Metal-organic frameworks (MOFs) are crystalline porous materials with designable topology, porosi... more Metal-organic frameworks (MOFs) are crystalline porous materials with designable topology, porosity and functionality, having promising applications in gas storage and separation, ion conduction and catalysis. It is challenging to observe MOFs with transmission electron microscopy (TEM) due to the extreme instability of MOFs upon electron beam irradiation. Here, we use a direct-detection electron-counting camera to acquire TEM images of the MOF ZIF-8 with an ultralow dose of 4.1 electrons per square ångström to retain the structural integrity. The obtained image involves structural information transferred up to 2.1 Å, allowing the resolution of individual atomic columns of Zn and organic linkers in the framework. Furthermore, TEM reveals important local structural features of ZIF-8 crystals that cannot be identified by diffraction techniques, including armchair-type surface terminations and coherent interfaces between assembled crystals. These observations allow us to understand how...
Aquaporins (AQPs) are proteins that facilitate the transport of water across cell membranes. AQP3... more Aquaporins (AQPs) are proteins that facilitate the transport of water across cell membranes. AQP3 expression is related to the expressions of other epidermal proteins involved in water maintenance (ie, CD44, claudin-1, and filaggrin). The expressions of AQP3 water channels are strongly affected by age and chronic sun exposure, and a defective osmotic equilibrium could occur in the epidermis, which would account for the skin dryness observed in older people and skin areas most exposed to sunlight. We investigated active ingredients that are able to increase AQP3 levels in order to improve hydration in human skin keratinocytes. We selected an ethanolic/water (70/30 v/v) extract of Ajuga turkestanica, a plant from Central Asia, as the hydrating agent. After 17 days of treatment every 2 days with this extract (2.5 microg/mL) in vitro, AQP3 expression measured at the protein level in human reconstructed epidermis was significantly increased. Water transport through both aquaporins and aquaglyceroporins and glycerol transport through aquaglyceroporins alone are important to skin hydration. The distribution and the variability of aquaporins in human skin cells suggest that these channels may have important roles in skin physiology. AQPs appear to be key protein targets to improve the resistance and quality of the skin surface as well as to improve aging and sun exposure-induced dryness as shown by their roles in 1) hydrating the living layers of the epidermis where the keratinocyte differentiation takes place and 2) barrier formation and recovery.
Aquaporins (AQPs) are proteins that facilitate the transport of water across cell membranes. AQP3... more Aquaporins (AQPs) are proteins that facilitate the transport of water across cell membranes. AQP3 expression is related to the expressions of other epidermal proteins involved in water maintenance (ie, CD44, claudin-1, and filaggrin). The expressions of AQP3 water channels are strongly affected by age and chronic sun exposure, and a defective osmotic equilibrium could occur in the epidermis, which would account for the skin dryness observed in older people and skin areas most exposed to sunlight. We investigated active ingredients that are able to increase AQP3 levels in order to improve hydration in human skin keratinocytes. We selected an ethanolic/water (70/30 v/v) extract of Ajuga turkestanica, a plant from Central Asia, as the hydrating agent. After 17 days of treatment every 2 days with this extract (2.5 microg/mL) in vitro, AQP3 expression measured at the protein level in human reconstructed epidermis was significantly increased. Water transport through both aquaporins and aq...
The purpose of this study was to examine the presence of aquaporin water channels in human skin a... more The purpose of this study was to examine the presence of aquaporin water channels in human skin and to assess their functional role. On western blots of human epidermis obtained from plastic surgery, a strong signal was obtained with polyclonal anti-aquaporin-3 antibodies. By indirect immuno¯uorescence on 5 mm cryosections, anti-aquaporin-3 antibodies strongly stained keratinocyte plasma membranes in human epidermis, whereas no staining was observed in the dermis or the stratum corneum or when antiaquaporin-3 antibodies were preabsorbed with the peptide used for immunization. Similarly, a strong signal with anti-aquaporin-3 antibodies was observed in keratinocyte plasma membranes of reconstructed human epidermis in culture at the air±liquid interface for up to 3 wk. The keratinocyte plasma membrane localization of aquaporin-3 was con®rmed at the electron microscope level in prickle cells. In addition an intracellular localization of aquaporin-3 was also detected in epidermis basal cells. Osmotically induced transepidermal water permeability was measured on stripped human skin and on reconstructed epidermis. Water transport across both stripped human skin and 2±3 wk reconstructed epidermis was comparable, inhibited by > 50% by 1 mM HgCl 2 and fully inhibited by acid pH. By stoppedow light scattering, keratinocyte plasma membranes, where aquaporin-3 is localized, exhibited a high, pH-sensitive, water permeability. Although human skin is highly impermeable to water, this is primarily accounted for by the stratum corneum, where a steep water content gradient was demonstrated. In contrast, the water content of viable strata of the epidermis is remarkably constant. Our results suggest that the human epidermis, below the stratum corneum, exhibits a high, aquaporin-3-mediated, water permeability. We propose that the role of aquaporin-3 is to water-clamp viable layers of the epidermis in order to improve the hydration of the epidermis below the stratum corneum. Key words: aquaporin water channels/human keratinocytes/water permeability. J Invest Dermatol 118: 678±685, 2002
Recent instrumental developments have enabled greatly improved resolution of scanning transmissio... more Recent instrumental developments have enabled greatly improved resolution of scanning transmission electron microscopes (STEM) through aberration correction. An additional and previously unanticipated advantage of aberration correction is the greatly improved depth sensitivity that has led to the reconstruction of a three-dimensional (3D) image from a focal series. In this chapter the potential of aberration-corrected 3D STEM to provide major improvements
Silver nanoparticles were deposited on the surface and pore walls of block copolymer membranes wi... more Silver nanoparticles were deposited on the surface and pore walls of block copolymer membranes with highly ordered pore structure. Pyridine blocks constitute the pore surfaces, complexing silver ions and promoting a homogeneous distribution. Nanoparticles were then formed by reduction with sodium borohydride. The morphology varied with the preparation conditions (pH and silver ion concentration), as confirmed by field emission scanning and transmission electron microscopy. Silver has a strong biocide activity, which for membranes can bring the advantage of minimizing the growth of bacteria and formation of biofilm. The membranes with nanoparticles prepared under different pH values and ion concentrations were incubated with Pseudomonas aeruginosa and compared with the control. The strongest biocidal activity was achieved with membranes containing membranes prepared under pH 9. Under these conditions, the best distribution with small particle size was observed by microscopy.
During intraerythrocytic development, the human malaria parasite, Plasmodium falciparum, establis... more During intraerythrocytic development, the human malaria parasite, Plasmodium falciparum, establishes membrane-bound compartments, known as Maurer's clefts, outside the confines of its own plasma membrane. The Maurer's compartments are thought to be a crucial component of the machinery for protein sorting and trafficking; however, their ultrastructure is only partly defined. We have used electron tomography to image Maurer's clefts of 3D7 strain parasites. The compartments are revealed as flattened structures with a translucent lumen and a more electron-dense coat. They display a complex and convoluted morphology, and some regions are modified with surface nodules, each with a circular cross-section of~25 nm. Individual 25 nm vesicle-like structures are also seen in the erythrocyte cytoplasm and associated with the red blood cell membrane. The Maurer's clefts are connected to the red blood cell membrane by regions with extended stalk-like profiles. Immunogold labelling with specific antibodies confirms differential labelling of the Maurer's clefts and the parasitophorous vacuole and erythrocyte membranes. Spot fluorescence photobleaching was used to demonstrate the absence of a lipid continuum between the Maurer's clefts and parasite membranes and the host plasma membrane.
Granules in anammox reactors contain besides anammox bacteria other microbial communities whose i... more Granules in anammox reactors contain besides anammox bacteria other microbial communities whose identity and relationship with the anammox bacteria are not well understood. High calcium concentrations are often supplied to anammox reactors to obtain sufficient bacterial aggregation and biomass retention. The aim of this study was to provide the first characterization of bacterial and archaeal communities in anammox granules from a full-scale anammox reactor and to explore on the possible role of calcium in such aggregates. High magnification imaging using backscattered electrons revealed that anammox bacteria may be embedded in calcium phosphate precipitates. Pyrosequencing of 16S rRNA gene fragments showed, besides anammox bacteria (Brocadiacea, 32 %), substantial numbers of heterotrophic bacteria Ignavibacteriacea (18 %) and Anaerolinea (7 %) along with heterotrophic denitrifiers Rhodocyclacea (9 %), Comamonadacea (3 %), and Shewanellacea (3 %) in the granules. It is hypothesized that these bacteria may form a network in which heterotrophic denitrifiers cooperate to achieve a well-functioning denitrification system as they can utilize the nitrate intrinsically produced by the anammox reaction. This network may provide a niche for the proliferation of archaea. Hydrogenotrophic methananogens, which scavenge the key fermentation product H2, were the most abundant archaea detected. Cells resembling the polygon-shaped denitrifying methanotroph Candidatus Methylomirabilis oxyfera were observed by electron microscopy. It is hypothesized that the anammox process in a full-scale reactor triggers various reactions overall leading to efficient denitrification and a sink of carbon as biomass in anammox granules.
Metal-organic frameworks (MOFs) are crystalline porous materials with designable topology, porosi... more Metal-organic frameworks (MOFs) are crystalline porous materials with designable topology, porosity and functionality, having promising applications in gas storage and separation, ion conduction and catalysis. It is challenging to observe MOFs with transmission electron microscopy (TEM) due to the extreme instability of MOFs upon electron beam irradiation. Here, we use a direct-detection electron-counting camera to acquire TEM images of the MOF ZIF-8 with an ultralow dose of 4.1 electrons per square ångström to retain the structural integrity. The obtained image involves structural information transferred up to 2.1 Å, allowing the resolution of individual atomic columns of Zn and organic linkers in the framework. Furthermore, TEM reveals important local structural features of ZIF-8 crystals that cannot be identified by diffraction techniques, including armchair-type surface terminations and coherent interfaces between assembled crystals. These observations allow us to understand how...
Aquaporins (AQPs) are proteins that facilitate the transport of water across cell membranes. AQP3... more Aquaporins (AQPs) are proteins that facilitate the transport of water across cell membranes. AQP3 expression is related to the expressions of other epidermal proteins involved in water maintenance (ie, CD44, claudin-1, and filaggrin). The expressions of AQP3 water channels are strongly affected by age and chronic sun exposure, and a defective osmotic equilibrium could occur in the epidermis, which would account for the skin dryness observed in older people and skin areas most exposed to sunlight. We investigated active ingredients that are able to increase AQP3 levels in order to improve hydration in human skin keratinocytes. We selected an ethanolic/water (70/30 v/v) extract of Ajuga turkestanica, a plant from Central Asia, as the hydrating agent. After 17 days of treatment every 2 days with this extract (2.5 microg/mL) in vitro, AQP3 expression measured at the protein level in human reconstructed epidermis was significantly increased. Water transport through both aquaporins and aquaglyceroporins and glycerol transport through aquaglyceroporins alone are important to skin hydration. The distribution and the variability of aquaporins in human skin cells suggest that these channels may have important roles in skin physiology. AQPs appear to be key protein targets to improve the resistance and quality of the skin surface as well as to improve aging and sun exposure-induced dryness as shown by their roles in 1) hydrating the living layers of the epidermis where the keratinocyte differentiation takes place and 2) barrier formation and recovery.
Aquaporins (AQPs) are proteins that facilitate the transport of water across cell membranes. AQP3... more Aquaporins (AQPs) are proteins that facilitate the transport of water across cell membranes. AQP3 expression is related to the expressions of other epidermal proteins involved in water maintenance (ie, CD44, claudin-1, and filaggrin). The expressions of AQP3 water channels are strongly affected by age and chronic sun exposure, and a defective osmotic equilibrium could occur in the epidermis, which would account for the skin dryness observed in older people and skin areas most exposed to sunlight. We investigated active ingredients that are able to increase AQP3 levels in order to improve hydration in human skin keratinocytes. We selected an ethanolic/water (70/30 v/v) extract of Ajuga turkestanica, a plant from Central Asia, as the hydrating agent. After 17 days of treatment every 2 days with this extract (2.5 microg/mL) in vitro, AQP3 expression measured at the protein level in human reconstructed epidermis was significantly increased. Water transport through both aquaporins and aq...
The purpose of this study was to examine the presence of aquaporin water channels in human skin a... more The purpose of this study was to examine the presence of aquaporin water channels in human skin and to assess their functional role. On western blots of human epidermis obtained from plastic surgery, a strong signal was obtained with polyclonal anti-aquaporin-3 antibodies. By indirect immuno¯uorescence on 5 mm cryosections, anti-aquaporin-3 antibodies strongly stained keratinocyte plasma membranes in human epidermis, whereas no staining was observed in the dermis or the stratum corneum or when antiaquaporin-3 antibodies were preabsorbed with the peptide used for immunization. Similarly, a strong signal with anti-aquaporin-3 antibodies was observed in keratinocyte plasma membranes of reconstructed human epidermis in culture at the air±liquid interface for up to 3 wk. The keratinocyte plasma membrane localization of aquaporin-3 was con®rmed at the electron microscope level in prickle cells. In addition an intracellular localization of aquaporin-3 was also detected in epidermis basal cells. Osmotically induced transepidermal water permeability was measured on stripped human skin and on reconstructed epidermis. Water transport across both stripped human skin and 2±3 wk reconstructed epidermis was comparable, inhibited by > 50% by 1 mM HgCl 2 and fully inhibited by acid pH. By stoppedow light scattering, keratinocyte plasma membranes, where aquaporin-3 is localized, exhibited a high, pH-sensitive, water permeability. Although human skin is highly impermeable to water, this is primarily accounted for by the stratum corneum, where a steep water content gradient was demonstrated. In contrast, the water content of viable strata of the epidermis is remarkably constant. Our results suggest that the human epidermis, below the stratum corneum, exhibits a high, aquaporin-3-mediated, water permeability. We propose that the role of aquaporin-3 is to water-clamp viable layers of the epidermis in order to improve the hydration of the epidermis below the stratum corneum. Key words: aquaporin water channels/human keratinocytes/water permeability. J Invest Dermatol 118: 678±685, 2002
Recent instrumental developments have enabled greatly improved resolution of scanning transmissio... more Recent instrumental developments have enabled greatly improved resolution of scanning transmission electron microscopes (STEM) through aberration correction. An additional and previously unanticipated advantage of aberration correction is the greatly improved depth sensitivity that has led to the reconstruction of a three-dimensional (3D) image from a focal series. In this chapter the potential of aberration-corrected 3D STEM to provide major improvements
Silver nanoparticles were deposited on the surface and pore walls of block copolymer membranes wi... more Silver nanoparticles were deposited on the surface and pore walls of block copolymer membranes with highly ordered pore structure. Pyridine blocks constitute the pore surfaces, complexing silver ions and promoting a homogeneous distribution. Nanoparticles were then formed by reduction with sodium borohydride. The morphology varied with the preparation conditions (pH and silver ion concentration), as confirmed by field emission scanning and transmission electron microscopy. Silver has a strong biocide activity, which for membranes can bring the advantage of minimizing the growth of bacteria and formation of biofilm. The membranes with nanoparticles prepared under different pH values and ion concentrations were incubated with Pseudomonas aeruginosa and compared with the control. The strongest biocidal activity was achieved with membranes containing membranes prepared under pH 9. Under these conditions, the best distribution with small particle size was observed by microscopy.
During intraerythrocytic development, the human malaria parasite, Plasmodium falciparum, establis... more During intraerythrocytic development, the human malaria parasite, Plasmodium falciparum, establishes membrane-bound compartments, known as Maurer's clefts, outside the confines of its own plasma membrane. The Maurer's compartments are thought to be a crucial component of the machinery for protein sorting and trafficking; however, their ultrastructure is only partly defined. We have used electron tomography to image Maurer's clefts of 3D7 strain parasites. The compartments are revealed as flattened structures with a translucent lumen and a more electron-dense coat. They display a complex and convoluted morphology, and some regions are modified with surface nodules, each with a circular cross-section of~25 nm. Individual 25 nm vesicle-like structures are also seen in the erythrocyte cytoplasm and associated with the red blood cell membrane. The Maurer's clefts are connected to the red blood cell membrane by regions with extended stalk-like profiles. Immunogold labelling with specific antibodies confirms differential labelling of the Maurer's clefts and the parasitophorous vacuole and erythrocyte membranes. Spot fluorescence photobleaching was used to demonstrate the absence of a lipid continuum between the Maurer's clefts and parasite membranes and the host plasma membrane.
Granules in anammox reactors contain besides anammox bacteria other microbial communities whose i... more Granules in anammox reactors contain besides anammox bacteria other microbial communities whose identity and relationship with the anammox bacteria are not well understood. High calcium concentrations are often supplied to anammox reactors to obtain sufficient bacterial aggregation and biomass retention. The aim of this study was to provide the first characterization of bacterial and archaeal communities in anammox granules from a full-scale anammox reactor and to explore on the possible role of calcium in such aggregates. High magnification imaging using backscattered electrons revealed that anammox bacteria may be embedded in calcium phosphate precipitates. Pyrosequencing of 16S rRNA gene fragments showed, besides anammox bacteria (Brocadiacea, 32 %), substantial numbers of heterotrophic bacteria Ignavibacteriacea (18 %) and Anaerolinea (7 %) along with heterotrophic denitrifiers Rhodocyclacea (9 %), Comamonadacea (3 %), and Shewanellacea (3 %) in the granules. It is hypothesized that these bacteria may form a network in which heterotrophic denitrifiers cooperate to achieve a well-functioning denitrification system as they can utilize the nitrate intrinsically produced by the anammox reaction. This network may provide a niche for the proliferation of archaea. Hydrogenotrophic methananogens, which scavenge the key fermentation product H2, were the most abundant archaea detected. Cells resembling the polygon-shaped denitrifying methanotroph Candidatus Methylomirabilis oxyfera were observed by electron microscopy. It is hypothesized that the anammox process in a full-scale reactor triggers various reactions overall leading to efficient denitrification and a sink of carbon as biomass in anammox granules.
Uploads
Papers by Rachid Sougrat