When working with the NEBNext Low-bias Small RNA Library Prep Kit, a sample is considered "enriched small RNA" if most of the input mass is compatible or is made compatible with the ligation chemistry (5´ phosphate and 3´ hydroxyl group) and is within the size range for capture with this kit (< 120 nt).
Examples of enriched small RNAs include isolated endogenous small RNAs (e.g., gel size selection or size fractionation), ribosome-protected fragments that have been end repaired (5´ phosphate and 3´ hydroxyl ends) (Ribo-seq), total RNA that has been fragmented within size range and end repaired, and appropriately sized synthetic RNAs (e.g. guide RNAs).
