In mammalian cells the introduction of small 21–23 nucleotide sequence-specific RNA duplexes (small/short interfering RNAs, siRNAs) can act to initiate post-transcriptional gene knockdown and avoid triggering non-specific effects in mammalian cells (Figure 1).  BLOCK-iT™ siRNAs are traditional, unmodified siRNA duplexes synthesized on demand with the highest quality. Using our award-winning BLOCK-iT™ RNAi Designer, you can design Custom BLOCK-iT™ siRNA sequences for any organism, using a cDNA sequence or a GenBank® accession number.

Custom BLOCK-iT™ siRNAs provide:

  • The ability to custom design any number of siRNAs and controls
  • High-quality, error-free siRNA duplexes
  • A cost-effective approach for RNAi experiments
  • Easy ways to design and order the most widely referenced RNAi product

Figure 1. Typical siRNA duplex:  21 nucleotides long, with 2 DNA base-pair overhangs (TT).

Ordering information

For your convenience BLOCK-iT™ siRNAs can be ordered in 4 different synthesis scales. To design and order BLOCK-iT™ siRNAs, please visit the BLOCK-iT™ RNAi Designer. Custom siRNAs can also be ordered by email.

Guarantee: The BLOCK-iT™ RNAi Designer is such an effective tool for designing siRNAs, that if you order the three best siRNA sequences designed by the BLOCK-iT™ RNAi Designer, we guarantee that at least two of them will give greater than 70% knockdown of mRNA, given that transfection efficiency in your experiment is at least 80%*

*Please contact Technical Support to take advantage of this offer. Please be prepared to fax or email your order reference number, oligonucleotide sequences and data showing your transfection efficiency and knockdown. This offer is good for one free duplex per target.


Product Literature

Web Seminars & Guides


See options for Custom services