# Nextera XT input considerations

**Sample input is the most important factor in a successful Nextera XT library prep**.

The first step in the Nextera XT library preparation workflow is the tagmentation reaction, which involves the transposome cleaving and tagging the double-stranded DNA with a universal overhang. The tagmentation efficiency is a key factor for the success of the library preparation.

The Nextera XT library preparation kit is optimized for **1 ng** double-stranded genomic DNA.

Quantify the input DNA with a fluorometric method, such as PicoGreen or Qubit. Avoid using methods that quantify total nucleic acid, like UV absorbance methods.

The transposomes are end-point enzymes, in that they cleave double-stranded DNA one time only and then the step is complete. Therefore, successful tagmentation is highly dependent on the input mass.

* **Using > 1 ng can lead to undertagmentation of the sample.**
* **Using < 1 ng can lead to overtagmentation of the sample.**

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| *For any feedback or questions regarding this article (Illumina Knowledge Article #1023), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000001023%20-%20Library%20Preparation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |


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