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Dansyl-L-proline is a fluorescent dansyl derivative of L-proline. The dimethylaminonaphthalene sulfonyl group provides the fluorophore, while the proline carboxyl group remains part of the molecule. Its strongest research identity is not as a routine SPPS monomer but as a fluorescent small-molecule probe.
Dansyl-L-proline has a long history as a site-selective probe for Sudlow site II of human serum albumin. Competitive displacement can therefore be used to test whether another ligand occupies the same binding region. This is a more specific application than describing the compound simply as a “fluorescent amino acid.”
Product Information
| Product Name | Dansyl-L-proline |
| Catalog No. | AS4098 |
| CAS No. | 1239-94-7 |
| Molecular Formula | C17H20N2O4S |
| Molecular Weight | 348.42 g/mol |
| Chemical Identity | N-dansyl-L-proline |
| Building Block Type | Fluorescent dansylated amino-acid probe |
| Primary Applications | Fluorescence binding studies, albumin site-II competition assays and analytical research |
Why Dansyl-L-Proline Is Useful in Albumin Binding Studies
The fluorescence of a dansyl probe is sensitive to its local environment. Binding to a hydrophobic albumin pocket can shift spectral behavior and change fluorescence intensity, allowing binding and displacement to be followed without covalently labeling the protein. We consider this site-II marker role the key differentiator for Dansyl-L-proline in procurement and experiment design.
A Fluorescent Probe Is Not the Same as a Fluorescent Peptide Building Block
The proline nitrogen is already sulfonylated by the dansyl group, so Dansyl-L-proline is not equivalent to an Fmoc-protected proline monomer for standard chain elongation. If the goal is instead to place a fluorophore at a defined position in a synthetic peptide, the design issues are closer to those discussed in our N-terminal versus lysine side-chain fluorescent labeling guide.
Related Dansyl Amino-Acid Chemistry
Changing the amino-acid portion of a dansyl derivative changes polarity, sterics and protein-binding behavior. Dansyl-L-Leu-OH is a useful related compound for laboratories comparing different dansylated amino-acid scaffolds. The two products share the same fluorophore but should not be assumed to have identical binding-site selectivity.
Procurement and QC Considerations
Confirm CAS 1239-94-7, formula C17H20N2O4S, MW 348.42 g/mol and L-proline identity. Because fluorescence experiments can be sensitive to trace impurities and solvent conditions, lot-specific chromatographic purity, storage history and solution preparation should be documented alongside the nominal chemical identity.
Product Documents
A Safety Data Sheet (SDS / MSDS) is available for this product to support laboratory handling, storage and safety assessment.
Certificates of Analysis (COAs) are batch-specific. Please contact us to request the COA for your product, and we will provide it by email.
Frequently Asked Questions
What is Dansyl-L-proline commonly used for?
A well-established use is as a fluorescent probe for Sudlow site II of human serum albumin in binding and competitive-displacement studies.
Is Dansyl-L-proline a normal SPPS amino acid?
No. Its amino nitrogen is already derivatized with the dansyl sulfonyl group, so it is better regarded as a fluorescent amino-acid probe than as a standard Fmoc/Boc monomer.
Can Dansyl-L-proline be compared with Dansyl-L-Leu-OH?
Yes as related dansylated amino-acid probes, but their amino-acid structures differ and their binding behavior should be measured rather than assumed to be identical.
Related Technical Resources
Compare another dansylated amino-acid probe: Dansyl-L-Leu-OH.
Explore custom fluorescent peptide labeling options.