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Trusted by Leading Research & Pharma Institutions

Fluorescent Protein Labeling Services

Site-specific protein fluorophore conjugation with precision characterization. From antibodies to engineered proteins, we deliver conjugates with optimized labeling efficiency and validated functionality.

50+ Fluorophores
Site-Specific
ESI-MS QC
Learn More

Trusted by leading research and pharmaceutical institutions

Harvard
Pfizer
MIT
Roche
Stanford
Novartis

Why Choose Us

Site-specific conjugation preserves function
50+ fluorophores across spectrum
Multi-platform expertise
Full documentation included

Site-Specific Conjugation

Sortase A, cysteine, disulfide re-bridging

Multi-Platform Expertise

NHS-ester, maleimide, enzyme approaches

Verified Quality

ESI-MS, HPLC, and full documentation

Market CAGR
12.4%
Overview Technology Specifications Workflow Applications FAQ
Service Overview

Expert Protein Fluorophore Conjugation

Our platform combines multiple conjugation chemistries with rigorous quality control to deliver conjugates that meet your exact specifications.

Site-Specific Conjugation

Advanced chemistries including Sortase A transpeptidation and disulfide re-bridging ensure labeling at defined positions, preserving antigen binding and protein function for critical applications.

  • Sortase A C-terminal labeling
  • Engineered cysteine labeling
  • Disulfide re-bridging for antibodies

Multi-Platform Expertise

From NHS-ester lysine labeling to maleimide cysteine chemistry and enzyme-mediated approaches, we match the right method to your protein and downstream application.

  • NHS-ester amine labeling
  • Maleimide thiol chemistry
  • Enzyme-mediated approaches

Extensive Dye Portfolio

50+ fluorophores spanning visible to near-IR spectrum including Alexa Fluor, CyDye, ATTO, and Janelia Fluor series.

Rigorous QC Verification

Every conjugate undergoes ESI-MS and HPLC characterization with DOL optimization for maximum signal-to-noise ratio.

Flexible Options

From single conjugates to multi-site labeling and orthogonal labeling for FRET studies.

Ready to Start Your Project?

Get expert guidance on your labeling strategy and a detailed quote.

Technology Platform

Our Labeling Technologies

Multiple conjugation chemistries to match your protein characteristics and experimental needs.

NHS-Ester Labeling

Primary amine-reactive chemistry targeting lysine residues and N-termini. Fast, reliable, and compatible with most proteins.

General Purpose High-Throughput

Maleimide Thiol Labeling

Cysteine-selective conjugation forming stable thioether bonds. Ideal for site-specific labeling when engineered cysteines are available.

Site-Specific smFRET

Sortase A Transpeptidation

Enzymatic C-terminal labeling using LPXTG recognition motif. Preserves native function while achieving precise site control.

Enzymatic Structural Biology

Quality Control

MS ESI-MS verification
HPLC Purity analysis
UV DOL calculation
COA Certificate of Analysis included

Purification Options

SEC Size-exclusion chromatography
HPLC High-purity separation
PAGE SDS-PAGE verification
Dialysis Buffer exchange
Specifications

Service Specifications

Comprehensive specifications to meet your research requirements.

Parameter Specification
Protein Types IgG antibodies, recombinant proteins, enzymes, peptides
Molecular Weight Range 12 kDa - 180 kDa
Sample Quantity 100 μg - 100 mg per project
Available Fluorophores 50+ dyes (AF488, AF555, AF647, Cy3, Cy5, ATTO, Janelia Fluor)
Degree of Labeling (DOL) Optimized per application (typically 1-8 dyes per protein)
Quality Control ESI-MS, HPLC, UV-Vis spectroscopy, SDS-PAGE
Purification Method Size-exclusion chromatography, HPLC
Documentation Certificate of Analysis, MS report, DOL verification
Workflow

Streamlined Process from Design to Delivery

Our proven 4-step workflow ensures quality and efficiency at every stage.

1

Consultation

Share protein details and assay requirements

2

Conjugation

Optimized chemistry under QC conditions

3

Purification

Free dye removal and characterization

4

QC & Delivery

Full characterization and documentation

Applications

Diverse Applications Across Biotechnology

Our labeling services support research and development in multiple fields.

Fluorescence Microscopy & Imaging

High-quality conjugates for confocal, super-resolution, and live-cell imaging applications. Site-specific labeling ensures preserved antigen binding and optimal signal-to-noise ratio.

  • AF488, AF555, AF594, AF647 for confocal
  • Janelia Fluor for STED and SIM
  • Preserved antigen binding affinity
  • Low background, high specificity
50+
Available fluorophores

Flow Cytometry & FACS

Optimized conjugates for multi-color flow cytometry panels with controlled DOL for maximum brightness and minimal aggregation.

  • PE, APC, Pacific Blue for multi-color panels
  • Optimized DOL for maximum brightness
  • Low background in biological samples
  • Batch-to-batch consistency
12+
Color panels validated

Structural Biology & Biophysics

Site-specific labeling for FRET studies, single-molecule experiments, and structural biology applications requiring precise donor-acceptor positioning.

  • ATTO dyes and FRET pairs
  • Defined donor-acceptor positioning
  • smFRET validated conjugates
  • Sortase A for C-terminal labeling
1:1
DOL for structural studies
Testimonials

What Our Clients Say

Trusted by researchers worldwide for quality and reliability.

"The site-specific Sortase labeling preserved our antibody binding affinity while giving us the precise labeling needed for single-molecule studies. Results exceeded expectations."

SC
Senior Scientist
Structural Biology Research Institution

"We've switched all our antibody conjugates to this service. The batch-to-batch consistency and detailed QC reports make a real difference in our multi-center clinical trials."

RD
Research Director
Pharmaceutical Development Company

"Technical support helped optimize the DOL for our flow cytometry panels. The conjugates give excellent separation in 12-color experiments. Highly recommended."

PS
Principal Scientist
Immunology Diagnostics Laboratory
Scientific Literature

Scientific Foundation

Our platform is backed by peer-reviewed research.

89 Citations

Bioorthogonal site-selective conjugation of fluorescent dyes to antibodies

P. Grossenbacher, M. C. Essers, J. Moser, S. A. Singer, et al. RSC Advances. 2022.

Disulfide re-bridging strategy for site-selective fluorescent dye labeling of IgG1 antibodies without loss of antibody function.

View DOI
142 Citations

Flavin-tag: A Facile Method for Site-Specific Labeling of Proteins with a Flavin Fluorophore

Y. Tong, M. Lee, J. Drenth, M. W. Fraaije, et al. Bioconjugate Chemistry. 2021.

Bacterial flavin transferase enables enzyme-mediated site-specific protein labeling with a 7-amino-acid flavin tag.

View DOI
35 Citations

Site-Specific C-Terminal Fluorescent Labeling of Tau Protein

L. Bryan, S. Awasthi, Y. Li, P. N. Nirmalraj, et al. ACS Omega. 2022.

Sortase A-mediated C-terminal labeling of Tau protein with Alexa Fluor 647 for Alzheimer's disease research.

View DOI
28 Citations

Parallel microscale protein labeling with precise control over average degree of labeling

Abbott Laboratory Research Team. Scientific Reports. 2023.

Copper-free click chemistry enables precise aDoL control for microscale protein labeling applications.

View DOI
67 Citations

Chemical tags and beyond: Live-cell protein labeling technologies for modern optical imaging

Research Team. Small Methods. 2023.

Comprehensive review of HaloTag, SNAP-tag, TMP-tag, and unnatural amino acid systems for super-resolution imaging.

View DOI
FAQ

Frequently Asked Questions

Find answers to common questions about our service.

DOL depends on your downstream application. For immunofluorescence, DOL of 2-4 typically provides optimal signal-to-noise. For flow cytometry, DOL of 4-8 maximizes brightness. For structural biology and FRET studies, site-specific labeling with DOL of 1-2 is preferred to minimize labeling heterogeneity. Our team will recommend the optimal DOL based on your specific requirements.
Most purified proteins with available lysine or cysteine residues are suitable. We recommend 1-10 mg of purified protein at greater than 90% purity, in buffers without primary amines (avoid Tris, glycine) or reducing agents. For challenging proteins, our technical team will evaluate compatibility during consultation.
Every conjugate undergoes comprehensive QC: ESI-MS to verify mass shift and labeling stoichiometry, HPLC and SEC to confirm purity and detect aggregates, UV-Vis spectroscopy for concentration and DOL calculation, and SDS-PAGE to verify conjugate integrity. Full documentation is provided in the Certificate of Analysis.
Yes. We offer multiple site-specific approaches: Sortase A transpeptidation for C-terminal labeling (requires LPXTG motif), engineered cysteine labeling for precise thiol positioning, and disulfide re-bridging for IgG antibodies. Share your protein sequence and requirements for a tailored recommendation.
We offer 50+ fluorophores spanning the spectrum from UV to near-IR: Alexa Fluor series (350, 488, 555, 594, 647, 680), CyDye series (Cy3, Cy5, Cy7), ATTO dyes, Janelia Fluor dyes, and tandem dyes (PE, APC conjugates). Custom dye requests can be accommodated for specific project needs.
Ship purified protein on dry ice or blue ice to maintain cold chain. Include buffer composition, concentration, and any specific handling instructions. For fragile proteins, consider express shipping. We accept samples Monday through Friday; weekend deliveries should be coordinated in advance.

Ready to Start Your Project?

Get a customized quote for your Fluorescent Labeling of Proteins Service project. Our experts will respond within 24 hours.

No obligation
24h response
Expert consultation

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· Site-Specific Protein Labeling Service

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