The Experts below are selected from a list of 7134 Experts worldwide ranked by ideXlab platform

Gerald Brezesinski - One of the best experts on this subject based on the ideXlab platform.

  • Mixed dppc dptap Monolayers at the air water interface influence of indolilo 3 acetic acid and selenate ions on the monolayer morphology
    Langmuir, 2011
    Co-Authors: Barbara Gzylmalcher, Maria Filek, Gerald Brezesinski
    Abstract:

    The interactions of Mixed Monolayers of two lipids, zwitterionic 1,2-dipalmitoyl-phosphatidylcholine (DPPC) and positively charged 1,2-dipalmitoyl-3-trimethylammonium-propane (DPTAP), with phytohormone indolilo-3-acetic acid (IAA) and selenate anions in the aqueous subphase were studied. For this purpose, isotherms of the surface pressure versus the mean molecular area were recorded. Domain formation was investigated by using Brewster angle microscopy (BAM). The method of grazing incidence X-ray diffraction (GIXD) was also applied for the characterization of the organization of lipid molecules in condensed Monolayers. It was found that selenate ions contribute to monolayer condensation by neutralizing the positive net charge of Mixed Monolayers whereas IAA molecules penetrated the lipid monolayer, causing its expansion/fluidization. When both solutes were introduced into the subphase, a competition between them for interaction with the positively charged lipids in the monolayer was observed.

  • Mixed stearoyl rac glycerol 12 hydroxy stearoyl rac glycerol Monolayers on the air water interface brewster angle microscopy and grazing incidence x ray diffraction investigation
    Journal of Physical Chemistry B, 2000
    Co-Authors: N Krasteva, D Vollhardt, Gerald Brezesinski
    Abstract:

    Mixed Monolayers of 1-monostearoyl-rac-glycerol (StGl) and 1-(12-hydroxy)monostearoyl-rac-glycerol (12OH-StGl) were studied by means of pressure−area (π−A) isotherms, Brewster angle microscopy (BAM) and grazing incidence X-ray diffraction (GIXD). Thermodynamic analysis of the π−A isotherms of the Mixed films showed strong deviations from the ideal behavior at all compositions. Negative deviations from ideality are observed in the Monolayers with low 12OH-StGl content. The 12OH-StGl molecules are homogeneously distributed in the StGl matrix. The inclusion of 12OH-StGl molecules decreases the pressure at which the NN → NNN tilt transition occurs. A tilted phase with an oblique lattice and chain tilt in an intermediate (I) direction is observed in the Mixed Monolayers with small xOH values. With increasing mole fraction of the 12OH-StGl component positive deviations from ideal behavior are observed. The averaged interactions between the like molecules of the pure substances dominate, and the Mixed monolayer ...

Katsuhiko Ariga - One of the best experts on this subject based on the ideXlab platform.

  • dynamic control of intramolecular rotation by tuning the surrounding two dimensional matrix field
    ACS Nano, 2019
    Co-Authors: Katsuhiko Ariga, Taizo Mori, Hokyun Chin, Kazuhiro Kawashima, Waka Nakanishi, Jonathan P Hill
    Abstract:

    The intramolecular rotation of 4-farnesyloxyphenyl-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY-ISO) was controlled by tuning its local physical environment within a Mixed self-assembled monolayer at an air–water interface. Intramolecular rotation was investigated by considering the twisted intramolecular charge transfer (TICT) fluorescence of BODIPY-ISO, which increases in intensity with increasing viscosity of the medium. In situ fluorescence spectroscopy was performed on Mixed Monolayers of BODIPY-ISO with several different lipids at the air–water interface during in-plane compression of the Monolayers. Depending on the identity of the lipid used, the fluorescence of the Mixed Monolayers could be enhanced by mechanical compression, indicating that the rotation of BODIPY-ISO can be controlled dynamically in mixtures with lipids dispersed at the air–water interface. Taken together, our findings provide insight into strategies for controlling the dynamic behavior of molecular machines involving mech...

  • Dynamic Control of Intramolecular Rotation by Tuning the Surrounding Two-Dimensional Matrix Field
    2019
    Co-Authors: Taizo Mori, Hokyun Chin, Kazuhiro Kawashima, Waka Nakanishi, Jonathan P Hill, Huynh Thien Ngo, Nam-joon Cho, Katsuhiko Ariga
    Abstract:

    The intramolecular rotation of 4-farnesyloxyphenyl-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY-ISO) was controlled by tuning its local physical environment within a Mixed self-assembled monolayer at an air–water interface. Intramolecular rotation was investigated by considering the twisted intramolecular charge transfer (TICT) fluorescence of BODIPY-ISO, which increases in intensity with increasing viscosity of the medium. In situ fluorescence spectroscopy was performed on Mixed Monolayers of BODIPY-ISO with several different lipids at the air–water interface during in-plane compression of the Monolayers. Depending on the identity of the lipid used, the fluorescence of the Mixed Monolayers could be enhanced by mechanical compression, indicating that the rotation of BODIPY-ISO can be controlled dynamically in mixtures with lipids dispersed at the air–water interface. Taken together, our findings provide insight into strategies for controlling the dynamic behavior of molecular machines involving mechanical stimuli at interfaces

  • molecular patterning of a guanidinium orotate Mixed monolayer through molecular recognition with flavin adenine dinucleotide
    Langmuir, 1997
    Co-Authors: Yushi Oishi, Katsuhiko Ariga, Kazuhiro Taguchi, Yuzuru Torii, Takayuki Kato, Miyuki Kuramori, Kazuaki Suehiro, Ayumi Kamino, Hiroshi Koyano, Toyoki Kunitake
    Abstract:

    Flavin adenine dinucleotide (FAD) undergoes multisite molecular recognition at the air-water interface with Mixed Monolayers that are capable of complementary hydrogen bonding. Molecular images were obtained with an atomic force microscope (AFM) for Mixed Monolayers of guanidinium (G) and orotate (O) amphiphiles transferred from pure water and from aqueous FAD. The AFM image of the G/O Mixed monolayer on FAD showed a periodic oblique pattern composed of two kinds of methyl peaks with different heights, whereas that on pure water showed a periodic hexagonal pattern of only one kind of methyl peak. The two-dimensional molecular patterning as height difference is conceivably caused by rearrangement of monolayer components based on specific recognition by the FAD template molecule.

Masatoshi Osawa - One of the best experts on this subject based on the ideXlab platform.

  • Structure and Lateral Interaction in Mixed Monolayers of Dioctadecyldimethylammonium Chloride (DOAC) and Stearyl Alcohol
    2016
    Co-Authors: Tamim A Darwish, Michael James, Masatoshi Osawa
    Abstract:

    π–A isotherms, atomic force microscopy (AFM), and sum frequency generation (SFG) vibrational spectroscopy are employed to investigate the molecular structure and lateral interactions in Mixed Monolayers of dioctadecyldimethylammonium chloride (DOAC) and stearyl alcohol (SA) at air/water and air/solid interfaces. To avoid possible interference between the two molecules in the SFG spectroscopic measurements, perprotonated DOAC and perdeuterated SA (dSA) were used. The thermodynamic analyses for the π–A isotherms show that DOAC is miscible with dSA. SFG observations reveal that DOAC molecules become conformationally ordered as dSA molecules are introduced into the monolayer. AFM observations demonstrate coexistence of DOAC-rich and dSA-rich domains in the Mixed monolayer with ratios different from their initial composition in the subphase. The present study suggests that DOAC molecules in the Mixed monolayer are condensed by mixing with dSA in which the repulsive interactions between positively charged head groups of the DOAC molecules are largely reduced along with an increase of van der Waals interactions with dSA

  • structure and lateral interaction in Mixed Monolayers of dioctadecyldimethylammonium chloride doac and stearyl alcohol
    Langmuir, 2013
    Co-Authors: Tamim A Darwish, Michael James, Masatoshi Osawa
    Abstract:

    π-A isotherms, atomic force microscopy (AFM), and sum frequency generation (SFG) vibrational spectroscopy are employed to investigate the molecular structure and lateral interactions in Mixed Monolayers of dioctadecyldimethylammonium chloride (DOAC) and stearyl alcohol (SA) at air/water and air/solid interfaces. To avoid possible interference between the two molecules in the SFG spectroscopic measurements, perprotonated DOAC and perdeuterated SA (dSA) were used. The thermodynamic analyses for the π-A isotherms show that DOAC is miscible with dSA. SFG observations reveal that DOAC molecules become conformationally ordered as dSA molecules are introduced into the monolayer. AFM observations demonstrate coexistence of DOAC-rich and dSA-rich domains in the Mixed monolayer with ratios different from their initial composition in the subphase. The present study suggests that DOAC molecules in the Mixed monolayer are condensed by mixing with dSA in which the repulsive interactions between positively charged head groups of the DOAC molecules are largely reduced along with an increase of van der Waals interactions with dSA.

Juhyoun Kwak - One of the best experts on this subject based on the ideXlab platform.

  • Faradaic impedance titration of pure 3-mercaptopropionic acid and ethanethiol Mixed Monolayers on gold
    2016
    Co-Authors: Kyuwon Kim, Juhyoun Kwak
    Abstract:

    Interfacial proton transfer reactions of pure 3-mercaptopropionic acid (MPA) and ethanethiol (EtSH) Mixed self-assembled Monolayers (SAMs) have been studied using the faradaic impedance titration method. The Fe(CN)6 3 − is used to probe the charge development of the terminal COOH group of the Monolayers. The charge-transfer resistance (Rct) is measured with the monolayer composition, adsorption coverage, and the ionic strength of pH solution. The surface pK determined for the pure MPA is 6.0 at a monolayer coverage and 0.1 M ionic strength. The in-plane electrostatic force effect, which causes a broadening of the titration curves, on the surface pK for the MPA SAM is not significant at an ionic strength over 0.1 M. The pK value for the pure MPA SAM shifts negatively as the surface coverage decreases, indicating that the in-plane interactions between acids and the hydrophobicity surrounding acids decrease at the same time. When the pure MPA SAM is compared with the EtSH Mixed SAM, the surface pK of the Mixed SAM is larger than that of the pure SAM. Such positive pK shifts are more pronounced at the pure MPA SAM with a lower coverage. This implies that the pK shifts of sparsely adsorbed acidthiol SAM are more sensitive to the introduction of hydrophobicity than to the decrease of the in-plane interactions. © 2001 Elsevier Science B.V. All rights reserved

  • faradaic impedance titration of pure 3 mercaptopropionic acid and ethanethiol Mixed Monolayers on gold
    Journal of Electroanalytical Chemistry, 2001
    Co-Authors: Kyuwon Kim, Juhyoun Kwak
    Abstract:

    Abstract Interfacial proton transfer reactions of pure 3-mercaptopropionic acid (MPA) and ethanethiol (EtSH) Mixed self-assembled Monolayers (SAMs) have been studied using the faradaic impedance titration method. The Fe(CN) 6 3− is used to probe the charge development of the terminal COOH group of the Monolayers. The charge-transfer resistance ( R ct ) is measured with the monolayer composition, adsorption coverage, and the ionic strength of pH solution. The surface p K determined for the pure MPA is 6.0 at a monolayer coverage and 0.1 M ionic strength. The in-plane electrostatic force effect, which causes a broadening of the titration curves, on the surface p K for the MPA SAM is not significant at an ionic strength over 0.1 M. The p K value for the pure MPA SAM shifts negatively as the surface coverage decreases, indicating that the in-plane interactions between acids and the hydrophobicity surrounding acids decrease at the same time. When the pure MPA SAM is compared with the EtSH Mixed SAM, the surface p K of the Mixed SAM is larger than that of the pure SAM. Such positive p K shifts are more pronounced at the pure MPA SAM with a lower coverage. This implies that the p K shifts of sparsely adsorbed acidthiol SAM are more sensitive to the introduction of hydrophobicity than to the decrease of the in-plane interactions.

Toyoki Kunitake - One of the best experts on this subject based on the ideXlab platform.

  • molecular patterning of a guanidinium orotate Mixed monolayer through molecular recognition with flavin adenine dinucleotide
    Langmuir, 1997
    Co-Authors: Yushi Oishi, Katsuhiko Ariga, Kazuhiro Taguchi, Yuzuru Torii, Takayuki Kato, Miyuki Kuramori, Kazuaki Suehiro, Ayumi Kamino, Hiroshi Koyano, Toyoki Kunitake
    Abstract:

    Flavin adenine dinucleotide (FAD) undergoes multisite molecular recognition at the air-water interface with Mixed Monolayers that are capable of complementary hydrogen bonding. Molecular images were obtained with an atomic force microscope (AFM) for Mixed Monolayers of guanidinium (G) and orotate (O) amphiphiles transferred from pure water and from aqueous FAD. The AFM image of the G/O Mixed monolayer on FAD showed a periodic oblique pattern composed of two kinds of methyl peaks with different heights, whereas that on pure water showed a periodic hexagonal pattern of only one kind of methyl peak. The two-dimensional molecular patterning as height difference is conceivably caused by rearrangement of monolayer components based on specific recognition by the FAD template molecule.