What are the physical properties of peptides?

Physical properties of peptide bonds depend on the amino acids that they are composed of. For instance, some amino acids may increase the solubility of peptides in water, while others can make them less or more stable. Peptide bonds are physically resistant to both thermal and chemical degradation. For this reason, they are useful to produce long lasting drugs and molecules. Peptides also have high melting points, and their stability is key in producing therapeutic agents. Peptides have a low molecular weight and consist of fewer secondary structures. Additionally, they have a high amount of ionizable groups.

Peptides are rigid and planar, and therefore rotation is very limited to near none. This allows for the peptide bond to remain fixed in a cis or trans configuration. The trans configuration of peptide bonds creates less steric hindrances of amino acid molecules. Peptide bonds exhibit a partial double bond characteristic due to its bond resonance. Resonance structures form due to the interaction between the carbonyl groups’ double bond electrons and the electrons of the C-N bond. Since their double bonds are short and durable, more free energy is necessary to break them.