Health & Life Sciences

Example Setup: Fluorescence of Biological Samples

Overview

Fluorescence measurements require a sensitive detector and an effective filter for discriminating between powerful excitation source wavelengths and weak emissions from the sample. For analysis of biological samples such as proteins, the amount of fluorescence can often give the researcher insight into the protein’s conformational states or activity under different biological conditions including changes in temperature, pH and ion concentration.

Fluorescence System Setup

We offer several spectrometers useful for fluorescence, but recommend the high-sensitivity, preconfigured QE Pro-FL for most fluorescence applications. The QE Pro-FL is set to ~350-1100 nm and is configured with a 200 µm slit and variable longpass filter.

In this setup, we use an LLS series UV LED for excitation. Nearly 20 different UV wavelength options are available, starting at 240 nm. The PX-2 pulsed xenon source is also useful for excitation.

Sampling Considerations

For solutions sampling, we use a CUV-ALL-UV 4-way cuvette holder, with the fibers coupled at 90 degrees to each other; 74-MSP mirrored screw plus to improve sensitivity; and two QP600-2-SR solarization-resistant optical fibers. Quartz cuvettes (1 cm pathlength) are used for the sample. Temperature-controlled cuvette holders are also available.

For most fluorescence experiments, you’ll need a filter to discriminate between excitation source wavelengths and spectral emissions from the sample. Our Linear Variable Filters are excellent for shaping the excitation energy from broadband sources. With a narrow-band excitation source such as an LED, a filter may not be necessary.

OceanView software completes the system.

Fluorescence System Components

The setup described here is just one of several options available for fluorescence measurement of solutions. For fluorescence of solids, one would likely select a broadband excitation source and a reflection/backscattering probe in place of the LED-cuvette holder setup described here.

Here are the items in the example setup:

Also Notable

Ocean Optics provides the modular optical sensing solutions and applications know-how to help you solve your measurement problems with a great degree of flexibility. For example, when analyzing proteins, users can take advantage of our QE series spectrometer’s replaceable slit design to perform both fluorescence and absorbance measurements. Similarly, our 4-way cuvette holder can be positioned for both 90 degree (fluorescence) and straight-through (absorbance) measurements. This modular approach is not typically available in traditional lab instrumentation.

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