total synthesis of nisin by solid phase peptide synthesis nisin - toxic-peptides Solid-phase peptide synthesis of five A-ring analogues of the lantibiotic nisin The Total Synthesis of Nisin by Solid Phase Peptide Synthesis: A Deep Dive

where-are-peptide-bonds-found-in-a-protein The total synthesis of nisin has emerged as a significant area of research, particularly through the application of solid phase peptide synthesis (SPPS). Nisin, a potent lantibiotic peptide antibiotic, possesses a complex structure characterized by multiple thioether rings and unusual amino acids, making its de novo synthesis a formidable challenge. While traditional solution-phase methods have been explored, SPPS offers a more streamlined and efficient approach for constructing such intricate molecules and their analogues. This article delves into the intricacies of achieving the total synthesis of nisin using solid-phase techniques, exploring the methodologies, challenges, and advancements in the field.

Understanding Nisin and the Need for Synthesis

Nisin is a naturally occurring antimicrobial peptide produced by *Lactococcus lactis*. Its mechanism of action involves binding to the lipid II precursor of bacterial cell wall synthesis, leading to pore formation and cell death. This potent antibacterial activity has led to its widespread use as a food preservative. However, the growing concern over antibiotic resistance and the desire for novel therapeutic agents have spurred interest in synthesizing nisin and its derivatives chemically. The total synthesis of nisin not only provides access to the natural product itself but also allows for the creation of modified analogues with potentially enhanced or altered properties, such as improved stability, broader spectrum activity, or reduced toxicity.What is solid phase peptide synthesis?

The Power of Solid Phase Peptide Synthesis (SPPS)

Solid-phase peptide synthesis, pioneered by R. Bruce Merrifield, revolutionized peptide chemistry by anchoring the growing peptide chain to an insoluble polymer resin. This strategy simplifies the purification process, as excess reagents and byproducts can be washed away after each coupling step, leaving the desired peptide attached to the solid support. The iterative cycle of deprotection, coupling, and washing allows for the stepwise assembly of amino acids in a defined sequence.

For the total synthesis of nisin, SPPS offers several advantages:

* Efficiency: The ability to wash away excess reagents minimizes product loss and simplifies purification.

* Automation: SPPS is amenable to automation, allowing for the rapid synthesis of peptides and libraries of analogues作者：K Manzor·2017·被引用次数：9—A number of A-ring analogues of the lantibioticnisin, containing replacements for the Dha at position 5, have been successfully prepared bysolid-phase peptide....

* Handling of Complex Structures: The solid support can facilitate the synthesis of modified peptides and cyclic structures, which are characteristic of lantibiotics like nisin.Peptidesplay a central role in numerous biological and physiological processes. They also may be critical for research endeavors in the post-genomic and ...

Key Challenges and Strategies in Nisin Synthesis via SPPS

The total synthesis of nisin via SPPS is not without its hurdles. The unique structural features of nisin, including the presence of lanthionine (Lan) and methyllanthionine (MeLan) rings formed by post-translational modifications of cysteine and serine/threonine residues, pose significant synthetic challengesThe research details thetotal synthesis of the lantibiotic lactocin S, a natural peptide from Lactobacillus sakei, through solid-phase peptide cyclizations ....

Several strategies have been employed to overcome these difficulties:

* Pre-formed Lanthionine Building Blocks: Researchers have synthesized and incorporated pre-formed, orthogonally protected lanthionine and methyllanthionine residues directly into the peptide chain during SPPSRing-opening reactions for the solid-phase synthesis of .... This approach ensures the correct formation of these crucial thioether bridges.

* Ring-Opening Chemistry: Innovative methods involving ring-opening reactions on-resin have been developed to construct the lanthionine rings post-assembly of the linear peptide backbone. This can involve the use of specific reagents to cyclize appropriately positioned amino acid side chains.

* Microwave-Enhanced SPPS: Microwave irradiation has been utilized to accelerate coupling reactions in SPPS, leading to reduced reaction times and improved yields, particularly for challenging couplings.(a)Total synthesis of nisin by the Shiba groupusing a desulfurisation approach to generate Lan bridges and then condensing peptide fragments. (b) Using ...

* Fragment Condensation: In some instances, a segment synthesis approach, where smaller peptide fragments are synthesized independently (either on solid phase or in solution) and then coupled together, has been employed to construct the full nisin molecule. This can be particularly useful for very long or complex peptides.

* Analogue Synthesis: A significant focus of SPPS research on nisin has been the synthesis of various analogues. This includes modifications to the A-ring, replacements for dehydroalanine residues, and the creation of lipopeptide analogues. These efforts aim to understand structure-activity relationships and develop peptides with tailored properties.

Advancements and Future Directions

The continuous refinement of SPPS methodologies, coupled with advances in protecting group chemistry and cyclization strategies, has made the total synthesis of nisin and its complex analogues increasingly feasible.Solid-Phase Synthesis of C-Terminus Cysteine Peptide Acids Researchers have successfully synthesized key fragments of nisin, such as the A-ring, and have explored various strategies for constructing the lanthionine rings. The development of new reagents and solid supports continues to push the boundaries of what is achievable in peptide synthesis.

Future research in this area is likely to focus on:

* Developing more efficient and robust methods for the synthesis of lanthionine and other post-translational modifications.

* Exploring novel analogues of nisin with enhanced antimicrobial activity, improved pharmacokinetic profiles, or broader applications beyond food preservation, potentially in therapeutic settings.

* Integrating SPPS with other synthetic techniques to achieve even more complex molecular architectures.

* Investigating the biosynthesis of nisin to gain further insights that can inform and improve chemical synthesis strategies.

The total synthesis of nisin by solid phase peptide synthesis represents a triumph of modern organic chemistry, enabling detailed structural and functional studies of this important lantibiotic and paving the way for the development of new antimicrobial agents.