Cornelius Krasel krasel at
Sun Aug 9 11:46:30 EST 1998

Arne Mueller <amuelle3 at> wrote:
> Can anyone here explain me in short words the principles of Surface
> Plasmon Resonance? I'm, a biologist working with proteins and DNA on a
> BIAcore, and I've to admit I haven't understood the principles of the
> phenomena. So maybe you can give me a quick introduction - only to know
> what happens in this black box machine ... ;-)

I liked this article:

        author  = {Malini Raghavan and Pamela J. Bjorkman},
        title   = {{BIAcore}: a microchip-based system for analyzing the
                formation of macromolecular complexes.},
        journal = {Structure},
        volume  = 3,
        pages   = {331--333},
        year    = 1995

Now comes the (possibly wrong) layman explanation: the BIAcore machine is
based on the principle of total reflection, i.e. if you reflect a light beam
on a surface at a very small angle, you get what is total reflection (i.e.
virtually no loss of light, a principle that is used to transmit light in
glassfiber). Interestingly, the exact angle of the outgoing light is dependent
on what happens at the reflecting interface. This is due to the evanescent
wave of the beam (if you are not into physics you may imagine that the beam
somehow "senses" what is at the other side of the reflective surface).
If you look at the equation for total reflection (can't do that at the
moment, my physics books are approx. 200 km away) you'll find that the
angle depends on the density (?) of the medium.

Therefore, what you need is a very thin surface (since the evanescent
wave doesn't travel very far into the medium) which, I believe, is made
of gold in the BIAcore apparatus. One side is reflective, the other one
is coated with reactive groups to which you then can covalently couple
one of your interaction partners. If the other partner binds, the
density of the medium changes --> the evanescent wave is influenced -->
the reflection angle changes a tiny little bit --> you get a readout.


/* Cornelius Krasel, U Wuerzburg, Dept. of Pharmacology, Versbacher Str. 9 */
/* D-97078 Wuerzburg, Germany   email: phak004 at  SP4 */
/* "Science is the game we play with God to find out what His rules are."  */

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