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Avinash Bajaj – One of the best experts on this subject based on the ideXlab platform.

  • synthesis structure activity relationship and mechanistic investigation of lithocholic acid Amphiphiles for colon cancer therapy
    MedChemComm, 2015
    Co-Authors: Manish Singh, Sandhya Bansal, Somanath Kundu, Priyanshu Bhargava, Ashima Singh, Rajender K. Motiani, Radhey Shyam, Vedagopuram Sreekanth, Sagar Sengupta, Avinash Bajaj
    Abstract:

    We report a structure–activity relationship of lithocholic acid Amphiphiles for their anticancer activities against colon cancer. We synthesized ten cationic Amphiphiles, differing in nature of their cationic charged head groups, using lithocholic acid. We observed that anticancer activities of these Amphiphiles against colon cancer cell lines are contingent on nature of the charged head group. The lithocholic acid-based amphiphile possessing a piperidine head group (LCA-PIP1) is ∼10 times more cytotoxic than its precursor. Biochemical studies revealed that enhanced activity of LCA-PIP1 compared to lithocholic acid is due to a greater activation of apoptosis. LCA-PIP1 induces sub G0 arrest and causes cleavage of caspases. A single dose of lithocholic acid–piperidine (LCA-PIP1) derivative is enough to reduce the tumor burden by 75% in a tumor xenoxenograft model.

  • Synthesis, structure–activity relationship, and mechanistic investigation of lithocholic acid Amphiphiles for colon cancer therapy
    MedChemComm, 2014
    Co-Authors: Manish Singh, Sandhya Bansal, Somanath Kundu, Priyanshu Bhargava, Ashima Singh, Rajender K. Motiani, Radhey Shyam, Vedagopuram Sreekanth, Sagar Sengupta, Avinash Bajaj
    Abstract:

    We report a structure–activity relationship of lithocholic acid Amphiphiles for their anticancer activities against colon cancer. We synthesized ten cationic Amphiphiles, differing in nature of their cationic charged head groups, using lithocholic acid. We observed that anticancer activities of these Amphiphiles against colon cancer cell lines are contingent on nature of the charged head group. The lithocholic acid-based amphiphile possessing a piperidine head group (LCA-PIP1) is ∼10 times more cytotoxic than its precursor. Biochemical studies revealed that enhanced activity of LCA-PIP1 compared to lithocholic acid is due to a greater activation of apoptosis. LCA-PIP1 induces sub G0 arrest and causes cleavage of caspases. A single dose of lithocholic acid–piperidine (LCA-PIP1) derivative is enough to reduce the tumor burden by 75% in a tumor xenoxenograft model.

Matthew Tirrell – One of the best experts on this subject based on the ideXlab platform.

  • self assembly of model dna binding peptide Amphiphiles
    Langmuir, 2005
    Co-Authors: Ronit Bitton, Judith Schmidt, Markus Biesalski, Raymond S Tu, Matthew Tirrell, Havazelet Biancopeled
    Abstract:

    Peptide Amphiphiles combine the specific functionality of proteins with the engineering convenience of synthetic Amphiphiles. These molecules covalently link a peptide headgroup, typically from an active fragment of a larger protein, to a hydrophobic alkyl tail. Our research is aimed at forming and characterizing covalently stabilized, self-assembled, peptide-amphiphile aggregates that can be used as a platform for the examination and modular design and construction of systems with engineering biological activity. We have studied the self-assembly properties of a model DNA-binding amphiphile, having a GCN4 peptide as the headgroup and containing a polymerizable methacrylic group in the tail region, using a combination of small-angle X-ray scattering, small-angle neutron scattering, and cryo- transmission elecelectron microscopy. Our results reveal a variety of morphologies in this system. The peptide Amphiphiles assembled in aqueous solution to helical ribbons and tubules. These structures transformed into la…

  • Cell adhesion on a polymerized peptide-amphiphile monolayer.
    Biomaterials, 2005
    Co-Authors: Markus Biesalski, Raymond S Tu, Alexandra Knaebel, Matthew Tirrell
    Abstract:

    Abstract We report the synthesis and characterization of a stable polymerized monolayer of peptide–amphihiles on a planar solid support that promotes mouse fibroblast cell adheadhesion and spreading. PeptideAmphiphiles consisting of a polymerizable fatty acid attached to a short RGD containing peptide sequence are self-assembled and polymerized at the water–air interface by means of the Langmuir– Blodgett technique. The surface concentration of the peptide–amphiphile is varied by co-spreading the peptide–amphiphile with an analogous non-modified polymerizable amphiphile at the water/air interface, prior to UV light-induced polymerization. The polymerized monolayer is transferred onto a hydrophobized smooth mica surface and the resulting surfaces have been investigated with respect to directing the cell adheadhesion and spreading of mouse fibroblast cells in a serum-free medium. Fibroblast cells adhere and spread on surfaces exposing the bioactive ligand but do not spread on reference surfaces without peptide. We find a maximum number of adherent cells at rather high peptide surface concentrations of about 10 mol% in the mixed monolayer, equivalent to more than 50 pmol/cm2 peptide on the surface of the film. We attribute this finding to a limited accessibility of the ligands by the integrins. Because of the stability of the polymerized peptide–amphiphile monolayer, these surfaces can be re-seeded multiple times with cells, i.e. adherent cells can be removed from the surface, the surface can be sterilized and cells can be re-attached.

  • structure and function of integral membrane protein domains resolved by peptide Amphiphiles application to phospholamban
    Biopolymers, 2003
    Co-Authors: Nathan A. Lockwood, Raymond S Tu, Matthew Tirrell, Zhiwen Zhang, David D. Thomas, Christine B Karim
    Abstract:

    We have used synthetic lipidated peptides (“peptideAmphiphiles”) to study the structure and function of isolated domains of integral transmembrane proteins. We used 9-fluorenylmethyloxycarbonyl (Fmoc) solid-phase peptide synthesis to prepare full-length phospholamban (PLB1–52) and its cytoplasmic (PLB1–25K: phospholamban residues 1–25 plus a C-terminal lysine), and transmembrane (PLB26–52) domains, and a 38-residue model α-helical sequence as a control. We created peptideAmphiphiles by linking the C-terminus of either the isolated cytoplasmic domain or the model peptide to a membrane-anchoring, lipid-like hydrocarbon tail. Circular dichdichroism measurements showed that the model peptide-amphiphile, either in aqueous suspension or in lipid bilayers, had a higher degree of α-helical secondary structure than the unlipidated model peptide. We hypothesized that the peptide-amphiphile system would allow us to study the function and structure of the PLB1–25K cytoplasmic domain in a native-like configuration. We compared the function (inhibition of the Ca-ATPase in reconstituted membranes) and structure (via CD) of the PLB1–25 amphiphile to that of PLB and its isolated transmembrane and cytoplasmic domains. Our results indicate that the cytoplasmic domain PLB1–25K has no effect on Ca-ATPase (calcium pump) activity, even when tethered to the membrane in a manner mimicking its native configuration, and that the transmembrane domain of PLB is sufficient for inhibition of the Ca-ATPase. © 2003 Wiley Periodicals, Inc. Biopolymers 69: 283–292, 2003

Jan C M Van Hest – One of the best experts on this subject based on the ideXlab platform.

  • Sensing cell adhesion using polydiacetylene-containing peptide amphiphile fibres
    Journal of Materials Chemistry B, 2015
    Co-Authors: Britta E. I. Ramakers, Jan C M Van Hest, S.a. Bode, Anouk R. Killaars, Dennis W P M Lowik
    Abstract:

    Sensing cell adheadhesion by means of a colourimetric response provides an intuitive measure of cell binding. In this study polydiacetylene-containing peptide Amphiphiles fibres were designed to sense cell adheadhesion by means of a colour change. The diacetylene-containing peptide Amphiphiles were functionalised with the cell-binding motif RGDS, and subsequently mixed with non-functionalised diacetylene-containing spacer Amphiphiles. The diacetylenes in the backbone of these fibres were polymerised using UV-light to give dark blue fibre solutions. Subsequent cell adheadhesion induced a colour change from blue to pink. The propensity of the RGDS fibres to change colour upon cell adheadhesion could be tuned by varying the C-terminal amino acid of the spacer amphiphile. In addition to this, by varying the RGDS density we found that the optimum colourimetric response was obtained for fibres with a 6:1 ratio of non-RGDS to RGDS Amphiphiles.

  • self assembly and polymerization of diacetylene containing peptide Amphiphiles in aqueous solution
    Biomacromolecules, 2008
    Co-Authors: Maaike Van Den Heuvel, Dennis W P M Lowik, Jan C M Van Hest
    Abstract:

    A systematic study was performed of the fiber forming properties and polymerization characteristics of two peptide Amphiphiles containing a diacetylene functionality in the alkyl tail comprising 23 and 25 C atoms, respectively. Both diyne containing peptide Amphiphiles were able to form stable β-sheet fibers of micrometers length in an aqueous solution. However, there was a large difference between the stability of the two Amphiphiles. This was shown by a large difference in assembly and disassembly temperature and by different behavior during polymerization. Because the monomers were preorganized with a tight molecular packing, the polymerization could be carried out using wavelengths up to 532 nm. For both Amphiphiles, the fiber structure did not change when the polymerization was carried out at an elevated temperature. The degree of polypolymerization, however, barely decreased for the longer amphiphile (2) but showed a gradual decline for the shorter one (1) when the temperature was raised from room tempe…

  • Controlled disassembly of peptide amphiphile fibres
    Journal of Peptide Science, 2008
    Co-Authors: Dennis W P M Lowik, Joris T. Meijer, Inge J. Minten, Henri A. Van Kalkeren, Lisa Heckenmüller, Ines E. Schulten, Kwinten Sliepen, Peter Smittenaar, Jan C M Van Hest
    Abstract:

    In this paper, the introduction of both a methionine residue and a nitrobenzyl derivative as a labile linker between the peptide part and the hydrophobic alkyl chain of a peptide amphiphile are presented. These modifications are shown not to inhibit the formation of structured assemblies that analogous peptide Amphiphiles lacking the linkers are able to form. Moreover, the introduction of either labile linker allows removal of the peptide amphiphile’s stabilizing hydrophobic moieties to initiate a controlled disassembly of fibre aggregates. This is achieved by either treatment with CNBr or UV irradiation, respectively. These disassembly mechanisms could be the starting point for methodology that allows further manipulation of self-assembled peptide amphiphile architectures. Copyright  2007 European Peptide Society and John Wiley & Sons, Ltd. Supplementary electronic material for this paper is available in Wiley InterScience at http://www.interscience.wiley.com/jpages/ 1075-2617/suppmat/

Dennis W P M Lowik – One of the best experts on this subject based on the ideXlab platform.

  • Sensing cell adhesion using polydiacetylene-containing peptide amphiphile fibres
    Journal of Materials Chemistry B, 2015
    Co-Authors: Britta E. I. Ramakers, Jan C M Van Hest, S.a. Bode, Anouk R. Killaars, Dennis W P M Lowik
    Abstract:

    Sensing cell adhesion by means of a colourimetric response provides an intuitive measure of cell binding. In this study polydiacetylene-containing peptide Amphiphiles fibres were designed to sense cell adhesion by means of a colour change. The diacetylene-containing peptide Amphiphiles were functionalised with the cell-binding motif RGDS, and subsequently mixed with non-functionalised diacetylene-containing spacer Amphiphiles. The diacetylenes in the backbone of these fibres were polymerised using UV-light to give dark blue fibre solutions. Subsequent cell adhesion induced a colour change from blue to pink. The propensity of the RGDS fibres to change colour upon cell adhesion could be tuned by varying the C-terminal amino acid of the spacer amphiphile. In addition to this, by varying the RGDS density we found that the optimum colourimetric response was obtained for fibres with a 6:1 ratio of non-RGDS to RGDS Amphiphiles.

  • self assembly and polymerization of diacetylene containing peptide Amphiphiles in aqueous solution
    Biomacromolecules, 2008
    Co-Authors: Maaike Van Den Heuvel, Dennis W P M Lowik, Jan C M Van Hest
    Abstract:

    A systematic study was performed of the fiber forming properties and polymerization characteristics of two peptide Amphiphiles containing a diacetylene functionality in the alkyl tail comprising 23 and 25 C atoms, respectively. Both diyne containing peptide Amphiphiles were able to form stable β-sheet fibers of micrometers length in an aqueous solution. However, there was a large difference between the stability of the two Amphiphiles. This was shown by a large difference in assembly and disassembly temperature and by different behavior during polymerization. Because the monomers were preorganized with a tight molecular packing, the polymerization could be carried out using wavelengths up to 532 nm. For both Amphiphiles, the fiber structure did not change when the polymerization was carried out at an elevated temperature. The degree of polymerization, however, barely decreased for the longer amphiphile (2) but showed a gradual decline for the shorter one (1) when the temperature was raised from room tempe…

  • Controlled disassembly of peptide amphiphile fibres
    Journal of Peptide Science, 2008
    Co-Authors: Dennis W P M Lowik, Joris T. Meijer, Inge J. Minten, Henri A. Van Kalkeren, Lisa Heckenmüller, Ines E. Schulten, Kwinten Sliepen, Peter Smittenaar, Jan C M Van Hest
    Abstract:

    In this paper, the introduction of both a methionine residue and a nitrobenzyl derivative as a labile linker between the peptide part and the hydrophobic alkyl chain of a peptide amphiphile are presented. These modifications are shown not to inhibit the formation of structured assemblies that analogous peptide Amphiphiles lacking the linkers are able to form. Moreover, the introduction of either labile linker allows removal of the peptide amphiphile’s stabilizing hydrophobic moieties to initiate a controlled disassembly of fibre aggregates. This is achieved by either treatment with CNBr or UV irradiation, respectively. These disassembly mechanisms could be the starting point for methodology that allows further manipulation of self-assembled peptide amphiphile architectures. Copyright  2007 European Peptide Society and John Wiley & Sons, Ltd. Supplementary electronic material for this paper is available in Wiley InterScience at http://www.interscience.wiley.com/jpages/ 1075-2617/suppmat/

Raymond S Tu – One of the best experts on this subject based on the ideXlab platform.

  • self assembly of model dna binding peptide Amphiphiles
    Langmuir, 2005
    Co-Authors: Ronit Bitton, Judith Schmidt, Markus Biesalski, Raymond S Tu, Matthew Tirrell, Havazelet Biancopeled
    Abstract:

    Peptide Amphiphiles combine the specific functionality of proteins with the engineering convenience of synthetic Amphiphiles. These molecules covalently link a peptide headgroup, typically from an active fragment of a larger protein, to a hydrophobic alkyl tail. Our research is aimed at forming and characterizing covalently stabilized, self-assembled, peptide-amphiphile aggregates that can be used as a platform for the examination and modular design and construction of systems with engineering biological activity. We have studied the self-assembly properties of a model DNA-binding amphiphile, having a GCN4 peptide as the headgroup and containing a polymerizable methacrylic group in the tail region, using a combination of small-angle X-ray scattering, small-angle neutron scattering, and cryo- transmission electron microscopy. Our results reveal a variety of morphologies in this system. The peptide Amphiphiles assembled in aqueous solution to helical ribbons and tubules. These structures transformed into la…

  • Cell adhesion on a polymerized peptide-amphiphile monolayer.
    Biomaterials, 2005
    Co-Authors: Markus Biesalski, Raymond S Tu, Alexandra Knaebel, Matthew Tirrell
    Abstract:

    Abstract We report the synthesis and characterization of a stable polymerized monolayer of peptide–amphihiles on a planar solid support that promotes mouse fibroblast cell adhesion and spreading. Peptide–Amphiphiles consisting of a polymerizable fatty acid attached to a short RGD containing peptide sequence are self-assembled and polymerized at the water–air interface by means of the Langmuir– Blodgett technique. The surface concentration of the peptide–amphiphile is varied by co-spreading the peptide–amphiphile with an analogous non-modified polymerizable amphiphile at the water/air interface, prior to UV light-induced polymerization. The polymerized monolayer is transferred onto a hydrophobized smooth mica surface and the resulting surfaces have been investigated with respect to directing the cell adhesion and spreading of mouse fibroblast cells in a serum-free medium. Fibroblast cells adhere and spread on surfaces exposing the bioactive ligand but do not spread on reference surfaces without peptide. We find a maximum number of adherent cells at rather high peptide surface concentrations of about 10 mol% in the mixed monolayer, equivalent to more than 50 pmol/cm2 peptide on the surface of the film. We attribute this finding to a limited accessibility of the ligands by the integrins. Because of the stability of the polymerized peptide–amphiphile monolayer, these surfaces can be re-seeded multiple times with cells, i.e. adherent cells can be removed from the surface, the surface can be sterilized and cells can be re-attached.

  • structure and function of integral membrane protein domains resolved by peptide Amphiphiles application to phospholamban
    Biopolymers, 2003
    Co-Authors: Nathan A. Lockwood, Raymond S Tu, Matthew Tirrell, Zhiwen Zhang, David D. Thomas, Christine B Karim
    Abstract:

    We have used synthetic lipidated peptides (“peptide-Amphiphiles”) to study the structure and function of isolated domains of integral transmembrane proteins. We used 9-fluorenylmethyloxycarbonyl (Fmoc) solid-phase peptide synthesis to prepare full-length phospholamban (PLB1–52) and its cytoplasmic (PLB1–25K: phospholamban residues 1–25 plus a C-terminal lysine), and transmembrane (PLB26–52) domains, and a 38-residue model α-helical sequence as a control. We created peptide-Amphiphiles by linking the C-terminus of either the isolated cytoplasmic domain or the model peptide to a membrane-anchoring, lipid-like hydrocarbon tail. Circular dichroism measurements showed that the model peptide-amphiphile, either in aqueous suspension or in lipid bilayers, had a higher degree of α-helical secondary structure than the unlipidated model peptide. We hypothesized that the peptide-amphiphile system would allow us to study the function and structure of the PLB1–25K cytoplasmic domain in a native-like configuration. We compared the function (inhibition of the Ca-ATPase in reconstituted membranes) and structure (via CD) of the PLB1–25 amphiphile to that of PLB and its isolated transmembrane and cytoplasmic domains. Our results indicate that the cytoplasmic domain PLB1–25K has no effect on Ca-ATPase (calcium pump) activity, even when tethered to the membrane in a manner mimicking its native configuration, and that the transmembrane domain of PLB is sufficient for inhibition of the Ca-ATPase. © 2003 Wiley Periodicals, Inc. Biopolymers 69: 283–292, 2003