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Alicja Wizert - One of the best experts on this subject based on the ideXlab platform.
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Lysozyme in the Tear Film Lipid Layer
Biophysical Journal, 2016Co-Authors: Lukasz Cwiklik, D. Robert Iskander, Agnieszka Olżyńska, Alicja WizertAbstract:The ocular surface of the human eye is covered and protected by the tear film, an aqueous multilayered structure. The very outer interface between the tear film and air is coated by the tear film Lipid layer (TFLL), a relatively thin Lipid-rich region. Its main function is reduction of the surface tension of the tear film-air interface. It was also postulated that the presence of the TFLL prevents rapid evaporation of water from the underlying water aqueous phase. TFLL deficiencies lead to evaporative dry eye syndrome, one of the commonly reported eye ailments.The aqueous phase of the tear film comprises several classes of proteins. Among them, lysozyme is the most abundant. Its primary biological function in the tear film is anti-microbial activity against pathogens. It was also suggested that lysozyme plays a role in maintaining stability of the tear film. Namely, it was experimentally demonstrated that tear proteins, including lysozyme, lower surface tension of tears hence increasing the film durability. It was also observed that lysozyme concentration in tears is diminished in patients with dry eye.Employing our recent computational model of the TFLL which is able to capture key molecular-level characteristics of the tear Lipid film, we employed coarse grain MD simulations focused on interactions of lysozyme with TFLL. Accumulation of the protein at the water-Lipid interface was observed. Moreover, simulations indicate that lateral compression-decompression cycles of the film, similar to those due to blinking, may lead to penetration of lysozyme into the TFLL and its subsequent accumulation in the Non-Polar Lipid phase. We tested this hypothesis experimentally for model TFLL layers employing Langmuir balance measurements coupled with fluorescence microscopy.
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molecular level organization of the tear film Lipid layer a molecular dynamics simulation study
Biophysical Journal, 2014Co-Authors: Alicja Wizert, Robert D Iskander, Pavel Jungwirth, Lukasz CwiklikAbstract:Tear film is essential to the health and optics of the human eye. It refreshes with every blink and ruptures if blinking is suppressed. Its instabilities lead to the dry eye syndrome. The outermost layer of the tear film consists of Lipids which provide an optically smooth surface over the cornea and retard water evaporation. The tear film Lipid layer formation and structure are still debated. We employ coarse grain molecular dynamics simulations to study molecular-level structure and dynamics of the tear film Lipid layer. A novel, realistic tear film model under conditions mimicking those experienced by the tear film under physiological conditions was built and employed.Simulations show that polar phosphoLipids separate their Non-Polar counterparts from the water phase, constituting a monomolecular uniform platform at which a thick Non-Polar Lipid layer is formed. This Lipid arrangement is stable upon lateral compression. A significant restructuring of the film occurs upon non-equilibrium lateral compression which mimics eye blinks. The water/Lipid interface undulates, and Lipids are sorted based on their head group size. Undulations of the water/Lipid boundary are followed by transfer of some of polar Lipids and water toward the Non-Polar phase, resulting in formation of inverse micelles in the Non-Polar Lipid layer with water encapsulated by polar Lipids. Moreover, some of Non-Polar Lipids are transferred into the water phase in vesicles formed by polar Lipids.We predict that the tear film Lipid layer at the molecular level is a dynamic and non-uniform assembly with Lipids and water forming numerous three-dimensional structures in the vicinity of the Lipid/water interface. These structures form and reorganize due to the action of eye lids during blinks. They may serve as Lipid reservoirs and thus effectively increase stability of the tear film.
Lukasz Cwiklik - One of the best experts on this subject based on the ideXlab platform.
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Lysozyme in the Tear Film Lipid Layer
Biophysical Journal, 2016Co-Authors: Lukasz Cwiklik, D. Robert Iskander, Agnieszka Olżyńska, Alicja WizertAbstract:The ocular surface of the human eye is covered and protected by the tear film, an aqueous multilayered structure. The very outer interface between the tear film and air is coated by the tear film Lipid layer (TFLL), a relatively thin Lipid-rich region. Its main function is reduction of the surface tension of the tear film-air interface. It was also postulated that the presence of the TFLL prevents rapid evaporation of water from the underlying water aqueous phase. TFLL deficiencies lead to evaporative dry eye syndrome, one of the commonly reported eye ailments.The aqueous phase of the tear film comprises several classes of proteins. Among them, lysozyme is the most abundant. Its primary biological function in the tear film is anti-microbial activity against pathogens. It was also suggested that lysozyme plays a role in maintaining stability of the tear film. Namely, it was experimentally demonstrated that tear proteins, including lysozyme, lower surface tension of tears hence increasing the film durability. It was also observed that lysozyme concentration in tears is diminished in patients with dry eye.Employing our recent computational model of the TFLL which is able to capture key molecular-level characteristics of the tear Lipid film, we employed coarse grain MD simulations focused on interactions of lysozyme with TFLL. Accumulation of the protein at the water-Lipid interface was observed. Moreover, simulations indicate that lateral compression-decompression cycles of the film, similar to those due to blinking, may lead to penetration of lysozyme into the TFLL and its subsequent accumulation in the Non-Polar Lipid phase. We tested this hypothesis experimentally for model TFLL layers employing Langmuir balance measurements coupled with fluorescence microscopy.
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molecular level organization of the tear film Lipid layer a molecular dynamics simulation study
Biophysical Journal, 2014Co-Authors: Alicja Wizert, Robert D Iskander, Pavel Jungwirth, Lukasz CwiklikAbstract:Tear film is essential to the health and optics of the human eye. It refreshes with every blink and ruptures if blinking is suppressed. Its instabilities lead to the dry eye syndrome. The outermost layer of the tear film consists of Lipids which provide an optically smooth surface over the cornea and retard water evaporation. The tear film Lipid layer formation and structure are still debated. We employ coarse grain molecular dynamics simulations to study molecular-level structure and dynamics of the tear film Lipid layer. A novel, realistic tear film model under conditions mimicking those experienced by the tear film under physiological conditions was built and employed.Simulations show that polar phosphoLipids separate their Non-Polar counterparts from the water phase, constituting a monomolecular uniform platform at which a thick Non-Polar Lipid layer is formed. This Lipid arrangement is stable upon lateral compression. A significant restructuring of the film occurs upon non-equilibrium lateral compression which mimics eye blinks. The water/Lipid interface undulates, and Lipids are sorted based on their head group size. Undulations of the water/Lipid boundary are followed by transfer of some of polar Lipids and water toward the Non-Polar phase, resulting in formation of inverse micelles in the Non-Polar Lipid layer with water encapsulated by polar Lipids. Moreover, some of Non-Polar Lipids are transferred into the water phase in vesicles formed by polar Lipids.We predict that the tear film Lipid layer at the molecular level is a dynamic and non-uniform assembly with Lipids and water forming numerous three-dimensional structures in the vicinity of the Lipid/water interface. These structures form and reorganize due to the action of eye lids during blinks. They may serve as Lipid reservoirs and thus effectively increase stability of the tear film.
Xueli Cao - One of the best experts on this subject based on the ideXlab platform.
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a biphasic system based on guanidinium ionic liquid preparative separation of eicosapentaenoic acid ethyl ester and docosahexaenoic acid ethyl ester by countercurrent chromatography
Journal of Chromatography A, 2020Co-Authors: Chen Fan, Lijiao Wen, Xueli CaoAbstract:Abstract Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are high nutritional components. Evidence for unique effects of them is increasing. Further understanding of their independent biological functions urgently needs more efficient separation techniques. Nowadays, most of the commercially available fish oil products are the mixture of eicosapentaenoic acid ethyl ester (EPAEE) and docosahexaenoic acid ethyl ester (DHAEE). It will be convenient to directly separate esterified EPA and DHA without saponification pretreatment. However, it is of great challenge to separate EPAEE and DHAEE because of their extremely fat-soluble nature and the equivalent chain length rule. In this research, the suitability of green guanidinium ionic liquid (IL) in countercurrent chromatography (CCC) solvent system for the separation of them was evaluated for the first time. Compared with imidazolium IL and phosphonium IL, guanidinium IL based non-aqueous biphasic system showed more outstanding separation performance. The separation mechanism was elucidated in depth through quantum mechanical calculations. It was found that guanidinium IL acted a crucial role in the CCC separation, which resulted in difference of partition behavior of EPAEE and DHAEE via different hydrogen-bonding affinity. EPAEE and DHAEE were successfully separated by solvent system (n-heptane/methanol/propylguanidinium chloride ([C3Gun]Cl, 1:1:5%, v/v/m)) with high purity (>95%) in one step, which was not achieved beforehand. Moreover, an easy recycling procedure of IL had also been devised, which significantly reduced waste generated. It opens up a new way for reasonable design water-free two-phase solvent system for efficient separation of very Non-Polar Lipid compounds.
D. Robert Iskander - One of the best experts on this subject based on the ideXlab platform.
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Lysozyme in the Tear Film Lipid Layer
Biophysical Journal, 2016Co-Authors: Lukasz Cwiklik, D. Robert Iskander, Agnieszka Olżyńska, Alicja WizertAbstract:The ocular surface of the human eye is covered and protected by the tear film, an aqueous multilayered structure. The very outer interface between the tear film and air is coated by the tear film Lipid layer (TFLL), a relatively thin Lipid-rich region. Its main function is reduction of the surface tension of the tear film-air interface. It was also postulated that the presence of the TFLL prevents rapid evaporation of water from the underlying water aqueous phase. TFLL deficiencies lead to evaporative dry eye syndrome, one of the commonly reported eye ailments.The aqueous phase of the tear film comprises several classes of proteins. Among them, lysozyme is the most abundant. Its primary biological function in the tear film is anti-microbial activity against pathogens. It was also suggested that lysozyme plays a role in maintaining stability of the tear film. Namely, it was experimentally demonstrated that tear proteins, including lysozyme, lower surface tension of tears hence increasing the film durability. It was also observed that lysozyme concentration in tears is diminished in patients with dry eye.Employing our recent computational model of the TFLL which is able to capture key molecular-level characteristics of the tear Lipid film, we employed coarse grain MD simulations focused on interactions of lysozyme with TFLL. Accumulation of the protein at the water-Lipid interface was observed. Moreover, simulations indicate that lateral compression-decompression cycles of the film, similar to those due to blinking, may lead to penetration of lysozyme into the TFLL and its subsequent accumulation in the Non-Polar Lipid phase. We tested this hypothesis experimentally for model TFLL layers employing Langmuir balance measurements coupled with fluorescence microscopy.
Agnieszka Olżyńska - One of the best experts on this subject based on the ideXlab platform.
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Lysozyme in the Tear Film Lipid Layer
Biophysical Journal, 2016Co-Authors: Lukasz Cwiklik, D. Robert Iskander, Agnieszka Olżyńska, Alicja WizertAbstract:The ocular surface of the human eye is covered and protected by the tear film, an aqueous multilayered structure. The very outer interface between the tear film and air is coated by the tear film Lipid layer (TFLL), a relatively thin Lipid-rich region. Its main function is reduction of the surface tension of the tear film-air interface. It was also postulated that the presence of the TFLL prevents rapid evaporation of water from the underlying water aqueous phase. TFLL deficiencies lead to evaporative dry eye syndrome, one of the commonly reported eye ailments.The aqueous phase of the tear film comprises several classes of proteins. Among them, lysozyme is the most abundant. Its primary biological function in the tear film is anti-microbial activity against pathogens. It was also suggested that lysozyme plays a role in maintaining stability of the tear film. Namely, it was experimentally demonstrated that tear proteins, including lysozyme, lower surface tension of tears hence increasing the film durability. It was also observed that lysozyme concentration in tears is diminished in patients with dry eye.Employing our recent computational model of the TFLL which is able to capture key molecular-level characteristics of the tear Lipid film, we employed coarse grain MD simulations focused on interactions of lysozyme with TFLL. Accumulation of the protein at the water-Lipid interface was observed. Moreover, simulations indicate that lateral compression-decompression cycles of the film, similar to those due to blinking, may lead to penetration of lysozyme into the TFLL and its subsequent accumulation in the Non-Polar Lipid phase. We tested this hypothesis experimentally for model TFLL layers employing Langmuir balance measurements coupled with fluorescence microscopy.