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An isolation kit helps you isolate a material of interest. When we talk about an isolation kit, we are likely talking about a kit that helps you isolate nucleic acid (RNA or DNA) or protein. These kits often contain all the buffers and hardware you need for your isolation. Let’s do a review of the types of isolation kits and how they work, then we’ll give you a general protocol to understand how the process works!

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RNA isolation kit

You can read a more detailed article about RNA isolation kits in our article “RNA purification kit”. For general RNA isolation, silica is used to bind RNA in a sample. This is based on the discovery that nucleic acids bind favorably to silica. Some kits contain centrifuge tubes with a silica filter in them that catch RNA. Other kits are magnetic bead based where the beads are coated in silica. In the presence of the correct pH and chaotropic salts, RNA is favored over DNA. mRNA can be probed for more specifically by pre-conjugating magnetic beads to oligo-dT chains, which will bind the poly-A tail of mRNA. 

DNA isolation kit

You can read more about DNA isolation in our article “magnetic DNA purification…”. In brief, DNA isolation kits come in centrifuge tube or bead based, like RNA isolation kits. The capture of DNA vs RNA is controlled by pH and the presence of chaotropic salts. Like most isolation kits, a DNA isolation kit will usually contain all the buffers you need as well. We will discuss which buffers you need below in a quick protocol.

Protein isolation kit 

You can read more about protein isolation in our article “protein isolation protocol”. An example of how protein isolation can be done by magnetic beads is by using magnetic beads pre-conjugated to Ni-NTA. A protein will be expressed with something called a his-tag (poly-histidine) and the his-tag will bind specifically to a Ni-NTA tag. Then the his-tag can be cleaved to release your protein once everything else in solution has been washed away in the magnetic bead protocol.

Quick isolation kit protocol for isolation

Step 1: You want to incubate your beads or centrifuge filter with your sample. Your kit will have a binding buffer in it that will create an ideal binding environment for your molecule you want to isolate. 

Step 2: Once your sample has had sufficient time to bind, you will use a washing buffer to wash away anything not bound to your bead or filter. If you are using a centrifuge tube, you will use a centrifuge to push the wash buffer through the filter. If you are a magnetic bead, you will simply put your sample container on a magnetic separator which will separate your beads from the rest of the solution. 

Step 3: When you have done enough wash steps, you will elute your sample. Your kit will have an elution buffer which creates an ideal environment for your sample to be removed from your centrifuge tube filter or the magnetic bead.

Free guide: Magnetic bead coatings: Today and Tomorrow

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Lluis M. Martínez | SEPMAG Chief Scientific Officer

Founder of SEPMAG, Lluis holds a PhD in Magnetic Materials by the UAB. He has conducted research at German and Spanish academic institutions. Having worked in companies in Ireland, USA and Spain, he has more than 20 years of experience applying magnetic materials and sensors to industrial products and processes. He has filed several international patents on the field and co-authored more than 20 scientific papers, most of them on the subject of magnetic particle movement.

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