Deviations in Bond Lengths and Bond Angles in Peptides

Allowed Deviations in fixed bond length and bond angles in peptides from the typical values

In peptides, the bond lengths and bond angles are generally determined by the underlying chemical structure and atomic interactions. However, there can be some deviations or variations in these values from the typical or average measurements. These discrepancies can be influenced by several factors, including steric hindrance, resonance effects, and hydrogen bonding.

1. Steric hindrance: Steric hindrance occurs when bulky groups or atoms are in close proximity, leading to repulsion and a deviation in bond angles and bond lengths. For example, if a side chain of an amino acid is large or contains multiple substituents, it can affect the bond angles and bond lengths in the peptide backbone

2. Resonance effects: Resonance occurs when electrons are delocalized within a molecule. In peptides, resonance can affect the bond lengths and bond angles between the atoms involved in the resonance system. This leads to a redistribution of electron density and can result in changes in the typical values of bond lengths and bond angles

3. Hydrogen bonding: Hydrogen bonding is a strong intermolecular force that can influence the geometry of the peptide backbone. When hydrogen bonds are formed between the peptide backbone and other molecules, it can cause changes in the bond angles and bond lengths. For example, hydrogen bonding can result in elongation or compression of the peptide bonds, affecting the bond lengths

It is important to note that the deviations in bond lengths and bond angles in peptides are usually within a narrow range and tend to follow certain trends. Researchers have conducted extensive studies on peptide structures and have established typical values for most amino acids. These values serve as references or averages to compare against experimental or theoretical measurements

However, it is also crucial to acknowledge that variations can exist among different peptide conformations and in different environments. Flexibility and conformational changes in the peptide structure can result in deviations from typical values. Additionally, factors such as temperature, pH, solvent composition, and crystal packing can influence the observed bond lengths and bond angles

In summary, while peptides generally exhibit well-defined bond lengths and bond angles, certain factors like steric hindrance, resonance effects, hydrogen bonding, and environmental conditions can lead to deviations from the typical or average values. Understanding these variations is important in studying peptide structures and their functional properties

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