Determination of Anisotropic Optical Constants and Surface Coverage of Molecular Films Using Polarized Visible ATR Spectroscopy. Application to Adsorbed Cytochrome <i>c</i> Films

Runge, Anne F.; Rasmussen, Nicole C.; Saavedra, S. Scott; Mendes, Sergio B.

doi:10.1021/jp045727e

Cited by 21 publications

(47 citation statements)

References 42 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For the application of those equations, we experimentally determined that the refractive index of the alumina waveguide thin film can be described by: n w = a + ( b )/( λ 2 ) + ( c )/( λ 4 ), where a = 1.645 76, b = 42.898 98, and c = 308 958 233.142. For the refractive index of the aqueous buffer solution, we used n c = 1.33, and the approximation30 that n l ≈ n c . As previously mentioned, the thickness of the guiding film is given by t = 180 nm, and the distance between the input and output couplers is L = 3.4 cm.…”

Section: Resultsmentioning

confidence: 99%

Investigations on the Q and CT Bands of Cytochrome c Submonolayer Adsorbed on an Alumina Surface Using Broadband Spectroscopy with Single-Mode Integrated Optical Waveguides

et al. 2009

Self Cite

View full text Add to dashboard Cite

In this work, we report experimental results on the molar absorptivity of cytochrome c adsorbed at different submonolayer levels onto an aluminum oxide waveguide surface; our data show a clear dependence of the protein optical properties on its surface density. The measurements were performed using the broadband, single-mode, integrated optical waveguide spectroscopic technique, which is an extremely sensitive tool able to reach submonolayer levels of detection required for this type of studies. This investigation focuses on the molar absorptivity at the Q-band (centered at 525 nm) and, for the first time to our knowledge, the weak charge transfer (CT) band (centered at 695 nm) of surface-adsorbed cyt c. Polarized light in the spectral region from 450 to 775 nm was all-coupled into an alumina thin film, which functioned as a single-mode planar optical waveguide. The alumina thin-film waveguide used for this work had a thickness of 180 nm and was deposited on a glass substrate by the atomic layer deposition process. The protein submonolayer was formed on the alumina waveguide surface through electrostatic adsorption from an aqueous buffer solution at neutral pH. The optical properties of the surface-adsorbed cyt c were investigated for bulk protein concentrations ranging from 5 nM to 8200 nM in the aqueous buffer solution. For a protein surface density of 2.3 pmol/cm 2 , the molar absorptivity measured at the charge transfer band was 335 M −1 cm −1 , and for a surface density of 15 pmol/cm 2 was 720 M −1 cm −1 , which is much closer to the value of cyt c dissolved in an aqueous neutral buffer (830 M −1 cm −1 ). The modification of the protein molar absorptivity and its dependence on the surface density can most likely be attributed to conformational changes of the surface-adsorbed species.

show abstract

Section: Resultsmentioning

confidence: 99%

Investigations on the Q and CT Bands of Cytochrome c Submonolayer Adsorbed on an Alumina Surface Using Broadband Spectroscopy with Single-Mode Integrated Optical Waveguides

et al. 2009

Self Cite

View full text Add to dashboard Cite

show abstract

“…3,53 By combining eqs 8 and 9, we obtain Similarly, by combining eqs 10 and 11, and using eqs 18 and 19, we obtain…”

Section: Polarized Fluorescencementioning

confidence: 95%

Combination of Polarized TIRF and ATR Spectroscopies for Determination of the Second and Fourth Order Parameters of Molecular Orientation in Thin Films and Construction of an Orientation Distribution Based on the Maximum Entropy Method

2006

Self Cite

View full text Add to dashboard Cite

This article describes two mathematical formalisms for the determination of the second and fourth order parameters of molecular films using optical spectroscopy. Method A uses polarized total internal reflection fluorescence (TIRF) to calculate the second and fourth order parameters, 〈P 2 (cos θ)〉 and 〈P 4 (cos θ)〉, using an independently determined value for the angle between the absorption and emission dipoles, γ. Method B uses 〈P 2 (cos θ)〉 obtained from attenuated total reflectance (ATR) data, along with polarized TIRF measurements to calculate 〈P 4 (cos θ)〉 and 〈cos 2 γ〉. The choice of a specific method should rely on experimental considerations. We also present a method to separate the contributions of substrate surface roughness and dipole orientation with respect to the molecular axis from the spectroscopically determined second and fourth order parameters. Finally, a maximum entropy approach for construction of an orientation distribution from order parameters is compared with the commonly used delta and Gaussian distributions.

show abstract

“…The linear fitting results for electron transfer rate for both polarizations were shown in ITO surface for different polarizations [213]. However our results were consistent with the fact that the molecular order of cytochrome c on a bare ITO surface is fairly negligible [208].…”

Section: Measurements Of Electron Transfer Rate With Incident Light Asupporting

confidence: 86%

“…Several studies have been done on the orientation of both reduced and oxidized cytochrome c on various surfaces [207][208][209][210][211] and conditions [212][213][214][215]. Results of electron transfer rate…”

Section: Measurements Of Electron Transfer Rate With Incident Light Amentioning

confidence: 99%

Novel analytical tools for studies in molecular assemblies : I. Electro-active single-mode integrated optical waveguides ; II. Coupled plasmon waveguide resonances.

Xue¹

View full text Add to dashboard Cite

Determination of Anisotropic Optical Constants and Surface Coverage of Molecular Films Using Polarized Visible ATR Spectroscopy. Application to Adsorbed Cytochrome c Films

Cited by 21 publications

References 42 publications

Investigations on the Q and CT Bands of Cytochrome c Submonolayer Adsorbed on an Alumina Surface Using Broadband Spectroscopy with Single-Mode Integrated Optical Waveguides

Investigations on the Q and CT Bands of Cytochrome c Submonolayer Adsorbed on an Alumina Surface Using Broadband Spectroscopy with Single-Mode Integrated Optical Waveguides

Combination of Polarized TIRF and ATR Spectroscopies for Determination of the Second and Fourth Order Parameters of Molecular Orientation in Thin Films and Construction of an Orientation Distribution Based on the Maximum Entropy Method

Novel analytical tools for studies in molecular assemblies : I. Electro-active single-mode integrated optical waveguides ; II. Coupled plasmon waveguide resonances.

Contact Info

Product

Resources

About