Cell death plays a homeostatic role in the life of a multicellular organism such as in removing d... more Cell death plays a homeostatic role in the life of a multicellular organism such as in removing damaged, unwanted, or excess cells, and aiding the normal development of organisms. Pyroptosis is an immunomodulatory form of regulated cell death that is mediated by the poreforming action of the gasdermin protein family, and has been linked to various diseases including cancer, neurodegeneration, and infection. Targeting pyroptosis therefore could have potential therapeutic benefit, for instance, via the inhibition of its execution. In this regard, marine-derived compounds can offer possible novel structures and scaffolds by which potential pyroptosis inhibitors can be designed. In this study 153 mareine-derived compounds were investigated for their in silico interaction with the NLRP3 inflammasome NACHT domain through molecular docking, ADMET profiling, and key interaction analysis. Docking of the compounds on the target protein based on a previously solved co-crystal structure yielded binding free energy (BFE) values between-10.8 to 82 kcal/mol. Interactions of the topperforming compounds with critical protein residues were predominantly non-covalent in
Novel protein-based nanomaterials are gaining much interest in recent years due in large part to ... more Novel protein-based nanomaterials are gaining much interest in recent years due in large part to their more environment-friendly preparation schemes coupled with promising biological activities. Although nanoparticles synthesized from protein sources are not new, various researches are still continuously investigating other potential templates and sources of new protein-based materials. In this study, Ag nanoclusters capped with crude protein extracts from the sea anemone Heteractis magnifica (H. magnifica) were prepared via one-pot, green synthesis, and subjected to preliminary biological activity testing. Fourier transform infrared spectroscopy (FTIR) analysis indicated successful capping of the nanoclusters, consistent with previous reports utilizing similar synthetic protocols, while scanning electron microscopy (SEM) revealed the presence of more aggregates on the surface of the prepared nanoclusters. Formation of the nanoclusters resulted in a slight to moderate antibacterial, but not antifungal, activity, although the material also showed a concentration-dependent hemolytic action. In contrast, the unmodified extract did not show any antimicrobial action while being more hemolytic as well. These results demonstrate the potential of these protein-capped Ag nanoclusters as antibacterial agents, although its unwanted hemolytic side effect will have to be reduced for it to have any therapeutic potential.
Novel nanomaterials derived from numerous biological samples including extracts from plants, anim... more Novel nanomaterials derived from numerous biological samples including extracts from plants, animals, and even bacteria have gained prominence due to their unique properties, more environmental friendly preparation, and interesting bioactivities. Among these, protein-capped noble metal, e.g., Ag, nanoclusters (NC) have gained considerable attention for their many potential applications, and significant efforts are being directed at using a wide variety of protein sources as capping agents as well as. In this work, crude protein extracts from the sea anemone Entacmaea quadricolor (E. quadricolor) subjected to either heat or β-mercaptoethanol denaturation were prepared to investigate the effects of these processes in the formation of AgNC and on its preliminary bioactivity, measured using a hemolysis assay against human erythrocytes. Fourier-transform infrared spectrometry (FTIR) analysis showed comparable spectra for the two denatured crude protein-capped AgNC, as well with as the undenatured protein-capped AgNC, like previous reports indicating successful capping of the NC. Moreover, the spectra suggest no significant alterations if protein secondary structure upon NC formation. The crude protein extracts were also found to be very weakly hemolytic at the concentration range tested (0.5-1 mg protein/mL) and denaturing the protein prior to NC formation did not significantly alter its hemolytic activity as well. These results imply that E. quadricolor crude protein denaturation prior to use with the reduction of Ag + has no deleterious effects in functioning as capping agents for the prepared AgNC.
Ferroptosis is an iron-dependent form of regulated necrosis associated with lipid peroxidation. D... more Ferroptosis is an iron-dependent form of regulated necrosis associated with lipid peroxidation. Despite its key role in the inflammatory outcome of ferroptosis, little is known about the molecular events leading to the disruption of the plasma membrane during this type of cell death. Here we show that a sustained increase in cytosolic Ca 2+ is a hallmark of ferroptosis that precedes complete bursting of the cell. We report that plasma membrane damage leading to ferroptosis is associated with membrane nanopores of few nanometers in radius and that ferroptosis, but not lipid peroxidation, can be delayed by osmoprotectants. Importantly, Ca 2+ fluxes during ferroptosis correlate with the activation of ESCRT-III-mediated membrane repair, which counterbalances the kinetics of cell death and modulates the inflammatory signature of ferroptosis. Our findings with ferroptosis provide a unifying concept that sustained high levels of cytosolic Ca 2+ prior to plasma membrane disruption are a common feature of regulated necrosis and position ESCRT-III as a general protective mechanism in these inflammatory cell death pathways.
Advances in biomembranes and lipid self-assembly, 2019
Abstract Necroptosis is a form of regulated cell death that critically depends on the function of... more Abstract Necroptosis is a form of regulated cell death that critically depends on the function of Mixed Lineage Kinase Domain-Like Pseudokinase (MLKL). MLKL activation triggers plasma membrane permeabilization and other cellular processes aimed at preparing necroptotic cells to communicate with its neighbors and stimulate inflammation and immunogenicity. Membrane repair mechanisms play a key role in delaying necroptosis, by compensating the lethal effect of MLKL. Tuning the regulation of MLKL activities and counterbalancing machineries can define cell fate and the way the immune system is activated. Beside necroptosis, other forms of cell death are also notable for their impact on the plasma membrane and their role at engaging the immune system. Understanding the principles that govern plasma membrane reorganization is crucial to regulate their diverse immunological outcomes. Here we review current knowledge about the involvement of MLKL in mediating necroptosis and compare it with other lytic types of cell death.
Reaction of 1-bromobutane was investigated using Fenton reagent. This reagent is known to be a go... more Reaction of 1-bromobutane was investigated using Fenton reagent. This reagent is known to be a good oxidant for organic pollutants, which is composed of Fe2+ and H2O2. The reaction products that were identified were: 1-bromo-2-butanol, 1-butanoyl bromide, 1,3-dibromobutane, 1,4-dibromobutane, and 1,1,1-tribromobutane. This was verified by separating and analyzing the reaction mixture by GC/MS. Mechanisms were proposed for the formation of the products of the reaction of 1-bromobutane and Fenton reagent
Chicken meat consumption remains high in the Philippines, and consequently, annual chicken produc... more Chicken meat consumption remains high in the Philippines, and consequently, annual chicken production has risen steadily over the years. Although most of the chicken meat available in the market are sourced from factory farms, there has been growing popularity of free-range chicken production, largely driven by its perceived health benefits and sanitation concerns in factory farms, among others. In this work, we aimed at comparing the trace metal (copper, iron, lead, manganese, and zinc) content of free-range and factory-farmed broiler chicken meat that are being sold in Laguna, Philippines. The samples were subjected to acid digestion and analysis was done using atomic absorption spectrometry. Results showed an average concentration between 0.17 – 0.24 mg/kg, 2.22 – 2.34 mg/kg, 0.12 – 0.15 mg/kg, 0.95 – 1.32 mg/kg, and 1.81 – 1.96 mg/kg for copper, iron, lead, manganese, and zinc, respectively. Statistical analysis using one-way ANOVA and Tukey multiple comparison test (p < 0.05...
Scheme 6-1 Schematic diagram of TNM-A isolation from sponge. Scheme 6-2 Schematic diagram of AM3 ... more Scheme 6-1 Schematic diagram of TNM-A isolation from sponge. Scheme 6-2 Schematic diagram of AM3 isolation from harvested A. klebsii cells. Scheme 6-3 Two-state reaction model.
Marine organisms are a very good source of unique bioactive secondary metabolites, although they ... more Marine organisms are a very good source of unique bioactive secondary metabolites, although they have been comparatively underexplored relative to their terrestrial counterparts. Preliminary investigation of crude extracts from the fire coral Millepora dichotoma revealed that the hemolytic potential of the MeOH extract, at a concentration of 5 mg/mL, was significantly lower at less than 5% hemolysis while DCM extract at the same concentration resulted to almost 100% hemolysis. Furthermore, antimicrobial assay revealed that the MeOH extract (5 mg/mL) mildly inhibited the fungi T. mentagrophytes and resulted in the thinning of growth of S. aureus, while DCM extracts showed no detectable activity against these organisms. These results demonstrated that MeOH extracts of M. dichotoma, without showing hemolytic side effects, could be further analysed for potential use against T. mentagrophytes and S. aureus infections.
Chemical investigation of the dichloromethane extract of the fire coral, Millepora dichotoma yiel... more Chemical investigation of the dichloromethane extract of the fire coral, Millepora dichotoma yielded β-sitosterol (1), triacylglycerols (2), and wax esters (3). The structures of 1-3 were identified by comparison of their NMR data with literature data.
Cholesterol-dependent cytolysins (CDCs) are proteinaceous toxins secreted as monomers by some Gra... more Cholesterol-dependent cytolysins (CDCs) are proteinaceous toxins secreted as monomers by some Gram-positive and Gram-negative bacteria that contribute to their pathogenicity. These toxins bind to either cholesterol or human CD59, leading to massive structural changes, toxin oligomerization, formation of very large pores, and ultimately cell death, making these proteins promising targets for inhibition. Myricetin, and its related flavonoids, have been previously identified as a candidate small molecule inhibitor of specific CDCs such as listeriolysin O (LLO) and suilysin (SLY), interfering with their oligomerization. In this work, molecular docking was performed to assess the interaction of myricetin with other CDCs whose crystal structures are already known. Results indicated that although myricetin bound to the hitherto identified cavity in domain 4 (D4), much more efficient and stable binding was obtained in sites along the interfacial regions of domains 1 – 3 (D1 – D3). This was ...
Zeitschrift fur Naturforschung. C, Journal of biosciences, Jan 9, 2016
Amphidinol 3 (AM3) and theonellamide A (TNM-A) are potent antifungal compounds produced by the di... more Amphidinol 3 (AM3) and theonellamide A (TNM-A) are potent antifungal compounds produced by the dinoflagellate Amphidinium klebsii and the sponge Theonella spp., respectively. Both of these metabolites have been demonstrated to interact with membrane lipids ultimately resulting in a compromised bilayer integrity. In this report, the activity of AM3 and TNM-A in ternary lipid mixtures composed of 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine (POPC):brain sphingomyelin:cholesterol at a mole ratio of 1:1:1 or 3:1:1 exhibiting lipid rafts coexistence is presented. It was found that AM3 has a more extensive membrane permeabilizing activity compared with TNM-A in these membrane mimics, which was almost complete at 15 μM. The extent of their activity nevertheless is similar to the previously reported binary system of POPC and cholesterol, suggesting that phase separation has neither beneficial nor detrimental effects in their ability to disrupt the lipid bilayer.
Algal biofuels serve as a promising alternative energy source for liquid fuels. However, one of t... more Algal biofuels serve as a promising alternative energy source for liquid fuels. However, one of the bottlenecks in the conversion of microalgae to biofuels is the drying process. A moisture content of at most 10 % is desired for algal biomass prior to oil extraction to maximise biofuel yield. Conventional means of drying results to longer drying time and uneven drying of algal biomass. This study investigated the drying characteristics of microwave for microalgae (Chlorella vulgaris). Three microwave intensity levels (300, 600, and 900 W) were considered to dry 10, 20, and 30 of algal mass. Page model gave a better fit on the moisture ratio with time of microwave drying than the exponential model. Furthermore, the specific energy requirement was computed, and a relationship was found between moisture ratio with power and mass. Fourier transform infrared spectroscopy results showed significant reduction of infrared signal intensities of the functional groups present in the algae after drying at higher microwave power level. It was concluded that the 20 W/g microwave drying setting gave a lower specific energy requirement with good quality of remaining high lipid content qualitatively. Furthermore, it was recommended to use gas chromatography mass spectroscopy to further quantify the algal lipids and other functional groups.
SummaryFerroptosis is an iron-dependent form of regulated necrosis associated with lipid peroxida... more SummaryFerroptosis is an iron-dependent form of regulated necrosis associated with lipid peroxidation. Despite its key role in the inflammatory outcome of ferroptosis, little is known about the molecular events leading to the disruption of the plasma membrane during this type of cell death. Here we show that a sustained increase in cytosolic Ca2+ is a hallmark of ferroptosis that precedes complete bursting of the cell. We report that plasma membrane damage leading to ferroptosis is associated with membrane nanopores of few nanometers in radius and that ferroptosis, but not lipid peroxidation, can be delayed by osmoprotectants. Importantly, Ca2+ fluxes during ferroptosis correlate with the activation of ESCRT-III-mediated membrane repair, which counterbalances the kinetics of cell death and modulates the inflammatory signature of ferroptosis. Our findings with ferroptosis provide a unifying concept that sustained high levels of cytosolic Ca2+ prior to plasma membrane disruption are a...
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2019
Theonellamide a, a marine-sponge-derived bicyclic peptide, binds to cholesterol in aqueous DMSO: ... more Theonellamide a, a marine-sponge-derived bicyclic peptide, binds to cholesterol in aqueous DMSO: Solution NMR-based analysis of peptide-sterol interactions using hydroxylated sterol. Bbamem (2018),
Theonellamide A (TNM-A) is an antifungal bicyclic dodecapeptide isolated from a marine sponge The... more Theonellamide A (TNM-A) is an antifungal bicyclic dodecapeptide isolated from a marine sponge Theonella sp. Previous studies have shown that TNM-A preferentially binds to 3βhydroxysterol-containing membranes and disrupts membrane integrity. In this study, several 1 H NMR-based experiments were performed to investigate the interaction mode of TNM-A with model membranes. First, the aggregation propensities of TNM-A were examined using diffusion ordered spectroscopy; the results indicate that TNM-A tends to form oligomeric aggregates of 2-9 molecules (depending on peptide concentration) in an aqueous environment, and this aggregation potentially influences the membrane-disrupting activity of the peptide. Subsequently, we measured the 1 H NMR spectra of TNM-A with sodium dodecyl sulfate-d 25 (SDS-d 25) micelles and small dimyristoylphosphatidylcholine (DMPC)d 54 /dihexanoylphosphatidylcholine (DHPC)-d 22 bicelles in the presence of a paramagnetic quencher Mn 2+. These spectra indicate that TNM-A poorly binds to these membrane mimics without sterol and mostly remains in the aqueous media. In contrast, broader 1 H signals of TNM-A were observed in 10 mol% cholesterol-containing bicelles, indicating that the peptide efficiently binds to sterol-containing bilayers. The addition of Mn 2+ to these bicelles also led to a decrease in the relative intensity and further line-broadening of TNM-A signals, indicating that the peptide stays near the surface of the bilayers. A comparison of the relative signal intensities with those of phospholipids showed that TNM-A resides in the lipid-water interface (close to the C2 portion of the phospholipid acyl chain). This shallow penetration of TNM-A to lipid bilayers induces an uneven membrane curvature and eventually disrupts membrane integrity. These results shed light on the atomistic mechanism accounting for the membrane-disrupting activity of TNM-A and the important role of cholesterol in its mechanism of action. Sterol-Dependent Membrane Association of the Marine Sponge-Derived Bicyclic Peptide Theonellamide A as Examined by 1H NMR
Theonellamides (TNMs) are antifungal and cytotoxic bicyclic dodecapeptides derived from the marin... more Theonellamides (TNMs) are antifungal and cytotoxic bicyclic dodecapeptides derived from the marine sponge Theonella sp. These peptides specifically bind to 3β-hydroxysterols, resulting in 1,3-β-d-glucan overproduction and membrane damage in yeasts. The inclusion of cholesterol or ergosterol in phosphatidylcholine membranes significantly enhanced the membrane affinity of theonellamide A (TNM-A) because of its direct interaction with 3β-hydroxyl groups of sterols. To better understand TNM-induced membrane alterations, we investigated the effects of TNM-A on liposome morphology. (31)P nuclear magnetic resonance (NMR) and dynamic light scattering (DLS) measurements revealed that the premixing of TNM-A with lipids induced smaller vesicle formation. When giant unilamellar vesicles were incubated with exogenously added TNM-A, confocal micrographs showed dynamic changes in membrane morphology, which were more frequently observed in cholesterol-containing than sterol-free liposomes. In conju...
Amphidinol 3 (AM3), a polyhydroxy-polyene metabolite from the dinoflagellate Amphidinium klebsii,... more Amphidinol 3 (AM3), a polyhydroxy-polyene metabolite from the dinoflagellate Amphidinium klebsii, possesses potent antifungal activity. Although AM3 permeabilizes phospholipid membranes only in the presence of sterol, the detailed molecular basis by which AM3 recognizes sterols in membranes remains unknown. Here, we investigated the molecular interaction between sterols and AM3 in membranes from the viewpoint of stereospecific molecular recognition using ergosterol, cholesterol, and epicholesterol, which is the 3-OH epimer of cholesterol. Dye leakage assays, surface plasmon resonance experiments, 2 H and 31 P NMR measurements, and microscopic observations revealed that AM3 directly interacts with membrane sterols through the strict molecular recognition of the stereochemistry of the sterol 3-OH group. The direct interaction enhances the membrane binding efficiency of AM3, which subsequently permeabilizes membranes without altering membrane integrity.
Cell death plays a homeostatic role in the life of a multicellular organism such as in removing d... more Cell death plays a homeostatic role in the life of a multicellular organism such as in removing damaged, unwanted, or excess cells, and aiding the normal development of organisms. Pyroptosis is an immunomodulatory form of regulated cell death that is mediated by the poreforming action of the gasdermin protein family, and has been linked to various diseases including cancer, neurodegeneration, and infection. Targeting pyroptosis therefore could have potential therapeutic benefit, for instance, via the inhibition of its execution. In this regard, marine-derived compounds can offer possible novel structures and scaffolds by which potential pyroptosis inhibitors can be designed. In this study 153 mareine-derived compounds were investigated for their in silico interaction with the NLRP3 inflammasome NACHT domain through molecular docking, ADMET profiling, and key interaction analysis. Docking of the compounds on the target protein based on a previously solved co-crystal structure yielded binding free energy (BFE) values between-10.8 to 82 kcal/mol. Interactions of the topperforming compounds with critical protein residues were predominantly non-covalent in
Novel protein-based nanomaterials are gaining much interest in recent years due in large part to ... more Novel protein-based nanomaterials are gaining much interest in recent years due in large part to their more environment-friendly preparation schemes coupled with promising biological activities. Although nanoparticles synthesized from protein sources are not new, various researches are still continuously investigating other potential templates and sources of new protein-based materials. In this study, Ag nanoclusters capped with crude protein extracts from the sea anemone Heteractis magnifica (H. magnifica) were prepared via one-pot, green synthesis, and subjected to preliminary biological activity testing. Fourier transform infrared spectroscopy (FTIR) analysis indicated successful capping of the nanoclusters, consistent with previous reports utilizing similar synthetic protocols, while scanning electron microscopy (SEM) revealed the presence of more aggregates on the surface of the prepared nanoclusters. Formation of the nanoclusters resulted in a slight to moderate antibacterial, but not antifungal, activity, although the material also showed a concentration-dependent hemolytic action. In contrast, the unmodified extract did not show any antimicrobial action while being more hemolytic as well. These results demonstrate the potential of these protein-capped Ag nanoclusters as antibacterial agents, although its unwanted hemolytic side effect will have to be reduced for it to have any therapeutic potential.
Novel nanomaterials derived from numerous biological samples including extracts from plants, anim... more Novel nanomaterials derived from numerous biological samples including extracts from plants, animals, and even bacteria have gained prominence due to their unique properties, more environmental friendly preparation, and interesting bioactivities. Among these, protein-capped noble metal, e.g., Ag, nanoclusters (NC) have gained considerable attention for their many potential applications, and significant efforts are being directed at using a wide variety of protein sources as capping agents as well as. In this work, crude protein extracts from the sea anemone Entacmaea quadricolor (E. quadricolor) subjected to either heat or β-mercaptoethanol denaturation were prepared to investigate the effects of these processes in the formation of AgNC and on its preliminary bioactivity, measured using a hemolysis assay against human erythrocytes. Fourier-transform infrared spectrometry (FTIR) analysis showed comparable spectra for the two denatured crude protein-capped AgNC, as well with as the undenatured protein-capped AgNC, like previous reports indicating successful capping of the NC. Moreover, the spectra suggest no significant alterations if protein secondary structure upon NC formation. The crude protein extracts were also found to be very weakly hemolytic at the concentration range tested (0.5-1 mg protein/mL) and denaturing the protein prior to NC formation did not significantly alter its hemolytic activity as well. These results imply that E. quadricolor crude protein denaturation prior to use with the reduction of Ag + has no deleterious effects in functioning as capping agents for the prepared AgNC.
Ferroptosis is an iron-dependent form of regulated necrosis associated with lipid peroxidation. D... more Ferroptosis is an iron-dependent form of regulated necrosis associated with lipid peroxidation. Despite its key role in the inflammatory outcome of ferroptosis, little is known about the molecular events leading to the disruption of the plasma membrane during this type of cell death. Here we show that a sustained increase in cytosolic Ca 2+ is a hallmark of ferroptosis that precedes complete bursting of the cell. We report that plasma membrane damage leading to ferroptosis is associated with membrane nanopores of few nanometers in radius and that ferroptosis, but not lipid peroxidation, can be delayed by osmoprotectants. Importantly, Ca 2+ fluxes during ferroptosis correlate with the activation of ESCRT-III-mediated membrane repair, which counterbalances the kinetics of cell death and modulates the inflammatory signature of ferroptosis. Our findings with ferroptosis provide a unifying concept that sustained high levels of cytosolic Ca 2+ prior to plasma membrane disruption are a common feature of regulated necrosis and position ESCRT-III as a general protective mechanism in these inflammatory cell death pathways.
Advances in biomembranes and lipid self-assembly, 2019
Abstract Necroptosis is a form of regulated cell death that critically depends on the function of... more Abstract Necroptosis is a form of regulated cell death that critically depends on the function of Mixed Lineage Kinase Domain-Like Pseudokinase (MLKL). MLKL activation triggers plasma membrane permeabilization and other cellular processes aimed at preparing necroptotic cells to communicate with its neighbors and stimulate inflammation and immunogenicity. Membrane repair mechanisms play a key role in delaying necroptosis, by compensating the lethal effect of MLKL. Tuning the regulation of MLKL activities and counterbalancing machineries can define cell fate and the way the immune system is activated. Beside necroptosis, other forms of cell death are also notable for their impact on the plasma membrane and their role at engaging the immune system. Understanding the principles that govern plasma membrane reorganization is crucial to regulate their diverse immunological outcomes. Here we review current knowledge about the involvement of MLKL in mediating necroptosis and compare it with other lytic types of cell death.
Reaction of 1-bromobutane was investigated using Fenton reagent. This reagent is known to be a go... more Reaction of 1-bromobutane was investigated using Fenton reagent. This reagent is known to be a good oxidant for organic pollutants, which is composed of Fe2+ and H2O2. The reaction products that were identified were: 1-bromo-2-butanol, 1-butanoyl bromide, 1,3-dibromobutane, 1,4-dibromobutane, and 1,1,1-tribromobutane. This was verified by separating and analyzing the reaction mixture by GC/MS. Mechanisms were proposed for the formation of the products of the reaction of 1-bromobutane and Fenton reagent
Chicken meat consumption remains high in the Philippines, and consequently, annual chicken produc... more Chicken meat consumption remains high in the Philippines, and consequently, annual chicken production has risen steadily over the years. Although most of the chicken meat available in the market are sourced from factory farms, there has been growing popularity of free-range chicken production, largely driven by its perceived health benefits and sanitation concerns in factory farms, among others. In this work, we aimed at comparing the trace metal (copper, iron, lead, manganese, and zinc) content of free-range and factory-farmed broiler chicken meat that are being sold in Laguna, Philippines. The samples were subjected to acid digestion and analysis was done using atomic absorption spectrometry. Results showed an average concentration between 0.17 – 0.24 mg/kg, 2.22 – 2.34 mg/kg, 0.12 – 0.15 mg/kg, 0.95 – 1.32 mg/kg, and 1.81 – 1.96 mg/kg for copper, iron, lead, manganese, and zinc, respectively. Statistical analysis using one-way ANOVA and Tukey multiple comparison test (p < 0.05...
Scheme 6-1 Schematic diagram of TNM-A isolation from sponge. Scheme 6-2 Schematic diagram of AM3 ... more Scheme 6-1 Schematic diagram of TNM-A isolation from sponge. Scheme 6-2 Schematic diagram of AM3 isolation from harvested A. klebsii cells. Scheme 6-3 Two-state reaction model.
Marine organisms are a very good source of unique bioactive secondary metabolites, although they ... more Marine organisms are a very good source of unique bioactive secondary metabolites, although they have been comparatively underexplored relative to their terrestrial counterparts. Preliminary investigation of crude extracts from the fire coral Millepora dichotoma revealed that the hemolytic potential of the MeOH extract, at a concentration of 5 mg/mL, was significantly lower at less than 5% hemolysis while DCM extract at the same concentration resulted to almost 100% hemolysis. Furthermore, antimicrobial assay revealed that the MeOH extract (5 mg/mL) mildly inhibited the fungi T. mentagrophytes and resulted in the thinning of growth of S. aureus, while DCM extracts showed no detectable activity against these organisms. These results demonstrated that MeOH extracts of M. dichotoma, without showing hemolytic side effects, could be further analysed for potential use against T. mentagrophytes and S. aureus infections.
Chemical investigation of the dichloromethane extract of the fire coral, Millepora dichotoma yiel... more Chemical investigation of the dichloromethane extract of the fire coral, Millepora dichotoma yielded β-sitosterol (1), triacylglycerols (2), and wax esters (3). The structures of 1-3 were identified by comparison of their NMR data with literature data.
Cholesterol-dependent cytolysins (CDCs) are proteinaceous toxins secreted as monomers by some Gra... more Cholesterol-dependent cytolysins (CDCs) are proteinaceous toxins secreted as monomers by some Gram-positive and Gram-negative bacteria that contribute to their pathogenicity. These toxins bind to either cholesterol or human CD59, leading to massive structural changes, toxin oligomerization, formation of very large pores, and ultimately cell death, making these proteins promising targets for inhibition. Myricetin, and its related flavonoids, have been previously identified as a candidate small molecule inhibitor of specific CDCs such as listeriolysin O (LLO) and suilysin (SLY), interfering with their oligomerization. In this work, molecular docking was performed to assess the interaction of myricetin with other CDCs whose crystal structures are already known. Results indicated that although myricetin bound to the hitherto identified cavity in domain 4 (D4), much more efficient and stable binding was obtained in sites along the interfacial regions of domains 1 – 3 (D1 – D3). This was ...
Zeitschrift fur Naturforschung. C, Journal of biosciences, Jan 9, 2016
Amphidinol 3 (AM3) and theonellamide A (TNM-A) are potent antifungal compounds produced by the di... more Amphidinol 3 (AM3) and theonellamide A (TNM-A) are potent antifungal compounds produced by the dinoflagellate Amphidinium klebsii and the sponge Theonella spp., respectively. Both of these metabolites have been demonstrated to interact with membrane lipids ultimately resulting in a compromised bilayer integrity. In this report, the activity of AM3 and TNM-A in ternary lipid mixtures composed of 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine (POPC):brain sphingomyelin:cholesterol at a mole ratio of 1:1:1 or 3:1:1 exhibiting lipid rafts coexistence is presented. It was found that AM3 has a more extensive membrane permeabilizing activity compared with TNM-A in these membrane mimics, which was almost complete at 15 μM. The extent of their activity nevertheless is similar to the previously reported binary system of POPC and cholesterol, suggesting that phase separation has neither beneficial nor detrimental effects in their ability to disrupt the lipid bilayer.
Algal biofuels serve as a promising alternative energy source for liquid fuels. However, one of t... more Algal biofuels serve as a promising alternative energy source for liquid fuels. However, one of the bottlenecks in the conversion of microalgae to biofuels is the drying process. A moisture content of at most 10 % is desired for algal biomass prior to oil extraction to maximise biofuel yield. Conventional means of drying results to longer drying time and uneven drying of algal biomass. This study investigated the drying characteristics of microwave for microalgae (Chlorella vulgaris). Three microwave intensity levels (300, 600, and 900 W) were considered to dry 10, 20, and 30 of algal mass. Page model gave a better fit on the moisture ratio with time of microwave drying than the exponential model. Furthermore, the specific energy requirement was computed, and a relationship was found between moisture ratio with power and mass. Fourier transform infrared spectroscopy results showed significant reduction of infrared signal intensities of the functional groups present in the algae after drying at higher microwave power level. It was concluded that the 20 W/g microwave drying setting gave a lower specific energy requirement with good quality of remaining high lipid content qualitatively. Furthermore, it was recommended to use gas chromatography mass spectroscopy to further quantify the algal lipids and other functional groups.
SummaryFerroptosis is an iron-dependent form of regulated necrosis associated with lipid peroxida... more SummaryFerroptosis is an iron-dependent form of regulated necrosis associated with lipid peroxidation. Despite its key role in the inflammatory outcome of ferroptosis, little is known about the molecular events leading to the disruption of the plasma membrane during this type of cell death. Here we show that a sustained increase in cytosolic Ca2+ is a hallmark of ferroptosis that precedes complete bursting of the cell. We report that plasma membrane damage leading to ferroptosis is associated with membrane nanopores of few nanometers in radius and that ferroptosis, but not lipid peroxidation, can be delayed by osmoprotectants. Importantly, Ca2+ fluxes during ferroptosis correlate with the activation of ESCRT-III-mediated membrane repair, which counterbalances the kinetics of cell death and modulates the inflammatory signature of ferroptosis. Our findings with ferroptosis provide a unifying concept that sustained high levels of cytosolic Ca2+ prior to plasma membrane disruption are a...
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2019
Theonellamide a, a marine-sponge-derived bicyclic peptide, binds to cholesterol in aqueous DMSO: ... more Theonellamide a, a marine-sponge-derived bicyclic peptide, binds to cholesterol in aqueous DMSO: Solution NMR-based analysis of peptide-sterol interactions using hydroxylated sterol. Bbamem (2018),
Theonellamide A (TNM-A) is an antifungal bicyclic dodecapeptide isolated from a marine sponge The... more Theonellamide A (TNM-A) is an antifungal bicyclic dodecapeptide isolated from a marine sponge Theonella sp. Previous studies have shown that TNM-A preferentially binds to 3βhydroxysterol-containing membranes and disrupts membrane integrity. In this study, several 1 H NMR-based experiments were performed to investigate the interaction mode of TNM-A with model membranes. First, the aggregation propensities of TNM-A were examined using diffusion ordered spectroscopy; the results indicate that TNM-A tends to form oligomeric aggregates of 2-9 molecules (depending on peptide concentration) in an aqueous environment, and this aggregation potentially influences the membrane-disrupting activity of the peptide. Subsequently, we measured the 1 H NMR spectra of TNM-A with sodium dodecyl sulfate-d 25 (SDS-d 25) micelles and small dimyristoylphosphatidylcholine (DMPC)d 54 /dihexanoylphosphatidylcholine (DHPC)-d 22 bicelles in the presence of a paramagnetic quencher Mn 2+. These spectra indicate that TNM-A poorly binds to these membrane mimics without sterol and mostly remains in the aqueous media. In contrast, broader 1 H signals of TNM-A were observed in 10 mol% cholesterol-containing bicelles, indicating that the peptide efficiently binds to sterol-containing bilayers. The addition of Mn 2+ to these bicelles also led to a decrease in the relative intensity and further line-broadening of TNM-A signals, indicating that the peptide stays near the surface of the bilayers. A comparison of the relative signal intensities with those of phospholipids showed that TNM-A resides in the lipid-water interface (close to the C2 portion of the phospholipid acyl chain). This shallow penetration of TNM-A to lipid bilayers induces an uneven membrane curvature and eventually disrupts membrane integrity. These results shed light on the atomistic mechanism accounting for the membrane-disrupting activity of TNM-A and the important role of cholesterol in its mechanism of action. Sterol-Dependent Membrane Association of the Marine Sponge-Derived Bicyclic Peptide Theonellamide A as Examined by 1H NMR
Theonellamides (TNMs) are antifungal and cytotoxic bicyclic dodecapeptides derived from the marin... more Theonellamides (TNMs) are antifungal and cytotoxic bicyclic dodecapeptides derived from the marine sponge Theonella sp. These peptides specifically bind to 3β-hydroxysterols, resulting in 1,3-β-d-glucan overproduction and membrane damage in yeasts. The inclusion of cholesterol or ergosterol in phosphatidylcholine membranes significantly enhanced the membrane affinity of theonellamide A (TNM-A) because of its direct interaction with 3β-hydroxyl groups of sterols. To better understand TNM-induced membrane alterations, we investigated the effects of TNM-A on liposome morphology. (31)P nuclear magnetic resonance (NMR) and dynamic light scattering (DLS) measurements revealed that the premixing of TNM-A with lipids induced smaller vesicle formation. When giant unilamellar vesicles were incubated with exogenously added TNM-A, confocal micrographs showed dynamic changes in membrane morphology, which were more frequently observed in cholesterol-containing than sterol-free liposomes. In conju...
Amphidinol 3 (AM3), a polyhydroxy-polyene metabolite from the dinoflagellate Amphidinium klebsii,... more Amphidinol 3 (AM3), a polyhydroxy-polyene metabolite from the dinoflagellate Amphidinium klebsii, possesses potent antifungal activity. Although AM3 permeabilizes phospholipid membranes only in the presence of sterol, the detailed molecular basis by which AM3 recognizes sterols in membranes remains unknown. Here, we investigated the molecular interaction between sterols and AM3 in membranes from the viewpoint of stereospecific molecular recognition using ergosterol, cholesterol, and epicholesterol, which is the 3-OH epimer of cholesterol. Dye leakage assays, surface plasmon resonance experiments, 2 H and 31 P NMR measurements, and microscopic observations revealed that AM3 directly interacts with membrane sterols through the strict molecular recognition of the stereochemistry of the sterol 3-OH group. The direct interaction enhances the membrane binding efficiency of AM3, which subsequently permeabilizes membranes without altering membrane integrity.
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Papers by Rafael Espiritu