Live-cell imaging (SiR and SIR700) probes developed by Spirochrome are cell-permeable compounds which stain microtubules (SiR-Tubulin), F-actin (SiR-Actin), Lysosomes (SiR-Lysosome) and chromosomal DNA (SiR-DNA) in living cells.
Cytoskeleton is excited to introduce the next generation of Spirochrome’s live cell imaging probes - the SPY™ probes. SPY™ probes improve upon the SiR live cell imaging technology while also expanding the fluorophore labeling options for the study of F-actin, microtubules, and DNA in living cells.
Live cell F-actin imaging 2.0 with SPY650-FastAct™: This new probe is a unique fluorescent live cell actin probe that labels very dynamic actin filaments. Click Here to Learn More
Additional Spirochrome Probes and Tools:
Flipper-TR® is a live cell fluorescent membrane tension probe that simplifies the methodology for investigating changes in membrane tension when used in combination with standard fluorescence lifetime measurements.
Benzylguanine substrates enables investigators to label their SNAP-tagged-fused-protein of interest with these fluorescent dyes; thus, harnessing the exceptional qualities of the SPY™ and SiR probes to enhance their investigation and understanding of their target protein.
Click on the links below to learn more about these cutting-edge probes and tools for live cell imaging.
Cytoskeleton, Inc. is the exclusive provider of Spirochrome, Ltd. products in North America.
Spirochrome technology is based on the proprietary fluorophore silicon rhodamine (SiR). SiR is a bright and photostable rhodamine-like dye. Its key features are its cell permeability, fluorogenic character and compatibility with super-resolution microscopy The fluorescence excitation and emission of SiR are in the far-red, reducing phototoxicity in live-cell imaging experiments. SiR is compatible with most microscopes as it can be used with standard Cy5 settings. The combination of all these properties set SiR-based probes apart from other fluorescent probes. Read more in this Nature Chemistry paper about the properties of SiR.
Fluorogenic probes for live-cell imaging of the cytoskeleton
SiR-actin and SiR-tubulin were recently introduced in a landmark paper published in Nature Methods. The probes combine minimal cytotoxicity with excellent brightness for fluorescence imaging of actin and tubulin. Combined with super-resolution microscopy, SiR-actin and SiR-tubulin permit live-cell imaging of the cytoskeleton with unprecedented resolution.
SiR-actin and SiR-tubulin can be used without transfection and without washing steps. An experiment that highlights these features is the use of SiR-actin to stain the actin fibers of erythrocytes by simply adding SiR-actin to whole blood. Furthermore, their far-red excitation and emission spectra make them compatible with genetically encoded reporters.
Spirochrome's live cell probes have been cited hundreds of times over the past several years. SiR-Actin citations are described here. More individual product citations are listed on each product page.
|Perez, Carolina Gomis et al.||Rapid propagation of membrane tension at retinal bipolar neuron presynaptic terminals||Science Advances||2022||ISSN 2375-2548|
|Bauerly, Elisabeth et al.||Impact of cilia-related genes on mitochondrial dynamics during Drosophila spermatogenesis||Developmental Biology||2022||ISSN 0012--1606|
|Efremov, Yuri M. et al.||3D nanomechanical mapping of subcellular and sub-nuclear structures of living cells by multi-harmonic AFM with long-tip microcantilevers||Scientific Reports 2022 12:1||2022||ISSN 2045--2322|
|Salomaa, Siiri I. et al.||SHANK3 conformation regulates direct actin binding and crosstalk with Rap1 signaling||Current Biology||2021||ISSN 1879-0445|
|Eysert, Fanny et al.||Alzheimer’s genetic risk factor FERMT2 (Kindlin-2) controls axonal growth and synaptic plasticity in an APP-dependent manner||Molecular Psychiatry||2021||ISSN 1476-5578|
|Warmt, Enrico et al.||Differences in cortical contractile properties between healthy epithelial and cancerous mesenchymal breast cells||New Journal of Physics||2021||ISSN 1367-2630|
|Wurzer, Hannah et al.||Intrinsic Resistance of Chronic Lymphocytic Leukemia Cells to NK Cell-Mediated Lysis Can Be Overcome In Vitro by Pharmacological Inhibition of Cdc42-Induced Actin Cytoskeleton Remodeling||Frontiers in Immunology||2021||ISSN 1664-3224|
|Jewett, Cayla E. et al.||RAB19 Directs Cortical Remodeling and Membrane Growth for Primary Ciliogenesis||Developmental Cell||2021||ISSN 1878-1551|
|Titelbaum, Moran et al.||Ezh2 harnesses the intranuclear actin cytoskeleton to remodel chromatin in differentiating Th cells||iScience||2021||ISSN 2589-0042|
|Scherer, Katharina M. et al.||A fluorescent reporter system enables spatiotemporal analysis of host cell modification during herpes simplex virus-1 replication||2021||PMID 33380421|
|Merlini, Mario et al.||Microglial Gi-dependent dynamics regulate brain network hyperexcitability||Nature Neuroscience||2021||ISSN 1546-1726|
|Tabdanov, Erdem D. et al.||Engineering T cells to enhance 3D migration through structurally and mechanically complex tumor microenvironments||Nature Communications||2021||ISSN 2041-1723|
|Morandell, Jasmin et al.||Cul3 regulates cytoskeleton protein homeostasis and cell migration during a critical window of brain development||Nature Communications||2021||ISSN 2041-1723|
|Choi, Yong Won et al.||Senescent Tumor Cells Build a Cytokine Shield in Colorectal Cancer||Advanced Science||2021||ISSN 2198-3844|
|Raza, Sayyid et al.||SOX9 is required for kidney fibrosis and activates NAV3 to drive renal myofibroblast function||Science Signaling||2021||ISSN 1937-9145|
|Damenti, Martina et al.||STED and parallelized RESOLFT optical nanoscopy of the tubular endoplasmic reticulum and its mitochondrial contacts in neuronal cells||Neurobiology of Disease||2021||ISSN 1095-953X|
|Vignaud, Timothée et al.||Stress fibres are embedded in a contractile cortical network||Nature Materials||2021||ISSN 1476-4660|
|Wallis, Samuel S. et al.||The ESCRT machinery counteracts Nesprin-2G-mediated mechanical forces during nuclear envelope repair||Developmental Cell||2021||ISSN 1878-1551|
|Bock, Fabian et al.||Rac1 promotes kidney collecting duct integrity by limiting actomyosin activity||Journal of Cell Biology||2021||ISSN 1540-8140|
|Monster, Jooske L. et al.||An asymmetric junctional mechanoresponse coordinates mitotic rounding with epithelial integrity||Journal of Cell Biology||2021||ISSN 1540-8140|
|Fläschner, Gotthold et al.||Rheology of rounded mammalian cells over continuous high-frequencies||Nature Communications 2021 12:1||2021||ISSN 2041--1723|
|Linklater, Erik S. et al.||Rab40–cullin5 complex regulates eplin and actin cytoskeleton dynamics during cell migration||Journal of Cell Biology||2021||ISSN 1540-8140|
|Ordas, Laura et al.||Mechanical Control of Cell Migration by the Metastasis Suppressor Tetraspanin CD82/KAI1||Cells 2021, Vol. 10, Page 1545||2021||ISSN 2073--4409|
|Jin, Jianfeng et al.||Pulsating fluid flow affects pre-osteoblast behavior and osteogenic differentiation through production of soluble factors||Physiological Reports||2021||ISSN 2051--817X|
|Kalargyrou, Aikaterini A et al.||Nanotube‐like processes facilitate material transfer between photoreceptors||EMBO reports||2021||ISSN 1469--221X|
|Tsuchiya, Kenta et al.||Ran-GTP Is Non-essential to Activate NuMA for Mitotic Spindle-Pole Focusing but Dynamically Polarizes HURP Near Chromosomes||Current Biology||2021||ISSN 1879-0445|
|Kozawa, Kei et al.||The CD44/COL17A1 pathway promotes the formation of multilayered, transformed epithelia||Current Biology||2021||ISSN 0960--9822|
|Eggers, Nikolas et al.||Cell-free genomics reveal intrinsic, cooperative and competitive determinants of chromatin interactions||Nucleic Acids Research||2021||ISSN 0305--1048|
|Uhl, Bernd et al.||uPA-PAI-1 heteromerization promotes breast cancer progression by attracting tumorigenic neutrophils||EMBO Molecular Medicine||2021||ISSN 1757--4684|
|Girardi, Francesco et al.||TGFβ signaling curbs cell fusion and muscle regeneration||Nature Communications 2021 12:1||2021||ISSN 2041--1723|
|Bain, Judith M. et al.||Immune cells fold and damage fungal hyphae||Proceedings of the National Academy of Sciences of the United States of America||2021||ISSN 1091-6490|
|Sala, Federico et al.||Rapid Prototyping of 3D Biochips for Cell Motility Studies Using Two-Photon Polymerization||Frontiers in Bioengineering and Biotechnology||2021||ISSN 2296-4185|
|Rafati, Yousef et al.||Effect of microtubule resonant frequencies on neuronal cells||https://doi.org/10.1117/12.2546569||2020||Article Link|
|Liu, Jiahao et al.||Deep learning–enhanced fluorescence microscopy via degeneration decoupling||Optics Express, Vol. 28, Issue 10, pp. 14859-14873||2020||ISSN 1094--4087|
|Pourcel, Lucille et al.||Influence of cytoskeleton organization on recombinant protein expression by CHO cells||Biotechnology and Bioengineering||2020||ISSN 1097-0290|
|Bouzhir, Latifa et al.||Generation and quantitative characterization of functional and polarized biliary epithelial cysts||Journal of Visualized Experiments||2020||ISSN 1940-087X|
|Pal, Debadrita et al.||Rac and Arp2/3-Nucleated Actin Networks Antagonize Rho During Mitotic and Meiotic Cleavages||Frontiers in Cell and Developmental Biology||2020||ISSN 2296-634X|
|De Faveri, Francesca et al.||LAP-like non-canonical autophagy and evolution of endocytic vacuoles in pancreatic acinar cells||Autophagy||2020||ISSN 1554-8635|
|Takeuchi, Yasuto et al.||Calcium Wave Promotes Cell Extrusion||Current Biology||2020||ISSN 0960-9822|
|Logan, Gregory et al.||Comparative analysis of taxol-derived fluorescent probes to assess microtubule networks in a complex live three-dimensional tissue||Cytoskeleton||2020||ISSN 1949--3592|
|Valenzuela, José Ignacio et al.||Localized Intercellular Transfer of Ephrin-As by Trans-endocytosis Enables Long-Term Signaling||Developmental Cell||2020||ISSN 1878-1551|
|Reimer, Dorothea et al.||B Cell Speed and B-FDC Contacts in Germinal Centers Determine Plasma Cell Output via Swiprosin-1/EFhd2||Cell Reports||2020||ISSN 2211-1247|
|Stiff, Tom et al.||Prophase-Specific Perinuclear Actin Coordinates Centrosome Separation and Positioning to Ensure Accurate Chromosome Segregation||Cell Reports||2020||ISSN 2211-1247|
|Schoenenberger, Angelina D. et al.||Macromechanics and polycaprolactone fiber organization drive macrophage polarization and regulate inflammatory activation of tendon in vitro and in vivo||Biomaterials||2020||ISSN 1878-5905|
|Kumari, Archana et al.||Structural insights into actin filament recognition by commonly used cellular actin markers||The EMBO Journal||2020||ISSN 0261--4189|
|Domart, Florelle et al.||Correlating sted and synchrotron xrf nano-imaging unveils cosegregation of metals and cytoskeleton proteins in dendrites||eLife||2020||ISSN 2050-084X|
|Tamborino, Giulia et al.||Cellular dosimetry of [177Lu]Lu-DOTA-[Tyr3]octreotate radionuclide therapy: the impact of modeling assumptions on the correlation with in vitro cytotoxicity||EJNMMI Physics||2020||ISSN 2197-7364|
|Ueki, Hiroshi et al.||Multicolor two-photon imaging of in vivo cellular pathophysiology upon influenza virus infection using the two-photon IMPRESS||Nature Protocols||2020||ISSN 1754--2189|
|Maraspini, Riccardo et al.||Optimization of 2D and 3D cell culture to study membrane organization with STED microscopy||Journal of Physics D: Applied Physics||2020||ISSN 1361-6463|
|Burger, Joyce et al.||Fibulin-4 deficiency differentially affects cytoskeleton structure and dynamics as well as TGFβ signaling||Cellular Signalling||2019||ISSN 1873-3913|
|Tomba, Caterina et al.||Laser-Assisted Strain Engineering of Thin Elastomer Films to Form Variable Wavy Substrates for Cell Culture||Small||2019||ISSN 1613-6829|
|Balta, Emre et al.||Spatial oxidation of L-plastin downmodulates actin-based functions of tumor cells||Nature Communications||2019||ISSN 2041-1723|
|Nagaraja, Surya et al.||Histone Variant and Cell Context Determine H3K27M Reprogramming of the Enhancer Landscape and Oncogenic State||Molecular Cell||2019||ISSN 1097-4164|
|Tsygankova, Oxana M. et al.||A unique role for clathrin light chain A in cell spreading and migration||Journal of Cell Science||2019||ISSN 1477-9137|
|Roldán, Adrian Saul Jimenez et al.||3,3′-Thiodipropanol As a Versatile Refractive Index-Matching Mounting Medium for Fluorescence Microscopy||Biomedical Optics Express||2019||ISSN 2156--7085|
|Vestre, Katharina et al.||Rab6 regulates cell migration and invasion by recruiting Cdc42 and modulating its activity||Cellular and Molecular Life Sciences||2019||ISSN 1420-9071|
|Maechler, Florian A. et al.||Curvature-dependent constraints drive remodeling of epithelia||Journal of Cell Science||2019||ISSN 1477-9137|
|Hu, Junyan et al.||Distinct roles of two myosins in C. Elegans spermatid differentiation||PLoS Biology||2019||ISSN 1545-7885|
|Janel, Sébastien et al.||Stiffness tomography of eukaryotic intracellular compartments by atomic force microscopy||Nanoscale||2019||ISSN 2040-3372|
|Hetmanski, Joseph H.R. et al.||Membrane Tension Orchestrates Rear Retraction in Matrix-Directed Cell Migration||Developmental Cell||2019||ISSN 1878-1551|
|Lickert, Sebastian et al.||Morphometric analysis of spread platelets identifies integrin αiIbβ3-specific contractile phenotype||Scientific Reports||2018||ISSN 2045-2322|
|Kschonsak, Yvonne T. et al.||Activated ezrin controls MISP levels to ensure correct NuMA polarization and spindle orientation||Journal of Cell Science||2018||ISSN 1477-9137|
|Kahn, Olga I. et al.||APC2 controls dendrite development by promoting microtubule dynamics||Nature Communications||2018||ISSN 2041-1723|
|Nozawa, Satoshi et al.||Osteoblastic heparan sulfate regulates osteoprotegerin function and bone mass||JCI insight||2018||ISSN 2379-3708|
|Neubert, Elsa et al.||Chromatin swelling drives neutrophil extracellular trap release||Nature Communications||2018||ISSN 2041-1723|
|Schoenenberger, Angelina D. et al.||Substrate fiber alignment mediates tendon cell response to inflammatory signaling||Acta Biomaterialia||2018||ISSN 1878-7568|
|Okumura, Masako et al.||Dynein–dynactin–NuMA clusters generate cortical spindle-pulling forces as a multiarm ensemble||eLife||2018||ISSN 2050-084X|
|Magliocca, Valentina et al.||Identifying the dynamics of actin and tubulin polymerization in iPSCs and in iPSC-derived neurons||Oncotarget||2017||ISSN 1949-2553|
|Zhao, Miao et al.||Identification of the PAK4 interactome reveals PAK4 phosphorylation of N-WASP and promotion of Arp2/3-dependent actin polymerization||Oncotarget||2017||ISSN 1949-2553|
|Petrini, Stefania et al.||Aged induced pluripotent stem cell (iPSCs) as a new cellular model for studying premature aging||Aging||2017||ISSN 1945-4589|
|Leite, Sérgio Carvalho et al.||The Actin-Binding Protein α-Adducin Is Required for Maintaining Axon Diameter||Cell Reports||2016||ISSN 2211--1247|
|D'Este, Elisa et al.||Subcortical cytoskeleton periodicity throughout the nervous system||Scientific Reports||2016||ISSN 2045-2322|
|Lukinavičius, Gražvydas et al.||Fluorogenic probes for live-cell imaging of the cytoskeleton||Nature Methods||2014||ISSN 1548-7105|
“Fluorogenic probes for live-cell imaging of the cytoskeleton”; G. Lukinavičius, L.Reymond, E. D’Este, A. Masharina, F. Göttfert, H. Ta, A. Güther, M. Fournier, S. Rizzo, H. Waldmann, C. Blaukopf, C. Sommer, D. W. Gerlich, H.-D. Arndt, S. W. Hell & K. Johnsson; Nature Methods 11, 731–733, 2014.
“STED Nanoscopy Reveals the Ubiquity of Subcortical Cytoskeleton Periodicity in Living Neurons”; E. D’Este, D. Kamin, F. Göttfert, A. El-Hady, S. W. Hell; Cell Reports , Volume 10 , Issue 8 , 1246 – 1251, 2015.
“A near-infrared fluorophore for live-cell super-resolution microscopy of cellular proteins”; G. Lukinavičius, K. Umezawa, N. Olivier, A. Honigmann, G. Yang, T. Plass, V. Mueller, L. Reymond, I. R. Corrêa Jr, Z. Luo, C. Schultz, E. A. Lemke, P. Heppenstall, C. Eggeling, S. Manley & K. Johnsson; Nature Chemistry 5, 132–139, 2013.
“Dynamic actin filaments control the mechanical behavior of the human red blood cell membrane”; D. S. Gokhin, R. B. Nowak, J. A. Khoory, A. de la Piedra, I. C. Ghiran and V. M. Fowler; Mol. Biol. Cell; February 25, 2015.
“A cleavable cytolysin-neuropeptide Y bioconjugate enables specific drug delivery and demonstrates intracellular mode of action”; V. M. Ahrens, K. B. Kostelnik, R. Rennert, D. Böhme, S. Kalkhof, D. Kosel, L. Weber, M. von Bergen and A. G. Beck-Sickinger; J. Control. Release; 209:170-178, 2015.
“Red Si–rhodamine drug conjugates enable imaging in GFP cells”; E. Kim, K. S. Yang, R. J. Giedt and R. Weissleder; Chem. Commun., 50, 4504-4507, 2014.
“A marginal band of microtubules transports and organizes mitochondria in retinal bipolar synaptic terminals”; M. Graffe, D. Zenisek, and J. Taraska; J. Gen Physiol. Vol. 146 No.1: 109-117, 2015.
“A Bright Dye for Live-Cell STED Microscopy”; S. Pitsch, I. Köster.
Q1. What is STED microscopy and how does it work?
A1. STED microscopy stands for Stimulated Emission Depletion microscopy. It is one type of super resolution microscopy which allows the capture of images with a higher resolution than conventional light microscopy which is constrained by diffraction of light. STED uses 2 laser pulses, one is the excitation pulse which excites the fluorophore, causing it to fluoresce. The second pulse, referred to as the STED pulse, de-excites the fluorophore via stimulated emission in an area surrounding a central focal spot that is not de-excited and thus continues to fluoresce. This is accomplished by focusing the STED pulse into a ring shape, a so-called donut, where the center focal spot is devoid of the STED laser pulse, conferring high resolution to the fluorescent area (Fig. 1; see Ref. 1 for more details on STED microscopy).
Figure 1. STED microscopic image of microtubules labeled with SiR-tubulin in human primary dermal fibroblasts.
Q2. Why is the SiR actin (or tubulin) probe good for STED microscopy?
A2. STED microscopy offers the ability to study cellular details on a nanometermolar scale in vivo. To take advantage of this super resolution microscopy, one must be able to select with high specificity the area to be examined using fluorescent probes. In addition, the fluorescent probes must be bright, photostable, exhibit no or little phototoxicity, be excited and emit in the far red spectrum. In addition, if the probe is to be used for live cell imaging (thus avoiding fixation artifacts that occur when cells are fixed), high cell permeability is necessary. The SiR actin and tubulin probes fulfill all of these requirements. In short, the combination of STED and SiR probes allows for unparalleled fluorescent visualization of subcellular actin and tubulin/microtubule structures and their physical characterization in living cells, (see Fig. 2 and Ref. 2).
Figure 2. STED images of cultured rat hippocampal neurons stained with SiR-actin. Bottom image is a close-up view of part of the top image to clearly visualize actin rings (stripes) with 180 nm periodicity. Courtesy Of Elisa D'Este, MPI Biophysical Chemistry, Göttingen.
Q3. What are the filter sets for these probes?
A3. The SiR actin and tubulin probes are visualized with standard Cy5 filters. Optimal excitation is 650 nm and emission is 670 nm. We recommend filters with an excitation of 630 + 20 nm and an emission of 680 + 20 nm (Fig. 3).
Q4. Why do the SiR probes have a low background compared to other fluorophores?
A4. SiR probes are excited by and emit light in the near infrared/far red spectral range, thus avoiding the use of shorter wavelengths such as blue and green light that typically autofluoresce, causing higher background signals. SiR-coupled probes possess two physical states: 1. a non-fluorescent, closed off-state (spirolactone) and 2. an open, highly fluorescent on-state (zwitterion). The binding of the probe to its ligand target favors the highly fluorescent open state while the free unbound probe exists in the closed, non-fluorescent state (Fig. 4). The fluorescence amplification is 100-fold from the unbound to bound state. This results in a highly sensitive biosensor in which the majority of fluorescence occurs only in the bound state (see Refs. 3 and 4).
Figure 4. SiR derivatives exist in equilibrium between the fluorescent zwitterionic (open) form (left structure) and the non-fluorescent spiro (closed) form (right structure).
Q5: Are the SiR probes stable at room temperature?
A5: Yes, the probes are stable at room temperature for a few days. However, it strongly depends on the probe and the solvent. Thus, it is recommended to store all of the probes or solutions at –20°C.
Q6: Are SiR-actin and SiR-tubulin toxic to cells?
A6: Yes, above a certain threshold both probes show some effect on cell proliferation and altered actin or microtubule dynamics. However, the probes are orders of magnitude less toxic than their parent drug. In HeLa cells, neither actin nor microtubule dynamics were altered at concentrations below 100 nM. At this concentration, SiR probes efficiently label microtubules and F-actin, allowing for the capture of high signal to noise images.
Q7: Do the probes work on fixed cells?
A7: SiR-actin probes can be used with PFA-fixed cells. SiR-actin labels F-actin in PFA-fixed cells as efficiently as phalloidin derivatives. SiR-tubulin labels microtubules only in ethyleneglycol-bis-succinimidyl-succinate (EGS)-fixed cells. However, a selective labeling of centrosomal microtubules of PFA-fixed cells was observed. SiR-actin and SiR-tubulin are not suitable for methanol-fixed cells.
Q8: Is it possible to image SiR-probes by STORM?
A8: No—under the very high light intensities typically used in STORM imaging, a phototoxic effect is observed on live cells.
Q9: Which organisms and tissues are stained by SiR-probes?
A9: This list describes only cell lines, tissues, or organisms that have been reported to work. Omission of a cell line, tissue, or organism does not mean that the SiR-probes will not work with the specific cells, tissues, or organisms.
Homo sapiens: U2OS, fibroblasts, HeLa, HUVEC, MCF-10A, HCT-116, A549, erythrocytes
Mus musculus: C2C12, IA32, skeletal muscle, primary cardiomyocyte, primary oocyte
Rattus norvegicus: primary hippocampal neurons, primary cortical neurons, NRK
Cercopithecus aethiops: COS-7
Mesocricetus auratus: BHK
Drosophila melanogaster: Notum epithelium, S2
Didelphis marsupialis: OK cells
Q10. Do SiR-probes work in 3D cell cultures?
A10: Yes, the probes are able to stain cells in a 3D growth environment.
Q11: What are the correction factors CF260 and CF280 for the SiR fluorophore?
A11: CF260 = 0.116 and CF280 = 0.147
1. Hell S.W. and Wichmann J. 1994. Breaking the diffraction resolution limit by stimulated emission: stimulated-emission-depletion fluorescence microscopy. Opt. Lett. 19, 780-782.
2. D’Este E. et al. 2015. STED nanoscopy reveals the ubiquity of subcortical cytoskeleton periodicity in living neurons. Cell Rep. 10, 1246-1251.
3. Lukinavicius G. et al. 2013. A near-infrared fluorophore for live-cell super-resolution microscopy of cellular proteins. Nat. Chem. 5, 132-139.
4. Lukinavicius G. et al. 2014. Fluorogenic probes for live-cell imaging of the cytoskeleton. Nature Methods. 11, 731-733.
ER Flipper-TR Kit, a probe for measuring plasma-membrane tension.
Lyso Flipper-TR Kit, a probe for measuring plasma-membrane tension.
Mito Flipper-TR Kit, a probe for measuring plasma-membrane tension.