2'-OMe-U-PACE Phosphoramidite

5'-Dimethoxytrityl-2'-OMe-Uridine,3'-O-(N,N-diisopropylamino)-phosphinyl-1,1-dimethyl-2-cyanoethyl acetate

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Product Specifications

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PACE modifications have enjoyed a resurgence in interest as applied to the field of CRISPR gene editing. In an initial publication, it was shown that single guide RNAs (sgRNA) provided significantly higher activity in cells when 2‘-O-methylthiophosphonoacetates were incorporated on the ends of the guide RNA to protect against cellular nucleases.1 In subsequent studies, 2’-OMe PACE modified sgRNAs were also shown to significantly increase on-target specificity of the CRISPR-Cas9 DNA cleavage in eukaryotic cells. In a recent paper, the incorporation of 2’-OMe PACE modified nucleotides in the 20-nucleotide guide region of the sgRNA was shown to decrease off-target cutting by over an order of magnitude while in most cases increasing the overall on-target efficiency as compared to unmodified single guide RNA.2

As an optimal cycle, we recommend using DCI as an activator (30-3150-XX) and a 15 minute coupling time. Following coupling, cap using Unicap with a regular coupling time and then oxidize using 0.5 M CSO for 3 minutes. Alternatively, a 33 minute coupling time using 0.45 M tetrazole, oxidation using low-water iodine (40-4032-XX) followed by capping with 6.5% DMAP as Cap B will give acceptable results. For deprotection, pre-treat the synthesis column with 1.5% DBU in anhydrous acetonitrile for 60 minutes at room temperature to remove 1,1-dimethyl-2-cyanoethyl protecting groups. Rinse the column with ACN, dry under argon and complete deprotection with 40% Methylamine for 2 hours at room temperature.



  • Coupling: 15 minute coupling time using 0.25M DCI (30-3150-xx) is recommended. Using the phosphoramidite-based capping reagent Unicap (10-4410-xx), cap using a regular coupling time and then oxidize with 0.5M CSO for 3 minutes for best results.
  • Deprotection: Pretreat synthesis column with 1.5% DBU in anhydrous acetonitrile for 60 minutes at room temperature. Rinse with acetonitrile and dry with argon. Deprotect using 40% methylamine for 2 hours at room temperature.
Diluent Anhydrous Acetonitrile
Storage Freezer storage, -10 to -30C, dry
Stability 2-3 days

Intellectual Property

These products are covered by patents, US 6,693,187 and 7,067,641, and patents pending owned by Metasense Technologies. Purchase of all or any of these products includes a limited license to use the products solely for the manufacture of oligonucleotides for research use only. This license specifically excludes the use of the product or oligonucleotides containing the product for: (a) therapeutic or diagnostic applications (including kits, pools, libraries and other products or services that incorporate oligonucleotides containing the product), (b) any in vivo toxicity/safety study in support of an investigational new drug application (or foreign counterpart), or (c) resale (including sale of kits, pools, libraries and other products or services that incorporate the product or oligonucleotides containing the product). If such activities have commercial application, a separate license is required from Metasense Technologies. Neither the product nor any product created through its use may be used in human clinical trials. A simple agreement must be signed before end-users and custom oligo services may purchase these products for use as defined above.

Dilution/Coupling Data

The table below show pack size data and, for solutions, dilution and approximate coupling based on normal priming procedures.

ABI 392/394

Catalog # Pack Size Grams/Pack 0.1M Dil. (mL) Approximate Number of Additions
LV40 LV200 40nm 0.2μm 1μm 10μm
10-3153-02 0.25 g 0.25 3.01 87 52.2 32.63 23.73 17.4 4.35
10-3153-05 0.5 g 0.5 6.02 187.33 112.4 70.25 51.09 37.47 9.37
10-3153-10 1.0 g 1 12.03 387.67 232.6 145.38 105.73 77.53 19.38


Catalog # Pack Size Grams/Pack Dilution (mL) Approximate Number of Additions
Molarity 50nm 0.2μm 1μm 15μm
10-3153-02 0.25 g 0.25 4.49 0.07 83.4 52.13 37.91 5.21
10-3153-05 0.5 g 0.5 8.98 0.07 173.2 108.25 78.73 10.83
10-3153-10 1.0 g 1 17.96 0.07 352.8 220.5 160.36 22.05


1. A. Hendel, et al., Nat Biotechnol, 2015, 33, 985-989.
2. D.E. Ryan, et al., Nucleic Acids Res, 2018, 46, 792-803.