Peptide Chemistry & Structure
Definitions related to peptide composition, bonding, folding, chemical modification, and structure–function concepts commonly referenced in peptide research.
- Amino Acid Residue
- An amino acid unit within a peptide chain after it has formed peptide bonds with neighboring amino acids.
- Primary Structure
- The linear amino acid sequence of a peptide, which strongly influences stability and biological behavior.
- Secondary Structure
- Local folding patterns (such as alpha-helices and beta-sheets) formed by hydrogen bonding within a peptide backbone.
- Tertiary Structure
- The overall 3D shape of a peptide or protein created by folding interactions between side chains and backbone elements.
- Conformation
- The specific 3D arrangement of atoms in a peptide; conformational changes can alter receptor binding or stability.
- Alpha-Helix
- A common secondary structure where the peptide backbone coils into a helix stabilized by hydrogen bonds.
- Beta-Sheet
- A secondary structure made of extended peptide strands aligned side-by-side and stabilized by hydrogen bonds.
- Side Chain (R-Group)
- The variable chemical group attached to an amino acid that determines many of its properties and interactions.
- Net Charge
- The overall electrical charge of a peptide at a given pH, influenced by the composition of ionizable residues.
- Hydrophobicity
- The tendency of residues or peptides to repel water; often influences folding, aggregation, and solubility.
- Solubility
- The ability of a peptide to dissolve in a given solvent, impacted by sequence, charge, and hydrophobic regions.
- Aggregation
- Clumping of peptide molecules into larger complexes, which can reduce activity and complicate handling or testing.
- Disulfide Bond
- A covalent bond between two cysteine residues that can stabilize peptide structure and influence folding.
- Cyclization
- Chemically linking peptide ends (or internal residues) to form a cyclic structure that may improve stability.
- Acetylation
- A chemical modification that adds an acetyl group (often at the N-terminus), potentially altering stability or activity.
- Amidation
- A modification often applied at the C-terminus that can improve stability and reduce enzymatic degradation.
- PEGylation
- Attachment of polyethylene glycol (PEG) to a peptide to alter solubility and improve stability in research contexts.
- Stapled Peptide
- A peptide engineered with a chemical “staple” to stabilize an alpha-helical structure and improve resistance to degradation.
- D-Amino Acids
- Amino acids in the D-configuration (mirror image of natural L-amino acids) sometimes used to improve peptide stability.
- Sequence Homology
- Similarity in amino acid sequence between peptides, often used to infer related structure or potential function.
- Structure–Function Relationship
- The concept that a peptide’s structure strongly influences its binding behavior, stability, and biological activity.