| DOI | Resolve DOI: https://doi.org/10.1063/1.1862613 |
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| Author | Search for: Mitchell, S.1; Search for: McAloney, R.1; Search for: Moffatt, Douglas1; Search for: Mora-Diez, N.1; Search for: Zgierski, Marek1 |
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| Affiliation | - National Research Council of Canada. NRC Steacie Institute for Molecular Sciences
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| Format | Text, Article |
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| Subject | chirality; interface phenomena; molecular configurations; nonlinear optical susceptibility; optical harmonic generation; optical rotation; polarisability; polymers |
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| Abstract | Quantitative measurements of second-harmonic generation optical activity (SHG-OA) have been performed for αα-helical polypeptides poly-(γγ-benzyl-LL-glutamate) and poly-(γγ-ethyl-LL-glutamate) adsorbed at the air∕water interface, with the fundamental frequency ℏω=2.96eVℏω=2.96eV (λ=417nm)(λ=417nm). The chiral component of the nonlinear susceptibilityχ(2)XYZχXYZ(2) is small for both polymers, being comparable in magnitude with the susceptibility χ(2)XXZχXXZ(2) of the clean air∕water interface. The microscopic origin of the nonlinear response has been investigated by using semiempirical ZINDO∕S calculations in conjunction with standard time-dependent perturbation theory to evaluate the molecular hyperpolarizability tensor of a model αα-helix composed of glycine residues. Calculated nonlinear susceptibilities (per monomer unit) are in good agreement with experimental measurements for both the chiral and achiral response. The computational results indicate that charge transfer transitions of the αα-helix have a large influence on the achiral components of the hyperpolarizability tensor, and produce characteristic features in the response under suitable experimental conditions. The dominant origin of SHG-OA for the model αα-helix is a structural effect due to the tilt of the plane of each amide group of the helix relative to the helical axis. SHG-OA is associated with the orientational distribution of isolated, achiral chromophores, and is present in the absence of electronic coupling between the amide subunits of the polypeptide αα-helix. |
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| Publication date | 2005-03-15 |
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| In | |
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| Language | English |
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| Peer reviewed | Yes |
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| NPARC number | 12328140 |
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| Export citation | Export as RIS |
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| Report a correction | Report a correction (opens in a new tab) |
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| Record identifier | df0a8259-4bd5-44b8-8226-d7626967c07c |
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| Record created | 2009-09-10 |
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| Record modified | 2020-04-07 |
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