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Halogenated Base-Modified Oligonucleotides

Custom halogenated base-modified oligonucleotides for photo-crosslinking, DNA repair, polymerase recognition and structure-function research.

Modification by Type 5-Br-dU / 5-I-dU / 5-F-dU Photo-Crosslinking DNA Damage & Repair Polymerase Recognition
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Overview Research Goals Families Selection Guide Products Design Notes FAQ Contact
Overview

Modified Nucleobases for Photochemistry, Repair and Recognition Studies

Bio-Synthesis supports custom halogenated base-modified oligonucleotides for studies requiring nucleobase-level substitution with fluorine, chlorine, bromine, iodine or specialty halogenated analogs.

Halogenated nucleobases are modified base analogs where the halogen changes size, electronegativity, polarizability, photochemistry or biological recognition. These substitutions are useful for photo-crosslinking, DNA damage and repair studies, polymerase recognition, heavy-atom effects, structure-function analysis and mechanistic nucleic acid research.

This page is best classified as Modified Oligonucleotides → Modification by Type → Halogenated Bases because the defining feature is the incorporated halogenated nucleobase chemistry rather than a single downstream application.

Halogen Effect Guide

small substitution, large chemical effect
F

Fluorine

Small, highly electronegative; useful for recognition and analog studies.

Cl

Chlorine

Moderate size; useful comparison point in halogen-series designs.

Br

Bromine

Polarizable and photoactive; common for 5-bromo-dU studies.

I

Iodine

Large, heavy atom; useful for photo-crosslinking and structure studies.

Research Planning

Why Researchers Use Halogenated Bases

Halogenated nucleobases provide controlled changes in size, electronegativity, polarizability and photochemical behavior. Different halogens support different experimental objectives.

Research Objective Common Analog Typical Benefit
Photo-crosslinking 5-Iodo-dU, 5-Bromo-dU UV-induced crosslink formation and interaction mapping
DNA Damage & Repair 5-Bromo-dU, 5-Fluoro-dU Damage recognition and repair pathway studies
Polymerase Recognition 5-Fluoro-dU Enzyme compatibility and extension studies
Heavy Atom Effects 5-Iodo-dU Enhanced structural and photochemical properties
Structure-Function Analysis Br / I analogs Modified stacking and molecular interactions
Halogen Bonding Studies F / Cl / Br / I analogs Investigation of non-covalent recognition mechanisms
Supported Families

Halogenated Base Families

Br

5-Bromo-dU / rU

Brominated uracil analogs for photo-crosslinking, DNA damage, repair and polymerase recognition workflows.

I

5-Iodo-dU / rU

Iodinated uracil analogs for photo-crosslinking, heavy-atom effects and protein or nucleic acid contact studies.

F

5-Fluoro-dU / rU

Fluorinated base analogs for enzyme recognition, base perturbation and antimetabolite-style research models.

Cl

5-Chloro-dU

Chlorinated analogs for comparison across halogen series and modified-base recognition studies.

C

Halogenated Cytidine Analogs

Specialty modified cytidine analogs for base-pairing, repair and structure-function experiments.

X

Custom Halogenated Bases

Project-specific halogenated base analogs reviewed for synthesis feasibility, purification and QC planning.

Selection Guide

Choose Halogenated Base by Research Goal

Use this guide as a starting point. Final design should consider sequence context, number of substitutions, oligo length, enzyme compatibility and photoactivation conditions.

Research Goal Suggested Base Design Note
Photo-crosslinking 5-Br-dU, 5-I-dU, 5-Br-rU, 5-I-rU UV/photoactivation wavelength, exposure and sequence context matter.
DNA damage and repair studies 5-Br-dU, 5-I-dU, 5-F-dU Use matched natural-base controls and consider repair enzyme specificity.
Polymerase recognition 5-Br-dU, 5-F-dU Validate enzyme tolerance, extension efficiency and misincorporation behavior.
Heavy atom / structural effects 5-I-dU, 5-Br-dU Larger halogens can support heavy-atom and structure-focused experiments.
Base-pairing perturbation 5-F-dU, 5-Cl-dU, halogenated C analogs Confirm Tm, mismatch behavior and duplex geometry experimentally.
Supported Products

Supported Halogenated Base Modifications

The table organizes common and custom halogenated base options by analog, halogen, DNA/RNA compatibility and typical research use.

Base Analog Natural Base Replaced Halogen Series Typical Application Technical Note
5-Bromo-dU dT / U analog Br DNA Photo-crosslinking, DNA damage, polymerase studies Bromine increases polarizability and can support photoactivated chemistry.
5-Iodo-dU dT / U analog I DNA Photo-crosslinking, heavy atom studies, structure probing Large iodine substituent supports strong photoactivity and heavy-atom effects.
5-Fluoro-dU dT / U analog F DNA Base analog, enzyme recognition and antimetabolite-style studies Fluorine is small but strongly electronegative; biological context matters.
5-Chloro-dU dT / U analog Cl DNA Modified-base recognition and damage/repair studies Intermediate halogen size; useful for comparison with Br/I/F analogs.
5-Bromo-rU rU analog Br RNA RNA photo-crosslinking and RNA structure studies Useful when RNA context and uridine substitution are required.
5-Iodo-rU rU analog I RNA RNA photo-crosslinking and protein/RNA contact mapping Commonly selected for photo-crosslinking logic in RNA workflows.
5-Fluoro-rU rU analog F RNA RNA base analog and enzyme recognition studies May alter enzyme recognition while preserving compact base geometry.
Halogenated dC analogs dC analog F / Br / I DNA Base-pairing, repair and structure-function studies Availability and feasibility depend on requested analog and sequence context.
Custom halogenated bases Base-specific analog F / Cl / Br / I DNA / RNA Specialty modified-base research Project review recommended for synthesis feasibility and QC planning.
Design Suggestions

Technical Notes & Design Considerations

Halogenated base performance is controlled by halogen identity, position, number of modified bases, sequence context, light exposure and enzyme compatibility.

Fluorine, chlorine, bromine and iodine differ in size, electronegativity and polarizability. Do not assume one halogenated base can be substituted for another without changing the assay behavior.
Internal base substitutions usually affect duplex structure and enzyme recognition more than terminal placement. Avoid modifying essential recognition motifs unless that is the experimental question.
Include an unmodified natural-base control and, when possible, a scrambled or mismatch control so the effect of the halogenated base can be interpreted clearly.
Bromo and iodo analogs may require carefully controlled UV conditions. Exposure time, wavelength, distance, buffer and target accessibility can change crosslinking efficiency.
Polymerases, ligases, nucleases and repair enzymes may respond differently to halogenated bases. Validate the specific enzyme system rather than assuming universal compatibility.
Use HPLC or PAGE purification and mass spectrometry confirmation, especially for long oligos, multiple substitutions or designs that also include dyes, quenchers or conjugation handles.
Applications

Applications for Halogenated Base-Modified Oligos

UV

Photo-Crosslinking

5-bromo and 5-iodo analogs for light-triggered crosslinking and contact mapping studies.

DDR

DNA Damage & Repair

Modified-base constructs for studying repair enzymes, damage recognition and lesion-like behavior.

POL

Polymerase Recognition

Evaluate enzyme tolerance, extension, misincorporation and modified-template behavior.

STR

Structure-Function Studies

Probe how halogen size and polarizability influence pairing, stacking and duplex geometry.

HB

Halogen Bonding

Explore halogen-mediated recognition, biomolecular interactions and structural effects.

SYN

Synthetic Biology

Build specialty modified-base constructs for engineered nucleic acid systems.

Common Research Questions

Questions Researchers Frequently Ask

Can 5-bromo-dU replace thymidine?

5-Bromo-dU is commonly used as a thymidine analog for DNA damage, repair and photo-crosslinking studies.

How does 5-iodo-dU enable photocrosslinking?

The iodine substituent promotes photochemical reactions that can capture biomolecular interactions.

What is the difference between 5-Br-dU and 5-I-dU?

Both are photoactive, but iodine generally provides stronger heavy-atom and photochemical effects.

Do halogenated bases affect duplex stability?

Effects depend on halogen type, sequence context and modification position.

Can halogenated oligos be combined with fluorescent dyes?

Yes. Many projects combine halogenated bases with dyes, quenchers and affinity tags.

Which halogenated bases work with polymerases?

Compatibility depends on the enzyme system and should be experimentally validated.

Frequently Asked Questions

FAQ

Which halogenated bases are commonly used?
Common examples include 5-bromo-dU, 5-iodo-dU, 5-fluoro-dU, 5-chloro-dU and RNA analogs such as 5-bromo-rU or 5-iodo-rU. Custom halogenated cytidine or specialty analogs may also be reviewed.
What are halogenated base-modified oligonucleotides?
They are DNA or RNA oligos containing nucleobase analogs where a halogen such as fluorine, chlorine, bromine or iodine is incorporated into the base structure. These substitutions can affect reactivity, polarizability, recognition and photochemistry.
When should I choose 5-bromo-dU?
5-bromo-dU is often selected for photo-crosslinking, DNA damage/repair, mutagenesis-related models and polymerase recognition studies. It is also useful as a comparison point against 5-iodo or 5-fluoro analogs.
When should I choose 5-iodo-dU or 5-iodo-rU?
 Iodo analogs are useful when strong photoactivity, heavy-atom effects or photo-crosslinking logic is desired. They are often considered for structure mapping or protein/nucleic acid contact studies.
Do halogenated bases affect Tm or base pairing?
 They can. Effects depend on halogen identity, base position, sequence context, number of substitutions and whether the analog is placed internally or near an end. Matched natural-base controls are recommended.
Are halogenated bases compatible with polymerase workflows?
 Some are compatible in specific contexts, but polymerase, ligase or nuclease behavior must be validated experimentally. Bulky or photoactive analogs can change enzyme recognition.
Can halogenated base oligos be combined with dyes or other labels?
 Yes, many designs can combine halogenated bases with fluorescent dyes, quenchers, biotin, amino modifiers, click handles or spacers. Spacing and purification should be reviewed during design.
What QC is recommended?
 HPLC or PAGE purification with mass spectrometry identity confirmation is recommended. Additional UV/Vis, purity analysis or application-specific testing may be useful for crosslinking or enzyme studies.
More FAQ'sAll FAQ's
Contact & Quote Request

Need help designing a halogenated base oligo?

Share your sequence, target halogenated base, desired position, number of substitutions, DNA/RNA format, application, UV/photoactivation conditions, scale, purification target and QC requirements. Bio-Synthesis can help review feasibility and design appropriate controls.
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Fast Quote Checklist

Include sequence, base analog, position, substitution count, scale, purification and QC.

Sequence Base analog Position UV condition QC
Scientific Background & Recommended Reading

Recommended Reading

Selected references for 2′→5′ oligoadenylates, RNase L biology, alternative RNA linkages and prebiotic nucleic acid chemistry.

  1. Silverman RH. Viral encounters with 2′,5′-oligoadenylate synthetase and RNase L during the interferon antiviral response. Journal of Virology. 2007.
    Background on the biological 2-5A/RNase L pathway.
  2. Player MR, Torrence PF. The 2-5A system: modulation of viral and cellular processes through acceleration of RNA degradation. Pharmacology & Therapeutics. 1998.
    Detailed review of 2′→5′ oligoadenylate biology.
  3. Usher DA, McHale AH. Nonenzymatic joining of oligoribonucleotides on a polyuridylic acid template. Science. 1976.
    Classic work relevant to alternative RNA linkage formation.
  4. Engelhart AE, Hud NV. Primitive genetic polymers. Cold Spring Harbor Perspectives in Biology. 2010.
    Context for prebiotic genetic polymers and alternative backbone structures.
  5. Torrence PF, Johnston MI. 2-5A and related 2′,5′-oligoadenylates. Methods in Enzymology. 1981.
    Foundational methods and biology for 2′→5′ oligoadenylate systems.

Note: References provide scientific background and design context. Final oligo design should be evaluated with the target sequence, linkage placement, assay conditions and purification/QC requirements.

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