The enhancement mechanism of Fmoc-Arg(Pbf)-OH on the antibacterial activity of peptide chains mainly includes the following aspects:
·Increasing positive charges: Antibacterial peptides usually carry positive charges, while the surface of bacterial cell membranes is generally negatively charged. The arginine residue in Fmoc-Arg(Pbf)-OH carries a positive charge. Its introduction can increase the positive charge density of the peptide chain and strengthen the electrostatic attraction between the antibacterial peptide and the bacterial cell membrane, making it easier for the antibacterial peptide to bind to the bacterial cell membrane, thereby improving the antibacterial activity. For example, some studies have shown that antibacterial peptides rich in arginine can more effectively adsorb onto the surface of bacteria and thus exert their antibacterial effects.
·Changing the structure of the peptide chain: The side chain of arginine is relatively long and has a certain degree of rigidity. After Fmoc-Arg(Pbf)-OH participates in the synthesis of the peptide chain, the steric hindrance and chemical properties of its side chain will affect the folding and conformation of the peptide chain. An appropriate conformation is crucial for the interaction between the antibacterial peptide and the bacterial cell membrane. It can enable the antibacterial peptide to better insert into the bacterial cell membrane, form transmembrane channels or disrupt the integrity of the cell membrane, leading to the leakage of bacterial contents and achieving the goal of killing bacteria.
·Improving stability: In antibacterial peptides, the Pbf group in Fmoc-Arg(Pbf)-OH can protect the guanidino group of the arginine side chain, preventing it from being enzymatically hydrolyzed or undergoing other chemical reactions in the organism. This increases the stability of the peptide chain, allowing the antibacterial peptide to maintain its activity for a longer time in the body and indirectly enhancing its antibacterial effect. Moreover, this protective effect can prevent the antibacterial peptide from being degraded and inactivated before reaching the target site, so that it can better exert its antibacterial activity.
·Participating in the formation of special structures: Arginine residues can form specific secondary or tertiary structures, such as α-helices and β-sheets, through hydrogen bonds, electrostatic interactions, etc. with other amino acid residues. These special structures are crucial for the antibacterial activity of antibacterial peptides. They can enhance the binding ability of antibacterial peptides to the bacterial cell membrane or intracellular targets, or help the antibacterial peptides form stable pore structures on the bacterial cell membrane, enabling the antibacterial peptides to more effectively exert their antibacterial effects.
