because rotation is significantly restricted around the peptide bond itself, the flexibility of the polypeptide chain is primarily determined by rotation around the bonds connecting the alpha-carbons to the peptide backbone (the N-Cα and Cα-C bonds)Peptide Bonds. This selective freedom of rotation allows polypeptide chains to adopt specific, ordered conformations.
The planar nature of the peptide bond, along with the limited rotation, is fundamental to the formation of secondary structures like alpha-helices and beta-sheets. In an alpha-helix, the planar peptide units are arranged in a specific helical pattern, stabilized by hydrogen bonds.Theplanar peptidegroup showing dihedral angles andbondlength. The rotation angle clockwise around the C α −Cbondis known as ψ (psi) whereas angle of ... Similarly, in beta-sheets, multiple polypeptide strands align with their planar peptide bonds oriented in a way that allows for extensive hydrogen bonding between strands. This ordered arrangement of planar units creates a robust and predictable framework for protein folding.
Furthermore, the planarity of the peptide bond influences the orientation of the side chains of amino acids作者：AS Edison·2001·被引用次数：89—Planarity, the result of ∼40% N–C′ dou- blebondcharacter arising from two dominant reso- nancestructures, allows for a great simplification in the .... Since the peptide unit is planar, the alpha-carbons, which are attached to the side chains, are positioned in a way that projects the side chains outward from the helical or sheet structure. This outward projection is essential for the side chains to interact with each other and with the surrounding environment, ultimately determining the protein's three-dimensional shape and its biological function.
#### How Planarity Shapes Protein Architecture:
* Backbone Rigidity: Restricts rotation, making the peptide backbone relatively rigid.
* Secondary Structure Formation: Facilitates the formation of alpha-helices and beta-sheets through predictable arrangements and hydrogen bonding.
* Side Chain Orientation: Determines the outward projection of amino acid side chains, influencing inter- and intramolecular interactions.Why is peptide bond planar?
* Protein Stability: Contributes to the overall stability of folded protein structuresBSCI 1510L Literature and Stats Guide: Peptide bond.
While the peptide bond itself is planar, there are two possible spatial arrangements for the atoms around this bond: cis and trans isomers.PPS 97' - THE PEPTIDE BOND These isomers arise from the restricted rotation and refer to the relative positions of the two alpha-carbon atoms connected by the peptide bondCis-trans isomerism. Having partial doublebondcharacter, thepeptide bondisplanar. For steric reasons, the trans configuration is normally favored in .... In the trans configuration, the two alpha-carbon atoms are on opposite sides of the peptide bond. In the cis configuration, they are on the same side.
For steric reasons, the trans isomer is overwhelmingly favored in proteins, occurring in over 99% of peptide bonds.Peptide bondshave a planar, trans, configurationand undergo very little rotation or twisting around the amide bond that links the α-amino nitrogen of one ... The cis isomer would involve greater spatial repulsion between the side chains or other atoms, making it less energetically favorable9.2 Peptide bond formation - Organic Chemistry II. However, the cis isomer can occur, particularly when the amino acid proline is involved in the peptide bond, due to the cyclic nature of proline's side chain, which reduces the steric hindrance. The presence of cis peptide bonds, though rare, can significantly impact local protein structure and dynamics.
#### Understanding Isomerism:
* Trans Isomer: Alpha-carbons are on opposite sides of the peptide bond; energetically favored and most common作者：KP Tan·2021·被引用次数：78—Theplanar peptide bondhence influences the nature and types of secondarystructuresin proteins. In addition to the Ĥ angles, we also studied the ....
* Cis Isomer: Alpha-carbons are on the same side of the peptide bond; less common, can occur with proline.
* Impact on Structure: Isomerism can affect local conformation and protein folding pathways.
While the peptide bond is generally considered planar, research has shown that in some protein structures, there can be small deviations from perfect planarityResonance in the Peptide Bond. These "distortions from peptide planarity" are typically modest and can arise from various forces within the folded protein, such as strain or specific interactions between amino acid residues. Despite these minor departures, the fundamental concept of planarity remains a cornerstone for understanding peptide bond behavior and its role in protein structure. These deviations, while subtle, can sometimes play a role in protein function or dynamics, highlighting the complex interplay of forces that govern protein architecture.
In conclusion, the planar structure of the peptide bond, driven by resonance and partial double bond character, is a fundamental principle in biochemistry. This geometric constraint is not merely an academic detail but a critical factor that dictates the rigidity of the polypeptide backbone, enables the formation of ordered secondary structures, and ultimately underpins the diverse and complex three-dimensional architectures of proteins, essential for all life processes作者：R Improta·2011·被引用次数：58—These indications are fully corroborated by a statistical survey of accurate protein/peptide structures. Orbital analysis shows that orbital interactions ....
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