Skip to product details

Chemical product profile

HONGKUN / PRODUCT DIRECTORY

6-Carboxyfluorescein succinimidyl ester | CAS 92557-81-8

An amine-reactive 6-FAM active ester for preparing fluorescent conjugates, combining a defined dye isomer with an NHS coupling group whose integrity is essential to labeling performance.

CAS92557-81-8
Molecular formulaC25H15NO9
Molecular weight473.4 g/mol

Product overview

The succinimidyl ester activates the additional carboxyl group of 6-FAM for reaction with amino groups. The fluorescent core remains present, so hydrolysed free dye can still contribute optical signal even when the reactive ester has been lost. Qualification therefore needs chemical identity and active-ester composition alongside fluorescence measurements.

Chemical identity

Chemical name
6-Carboxyfluorescein succinimidyl ester
CAS number
92557-81-8
Molecular formula
C25H15NO9
Molecular weight
473.4 g/mol

Application context

6-FAM SE is used to introduce a fluorescein label onto amine-bearing molecules through amide formation. Research conjugates may include peptides, proteins or amine-functionalized probes. Free dye removal and degree of labeling are properties of the conjugation process and should be assessed in that system. Name the single 6-isomer explicitly and distinguish this reagent from carboxyfluorescein diacetate succinimidyl ester used in different labeling workflows.

Chemistry and synthetic role

An N-hydroxysuccinimide leaving group supports amide coupling; hydrolysis converts the activated group back to a carboxylic acid.

Quality review

Measure intact active ester

Resolve the NHS ester from hydrolysed 6-FAM rather than relying on fluorescence alone.

Confirm positional-isomer identity

Specify the 6-isomer and an isomer-sensitive analytical method.

Review moisture exposure

Agree water or stability controls suited to maintaining the active ester during handling.

Preparing a specification

Specify single-isomer 6-FAM NHS ester, intact-ester assay, free 6-FAM, positional impurities and moisture-related controls; define the intended amine-bearing substrate.

Packaging and storage

Confirm container compatibility, closure and net weight for the selected grade and destination. Follow the actual supplier SDS and batch label for storage and transport.

Documentation

Request the batch COA, SDS and analytical methods covering the agreed purchasing specification. Confirm which supporting chromatograms and application-specific records are available from the selected manufacturer.

Procurement questions

Does fluorescence prove coupling activity?

No. Hydrolysed free dye can remain fluorescent; check intact ester content.

Is this the diacetate cell-tracking reagent?

No. This identity lacks the phenolic acetate groups of that reagent.

What should a labeling trial measure?

Assess conjugation, residual free dye and degree of labeling in the intended system.

Technical sources
  1. PubChem CAS identity lookupNCBI / PubChem
  2. FAM NHS ester, 6-isomer specificationLumiprobe
  3. FAM NHS ester, 6-isomerLumiprobe