Thermal characterization of antimicrobial peptide stigmurin employing thermal analytical techniques

• Published in: Journal of thermal analysis and calorimetry 2019-12, Vol.138 (5), p.3765-3779
• Main Authors: Porto, Dayanne Lopes, Leite, Geovana Quixabeira, Da Silva, Antonio Rodrigo Rodriges, Souto, Augusto Lopes, Gomes, Ana Paula Barreto, de Souza, Fábio Santos, Macêdo, Rui Oliveira, Araújo, Renata Mendonça, Cavalheiro, Éder Tadeu Gomes, Pedrosa, Matheus de Freitas Fernandes, Aragão, Cícero Flávio Soares
• Format: Article
• Language: English
• Subjects: Alcohols; Amines; Ammonia; Analytical Chemistry; Antiinfectives and antibacterials; Antimicrobial agents; Aromatic compounds; Chemistry; Chemistry and Materials Science; Condensates; Decarboxylation; Decomposition; Endothermic reactions; Ethers; Glass transition temperature; Inorganic Chemistry; Measurement Science and Instrumentation; Methicillin; Methods; Nitriles; Nitrogen; Peptides; Physical Chemistry; Polymer Sciences; Pyrolysis; Quality control; Thermal decomposition; Thermodynamic properties
• ISSN: 1388-6150; 1588-2926
• DOI: 10.1007/s10973-019-08737-0

Stigmurin is a peptide with amidated C-terminus (FFSLIPSLVGGLISAFK-NH 2 ) identified in the transcriptome of the scorpion Tityus stigmurus that has shown antimicrobial action against methicillin-resistant pathogens and low antihemolytic activity, and recently proved to be efficient in controlling sepsis. Despite its pharmacological potential, there is no report about thermal studies for the characterization of the amorphous solid. The objective of this work is to characterize stigmurin using thermoanalytical techniques in the solid state in an inert and oxidative atmosphere. Stigmurin presents glass transition temperature at 149 °C. The results of TG–FTIR and pyrolysis suggest that the pathways for decomposition include homolytic breakdown of the side chains of amino acid residues. Decomposition possibly begins at the N-terminus, with formation of the aromatic compounds, amines, nitriles, alcohols, and ethers among others followed by defragmentation reactions (mainly decarboxylation and deamination) and intramolecular condensation reactions. It generates compounds similar to 2,5-diketopiperazine or DKP, and releases water and low molecular mass products (CO 2 , NH 3 , CO, HCNO). The decomposition of stigmurin is an endothermic process where the product of decomposition is originated in the liquid state according to DSC-photovisual images. Stigmurin is more stable in nitrogen atmosphere than synthetic air. This approach provides important information about the thermal decomposition of stigmurin, a molecule endowed with potent antimicrobial activity, supplying relevant parameters (temperature, degradation products, etc.) for technological strategies focusing on quality control and development studies of preformulation involving stigmurin and synthetic peptides in general.