Design for Supported Planar Waveguides for Obtaining Mid-IR Evanescent-Wave Absorption Spectra from Biomembranes of Individual Cells

$29.00 plus tax (Refund Policy)

Buy Article:


We have been developing miniature planar Ge waveguides to detect mid-IR evanescent-wave absorption spectra from the cell membranes of individual intact frog eggs, 1.5-mm in diameter, from Xenopus laevis, with the aim of detecting and analyzing transient conformational changes of voltage-gated ion channel proteins in the membrane. Here we use waveguide optical theory to calculate optimal dimensions for a germanium waveguide to be used as a multiple-internal-reflection ATR element for this purpose. We assume that light from a standard broad-band IR source is coupled efficiently into and out of a planar Ge waveguide, and then onto a small-area MCT detector, by using an IR microscope with a highnumerical-aperture objective. To increase the coupling efficiency even further, we assume that we can fabricate the waveguide with a gradual 7-fold-tapering to the tiny dimensions needed in the sensing region. Then, assuming that ~ 107 ion channel proteins in an occyte can be made to contact an area of a planar Ge waveguide up to ~ 200 mu m in diameter, we calculate that voltage-gated structural changes in these channel proteins should produce absorbance change signals of ~ 10-6 if the waveguide sensor thickness is set near the optimal thickness of ~ 1 mu m and the sensor region length is limited to 100 mu m. If such a sensor can be fabricated, we calculate that detection of the predicted voltage-gated absorbance changes with a commercial FT-IR microscope should be possible after ~ 20 min of signal averaging.


Document Type: Research Article


Publication date: April 1, 1997

More about this publication?
Related content



Share Content

Access Key

Free Content
Free content
New Content
New content
Open Access Content
Open access content
Subscribed Content
Subscribed content
Free Trial Content
Free trial content
Cookie Policy
Cookie Policy
ingentaconnect website makes use of cookies so as to keep track of data that you have filled in. I am Happy with this Find out more