Protocol for Bridging double-stranded DNA with a single-stranded DNA oligo using NEBuilder HiFi DNA Assembly (NEB #E2621)

This method allows you to assemble a single-stranded DNA (ssDNA) oligo insert and a double-stranded DNA (dsDNA) vector fragment. The resulting construct can be used to prepare a library of inserts using the same overlap sequences at each end and a variable region in the middle, as in the following application note: Bridging dsDNA with a ssDNA Oligo and NEBuilder HiFi DNA Assembly to create an sgRNA-Cas9 Expression Vector

This protocol is recommended for the assembly of the following types of DNA fragment:

• Short ssDNA inserts with 25 nucleotide (nt) overlaps
• dsDNA vector linearized by PCR or restriction digest

Single-stranded DNA oligo design

The ssDNA oligo should have 25-30 nucleotide overlaps on each end with the vector; there is no need to phosphorylate the 5’ end. This protocol is recommended for short insert sizes (1-25 bases). Please be aware, longer ssDNA oligos are more prone to secondary structure formation which may impact assembly performance.

DNA Quantities

This protocol uses a 1:200 (vector:insert) molar ratio with 0.005 picomoles of vector and 1 picomole of ssDNA oligo.

Protocol

1. Dilute resuspended oligos (100 μM stock) to a final concentration of 0.2 μM (0.2 pmol/μl) using TE buffer (10 mM Tris, 0.1 mM EDTA; pH 8.0) supplemented with 50 mM NaCl (or 1X NEBuffer r2.1). This can be done by taking 1 µl of 100 μM oligo stock and diluting it with 499 μl of buffer.
2. Set-up the following reaction on ice:

* NEBioCalculator (NEBioCalculator.neb.com) can help with DNA mass to molar quantity conversions for both ssDNA and dsDNA.

Note: If you are working with large plasmids >10 kb in size we recommend NEB ® 10-beta Competent E. coli (High Efficiency) (NEB #C3019H). If your plasmid or insert contain repetitive sequences, we recommend NEB ® Stable Competent E. coli (High Efficiency) (NEB #C3040H).