Biomolecular interactions of lysosomotropic surfactants with cytochrome c and its effect on the protein conformation: A biophysical approach

The molecular interactions between two single-chain lysosomotropic surfactants DMM-11 (2-Dodecanoyloxyethyl)trimethylammonium bromide) and DMPM-11 (2-Dodecanoyloxypropyl)trimethylammonium bromide) with a small heme-protein (cytochrome c (cyt-c)) in Hepes buffer (pH = 7.4) were extensively investigated by surface tension, dynamic light scattering (DLS), circular dichroism (CD) and fluorescence spectroscopy in combination with molecular dynamic simulation techniques. The results demonstrated that surfactants can destroy the hydrophobic cavity of cyt-c, make the α-helical become loose and convert it into the β-sheet structure. The interactions between surfactants and cyt-c are mainly hydrophobic. Molecular modelling approaches were also used to gather a deeper insight on the binding of lysosomotropic surfactants with cyt-c and the in silico results were found to be in good agreement with the experimental ones. This study provides a molecular basis for the applications of protein-surfactant complexes in biological, food, pharmaceutical, industrial and cosmetic systemsPolish-Portugal Executive Program for years 2017–2018 sponsored by the Polish Ministry of Science and Higher Education and by the Portuguese Foundation for Science and Technology (FCT). Additionally, FCT supported the study under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684). T. Janek was supported by the National Science Centre, Poland, projects 2017/26/E/NZ9/00975 and 2018/02/X/NZ6/02201. L. R. Rodrigues acknowledges FCT for the grant SFRH/BSAB/142873/2018. E. J. Gudiña was supported by the grant UMINHO/BPD/39/2015 funded by FCT under the scope of the project UID/BIO/04469/2013info:eu-repo/semantics/publishedVersio

Study of metal-lipopeptide complexes and their self-assembly behavior, micelle formation, interaction with bovine serum albumin and biological properties

The present study aimed to explore the interactions of divalent counterions with biomolecular amphisin using circular dichroism (CD), ultravioletvisible (UVVis) and density functional theory (DFT). The binding mode of interactions between metal-amphisin complexes and bovine serum albumin (BSA) were studied using fluorescence spectroscopy. The results showed that Cu2+ is coordinated by one oxygen atom of the aspartic acid side chain and three amide nitrogen atoms, whereas Zn2+, Ca2+ and Mg2+ favour the association with backbone oxygen atoms of the amphisin. On the other hand, the aggregation of amphisin induced by divalent counterions was studied by dynamic light scattering (DLS). Our results revealed that the self-assembly process of amphisin can be controlled by the addition of metal ions. The results of CD spectra demonstrated that the binding of divalent counterions to the lipopeptide induces conformational changes in amphisin. Further studies using fluorescence spectroscopy showed that the metal-lipopeptide systems could interact with some functional groups of BSA, increasing the microenvironment around Trp residues of BSA. Thus, the interaction data acquired herein for the interesting class of complexes will be of significance in metal-based drug discovery and developmental research.This work was supported by Polish-Portugal Executive Program for years 2017–2018. Lígia Rodrigues acknowledges the Portuguese Foundation for Science and Technology (FCT) for the financial support under the scope of the strategic funding of SFRH/BSAB/142873/2018, UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684). Żaneta Czyżnikowska gratefully acknowledges the allotment of the CPU time in Wroclaw Center of Networking and Supercomputing (WCSS).info:eu-repo/semantics/publishedVersio

Metal-biosurfactant complexes characterization: binding, self-assembly and interaction with bovine serum albumin

Studies on the specific and nonspecific interactions of biosurfactants with proteins are broadly relevant given the potential applications of biosurfactant/protein systems in pharmaceutics and cosmetics. The aim of this study was to evaluate the interactions of divalent counterions with the biomolecular anionic biosurfactant surfactin-C15 through molecular modeling, surface tension and dynamic light scattering (DLS), with a specific focus on its effects on biotherapeutic formulations. The conformational analysis based on a semi-empirical approach revealed that Cu2+ ions can be coordinated by three amide nitrogens belonging to the surfactin-C15 cycle and one oxygen atom of the aspartic acid from the side chain of the lipopeptide. Backbone oxygen atoms mainly involve Zn2+, Ca2+ and Mg2+. Subsequently, the interactions between metal-coordinated lipopeptide complexes and bovine serum albumin (BSA) were extensively investigated by fluorescence spectroscopy and molecular docking analysis. Fluorescence results showed that metal-lipopeptide complexes interact with BSA through a static quenching mechanism. Molecular docking results indicate that the metal-lipopeptide complexes are stabilized by hydrogen bonding and van der Waals forces. The biosurfactant-protein interaction properties herein described are of significance for metal-based drug discovery hypothesizing that the association of divalent metal ions with surfactin allows its interaction with bacteria, fungi and cancer cell membranes with effects that are similar to those of the cationic peptide antibiotics.This work was supported by the National Science Centre, Poland, projects 2018/02/X/NZ6/02201 and 2017/26/E/NZ9/00975. Publication supported by Wrocław Centre of Biotechnology, program the Leading National Research Centre (KNOW) for years 2014–2018.info:eu-repo/semantics/publishedVersio

Structure and mode of action of cyclic lipopeptide pseudofactin II with divalent metal ions

"Available online 28 June 2016"The interaction of natural lipopeptide pseudofactin II with a series of doubly charged metal cations was examined by matrixassisted laserdesorption ionizationtime of flight (MALDI-TOF) mass spectrometry and molecular modelling. The molecular modelling for metal-pseudofactin II provides information on the metalpeptide binding sites. Overall, Mg2+, Ca2+ and Zn2+ favor the association with oxygen atoms spanning the peptide backbone, whereas Cu2+ is coordinated by three nitrogens. Circular dichroism (CD) results confirmed that Zn2+ and Cu2+ can disrupt the secondary structure of pseudofactin II at high concentrations, while Ca2+ and Mg2+ did not essentially affect the structure of the lipopeptide. Interestingly, our results showed that the addition of Zn2+ and Cu2+ helped smaller micelles to form larger micellar aggregates. Since pseudofactin II binds metals, we tested whether this phenomena was somehow related to its antimicrobial activity against Staphylococcus epidermidis and Proteus mirabilis. We found that the antimicrobial effect of pseudofactin II was increased by supplementation of culture media with all tested divalent metal ions. Finally, by using Gram-positive and Gram-negative bacteria we showed that the higher antimicrobial activity of metal complexes of pseudofactin II is attributed to the disruption of the cytoplasmic membrane.Fundação para a Ciência e Tecnologia (FCT) for the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684

Physicochemical study of biomolecular interactions between lysosomotropic surfactants and bovine serum albumin

The interactions between two cationic lysosomotropic surfactants (2-dodecanoyloxyethyl)trimethylammonium bromide (DMM-11) and (2-dodecanoyloxypropyl)trimethylammonium bromide (DMPM-11) with bovine serum albumin (BSA) in Hepes buffer (pH = 7.4) were systematically studied by surface tension, fluorescence and circular dichroism (CD) spectroscopy and isothermal titration calorimetry (ITC). Furthermore, the size of the micellar aggregates and the polydispersity indexes of both cationic surfactants were studied by dynamic light scattering technique (DLS). The hydrodynamic radii, micellar volumes and aggregation numbers were calculated using a method based on density functional theory (DFT). The results showed that, in both cases, the surface tension was modified upon addition of BSA, and the critical micelle concentration (CMC) values of DMM-11 and DMPM-11 were higher in the presence of BSA. The fluorescence intensity of BSA decreased significantly as the concentration of both cationic surfactants increased and this effect was attributed to the formation of surfactant-BSA complexes. Synchronous fluorescence spectrometry showed the binding-induced conformational changes in BSA. Finally, CD and DLS results revealed the occurrence of changes in the secondary structure of the protein in the presence of both surfactants. In conclusion, understanding the interactions between lysosomotropic surfactants and BSA is required to explore their potential applications in medicine.Author Żaneta Czyżnikowska gratefully acknowledge the allotment of the CPU time in Wroclaw Center of Networking and Supercomputing (WCSS). All the ITC experiments were performed by Joanna Gałęzowska in the Laboratory of Elemental Analysis and Structural Research, Faculty of Pharmacy and the Division of Laboratory Diagnostics, Wroclaw Medical University, supported by the ERDF Project within the Innovation Economy Operational Programme POIG.02.01.00-14-122/09”. Ligia R. Rodrigues and Eduardo J. Gudiña acknowledge the Portuguese Foundation for Science and Technology (FCT) for the financial support under the scope of the strategic funding of UID/BIO/04469/2013 unit and COMPETE 2020 (POCI-01-0145-FEDER-006684) and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 − Programa Operacional Regional do Norte. The authors also thank the FCT for the financial support under the scope of the Project RECI/BBB-EBI/0179/2012 (FCOMP-01-0124-FEDER-027462). This work was supported by Polish-Portugal Executive Program for years 2017-2018.info:eu-repo/semantics/publishedVersio