NMR Study of the Secondary Structure and Biopharmaceutical Formulation of an Active Branched Antimicrobial Peptide

Abstract

The synthetic antimicrobial peptide SET-M33 is being developed as a possible new antibacterial candidate for the treatment of multi-drug resistant bacteria. SET-M33 is a branched peptide featuring higher resistance and bioavailability than its linear analogues. SET-M33 shows antimicrobial activity against different species of multi-resistant Gram-negative bacteria, including clinically isolated strains of Pseudomonas aeruginosa, Klebsiella pneumoniae, Acinetobacter baumanii and Escherichia coli. The secondary structure of this 40 amino acid peptide was investigated by NMR to fully characterize the product in the framework of preclinical studies. The possible presence of helixes or β-sheets in the structure had to be explored to predict the behavior of the branched peptide in solution, with a view to designing a formulation for parenteral administration. Since the final formulation of SET-M33 will be strictly defined in terms of counter-ions and additives, we also report the studies on a new salt form, SET-M33 chloride, that retains its activity against Gram-negative bacteria and gains in solubility, with a possible improvement in the pharmacokinetic profile. The opportunity of using a chloride counter-ion is very convenient from a process development point of view and did not increase the toxicity of the antimicrobial drug.

Antimicrobial and Amyloidogenic Activity of Peptides. Can Antimicrobial Peptides Be Used against SARS-CoV-2?

“…At the same time, AMPs or host defense peptides have a potent broad-spectrum antimicrobial action against pathogenic bacteria, fungi, and viruses [ 27 ]. Thus, AMPs and their various combinations are considered as promising candidates for drugs against multidrug-resistant bacteria such as P. aeruginosa , S. aureus , K. pneumoniae or A. baumannii [ 28 , 29 , 30 ].…”

Stability and Activity of the Antimicrobial Peptide Leg1 in Solution and on Meat and Its Optimized Generation from Chickpea Storage Protein

“…In contrast, Sikora et al described divergent MIC values of AMPs depending on their counter-ions and recommended the testing of peptides with different counter-ions individually [30]. Castiglia et al did not observe any influence of acetate and chloride on MICs, but reported a better solubility of peptide chlorides [32]. In accordance with the present results, the sodium salts of TFA, acetate, and chloride did not show any antimicrobial effects in concentrations up to 1000 µM (Supplementary Materials, Table S1) confirming that the counter-ion has no influence on the antimicrobial activity of Leg1.…”

The importance of nuclear quantum effects for NMR crystallography

“…Error bars reflect ML uncertainties as well as, where applicable, statistical errors due to sampling. Experimental values [64][65][66][67][68][69] are indicated as black stars.…”

“…Fig. 2 shows a visual representation of the shifts for the polymorphs of succinic acid and glycine for which experimental data is available [64][65][66][67][68][69] (a full table is provided in the Supplemental Information). Even after internal calibration, NQEs lead to changes of the chemical shifts by up to 0.2 ppm for 1 H and 2 ppm for 13 C, in every case reducing the discrepancy with measurements.…”

“…This small difference is not reflected in significant changes in the predicted chemical shieldings for γ-glycine, indicating that the thermal expansion of the cell by around 1-2% in volume does not significantly affect σ. [65][66][67][68][69], as determined using the Bayesian framework of Ref. [59].…”