How Do You Follow Biology
That You Cannot See?

DNA replication, nascent protein synthesis and glycosylation are dynamic biological processes. Metabolic labeling and bioorthogonal chemistry allow researchers to introduce chemical handles during these processes and subsequently visualize, detect or enrich the newly labeled biomolecules.

Start With the Biology, Not the Dye

A labeling experiment should not begin by asking which fluorophore to use. The first question should be: What biological process or molecule do you want to follow?

Tracking newly synthesized DNA, nascent proteins, glycans and purified antibodies requires different labeling strategies and different reactive chemistries.

1. Tracking DNA Synthesis

Modified nucleosides such as EdU can be incorporated into newly synthesized DNA during replication.

The alkyne functionality carried by EdU can subsequently react with an azide-functionalized fluorophore or affinity tag through click chemistry.

This provides a convenient strategy for investigating DNA synthesis, cell proliferation and cell-cycle activity.

2. Tracking Nascent Protein Synthesis

Measuring total protein abundance and measuring proteins being synthesized during a defined experimental window are different questions.

Methionine analogs such as AHA and HPG can be incorporated into newly translated proteins, introducing azide or alkyne handles.

Complementary click reagents can then provide fluorescent detection or affinity enrichment of the nascent proteome.

3. Tracking Glycosylation

Azido- and alkynyl-modified sugar analogs can enter cellular glycan biosynthesis pathways and introduce bioorthogonal handles into newly generated glycoconjugates.

Subsequent click chemistry enables visualization or enrichment of metabolically labeled glycans for studies of cell-surface biology, trafficking, immune recognition and cancer biology.

Why Click Chemistry?

Biological samples contain a large number of native reactive groups. A useful labeling reaction must therefore be selective enough to operate without extensively reacting with endogenous cellular chemistry.

Azide-alkyne chemistry provides a bioorthogonal approach in which complementary chemical handles can be selectively connected after metabolic incorporation.

Copper-Catalyzed or Copper-Free?

CuAAC couples azides with terminal alkynes using a copper catalyst and provides efficient conjugation chemistry.

SPAAC uses strained cyclooctynes such as DBCO to react with azides without requiring copper.

Copper-free chemistry can be advantageous when live cells or copper-sensitive biological systems are involved.

Choose the Detection Strategy With the Label

What About Purified Antibodies and Proteins?

Purified biomolecules can be directly conjugated through functional groups such as lysine amines or cysteine thiols.

Vector Laboratories' ChromaLINK® technology uses an amine-reactive biotin reagent containing a UV-traceable chromophore, allowing the degree of biotin incorporation to be measured directly after labeling.

The ChromaLINK Biotin Protein Labeling Kit supports proteins in the 20–200 kDa range and labeling scales from approximately 25 µg to 1 mg per reaction.

Labeling Strategy Checklist

✓ Are you tracking DNA, RNA, protein or glycans?

✓ Do you need to distinguish newly synthesized molecules?

✓ Must labeling occur in living cells?

✓ Is fluorescence imaging required?

✓ Will the sample be analyzed by flow cytometry?

✓ Is affinity enrichment or purification required?

✓ Can the workflow tolerate copper?

✓ Are multiple fluorophores being used?

✓ Could the label alter biomolecule function?

Planning a Metabolic Labeling or Bioconjugation Experiment?

Dana Bioscience can help identify reagents for metabolic labeling, click chemistry, fluorescent labeling, biotinylation and biomolecule conjugation.

Share your target molecule, sample type, desired detection method and downstream application, and we can help evaluate suitable labeling chemistries and research products.