Microtubule Probes

Microtubule probes are useful for direct imaging of the microtubule cytoskeletons in cells, with high sensitivity and selectivity, in both in vivo and in vitro settings.

Products
Background
Literature (1)
Cat. No. Product Name / Activity
2226 Flutax 1
Fluorescent taxol derivative; microtubule stain
6254 Flutax 2
Green fluorescent taxol derivative; binds microtubules
7315 Taxol Janelia Fluor® 526
Green fluorescent taxol derivative; probe for microtubule staining
6267 Taxol Janelia Fluor ® 549
Yellow fluorescent taxol derivative; probe for microtubule staining
6266 Taxol Janelia Fluor® 646
Red fluorescent taxol derivative; probe for microtubule staining; protocol available

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    Microtubules

    Microtubules are found in all eukaryotic cells and are major components of their cytoskeleton. They are hollow cylindrical structures of 20-25 nm in diameter and consist of α- and β-tubulin heterodimers organized into linear protofilaments. They are highly dynamic structures that undergo continual assembly and disassembly in a process driven by GTP hydrolysis. They are polar structures with a fast-growing β-subunits (+) end, and a slow-growing α-subunits (-) end.

    Microtubules are important in many cellular processes. They participate in vital cell functions such as intracellular transport, signalling, proliferation and maintain the cell structure. They also form the mitotic spindle which pull eukaryotic chromosomes apart during cell division.

    Taxol-Based Microtubule Probes

    Fluorescent probes present opportunities for the selective imaging of microtubules within the cell cytoplasm. Tocris offers two categories of fluorescent microtubule probes: Flutax and Taxol Janelia Fluor®, both Taxol (Cat. No. 1097) based molecules.

    Taxol (often referred to as Paclitaxel) is a diterpenoid originally isolated from yew tree bark. Taxol binds to the β-tubulin subunit in the microtubule lumen which promotes and stabilizes its polymerization, blocking the microtubule dynamics necessary for mitotic cellular functions and leading to cell death. Given its antimitotic and cytotoxic action, Taxol has been used for many years as an antitumor drug particularly in breast, prostate, lung, and ovarian cancer treatment.

    The conjugation of fluorescent dyes to Taxol offers a convenient way to visualize microtubule formation and study factors that influence microtubule assembly. It is important to be aware when using these probes that the pharmacological action of Taxol itself remains after conjugation to a fluorescent dye. The stabilization of tubulin polymerization causes cell cycle arrest at the G2/M phase and cell death.

    Flutax Microtubule Probes

    Flutax 1 (Cat. No. 2226) and Flutax 2 (Cat. No. 6254) are probes constituting of Taxol conjugated to the fluorescent dyes fluorescein and Oregon Green 488, respectively. The main difference between the two probes is the pH sensitivity of the dye used. In the physiological pH range, fluorescein is considered highly pH sensitive, whereas Oregon Green 488 is essentially pH insensitive. Both Flutax 1 and Flutax 2 are green fluorescent probes, cell permeable, bright, with similar absorption and emission maxima. They bind selectively to microtubules with high affinity (Ka ≈ 107 M-1, at 37ºC). Their use is compatible with confocal microscopy and flow cytometry.

    Taxol Janelia Fluor® Microtubule Probes

    Taxol Janelia Fluor® probes consist of a Janelia Fluor® dye conjugated to Taxol. They offer significant advantages over spectrally similar dyes in terms of their brightness and photostability. Additionally, Janelia Fluor® dyes are especially well suited to super-resolution microscopy (SRM) techniques.

    Tocris provides three Taxol Janelia Fluor® probes for microtubule staining. These include Taxol Janelia Fluor® 526 (Cat. No. 7315; green), Taxol Janelia Fluor® 549 (Cat. No. 6267; yellow) and Taxol Janelia Fluor® 646 (Cat. No. 6266; red). Both Taxol Janelia Fluor® 549 and 646 are designed with the same chemical linkage position as the Flutax compounds. In contrast, Taxol Janelia Fluor® 526 is conjugated at the 3' N position which has been shown to reduce toxicity.

    Probe Featured Product: Taxol Janelia Fluor® 526

    Taxol Janelia Fluor® 526 (Cat. No. 7315) is a fluorogenic green-emitting microtubule probe. This fluorogenic probe is non-fluorescent until bound to microtubules, which allows researchers to carry out no-wash experiments, with bright, low noise signals, perfect for sensitive or low expression experiments. It enables easy multicolor, multi-labeling microscopy experiments. Taxol Janelia Fluor® 526 is suitable for live-cell imaging in confocal microscopy and super-resolution microscopy techniques including STED (standard 775 nm laser for depletion).

    Spectral data for Taxol Janelia Fluor 526 microtubule Probes Emission Color Green
    λabs 531 nm
    λem 549 nm
    Extinction Coefficient (ε) 118,000 M-1cm-1
    Quantum Yield (φ) 0.87
    Application Confocal microscopy, STED, super-resolution microscopy

    Figure 1: Spectral and photophysical data for Taxol Janelia Fluor® 526

     

    Application of Taxol Janelia Fluor® 646 in COS7 Cells

    Taxol Janelia Fluor® 646 (Cat. No. 6266) has been utilized for microtubule staining in COS7 cells and visualized using confocal microscopy.

    Application of Taxol Janelia Fluor 646 in COS7 Cells

    Figure 2: Application of Taxol Janelia Fluor® 646, dye on COS7 cells; COS7 cells were labeled with 3 µM Taxol Janelia Fluor® 646 for one hour at 37°C. Images were taken on a Leica TCS SP8 Confocal Laser Scanning Microscope.

    All images kindly provided by Prof. Christian Soeller, University of Exeter; acquired by Evelina Lucinskaite, Anna Meletiou and Alexander Clowsley.

    Microtubule Probes Imaging Application

    Cat. No. Product Name / Activity Emission color λEX (nM) λEM (nM) Application
    2226 Flutax 1 Fluorescent taxol derivative; microtubule stain Green 495 520 Flow cytometry, confocal microscopy
    6254 Flutax 2 Green fluorescent taxol derivative; binds microtubules Green 496 526 Flow cytometry, confocal microscopy
    7315 Taxol Janelia Fluor® 526 Green fluorescent taxol derivative; for microtubule staining Green 531 549 Confocal microscopy, SRM, STED
    6267 Taxol Janelia Fluor® 549 Yellow fluorescent taxol derivative; for microtubule staining Yellow 556 575 Flow cytometry confocal microscopy, SRM
    6266 Taxol Janelia Fluor® 646 Red fluorescent taxol derivative; for microtubule staining Red 655 671 Flow cytometry confocal microscopy, SRM

    Table 1: Summary of spectral data and imaging application for Taxol derivative microtubule probes

    References

  • Lillo et al. (2002) Location and properties of the taxol binding center in microtubules: a picosecond laser study with fluorescent toxoids. Biochemistry. 41 12436. PMID: 12369834
  • Diaz et al. (2000) Molecular recognition of taxol by microtubules. Kinetics and thermodynamics of binding of fluorescent taxol derivatives to an exposed site. J.Biol.Chem. 275 26265. PMID: 10818101
  • St. George et al. (2015) Molecular recognition of taxol by microtubules. Kinetics and thermodynamics of binding of fluorescent taxol derivatives to an exposed site. PLoS One. 10 e0129168. PMID: 26052950
  • Zheng et al. (2019) Designing and Testing of Novel Taxanes to Probe the Highly Complex Mechanisms by Which Taxanes Bind to Microtubules and Cause Cytotoxicity to Cancer Cells. ACS Cent. Sci.5 1602. PMID: 31572787
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    Literature for Microtubule Probes

    Tocris offers the following scientific literature for Microtubule Probes to showcase our products. We invite you to request* your copy today!

    *Please note that Tocris will only send literature to established scientific business / institute addresses.


    Fluorescent Probes and Dyes Research Product Guide

    Fluorescent Probes and Dyes Research Product Guide

    This product guide provides a background to the use of Fluorescent Probes and Dyes, as well as a comprehensive list of our

    • Fluorescent Dyes
    • Dyes for Flow Cytometry
    • Fluorescent Probes
    • Anti-fade Reagents
    • Bioluminescent Substrates
    • Fluorogenic Dyes for Light-Up Aptamers
    • Fluorescent Probes for Imaging Bacteria
    • TSA Reagents for Enhancing IHC, ICC & FISH Signals