The Experts below are selected from a list of 90 Experts worldwide ranked by ideXlab platform
Klaus Brandenburg - One of the best experts on this subject based on the ideXlab platform.
-
Improvement of X-ray powder-diffraction patterns of Salmonella minnesota deep rough mutant bacterial lipopolysaccharide induced by heating plus hydration
Thin Solid Films, 1998Co-Authors: P.-j. Koch, Manfred Kastowsky, Hans Bradaczek, Klaus BrandenburgAbstract:Abstract The effects of different sample treatments on the X-ray powder-diffraction patterns of Salmonella minnesota R595 deep rough mutant bacterial lipopolysaccharides (LPS) were investigated. Samples were obtained by slow evaporation of aqueous solutions or suspensions of sodium, lithium and natural salt form lipids. Samples were treated by hydration in moist air, heating to 60°C and heating plus hydration. While after heating of samples no changes in diffraction patterns were observed, other treatments resulted in the improvement of peak intensities and sharpness of reflections. Heating plus hydration give the most significant effects. For one natural salt form LPS sample the treatments resulted in almost doubling of the number of observable reflections with the highest order found at 2 (∼) = 36°. It is discussed that the effects of treatments are most probably related to perfection of the lateral and the stacking order in the samples. rather than an improved mosaic spread. The simplicity of our sample treatments make them suitable for application to other than lipopolysaccharide samples, especially for samples prepared by the Langmuir-Blodgett method.
-
structural polymorphisms of rough mutant lipopolysaccharides rd to ra from Salmonella minnesota
Journal of Structural Biology, 1993Co-Authors: Ulrich Seydel, Michel H. J. Koch, Klaus BrandenburgAbstract:The structural polymorphisms of rough mutant lipopolysaccharides (LPS) Rd, Rc, Rb, and Ra from Salmonella minnesota (strains R4, R7, Rz, R5, R345, and R60, respectively) were investigated as a function of temperature, water content, and Mg2+ concentration. The gel to liquid crystalline (beta alpha) phase transition temperature (Tc) and the state of order within each phase were measured by Fourier transform infrared spectroscopy. The amount of bound water was determined by differential scanning calorimetry and the three-dimensional structures in each phase state were characterized by synchrotron radiation X-ray diffraction. The results indicate an extremely complex dependence of the structural behavior of LPS on ambient conditions. The beta alpha acyl chain melting temperatures at high water contents (95-97%), Tc = 31 to 32 degrees C for LPS Rd, 33 to 35 degrees C for LPS Rc to Rb, and 36 degrees C for LPS Ra, increase with decreasing water content and in the presence of Mg2+ cations with a concomitant broadening of the transition range. Below 30 to 50% water content, no distinct phase transitions can be observed. These effects are most pronounced for LPS with the shortest sugar chains. Below 50% water content, only lamellar structures can be observed in the temperature range 5 to 80 degrees C, independent of the Mg2+ concentration. Above 50% water concentration, for large [LPS]:[Mg2+] molar ratios the predominant structure above Tc is nonlamellar; for smaller [LPS]:[Mg2+] molar ratios a superposition of lamellar and nonlamellar structures is found. For all LPS Rd to Rb at low Mg2+ concentrations, the phase transition is connected with a change in the three-dimensional structure from lamellar or mixed lamellar/nonlamellar to a pure nonlamellar, probably cubic structure. The tendency to form non-lamellar structures decreases with the length of the core oligosaccharide. At an equimolar ratio of [LPS] and [Mg2+] a multibilayered organization is observed. Some of the nonlamellar structures are cubic phases with periodicities between 12 and 16 nm. The molecular dimensions of the single endotoxin molecules in the absence and the presence of external water are estimated from the different lamellar periodicities, including those of free lipid A and deep rough mutant LPS Re. These observations are discussed with respect to the biological importance of LPS as a potent inducer of biological effects in mammals.
-
Structural polymorphisms of rough mutant lipopolysaccharides Rd to Ra from Salmonella minnesota.
Journal of structural biology, 1993Co-Authors: Ulrich Seydel, Michel H. J. Koch, Klaus BrandenburgAbstract:The structural polymorphisms of rough mutant lipopolysaccharides (LPS) Rd, Rc, Rb, and Ra from Salmonella minnesota (strains R4, R7, Rz, R5, R345, and R60, respectively) were investigated as a function of temperature, water content, and Mg2+ concentration. The gel to liquid crystalline (B↔α) phase transition temperature (Tc) and the state of order within each phase were measured by Fourier transform infrared spectroscopy. The amount of bound water was determined by differential scanning calorimetry and the three-dimensional structures in each phase state were characterized by synchrotron radiation X-ray diffraction. The results indicate an extremely complex dependence of the structural behavior of LPS on ambient conditions. The B↔α acyl chain melting temperatures at high water contents (95-97%), Tc = 31 to 32°C for LPS Rd, 33 to 35°C for LPS Rc to Rb, and 36°C for LPS Ra, increase with decreasing water content and in the presence of Mg2+ cations with a concomitant broadening of the transition range. Below 30 to 50% water content, no distinct phase transitions can be observed. These effects are most pronounced for LPS with the shortest sugar chains. Below 50% water content, only lamellur structures can be observed in the temperature range 5 to 80°C, independent of the Mg2+ concentration. Above 50% water concentration, for large [LPS]:[Mg2+] molar ratios the predominant structure above Tc is nonlamellar; for smaller [LPS]:[Mg2+] molar ratios a superposition of lamellar and nonlamellar structures is found. For all LPS Rd to Rb at low Mg2+ concentrations, the phase transition is connected with a change in the three-dimensional structure from lamellar or mixed lamellar/nonlamellar to a pure nonlamellar, probably cubic structure. The tendency to form nonlamellar structures decreases with the length of the core oligosaccharide. At an equimolar ratio of [LPS] and [Mg2+] a multibilayered organization is observed. Some of the nonlamellar structures are cubic phases with periodicities between 12 and 16 nm. The molecular dimensions of the single endotoxin molecules in the absence and the presence of external water are estimated from the different lamellar periodicities, including those of free lipid A and deep rough mutant LPS Re. These observations are discussed with respect to the biological importance of LPS as a potent inducer of biological effects in mammals.
-
Phase diagram of deep rough mutant lipopolysaccharide from Salmonella minnesota R595.
Journal of structural biology, 1992Co-Authors: Klaus Brandenburg, Michel H. J. Koch, Ulrich SeydelAbstract:The structural polymorphism of deep rough mutant lipopolysaccharide--in many biological systems the most active endotoxin--from Salmonella minnesota strain R595 was investigated as function of temperature, water content, and Mg2+ concentration. Differential scanning calorimetry was used to determine the amount of bound water and the enthalpy change at the beta alpha gel to liquid crystalline acyl chain melting. The onset, midtemperature Tc, and completion of the beta alpha phase transition were studied with Fourier-transform infrared spectroscopy. Synchrotron radiation X-ray diffraction was used to characterize the supramolecular three-dimensional structures in each phase state. The results indicate an extremely complex dependence of the structural behavior of LPS on ambient conditions. The beta alpha acyl chain melting temperature Tc lying at 30 degrees C at high water content (95%) increases with decreasing water content reaching a value of 50 degrees C at 30% water content. Concomitantly, a broadening of the transition range takes place. At still lower water content, no distinct phase transition can be observed. This behavior is even more clearly expressed in the presence of Mg2+. In the lower water concentration range (< 50%) at temperatures below 70 degrees C, only lamellar structures can be observed independent of the Mg2+ concentration. This correlates with the absence of free water. Above 50% water concentration, the supramolecular structure below 70 degrees C strongly depends on the [LPS]:[Mg2+] ratio. For large [LPS]:[Mg2+] ratios, the predominant structure is nonlamellar, for smaller [LPS]:[Mg2+] ratios there is a superposition of lamellar and nonlamellar structures. At an equimolar ratio of LPS and Mg2+ a multibilayered organization is observed. The nonlamellar structures can be assigned in various cases to structures with cubic symmetry with periodicities between 12 and 16 nm. Under all investigated conditions, a transition into the hexagonal II structure takes place between 70 and 80 degrees C. These observations are discussed in relation to the biological importance of LPS as constituent of the outer membrane of gram-negative bacteria and as potent inducer of biological effects in mammals.
Béla Kocsis - One of the best experts on this subject based on the ideXlab platform.
-
non bilayer formation in the dppe dppg vesicle system induced by deep rough mutant of Salmonella minnesota r595 lipopolysaccharide
Colloids and Surfaces B: Biointerfaces, 2006Co-Authors: Edit Urbán, Attila Bóta, Béla KocsisAbstract:The vesicle system consisting of 80 mol% dipalmitoylphosphatidylethanolamine (DPPE) and 20 mol% dipalmitoylphosphatidylglycerol (DPPG) undergoes to structural changes caused by various concentrations of Salmonella minnesota R595 lipopolysaccharide (LPS). The phenomenon was investigated by methods applying small- and wide-angle X-ray scattering (SAXS and WAXS), calorimetry (DSC) and freeze-fracture. In the low LPS concentration regime (investigated at 0.02 LPS/DPPE-DPPG molar ratio) a phase separation was observed. Two kind of domains are formed which are rich and poor in DPPE and in these domains cubic and lamellar structures are present, respectively. Increasing the LPS concentration up to 0.1 LPS/DPPE-DPPG molar ratio the phase separation is more expressed and the temperature domains of the phase transitions are more different. Increasing the temperature chain melting of the lamellar phase occurs first and destruction of the cubic phase is observed later. At high LPS concentration (equimolar ratio of LPS/DPPE-DPPG), where this amphiphilic molecule cannot be considered any more a guest molecule, the cubic structure dominates the phase behaviour of the LPS molecules.
-
Non-bilayer formation in the DPPE–DPPG vesicle system induced by deep rough mutant of Salmonella minnesota R595 lipopolysaccharide
Colloids and surfaces. B Biointerfaces, 2006Co-Authors: Edit Urbán, Attila Bóta, Béla KocsisAbstract:The vesicle system consisting of 80 mol% dipalmitoylphosphatidylethanolamine (DPPE) and 20 mol% dipalmitoylphosphatidylglycerol (DPPG) undergoes to structural changes caused by various concentrations of Salmonella minnesota R595 lipopolysaccharide (LPS). The phenomenon was investigated by methods applying small- and wide-angle X-ray scattering (SAXS and WAXS), calorimetry (DSC) and freeze-fracture. In the low LPS concentration regime (investigated at 0.02 LPS/DPPE-DPPG molar ratio) a phase separation was observed. Two kind of domains are formed which are rich and poor in DPPE and in these domains cubic and lamellar structures are present, respectively. Increasing the LPS concentration up to 0.1 LPS/DPPE-DPPG molar ratio the phase separation is more expressed and the temperature domains of the phase transitions are more different. Increasing the temperature chain melting of the lamellar phase occurs first and destruction of the cubic phase is observed later. At high LPS concentration (equimolar ratio of LPS/DPPE-DPPG), where this amphiphilic molecule cannot be considered any more a guest molecule, the cubic structure dominates the phase behaviour of the LPS molecules.
-
Effect of Salmonella minnesota R595 LPS on the dipalmitoylphosphatidyl-ethanolamine (DPPE)–dipalmitoylglycerol (DPG)–water model membrane system
Chemistry and Physics of Lipids, 2006Co-Authors: Edit Urbán, Attila Bóta, Béla KocsisAbstract:The effect of Salmonella minnesota R595 lipopolysaccharide (LPS) on model membrane consisting of a mixture of fully hydrated lipids (dipalmitoylphosphatidylethanolamine (DPPE) and dipalmitoylglycerol (DPG)) was investigated by differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS) and freeze-fracture methods. The DPPE-DPG/water system forms a multilamellar arrangement in the gel phase which transforms into a mixture of inverted hexagonal and cubic structures. By the presence of LPS the thermotropic behaviour of the system was affected significantly only at its high concentration (1:1 mol/mol LPS/DPPE-DPG) in the gel phase, while above the chain melting transition the ratio of the inverted cubic and the hexagonal structures was changed and at the 1:1 mol/mol LPS/DPPE-DPG ratio a complex and amorphous phase was formed. The structural parameters of the inverted hexagonal and cubic phases are modified by the temperature and also by the LPS concentration, as deduced from the characteristic SAXS curves. Summarizing the effects of the LPS molecules on the DPPE-DPG/water vesicle system a schematic phase diagram was constructed.
Ulrich Seydel - One of the best experts on this subject based on the ideXlab platform.
-
structural polymorphisms of rough mutant lipopolysaccharides rd to ra from Salmonella minnesota
Journal of Structural Biology, 1993Co-Authors: Ulrich Seydel, Michel H. J. Koch, Klaus BrandenburgAbstract:The structural polymorphisms of rough mutant lipopolysaccharides (LPS) Rd, Rc, Rb, and Ra from Salmonella minnesota (strains R4, R7, Rz, R5, R345, and R60, respectively) were investigated as a function of temperature, water content, and Mg2+ concentration. The gel to liquid crystalline (beta alpha) phase transition temperature (Tc) and the state of order within each phase were measured by Fourier transform infrared spectroscopy. The amount of bound water was determined by differential scanning calorimetry and the three-dimensional structures in each phase state were characterized by synchrotron radiation X-ray diffraction. The results indicate an extremely complex dependence of the structural behavior of LPS on ambient conditions. The beta alpha acyl chain melting temperatures at high water contents (95-97%), Tc = 31 to 32 degrees C for LPS Rd, 33 to 35 degrees C for LPS Rc to Rb, and 36 degrees C for LPS Ra, increase with decreasing water content and in the presence of Mg2+ cations with a concomitant broadening of the transition range. Below 30 to 50% water content, no distinct phase transitions can be observed. These effects are most pronounced for LPS with the shortest sugar chains. Below 50% water content, only lamellar structures can be observed in the temperature range 5 to 80 degrees C, independent of the Mg2+ concentration. Above 50% water concentration, for large [LPS]:[Mg2+] molar ratios the predominant structure above Tc is nonlamellar; for smaller [LPS]:[Mg2+] molar ratios a superposition of lamellar and nonlamellar structures is found. For all LPS Rd to Rb at low Mg2+ concentrations, the phase transition is connected with a change in the three-dimensional structure from lamellar or mixed lamellar/nonlamellar to a pure nonlamellar, probably cubic structure. The tendency to form non-lamellar structures decreases with the length of the core oligosaccharide. At an equimolar ratio of [LPS] and [Mg2+] a multibilayered organization is observed. Some of the nonlamellar structures are cubic phases with periodicities between 12 and 16 nm. The molecular dimensions of the single endotoxin molecules in the absence and the presence of external water are estimated from the different lamellar periodicities, including those of free lipid A and deep rough mutant LPS Re. These observations are discussed with respect to the biological importance of LPS as a potent inducer of biological effects in mammals.
-
Structural polymorphisms of rough mutant lipopolysaccharides Rd to Ra from Salmonella minnesota.
Journal of structural biology, 1993Co-Authors: Ulrich Seydel, Michel H. J. Koch, Klaus BrandenburgAbstract:The structural polymorphisms of rough mutant lipopolysaccharides (LPS) Rd, Rc, Rb, and Ra from Salmonella minnesota (strains R4, R7, Rz, R5, R345, and R60, respectively) were investigated as a function of temperature, water content, and Mg2+ concentration. The gel to liquid crystalline (B↔α) phase transition temperature (Tc) and the state of order within each phase were measured by Fourier transform infrared spectroscopy. The amount of bound water was determined by differential scanning calorimetry and the three-dimensional structures in each phase state were characterized by synchrotron radiation X-ray diffraction. The results indicate an extremely complex dependence of the structural behavior of LPS on ambient conditions. The B↔α acyl chain melting temperatures at high water contents (95-97%), Tc = 31 to 32°C for LPS Rd, 33 to 35°C for LPS Rc to Rb, and 36°C for LPS Ra, increase with decreasing water content and in the presence of Mg2+ cations with a concomitant broadening of the transition range. Below 30 to 50% water content, no distinct phase transitions can be observed. These effects are most pronounced for LPS with the shortest sugar chains. Below 50% water content, only lamellur structures can be observed in the temperature range 5 to 80°C, independent of the Mg2+ concentration. Above 50% water concentration, for large [LPS]:[Mg2+] molar ratios the predominant structure above Tc is nonlamellar; for smaller [LPS]:[Mg2+] molar ratios a superposition of lamellar and nonlamellar structures is found. For all LPS Rd to Rb at low Mg2+ concentrations, the phase transition is connected with a change in the three-dimensional structure from lamellar or mixed lamellar/nonlamellar to a pure nonlamellar, probably cubic structure. The tendency to form nonlamellar structures decreases with the length of the core oligosaccharide. At an equimolar ratio of [LPS] and [Mg2+] a multibilayered organization is observed. Some of the nonlamellar structures are cubic phases with periodicities between 12 and 16 nm. The molecular dimensions of the single endotoxin molecules in the absence and the presence of external water are estimated from the different lamellar periodicities, including those of free lipid A and deep rough mutant LPS Re. These observations are discussed with respect to the biological importance of LPS as a potent inducer of biological effects in mammals.
-
Phase diagram of deep rough mutant lipopolysaccharide from Salmonella minnesota R595.
Journal of structural biology, 1992Co-Authors: Klaus Brandenburg, Michel H. J. Koch, Ulrich SeydelAbstract:The structural polymorphism of deep rough mutant lipopolysaccharide--in many biological systems the most active endotoxin--from Salmonella minnesota strain R595 was investigated as function of temperature, water content, and Mg2+ concentration. Differential scanning calorimetry was used to determine the amount of bound water and the enthalpy change at the beta alpha gel to liquid crystalline acyl chain melting. The onset, midtemperature Tc, and completion of the beta alpha phase transition were studied with Fourier-transform infrared spectroscopy. Synchrotron radiation X-ray diffraction was used to characterize the supramolecular three-dimensional structures in each phase state. The results indicate an extremely complex dependence of the structural behavior of LPS on ambient conditions. The beta alpha acyl chain melting temperature Tc lying at 30 degrees C at high water content (95%) increases with decreasing water content reaching a value of 50 degrees C at 30% water content. Concomitantly, a broadening of the transition range takes place. At still lower water content, no distinct phase transition can be observed. This behavior is even more clearly expressed in the presence of Mg2+. In the lower water concentration range (< 50%) at temperatures below 70 degrees C, only lamellar structures can be observed independent of the Mg2+ concentration. This correlates with the absence of free water. Above 50% water concentration, the supramolecular structure below 70 degrees C strongly depends on the [LPS]:[Mg2+] ratio. For large [LPS]:[Mg2+] ratios, the predominant structure is nonlamellar, for smaller [LPS]:[Mg2+] ratios there is a superposition of lamellar and nonlamellar structures. At an equimolar ratio of LPS and Mg2+ a multibilayered organization is observed. The nonlamellar structures can be assigned in various cases to structures with cubic symmetry with periodicities between 12 and 16 nm. Under all investigated conditions, a transition into the hexagonal II structure takes place between 70 and 80 degrees C. These observations are discussed in relation to the biological importance of LPS as constituent of the outer membrane of gram-negative bacteria and as potent inducer of biological effects in mammals.
Edit Urbán - One of the best experts on this subject based on the ideXlab platform.
-
non bilayer formation in the dppe dppg vesicle system induced by deep rough mutant of Salmonella minnesota r595 lipopolysaccharide
Colloids and Surfaces B: Biointerfaces, 2006Co-Authors: Edit Urbán, Attila Bóta, Béla KocsisAbstract:The vesicle system consisting of 80 mol% dipalmitoylphosphatidylethanolamine (DPPE) and 20 mol% dipalmitoylphosphatidylglycerol (DPPG) undergoes to structural changes caused by various concentrations of Salmonella minnesota R595 lipopolysaccharide (LPS). The phenomenon was investigated by methods applying small- and wide-angle X-ray scattering (SAXS and WAXS), calorimetry (DSC) and freeze-fracture. In the low LPS concentration regime (investigated at 0.02 LPS/DPPE-DPPG molar ratio) a phase separation was observed. Two kind of domains are formed which are rich and poor in DPPE and in these domains cubic and lamellar structures are present, respectively. Increasing the LPS concentration up to 0.1 LPS/DPPE-DPPG molar ratio the phase separation is more expressed and the temperature domains of the phase transitions are more different. Increasing the temperature chain melting of the lamellar phase occurs first and destruction of the cubic phase is observed later. At high LPS concentration (equimolar ratio of LPS/DPPE-DPPG), where this amphiphilic molecule cannot be considered any more a guest molecule, the cubic structure dominates the phase behaviour of the LPS molecules.
-
Non-bilayer formation in the DPPE–DPPG vesicle system induced by deep rough mutant of Salmonella minnesota R595 lipopolysaccharide
Colloids and surfaces. B Biointerfaces, 2006Co-Authors: Edit Urbán, Attila Bóta, Béla KocsisAbstract:The vesicle system consisting of 80 mol% dipalmitoylphosphatidylethanolamine (DPPE) and 20 mol% dipalmitoylphosphatidylglycerol (DPPG) undergoes to structural changes caused by various concentrations of Salmonella minnesota R595 lipopolysaccharide (LPS). The phenomenon was investigated by methods applying small- and wide-angle X-ray scattering (SAXS and WAXS), calorimetry (DSC) and freeze-fracture. In the low LPS concentration regime (investigated at 0.02 LPS/DPPE-DPPG molar ratio) a phase separation was observed. Two kind of domains are formed which are rich and poor in DPPE and in these domains cubic and lamellar structures are present, respectively. Increasing the LPS concentration up to 0.1 LPS/DPPE-DPPG molar ratio the phase separation is more expressed and the temperature domains of the phase transitions are more different. Increasing the temperature chain melting of the lamellar phase occurs first and destruction of the cubic phase is observed later. At high LPS concentration (equimolar ratio of LPS/DPPE-DPPG), where this amphiphilic molecule cannot be considered any more a guest molecule, the cubic structure dominates the phase behaviour of the LPS molecules.
-
Effect of Salmonella minnesota R595 LPS on the dipalmitoylphosphatidyl-ethanolamine (DPPE)–dipalmitoylglycerol (DPG)–water model membrane system
Chemistry and Physics of Lipids, 2006Co-Authors: Edit Urbán, Attila Bóta, Béla KocsisAbstract:The effect of Salmonella minnesota R595 lipopolysaccharide (LPS) on model membrane consisting of a mixture of fully hydrated lipids (dipalmitoylphosphatidylethanolamine (DPPE) and dipalmitoylglycerol (DPG)) was investigated by differential scanning calorimetry (DSC), small-angle X-ray scattering (SAXS) and freeze-fracture methods. The DPPE-DPG/water system forms a multilamellar arrangement in the gel phase which transforms into a mixture of inverted hexagonal and cubic structures. By the presence of LPS the thermotropic behaviour of the system was affected significantly only at its high concentration (1:1 mol/mol LPS/DPPE-DPG) in the gel phase, while above the chain melting transition the ratio of the inverted cubic and the hexagonal structures was changed and at the 1:1 mol/mol LPS/DPPE-DPG ratio a complex and amorphous phase was formed. The structural parameters of the inverted hexagonal and cubic phases are modified by the temperature and also by the LPS concentration, as deduced from the characteristic SAXS curves. Summarizing the effects of the LPS molecules on the DPPE-DPG/water vesicle system a schematic phase diagram was constructed.
-
Distortion of the lamellar arrangement of phospholipids by deep rough mutant lipopolysaccharide from Salmonella minnesota
Journal of Thermal Analysis and Calorimetry, 2005Co-Authors: Edit Urbán, B Kocsis, A. Bóta, K. LohnerAbstract:The concentration dependent effects of deep rough mutant lipopolysaccharide (LPS) from Salmonella minnesota (R595) on two different phospholipid model membranes was investigated by differential scanning calorimetry and small-angle X-ray scattering (SAXS). At low concentrations of LPS the well ordered multilamellar arrangement of dipalmitoylphosphatidylcholine (DPPC) vesicles is strongly distorted resulting in a loss of positional correlation of the lipid lamellae and smaller domain sizes within the lamellae. The pre-transition of DPPC was abolished at a LPS/DPPC molar ratio of 0.1:1 and the main or chain melting transition was strongly broadened. Moreover, the enthalpy was significantly decreased and a transition was hardly detected at an equimolar mixture of LPS/DPPC. LPS also affected the lamellar arrangement of a mixture of dipalmitoylphosphatidylethanolamine (DPPE) and dipalmitoylphosphatidylglycerol (DPPG). Furthermore, a phase separation was observed for this phospholipid mixture resulting in DPPE enriched and depleted domains. Similarly to DPPC, only a weak phase transition was observed at the highest LPS concentration used (LPS/DPPE-DPPG 1:1 mol/mol). SAXS measurements showed that for both systems increasing the concentration of LPS resulted in a concomitant increase of the formation of cubic structures, which are predominant at an equimolar mixture of LPS/phospholipid. However, because of the small number of peaks it was not possible to unambiguously identify the space group of the cubic structure, complicated by the coexistence with a lamellar phase, which was particularly detectable for the LPS/DPPC mixture.
Michel H. J. Koch - One of the best experts on this subject based on the ideXlab platform.
-
structural polymorphisms of rough mutant lipopolysaccharides rd to ra from Salmonella minnesota
Journal of Structural Biology, 1993Co-Authors: Ulrich Seydel, Michel H. J. Koch, Klaus BrandenburgAbstract:The structural polymorphisms of rough mutant lipopolysaccharides (LPS) Rd, Rc, Rb, and Ra from Salmonella minnesota (strains R4, R7, Rz, R5, R345, and R60, respectively) were investigated as a function of temperature, water content, and Mg2+ concentration. The gel to liquid crystalline (beta alpha) phase transition temperature (Tc) and the state of order within each phase were measured by Fourier transform infrared spectroscopy. The amount of bound water was determined by differential scanning calorimetry and the three-dimensional structures in each phase state were characterized by synchrotron radiation X-ray diffraction. The results indicate an extremely complex dependence of the structural behavior of LPS on ambient conditions. The beta alpha acyl chain melting temperatures at high water contents (95-97%), Tc = 31 to 32 degrees C for LPS Rd, 33 to 35 degrees C for LPS Rc to Rb, and 36 degrees C for LPS Ra, increase with decreasing water content and in the presence of Mg2+ cations with a concomitant broadening of the transition range. Below 30 to 50% water content, no distinct phase transitions can be observed. These effects are most pronounced for LPS with the shortest sugar chains. Below 50% water content, only lamellar structures can be observed in the temperature range 5 to 80 degrees C, independent of the Mg2+ concentration. Above 50% water concentration, for large [LPS]:[Mg2+] molar ratios the predominant structure above Tc is nonlamellar; for smaller [LPS]:[Mg2+] molar ratios a superposition of lamellar and nonlamellar structures is found. For all LPS Rd to Rb at low Mg2+ concentrations, the phase transition is connected with a change in the three-dimensional structure from lamellar or mixed lamellar/nonlamellar to a pure nonlamellar, probably cubic structure. The tendency to form non-lamellar structures decreases with the length of the core oligosaccharide. At an equimolar ratio of [LPS] and [Mg2+] a multibilayered organization is observed. Some of the nonlamellar structures are cubic phases with periodicities between 12 and 16 nm. The molecular dimensions of the single endotoxin molecules in the absence and the presence of external water are estimated from the different lamellar periodicities, including those of free lipid A and deep rough mutant LPS Re. These observations are discussed with respect to the biological importance of LPS as a potent inducer of biological effects in mammals.
-
Structural polymorphisms of rough mutant lipopolysaccharides Rd to Ra from Salmonella minnesota.
Journal of structural biology, 1993Co-Authors: Ulrich Seydel, Michel H. J. Koch, Klaus BrandenburgAbstract:The structural polymorphisms of rough mutant lipopolysaccharides (LPS) Rd, Rc, Rb, and Ra from Salmonella minnesota (strains R4, R7, Rz, R5, R345, and R60, respectively) were investigated as a function of temperature, water content, and Mg2+ concentration. The gel to liquid crystalline (B↔α) phase transition temperature (Tc) and the state of order within each phase were measured by Fourier transform infrared spectroscopy. The amount of bound water was determined by differential scanning calorimetry and the three-dimensional structures in each phase state were characterized by synchrotron radiation X-ray diffraction. The results indicate an extremely complex dependence of the structural behavior of LPS on ambient conditions. The B↔α acyl chain melting temperatures at high water contents (95-97%), Tc = 31 to 32°C for LPS Rd, 33 to 35°C for LPS Rc to Rb, and 36°C for LPS Ra, increase with decreasing water content and in the presence of Mg2+ cations with a concomitant broadening of the transition range. Below 30 to 50% water content, no distinct phase transitions can be observed. These effects are most pronounced for LPS with the shortest sugar chains. Below 50% water content, only lamellur structures can be observed in the temperature range 5 to 80°C, independent of the Mg2+ concentration. Above 50% water concentration, for large [LPS]:[Mg2+] molar ratios the predominant structure above Tc is nonlamellar; for smaller [LPS]:[Mg2+] molar ratios a superposition of lamellar and nonlamellar structures is found. For all LPS Rd to Rb at low Mg2+ concentrations, the phase transition is connected with a change in the three-dimensional structure from lamellar or mixed lamellar/nonlamellar to a pure nonlamellar, probably cubic structure. The tendency to form nonlamellar structures decreases with the length of the core oligosaccharide. At an equimolar ratio of [LPS] and [Mg2+] a multibilayered organization is observed. Some of the nonlamellar structures are cubic phases with periodicities between 12 and 16 nm. The molecular dimensions of the single endotoxin molecules in the absence and the presence of external water are estimated from the different lamellar periodicities, including those of free lipid A and deep rough mutant LPS Re. These observations are discussed with respect to the biological importance of LPS as a potent inducer of biological effects in mammals.
-
Phase diagram of deep rough mutant lipopolysaccharide from Salmonella minnesota R595.
Journal of structural biology, 1992Co-Authors: Klaus Brandenburg, Michel H. J. Koch, Ulrich SeydelAbstract:The structural polymorphism of deep rough mutant lipopolysaccharide--in many biological systems the most active endotoxin--from Salmonella minnesota strain R595 was investigated as function of temperature, water content, and Mg2+ concentration. Differential scanning calorimetry was used to determine the amount of bound water and the enthalpy change at the beta alpha gel to liquid crystalline acyl chain melting. The onset, midtemperature Tc, and completion of the beta alpha phase transition were studied with Fourier-transform infrared spectroscopy. Synchrotron radiation X-ray diffraction was used to characterize the supramolecular three-dimensional structures in each phase state. The results indicate an extremely complex dependence of the structural behavior of LPS on ambient conditions. The beta alpha acyl chain melting temperature Tc lying at 30 degrees C at high water content (95%) increases with decreasing water content reaching a value of 50 degrees C at 30% water content. Concomitantly, a broadening of the transition range takes place. At still lower water content, no distinct phase transition can be observed. This behavior is even more clearly expressed in the presence of Mg2+. In the lower water concentration range (< 50%) at temperatures below 70 degrees C, only lamellar structures can be observed independent of the Mg2+ concentration. This correlates with the absence of free water. Above 50% water concentration, the supramolecular structure below 70 degrees C strongly depends on the [LPS]:[Mg2+] ratio. For large [LPS]:[Mg2+] ratios, the predominant structure is nonlamellar, for smaller [LPS]:[Mg2+] ratios there is a superposition of lamellar and nonlamellar structures. At an equimolar ratio of LPS and Mg2+ a multibilayered organization is observed. The nonlamellar structures can be assigned in various cases to structures with cubic symmetry with periodicities between 12 and 16 nm. Under all investigated conditions, a transition into the hexagonal II structure takes place between 70 and 80 degrees C. These observations are discussed in relation to the biological importance of LPS as constituent of the outer membrane of gram-negative bacteria and as potent inducer of biological effects in mammals.
