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Universal Bases for Oligonucleotides

Build flexibility into primers, probes, and adapters with inosine, 5‑nitroindole (5NI), 3‑nitropyrrole (3NP), and K‑Base to tolerate sequence diversity without redesign. End‑to‑end services from design to RUO→GMP‑like manufacturing.

Inosine (dI) 5‑Nitroindole (5NI) 3‑Nitropyrrole (3NP) K‑Base Degenerate Primers Probe Rescue ISO 9001:2015 ISO13485:2016 45+ Years of Expertise U.S.A. Facilities-Texas GLP/GMP-Aligned
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Overview Products Workflow FAQ References

Universal Base Overview

Universal bases enable wobble-tolerant pairing so assays can tolerate naturally variable sites, polymorphisms, or mixed templates without constantly redesigning primers or probes. We offer inosine (dI) and hydrophobic universal bases (5NI, 3NP, K-Base) with design assistance on placement and Tm correction. We provide purification (desalt, PAGE, HPLC), QC (OD260, LC-MS where applicable), and ISO-aligned documentation from research to GMP-like scale.

Design support
Placement & Tm modeling
Purification
Desalt • PAGE • HPLC
QC options
OD260 • LC-MS (as applicable)
Scale
nmol → multi-gram
  • Universal base oligonucleotides for degenerate primers, probes, and adapters.
  • Inosine (dI) wobble pairing vs hydrophobic universals (5NI, 3NP).
  • Tm corrections and polymerase compatibility guidance.
  • Probe rescue and mixed-template assays.
  • RUO → GMP-like synthesis with ISO-aligned QC.
  • HPLC/PAGE purification & optional LC-MS.
  • Custom formats (tubes, plates, kits) and barcoding for scale.
  • Consultative design support for challenging templates.

Products

Order universal-base oligos as single items or panels. We’ll advise on placement limits and Tm impact.
Modification Description Typical Use Code
Inosine (dI) Natural nucleoside analog (pairs preferentially with C but tolerates A/U/T or G). Useful as a “wobble” placeholder. Degenerate site [dI]
5-Nitroindole (5NI) Hydrophobic universal base that stacks but does not H-bond; preserves duplex without strict base recognition. Mismatched/unknown base [5NI]
3-Nitropyrrole (3NP) Hydrophobic universal base similar to 5NI with different stacking profile; stabilizes duplex while masking identity. Mismatched/unknown base [3NP]
K-Base Alternative hydrophobic universal; fine-tune placement and count to avoid excessive Tm loss. Degenerate site [K-Base]
Tip: Limit consecutive universals; intersperse with native bases and consider short spacers to buffer local Tm drops.
  • Placement limits: avoid long consecutive stretches of universal bases; test 1–2 positions per primer/probe region first.
  • Tm considerations: hydrophobic universals lower Tm more than inosine. Compensate by lengthening the oligo or adjusting GC content.
  • Polymerase compatibility: verify extension across hydrophobic universals with your chosen enzyme; some combinations slow kinetics.
  • QC: OD260 as standard; LC-MS offered for sequences amenable to ionization/detection.

Every universal base oligo is built on Bio-Synthesis’s custom DNA/RNA synthesis platform, supporting phosphoramidite amidite chemistry with over 300+ available modifications. We specialize in universal base amidite coupling, degenerate primer design consultation, and batch documentation for regulated research. Applications include qPCR primer design, mutation scanning, sequencing adapters, and hybridization-based probe assays.

Workflow — Design → Build → Validate → Scale

STEP 1 Design Placement & Tm correction Constraints & polymerase STEP 2 Build Synthesis & purification QC per spec STEP 3 Validate Pilot runs, assay fit Adjust placement STEP 4 Scale RUO → GMP-like path Kitting & logistics
Step 1

Design

Placement & Tm correction
Constraints & polymerase

Step 2

Build

Synthesis & purification
QC per spec

Step 3

Validate

Pilot runs, assay fit
Adjust placement

Step 4

Scale

RUO → GMP-like path
Kitting & logistics

FAQ

What’s the difference between inosine and hydrophobic universal bases?
Inosine wobbles (prefers C); hydrophobic universals (5NI, 3NP) stabilize stacking without H‑bonding. Thermal penalties differ; 5NI is typically less destabilizing than 3NP.
How many universal bases can I use?
Start with 1–2 per primer/probe region; avoid long consecutive runs. Compensate Tm as needed.
More FAQ'sAll FAQ's

References

Universal bases & design considerations

  1. Martin FH, Miguel Castro, Aboul‑ela F, Tinoco I Jr. Base pairing involving deoxyinosine: implications for probe design. Nucleic Acids Res. 1985;13(24):8927‑8938. PubMed • PMC
  2. Loakes D. The applications of universal DNA base analogues. Nucleic Acids Res. 2001;29(12):2437–2447. PMC • PubMed
  3. Loakes D, Brown DM, Linde S, Hill F. 3‑Nitropyrrole and 5‑nitroindole as universal bases in primers for DNA sequencing and PCR. Nucleic Acids Res. 1995;23(13):2361–2366. PDF
  4. Hill F, et al. Polymerase recognition of synthetic degenerate and universal bases. Nucleic Acids Res. 1998;26(10):2473–2480. PMC

Vendor & application notes

  1. Glen Research. 5‑Nitroindole‑CE Phosphoramidite. Product
  2. Glen Research. Mixed and Universal Bases (overview). Application note
  3. Glen Report 8.11. New Universal and Degenerate Bases. Article • PDF
  4. Glen Report 9.15. Properties of Oligonucleotides Containing the Bases P and K. Article

Why Choose Bio-Synthesis

Trusted by biotech leaders worldwide for over 45 years of delivering high-quality, fast, and scalable synthetic biology solutions.

Greetings, Researchers,

Please be advised that any information, guidelines, write-ups, and oral/video/graphic content on our website are intended solely as general guidelines.
It is the researcher's sole responsibility to conduct thorough research on the design of products intended for their experiments before submitting
their designs to Biosynthesis for production feasibility review.
Thank you for your understanding.

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