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Cell Imaging

Cell imaging analysis can use fluorescent dyes, fluorophore labeled molecules or recombinant protein plasmid systems. Recombinant protein labeling systems and  bioluminescent reporter systems are among the most sensitive fluorescence methods for imaging expression, transport, co-localization and degradation in either fixed or living cells. Protein labeling systems offer many advantages. For example, color changes can be easily implemented by using different substrates. Protein labeling systems can involve the use of tag-specific antibodies or antibodies to separate epitopes engineered into a plasmid tag system for detection. Protein labeling systems can be used with non-cell permeable substrates to enable the specific imaging of cell surface targets. This strategy is not possible with bioluminescent recombinant systems.  In living cells, protein labeling substrates can be introduced and followed in cells over time. Two separate cellular targets can also be imaged simultaneously, using protein labeling systems with mutually exclusive, tag specific fluorescent substrates. Cellular functions and structures can be visually detected using methods such as wide-field fluorescence, confocal, time-resolved and fluorescence resonance energy transfer (FRET) microscopy, or cell based high content assays.  Given cellular target characteristics and the array of possible detection methods, choosing an optimal fluorescence system for cellular imaging is key to experimental design.  

SNAP-tag® is a registered trademark of New England Biolabs, Inc.

Cell Imaging includes these areas of focus:

SNAP Companion
SNAP Surface
CLIP Surface
ACP/MCP Surface
ACP/MCP Companion

FAQs for Cell Imaging

Protocols for Cell Imaging

Features of SNAP-tag/CLIP-tag

  • Clone and express once, then use with a variety of substrates
  • Non-toxic to living cells
  • Wide selection of fluorescent substrates
  • Highly specific covalent labeling
  • Simultaneous dual labeling

Applications of SNAP-tag/CLIP-tag

  • Simultaneous dual protein labeling inside live cells
  • Protein localization and translocation
  • Pulse-chase experiments
  • Receptor internalization studies
  • Selective cell surface labeling
  • Protein pull-down assays
  • Protein detection in SDS-PAGE
  • Flow cytometry
  • High throughput binding assays in microtiter plates
  • Biosensor interaction experiments
  • FRET-based binding assays
  • Single molecule labeling
  • Super-resolution microscopy

Advantages of ACP/MCP-tag

  • Small - Expressed tag is only 8 kDa (77aa)
  • Versatile - ACP- and MCP-tagged fusions can be co-expressed and sequentially labeled for two color applications on cell surfaces
  • Specific - Components remain exclusively extracellular, preventing intracellular labeling
  • Precise - Label is covalently bound under biological conditions in a defined position
  • Non-toxic - Substrates are non-toxic to living cells
  • Selection - Choice of substrates available, including 488, 547, 647 nm and biotin

Protein Labeling with SNAP-tag and CLIP-tag

The SNAP- (gold) or CLIP-tag (purple) is fused to the protein of interest (blue). Labeling occurs through covalent attachment to the tag, releasing either a guanine or a cytosine moiety.

Protein Labeling with ACP-tag

ACP-tag (red) fused to the protein of interest (blue) is labeled in the presence of a required synthase.

SNAP-tag®, CLIP-tag™ and ACP/MCP-tag Substrate Selection Chart

NEB offers a large selection of fluorescent labels (substrates) for SNAP-, CLIP-, ACP- and MCP-tag fusion proteins.

Legal Information

This product is covered by one or more patents, trademarks and/or copyrights owned or controlled by New England Biolabs, Inc (NEB).

While NEB develops and validates its products for various applications, the use of this product may require the buyer to obtain additional third party intellectual property rights for certain applications.

For more information about commercial rights, please contact NEB's Global Business Development team at

This product is intended for research purposes only. This product is not intended to be used for therapeutic or diagnostic purposes in humans or animals.

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    Fluorescent Labeling of COS-7 Expressing SNAP-tag Fusion Proteins for Live Cell Imaging

    Watch as Chris Provost, of New England Biolabs, performs fluorescent imaging of live COS-7 cells expressing SNAP-tag® fusion proteins.

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    SNAP-tag Overview Tutorial

    View an interactive tutorial explaining the mechanism of our SNAP-tag® technologies and reagents available for researchers wishing to study the function and localization of proteins in live or fixed cells.