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Bozhong Mu - One of the best experts on this subject based on the ideXlab platform.
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Interaction of a biosurfactant, Surfactin with a cationic Gemini surfactant in aqueous solution
Journal of Colloid and Interface Science, 2016Co-Authors: Vasil M. Garamus, Jingwen Xiao, Helmut Eckerlebe, Regine Willumeit-römer, Bozhong MuAbstract:The interaction between biosurfactant Surfactin and cationic Gemini surfactant ethanediyl-1,3-bis(dodecyldimethylammonium bromide) (abbreviated as 12-3-12) was investigated using turbidity, surface tension, dynamic light scattering (DLS) and small angle neutron scattering (SANS). Analysis of critical micelle concentration (CMC) values in Surfactin/12-3-12 mixture indicates that there is synergism in formation of mixed Surfactin/12-3-12 micelles. Although Surfactin and 12-3-12 are oppositely charged in phosphate buffer solution (PBS, pH7.4), there are no precipitates observed at the concentrations below the CMC of Surfactin/12-3-12 system. However, at the concentration above CMC value, the Surfactin/12-3-12 mixture is severely turbid with high 12-3-12 content. DLS and SANS measurements follow the size and shape changes of mixed Surfactin/12-3-12 aggregates from small spherical micelles via elongated aggregates to large bulk complexes with increasing fraction of Gemini surfactant.
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Structural diversity of the microbial Surfactin derivatives from selective esterification approach.
International Journal of Molecular Sciences, 2015Co-Authors: Chuanshi Shao, Hong-ze Gang, Shi-zhong Yang, Bozhong MuAbstract:Surfactin originated from genus Bacillus is composed of a heptapeptide moiety bonded to the carboxyl and hydroxyl groups of a β-hydroxy fatty acid and it can be chemically modified to prepare the derivatives with different structures, owing to the existence of two free carboxyl groups in its peptide loop. This article presents the chemical modification of Surfactin esterified with three different alcohols, and nine novel Surfactin derivatives have been separated from products by the high performance liquid chromatography (HPLC). The novel derivatives, identified with Fourier transform infrared spectroscopy (FT-IR) and electrospray ionization mass spectrometry (ESI-MS), are the mono-hexyl-Surfactin C14 ester, mono-hexyl-Surfactin C15 ester, mono-2-methoxy-ethyl-Surfactin C14 ester, di-hexyl-Surfactin C14 ester, di-hexyl-Surfactin ester C15, di-2-methoxy-ethyl-Surfactin ester C14, di-2-methoxy-ethyl-Surfactin ester C15, di-6-hydoxyl-hexyl-Surfactin C14 ester and, di-6-hydoxyl-hexyl-Surfactin C15 ester. The reaction conditions for esterification were optimized and the dependence of yields on different alcohols and catalysts were discussed. This study shows that esterification is one of the most efficient ways of chemical modification for Surfactin and it can be used to prepare more derivatives to meet the needs of study in biological and interfacial activities.
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Interaction Between Surfactin and Bovine Serum Albumin
Journal of Dispersion Science and Technology, 2013Co-Authors: Bozhong MuAbstract:The interaction of Surfactin, a typical biosurfactant, with bovine serum albumin (BSA) was investigated by surface tension, fluorescence, freeze-fractured transmission electron microscopy (FF-TEM) and circular dichroism (CD) measurements. The surface tension curves of pure Surfactin solution and Surfactin/BSA solutions have different phenomena, where two obvious inflections determined as the critical aggregation concentration (cac) and the critical micelle concentration (cmc) appear for Surfactin/BSA solutions. The higher BSA concentration, the higher cac and cmc values for Surfactin/BSA solution. Fluorescence spectra show that the structure change of BSA is dependent on both Surfactin and BSA concentration. The micropolarity, FF-TEM and CD results further demonstrate the interaction between BSA and Surfactin. The excess free energy (ΔG0) of Surfactin/BSA interactions have been obtained as −6.13 and 5.32 kJ/mol for 1.0 × 10−6 and 3.8 × 10−6 mol/L BSA concentration, respectively. The binding ratio (R) dete...
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Kinetic Modeling of Esterification Reaction of Surfactin-C 15 in Methanol Solution
Applied Biochemistry and Biotechnology, 2012Co-Authors: Yue Zhao, Shi-zhong Yang, Bozhong MuAbstract:Surfactin in methanol solution with acid would be spontaneously esterified into the mono- or dimethyl ester Surfactin even at a temperature as low as 4 °C because there were two free carboxyl groups in the peptide loop of Surfactin. Using trifluoroacetic acid as the catalyst, the esterification and the contents change in Surfactin-C15, mono- and dimethyl ester Surfactin-C15 with time were investigated at 4, 25, and 45 °C, respectively. The kinetic model was established for prediction of the esterification degree under experimental conditions. At 4, 25, and 45 °C, more than 10 % of the Surfactin-C15 in methanol solution in the presence of 0.05 % trifluoroacetic acid was changed into the esterified Surfactin-C15 after 37.6, 14.1, and 7.4 h, respectively. The maximum of intermediate of the mono-methyl ester Surfactin-C15 was observed at 4, 25, and 45 °C after 25, 10, and 5 days, respectively. Our results indicated that the time for preparation should be strictly controlled to avoid an unexpected esterification of Surfactin during its storage and experimental treatment, and the kinetic results could be adopted as the reference condition for preparation of monomethyl ester Surfactin-C15.
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Molecular dynamics study of Surfactin monolayer at the air/water interface.
Journal of Physical Chemistry B, 2011Co-Authors: Hong-ze Gang, Bozhong MuAbstract:The surface parameter of protonated Surfactin molecules and the structural properties of the protonated Surfactin monolayer adsorbed at the air/water interface have been studied by molecular dynamics simulation. The simulation was performed at 293 K and the interfacial concentration of Surfactin was set in a range of 0.70–2.20 nm2 molecule–1. The results show that the interfacial concentration greatly affects the molecular orientation of Surfactin, the structure of the peptide ring backbone and the spatial arrangement of the Surfactin monolayer. The peptide ring backbone of the Surfactin molecule exhibits a structural flexibility, and a more packed structure is adopted at higher interfacial concentration. The hydrophobic contacts between Surfactin molecules and the stability of the secondary structures, β-turn structure in Leu2 → Asp5 and the β-sheet domains, are enhanced when the Surfactin molecules are in a very packed situation.
Makoto Shoda - One of the best experts on this subject based on the ideXlab platform.
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gene yerp involved in Surfactin self resistance in bacillus subtilis
Antimicrobial Agents and Chemotherapy, 2001Co-Authors: Kenji Tsuge, Yuichiro Ohata, Makoto ShodaAbstract:Certain strains of Bacillus subtilis produce Surfactin, a cyclic lipopeptide biosurfactant. Surfactin is composed of one β-hydroxy fatty acid, which has a long fatty acid moiety, and seven amino acids, three of which have d configuration. The β-hydroxy fatty acid links with a heptapeptide to form a lactone ring (2, 14, 30). Surfactin is synthesized nonribosomally by large template enzymes. The genes required for Surfactin synthesis are identified to date as the srfA operon and sfp. The srfA operon encodes the large template enzymes (5), and sfp encodes a 4′-phosphopantetheinyl transferase that posttranslationally modifies template enzymes to their functional forms (19). Since Surfactin is a strong surfactant that reduces the surface tension of water from 72 to 27 mN/m at a concentration of 20 μM (2), studies on Surfactin are focused on properties such as antitumor activity (15), activity against enveloped viruses (44), and activity against the protoplast of Bacillus megaterium (43) and against Mycoplasma (4, 45). In particular, regarding its antiviral and anti-Mycoplasma activities, Surfactin is thought to disrupt or disintegrate membranes via physicochemical interaction with the membranes, and its biotechnological and pharmaceutical applications are thus of interest (44, 45). Together with the increasing knowledge of the special biological activity of Surfactin, the question arises as to whether Surfactin is toxic to the producing strain. In general, production of antibiotics is closely associated with resistance of the producing microorganisms because these microorganisms must avoid the adverse effects of their own metabolisms. Strategies for acquisition of antibiotic resistance include elimination of the target site of the antibiotic by modification, chemical modification of the antibiotic, and efflux of the antibiotic in the cells (6). However, to date, there is no information on the mechanism of Surfactin resistance in B. subtilis. In our investigation of the gene(s) responsible for lipopeptide production in B. subtilis, we are interested in self-resistance to Surfactin, especially in efflux of the product in the environment of the cells. In this study, we used B. subtilis strain 168, which cannot produce Surfactin because of a mutation in the sfp gene (referred to as sfp0) (25). By transposon mutagenesis of this strain, we obtained a Surfactin-susceptible mutant from which yerP was identified to be the determinant of susceptibility. Moreover, we examined the relationship of yerP deficiency with Surfactin production or drug resistance.
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Isolation of new variants of Surfactin by a recombinant Bacillus subtilis
Applied Microbiology and Biotechnology, 1997Co-Authors: S. Nakayama, S. Takahashi, M. Hirai, Makoto ShodaAbstract:A recombinant Bacillus subtilis MI113(pC115), carrying a gene responsible for the production of Surfactin and iturin A cloned from B. subtilis RB14C, produced new Surfactin variants, in addition to the already reported Surfactin, when MI113(pC115) was cultured in solid-state fermentation of soybean curd residue (okara) as a substrate. All variants isolated by HPLC were characterized.
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production of a lipopeptide antibiotic Surfactin by recombinant bacillus subtilis in solid state fermentation
Biotechnology and Bioengineering, 1995Co-Authors: Akihiro Ohno, Makoto ShodaAbstract:Abstract Production of a lipopeptide antibiotic, Surfactin, in solid state fermentation (SSF) on soybean curd residue, Okara, as a solid substrate was carried out using Bacillus subtilis MI113 with a recombinant plasmid pC112, which contains lpa-14, a gene related to Surfactin production cloned at our laboratory from a wild-type Surfactin producer, B. subtilis RB14. The optimal moisture content and temperature for the production of Surfactin were 82% and 37 degrees C, respectively. The amount of Surfactin produced by MI113 (pC112) was as high as 2.0 g/kg wet weight, which was eight times as high as that of the original B. subtilis RB14 at the optimal temperature for Surfactin production, 30 degrees C. Although the stability of the plasmid showed a similar pattern in both SSF and submerged fermentation (SMF), production of Surfactin in SSF was 4-5 times more efficient than in SMF. (c) 1995 John Wiley & Sons, Inc.
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Molecular cloning of a gene responsible for the biosynthesis of the lipopeptide antibiotics iturin and Surfactin
Journal of Fermentation and Bioengineering, 1992Co-Authors: Hideji Hiraoka, Makoto ShodaAbstract:Abstract A gene responsible for the production of iturin and Surfactin was cloned and analyzed in the original wild strain Bacillus subtilis RB14, a coproducer of Surfactin and iturin, as well as in B. subtilis MI113, a derivative of strain B. subtilis 168. The cloned gene lpa (lipopeptide antibiotic production) permitted only Surfactin production in strain MI113, but when it was destroyed in RB14, the defective strain simultaneously lost the ability to produce both Surfactin and iturin. The ability was restored by the introduction of the intact lpa gene into the strain.
Chunling Wang - One of the best experts on this subject based on the ideXlab platform.
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anti inflammatory activity and mechanism of Surfactin in lipopolysaccharide activated macrophages
Inflammation, 2015Co-Authors: Yuanyuan Zhang, Bin Dong, Chunling WangAbstract:Surfactin is primarily produced by Bacillus natto TK-1 and is one of the most powerful biosurfactants. It consists of a heptapeptide interlinked with a β-hydroxy fatty acid. Because of its special structure, Surfactin shows broad biological effects, including anti-tumour, anti-microbial and anti-mycoplasma activities. It also has potential anti-inflammatory activity; however, the anti-inflammatory mechanism of Surfactin has not been explored. In this study, we investigated the anti-inflammatory mechanism of Surfactin in lipopolysaccharide (LPS)-stimulated macrophages. Surfactin exhibited an anti-inflammatory effect without cytotoxicity at certain concentrations, and the lipopolysaccharide (LPS)-stimulated cells appeared normal after Surfactin treatment. Surfactin significantly inhibited the increased expression of IFN-γ, IL-6, iNOS and nitric oxide (NO). TLR4 is the critical receptor for LPS; therefore, the TLR4 signal transduction pathway is the primary pathway that mediates LPS-induced inflammation. The results show that Surfactin downregulated the LPS-induced TLR4 protein expression of macrophages and indicated that the Surfactin-mediated signal pathway was involved in with TLR4. The subsequent studies demonstrated that Surfactin exhibited anti-inflammatory effects by attenuating the activation of nuclear factor-κB (NF-κB), which is involved in the nuclear factor-κB (NF-κB) cell signalling pathways. These results suggest that Surfactin may be a new therapeutic agent for inflammation.
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ros ca2 is associated with mitochondria permeability transition pore involved in Surfactin induced mcf 7 cells apoptosis
Chemico-Biological Interactions, 2011Co-Authors: Sisi Zhao, Zhuo Wang, Chunling WangAbstract:Abstract The Surfactin can inhibit proliferation and induce apoptosis in cancer cells. Moreover, Surfactin can induce cell death in human breast cancer MCF-7 cells through mitochondrial pathway. However, the molecular mechanism involved in this pathway remains to be elucidated. Here, the reactive oxygen species (ROS) and Ca 2+ on mitochondria permeability transition pore (MPTP) activity, and MCF-7 cell apoptosis which induced by Surfactin were investigated. It is found that Surfactin evoked mitochondrial ROS generation, and the Surfactin-induced cell death was prevented by N-acetylcysteine (NAC, an inhibitor of ROS). An increasing cytoplasmic Ca 2+ concentration was detected in Surfactin-induced MCF-7 apoptosis, which was inhibited by 1,2-bis (2-aminophenoxy) ethane-N,N,N′,N′-tetraacetic acid (BAPTA-AM, a chelator of calcium). In addition, the relationship between ROS generation and the increase of cytoplasm Ca 2+ was determined. The results showed that Surfactin initially induced the ROS formation, leading to the MPTP opening accompanied with the collapse of mitochondrial membrane potential (Δ Ψ m ). Then the cytoplasmic Ca 2+ concentration increased in virtue of the changes of mitochondrial permeability, which was prevented by BAPTA-AM. Besides, cytochrome c (cyt c) was released from mitochondria to cytoplasm through the MPTP and activated caspase-9, eventually induced apoptosis. In summary, Surfactin has notable anti-tumor effect on MCF-7 cells, however, there was no obvious cytotoxicity on normal cells.
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Surfactin induces apoptosis in human breast cancer mcf 7 cells through a ros jnk mediated mitochondrial caspase pathway
Chemico-Biological Interactions, 2010Co-Authors: Aihua Wang, Chunling Wang, Meifang Lu, Runzhi JiaoAbstract:Abstract Surfactin has been known to inhibit proliferation and induce apoptosis in cancer cells. However, the molecular mechanisms involved in Surfactin-induced apoptosis remain poorly understood. The present study was undertaken to elucidate the underlying network of signaling events in Surfactin-induced apoptosis of human breast cancer MCF-7 cells. In this study, Surfactin caused reactive oxygen species (ROS) generation and the Surfactin-induced cell death was prevented by antioxidants N-acetylcysteine (NAC) and catalase, suggesting involvement of ROS generation in Surfactin-induced cell death. Surfactin induced a sustained activation of the phosphorylation of ERK1/2 and JNK, but not p38. Moreover, Surfactin-induced cell death was reversed by PD98059 (an inhibitor of ERK1/2) and SP600125 (an inhibitor of JNK), but not by SB203580 (an inhibitor of p38). However, the phosphorylation of JNK rather than ERK1/2 activation by Surfactin was blocked by NAC/catalase. These results suggest that the action of Surfactin on MCF-7 cells was via ERK1/2 and JNK, but not via p38, and the ERK1/2 and JNK activation induce apoptosis through two independent signaling mechanisms. Surfactin triggered the mitochondrial/caspase apoptotic pathway indicated by enhanced Bax-to-Bcl-2 expression ratio, loss of mitochondrial membrane potential, cytochrome c release, and caspase cascade reaction. The NAC and SP600125 blocked these events induced by Surfactin. Moreover, the general caspase inhibitor z-VAD-FMK inhibited the caspase-6 activity and exerted the protective effect against the Surfactin-induced cell death. Taken together, these findings suggest that the Surfactin induces apoptosis through a ROS/JNK-mediated mitochondrial/caspase pathway.
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Surfactin induces apoptosis and g 2 m arrest in human breast cancer mcf 7 cells through cell cycle factor regulation
Cell Biochemistry and Biophysics, 2009Co-Authors: A H Wang, Chunling Wang, R Z Jiao, B ZengAbstract:Surfactin, purified from Bacillus subtilis natto TK-1, inhibited proliferation of human breast cancer MCF-7 cells in a dose- and time-dependent manner, with IC50 at 24, 48, and 72 h of 82.6, 27.3, and 14.8 μM, respectively. Surfactin-induced cell death was considered to be apoptotic by observing the typical apoptotic morphological change by acridine orange/ethidium bromide staining and Transferase-mediated dUTP Nick End-labeling assay. [Ca2+]i measurement revealed that Surfactin induced a sustained increase in concentration of intracellular [Ca2+]i. Flow cytometric analysis also demonstrated that Surfactin caused time-dependent apoptosis of MCF-7 cells through cell arrest at G2/M phase. Western blot revealed that Surfactin induced accumulation of the tumor suppressor p53 and cyclin kinase inhibitor p21waf1/cip1, and inhibited the activity of the G2-specific kinase, cyclin B1/p34cdc2. Based on our findings, Surfactin inhibited proliferation in MCF-7 cells by inducing apoptosis and the elevation of [Ca2+]i may play an important role in the apoptosis. The mechanism which Surfactin caused G2/M arrest seems to be through cell cycle factor regulation.
Michel Paquot - One of the best experts on this subject based on the ideXlab platform.
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molecular organization of Surfactin phospholipid monolayers effect of phospholipid chain length and polar head
Biochimica et Biophysica Acta, 2007Co-Authors: O Bouffioux, Marc Eeman, Alexandre Berquand, Yves F Dufrene, Michel Paquot, Robert Brasseur, Magali DeleuAbstract:Mixed monolayers of the surface-active lipopeptide Surfactin-C-15 and various lipids differing by their chain length (DMPC, DPPC, DSPC) and polar headgroup (DPPC, DPPE, DPPS) were investigated by atomic force microscopy (AFM) in combination with molecular modeling (Hypermatrix procedure) and surface pressure-area isotherms. In the presence of Surfactin, AFM topographic images showed phase separation for each Surfactin-phospholipid system except for Surfactin-DMPC, which was in good agreement with compression isotherms. On the basis of domain shape and line tension theory, we conclude that the miscibility between Surfactin and phospholipids is higher for shorter chain lengths (DMPC > DPPC > DSPC) and that the polar headgroup of phospholipids influences the miscibility of Surfactin in the order DPPC > DPPE > DPPS. Molecular modeling data show that mixing Surfactin and DPPC has a destabilizing effect on DPPC monolayer while it has a stabilizing effect towards DPPE and DPPS molecular interactions. Our results provide valuable information on the activity mechanism of Surfactin and may be useful for the design of Surfactin delivery systems. (c) 2007 Elsevier B.V. All rights reserved.
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Surfactin and fengycin lipopeptides of bacillus subtilis as elicitors of induced systemic resistance in plants
Environmental Microbiology, 2007Co-Authors: Marc Ongena, Michel Paquot, Emmanuel Jourdan, Akram Adam, Alain Brans, Bernard Joris, Jeanlouis Arpigny, Philippe ThonartAbstract:Summary Multiple strains of Bacillus spp. were demonstrated to stimulate plant defence responses. However, very little is known about the nature of molecular determi- nants secreted by these Gram-positive bacteria that are responsible for the elicitation of the induced systemic resistance (ISR) phenomenon. This study shows that the lipopeptides Surfactins and fengycins may be involved in this elicitation process. In bean, pure fengycins and Surfactins provided a significant ISR-mediated protective effect on bean plants, similar to the one induced by living cells of the producing strain S499. Moreover, experiments conducted on bean and tomato plants showed that overexpression of both Surfactin and fengycin biosynthetic genes in the naturally poor producer Bacillus subtilis strain 168 was associated with a significant increase in the potential of the derivatives to induce resistance. In tomato cells, key enzymes of the lipoxygenase pathway appeared to be activated in resistant plants following induction by lipopeptide overproducers. To our knowledge, such lipopeptides constitute a novel class of compounds from non-pathogenic bacteria that can be perceived by plant cells as signals to initiate defence mechanisms.
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penetration of Surfactin into phospholipid monolayers nanoscale interfacial organization
Langmuir, 2006Co-Authors: Marc Eeman, Alexandre Berquand, Yves F Dufrene, Michel Paquot, Samuel Dufour, Magali DeleuAbstract:Atomic force microscopy (AFM) combined with surface pressure-area isotherms were used to probe the interfacial behavior of phospholipid monolayers following penetration of Surfactin, a cyclic lipopeptide produced by Bacillus subtilis strains. Prior to penetration experiments, interfacial behavior of different Surfactin molecules (cyclic Surfactins with three different aliphatic chain lengths-S13, S14, and S15-and a linear Surfactin obtained by chemical cleavage of the cycle of the Surfactin S15) has been investigated. A more hydrophobic aliphatic chain induces greater surface-active properties of the lipopeptide. The opening of the peptide ring reduces the surface activity. The effect of phospholipid acyl chain length (dimyristoylphosphatidylcholine, dipalmitoylphosphatidylcholine- (DPPC), and distearoylphosphatidylcholine) and phospholipid polar head (DPPC, dipalmitoylphosphatidylethanolamine and dipalmitoylphosphatidylserine) on monolayer penetration properties of the Surfactin S15 has been explored. Results showed that while the lipid monolayer thickness and the presence of electrostatic repulsions from the interfacial film do not significantly influence Surfactin insertion, these parameters strongly modulate the ability of the Surfactin to alter the nanoscale organization of the lipid films. We also probed the effect of Surfactin structure (influence of the aliphatic chain length and of the cyclic structure of the peptide ring) on the behavior of DPPC monolayers. AFM images and isotherms showed that Surfactin penetration is promoted by longer lipopeptide chain length and a cyclic polar head. This indicates that hydrophobic interactions are of main importance for the penetration power of Surfactin molecules.
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hemolytic activity of new linear Surfactin analogs in relation to their physico chemical properties
Biochimica et Biophysica Acta, 2005Co-Authors: Samuel Dufour, Philippe Thonart, Magali Deleu, Katherine Nott, Bernard Wathelet, Michel PaquotAbstract:Abstract New linear analogs of Surfactin have been synthesized. Their physico-chemical parameters were determined. The results indicate that these linear products show surface activities although they are lowered compared to those of cyclic compounds. The hemolytic activities have also been assayed. In contrast with cyclic Surfactins, no significant hemolysis occurs for the linear products in the range of concentrations tested. Moreover, a protective effect against Triton X-100 induced hemolysis has been highlighted for linear Surfactins. The concentration at which this protective effect happens is correlated directly to the CMC, and inversely to the acyl chain length of the product. In a hypotonic medium, analogs having a long acyl chain tend to increase the hemolysis, meanwhile the product with the shortest chain tends to decrease it.
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Surface-Active Properties of Surfactin/Iturin A Mixtures Produced by Bacillus subtilis
Langmuir, 1997Co-Authors: Hary Razafindralambo, Philippe Thonart, Magali Deleu, Philippe Jacques, Yves Popineau, Choukri Hbid, Michel PaquotAbstract:Surface-active properties including dynamic adsorption, monolayer stability, micelle forming capacity, and foaming aptitudes of Surfactin-C15/iturin A-C15 mixtures were studied. Surfactin-C15 and iturin A-C15 molecules interact in synergism on the most surface-active properties evaluated at 20 °C at the air−water interface and in aqueous solution (pH 8.0). The synergism is positive on the adsorption effect, monolayer stability, foam density, and liquid stability in foam, whereas it is negative on the adsorption rate. No synergism occurs on micelle forming capacity, but Surfactin-C15 and iturin A-C15 form mixed micelles when the solution contains a low proportion of Surfactin-C15. In all cases the synergistic effect is maximum when Surfactin-C15 and iturin A-C15 molecules are mixed in a 2:3 ratio. This is attributed to the Surfactin/iturin A complex formation resulting from specific interactions among two Surfactin-C15 molecules and three iturin A-C15 molecules. A model of such a complex formation is proposed.
Hsinhui Shen - One of the best experts on this subject based on the ideXlab platform.
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Surfactin at the water air interface and in solution
Langmuir, 2015Co-Authors: Javier Iglesiasfernandez, Hsinhui Shen, Robert J Thomas, Leonardo Darre, Axel Kohlmeyer, Carmen DomeneAbstract:The lipopeptide Surfactin produced by certain strains of Bacillus subtillis is a potent biosurfactant with high amphiphilicity and a strong tendency for self-aggregation. Surfactin possesses a number of valuable biological properties such as antiviral, antibacterial, antifungal, and hemolytic activities. Owing to these properties, in addition to the general advantages of biosurfactants over synthetic surfactants, Surfactin has potential biotechnological and biomedical applications. Here, the aggregation properties of Surfactin in solution together with its behavior at the water/air interface were studied using classical molecular dynamics simulations (MD) at three different pH values. Validation of the MD structural data was performed by comparing neutron reflectivity and volume fraction profiles computed from the simulations with their experimental counterparts. Analysis of the MD trajectories supported conclusions about the distribution, conformations, and interactions of Surfactin in solution and at th...
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Surfactin at the Water/Air Interface and in Solution
Langmuir, 2015Co-Authors: Javier Iglesias-fernández, Hsinhui Shen, Robert J Thomas, Leonardo Darre, Axel Kohlmeyer, Carmen DomeneAbstract:The lipopeptide Surfactin produced by certain strains of Bacillus subtillis is a potent biosurfactant with high amphiphilicity and a strong tendency for self-aggregation. Surfactin possesses a number of valuable biological properties such as antiviral, antibacterial, antifungal, and hemolytic activities. Owing to these properties, in addition to the general advantages of biosurfactants over synthetic surfactants, Surfactin has potential biotechnological and biomedical applications. Here, the aggregation properties of Surfactin in solution together with its behavior at the water/air interface were studied using classical molecular dynamics simulations (MD) at three different pH values. Validation of the MD structural data was performed by comparing neutron reflectivity and volume fraction profiles computed from the simulations with their experimental counterparts. Analysis of the MD trajectories supported conclusions about the distribution, conformations, and interactions of Surfactin in solution and at th...
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destruction and solubilization of supported phospholipid bilayers on silica by the biosurfactant Surfactin
Langmuir, 2010Co-Authors: Hsinhui Shen, Robert J Thomas, J Penfold, Giovanna FragnetoAbstract:The lipopeptide Surfactin from Bacillus subtilis strains exhibits strong surface and biological activity, the latter probably because of its interaction with biological membranes. We have investigated the interaction of aqueous solutions of Surfactin with supported bilayers of diphosphatidylcholine (DPPC) on silica using neutron reflectometry. We have also used small-angle neutron scattering (SANS) to study the solubilized aggregates formed as a result of the destruction of the supported membrane by Surfactin. Although Surfactin on its own does not attach to the silica supporting surface, it is taken up from solution by the membrane, confirming that there is an attractive interaction between DPPC and Surfactin. The Surfactin concentration in the layer can reach up to about 20 mol % relative to DPPC. The membrane is stable provided that the Surfactin concentration is below its critical micelle concentration (cmc, 5 × 10−5 M). Above the cmc, however, the membrane is solubilized and removed from the surface,...
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aggregation of the naturally occurring lipopeptide Surfactin at interfaces and in solution an unusual type of surfactant
Langmuir, 2009Co-Authors: Hsinhui Shen, Robert J Thomas, Chienyen Chen, Richard C Darton, Simon C Baker, J PenfoldAbstract:Neutron reflectometry has been used to study the structure of the biosurfactant, Surfactin, at the air/water and at the hydrophobic solid/water interfaces. Three different deuterated Surfactins were produced from the Bacillus subtilis strain: one perdeuterated, one with the four leucines perdeuterated, and one with everything except the four leucines perdeuterated. The neutron reflectivity profiles of these three samples in null reflecting water and in D2O with a seventh profile of the protonated Surfactin in D2O were measured at pH 7.5. This combination of different isotopic compositions made it possible to deduce the distribution of each type of labeled fragment in the Surfactin. Surfactin is found to adopt a ball-like structure with a thickness of 14 ± A and an area per molecule of 147 ± 5 A2. This makes it more like a hydrophobic nanoparticle, whose solubility in water is maintained only by its charge, than a conventional surfactant. This is probably what makes it surface-active at such low concentrat...
