From owner-biophys@hgmp.mrc.ac.uk Mon Sep 11 13:05:07 2000 Return-Path: Received: by mercury.hgmp.mrc.ac.uk (Postfix, from userid 110) id 9755917AD2; Mon, 11 Sep 2000 13:05:06 +0100 (BST) Received: by mercury.hgmp.mrc.ac.uk (Postfix, from userid 6024) id 5696817A92; Mon, 11 Sep 2000 13:05:05 +0100 (BST) Received: from niobium.hgmp.mrc.ac.uk (niobium [193.62.192.41]) by mercury.hgmp.mrc.ac.uk (Postfix) with ESMTP id C7EB4415D4 for ; Mon, 11 Sep 2000 13:05:04 +0100 (BST) Received: (from news@localhost) by niobium.hgmp.mrc.ac.uk (8.9.3+Sun/8.8.8) id NAA08884 for biophys-list@hgmp.mrc.ac.uk; Mon, 11 Sep 2000 13:05:04 +0100 (BST) X-Authentication-Warning: niobium.hgmp.mrc.ac.uk: news set sender to using -f From: Juha-Matti I Alakoskela X-Newsgroups: bionet.biophysics Subject: Re: ...sorry Fluorescence DETECTED CD description needed Date: 11 Sep 2000 11:43:07 GMT Organization: University of Helsinki Lines: 45 Message-ID: <8piggb$peq$1@oravannahka.helsinki.fi> References: <8piefr$29$1@newsserver.rrzn.uni-hannover.de> X-Trace: oravannahka.helsinki.fi 968672587 26074 128.214.205.27 (11 Sep 2000 11:43:07 GMT) X-Complaints-To: usenet@news.helsinki.fi User-Agent: tin/1.4.2-20000205 ("Possession") (UNIX) (OSF1/V4.0 (alpha)) To: biophys@hgmp.mrc.ac.uk Sender: owner-biophys@hgmp.mrc.ac.uk Precedence: bulk Gregor Witte wrote: : What exactly means fluorescence detected Circulardichroism? How does this : method work? : Does anyone know a link to a method description (internet) or could give me : a brief description via email? : Thanks a lot Dear Gregor, Though I am not an expert on the field, I think I can help you. As you probably know, in normal CD we measure the difference in absorption by letting the clockwise and counter-clockwise circularly polarized light go through our sample, and determining how much of the each is absorbed by detecting how much of it came through. In fluorescence detected circular dichroism the molecule/chromophore of interest has to be a fluorescent one. Again, the molecule will absorb the clockwise and counter-clockwise circularly polarized light differently. However, instead of measuring how much of the light was absorbed, we measure the emission intensity of the molecule. Since the intensity of the emission is proportional to the amount of light absorbed and since the quantum yield is not dependent on the polarization of the light absorbed, we can measure the circular dichroism of the absorption by exciting our molecule first with light of one polarization, and then with light of the other polarization, and by measuring the emission intensity in both cases. I am not aware of any internet source, but I can give a nice reference: Tinoco I Jr. Mickols W. Maestre MF. Bustamante C. Absorption, scattering, and imaging of biomolecular structures with polarized light. [Review] Annual Review of Biophysics & Biophysical Chemistry. 16:319-49, 1987. Yours Sincerely, Juha-Matti Alakoskela Helsinki Biophysics and Biomembrane Group ........ phone +358 9 191 8236 Department of Medical Chemistry .................. fax +358 9 191 8276 Institute of Biomedicine ............................................... Siltavuorenpenger 10 A ................................................. P.O. Box 8 ............................................................. 00014 University of Helsinki ........................................... Finland ................................................................ .