RW4 peptide

• Handling and Storage of Synthetic Peptides
• Material Safety Data Sheets (MSDS)

Batch to batch variation of the purity

The RW4 peptide, part of the (RW)_n series, is a synthetic cationic antimicrobial peptide composed of four repeats of arginine (R) and tryptophan (W) residues, with a C-terminal amidation. This peptide exhibits a strong interaction with negatively charged phospholipid bilayers, such as those containing phosphatidylglycerol (POPG), as demonstrated by circular dichroism spectroscopy and tryptophan fluorescence studies. The RW4 peptide shows enhanced antimicrobial activity with increasing chain length, attributed to its ability to partition into lipid membranes and disrupt bilayer integrity. Spectroscopic data indicate that RW4 undergoes conformational changes upon binding to lipid vesicles, suggesting a mechanism involving membrane intercalation.

Fluorescence studies reveal that the tryptophan residues in RW4 are more protected in POPG vesicles compared to zwitterionic phosphatidylcholine (POPC) vesicles, highlighting its preferential interaction with negatively charged membranes. The peptide's antimicrobial efficacy correlates with its chain length, with longer peptides like RW4 demonstrating greater activity. These findings underscore the importance of arginine and tryptophan residues in mediating peptide-lipid interactions and membrane disruption, providing insights into the design of short, potent antimicrobial peptides.

• Strøm et al (2002) Antimicrobial activity of short arginine- and tryptophan-rich peptides. J. Pept. Sci. 8(8) 431 PMID: 12212806
• Liu et al (2007) Length effects in antimicrobial peptides of the (RW)n series. Antimicrob. Agents Chemother. 51(2) 597 PMID: 17145799
• Mohan et al (2014) Enhanced antimicrobial activity of peptide-cocktails against common bacterial contaminants of ex vivo stored platelets. Clin. Microbiol. Infect. 20(1) O39 PMID: 23926880

Trifluoroacetic acid (TFA) has a significant impact on peptides due to its role in the peptide synthesis process.

TFA is essential for the protonation of peptides that lack basic amino acids such as Arginine (Arg), Histidine (His), and Lysine (Lys), or ones that have blocked N-termini. As a result, peptides often contain TFA salts in the final product.

TFA residues, when present in custom peptides, can cause unpredictable fluctuations in experimental data. At a nanomolar (nM) level, TFA can influence cell experiments, hindering cell growth at low concentrations (as low as 10 nM) and promoting it at higher doses (0.5–7.0 mM). It can also serve as an allosteric regulator on the GlyR of glycine receptors, thereby increasing receptor activity at lower glycine concentrations.

In an in vivo setting, TFA can trifluoroacetylate amino groups in proteins and phospholipids, inducing potentially unwanted antibody responses. Moreover, TFA can impact structure studies as it affects spectrum absorption.