The Experts below are selected from a list of 111 Experts worldwide ranked by ideXlab platform
Paolo Neyroz - One of the best experts on this subject based on the ideXlab platform.
-
2-Naphthol-phosphatidylethanolamine: A fluorescent Phospholipid analogue for excited-state proton transfer studies in membranes
Journal of Fluorescence, 1996Co-Authors: Paolo Neyroz, Lorella Franzoni, Alberto Spisni, Carolina Menna, Lanfranco MasottiAbstract:The fluorescence properties of the Phospholipid Derivative, N -[1-(2-naphthol)]-phosphatidylethanolamine (NAPH-PE), have been studied by steady-state and time-resolved fluorescence techniques. The new probe is a naphthol adduct of phosphatidylethanolamine. The emission spectrum of the fluorescent Phospholipid depends on the pH and on the proton acceptor concentration as expected for a typical two-state excited-state proton transfer reaction. In ethanol solutions at an apparent pH of 6.7 and in the presence of acetate anion (0.14 M) , a biexponential decay is obtained from global analysis of the data. The lifetimes, τ _1=3.9 ns and τ _2=6.2 ns. are constant across the spectral region 350–460 nm. The decay-associated spectra and the species-associated spectra reproduce well the profiles reported for a two-state excited-state proton transfer reaction. The fluorescent Phospholipid has been incorporated into dimyristoyllecithin and dipalmitoyllecithin vesicles. Although lower proton transfer is found, the reaction appears to be dependent on the gel-to-liquid-crystalline phase transition of the lipid membrane. In addition, the steady-state anisotropy of NAPH-PE measured as a function of temperature trace the phase transition of the two vesicle systems. Thus, it is shown that the physical state of the bilayer affects a reaction which takes place at the membrane surface. In the presence of acetate ions (0.3 M) , global analysis, performed in terms of fluorescence decay parameters, recovers preexponential coefficients that are consistent with an excited-state proton transfer reaction. The short lifetime drops from 3.9 to 0.44 ns without significant changes of the longer-lifetime component.
-
Preparation of lucifer yellow fluorescent liposomes: A method for cells' membrane labeling
Journal of Fluorescence, 1993Co-Authors: Carolina Menna, Lanfranco Masotti, Natalia Calonghi, Paolo NeyrozAbstract:This report describes a method to conjugate lucifer yellow to the external surface of liposomes. The heterobifunctional cross-linking reagent N -succinimidyl 3-(2-pyridyldithio)propionate has been used to activate DMPE molecules. The DMPE-dithiopyridine product has been mixed with DMPC to prepare liposome vesicles. These have been reduced by DTT and finally reacted with lucifer yellow-iodoacetamide to produce the fluorescence-labeled vesicles. The quenching of their fluorescence intensity by Kl is consistent with fully exposed fluorophores. The decay of the fluorescence intensity of the lipid-bound lucifer yellow is biexponential (τ_1=7.9 ns; τ_2=1.1 ns), with a relative yield of 0.16. When the fluorescent liposomes are mixed with cells, the lucifer yellow-DMPE Derivative is transferred. Boar spermatozoa and peripheral human blood lymphocytes have been used as cellular models. The extent of incorporation is dependent on the incubation time and temperature. At 36°C, lucifer yellow fluorescence appears in the spermatozoa cells after 10 min of incubation and reaches its maximum at about 60 min. The fluorescent Phospholipid Derivative seems to incorporate specifically into membrane structures. The highest labeling ratio is observed with integer, scarcely motile, spermatozoa. A poorer labeling yield (≈15%) is found with lymphocytes. Interestingly, photobleaching due to epiillumination of the labeled cells is apparently negligible and cells are clearly visible after irradiation times ranging from several minutes to few hours.
-
The chemical synthesis of N-[1-(2-naphthol)]-phosphatidylethanolamine, a fluorescent Phospholipid for excited-state proton transfer studies☆
Chemistry and Physics of Lipids, 1992Co-Authors: Paolo Neyroz, Lorella Franzoni, Alberto Spisni, Lanfranco Masotti, Ludwig BrandAbstract:Abstract A procedure for the preparation of N-[1-(2-naphthol)]-phosphatidylethanolamine (NAPH-PE) has been developed. The synthesis is based on the Schiff base formation between the NH2 of the Phospholipid and the aldehyde moiety of 2-hydroxy-1-napththaldehyde. Then selective reduction of the imine is used to obtain the stable secondary amine, NAPH-PE. Formation of the intermediate Schiff base and the final product is confirmed by 13C- and 1H-NMR. Similar to free 2-naphthol, the excited-state pKa ( p K a ∗ ) of its Phospholipid Derivative appears to be significantly lower than the ground-state pKa. At pH 7.4, the excitation spectrum of NAPH-PE shows no deprotonated species in the ground-state, while the emission spectrum presents a significant contribution of this species. Thus the fluorescent Phospholipid exhibits the typical behavior of excited-state proton-transfer probes. NAPH-PE is found to incorporate in dimyristoyllecithin (DML) vesicles. The emission spectrum of the probe inserted in the liposomes is affected by acetate used as a proton acceptor. These properties should also be manifest in other lipid bilayers (e.g., plasma membranes of cells) and used for excited-state proton transfer studies.
Lanfranco Masotti - One of the best experts on this subject based on the ideXlab platform.
-
2-Naphthol-phosphatidylethanolamine: A fluorescent Phospholipid analogue for excited-state proton transfer studies in membranes
Journal of Fluorescence, 1996Co-Authors: Paolo Neyroz, Lorella Franzoni, Alberto Spisni, Carolina Menna, Lanfranco MasottiAbstract:The fluorescence properties of the Phospholipid Derivative, N -[1-(2-naphthol)]-phosphatidylethanolamine (NAPH-PE), have been studied by steady-state and time-resolved fluorescence techniques. The new probe is a naphthol adduct of phosphatidylethanolamine. The emission spectrum of the fluorescent Phospholipid depends on the pH and on the proton acceptor concentration as expected for a typical two-state excited-state proton transfer reaction. In ethanol solutions at an apparent pH of 6.7 and in the presence of acetate anion (0.14 M) , a biexponential decay is obtained from global analysis of the data. The lifetimes, τ _1=3.9 ns and τ _2=6.2 ns. are constant across the spectral region 350–460 nm. The decay-associated spectra and the species-associated spectra reproduce well the profiles reported for a two-state excited-state proton transfer reaction. The fluorescent Phospholipid has been incorporated into dimyristoyllecithin and dipalmitoyllecithin vesicles. Although lower proton transfer is found, the reaction appears to be dependent on the gel-to-liquid-crystalline phase transition of the lipid membrane. In addition, the steady-state anisotropy of NAPH-PE measured as a function of temperature trace the phase transition of the two vesicle systems. Thus, it is shown that the physical state of the bilayer affects a reaction which takes place at the membrane surface. In the presence of acetate ions (0.3 M) , global analysis, performed in terms of fluorescence decay parameters, recovers preexponential coefficients that are consistent with an excited-state proton transfer reaction. The short lifetime drops from 3.9 to 0.44 ns without significant changes of the longer-lifetime component.
-
Preparation of lucifer yellow fluorescent liposomes: A method for cells' membrane labeling
Journal of Fluorescence, 1993Co-Authors: Carolina Menna, Lanfranco Masotti, Natalia Calonghi, Paolo NeyrozAbstract:This report describes a method to conjugate lucifer yellow to the external surface of liposomes. The heterobifunctional cross-linking reagent N -succinimidyl 3-(2-pyridyldithio)propionate has been used to activate DMPE molecules. The DMPE-dithiopyridine product has been mixed with DMPC to prepare liposome vesicles. These have been reduced by DTT and finally reacted with lucifer yellow-iodoacetamide to produce the fluorescence-labeled vesicles. The quenching of their fluorescence intensity by Kl is consistent with fully exposed fluorophores. The decay of the fluorescence intensity of the lipid-bound lucifer yellow is biexponential (τ_1=7.9 ns; τ_2=1.1 ns), with a relative yield of 0.16. When the fluorescent liposomes are mixed with cells, the lucifer yellow-DMPE Derivative is transferred. Boar spermatozoa and peripheral human blood lymphocytes have been used as cellular models. The extent of incorporation is dependent on the incubation time and temperature. At 36°C, lucifer yellow fluorescence appears in the spermatozoa cells after 10 min of incubation and reaches its maximum at about 60 min. The fluorescent Phospholipid Derivative seems to incorporate specifically into membrane structures. The highest labeling ratio is observed with integer, scarcely motile, spermatozoa. A poorer labeling yield (≈15%) is found with lymphocytes. Interestingly, photobleaching due to epiillumination of the labeled cells is apparently negligible and cells are clearly visible after irradiation times ranging from several minutes to few hours.
-
The chemical synthesis of N-[1-(2-naphthol)]-phosphatidylethanolamine, a fluorescent Phospholipid for excited-state proton transfer studies☆
Chemistry and Physics of Lipids, 1992Co-Authors: Paolo Neyroz, Lorella Franzoni, Alberto Spisni, Lanfranco Masotti, Ludwig BrandAbstract:Abstract A procedure for the preparation of N-[1-(2-naphthol)]-phosphatidylethanolamine (NAPH-PE) has been developed. The synthesis is based on the Schiff base formation between the NH2 of the Phospholipid and the aldehyde moiety of 2-hydroxy-1-napththaldehyde. Then selective reduction of the imine is used to obtain the stable secondary amine, NAPH-PE. Formation of the intermediate Schiff base and the final product is confirmed by 13C- and 1H-NMR. Similar to free 2-naphthol, the excited-state pKa ( p K a ∗ ) of its Phospholipid Derivative appears to be significantly lower than the ground-state pKa. At pH 7.4, the excitation spectrum of NAPH-PE shows no deprotonated species in the ground-state, while the emission spectrum presents a significant contribution of this species. Thus the fluorescent Phospholipid exhibits the typical behavior of excited-state proton-transfer probes. NAPH-PE is found to incorporate in dimyristoyllecithin (DML) vesicles. The emission spectrum of the probe inserted in the liposomes is affected by acetate used as a proton acceptor. These properties should also be manifest in other lipid bilayers (e.g., plasma membranes of cells) and used for excited-state proton transfer studies.
Michael James - One of the best experts on this subject based on the ideXlab platform.
-
Synthesis of deuterated [D32]oleic acid and its Phospholipid Derivative [D64]dioleoyl‐sn‐glycero‐3‐phosphocholine
Journal of Labelled Compounds and Radiopharmaceuticals, 2013Co-Authors: Tamim A Darwish, Emily Luks, Greta Moraes, Nageshwar R Yepuri, Peter J Holden, Michael JamesAbstract:Oleic acid and its Phospholipid Derivatives are fundamental to the structure and function of cellular membranes. As a result, there has been increasing interest in the availability of their deuterated forms for many nuclear magnetic resonance, infrared, mass spectroscopy and neutron scattering studies. Here, we present for the first time a straightforward, large-scale (gram quantities) synthesis of highly deuterated [D32]oleic acid by using multiple, yet simple and high yielding reactions. The precursors for the synthesis of [D32]oleic acid are [D14]azelaic acid and [D17]nonanoic acid, which were obtained by complete deuteration (>98% D) of their 1H forms by using metal catalysed hydrothermal H/D exchange reactions. The oleic acid was produced with ca. 94% D isotopic purity and with no contamination by the trans-isomer (elaidic acid). The subsequent synthesis of [D64]dioleoyl-sn-glycero-3-phosphocholine from [D32]oleic acid is also described. Copyright © 2013 John Wiley & Sons, Ltd.
-
synthesis of deuterated d32 oleic acid and its Phospholipid Derivative d64 dioleoyl sn glycero 3 phosphocholine
Journal of Labelled Compounds and Radiopharmaceuticals, 2013Co-Authors: Tamim A Darwish, Emily Luks, Greta Moraes, Nageshwar R Yepuri, Peter J Holden, Michael JamesAbstract:Oleic acid and its Phospholipid Derivatives are fundamental to the structure and function of cellular membranes. As a result, there has been increasing interest in the availability of their deuterated forms for many nuclear magnetic resonance, infrared, mass spectroscopy and neutron scattering studies. Here, we present for the first time a straightforward, large-scale (gram quantities) synthesis of highly deuterated [D32]oleic acid by using multiple, yet simple and high yielding reactions. The precursors for the synthesis of [D32]oleic acid are [D14]azelaic acid and [D17]nonanoic acid, which were obtained by complete deuteration (>98% D) of their 1H forms by using metal catalysed hydrothermal H/D exchange reactions. The oleic acid was produced with ca. 94% D isotopic purity and with no contamination by the trans-isomer (elaidic acid). The subsequent synthesis of [D64]dioleoyl-sn-glycero-3-phosphocholine from [D32]oleic acid is also described. Copyright © 2013 John Wiley & Sons, Ltd.
Carolina Menna - One of the best experts on this subject based on the ideXlab platform.
-
2-Naphthol-phosphatidylethanolamine: A fluorescent Phospholipid analogue for excited-state proton transfer studies in membranes
Journal of Fluorescence, 1996Co-Authors: Paolo Neyroz, Lorella Franzoni, Alberto Spisni, Carolina Menna, Lanfranco MasottiAbstract:The fluorescence properties of the Phospholipid Derivative, N -[1-(2-naphthol)]-phosphatidylethanolamine (NAPH-PE), have been studied by steady-state and time-resolved fluorescence techniques. The new probe is a naphthol adduct of phosphatidylethanolamine. The emission spectrum of the fluorescent Phospholipid depends on the pH and on the proton acceptor concentration as expected for a typical two-state excited-state proton transfer reaction. In ethanol solutions at an apparent pH of 6.7 and in the presence of acetate anion (0.14 M) , a biexponential decay is obtained from global analysis of the data. The lifetimes, τ _1=3.9 ns and τ _2=6.2 ns. are constant across the spectral region 350–460 nm. The decay-associated spectra and the species-associated spectra reproduce well the profiles reported for a two-state excited-state proton transfer reaction. The fluorescent Phospholipid has been incorporated into dimyristoyllecithin and dipalmitoyllecithin vesicles. Although lower proton transfer is found, the reaction appears to be dependent on the gel-to-liquid-crystalline phase transition of the lipid membrane. In addition, the steady-state anisotropy of NAPH-PE measured as a function of temperature trace the phase transition of the two vesicle systems. Thus, it is shown that the physical state of the bilayer affects a reaction which takes place at the membrane surface. In the presence of acetate ions (0.3 M) , global analysis, performed in terms of fluorescence decay parameters, recovers preexponential coefficients that are consistent with an excited-state proton transfer reaction. The short lifetime drops from 3.9 to 0.44 ns without significant changes of the longer-lifetime component.
-
Preparation of lucifer yellow fluorescent liposomes: A method for cells' membrane labeling
Journal of Fluorescence, 1993Co-Authors: Carolina Menna, Lanfranco Masotti, Natalia Calonghi, Paolo NeyrozAbstract:This report describes a method to conjugate lucifer yellow to the external surface of liposomes. The heterobifunctional cross-linking reagent N -succinimidyl 3-(2-pyridyldithio)propionate has been used to activate DMPE molecules. The DMPE-dithiopyridine product has been mixed with DMPC to prepare liposome vesicles. These have been reduced by DTT and finally reacted with lucifer yellow-iodoacetamide to produce the fluorescence-labeled vesicles. The quenching of their fluorescence intensity by Kl is consistent with fully exposed fluorophores. The decay of the fluorescence intensity of the lipid-bound lucifer yellow is biexponential (τ_1=7.9 ns; τ_2=1.1 ns), with a relative yield of 0.16. When the fluorescent liposomes are mixed with cells, the lucifer yellow-DMPE Derivative is transferred. Boar spermatozoa and peripheral human blood lymphocytes have been used as cellular models. The extent of incorporation is dependent on the incubation time and temperature. At 36°C, lucifer yellow fluorescence appears in the spermatozoa cells after 10 min of incubation and reaches its maximum at about 60 min. The fluorescent Phospholipid Derivative seems to incorporate specifically into membrane structures. The highest labeling ratio is observed with integer, scarcely motile, spermatozoa. A poorer labeling yield (≈15%) is found with lymphocytes. Interestingly, photobleaching due to epiillumination of the labeled cells is apparently negligible and cells are clearly visible after irradiation times ranging from several minutes to few hours.
Lorella Franzoni - One of the best experts on this subject based on the ideXlab platform.
-
2-Naphthol-phosphatidylethanolamine: A fluorescent Phospholipid analogue for excited-state proton transfer studies in membranes
Journal of Fluorescence, 1996Co-Authors: Paolo Neyroz, Lorella Franzoni, Alberto Spisni, Carolina Menna, Lanfranco MasottiAbstract:The fluorescence properties of the Phospholipid Derivative, N -[1-(2-naphthol)]-phosphatidylethanolamine (NAPH-PE), have been studied by steady-state and time-resolved fluorescence techniques. The new probe is a naphthol adduct of phosphatidylethanolamine. The emission spectrum of the fluorescent Phospholipid depends on the pH and on the proton acceptor concentration as expected for a typical two-state excited-state proton transfer reaction. In ethanol solutions at an apparent pH of 6.7 and in the presence of acetate anion (0.14 M) , a biexponential decay is obtained from global analysis of the data. The lifetimes, τ _1=3.9 ns and τ _2=6.2 ns. are constant across the spectral region 350–460 nm. The decay-associated spectra and the species-associated spectra reproduce well the profiles reported for a two-state excited-state proton transfer reaction. The fluorescent Phospholipid has been incorporated into dimyristoyllecithin and dipalmitoyllecithin vesicles. Although lower proton transfer is found, the reaction appears to be dependent on the gel-to-liquid-crystalline phase transition of the lipid membrane. In addition, the steady-state anisotropy of NAPH-PE measured as a function of temperature trace the phase transition of the two vesicle systems. Thus, it is shown that the physical state of the bilayer affects a reaction which takes place at the membrane surface. In the presence of acetate ions (0.3 M) , global analysis, performed in terms of fluorescence decay parameters, recovers preexponential coefficients that are consistent with an excited-state proton transfer reaction. The short lifetime drops from 3.9 to 0.44 ns without significant changes of the longer-lifetime component.
-
The chemical synthesis of N-[1-(2-naphthol)]-phosphatidylethanolamine, a fluorescent Phospholipid for excited-state proton transfer studies☆
Chemistry and Physics of Lipids, 1992Co-Authors: Paolo Neyroz, Lorella Franzoni, Alberto Spisni, Lanfranco Masotti, Ludwig BrandAbstract:Abstract A procedure for the preparation of N-[1-(2-naphthol)]-phosphatidylethanolamine (NAPH-PE) has been developed. The synthesis is based on the Schiff base formation between the NH2 of the Phospholipid and the aldehyde moiety of 2-hydroxy-1-napththaldehyde. Then selective reduction of the imine is used to obtain the stable secondary amine, NAPH-PE. Formation of the intermediate Schiff base and the final product is confirmed by 13C- and 1H-NMR. Similar to free 2-naphthol, the excited-state pKa ( p K a ∗ ) of its Phospholipid Derivative appears to be significantly lower than the ground-state pKa. At pH 7.4, the excitation spectrum of NAPH-PE shows no deprotonated species in the ground-state, while the emission spectrum presents a significant contribution of this species. Thus the fluorescent Phospholipid exhibits the typical behavior of excited-state proton-transfer probes. NAPH-PE is found to incorporate in dimyristoyllecithin (DML) vesicles. The emission spectrum of the probe inserted in the liposomes is affected by acetate used as a proton acceptor. These properties should also be manifest in other lipid bilayers (e.g., plasma membranes of cells) and used for excited-state proton transfer studies.