ABSTRACT
Measurements of very slow diffusive processes in membranes, like the diffusion of integral membrane proteins, by fluorescence recovery after photo bleaching (FRAP) are hampered by bleaching of the probe during the read out of the fluorescence recovery. In the limit of long observation time (very slow diffusion as in the case of large membrane proteins), this bleaching may cause errors to the recovery function and thus provides error-prone diffusion coefficients. In this work we present a new approach to a two-dimensional closed form analytical solution of the reaction-diffusion equation, based on the addition of a dissipative term to the conventional diffusion equation. The calculation was done assuming (i) a Gaussian laser beam profile for bleaching the spot and (ii) that the fluorescence intensity profile emerging from the spot can be approximated by a two-dimensional Gaussian. The detection scheme derived from the analytical solution allows for diffusion measurements without the constraint of observation bleaching. Recovery curves of experimental FRAP data obtained under non-negligible read-out bleaching for native membranes (rabbit endoplasmic reticulum) on a planar solid support showed excellent agreement with the analytical solution and allowed the calculation of the lipid diffusion coefficient.
Subject(s)
Cell Membrane/chemistry , Cytochrome P-450 Enzyme System/chemistry , Fluorescence Recovery After Photobleaching/methods , Membrane Fluidity , Membrane Proteins/chemistry , Microsomes, Liver/chemistry , Models, Biological , Models, Chemical , Animals , Cells, Cultured , Computer Simulation , Cytochrome P-450 Enzyme System/analysis , Diffusion , Membrane Proteins/analysis , RabbitsABSTRACT
BACKGROUND: The goal of this study was to assess and compare voice handicap in patients with benign organic and functional dysphonia. PATIENTS AND METHODS: Voice handicap was assessed using a German version of the Voice Handicap Index. A total of 108 German speaking patients, 64 women and 44 men aged 45.3+/-15.1 years with benign organic ( n=69) or functional ( n=39) voice disorders completed the questionnaire immediately after clinical examination and without knowing their individual diagnosis. Fifty individuals without voice complaints and normal voice status, 28 women and 22 men aged 47.1+/-15.5 years, served as controls. RESULTS: Significant differences ( P<0.001) were found between all dysphonic patients and the control group. When comparing dysphonic patients according to their gender and diagnosis group (organic or functional) no significant differences were detected. CONCLUSION: It can no longer be assumed that patients with functional voice disorders over emphasize their disease. The data obtained in this study prove that there are no gender specific differences in the way a voice disorder is experienced. There are also no differences in the way patients with a different language background experience their voice handicap.
