v2 and v3 chemistry share the same barcode structure, and the structure is the same for DNA and Protein libraries.
A barcode is a unique DNA sequence ligated to fragments within a sequencing library for downstream in-silico sorting and identification. The barcodes are attached to the 5' end of the R1 (forward) reads. After generating the DNA libraries, these barcodes need to be removed from the sequence and used as cell identifiers.
For more information, refer to the Tapestri Pipeline User Guide.
v2 Barcodes (present in v2 and v3 chemistries)
Barcoding Bead: PhotoC-Element---Read 1 (36 bp)---BC1 (9 bp)---Off-Constant (14 – 17 bp)---BC2 (9 bp)---Constant2 (15 bp)
PhotoC-E is a linker that is bound between the Read 1 and the beads. This allows us to cleave the oligo from the beads when exposed to long-wave, low-wattage UV light.
Read 1 is the read primer where Illumina’s sequencing primer binds to start the sequencing process.
With Off-Constant offsets of 0 to 3 as follows:
- 0 Bases = no base
- 1 Base = C
- 2 Bases = TC
- 3 Bases = GTC
Forward Primer: Constant2 (15 bp)---Fwd primer (17 – 33 bp)
Reverse Primer: Rev primer (17 – 33 bp)---Read2 (34 bp)