# TruSeq DNA PCR Free library preparation input

**Why are different input amounts used to generate 350 bp and 550 bp PCR-Free libraries?**\
The input recommendations were tested and validated to yield appropriate final yields for sequencing. Illumina recommends 1 µg input for the 350 bp target insert size and 2 µg for the 550 bp target insert size. In order to generate sufficient nanomolar concentration of libraries for sequencing with the larger 550 bp insert length, 2 μg of input material is required, due to the longer insert size compared to the 350 bp workflow.

**Can the input DNA quantity be reduced?**\
Illumina does not support or recommend input amounts lower than 1 μg for a 350 bp insert size or 2 μg for a 550 bp library. It is possible that reducing the amount of input material may fail to generate enough library to successfully proceed with sequencing.

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| *For any feedback or questions regarding this article (Illumina Knowledge Article #1182), contact Illumina Technical Support* [*techsupport@illumina.com*](mailto:techsupport@illumina.com?subject=Question%2FFeedback%20Regarding%20Illumina%20Knowledge%20Article%20#000001182%20-%20Library%20Preparation%20\&body=Dear%20Illumina%20Technical%20Support,%0D%0A%0D%0A)*.* |


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