Francisco J Aranda

Jundi Shapur University of Technology, Nāşerī, Khūzestān, Iran

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Publications (83)275.32 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Abstract Organotin compounds, such as tri-n-butyltin(IV) chloride (TBT), are widespread toxicants which disrupt different functions in living organisms. TBT interacts with lipid membranes and membrane proteins. The inhibition of the calcium ATPase from sarcoplasmic reticulum membranes (SERCA1) by TBT was studied. It was found that the ATPase inhibition could not be reverted in a large time scale, moreover, an excess of TBT over enzyme did not fully inhibit the ATPase activity, therefore it was concluded that TBT irreversibly inhibits the enzyme, and this inhibition is accompanied by a decrease in the effective TBT concentration. The residual ATP hydrolysis activity was measured at different TBT concentrations with time, and the protective effect of different calcium concentrations on the TBT inhibition was also determined. The simplest kinetic mechanism to successfully explain all the observations and the kinetic behavior was found to be a single irreversible step of the inhibitor binding to the enzyme accompanied with a first-order inhibitor inactivation. A fluorescence study of fluorescein-5-isothiocyanate (FITC) labeled enzyme revealed that TBT binding to the enzyme entails a conformational change related to the high to low affinity calcium binding state transition (E1 to E2 transition), resembling the conformational change induced by vanadate linked to the formation of E2V complex from E1 state. A docking study allowed us to propose a binding pocket for TBT in the membrane region of E1 close to the high affinity calcium binding sites, as well as to define the interactions with amino acid residues interfering with calcium sites occupancy.
    Journal of biomolecular Structure & Dynamics 07/2014; · 2.98 Impact Factor
  • José A Teruel, Antonio Ortiz, Francisco J Aranda
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    ABSTRACT: Trehalose lipids are bacterial biosurfactants which present interesting physicochemical and biological properties. These glycolipids have a number of different commercial applications and there is an increasing interest in their use as therapeutic agents. The amphiphilic nature of trehalose lipids points to the membrane as their hypothetical site of action and therefore the study of the interaction between these biosurfactants and biological membranes is critical. In this study, we examine the interactions between a trehalose lipid (TL) from Rhodococcus sp. and dimyristoylphosphatidylglycerol (DMPG) membranes at low ionic strength, by means of differential scanning calorimetry, light scattering, fluorescence polarization and infrared spectroscopy. We describe that there are extensive interactions between TL and DMPG involving the perturbation of the thermotropic intermediate phase of the phospholipid, the destabilization and shifting of the DMPG gel to liquid crystalline phase transition to lower temperatures, the perturbation of the sample transparency, and the modification of the order of the phospholipid palisade in the gel phase. We also report an increase of fluidity of the phosphatidylglycerol acyl chains and dehydration of the interfacial region of the bilayer. These changes would increase the monolayer negative spontaneous curvature of the phospholipid explaining the destabilizing effect on the intermediate state exerted by this biosurfactant. The observations contribute to get insight into the biological mechanism of action of the biosurfactant and help to understand the properties of the intermediate phase display by DMPG at low ionic strength.
    Chemistry and Physics of Lipids 04/2014; · 2.59 Impact Factor
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    ABSTRACT: Catechin flavonoids are the main components of green tea extracts which present broad potential physiological activities. Several of their biological activities seem to affect membrane-dependent cellular processes and it is known that some catechins interact with phospholipid membranes. In this study we examine the interactions of a 3-O-(3,4,5-trimethoxybenzoyl)-(-)-catechin (TMCG), and its quinone methide (QM) activated product with 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) membranes by means of differential scanning calorimetry, X-ray diffraction, Fourier-Transform infrared spectroscopy and molecular dynamics simulation. We report that there are extensive interactions between TMCG and DPPC involving the perturbation of the thermotropic gel to liquid crystalline phase transition of the phospholipid, the decrease of bilayer thickness and the promotion of interdigitated gel phase, together with an increase of the hydrogen bonding pattern of the interfacial region of the bilayer. In contrast, QM shows a weak interaction with the phospholipid bilayer. Molecular dynamics simulation indicates that TMCG locates in the interior of the bilayer, while QM is found interacting with the surface of the membrane. The observations are interpreted in terms of the mechanism of membrane prodrug activation and the underlying membrane perturbations of the biological actions of natural catechins.
    Biochimica et Biophysica Acta 02/2014; · 4.66 Impact Factor
  • Ana Zaragoza, José A Teruel, Francisco J Aranda, Antonio Ortiz
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    ABSTRACT: Trehalose-containing glycolipid biosurfactants form an emerging group of interesting compounds, which alter the structure and properties of phospholipid membranes, and interact with enzymatic and non-enzymatic proteins. Phospholipases A2 constitute a class of enzymes that hydrolyze the sn-2 ester of glycerophospholipids, and are classified into secreted phospholipases A2 (sPLA2) and intracellular phospholipases A2. In this work, pancreatic sPLA2 was chosen as a model enzyme to study the effect of the trehalose lipid biosurfactant on enzymes acting on interfaces. By using this enzyme, it is possible to study the modulation of enzyme activity, either by direct interaction of the biosurfactant with the protein, or as a result of the incorporation of the glycolipid on the phospholipid target membrane. It is shown that the succinoyl trehalose lipid isolated from Rhodococcus erythropolis 51T7 interacts with porcine pancreatic sPLA2 and inhibits its catalytic activity. Two modes of inhibition are observed, which are clearly differentiated by its timescale. First, a slow inhibition of sPLA2 activity upon preincubation of the enzyme with trehalose lipid in the absence of substrate is described. Second, incorporation of trehalose lipid into the phospholipid target membrane gives rise to a fast enzyme inhibition. These results are discussed in the light of previous data on sPLA2 inhibitors and extend the list of interesting biological activities reported for this R. erythropolis trehalose lipid biosurfactant.
    Journal of Colloid and Interface Science 07/2013; · 3.55 Impact Factor
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    ABSTRACT: The commercial application of biosurfactants in the biomedical field has increased in the past decade due to their antimicrobial activity, low cytotoxicity and ability to induce apoptosis in cancer cells. In the light of this therapeutic potential, as well as possible applications in cosmetics or as drug vehicles in pharmaceutical products, a new biosurfactant produced by Sphingobacterium detergens was investigated for its haemolytic activity and cytotoxic and antiproliferative effects in different cell lines. Fraction A showed 100% haemolysis in rabbit erythrocytes, but in Fraction B the rate was only 83% (115-fold lower). When comparing cytotoxicity values (IC50) of the two fractions in model fibroblast and keratinocyte cell cultures, Fraction B was less cytotoxic, showing lower values than the reference compound SDS, indicating low skin irritability. Finally, in non-differentiated intestinal Caco-2 cultures, Fractions A and B reduced cell proliferation and induced apoptosis by 44% and 75%, respectively. According to these results, biosurfactants produced by S. detergens have potential application in cosmetic and pharmaceutical formulations.
    International Journal of Pharmaceutics 06/2013; · 3.99 Impact Factor
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    ABSTRACT: This work presents a biophysical study on the interactions of a monorhamnolipid (monoRL) produced by Pseudomonas aeruginosa MA01 with model dielaidoylphosphatidyl-ethanolamine (DEPE) membranes. Incorporation of monoRL into DEPE shifts the onset temperature of the Lβ-to-Lα and the Lα-to-HII phase transitions toward lower values. Incorporation of monoRL into DEPE indicates the coexistence of lamellar and hexagonal-HII phases in rhamnolipid-containing samples at 60°C, at which pure DEPE is lamellar. Thus, both techniques show that monoRL facilitates formation of the hexagonal-HII phase in DEPE, i.e. it destabilizes the bilayer organization. The phase diagram for the phospholipid component indicates a near-ideal behavior, with better miscibility of monoRL into DEPE in the fluid phase than in the gel phase. The various vibrational modes bands of the acyl chains of DEPE were studied by FTIR spectroscopy, focusing on the CH2 symmetric stretching mode. Incorporation of monoRL into DEPE shifts the frequency of this band to higher wavenumbers, at temperatures both below and above the main gel to liquid-crystalline phase transition. Examination of the C=O stretching band of DEPE indicates that monoRL/DEPE interactions result in an overall dehydration effect on the polar headgroup of DEPE. These results are discussed on the light of the possible role of rhamnolipids as bilayer stabilizers/destabilizers during cell membrane fluctuations events.
    Biochimica et Biophysica Acta 05/2013; · 4.66 Impact Factor
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    ABSTRACT: The commercial application of a new biosurfactant such as the one produced by Sphingobacteriumdetergens needs a cost-effective process and knowledge of its properties. In the present study, a specific medium and a downstream process have been developed to enhance biosurfactant production. Optimal concentrations of nutrients in MCA medium were (g/L) the following: KH(2)PO(4), 1; K(2)HPO(4), 2; CO(NH(2))(2) 0.88; CaCl(2) 0.01; FeSO(4)·7H(2)O, 0.01; MgSO(4)·7H(2)O 0.5; KCl, 1.0; trace elements 0.05mL. Biosurfactant production in the MCA medium required a bacterial co-metabolism of glucose and an n-alkane. A fed-batch culture with supernatant lyophilization prior to organic extraction produced 466mg/L of organic extract, which represents a 6.9-fold increase in production. The newly obtained biosurfactant was a complex mixture of molecules. The three characterized fractions consisted of the complete fraction and two second-level purification fractions with apolar and polar characteristics. The complete and apolar fractions have been shown to self-aggregate in the form of lamellar liquid crystals at a high concentration and bilayers at lower concentrations. Negatively charged particles were identified, which were neutralized at a low pH with a concomitant increase in size. The pH affected the surface tension of the solutions congruently with phosphate headgroups.
    Journal of Colloid and Interface Science 12/2012; · 3.55 Impact Factor
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    ABSTRACT: A novel Gram-negative strain, designated as 6.2ST, was isolated from a soil sample and identified as a biosurfactant producer. Its taxonomic position was investigated using a polyphasic approach. The cells were non-motile, non-spore-forming rods. The organism grew optimally at 30-37°C, with 0-3% NaCl, and at pH 7.0. Based on 16S rRNA gene sequence analysis, strain 6.2ST was found to be a member of the genus Sphingobacterium and is most closely related to four type species of the genus, showing sequence similarities of 96.8-98.9%. Partial chaperonin 60 (cpn60) gene sequence analysis was useful in resolving phylogenetic relationships between strain 6.2ST and closely related taxa, with similarities ranging from 85.5% (with S. thalpophilum DSM 11723T) to 90.3% (with S. canadense CR11T and S. multivorum JCM 21156T). Furthermore, the results of DNA-DNA hybridization experiments were clearly lower than 70% DNA-DNA similarity, and consequently confirmed that this new strain does not belong to a previously described species of the genus Sphingobacterium. The major fatty acids were summed feature 3 (iso- C15:0 2 OH and/or C16:1 w7c) (43.71%); iso-C15:0 (20.91%); iso-C17:0 3-OH (7.40%) and C16:0 (7.33%). The G+C content of the genomic DNA was 40.0 mol%. According to its phenotypic and genotypic characteristics and phylogenetic data, strain 6.2ST represents a novel species of the genus Sphingobacterium, for which the name Sphingobacterium detergens sp. nov. is proposed. The type strain is 6.2ST (= CECT 7938T = LMG 26465T).
    INTERNATIONAL JOURNAL OF SYSTEMATIC AND EVOLUTIONARY MICROBIOLOGY 02/2012; · 2.11 Impact Factor
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    ABSTRACT: The interaction of the organotin compounds trimethyltin(IV) and tributyltin(IV) chlorides with the calcium pump from sarcoplasmic reticulum membranes was studied. It was found that the presence of calcium fully protects against the inhibitory effect of both organotin compounds. However, the apparent affinity of the protein for tributyltin chloride is two orders of magnitude higher than for trimethyltin chloride (K 0.5 values of 14 µ m and 1.4 m m, respectively). Studies of intrinsic fluorescence of the Ca2+‐ATPase and enzyme phosphorylation by ATP and Pi support the hypothesis that the inhibitory properties of trialkyltin compounds are due to the inhibition of calcium binding to the high‐affinity binding sites of the Ca2+‐ATPase. This suggests that there is a specific interaction between the trialkyltin compounds and the calcium binding sites of the protein. The effect of trialkyltin compounds on Ca2+‐ATPase was also addressed by differential scanning calorimetry to assess the thermal transition of the protein denaturation, and by infrared spectroscopy in the absorption region corresponding to the amide I band (1600–1700 cm−1) to observe changes in the secondary structure of the protein. We conclude that the interaction of trialkyltin compounds with Ca2+‐ATPase reduces the affinity and cooperativity for calcium binding and, consequently, the inhibition of ATPase activity. These events are accompanied by changes in the secondary structure of the protein, including loss of α‐helix structure and a concomitant increase in protein aggregation or unfolding. The activity of trialkyltin compounds on the Ca2+‐ATPase is discussed in relation to their solubility in water and in the lipid phase. Copyright © 2012 John Wiley & Sons, Ltd.
    Applied Organometallic Chemistry 01/2012; 26(11). · 2.01 Impact Factor
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    ABSTRACT: One major application of surfactants is to prevent aggregation during various processes of protein manipulation. In this work, a bacterial trehalose lipid (TL) with biosurfactant activity, secreted by Rhodococcus sp., has been identified and purified. The interactions of this glycolipid with selected model proteins have been studied by using differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy, isothermal titration calorimetry (ITC), and fluorescence spectroscopy. Bovine serum albumin (BSA) and cytochrome c (Cyt-c) have been chosen because of their quite different secondary structures: BSA contains essentially no β-sheets and an average 66% α-helix, whereas Cyt-c possesses up to 25% β-sheets and up to 45% α-helical structure. Differential scanning calorimetry shows that addition of TL to BSA at concentrations below the critical micelle concentration (cmc) shifts the thermal unfolding temperature to higher values. FTIR indicates that TL does not alter the secondary structure of native BSA, but the presence of TL protects the protein toward thermal denaturation, mainly by avoiding formation of β-aggregates. Studies on the intrinsic Trp fluorescence of BSA show that addition of TL to the native protein results in conformational changes. BSA unfolding upon thermal denaturation in the absence of TL makes the Trp residues less accessible to the quencher, as shown by a decrease in the value of Stern-Volmer dynamic quenching constant, whereas denaturation in the presence of the biosurfactant prevents unfolding, in agreement with FTIR results. In the case of Cyt-c, interaction with TL gives rise to a new thermal denaturation transition, as observed by DSC, at temperatures below that of the native protein, therefore facilitating thermal unfolding. Binding of TL to native BSA and Cyt-c, as determined by ITC, suggests a rather nonspecific interaction of the biosurfactant with both proteins. FTIR indicates that TL slightly modifies the secondary structure of native Cyt-c, but protein denaturation in the presence of TL results in a higher proportion of β-aggregates than in its absence (20% vs 3.9%). The study of Trp fluorescence upon TL addition to Cyt-c results in a completely opposite scenario to that described above for BSA. In this case, addition of TL considerably increases the value of the dynamic quenching constant, both in native and denatured protein; that is, the interaction with the glycolipid induces conformational changes which facilitate the exposure of Trp residues to the quencher. Considering the structures of both proteins, it could be derived that the characteristics of TL interactions, either promoting or avoiding thermal unfolding, are highly dependent on the protein secondary structure. Our results also suggest the rather unspecific nature of these interactions. These might well involve protein hydrophobic domains which, being buried into the protein native structures, become exposed upon thermal unfolding.
    Langmuir 12/2011; 28(2):1381-90. · 4.38 Impact Factor
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    ABSTRACT: Bacterial trehalose lipids are biosurfactants with potential application in the biomedical/healthcare industry due to their interesting biological properties. Given the amphiphilic nature of trehalose lipids, the understanding of the molecular mechanism of their biological action requires that the interaction between biosurfactant and membranes is known. In this study we examine the interactions between a trehalose lipid from Rhodococcus sp. and dimyristoylphosphatidylglycerol membranes by means of differential scanning calorimetry, X-ray diffraction, infrared spectroscopy and fluorescence polarization. We report that there are extensive interactions between trehalose lipid and dimyristoylphosphatidylglycerol involving the perturbation of the thermotropic gel to liquid-crystalline phase transition of the phospholipid, the increase of fluidity of the phosphatidylglycerol acyl chains and dehydration of the interfacial region of the bilayer, and the modulation of the order of the phospholipid bilayer. The observations are interpreted in terms of structural perturbations affecting the function of the membrane that might underline the biological actions of the trehalose lipid.
    Biochimica et Biophysica Acta 08/2011; 1808(8):2067-72. · 4.66 Impact Factor
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    ABSTRACT: Strain 6.2S, isolated from soil and identified as a Sphingobacterium sp., is the first strain in this genus to be reported as a biosurfactant producer, being able to reduce the surface tension of its culture supernatant to 32 mN/m. In this work, biosurfactants from the culture supernatant were purified and partially characterized. The crude extract (10 g/L) was very effective in reducing surface tension (22 mN/m). Thin layer chromatography (TLC) indicated that a mixture of various biosurfactants was present in the 6.2S crude extract. After purification, Fraction A, a phospholipid mixture, reduced surface tension to 33 mN/m. Fraction B was a mixture of lipopetides and at least one glycolipid. The surface tension-concentration curve showed two plateaux, the first of which can be attributed to a critical aggregation concentration of the biosurfactant with a protein (2.7 g/L) and the second to the true cmc in water (6.3g/L).
    Journal of Colloid and Interface Science 05/2011; 361(1):195-204. · 3.55 Impact Factor
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    ABSTRACT: The effect of sterols composition in a lipid bilayer was investigated on membranes of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and mixtures with the plant sterols β-sitosterol and stigmasterol. Differential scanning calorimetry, 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence polarization and infrared spectroscopy studies showed that both sterols changed the packing of the membrane and the hydration of the polar headgroup of the phospholipids, disordering the gel phase and, vice versa, ordering the membrane in the liquid crystalline phase. In all cases some differences among β-sitosterol and stigmasterol could be observed, being β-sitosterol slightly more efficient than stigmasterol in ordering a fluid membrane, bringing the membrane to a more packed liquid ordered phase. Molecular dynamic simulations were carried out to better characterize the distinct behavior of both sterols in a DPPC-membrane. The calculated parameters agreed quite well with the experimental results and a molecular model is proposed to explain differences in the sterols molecules and their effect on the DPPC-bilayer.
    Journal of Colloid and Interface Science 02/2011; 358(1):192-201. · 3.55 Impact Factor
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    ABSTRACT: Phosphatidylethanolamine-based pH-sensitive liposomes of various compositions have been described as efficient systems for cytoplasmic delivery of molecules into cells. Incorporation of an amphiphile of appropriate structure is needed for the stabilization and performance of these vesicles. Among the wide variety of interesting activities displayed by Pseudomonas aeruginosa dirhamnolipids (diRL), is their capacity to stabilize bilayer structures in phosphatidylethanolamine systems. In this work, X-ray scattering, dynamic light scattering, fluorescence spectroscopy and fluorescence microscopy have been used to study the structure and pH-dependent behaviour of phosphatidylethanolamine/diRL liposomes. We show that diRL, in combination with dioleoylphosphatidylethanolamine (DOPE), forms stable multilamellar and unilamellar liposomes. Acidification of DOPE/diRL vesicles leads to membrane destabilization, fusion, and release of entrapped aqueous vesicle contents. Finally, DOPE/diRL pH-sensitive liposomes act as efficient vehicles for the cytoplasmic delivery of fluorescent probes into cultured cells. It is concluded that DOPE/diRL form stable pH-sensitive liposomes, and that these liposomes are incorporated into cultured cells through the endocytic pathway, delivering its contents into the cytoplasm, which means a potential use of these liposomes for the delivery of foreign substances into living cells. Our results establish a new application of diRL as a bilayer stabilizer in phospholipid vesicles, and the use of diRL-containing pH-sensitive liposomes as delivery vehicles.
    Chemistry and Physics of Lipids 10/2010; 164(1):16-23. · 2.59 Impact Factor
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    ABSTRACT: Curcumin is a polyphenol present in turmeric, a spice widely used in Asian traditional medicine and cooking. It has many and diverse biological effects and is incorporated in cell membranes. This paper describes the mode in which curcumin modulates the physical properties of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dielaidyl-sn-glycero-3-phosphoetnanolamine (DEPE) multilamellar membranes. Curcumin disordered DPPC membranes at temperatures below T(c) as seen by DSC, FT-IR, (2)H NMR, WAXD, and SAXD. The decrease induced by curcumin in T(c) suggested that it is oriented in the bilayer with its main axis parallel to the acyl chains. Above T(c), too, curcumin introduced disorder as seen by infrared spectroscopy which showed that curcumin also alters the conformation of the polar group of DPPC, increasing the percentage of unhydrated C=O groups, but does not form hydrogen bonds with either the C=O group or the phosphate group of DPPC. Small angle X-ray diffraction showed a notable increase in the repeating spacings as a result of the presence of curcumin, suggesting the formation of a rippled phase. Increasing concentrations of curcumin progressively modified the onset and completion of the phase transition and also DeltaH up to a 6:1 DPPC/curcumin molar ratio. A further increase of curcumin concentration did not produce effects on the transition parameters, suggesting that there is a limit for the solubility of curcumin in DPPC. Additionally, when DEPE was used to test the effect of curcumin on the phospholipid polymorphism, it was found that the temperature at which the H(II) phase is formed decreased, indicating that curcumin favors negative curvature of the membrane, which may be important for explaining its effect on membrane dynamics and on membrane proteins or on proteins which may be activated through membrane insertion.
    The Journal of Physical Chemistry B 08/2010; 114(30):9778-86. · 3.61 Impact Factor
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    ABSTRACT: Curcumin is a polyphenol present in turmeric, widely used in Asian traditional medicine and cooking, which has many and diverse biological effects and is found incorporated in membranes. We have studied the mode in which curcumin modulates the physical properties of 1, 2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) multilamellar membranes and 1, 2-dielaidoyl-sn-glycero-3-phosphoetnanolamine (DEPE). Curcumin disordered DPPC membranes at temperatures below Tc as seen through DSC, FT-IR, 2H-NMR, WAXD and SAXD.
    Biophysical Journal, 54th Annual Meeting Biophysical Society, San Francisco, USA; 02/2010
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    ABSTRACT: A succinoyl trehalose lipid produced by Rhodococcus sp. behaves as a biological surfactant and also displays various interesting biological activities. Trehalose lipid has been shown to have a great tendency to partition into phospholipid membranes; therefore, the characterization of its interaction with biological membranes is of central importance. In this work, human red blood cells have been used as an experimental model. Trehalose lipid causes the swelling of human erythrocytes followed by hemolysis at concentrations well below its critical micellar concentration. Kinetic measurements show that, upon addition of trehalose lipid, K(+) release precedes that of hemoglobin. Osmotic protectants of the appropriate size added to the external medium make it possible to avoid hemolysis. The results indicate that trehalose lipid causes the hemolysis of human erythrocytes by a colloid-osmotic mechanism, most likely by formation of enhanced permeability domains, or "pores" enriched in the biosurfactant, within the erythrocyte membrane. Scanning electron microscopy shows trehalose lipid-induced spherocytosis and echinocytosis of red blood cells, which fits well within the framework of the bilayer-couple hypothesis. The presented results contribute to establishing a molecular basis for the biological properties of this trehalose lipid biosurfactant.
    Langmuir 02/2010; 26(11):8567-72. · 4.38 Impact Factor
  • Antonio Ortiz, Francisco J Aranda, Jose A Teruel
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    ABSTRACT: Rhamnolipids are bacterial biosurfactants produced by Pseudomonas spp. These compounds have been shown to present several interesting biological activities and to have potential applications as therapeutics agents. It has been suggested that the interaction with the membrane could be the ultimate responsible for these actions. Therefore it is of great interest to get insight into the molecular mechanism of the interaction of purified rhamnolipids with the various phospholipid components of biological membranes. In this work, the CMC of a purified bacterial dirhamnolipid was determined both by isothermal titration calorimetry and surface tension measurements. The partition coefficients from water to membranes of different compositions, as well as the corresponding thermodynamic parameters, indicated that membrane partitioning was an entropically driven process. Interaction of dirhamnolipid with phospholipids was studied by means of calorimetry, FTIR and X-ray diffraction. It is shown this interaction had various effects that might constitute the molecular basis to explain the former activities: domain formation with lateral phase separation, increased motional disorder of the phospholipid acyl chains and dehydration of the aqueous interface. Our results suggest that dirhamnolipid, having a large polar headgroup and a smaller hydrophobic portion, behaves as an inverted-cone shaped molecule, conferring positive curvature to membranes, which might be behind its disrupting effects on membranes.
    Advances in experimental medicine and biology 01/2010; 672:42-53. · 1.83 Impact Factor
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    ABSTRACT: Pseudomonas aeruginosa, when cultured under the appropriate conditions, secretes rhamnolipids to the external medium. These glycolipids constitute one of the most interesting classes of biosurfactants so far. A dirhamnolipid fraction was isolated and purified from the crude biosurfactant, and its action on model and biological membranes was studied. Dirhamnolipid induced leakage of internal contents, as measured by the release of carboxyfluorescein, in phosphatidylcholine unilamellar vesicles, at concentrations below its CMC. Membrane solubilization was not observed within this concentration range. The presence of inverted cone-shaped lipids in the membrane, namely lysophosphatidylcholine, accelerated leakage, whereas cone-shaped lipids, like phosphatidylethanolamine, decreased leakage rate. Increasing concentrations of cholesterol protected the membrane against dirhamnolipid-induced leakage, which was totally abolished by the presence of 50 mol% of the sterol. Dirhamnolipid caused hemolysis of human erythrocytes through a lytic mechanism, as shown by the similar rates of K(+) and hemoglobin leakage, and by the absence of effect of osmotic protectants. Scanning electron microscopy showed that the addition of the biosurfactant changed the usual disc shape of erythrocytes into that of spheroechinocytes. The results are discussed within the frame of the biological actions of dirhamnolipid, and the possible future applications of this biosurfactant.
    Journal of Colloid and Interface Science 09/2009; 341(2):240-7. · 3.55 Impact Factor
  • New Biotechnology 09/2009; 25. · 1.71 Impact Factor

Publication Stats

972 Citations
275.32 Total Impact Points

Institutions

  • 2013
    • Jundi Shapur University of Technology
      Nāşerī, Khūzestān, Iran
  • 1982–2013
    • University of Murcia
      • • Department of Biochemistry and Molecular Biology I
      • • Department of Biochemistry and Molecular Biology B and Immunology
      • • Facultad de Veterinaria
      • • Facultad de Medicina
      Murcia, Murcia, Spain
  • 2011
    • University of Tarapacá
      • Departamento de Recursos Ambientales
      Arica, Region de Arica y Parinacota, Chile
  • 2008–2011
    • University of Barcelona
      • Facultad de Farmacia
      Barcelona, Catalonia, Spain