70nucleotide

70-nucleotide, abbreviated as 70-nt, refers to a nucleic acid strand that contains 70 nucleotides. This length applies to both DNA and RNA sequences and is long enough to support defined secondary structures and functional motifs while remaining within typical chemical synthesis capabilities.

In synthesis, 70-nt oligonucleotides are routinely produced by solid-phase phosphoramidite chemistry with high fidelity. Purification commonly employs gel or high-performance liquid chromatography, and many 70-nt strands are synthesized with chemical modifications such as fluorophores, quenchers, or backbone changes for stability or detection. Yields and purification complexity increase with length, particularly for sequences with high GC content or repetitive regions.

For lengths beyond straightforward synthesis, assembly strategies are used. Overlapping synthetic fragments can be joined enzymatically or by ligation, and PCR-based assembly can generate longer constructs. In molecular biology research, 70-nt sequences are frequently used as random-region libraries for SELEX (aptamer selection), where the length provides substantial diversity and the capacity to form stable three-dimensional structures.

Applications of 70-nt oligonucleotides include serves as DNA probes and primers, antisense or regulatory oligos in certain contexts, and building blocks in DNA nanotechnology and nanostructures. They also function as transcription templates, sequencing adapters, or scaffolds for functionalization in various assay formats.

Design considerations focus on GC content, predicted secondary structure, and avoiding problematic motifs. Computational tools such as Mfold or NUPACK help assess folding and stability, while practical considerations include desired nuclease resistance and compatibility with downstream applications.