Circular Aqueous Fmoc/t-Bu Solid-Phase Peptide Synthesis

Exploring Tryptophan-based Short Peptides: Promising Candidate for Anticancer and Antimicrobial Therapies

BACKGROUND

Ultra-short peptides are essential therapeutic agents due to their heightened selectivity and reduced toxicity. Scientific literature documents the utilization of dipeptides, tripeptides, and tetrapeptides as promising agents for combating cancer. We have created a range of tryptophan-based peptides derived from literature sources in order to assess their potential as anticancer drugs.

METHODS

We present the results of our study on the antibacterial and anticancer effectiveness of 10 ultra-short peptides that were produced utilizing microwave-assisted solid phase peptide synthesis. The synthesized peptides underwent screening for in vitro antibacterial activity using the agar dilution method.

RESULTS

HPLC, LC-MS, 1H NMR, and 13C NMR spectroscopy were used to analyze the synthesized peptides. In tests using the HeLa and MCF-7 cell lines, the synthesized peptides' anticancer efficacy was assessed. The study found that two peptides showed potential median inhibitory concentration (IC50) values of 3.9±0.13 μM and 1.8±0.09 μM, respectively, and showed more activity than the reference medication doxorubicin.

CONCLUSION

The antibacterial activity of synthesized peptides 3b and 4b was found to be better than the other synthetic peptides. MIC value of roughly 5-50 μg/mL for peptides 3a, 4c, and 4d showed strong antifungal activity against Candida albicans. The synthesized peptides were also evaluated for their anticancer activity against HeLa and MCF-7 cell lines, and found that peptides 3e and 4e were more potent than other peptides against doxorubicin.

Total wash elimination for solid phase peptide synthesis

We present a process for solid phase peptide synthesis (SPPS) that completely eliminates all solvent intensive washing steps during each amino acid addition cycle. A key breakthrough is the removal of a volatile Fmoc deprotection base through bulk evaporation at elevated temperature while preventing condensation on the vessel surfaces with a directed headspace gas flushing. This process was demonstrated at both research and production scales without any impact on product quality and when applied to a variety of challenging sequences (up to 89 amino acids in length). The overall result is an extremely fast, high purity, scalable process with a massive waste reduction (up to 95%) while only requiring 10-15% of the standard amount of base used. This transformation of SPPS represents a step-change in peptide manufacturing process efficiency, and should encourage expanded access to peptide-based therapeutics.

Suppression of alpha-carbon racemization in peptide synthesis based on a thiol-labile amino protecting group

In conventional solid-phase peptide synthesis (SPPS), α-amino groups are protected with alkoxycarbonyl groups (e.g., 9-fluorenylmethoxycarbonyl [Fmoc]). However, during SPPS, inherent side reactions of the protected amino acids (e.g., α-C racemization and aspartimide formation) generate by-products that are hard to remove. Herein, we report a thiol-labile amino protecting group for SPPS, the 2,4-dinitro-6-phenyl-benzene sulfenyl (DNPBS) group, which is attached to the α-amino group via a S-N bond and can be quantitatively removed in minutes under nearly neutral conditions (1 M p-toluenethiol/pyridine). The use of DNPBS greatly suppresses the main side reactions observed during conventional SPPS. Although DNPBS SPPS is not as efficient as Fmoc SPPS, especially for synthesis of long peptides, DNPBS and Fmoc are orthogonal protecting groups; and thus DNPBS SPPS and Fmoc SPPS can be combined to synthesize peptides that are otherwise difficult to obtain.

Pramod S, T. Prabhakar B, B.N. Naika M, G. Thippeswamy T, Niranjana P. Characterization and biochemical activities of novel functional antimicrobial peptide (AMP) from Trichogramma chilonis

Introduction and Aim: The antimicrobial peptides (AMPs) are generally found in invertebrates, mammals, birds, plants and insects. AMPs produced by insect parasitoids contribute to innate immunity to resist infection due to lack of adaptive immunity. T. chilonis is one of the most effective endoparasitoid wasps for controlling lepidopterous insects. Several attempts have been made to isolate, characterize and develop a commercially viable product of AMPs from various insect sources. The present study aimed to characterize AMP from T. chilonis for potential antimicrobial and anti-cancer properties.    Methods: AMP was identified through T. chilonis transcriptome sequence and designed in silico and synthesized. Its purity was quantified using RP-HPLC, and the mass identified by mass spectrophotometry. LC/MS-MS was employed to predict the sequence and the BLAST program used to compare the sequence. AMP was tested for haemolytic activity and antimicrobial activity. Two pathogenic bacteria and fungal strains were used and IC50 values and MIC values were predicted against microbial strains.    Results: Synthetic peptide was found to be 95% homogenous with molecular weight of 3.48 kD.  The peptide was identified to be a novel antimicrobial peptide consisting of 33 amino acid residues, and has a low computed instability index of -0.1.55 with high hydrophobic ratio of 27.27%. The antimicrobial activity revealed that T. chilonis antimicrobial peptide (TC-AMP) strongly inhibits the growth of selected human bacterial and fungal pathogens. While the haemolytic assay showed that the peptide did not obliterate human RBC in vitro. TC-AMP also showed an efficient inhibition of angiogenesis by in vivo model as evident by inhibition of vascularization.   Conclusions: AMP derived from the parasitoid has a potent antibiotic and anti-angiogenesis property. The peptide can be used as a potential antimicrobial and anticancer drug in near future with more detailed studies on its targeted applications.

Electrochemistry for the Chemoselective Modification of Peptides and Proteins

Although electrochemical strategies for small-molecule synthesis are flourishing, this technology has yet to be fully exploited for the mild and chemoselective modification of peptides and proteins. With the growing number of diverse peptide natural products being identified and the emergence of modified proteins as therapeutic and diagnostic agents, methods for electrochemical modification stand as alluring prospects for harnessing the reactivity of polypeptides to build molecular complexity. As a mild and inherently tunable reaction platform, electrochemistry is arguably well-suited to overcome the chemo- and regioselectivity issues which limit existing bioconjugation strategies. This Perspective will showcase recently developed electrochemical approaches to peptide and protein modification. The article also highlights the wealth of untapped opportunities for the production of homogeneously modified biomolecules, with an eye toward realizing the enormous potential of electrochemistry for chemoselective bioconjugation chemistry.