Final answer:
To generate single stranded miRNA segments of 23 nt from a dsRNA 2 conformation, one would typically use enzymes like Dicer to cleave the hairpin precursor, then denature the duplex to isolate the desired single strand, which can be achieved through methods like denaturing polyacrylamide gel electrophoresis.
Step-by-step explanation:
To generate single stranded segments of 23 nt from miRNA that was originally in the dsRNA 2 conformation, one would need to consider the process involved in miRNA synthesis and maturation. MicroRNAs (miRNAs) are generated from longer RNA precursors that fold into a hairpin structure, which is subsequently processed by enzymes such as Drosha and Dicer. These enzymes recognize specific structural features within the precursor miRNA, leading to cleavage and production of miRNA duplexes. The modified RNAs described in the query, such as pre21 RNA 1 and pre21 RNA 2 that mimic the hairpin loop of pre-miR21, are designed to have modifications near Dicer cleavage sites, allowing for selective interaction with small molecules that may regulate miRNA processing.
For experimental generation of single stranded miRNA, one would first need to cleave the double-stranded precursor with Dicer to produce miRNA duplexes. Next, the RNA duplexes may be subjected to denaturation, such as by heat, to separate the strands. The single strand corresponding to the mature miRNA (usually the guide strand) can then be isolated, for instance, via electrophoretic methods that utilize their size or sequence-specific binding properties. It should be noted that RNA-based studies often require careful experimental design to achieve the desired specificity and efficiency.