Stable Markers for Northern Analysis

Ambion's Millennium Markers™ are designed to provide accurate size determination of single-stranded RNA transcripts from 0.5-9 kb and can be used in any Northern protocol. Because of their even spacing, Millennium Markers are ideal for constructing very accurate standard curves for mRNA size determination. They also provide a reference for easy verification and comparison of known bands.

Millennium Markers are a mixture of 10 sizes of in vitro transcripts: 0.5, 1, 1.5, 2, 2.5, 3, 4, 5, 6, and 9 kb. They are available unlabeled or biotinylated for your convenience. The unlabeled markers can be stained with ethidium bromide during or after electrophoresis, or can be end-labeled.

RNA markers are more stable (Figure 1) and resistant to RNases (Figure 2) when stored in formamide. Therefore, we now provide the Millennium Markers in formamide. To use, simply add the Northern Loading Buffer to the markers and heat, just as you would treat your RNA samples.

Figure 1. Stability of RNA Millennium Markers™ Stored in Aqueous Buffer and Formamide. Millennium Markers stored in aqueous buffer and formamide were incubated at room temperature for up to one week.

Figure 2. Stability of RNA Markers When Exposed to RNase A. 2 µg of Millennium Markers™-Formamide and 3 µg of a competitor's RNA Ladder were treated with the specified amount of RNase A for 30 minutes at room temperature. Following incubation, formaldehyde load dye was added, samples were heat denatured at 80°C for 10 minutes and electrophoresed together on a 1% formaldehyde agarose gel. Note that the Millennium Markers-Formamide are at lower concentration and yet are still more stable than the competitor's RNA Ladder even at much higher concentrations of RNase A.

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