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Explore cEt sugar-modified nucleic acid chemistry for RNA-binding affinity, nuclease resistance, and research-stage antisense oligonucleotide development.
Constrained ethyl (cEt) nucleic acid is a 2′,4′-bridged sugar modification used in antisense oligonucleotide research. Its bicyclic structure limits how freely the sugar can move, helping the modified nucleotide adopt a geometry that pairs favorably with complementary RNA.
cEt was developed by combining design features of locked nucleic acid (LNA) and 2′-O-methoxyethyl (2′-MOE) chemistry. Researchers use it to explore strong RNA binding, resistance to nuclease degradation, and the balance between antisense activity and tolerability.
One important use is in gapmer antisense oligonucleotides. cEt residues can be placed in the flanking wings, while a central DNA gap remains available to recruit RNase H and promote cleavage of the target RNA. The right number and position of cEt residues depend on the sequence and intended application.
At Bio-Synthesis, we can review cEt-modified sequences, monomer sourcing, synthesis scale, purification, and analytical requirements before confirming manufacturing feasibility.
Constrained ethyl (cEt) nucleotide molecular architecture with bridged sugar bonds highlighted in green.
Structure note: cEt is distinct from ENA, LNA, and 2′-MOE. The exact monomer configuration, nucleobase, and protecting groups must be confirmed before synthesis.
Published work has explored cEt as a high-affinity modification for antisense research. These properties are useful starting points, but the final result depends on the entire sequence and backbone design.
The constrained sugar can improve duplex stability when a cEt-modified oligonucleotide binds complementary RNA.
cEt-containing oligonucleotides have shown resistance to nuclease degradation in published experimental systems.
cEt can be evaluated in the modified wings of an RNase H-dependent gapmer without replacing the central DNA gap.
Wing composition, backbone chemistry, and placement can be adjusted to study activity, specificity, and tolerability.
Research perspective: cEt is not universally safer or more potent than LNA or 2′-MOE. Sequence-matched comparisons and appropriate biological testing are essential.
The best design starts with the mechanism: do you want to cleave RNA through RNase H, or block an RNA interaction without cleavage?
For RNase H-dependent ASOs, cEt is commonly considered for the flanking regions. Preserve an appropriate DNA gap and compare modified-wing patterns using target knockdown, RNA cleavage, thermal stability, and tolerability assays.
Important: A fully cEt-modified oligonucleotide should not be assumed to support RNase H-mediated cleavage.
These modifications are not interchangeable. Each offers a different combination of structure, affinity, development experience, and supply considerations.
Confirm the exact cEt phosphoramidite, stereochemical configuration, available nucleobases, coupling and deprotection conditions, and desired final yield. Define purity and identity testing, such as HPLC/UPLC and mass spectrometry, before production.
Quotation note: A requested final purified amount is not the same as the synthesis starting scale.
A gapmer combines modified wings with a DNA region that can support RNase H-mediated target RNA cleavage. cEt is one possible wing chemistry; its placement should be optimized rather than treated as a fixed recipe.
cEt placement options
RNase H-compatible region
Establish whether RNA cleavage or steric blocking is the intended outcome.
For RNase H designs, test gap length, boundaries, and cleavage experimentally.
Screen cEt placement against a matched 2′-MOE or LNA control when useful.
Assess target activity, stability, protein interactions, and tolerability.
The colored circles indicate regions, not nucleotide counts or a validated 4–7–4 sequence. See the peer-reviewed studies below for cEt gapmer research.
cEt is most closely associated with antisense chemistry development, where modification choice influences binding, stability, and biological response.
Explore cEt-containing wings while retaining a DNA gap for RNase H activity.
Gapmer synthesis →
Compare matched sequences and wing chemistries for RNA knockdown.
Custom antisense →
Study affinity, stability, activity, and tolerability during candidate selection.
Therapeutic support →
Evaluate high-affinity RNA recognition where cleavage is not the intended mechanism.
Splice-switching services →
Specialty cEt phosphoramidites require a reagent and method review before manufacturing. We begin with your sequence, the modification positions, and the amount of purified material you actually need.
Confirm sequence, cEt positions, backbone, and target application.
Verify nucleobase options, configuration, supply, and permitted use.
Evaluate coupling efficiency, deprotection, and scale.
Plan appropriate HPLC/UPLC and MS testing.
Confirm final yield, purity, formulation, and documentation.
Bio-Synthesis: We support custom oligonucleotide chemistry development and analytical characterization. cEt-specific synthesis and delivery are subject to reagent availability and feasibility confirmation.
If you are evaluating cEt, these related services may help you compare alternative modifications or plan a complete antisense oligonucleotide design.
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Compare sugar, backbone and conjugate options.
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AmNA Chemistry
Compare amido-bridged nucleic acid with cEt.
Explore AmNA ↗
Share your sequence, research goal, and required final yield. Our team can review cEt placement, monomer sourcing, purification, and analytical requirements.
Sequence, cEt positions, target RNA, RNase H compatibility, and comparator chemistry.
cEt monomer availability, synthesis conditions, purification, and analytical identity.
cEt-modified oligonucleotide projects are subject to reagent availability, technical feasibility, and applicable intellectual-property requirements. Manufacturing availability is confirmed only after review.
cEt chemistry was developed and studied in antisense research programs at Isis Pharmaceuticals (now Ionis Pharmaceuticals). Published studies describe both the underlying monomer design and its evaluation in antisense oligonucleotides.
Because cEt is a specialty modification, commercial availability and permitted uses should be confirmed for the specific monomer and project. A published synthesis route does not automatically establish unrestricted commercial supply or freedom to operate.
Bio-Synthesis can review the technical requirements and explore reagent sourcing before committing to pricing, manufacturing timelines, or delivery.
These papers describe the development of cEt nucleosides and their evaluation in antisense designs. Findings apply to the experimental systems studied and should not be generalized to every cEt sequence.
DOI: 10.1093/nass/nrn280 — early cEt and cMOE monomer design and evaluation.
DOI: 10.1021/jm801294h — results for specific short antisense designs in animal models.
DOI: 10.1021/jo902560f — synthetic and biophysical evaluation of cEt/cMOE chemistry.
DOI: 10.1039/C2CC32286B — structural analysis and nuclease resistance.
DOI: 10.1093/nar/gkaa031 — study of cEt-wing gapmers and phosphorothioate stereochemistry.
The scientific literature supports specific experimental findings; it does not establish universal potency, safety, or commercial availability.
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