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Figure 2 | EURASIP Journal on Bioinformatics and Systems Biology

Figure 2

From: In vitro detection of adrenocorticotropic hormone levels by fluorescence correlation spectroscopy immunoassay for mathematical modeling of glucocorticoid-mediated feedback mechanisms

Figure 2

FCS principle and instrumentation. In the confocal setup (a) of a single-color FCS, the excitation Argon-laser light is directed by a dichroic mirror into a water immersion objective that focuses the light in a calibrated volume inside the sample (a). Changes in diffusion behavior of fluorescent molecules entering and leaving the detection volume are monitored (a). Thereby, each fluorescence signal is collected through the same objective and focused onto a pinhole, so that the laser beam waist inside the sample is imaged onto the pinhole aperture. The conjugation of the objective and the pinhole creates a spatial filter, which efficiently cuts the sampling volume to a diffraction limited size. After the pinhole, the fluorescence signal is collected directly by an Avalanche photodiode and processed into an autocorrelation function G(τ) to calculate single molecule concentrations.

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