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Volumn 112, Issue 5, 2008, Pages 1350-1357

Structure and dynamics of an extended conjugated NLO chromophore within an amphiphilic 4-helix bundle peptide by molecular dynamics simulation

Author keywords

[No Author keywords available]

Indexed keywords

CHROMOPHORES; COMPUTER SIMULATION; OPTIMIZATION; PEPTIDES; POLARIZATION;

EID: 39649088460     PISSN: 15206106     EISSN: None     Source Type: Journal    
DOI: 10.1021/jp076643j     Document Type: Article
Times cited : (14)

References (43)
  • 15
    • 84906378632 scopus 로고    scopus 로고
    • Polarized resonant second-harmonic generation (SHG) from single monolayers of either the apo form of the amphiphilic 4-helix bundle peptide APO or the holo form with a bridged Ru-polypyridyl Zn-porphyrin chromophore designated Ru-PZn at a stoichiometry of one chromophore per 4-helix bundle covalently attached to the surface of fused silica was investigated. A pulsed-laser system was employed, operating at the fundamental wavelength of 840 nm, a repetition rate of 76 MHz, and a pulse width of 100 fs. The fundamental beam was incident at 30° to the plane of the substrate. S- and P-polarized second harmonic at 420 nm was measured in transmission through the substrate (i.e, along the incident beam direction) and observed only for the holo form of the peptide, i.e, when the Ru-PZn chromophore was present. Damage to the monolayer specimens was observed in this nearly CW mode (i.e, 76 MHz) at relatively high peak power densities of ∼4400 MW/cm2. Reduction of
    • -30 esu. Note that while these SHG measurements were performed with a fundamental of 840 nm, the chromohore's dynamic hyperpolarizability was shown in the reference to increase from 40- to 100-fold at the longer fundamental wavelengths of 1064 and 1300 nm, respectively, relative to that at 800 nm. Gonella, G.; Tronin, A.; Dai, H.-L.; Blasie, J. K. Orientational Order and Hyperpolarizability of Nonlinear Chromophore Molecules Supported in Amphiphilic 4-Helix Bundle Peptides. Manuscript in preparation.
  • 19
    • 84906364329 scopus 로고    scopus 로고
    • The amphiphilic bundle APO was designed to facilitate its vectorial insertion at soft interfaces between polar and nonpolar media. The interface between water and a long-chain alkane (e.g, octane) provides a model interface to address the stability of the structures of the designed bundles incorporating such NLO chromophores to the local anisotropy of the interface via classical MD simulation, the subject of this investigation. In this case, the hydrophilic and hydrophobic domains of the bundle, oriented with its long-axis perpendicular to the interface, would be anticipated to interact only with their respective water and octane environments in the absence of any interactions with neighboring bundles and/or applied external forces. We refer to this situation as the isolated bundle case. It is more relevant to spectroscopic studies of chromophore conformation and dynamics within the detergent-solubilized AP0-chromophore complex in isotropic solution, including circu
    • The amphiphilic bundle APO was designed to facilitate its vectorial insertion at soft interfaces between polar and nonpolar media. The interface between water and a long-chain alkane (e.g., octane) provides a model interface to address the stability of the structures of the designed bundles incorporating such NLO chromophores to the local anisotropy of the interface via classical MD simulation, the subject of this investigation. In this case, the hydrophilic and hydrophobic domains of the bundle, oriented with its long-axis perpendicular to the interface, would be anticipated to interact only with their respective water and octane environments in the absence of any interactions with neighboring bundles and/or applied external forces. We refer to this situation as the "isolated bundle" case. It is more relevant to spectroscopic studies of chromophore conformation and dynamics within the detergent-solubilized AP0-chromophore complex in isotropic solution, including circular dichroism (ref 40) or hyper-Rayleigh scattering (ref 41). However, it is extremely difficult to realize any definitive experimental results with an extended planar interface for the water-octane system. To date, only very simple amphiphiles (e.g., long-chain alcohols) have been studied at such a water-alkane interface (ref 42). Complex amphiphiles, with limited solubility in either polar or nonpolar media such as the amphiphilic 4-helix bundle APO, are much more easily studied in Langmuir monolayers at the water-air interface with control of lateral surface pressure (ref 29). The helices associate to form a 2-D ensemble of 4-helix bundles with their long axis oriented perpendicular to the interface only at higher surface pressures, corresponding to minimal average areas per helix in the plane of the interface. In this situation, the hydrophobic domain of the bundle is stabilized by favorable nonpolar interactions with those domains of neighboring bundles. Thus, small ensemble simulations of the amphiphilic bundles at the water-air interface (ref 16) would provide a more direct comparison with the experiments sensitive to macromolecular structure and dynamics at an extended planar interface (e.g., as provided by neutron reflectivity and relevant to Table Sl in the Supporting Information).
  • 27
    • 84906392314 scopus 로고    scopus 로고
    • In spite of the above, we do note that there remain some differences in the equilibrated structures of the F6H20-hydrophilic holo form dependent on the initial configuration. These differences are, however, of little relevance to this communication as they concern only small differences in the precise location of the chromophore within the core of the hydrophilic domain of APO (both with regard to its position along the length and within the cross-section of the 4-helix bundle, These differences are manifest in the time-averaged positions of selected residues along the length of the bundle axis (Table S1 in the Supporting Information, Some are of sufficient magnitude to be experimentally measurable employing neutron reflectivity from Langmuir monolayers of the peptide-chromophore complex at the water-air interface at higher surface pressures coupled with the perdeuteration of these selected residues one at a time ref 43
    • In spite of the above, we do note that there remain some differences in the equilibrated structures of the F6H20-hydrophilic holo form dependent on the initial configuration. These differences are, however, of little relevance to this communication as they concern only small differences in the precise location of the chromophore within the core of the hydrophilic domain of APO (both with regard to its position along the length and within the cross-section of the 4-helix bundle). These differences are manifest in the time-averaged positions of selected residues along the length of the bundle axis (Table S1 in the Supporting Information). Some are of sufficient magnitude to be experimentally measurable employing neutron reflectivity from Langmuir monolayers of the peptide-chromophore complex at the water-air interface at higher surface pressures coupled with the perdeuteration of these selected residues one at a time (ref 43).
  • 40
    • 0342804291 scopus 로고    scopus 로고
    • For a thorough discussion, see
    • For a thorough discussion, see Kuball, H. G.; Höffer, T. Chirality 2000, 12, 278.
    • (2000) Chirality , vol.12 , pp. 278
    • Kuball, H.G.1    Höffer, T.2


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.