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Cross-Linking Base Modified Oligonucleotides

Photoreactive oligonucleotide chemistries for DNA/RNA cross-linking, structure probing, and protein interaction mapping.

Structure Probing Protein–Nucleic Acid Mapping UV-Induced Capture Photoactivatable Oligos Photoreactive Oligonucleotides

UV-Activated Cross-Linking Chemistry for DNA/RNA Structure & Interaction Studies

UV-activated cross-linking chemistries enable covalent bonds between DNA/RNA strands or between nucleic acids and proteins. These modifications are useful for structural biology, probing nucleic acid secondary structures, mapping protein-nucleic acid interactions, photochemical assays and stabilized nucleic acid complex studies.

Cross-linkers generally fall into two practical categories: nucleic acid intercalators such as psoralen for site-specific targeting in double- and triple-stranded DNA, and halogenated bases such as 5-bromo-dC, 5-iodo-dC and 5-iodo-dU for intra-strand cross-linking, site-specific damage models or protein-directed capture.

Bio-Synthesis provides custom cross-linker oligonucleotides tailored for research, diagnostic and therapeutic development workflows with scalable synthesis, purification and analytical QC support.

Design

Select site, strand, linker reach and duplex context.

Synthesize

Build psoralen, halogenated or convertible base oligos.

Activate

Use UVA exposure and controls to form covalent links.

Analyze

Validate by PAGE, HPLC, MS or mapping workflows.

Photoreactive Oligonucleotide Chemistry Guide

A cleaner chemistry guide for selecting psoralen intercalators, halogenated photoreactive bases, or convertible reactive bases based on your cross-linking goal, activation strategy and downstream analysis.

Ψ

Psoralen Intercalators

Best for interstrand cross-linking in stable duplex or triplex nucleic acid structures.

Psoralen C6 Psoralen-TEG
Activation
UVA irradiation, commonly around 320–365 nm.
Mechanism
Intercalates into helical regions and forms covalent interstrand links after activation.
Use For
Duplex stabilization, triplex studies, structure probing and photochemical assay development.
Note
TEG linker can improve reach and accessibility in selected designs.
Br/I

Halogenated Photoreactive Bases

Best for UV-dependent site-specific photochemistry, damage models and protein interaction capture.

5-Br-dC 5-I-dC 5-I-dU
Activation
UV irradiation; exact conditions depend on assay format and target system.
Mechanism
UV exposure generates reactive intermediates that support covalent capture and cross-linking.
Use For
Protein–DNA/RNA mapping, photochemical probes, interaction capture and DNA damage studies.
Note
Placement and sequence context strongly affect yield and specificity.
dG

Convertible Reactive Bases

Best for specialized conjugation, covalent capture and custom nucleic acid labeling strategies.

Convertible dG Custom reactive bases
Activation
Project-dependent; selected based on conjugation or capture chemistry.
Mechanism
Reactive nucleobase chemistry enables post-synthetic modification or targeted covalent capture.
Use For
Protein conjugation, specialized labeling, interaction mapping and multifunctional constructs.
Note
Often requires custom purification and analytical confirmation planning.

Need interstrand duplex stabilization?

Start with psoralen C6 or psoralen-TEG.

Need protein or interaction capture?

Consider 5-I-dU, 5-I-dC, 5-Br-dC or convertible dG.

Need a custom multifunctional probe?

Start with psoralen C6 or psoralen-TEG.
Practical UV activation and control notes
  • UVA exposure around 320–365 nm is commonly used for psoralen activation.
  • Optimize UV dose, exposure distance, temperature, buffer, and target concentration for each assay.
  • Use no-UV, no-modifier, unmodified oligo, and target-minus controls to separate specific cross-linking from nonspecific photochemistry.
  • Analyze cross-linked products by denaturing PAGE, HPLC, MS, primer extension, digestion mapping, or other project-specific methods.
Experimental recommendation: UV wavelength, exposure time, sequence context, spacer architecture, target accessibility, duplex stability and analytical workflow should all be evaluated during cross-linking oligo design. Small pilot studies are recommended before scale-up or screening applications.

Applications for Photoreactive & Photoactivatable Oligonucleotides

Cross-linking base modified oligonucleotides are commonly used in structural biology, interaction mapping, photochemical capture workflows, stabilized nucleic acid systems and UV-induced probe development programs.

RNA

Protein–RNA Interaction Mapping

Photoactivatable oligos support RNA-binding protein studies, CLIP-style workflows, interaction capture and UV-dependent covalent stabilization.

DNA

DNA Structure Probing

Psoralen and halogenated bases help probe duplex accessibility, secondary structure and higher-order nucleic acid organization.

UV

Photochemical Assays

UV-activated cross-linking workflows support assay development, probe validation and target engagement studies.

CAP

Protein Capture Workflows

Halogenated and convertible bases support protein–DNA and protein–RNA covalent capture strategies.

STB

Stabilized Duplex Systems

Interstrand cross-linking can stabilize nucleic acid complexes for biophysical, structural and translational studies.

MAP

Interaction & Damage Mapping

Cross-linkers may be used to study repair pathways, UV-induced damage and site-specific interaction regions.

Psoralen vs. Halogenated Bases

The optimal cross-linking chemistry depends on whether the goal is interstrand stabilization, protein capture, structure probing or UV-triggered photochemistry.

Feature Psoralen Intercalators Halogenated Bases
Typical Cross-Linking Mode Interstrand duplex/triplex cross-linking Intra-strand or protein-associated cross-linking
Common Products Psoralen C6; Psoralen-TEG 5-Br-dC; 5-I-dC; 5-I-dU
Activation UVA irradiation UV irradiation
Best Fit Stable duplex systems and structure probing Protein capture, DNA damage and photoreactive assays
Spacer Flexibility High with TEG linker options Typically site-specific base replacement
Common Applications Duplex stabilization, triplex studies, structural mapping Protein-binding studies, UV damage models, capture workflows

Placement, Architecture & Cross-Linking Strategy

Cross-linking oligos should be designed around the target structure, intended covalent linkage, cross-linker reach, UV exposure window, and downstream analytical method.

Placement & Architecture

  • Intercalator targeting: place psoralen within stable double- or triple-stranded segments, often near favorable helical regions.
  • Intra-strand goals: choose halogenated bases when the goal is intra-strand linking, site-specific damage or direct protein capture.
  • Spacing & reach: flexible spacers such as TEG can improve accessibility to the intended partner strand or protein.
  • Context mixing: cross-linkers can be combined with 2'-OMe, 2'-MOE, LNA wings or phosphorothioate backbones when stability tuning is needed.

Probe vs. Therapeutic Context

  • For analytical probes, prioritize signal specificity, site accessibility and clean readout.
  • For therapeutic or translational research constructs, evaluate safety, clearance, off-target reactivity and stability.
  • Bio-Synthesis can help model melting temperature and recommend positions to balance cross-link yield, hybridization and off-target risk.
  • Small-scale pilot lots can support method optimization before larger synthesis or scale-up.
1

Define Target

Duplex, triplex, protein complex, secondary structure or capture target.

2

Select Chemistry

Psoralen, halogenated base, convertible base or mixed modification design.

3

Place Modifier

Position cross-linker for reach, specificity, Tm and downstream readout.

4

Optimize UV

Run dose and time controls to maximize specific product formation.

5

Validate Product

Analyze by denaturing PAGE, HPLC, MS or mapping workflow.

Experimental considerations: Cross-linking efficiency depends on sequence context, duplex accessibility, UV dose, temperature, buffer composition, target concentration, spacer flexibility and target structure. Small pilot studies are strongly recommended before large-scale synthesis or screening workflows.

Synthesis, Purification & Analytical Documentation

CH

Chemistry Options

  • Psoralen C6 and Psoralen-TEG intercalator formats.
  • 5-Br-dC, 5-I-dC and 5-I-dU halogenated bases.
  • Convertible dG for protein capture and conjugation studies.
  • PO, PS and mixed backbone strategies.
PUR

Purification Support

  • HPLC or PAGE purification depending on construct and target purity.
  • RP-HPLC with diafiltration may be used for selected conjugates.
  • Purification strategy can be adapted for dyes, affinity tags, peptides, PEG and chelators.
QC

QC & Documentation

  • Identity confirmation by ESI-MS or MALDI.
  • Purity by HPLC and optional SEC for selected conjugates.
  • COA with yield, method parameters and impurity profile.
  • ISO 9001 / ISO 13485 alignment; GLP/GMP-like practices as scoped.
Compatibility: Cross-linking bases may be combined with dyes, affinity tags, linkers and other oligo modifications. Placement and purification should be reviewed to reduce interference with hybridization, cross-linking efficiency and downstream analysis.

FAQ

When should I use psoralen vs. halogenated bases?
Psoralen intercalators are preferred for site-specific interstrand links in double- or triple-helical regions. Halogenated bases (e.g., 5-Br-dC, 5-I-dU) are often chosen for intra-strand links or direct protein capture.
Can cross-linkers be combined with dyes or affinity tags?
Yes. Cross-linkers are compatible with a wide range of conjugations; we’ll advise on placement and purification to avoid interference.
Do cross-linker bases affect duplex stability?
Effects are context-dependent; we recommend verifying Tm in your buffer and adjusting length or adding stabilizing sugars (2′-OMe/MOE/LNA) as needed.
What QC is recommended for cross-linking base modified oligos?
 Recommended QC may include HPLC purity, ESI-MS or MALDI identity confirmation, yield reporting and project-specific documentation. Conjugated or complex constructs may require additional analytical methods.
What should I provide for a quote?
 Send the sequence, desired cross-linking base or psoralen format, modification position, scale, purification target, intended application, UV workflow and any additional labels, backbones or conjugates.
What UV conditions are typically used?
 UVA around 320-365 nm is commonly used for psoralen activation. The optimal wavelength, exposure time and dose should be titrated for the sequence, buffer, target complex and analytical readout.

Need help selecting the right cross-linking base?

Share your sequence, target structure or protein complex, preferred cross-linking chemistry, desired modification position, UV workflow, purification target and QC requirements. Bio-Synthesis can recommend optimal modification sites, UV controls and analytical strategies for your project.

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Sequence Modifier Position Scale QC Needs

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