Convertible Base Oligos

Convertible Base Modified Oligonucleotides

Post‑synthetic functionalization, reactive handles, and lesion mimics for assay development. Popular options include 5‑F‑dC (TMP‑5‑F‑dU), O6‑Phenyl‑dI, 2‑F‑dI, O4‑Triazolyl‑dU, and m6A—plus halogenated and thio/oxo variants for crosslinking, mutagenesis, and epigenetics.

Overview

Convertible base oligonucleotides incorporate bases engineered to be transformed or to provide a reactive leaving group after synthesis. These scaffold bases are used to install probes, form crosslinks, mimic DNA/RNA lesions, or introduce epigenetic marks at defined sites.

Post‑synthetic conversion Crosslinking bases Epigenetic marks Mutagenesis tools QC: HPLC • LC‑MS
Why convertible?
  • Single, addressable site for post‑synthetic modification
  • Photo/redox/chemical crosslinking at precise positions
  • Lesion/epigenetic standards for mechanistic assays
Typical outputs
  • Dye/quencher/biotin install via substitution or click
  • Protein–DNA crosslinks with halogenated handles
  • m6A or oxidized bases for reader/repair studies
QC & scale
  • Desalt → HPLC/UPLC
  • LC‑MS identity; conversion yield summary
  • RUO → GMP‑like documentation

Technology & Methods

Convertible Leaving Groups

O4‑triazolyl‑dU and activated 5‑position pyrimidines undergo substitution with amines, thiols, or azides to install labels or linkers after synthesis.

Halogen‑Assisted Crosslinking

5‑Br/5‑I pyrimidines and 8‑Br purines support photo/radical crosslinking/footprinting to probe nucleic acid–protein contacts.

Lesion/Epigenetic Mimics

Defined modifications such as m6A or oxidized bases serve as standards for reader/writer assays and sequencing controls.

Design tip: Choose by conversion chemistry (nucleophile vs. photolysis) and buffer compatibility. Model Tm when placing multiple sites.

Applications

Post‑Synthetic Labeling

Install dyes, quenchers, biotin, or click handles at a single locus for FRET, hybridization probes, and pull‑down.

Crosslinking & Footprinting

Map protein–nucleic acid interfaces using photo/radical‑activated bases (e.g., 5‑Br‑dU).

Mutagenesis & Repair

Introduce convertible lesions or epigenetic marks (m6A) to study repair fidelity and reader proteins.

Products & Ordering

Product / Modification Description Function Application Code
Convertible 5‑F‑dC (TMP‑5‑F‑dU) Pyrimidine with convertible handle derived from 5‑fluoro scaffold. Post‑synthetic substitution / labeling Site‑specific dye/biotin install; probe optimization [5‑F‑dC]
Convertible dA (O6‑Phenyl‑deoxy Inosine) dI analog with O6‑aryl functionality enabling downstream conversion. Reactive site installation Reporter/ligand attachment at A‑position [O6‑Phenyl‑dI]
Convertible dG (2‑Fluoro deoxy inosine) 2‑fluoro inosine scaffold used as a convertible surrogate for G. Nucleophilic substitution Post‑synthetic label installation [2‑FdI]
Convertible dU & dC (O4‑Triazolyl dU) O4‑triazolyl‑dU enables displacement by nucleophiles. Leaving‑group chemistry Attachment of amines/thiols/azides [O4‑Tri‑dU]
N6‑Methyl rA (m6A) Defined epigenetic adenosine mark for RNA. Epigenetic mimic / binding studies Reader assays, mapping, standards [m6A]
5‑Bromo‑dU Halogenated dU; photo/radical activation for crosslinking/footprinting. Photo‑induced crosslinking Protein–DNA mapping [5‑Br‑dU]
5‑Iodo‑dU Iodinated dU with high crosslink propensity under activation. Crosslinking handle Interface mapping [5‑I‑dU]
4‑Thio‑dT Thio‑modified thymidine; UVA‑reactive for crosslinking at defined sites. Photo‑crosslinking (UVA) RNA/DNA–protein interaction studies [4‑Thio‑dT]
8‑Bromo‑dG Purine analog used as lesion/conversion adjunct. Lesion mimic Repair pathway interrogation [8‑Br‑dG]
Customizations: internal placements, multiple convertible sites, PEG/hexa‑EG spacers, purification from Desalt to HPLC/UPLC, aliquots & kitting, RUO→GMP‑like documentation.

Technical Notes

  • Placement & Tm considerations. Space convertible sites ≥3–4 nt from termini. For multiple sites, model Tm shifts and adjust length or salt.
  • Conversion chemistry. Prefer mild nucleophiles (amines/thiols/azides). Validate on a short test oligo; avoid backbone‑damaging conditions.
  • Crosslinking conditions. For 5‑Br/5‑I bases, follow established photo/radical protocols with no‑UV controls. For 4‑Thio‑dT, UVA (~365 nm) is typical.
  • Purification & analytics. HPLC/UPLC is recommended for post‑conversion products. LC‑MS verifies mass shift; PAGE helps separate conjugate sizes.
  • Storage & handling. Store dried at −20 °C; avoid repeated freeze–thaw. Protect photoactive bases from light.

Ready to specify your convertible bases?

Send sequence, placement, conversion goal, and purification level—We’ll return a tuned design and QC plan.

Ordering Checklist

Sequence & placement
Target sequence, position(s) of the convertible base, and any flanking LNA/2′-OMe.
Conversion chemistry
Planned nucleophile (amine/thiol/azide), dye/biotin partner, or click (azide/alkyne).
Spacer/geometry
Optional PEG/hexa‑EG spacer length or internal vs terminal attachment preferences.
Scale & purification
Requested scale (µmol → multi‑gram) and purification (Desalt vs HPLC/UPLC).
QC & documentation
LC‑MS confirmation, (optional) UV/Vis, CoA & method summary, RUO→GMP‑like docs.
Pilot & logistics
Pilot conversion request, formulation/buffer, aliquots, barcoding, and shipping needs.

FAQ

What’s a “convertible base”?

A base with a reactive/convertible position that can be transformed after oligo synthesis—useful for on‑demand labeling or crosslinking.

Do these alter hybridization?

Usually minimal effects; we compensate via length/composition or by adding LNA/2′‑OMe nearby.

Can you do the conversion step?

Yes. We can convert, purify (HPLC/UPLC), confirm by LC‑MS, and supply a CoA.

RNA support?

Selected chemistries are available for RNA—share your target and we’ll confirm feasibility.

How do I choose between O4‑triazolyl‑dU and 5‑halogenated dU (5‑Br‑dU/5‑I‑dU)?

O4‑triazolyl‑dU supports nucleophilic substitution (amines/thiols/azides) for post‑synthetic labeling. 5‑Br/5‑I dU are favored for photo/radical crosslinking and footprinting. Select by intended mechanism and buffer constraints.

What conversion yields should I expect for convertible bases?

Yields depend on sequence context, reagent, and work‑up. Typical crude‑to‑purified conversion recoveries can range from ~50–90%. We recommend a short pilot conversion to tune conditions before scaling.

Can you attach dyes or biotin after conversion?

Yes—common partners are NHS esters (amines), maleimides (thiols), and azide/alkyne pairs for click chemistry. Spacers (PEG/hexa‑EG) can reduce quenching and steric effects.

Are LNA or 2′‑OMe compatible near a convertible site?

Generally yes. LNA/2′‑OMe can flank a convertible base to maintain Tm. Consider sterics for bulky substituents and confirm with a short Tm check.

What purification do you recommend after conversion?

HPLC/UPLC is recommended for clean separation of converted vs. unconverted species. Desalting alone may leave mixed populations.

Do you support photo‑reactive bases (4‑Thio‑dT, psoralen) on convertible scaffolds?

We can evaluate feasibility. 4‑Thio‑dT and psoralen require UVA and light controls; we’ll advise on placement and handling.

How do you verify conversion and labeling?

We confirm by LC‑MS; for chromophores, we can also provide UV/Vis data. PAGE or CE can assist with size/charge shifts.

What scales and documentation do you offer?

Synthesis from µmol → multi‑gram with CoA, method summaries, and optional RUO→GMP‑like documentation.

Speak to a Scientist

References

  1. Reviews on convertible nucleosides and post‑synthetic modification strategies.
  2. Applications of halogenated and thio bases for crosslinking/footprinting.
  3. Use of epigenetic base analogs (e.g., m6A) in assay standardization.

We can align specific literature protocols to your design upon request.

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