Guide RNA is the RNA that tells a Cas nuclease where to cut, and buying it well is mostly a matter of choosing the right format for the experiment before you look at price. A synthetic single guide, a two-part crRNA and tracrRNA pair, an in vitro transcribed guide made in your own lab and a guide expressed from a plasmid are four different products with four different cost structures. This page explains the choice and points at the vendor comparison for the synthetic options.
Single guide or two-part guide
A single guide RNA fuses the targeting sequence and the scaffold into one molecule, which is convenient and is what most published protocols expect. The two-part format keeps the target-specific crRNA short and cheap and reuses one universal tracrRNA across every target, so a screen across dozens of targets often costs less as a two-part order. The two parts must be annealed before use, which is a small step but a real one, and not every Cas variant accepts both formats.
Synthetic versus in vitro transcribed
Chemically synthesised guides arrive ready to use, can carry stabilising modifications at the ends, and are the usual choice for ribonucleoprotein delivery into primary cells where an unmodified RNA is degraded and triggers innate immune sensing. In vitro transcription from a DNA template is far cheaper per guide and suits a lab making many guides for cell lines, but the product carries a triphosphate and no protective chemistry, and quality varies with the hands that made it. The decision is about the cells and the delivery route, not the price alone.
Modifications and what they cost
End modifications such as 2'-O-methyl bases and phosphorothioate linkages at the first and last few positions protect the guide from exonucleases and are now standard for primary cell and in vivo work. They add cost per guide and add a purification requirement, because a modified full-length product has to be separated from failure sequences. Ask each vendor what modification pattern they offer as standard and whether the price quoted includes purification and a mass spectrometry certificate.
Reading the vendor comparison
The RNA synthesis pages on this site record the published prices for synthetic RNA by scale and purification, verified on the vendor's page and dated. Use them to compare like with like: the same length, the same modification pattern, the same purity grade. A guide quoted at a low headline price with purification and modification as extras usually ends up costing more than one quoted complete.
Questions people ask about guide rna
What is the difference between guide RNA and sgRNA?
Guide RNA is the general term for the RNA that directs a Cas nuclease. sgRNA is the single-molecule format that fuses crRNA and tracrRNA; a two-part crRNA plus tracrRNA pair is also a guide RNA.
Should I buy modified guide RNA?
For primary cells, stem cells, in vivo delivery or any ribonucleoprotein work, yes; the end modifications materially improve editing and reduce immune sensing. For routine cell-line editing from a plasmid, expression from the plasmid replaces the purchase.
How long does synthetic guide RNA take to arrive?
Typically days for a standard sgRNA and longer for heavily modified or HPLC-purified orders; each vendor's page states its lead time and the comparison links to it.
Can I make guide RNA myself?
Yes, by in vitro transcription from a PCR template or a linearised plasmid. It is cheap and quick but unmodified, and quality control is on you.