I can't see the structural details of neurons when I inject my fluorescent dextran. What can I do to improve the detailed structure?
If you want to see the most detailed structure you should use the low molecular weight conjugated dextrans such as the 3,000 MW dextrans.
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Why isn't my fluorescently conjugated dextran signal retained after fixation?
Ensure that the dextran you are using is the fixable form (i.e., contains a primary amine). Dextrans that do not contain a primary amine will not be fixed. Another factor could be that the concentration of the dextran is too low, and the concentration use can be increased up to 10 mg/mL.
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What are the charges of the dextrans?
We do not determine the net charge of the dextran conjugates. The net charge depends on the fluorophore used to label the dextran and the method of preparing the conjugate. We label some dextrans as neutral or anionic based on the fluorophore used, however the net charge of the dextran may not always be the same as the dye. The Alexa Fluor, Cascade Blue, Lucifer Yellow, fluorescein, and Oregon Green dextrans are intrinsically anionic, whereas most of the dextrans labeled with the zwitterionic Rhodamine B, tetramethylrhodamine and Texas Red dyes are essentially neutral.
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What size dextran is best for neuronal tracing?
Dextrans with molecular weights from 3,000 to 70,000 have been used, however the 3,000 and 10,000 MW dextrans are most commonly used for neuronal tracing. The 3,000 MW dextrans are used for more detailed tracing of fine neuronal projections, investigating gap junctions, and diffuse more quickly; while the 10,000 MW dextrans have slower distribution, longer cellular retention, and do not cross gap junctions.
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Do you have a neuronal tracing protocol?
The NeuroTrace BDA-10,000 Neuronal Tracer Kit (Cat. No. N7167) manual has a good protocol for injection procedures and neuronal tracing using the10,000 MW lysine-fixable biotin dextran amine (BDA). This protocol could potentially be applied to other fluorescent dextrans.
Please review Tables 1a and 1b on pages 4 and 5 - https://tools.thermofisher.com/content/sfs/manuals/mp07167.pdf
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