16th May 2017

AptaBasics: What is an Aptamer Library?

Last week we described what aptamers are and the fact they have a variable region. This week we will discuss the scale of the library and why this makes aptamers suitable to many applications.

To generate the largest possible aptamer library, we start with a combinational library of DNA or RNA. The combinational library then undergoes degenerative mutation to increase the diversity of aptamers present. The degeneration causes the aptamers to change from their original sequences, increasing diversity in the population.

The aptamers in the library contain variable regions of 20-80 nucleotides long, giving a possible 420-480 sequences. We are able to then use this library to select aptamers to specific targets.

Other Libraries

Having a larger library increases the chance of finding a suitable match for a target. Each aptamer library has about 1015 opportunities to deliver a binding molecule fitting your specific target with appropriate affinity and binding characteristics.

Library vs log scale of molecules present.

A graph comparing different combinational libraries to the number of different molecules present.

Other combinational libraries are much smaller than an aptamer library. A good combinational chemical library consists of about 1 million different molecules. A recombinant phage display library will contain around 45 billion different structures whereas our degenerative combinational aptamer library will have approximately to 1015 molecules. This makes an aptamer library is 22,000 bigger than a recombinant phage display library and a billion times larger than a combinational chemical library!

When a library is this large, it is common for several aptamers to have a high binding affinity to the target of interest. This is one of the key advantages to aptamer selection. At Aptamer Group we use customer defined conditions to select an aptamer that best fits the intended end use application.

Within a library there may also be aptamers that can differentiate between molecules that differ by just one functional group. Next week we will use case study data to show how specific aptamers can be.

If you are interested in how aptamers can support your research and development objectives, please call us on +44 (0) 1904 567 790 or email  info@aptamergroup.co.uk.