Peter Walde - Academia.edu (original) (raw)

Papers by Peter Walde

Research paper thumbnail of Oparin's Reactions Revisited: Enzymic Synthesis of Poly(adenylic acid) in Micelles and Self-Reproducing Vesicles

J Am Chem Soc, 1994

Poly( adenylic acid) in Micelles and Self-Reproducing Vesicles ... Peter Walde,? Ayako Goto,* Pie... more Poly( adenylic acid) in Micelles and Self-Reproducing Vesicles ... Peter Walde,? Ayako Goto,* Pierre-Alain Monnard,+ Michaela Wessicken,t and Pier Luigi Luisist ... Contribution from the Institut fur Polymere, ETH-Zentrum, CH-8092 Zurich, Switzerland, and Laboratory of ...

Research paper thumbnail of Self-replicating reverse micelles and chemical autopoiesis

Journal of the American Chemical Society, 1990

Table of Contents. Research Article. Self-replicating reverse micelles and chemical autopoiesis. ... more Table of Contents. Research Article. Self-replicating reverse micelles and chemical autopoiesis. First Page; PDF Hi-Res PDF[271 KB]. Pascale ...

Research paper thumbnail of Modeling of enzymatic reactions in vesicles: The case of ?-chymotrypsin

Biotechnol Bioeng, 1999

The kinetic behavior of the alpha-chymotrypsin-catalyzed hydrolysis of the two p-nitroanilide sub... more The kinetic behavior of the alpha-chymotrypsin-catalyzed hydrolysis of the two p-nitroanilide substrates succinyl-L-Ala-L-Ala-L-Pro-L-Phe-p-nitroanilide (Suc-Ala-Ala-Pro-Phe-pNA) and benzoyl-L-Tyr-p-nitroanilide (Bz-Tyr-pNA) was modeled and simulated for two different systems, namely for an aqueous solution and for a vesicle system, which was composed of phospholipid vesicles containing entrapped alpha-chymotrypsin. In the case of the vesicles, the substrate was added to the bulk, exovesicular aqueous phase. The experimentally determined time-dependence of product (p-nitroaniline) formation was modeled by considering the kinetic behavior of the enzyme and-in the case of vesicles-the substrate permeability across the bilayer membrane. In aqueous solution-without vesicles-the kinetic constants kcat and KS (respectively KM) were determined from fitting the model to experimental data of batch product concentration-time curves. The results were in good agreement with the corresponding values obtained from initial velocity measurements. For the vesicle system, using the phospholipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), simulation showed that the substrate permeation across the bilayer was rate limiting. Using experimental data, we could obtain the substrate permeability coefficient for Bz-Tyr-pNA by parametric fitting as 2. 45 x 10(-7) cm/s.

Research paper thumbnail of pH-Sensitive Vesicles Containing a Lipidic�-Amino Acid with Two Hydrophobic Chains

Chem Biodivers, 2008

The lipidic beta-amino acid 2-(aminomethyl)-2-pentadecylheptadecanoic acid (1) was synthesized vi... more The lipidic beta-amino acid 2-(aminomethyl)-2-pentadecylheptadecanoic acid (1) was synthesized via the alkylation of the C(alpha)-atom of fully protected beta-alanine. Mixed large unilamellar vesicles with a diameter between 100 and 200 nm containing POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) and 1 at a molar ratio of 9 : 1 were prepared and found to have a surface charge which is dependent on pH. At slightly acidic pH, the vesicles were positively charged, and at alkaline pH negatively charged. Dynamic light scattering, zeta potential, and cryo-transmission electron-microscopy measurements indicated that the mixed vesicles fused at pH 4-5 with negatively charged mixed vesicles composed of POPC and POPG (9.8 : 1, molar ratio), POPG being 1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)].

Research paper thumbnail of Enzymatic Polymerization in Presence of Vesicles as Templates

Chimia International Journal For Chemistry, Nov 27, 2009

Research paper thumbnail of Modeling of enzymatic reactions in vesicles: The case of a-chymotrypsin

Biotechnol Bioeng, 1999

The kinetic behavior of the alpha-chymotrypsin-catalyzed hydrolysis of the two p-nitroanilide sub... more The kinetic behavior of the alpha-chymotrypsin-catalyzed hydrolysis of the two p-nitroanilide substrates succinyl-L-Ala-L-Ala-L-Pro-L-Phe-p-nitroanilide (Suc-Ala-Ala-Pro-Phe-pNA) and benzoyl-L-Tyr-p-nitroanilide (Bz-Tyr-pNA) was modeled and simulated for two different systems, namely for an aqueous solution and for a vesicle system, which was composed of phospholipid vesicles containing entrapped alpha-chymotrypsin. In the case of the vesicles, the substrate was added to the bulk, exovesicular aqueous phase. The experimentally determined time-dependence of product (p-nitroaniline) formation was modeled by considering the kinetic behavior of the enzyme and-in the case of vesicles-the substrate permeability across the bilayer membrane. In aqueous solution-without vesicles-the kinetic constants kcat and KS (respectively KM) were determined from fitting the model to experimental data of batch product concentration-time curves. The results were in good agreement with the corresponding values obtained from initial velocity measurements. For the vesicle system, using the phospholipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), simulation showed that the substrate permeation across the bilayer was rate limiting. Using experimental data, we could obtain the substrate permeability coefficient for Bz-Tyr-pNA by parametric fitting as 2. 45 x 10(-7) cm/s.

Research paper thumbnail of Self-replicating micelles: aqueous micelles and enzymatically driven reactions in reverse micelles

J Am Chem Soc, 1991

... I-Pyrenesulfonic acid sodium salt (PSA) was from Mo-lecular Probes; pyrene, methylviologen ch... more ... I-Pyrenesulfonic acid sodium salt (PSA) was from Mo-lecular Probes; pyrene, methylviologen chloride (MV), and l -octanol from Aldrich; and K,Fe(CN), from Merck. ... (6) Lang, J.; Jada, A ... Micelle concentration ([MI) as determined by fluorescence quenching; uncertainty &8%. ...

Research paper thumbnail of Interaction of α-and β-Oligoarginine-Acids and Amides with Anionic Lipid Vesicles: A Mechanistic and Thermodynamic Study †

Biochemistry Usa, 2006

ABSTRACT

Research paper thumbnail of Autopoietic Self-Reproduction of Fatty Acid Vesicles

J Am Chem Soc, 1994

Conditions are described under which vesicles formed by caprylic acid and oleic acid in water are... more Conditions are described under which vesicles formed by caprylic acid and oleic acid in water are able to undergo autopoietic self-reproduction-namely an increase of their population number due to a reaction which takes place within the spherical boundary of the vesicles themselves. This is achieved by letting a certain amount of the neat water-insoluble caprylic or oleic anhydride hydrolyze at alkaline pH: the initial increase of the concentration of the released acidcarboxylate is extremely slow (several days to reach the conditions for spontaneous vesicle formation), but afterwards, the presence of vesicles brings about a rapid second phase leading to more and more vesicles being formed in an overall autocatalytic process. The catalytic power of the caprylic acid and oleic acid vesicles toward the hydrolysis of the corresponding anhydride is documented in a set of independent experiments. In these experiments, the hydrolysis was carried out in the presence of vesicles at a pH corresponding approximately to the pK of the acid in the vesicles. The process of autopoietic self-reproduction of caprylic acid and oleic acid vesicles is studied as a function of temperature: by increasing temperature (up to 70 "C), the exponential time progress of vesicle formation tends to become steeper while the long initial slow phase is significantly shortened. The caprylic acid and oleic acid vesicles are characterized by electron microscopy and by determining their internal volume. The question whether and to what extent these vesicles form a classic chemical equilibrium system-in which namely the free surfactant is in equilibrium with the aggregates-is also investigated.

Research paper thumbnail of Self-Reproduction of Micelles and Liposomes and the Transition to Life

J Liposome Res, 1993

ABSTRACT

Research paper thumbnail of Stable and Simple Immobilization of Proteinase K Inside Glass Tubes and Microfluidic Channels

ACS applied materials & interfaces, Jan 4, 2015

Engyodontium album proteinase K (proK) is widely used for degrading proteinaceous impurities duri... more Engyodontium album proteinase K (proK) is widely used for degrading proteinaceous impurities during the isolation of nucleic acid from biological samples, or in proteomics and prion research. Towards applications of proK in flow reactors, a simple method for the stable immobilization of proK inside glass micropipette tubes was developed. The immobilization of the enzyme was achieved by adsorption of a dendronized polymer-enzyme conjugate from aqueous solution. This conjugate was first synthesized from a polycationic dendronized polymer (denpol) and proK and consisted, on average, of 2000 denpol repeating units and 140 proK molecules, which were attached along the denpol chain via stable bis-aryl hydrazone bonds. Although the immobilization of proK inside the tube was based on non-specific, non-covalent interactions only, the immobilized proK did not leak from the tube and remained active during prolonged storage at 4 °C and during continuous operation at 25 °C and pH = 7.0. The proc...

Research paper thumbnail of Dynamic Aspects of Fatty Acid Vesicles: pH‐Induced Vesicle‐Micelle Transition and Dilution‐Induced Formation of Giant Vesicles

Research paper thumbnail of Enzymatic Reactions in Giant Vesicles

Perspectives in Supramolecular Chemistry, 1999

Research paper thumbnail of ChemInform Abstract: Achievements and Challenges in Generating Protocell Models

Research paper thumbnail of ChemInform Abstract: Liposomes Containing Purine and Pyrimidine Bases: Stable Unilamellar Liposomes from Phosphatidyl Nucleosides

ChemInform, 1994

ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Research paper thumbnail of Efficient Polymerization of the Aniline Dimer p -Aminodiphenylamine (PADPA) with Trametes versicolor Laccase/O 2 as Catalyst and Oxidant and AOT Vesicles as Templates

ACS Catalysis, 2014

ABSTRACT The aniline dimer PADPA (= p-aminodiphenylamine = N-phenyl-1,4-phenylenediamine) was pol... more ABSTRACT The aniline dimer PADPA (= p-aminodiphenylamine = N-phenyl-1,4-phenylenediamine) was polymerized to poly(PADPA) at 25 °C with Trametes versicolor laccase (TvL)/O2 as catalyst and oxidant and in the presence of vesicles formed from sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as templates. In comparison to the previously studied polymerization of aniline with the same type of enzyme-vesicle system, the polymerization of PADPA is much faster, and considerably fewer enzymes are required for complete monomer conversion. Turbidity measurements indicate that PADPA strongly binds to the vesicle surface before oxidation and polymerization are initiated. Such binding is confirmed by molecular dynamics (MD) simulations, supporting the assumption that the reactions which lead to poly(PADPA) are localized on the vesicle surface. The poly(PADPA) obtained resembles the emeraldine salt form of polyaniline (PANI-ES) in its polaron state with a high content of unpaired electrons, as judged from UV/vis/NIR, EPR, and FTIR absorption measurements. There are, however, also notable spectroscopic differences between PANI-ES and the enzymatically prepared poly(PADPA). Poly(PADPA) appears to be similar to a chemically synthesized poly(PADPA) as obtained in a previous work with ammonium peroxydisulfate (APS) as the oxidant in a mixture of 50 vol % ethanol and 50 vol % 0.2 M sulfuric acid (J. Phys. Chem. B 2008, 112, 6976-6987). ESI-MS measurements of early intermediates of the reaction with TvL and AOT vesicles indicate that the presence of the vesicles decreases the extent of formation of unwanted oxygen-containing species in comparison to the reaction in the absence of vesicles. This is the first information about the differences in the chemical composition of early reaction intermediates when the reaction carried out in the presence of vesicles under optimal conditions is compared with a template-free system.

Research paper thumbnail of Liposomes Containing Purine and Pyrimidine Bases: Stable Unilamellar Liposomes from Phosphatidyl Nucleosides

The Journal of Physical Chemistry, 1994

ABSTRACT

Research paper thumbnail of Emergent properties arising from the assembly of amphiphiles. Artificial vesicle membranes as reaction promoters and regulators

Chemical communications (Cambridge, England), Jan 14, 2014

This article deals with artificial vesicles and their membranes as reaction promoters and regulat... more This article deals with artificial vesicles and their membranes as reaction promoters and regulators. Among the various molecular assemblies which can form in an aqueous medium from amphiphilic molecules, vesicle systems are unique. Vesicles compartmentalize the aqueous solution in which they exist, independent on whether the vesicles are biological vesicles (existing in living systems) or whether they are artificial vesicles (formed in vitro from natural or synthetic amphiphiles). After the formation of artificial vesicles, their aqueous interior (the endovesicular volume) may become - or may be made - chemically different from the external medium (the exovesicular solution), depending on how the vesicles are prepared. The existence of differences between endo- and exovesicular composition is one of the features on the basis of which biological vesicles contribute to the complex functioning of living organisms. Furthermore, artificial vesicles can be formed from mixtures of amphiph...

Research paper thumbnail of From self-assembled vesicles to protocells

Cold Spring Harbor perspectives in biology, 2010

Self-assembled vesicles are essential components of primitive cells. We review the importance of ... more Self-assembled vesicles are essential components of primitive cells. We review the importance of vesicles during the origins of life, fundamental thermodynamics and kinetics of self-assembly, and experimental models of simple vesicles, focusing on prebiotically plausible fatty acids and their derivatives. We review recent work on interactions of simple vesicles with RNA and other studies of the transition from vesicles to protocells. Finally we discuss current challenges in understanding the biophysics of protocells, as well as conceptual questions in information transmission and self-replication.

Research paper thumbnail of In vitro and in vivo anti-tumor effects of novel Span 80 vesicles containing immobilized Eucheuma serra agglutinin

International journal of pharmaceutics, Jan 15, 2010

The lectin Eucheuma serra agglutinin (ESA) is known from previous studies to specifically bind to... more The lectin Eucheuma serra agglutinin (ESA) is known from previous studies to specifically bind to high-mannose type N-glycans and to induce apoptotic cancer cell death in vitro. In this study, Span 80 vesicles, with an average diameter between about 200 and 400 nm, containing immobilized ESA were prepared from the nonionic surfactant Span 80, also known as sorbitan monooleate. The vesicles were investigated in vitro and in vivo to evaluate the vesicles's potential applicability as novel drug delivery system. The results obtained are promising since the following was observed: (i) vesicular ESA had the same hemagglutinating activity as free ESA, demonstrating its biological activity when bound to the vesicles; (ii) vesicles containing immobilized ESA decreased the viability of Colo201 cancer cells in vitro while the growth of normal cells was not affected; (iii) the vesicles showed binding to Colo201 cells in vitro and caused inhibition of cancer cell growth in nude mice to which...

Research paper thumbnail of Oparin's Reactions Revisited: Enzymic Synthesis of Poly(adenylic acid) in Micelles and Self-Reproducing Vesicles

J Am Chem Soc, 1994

Poly( adenylic acid) in Micelles and Self-Reproducing Vesicles ... Peter Walde,? Ayako Goto,* Pie... more Poly( adenylic acid) in Micelles and Self-Reproducing Vesicles ... Peter Walde,? Ayako Goto,* Pierre-Alain Monnard,+ Michaela Wessicken,t and Pier Luigi Luisist ... Contribution from the Institut fur Polymere, ETH-Zentrum, CH-8092 Zurich, Switzerland, and Laboratory of ...

Research paper thumbnail of Self-replicating reverse micelles and chemical autopoiesis

Journal of the American Chemical Society, 1990

Table of Contents. Research Article. Self-replicating reverse micelles and chemical autopoiesis. ... more Table of Contents. Research Article. Self-replicating reverse micelles and chemical autopoiesis. First Page; PDF Hi-Res PDF[271 KB]. Pascale ...

Research paper thumbnail of Modeling of enzymatic reactions in vesicles: The case of ?-chymotrypsin

Biotechnol Bioeng, 1999

The kinetic behavior of the alpha-chymotrypsin-catalyzed hydrolysis of the two p-nitroanilide sub... more The kinetic behavior of the alpha-chymotrypsin-catalyzed hydrolysis of the two p-nitroanilide substrates succinyl-L-Ala-L-Ala-L-Pro-L-Phe-p-nitroanilide (Suc-Ala-Ala-Pro-Phe-pNA) and benzoyl-L-Tyr-p-nitroanilide (Bz-Tyr-pNA) was modeled and simulated for two different systems, namely for an aqueous solution and for a vesicle system, which was composed of phospholipid vesicles containing entrapped alpha-chymotrypsin. In the case of the vesicles, the substrate was added to the bulk, exovesicular aqueous phase. The experimentally determined time-dependence of product (p-nitroaniline) formation was modeled by considering the kinetic behavior of the enzyme and-in the case of vesicles-the substrate permeability across the bilayer membrane. In aqueous solution-without vesicles-the kinetic constants kcat and KS (respectively KM) were determined from fitting the model to experimental data of batch product concentration-time curves. The results were in good agreement with the corresponding values obtained from initial velocity measurements. For the vesicle system, using the phospholipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), simulation showed that the substrate permeation across the bilayer was rate limiting. Using experimental data, we could obtain the substrate permeability coefficient for Bz-Tyr-pNA by parametric fitting as 2. 45 x 10(-7) cm/s.

Research paper thumbnail of pH-Sensitive Vesicles Containing a Lipidic�-Amino Acid with Two Hydrophobic Chains

Chem Biodivers, 2008

The lipidic beta-amino acid 2-(aminomethyl)-2-pentadecylheptadecanoic acid (1) was synthesized vi... more The lipidic beta-amino acid 2-(aminomethyl)-2-pentadecylheptadecanoic acid (1) was synthesized via the alkylation of the C(alpha)-atom of fully protected beta-alanine. Mixed large unilamellar vesicles with a diameter between 100 and 200 nm containing POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine) and 1 at a molar ratio of 9 : 1 were prepared and found to have a surface charge which is dependent on pH. At slightly acidic pH, the vesicles were positively charged, and at alkaline pH negatively charged. Dynamic light scattering, zeta potential, and cryo-transmission electron-microscopy measurements indicated that the mixed vesicles fused at pH 4-5 with negatively charged mixed vesicles composed of POPC and POPG (9.8 : 1, molar ratio), POPG being 1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)].

Research paper thumbnail of Enzymatic Polymerization in Presence of Vesicles as Templates

Chimia International Journal For Chemistry, Nov 27, 2009

Research paper thumbnail of Modeling of enzymatic reactions in vesicles: The case of a-chymotrypsin

Biotechnol Bioeng, 1999

The kinetic behavior of the alpha-chymotrypsin-catalyzed hydrolysis of the two p-nitroanilide sub... more The kinetic behavior of the alpha-chymotrypsin-catalyzed hydrolysis of the two p-nitroanilide substrates succinyl-L-Ala-L-Ala-L-Pro-L-Phe-p-nitroanilide (Suc-Ala-Ala-Pro-Phe-pNA) and benzoyl-L-Tyr-p-nitroanilide (Bz-Tyr-pNA) was modeled and simulated for two different systems, namely for an aqueous solution and for a vesicle system, which was composed of phospholipid vesicles containing entrapped alpha-chymotrypsin. In the case of the vesicles, the substrate was added to the bulk, exovesicular aqueous phase. The experimentally determined time-dependence of product (p-nitroaniline) formation was modeled by considering the kinetic behavior of the enzyme and-in the case of vesicles-the substrate permeability across the bilayer membrane. In aqueous solution-without vesicles-the kinetic constants kcat and KS (respectively KM) were determined from fitting the model to experimental data of batch product concentration-time curves. The results were in good agreement with the corresponding values obtained from initial velocity measurements. For the vesicle system, using the phospholipid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), simulation showed that the substrate permeation across the bilayer was rate limiting. Using experimental data, we could obtain the substrate permeability coefficient for Bz-Tyr-pNA by parametric fitting as 2. 45 x 10(-7) cm/s.

Research paper thumbnail of Self-replicating micelles: aqueous micelles and enzymatically driven reactions in reverse micelles

J Am Chem Soc, 1991

... I-Pyrenesulfonic acid sodium salt (PSA) was from Mo-lecular Probes; pyrene, methylviologen ch... more ... I-Pyrenesulfonic acid sodium salt (PSA) was from Mo-lecular Probes; pyrene, methylviologen chloride (MV), and l -octanol from Aldrich; and K,Fe(CN), from Merck. ... (6) Lang, J.; Jada, A ... Micelle concentration ([MI) as determined by fluorescence quenching; uncertainty &8%. ...

Research paper thumbnail of Interaction of α-and β-Oligoarginine-Acids and Amides with Anionic Lipid Vesicles: A Mechanistic and Thermodynamic Study †

Biochemistry Usa, 2006

ABSTRACT

Research paper thumbnail of Autopoietic Self-Reproduction of Fatty Acid Vesicles

J Am Chem Soc, 1994

Conditions are described under which vesicles formed by caprylic acid and oleic acid in water are... more Conditions are described under which vesicles formed by caprylic acid and oleic acid in water are able to undergo autopoietic self-reproduction-namely an increase of their population number due to a reaction which takes place within the spherical boundary of the vesicles themselves. This is achieved by letting a certain amount of the neat water-insoluble caprylic or oleic anhydride hydrolyze at alkaline pH: the initial increase of the concentration of the released acidcarboxylate is extremely slow (several days to reach the conditions for spontaneous vesicle formation), but afterwards, the presence of vesicles brings about a rapid second phase leading to more and more vesicles being formed in an overall autocatalytic process. The catalytic power of the caprylic acid and oleic acid vesicles toward the hydrolysis of the corresponding anhydride is documented in a set of independent experiments. In these experiments, the hydrolysis was carried out in the presence of vesicles at a pH corresponding approximately to the pK of the acid in the vesicles. The process of autopoietic self-reproduction of caprylic acid and oleic acid vesicles is studied as a function of temperature: by increasing temperature (up to 70 "C), the exponential time progress of vesicle formation tends to become steeper while the long initial slow phase is significantly shortened. The caprylic acid and oleic acid vesicles are characterized by electron microscopy and by determining their internal volume. The question whether and to what extent these vesicles form a classic chemical equilibrium system-in which namely the free surfactant is in equilibrium with the aggregates-is also investigated.

Research paper thumbnail of Self-Reproduction of Micelles and Liposomes and the Transition to Life

J Liposome Res, 1993

ABSTRACT

Research paper thumbnail of Stable and Simple Immobilization of Proteinase K Inside Glass Tubes and Microfluidic Channels

ACS applied materials & interfaces, Jan 4, 2015

Engyodontium album proteinase K (proK) is widely used for degrading proteinaceous impurities duri... more Engyodontium album proteinase K (proK) is widely used for degrading proteinaceous impurities during the isolation of nucleic acid from biological samples, or in proteomics and prion research. Towards applications of proK in flow reactors, a simple method for the stable immobilization of proK inside glass micropipette tubes was developed. The immobilization of the enzyme was achieved by adsorption of a dendronized polymer-enzyme conjugate from aqueous solution. This conjugate was first synthesized from a polycationic dendronized polymer (denpol) and proK and consisted, on average, of 2000 denpol repeating units and 140 proK molecules, which were attached along the denpol chain via stable bis-aryl hydrazone bonds. Although the immobilization of proK inside the tube was based on non-specific, non-covalent interactions only, the immobilized proK did not leak from the tube and remained active during prolonged storage at 4 °C and during continuous operation at 25 °C and pH = 7.0. The proc...

Research paper thumbnail of Dynamic Aspects of Fatty Acid Vesicles: pH‐Induced Vesicle‐Micelle Transition and Dilution‐Induced Formation of Giant Vesicles

Research paper thumbnail of Enzymatic Reactions in Giant Vesicles

Perspectives in Supramolecular Chemistry, 1999

Research paper thumbnail of ChemInform Abstract: Achievements and Challenges in Generating Protocell Models

Research paper thumbnail of ChemInform Abstract: Liposomes Containing Purine and Pyrimidine Bases: Stable Unilamellar Liposomes from Phosphatidyl Nucleosides

ChemInform, 1994

ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance t... more ABSTRACT ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Research paper thumbnail of Efficient Polymerization of the Aniline Dimer p -Aminodiphenylamine (PADPA) with Trametes versicolor Laccase/O 2 as Catalyst and Oxidant and AOT Vesicles as Templates

ACS Catalysis, 2014

ABSTRACT The aniline dimer PADPA (= p-aminodiphenylamine = N-phenyl-1,4-phenylenediamine) was pol... more ABSTRACT The aniline dimer PADPA (= p-aminodiphenylamine = N-phenyl-1,4-phenylenediamine) was polymerized to poly(PADPA) at 25 °C with Trametes versicolor laccase (TvL)/O2 as catalyst and oxidant and in the presence of vesicles formed from sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as templates. In comparison to the previously studied polymerization of aniline with the same type of enzyme-vesicle system, the polymerization of PADPA is much faster, and considerably fewer enzymes are required for complete monomer conversion. Turbidity measurements indicate that PADPA strongly binds to the vesicle surface before oxidation and polymerization are initiated. Such binding is confirmed by molecular dynamics (MD) simulations, supporting the assumption that the reactions which lead to poly(PADPA) are localized on the vesicle surface. The poly(PADPA) obtained resembles the emeraldine salt form of polyaniline (PANI-ES) in its polaron state with a high content of unpaired electrons, as judged from UV/vis/NIR, EPR, and FTIR absorption measurements. There are, however, also notable spectroscopic differences between PANI-ES and the enzymatically prepared poly(PADPA). Poly(PADPA) appears to be similar to a chemically synthesized poly(PADPA) as obtained in a previous work with ammonium peroxydisulfate (APS) as the oxidant in a mixture of 50 vol % ethanol and 50 vol % 0.2 M sulfuric acid (J. Phys. Chem. B 2008, 112, 6976-6987). ESI-MS measurements of early intermediates of the reaction with TvL and AOT vesicles indicate that the presence of the vesicles decreases the extent of formation of unwanted oxygen-containing species in comparison to the reaction in the absence of vesicles. This is the first information about the differences in the chemical composition of early reaction intermediates when the reaction carried out in the presence of vesicles under optimal conditions is compared with a template-free system.

Research paper thumbnail of Liposomes Containing Purine and Pyrimidine Bases: Stable Unilamellar Liposomes from Phosphatidyl Nucleosides

The Journal of Physical Chemistry, 1994

ABSTRACT

Research paper thumbnail of Emergent properties arising from the assembly of amphiphiles. Artificial vesicle membranes as reaction promoters and regulators

Chemical communications (Cambridge, England), Jan 14, 2014

This article deals with artificial vesicles and their membranes as reaction promoters and regulat... more This article deals with artificial vesicles and their membranes as reaction promoters and regulators. Among the various molecular assemblies which can form in an aqueous medium from amphiphilic molecules, vesicle systems are unique. Vesicles compartmentalize the aqueous solution in which they exist, independent on whether the vesicles are biological vesicles (existing in living systems) or whether they are artificial vesicles (formed in vitro from natural or synthetic amphiphiles). After the formation of artificial vesicles, their aqueous interior (the endovesicular volume) may become - or may be made - chemically different from the external medium (the exovesicular solution), depending on how the vesicles are prepared. The existence of differences between endo- and exovesicular composition is one of the features on the basis of which biological vesicles contribute to the complex functioning of living organisms. Furthermore, artificial vesicles can be formed from mixtures of amphiph...

Research paper thumbnail of From self-assembled vesicles to protocells

Cold Spring Harbor perspectives in biology, 2010

Self-assembled vesicles are essential components of primitive cells. We review the importance of ... more Self-assembled vesicles are essential components of primitive cells. We review the importance of vesicles during the origins of life, fundamental thermodynamics and kinetics of self-assembly, and experimental models of simple vesicles, focusing on prebiotically plausible fatty acids and their derivatives. We review recent work on interactions of simple vesicles with RNA and other studies of the transition from vesicles to protocells. Finally we discuss current challenges in understanding the biophysics of protocells, as well as conceptual questions in information transmission and self-replication.

Research paper thumbnail of In vitro and in vivo anti-tumor effects of novel Span 80 vesicles containing immobilized Eucheuma serra agglutinin

International journal of pharmaceutics, Jan 15, 2010

The lectin Eucheuma serra agglutinin (ESA) is known from previous studies to specifically bind to... more The lectin Eucheuma serra agglutinin (ESA) is known from previous studies to specifically bind to high-mannose type N-glycans and to induce apoptotic cancer cell death in vitro. In this study, Span 80 vesicles, with an average diameter between about 200 and 400 nm, containing immobilized ESA were prepared from the nonionic surfactant Span 80, also known as sorbitan monooleate. The vesicles were investigated in vitro and in vivo to evaluate the vesicles's potential applicability as novel drug delivery system. The results obtained are promising since the following was observed: (i) vesicular ESA had the same hemagglutinating activity as free ESA, demonstrating its biological activity when bound to the vesicles; (ii) vesicles containing immobilized ESA decreased the viability of Colo201 cancer cells in vitro while the growth of normal cells was not affected; (iii) the vesicles showed binding to Colo201 cells in vitro and caused inhibition of cancer cell growth in nude mice to which...