C-Terminal Aliphatic Acid Modified Alpha-Defensin 5 Variant
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Solution Overview
Problem
Current antibacterial drugs face challenges in effectively targeting broad-spectrum and extended-spectrum drug-resistant bacteria, with human defensin-5 (HD-5) being influenced by environmental factors like sodium chloride, limiting its industrial and clinical application.
Innovation Solution
A human α-defensin 5 variant is created by modifying the C-terminal with aliphatic acid chains, enhancing its bactericidal activity and stability, allowing it to form a micellar structure for stronger binding to bacteria, thus overcoming the limitations of natural HD-5.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If natural HD-5 is used as an antibacterial peptide, then it has broad spectrum antibacterial activity, but its activity is extremely reduced by sodium chloride in physiological concentration
Solution Approach 1:
The patent modifies the C-terminal parameters of HD-5 by adding amino acid residues and conjugating aliphatic acid chains with 8-24 carbon atoms. This parameter change transforms the peptide's physical and chemical properties, enabling it to resist sodium chloride inhibition while maintaining antibacterial activity. The modified structure allows the peptide to function reliably in physiological saline environments where natural HD-5 fails.
Solution Approach 2:
The patent creates a composite structure by conjugating aliphatic acid chains to the C-terminal of HD-5. This composite modification combines the antibacterial properties of HD-5 with the salt-resistant characteristics of the aliphatic acid-modified structure, producing a hybrid peptide that overcomes the limitations of natural HD-5 in saline environments.
2Reliability
If HD-5 is modified to improve salt resistance, then bactericidal potency increases, but the molecular structure becomes more complex
Solution Approach 1:
The modification strategy segments the molecular complexity into two distinct functional parts: the original HD-5 core structure that provides antibacterial activity, and the C-terminal aliphatic acid addition that provides salt resistance. This segmentation allows each part to perform its specific function without interfering with the other, achieving enhanced overall performance with manageable structural complexity.
Solution Approach 2:
The patent applies local quality modification by specifically targeting the C-terminal region of HD-5 for aliphatic acid conjugation. This localized modification approach improves salt resistance and bactericidal potency at the C-terminal without altering the essential antibacterial structure of the N-terminal and central regions, thereby achieving enhanced function with minimal structural complexity increase.
3Reliability
If aliphatic acid chains with 8-24 carbon atoms are conjugated to C-terminal, then salt resistance and bactericidal activity are enhanced, but manufacturing process becomes more difficult
Solution Approach 1:
The patent employs preliminary action by first extending the C-terminal with amino acid residues to create a ready-to-conjugate structure, then subsequently conjugating the aliphatic acid chain. This stepwise preliminary preparation simplifies the overall manufacturing process by creating intermediate structures that are easier to handle and modify, reducing the complexity of the final conjugation step compared to direct aliphatic acid attachment to native HD-5.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The modified variant, HD-5Myr and HD-5Lau, exhibit significantly improved bactericidal potency against drug-resistant bacteria, including MRSA and E. coli, with enhanced salt-resistance and immunomodulatory effects, making them suitable for novel antibacterial and immunomodulatory agents.
Implementation Method 1
convert it into a cationic amphipathic self-assembly nano-antibacterial peptide
Implementation Method 2
The action mechanism of cationic antibacterial peptides relates to positive charges carried thereon, which can bind to bacterial surface with negative charges
Data Source
AI summary
A human α-defensin 5 variant is obtained by adding amino acid residues at C-terminal of α-defensin 5 and then being modified to link an aliphatic acid. At least one of the added amino acid residues has a free amino group, and the free amino group is modified to link an aliphatic acid with 8-24 carbon atoms. The variant is used in manufacture of an antibacterial agent and an immunomodulatory agent. Antibacterial activity is significantly enhanced by extending and modifying the C-terminal of HD-5; in particular, salt tolerance is significantly improved by extending the C-terminal of HD-5 with Lys and then being modified with myristic acid, thereby breaking the restriction of salt-sensibility of conventional antimicrobial peptides. The variant can significantly promote release of inflammatory factors from macrophages and thus can be applied in manufacture of immunomodulatory agent.