6-FAM SE (6-Carboxyfluorescein N-succinimidyl ester) is another isomer of carboxyfluorescein. 6-FAM SE is mainly used for labeling nucleotides and sequencing nucleic acids.

I. Nucleic acid sequencing
1. Labeling nucleotides: 6-FAM SE reacts with the 5' end of the nucleotide or oligonucleotide, and the succinic anhydride group reacts with the primary amine group in the nucleic acid to form a covalently bound fluorescent dye.
2. Fluorescence detection: During the sequencing process, the labeled nucleotides will emit fluorescence (excitation wavelength: 495 nm, emission wavelength: 520 nm), and the automatic sequencer can detect the fluorescence signal to determine the base sequence.
II. Gene expression analysis
1. Labeling probes: 6-FAM is used as probes in qPCR experiments, which are designed to bind to specific regions of the target gene.
2. Quantification: The fluorescence signal generated during the amplification process is proportional to the number of target genes, so that gene expression can be quantitatively analyzed.
III. Molecular biology detection:
1. Probe preparation: 6-FAM is labeled on a nucleic acid probe, which will hybridize with the target sequence.
b. Detection: The fluorescence signal emitted by the 6-FAM-labeled probe is detected by fluorescence microscopy.