Antimicrobial peptides (AMP) can be found in all living organisms. The peptides are always at low molecular mass (2-5 kDa). They are between 12 and 50 amino acids in size. The peptides are categorized into four classes: helical peptides, cyclic peptides, peptides with disulfide bonds, and peptides rich in certain amino acids such as prolin and cysteine.
The peptides containing aspartate, asparagine, serine, glutamate, glutamine, or alanine residues are much easier to form alpha-helix structure. The peptides with Ala and Leu do not have stabilizing side-chain reactions and can be found in many helix structures. The highly helical peptides can be used for drug design because these peptides retain the ligand-binding properties. Understanding the mechanism of alpha-helix formation by peptide will be beneficial for studying protein folding. The peptide sequences can be engineered to form helical structure by self-assembling hydrogelation. One example of such structure is through hydrogen-bonded networks by hydrophobic fibril-fibril interactions. The peptides containing Ala and Gln are important to form such hydrogels: IAALKAK or IQQLEQE.
Synthesis of cyclic peptides is developed to circumvent degradation of peptides. The cyclic peptide synthesis service can be performed via ligation of petpide hydrazides. The linear peptide is usually cleaved from the resin and cyclized in solution. The head-to-tail cyclic peptide can be synthesized after selective deprotection of certain amino acids. Some famous examples of cyclic peptides are bacitracin, cyclotide, and polymyxin.
Peptides containing disulfide bonds enhance their stability and activity. Many peptides with disulfide bonds are used to enhance stability against proteases. Peptides with disulfide bonds are used as cleavable covalent linkages for enhancing the cell penetration. Defensin is a cysteine-rich cationic protein. The 18-45 amino acid protein contains six to eight conserved cysteine residues.
Peptides rich in certain amino acids such as proline and cysteines. Defensin is the cysteine-rich antimicrobial peptide.
Antimicrobial peptides are promising candidates for novel therapeutic agents. Many peptides are used as antibiotics, anti-virus agents, insecticides, or anti-tumor agents to combat pathogenic microorganisms.
LifeTein utilizes proprietary peptide synthesis techniques to synthesize specific antimicrobial peptides. The physicochemical parameters such as net charge, amino acid structure and side chains, and hydrophobicity are considered and modified during the peptide synthesis process. Using D-amino acids, or Pro to Lys substitution are useful in breaking the secondary structure of peptide in order to reduce the hydrophobic interactions. Many mass spectrometry strategies such as MALDI-TOF, LC-electrospray ionization (ESI), and ion trap MS are used to identify products of solid-phase synthesis and thereby optimize synthetic conditions.