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Thiol-Modified Oligonucleotides

Reactive sulfhydryl functional groups for maleimide coupling, gold nanoparticle attachment, surface immobilization, disulfide-linked conjugates and custom oligonucleotide bioconjugation.

5′ Thiol 3′ Thiol Internal SH Protected S–S Gold Surface Compatible Maleimide Ready PEG Thiol
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Overview Selector Modifiers Reactions Spacers Protected vs Free Challenges Applications Design Related Contact
Overview

Thiol Conjugation Platform for DNA, RNA & Modified Oligos

Thiol-modified oligonucleotides are synthetic DNA, RNA, PNA or modified oligos containing sulfhydryl ( –SH) functional groups. These thiol handles enable controlled conjugation to dyes, peptides, proteins, antibodies, PEG, polymers, nanoparticles, gold surfaces and other biomaterials.

Thiol chemistry is especially useful for maleimide coupling, gold nanoparticle functionalization, gold-coated biosensor surfaces, disulfide exchange, redox-sensitive linkages and therapeutic research designs where surface-active or cleavable conjugation is required.

Design insight: The optimal thiol modifier depends on whether you need a protected or free thiol, desired linker length, 5′/3′/internal placement, target surface or biomolecule, and whether a reducible disulfide linkage is desired.

Interactive Thiol Design Selector

Interactive Thiol Recommendation Tool

Click an application to view the recommended thiol modifier, spacer, protection strategy, typical workflow and design notes. This selector gives first-pass guidance before choosing a specific thiol format.

Interactive Thiol Recommendation Tool

Use this practical guide when you know the application but are not sure which thiol format to request.

Click a tab to update the recommendation
Recommended starting point

5′-Thiol Modifier C6 S-S Routine Conjugation

Protected C6 thiol is usually the best starting format for maleimide-reactive dyes, peptides, proteins and PEG reagents because it balances stability, spacing and coupling accessibility.

Spacer

C6 or TEG

Protection

Protected S-S preferred

Reaction

Reduction then maleimide coupling

Purification

HPLC recommended

Compatible Partners

Maleimide dyes, peptides, proteins, PEG-maleimide

View thiol modifier table See reaction chemistry

Best fit

  • Maleimide dyes
  • Maleimide peptides
  • PEG-maleimide
  • Protein or antibody coupling

Design note

  • Use amine-free and thiol-compatible conditions after reduction to maximize conjugation efficiency.

Typical Workflow

↻
Protected –SH
→
Reduce (TCEP)
→
Maleimide
→
Thioether ✓
Final Product Stable Thioether Linkage Routine Workflow
Recommended starting point

Free or Reduced C6/C12 Thiol Routine Conjugation

Gold nanoparticles, gold electrodes and SPR-style gold surfaces generally require a free thiol or freshly reduced protected thiol for Au-S attachment.

Spacer

C6, C12 or TEG

Protection

Free or reduced before use

Reaction

Au-S surface binding

Purification

HPLC recommended

Compatible Partners

AuNPs, gold electrodes, SPR chips, gold films

View surface applications See reaction chemistry

Best fit

  • Gold nanoparticles
  • Gold electrodes
  • SPR chips
  • Electrochemical sensors

Design note

  • C12 or TEG can improve surface presentation for bulky targets.

Typical Workflow

↻
Protected –SH
→
Reduce
→
Gold Surface
→
Au–S Bond ✓
Final Product Au–S Surface Bond Routine Workflow
Recommended starting point

C6, C12 or PEG-Thiol Intermediate Design

For proteins and antibodies, a longer or hydrophilic spacer often improves accessibility and reduces steric crowding between the oligo and biomolecule.

Spacer

C12, TEG, PEG6 or PEG12

Protection

Protected thiol preferred

Reaction

Maleimide or disulfide exchange

Purification

HPLC / Project-specific QC

Compatible Partners

Maleimide proteins, antibodies, enzymes, peptide scaffolds

Compare spacers Ask for review

Best fit

  • Proteins
  • Enzymes
  • Antibody fragments
  • Full antibodies

Design note

  • Protein activation chemistry should be reviewed before selecting the thiol format.

Typical Workflow

↻
Protected –SH
→
Maleimide Protein
→
Protein–Oligo
→
Purify ✓
Final Product Protein–Oligo Conjugate Review Recommended
Recommended starting point

Thiol-PEG4 to Thiol-PEG12 Intermediate Design

PEG thiol spacers are useful when solubility, flexibility and distance from the oligo backbone are important for downstream conjugation.

Spacer

PEG4, PEG6, PEG12+

Protection

Protected preferred

Reaction

Maleimide, polymer or surface coupling

Purification

HPLC recommended

Compatible Partners

PEG-maleimide, polymers, hydrophobic payloads

View PEG thiols Compare linker length

Best fit

  • PEGylation
  • Hydrophobic payloads
  • Protein conjugates
  • Nanoparticle surfaces

Design note

  • Long PEG spacers can alter purification behavior and should be reviewed during conjugate design.

Typical Workflow

↻
SH Oligo
→
PEG–Maleimide
→
PEGylated Oligo
→
Purify ✓
Final Product PEGylated Oligonucleotide Flexible Spacer
Recommended starting point

Activated Disulfide or OPSS Oligo Advanced Design

When the desired linkage must be reducible, activated disulfide and OPSS-style strategies can support disulfide exchange with thiol-bearing partners.

Spacer

Project-specific

Protection

Disulfide chemistry

Reaction

Thiol-disulfide exchange

Purification

HPLC / LC-MS review

Compatible Partners

OPSS, pyridyl disulfide and thiol-bearing payloads

Protected vs free thiol See disulfide chemistry

Best fit

  • Redox-sensitive conjugates
  • Cleavable payload attachment
  • Drug delivery research
  • Controlled-release designs

Design note

  • Reducing conditions and payload stability must be reviewed together.

Typical Workflow

↻
Protected –SH
→
OPSS Linker
→
Disulfide Bond
→
Release ✓
Final Product Redox-Cleavable Linkage Advanced Workflow
Recommended starting point

C6/C12 Thiol or PEG-Thiol Advanced Design

Nanoparticle and nanomaterial conjugation often benefits from longer alkyl or PEG spacers to improve orientation, colloidal behavior and accessibility.

Spacer

C12, TEG or PEG12

Protection

Free/reduced or protected

Reaction

Gold binding or surface coupling

Purification

Project-specific

Compatible Partners

Gold, silica, magnetic beads and quantum dots

View nanomaterial targets Compare spacers

Best fit

  • Gold nanoparticles
  • Magnetic beads
  • Silica particles
  • Quantum dots

Design note

  • Surface density and salt conditions can strongly affect nanoparticle performance.

Typical Workflow

↻
Reduced –SH
→
Nanoparticle
→
Surface Loading
→
Display ✓
Final Product Stable Surface Display Surface Workflow
Recommended starting point

Protected Thiol with Custom Spacer Review Advanced Design

Therapeutic-style research designs often require protected thiols, defined linker spacing, custom purification and analytical confirmation to support controlled conjugation.

Spacer

C6, PEG or custom

Protection

Protected thiol preferred

Reaction

Maleimide, disulfide or custom

Purification

HPLC with MS where feasible

Compatible Partners

ODC payloads, targeting ligands, PEG and custom linkers

Request design review View design notes

Best fit

  • ODC research
  • PEGylated oligos
  • Targeting ligand constructs
  • Custom delivery systems

Design note

  • Payload stability, stoichiometry and analytical release should be defined early.

Typical Workflow

↻
Protected –SH
→
Payload Coupling
→
HPLC Purify
→
QC Release ✓
Final Product Controlled Research Conjugate Scientist Review
Common Thiol Design Workflow

From Application to Purified Thiol-Oligo Conjugate

Use this workflow to frame thiol-modified oligo projects before selecting a specific modifier, spacer, protection strategy and downstream conjugation condition.

1. Define Application
→
2. Choose Thiol Modifier
→
3. Select Spacer
→
4. Protected or Free SH
→
5. Conjugation
→
6. Purification & QC
Available Thiol-Modified Oligonucleotide Modifications

Thiol Modifier Codes and Design Notes

The tables below organize common and advanced thiol-bearing oligo formats used for post-synthetic coupling, gold attachment, disulfide-sensitive conjugation, PEG spacing and multifunctional designs.

Important: Protected thiol forms are often preferred during synthesis, purification and shipment. Deprotection or reduction is typically performed shortly before conjugation to generate the free sulfhydryl group.

👇 Click a tab below to explore thiol modifier families, applications and conjugation recommendations.Tables are grouped so users can scan quickly while preserving a detailed modifier list.

Terminal Thiol Linkers

5′ and 3′ thiol handles for maleimide coupling, gold attachment and directional conjugation.

8 modifiers
Modification Code Position / Scaffold Reaction Applications Notes
5′-Thiol Modifier C6 S-S [5SH-C6-SS] 5′ terminal protected thiol Reduction → maleimide / gold / disulfide exchange General thiol conjugation, gold attachment, protein or peptide coupling Most common protected 5′ thiol format; reduce before coupling.
3′-Thiol Modifier C3 S-S [3SH-C3-SS] 3′ terminal protected thiol Reduction → maleimide / gold / disulfide exchange 3′-directed conjugation, surface attachment, capture probes Useful when the 5′ end must remain available.
5′-Thiol Modifier C6 [5SH-C6] 5′ terminal free thiol Maleimide, gold surface, activated disulfide Direct coupling and Au–S immobilization Immediately reactive; avoid oxidation before use.
3′-Thiol Modifier C3 [3SH-C3] 3′ terminal free thiol Maleimide, gold surface, disulfide exchange Compact 3′ surface attachment and conjugation Short 3′ spacer for direct immobilization.
5′-Thiol Modifier C12 [5SH-C12] 5′ terminal long thiol Maleimide, gold, surface coupling Bulky proteins, nanoparticles, sensor surfaces Longer alkyl spacer improves distance from the oligo.
3′-Thiol Modifier C12 [3SH-C12] 3′ terminal long thiol Maleimide, gold, disulfide exchange Surface display, large payload attachment Useful when the 3′ payload needs more spacing.
5′-Thiol-TEG [5SH-TEG] 5′ terminal flexible spacer Maleimide, gold, polymer coupling Protein conjugation, flexible surface display TEG spacer improves accessibility and flexibility.
3′-Thiol-TEG [3SH-TEG] 3′ terminal flexible spacer Maleimide, gold, surface coupling SPR, microarray, biosensor immobilization Hydrophilic flexible 3′ thiol option.

Typical choice: Use 5′-Thiol C6 S-S for most maleimide coupling workflows and free/reduced C6 thiol for gold surface immobilization.

Internal and Base-Specific Thiol Modifiers

Internal thiol handles for defined sequence placement, structural probes, internal labeling and dual-functional oligo designs.

6 modifiers
Modification Code Position / Scaffold Reaction Applications Notes
Thiol-Modifier dT [dT-SH] Internal thymidine-linked thiol Maleimide, disulfide exchange, gold-assisted designs Site-specific internal labeling, probes, FRET designs Places thiol at a defined internal T position.
Thiol C6 dT [dT-SH-C6] Internal dT with C6 thiol linker Maleimide, activated disulfide Internal payload attachment and structural probes Common internal thiol format with useful spacing.
Internal Thiol C6 Linker [iSH-C6] Internal non-base linker Maleimide, disulfide exchange Internal conjugation when base replacement is acceptable Useful for non-nucleoside internal insertion.
Internal Thiol-TEG [iSH-TEG] Internal flexible thiol spacer Maleimide, gold surface, disulfide exchange Internal labels and sterically crowded designs Flexible hydrophilic internal spacer.
Thiol-Modifier Serinol [SH-Ser] Serinol-based thiol scaffold Maleimide, surface coupling Terminal or internal flexible thiol design Useful for custom spacing and accessibility.
Thiol-dU / U-linked Thiol [dU-SH] Internal uridine-like thiol Maleimide, post-synthetic labeling DNA/RNA probe designs Use when U/dU placement is preferred.

Typical choice: Use Thiol-dT or dT-SH-C6 when the thiol must be placed at a defined internal position without using a terminal end.

PEG and Flexible Thiol Linkers

Hydrophilic thiol spacers for proteins, antibodies, polymers, nanoparticles and sterically demanding payloads.

6 spacers
Modification Code Position / Scaffold Reaction Applications Notes
Thiol-PEG2 [SH-PEG2] Short PEG thiol spacer Maleimide, polymer coupling, gold Small dyes, compact payloads Short hydrophilic spacing.
Thiol-PEG4 [SH-PEG4] PEG4 thiol spacer Maleimide, PEGylation, protein coupling Peptides, small proteins, improved solubility Good balance of spacing and solubility.
Thiol-PEG6 [SH-PEG6] PEG6 thiol spacer Maleimide, polymer/protein coupling Protein and antibody fragment conjugation Useful when steric access matters.
Thiol-PEG12 [SH-PEG12] Extended PEG thiol spacer Maleimide, nanoparticles, therapeutic research Antibodies, nanoparticles, bulky payloads Preferred for large or sterically demanding partners.
Long PEG-Thiol [SH-PEGn] Custom long PEG thiol Maleimide, surface, polymer coupling Therapeutic research, surfaces, large macromolecules Custom feasibility and purification review recommended.
Hydrophilic Thiol Spacer [SH-spacer] Custom flexible thiol spacer Maleimide, gold, biomolecule coupling Assay-specific spacing and solubility tuning Spacer selected based on payload and application.

Typical choice: Use PEG4/PEG6 for moderate spacing and PEG12 or longer PEG designs for antibodies, nanoparticles or therapeutic research conjugates.

Protected, Activated and Redox-Sensitive Thiols

Protected thiols and disulfide formats for stable handling, thiol activation, redox-sensitive linkages and cleavable conjugates.

5 formats
Modification Code Position / Scaffold Reaction Applications Notes
Disulfide-Protected Thiol [SH-SS-protected] Protected thiol Reduction → free SH Storage-stable thiol oligos, maleimide coupling Preferred for synthesis, shipment and storage.
Activated Disulfide [activated-SS] Activated disulfide handle Disulfide exchange Redox-cleavable conjugates, controlled release Supports reducible linkage design.
Pyridyl Disulfide / OPSS Oligo [OPSS-oligo] Pyridyl disulfide Thiol-disulfide exchange Protein/peptide coupling, cleavable designs Useful for coupling to free thiol partners.
Redox-Cleavable Disulfide Linker [redox-SS] Cleavable disulfide linker Reduction-sensitive release Delivery research and cleavable conjugates Useful for intracellular reducing environments.
Thiol with Reducing Activation [protected-SH] Protected terminal/internal thiol DTT/TCEP activation then coupling General conjugation workflow Activation conditions depend on payload and buffer.

Typical choice: Protected thiols are preferred for stability. Activated disulfide and OPSS formats are useful when the desired linkage is reducible.

Multifunctional and Custom Thiol Designs

Dual-handle and custom thiol oligos for orthogonal conjugation, labeling, capture, surface display and advanced architectures.

9 designs
Modification Code Position / Scaffold Reaction Applications Notes
Thiol + Amino Oligo [SH+NH2] Dual functional design Maleimide + NHS ester routes Orthogonal dual conjugation Requires protection and reaction-order planning.
Thiol + Azide Oligo [SH+N3] Dual thiol/click design Maleimide/gold + click chemistry Two-payload or surface-plus-click designs Useful for stepwise conjugation.
Thiol + DBCO Oligo [SH+DBCO] Dual thiol/SPAAC handle Maleimide/gold + copper-free click Copper-free multi-step conjugation Orthogonal chemistry planning recommended.
Thiol + Fluorophore Oligo [SH+Dye] Labeled thiol oligo Gold/maleimide plus optical readout Biosensors, nanoparticles, imaging probes Dye placement should be reviewed for quenching.
Thiol + Biotin Oligo [SH+Biotin] Affinity plus thiol handle Streptavidin capture + gold/maleimide Capture assays, surfaces, pull-down formats Useful for multi-mode capture and immobilization.
Thiol + Cholesterol / Lipid [SH+Lipid] Hydrophobic conjugate plus thiol Surface or secondary coupling Delivery and membrane-associated research Purification can be more complex.
Thiol + GalNAc [SH+GalNAc] Targeting ligand plus thiol Secondary conjugation or immobilization Targeted oligo research and platform builds Custom design review required.
Branched / Multivalent Thiol Oligo [multi-SH] Multiple thiol handles Gold, maleimide, multivalent coupling Nanotechnology, arrays, high-density surfaces Multiple thiols can complicate QC and stoichiometry.
Customer-Supplied Thiol Linker [client-SH-linker] Custom route Project-specific Proprietary linkers or payloads Route depends on solubility, stability and compatibility.

Technical review recommended: Multifunctional thiol designs require careful protection, reaction order, purification and analytical strategy.

Conjugation Chemistry

Thiol Conjugation Reaction Library

Thiol handles support multiple conjugation routes beyond standard maleimide coupling.

Compatible Thiol-Reactive Chemistries

Reactive Partner Reaction Bond / Product Typical Applications Notes
Maleimide Michael addition Thioether conjugate Dyes, peptides, proteins, antibodies, PEG Most common thiol-oligo coupling route.
Gold surface / AuNP Au–S binding Thiol-gold attachment Gold nanoparticles, SPR, electrodes, biosensors Strong surface attachment; salt-aging may be used for AuNPs.
Pyridyl disulfide / OPSS Disulfide exchange Cleavable disulfide Redox-sensitive conjugates, drug delivery research Can release under reducing conditions.
Vinyl sulfone Michael addition Stable thioether-like linkage Polymer or protein attachment Useful in selected biomolecule workflows.
Haloacetyl / iodoacetamide Nucleophilic substitution Thioether conjugate Biomolecule labeling Conditions require careful control.

Maleimide Coupling

Oligo-SH + Maleimide → Thioether

Best for dye, peptide, protein, antibody and PEG conjugates.

Gold Surface Binding

Oligo-SH + Au → Au–S

Best for AuNPs, gold electrodes, SPR chips and biosensors.

Disulfide Exchange

Oligo-SH + OPSS → S–S

Best for reducible or redox-responsive conjugates.

Spacer Selection Guide

How Long Should the Thiol Linker Be?

Thiol Spacer Comparison

Linker Relative Length Flexibility Best Use Design Notes
C3 Short Low Compact 3′ conjugates and surface attachment Minimal spacing; not ideal for bulky proteins.
C6 Medium Moderate General maleimide coupling and gold attachment Most common general-purpose thiol spacer.
C12 Long High Large proteins, nanoparticles and surfaces Useful when extra distance from the backbone is required.
TEG Flexible High Surface display and biomolecule coupling Hydrophilic flexible spacer.
PEG4 / PEG6 Medium hydrophilic Very high Proteins, peptides, polymers Improves solubility and reduces steric effects.
PEG12+ Extended hydrophilic Excellent Antibodies, nanoparticles, therapeutic research Custom review recommended for long PEG constructs.
Protected vs Free Thiol

Should You Use a Protected or Free Thiol?

Protected thiols are typically safer for synthesis and shipment. Free thiols are convenient when immediate coupling or gold attachment is planned.

Protected Thiol

  • Greater storage and shipment stability
  • Helps reduce premature oxidation
  • Requires reduction or deprotection before coupling
  • Preferred for therapeutic-style and high-value conjugation workflows

Free Thiol

  • Immediately reactive toward maleimides and gold
  • Useful for direct coupling in the customer lab
  • Requires careful oxygen and buffer control
  • Best when the conjugation will be performed soon after receipt

Protected Thiol Workflow

Protected S–S → Reduction → Free SH → Conjugate

Recommended when the thiol must survive synthesis, purification, storage and shipment.

Free Thiol Workflow

Oligo-SH → Couple Now

Best for immediate maleimide coupling or gold immobilization workflows.

Oxidation Risk

2 SH → S–S Dimer

Free thiols can oxidize; use reducing and handling conditions appropriate for the project.

Troubleshooting & Design Support

Thiol Design Risk Checklist

Use this checklist to identify oxidation, spacer, surface, purification and reaction-order risks before selecting a thiol format.

Prevent the Most Common Thiol-Oligo Problems

Most thiol conjugation issues come from oxidation, incomplete reduction, spacer selection, surface loading, reaction timing, payload hydrophobicity, or purification complexity. This guide summarizes the problem, likely cause, and recommended design fix.

Best Practical Rule

For most projects, order a protected thiol, reduce immediately before conjugation, and choose a longer or PEG spacer when the payload, protein, nanoparticle, or surface is bulky.

Protected thiol
Fresh reduction
Compatible buffer
Controlled conjugation
HPLC / QC review
Challenge Likely Cause Recommended Solution Design Review
Thiol activation and oxidation
Low conjugation efficiency Thiol oxidation before coupling or incomplete deprotection/reduction. Use freshly reduced thiol, minimize air exposure, and confirm reducing conditions are compatible with the payload. Routine
Unexpected disulfide formation Free thiol oxidation during storage, shipment, or prolonged handling. Order protected thiol formats and reduce immediately before conjugation. Routine
Variable reproducibility Inconsistent reduction time, pH, buffer composition, or reaction timing. Standardize reduction, buffer, pH, reaction time, and purification workflow. Review
Spacer and payload accessibility
Poor protein labeling Spacer is too short or the protein/antibody is sterically crowded. Select C12, TEG, PEG6, or PEG12 thiol spacing to improve accessibility. Review
Low surface coverage Limited accessibility of the thiol or unfavorable surface presentation. Increase spacer length, use PEG/TEG linkers, and optimize immobilization conditions. Review
Hydrophobic conjugate behavior Lipid, cholesterol, dye, or drug-like payload changes solubility and retention. Consider PEG spacers and plan purification method development before synthesis. Technical
Nanoparticle and surface workflows
Gold nanoparticle aggregation High oligo density, rapid salt addition, or insufficient colloidal stabilization. Optimize loading density and use gradual salt-aging or project-specific stabilization conditions. Review
Weak biosensor signal Surface density, linker length, or target accessibility is not optimized. Evaluate C12/TEG/PEG spacers, oligo density, and orientation on the surface. Review
Multifunctional and analytical complexity
Competing reactions Multiple reactive groups are present without a defined reaction order. Use orthogonal multifunctional designs and define the reaction sequence before conjugation. Technical
Difficult purification Large hydrophobic payload, long PEG, multiple reactive handles, or mixed products. Plan HPLC method and analytical QC before synthesis; consider LC-MS/MALDI when feasible. Technical
Therapeutic-style complexity Payload stability, stoichiometry, linker cleavage, and release testing are not defined early. Request scientist review for linker, protection, conjugation, purification, and QC strategy. Advanced

When in doubt, choose protected thiol

Protected thiol formats are usually safer for synthesis, storage, shipment, and controlled activation.

Use longer spacers for bulky partners

C12, TEG, and PEG spacers often improve coupling to proteins, antibodies, nanoparticles, and surfaces.

Plan purification early

Hydrophobic or multifunctional conjugates may require custom HPLC and analytical QC planning.

Need help? Bio-Synthesis can review the thiol handle, spacer, protected/free format, reduction approach, conjugation partner, purification plan, and QC requirements before synthesis.

Applications

Common Thiol-Oligo Conjugation Targets

Where Thiol-Modified Oligos Are Used

Thiol handles support both solution-phase bioconjugation and surface-based immobilization workflows.

Au

Gold Nanoparticles

AuNP-functionalized oligos for diagnostics, biosensing and nanotechnology.

SUR

Gold Surfaces

Gold electrodes, SPR chips, arrays and electrochemical sensors.

PEP

Peptides

Thiol-maleimide peptide-oligo conjugation.

AB

Antibodies

Controlled antibody-oligo conjugation strategies.

PEG

PEG / Polymers

PEG-maleimide and polymer conjugation workflows.

DYE

Fluorophores

Thiol-reactive dyes and dual-functional probes.

ODC

Drug-Like Payloads

Cleavable or reducible ODC research designs.

NP

Nanomaterials

Magnetic beads, silica, quantum dots and thiol-reactive materials.

SPR

Surface plasmon resonance chips.

QCM

Quartz crystal microbalance sensors.

Electrodes

Electrochemical DNA sensors.

Microarrays

Capture and hybridization surfaces.

DNA Nano

Programmable assemblies and AuNP networks.

Design, Purification & QC

Practical Thiol-Oligo Design Considerations

Recommendations for Thiol-Modified Oligos

Consideration Recommendation Why It Matters
Protected vs free thiol Use protected thiol unless the oligo will be coupled immediately. Protection reduces oxidation and undesired side reactions.
Spacer length Use C6 for general work; C12/TEG/PEG for surfaces, proteins and nanoparticles. Spacing improves accessibility and surface presentation.
Buffer compatibility Avoid oxidizing conditions; select reducing/deprotection steps compatible with payload. Thiol oxidation can reduce conjugation efficiency.
Gold applications Use free or reduced thiol with appropriate surface loading conditions. Au–S density and orientation affect assay performance.
Purification HPLC is commonly recommended for modified and conjugated thiol oligos. Separates unmodified oligo, dimers and conjugation byproducts.
QC Confirm identity by MS where feasible; use UV-Vis or HPLC for conjugates. Thiol-protected and conjugated products can require method-specific QC.

Flexible Placement

5′, 3′, internal and custom thiol placement can be evaluated.

Protected Formats

Protected thiols help improve handling during synthesis and shipment.

Custom Conjugation

Support for maleimide, gold, disulfide, PEG and protein conjugation.

Analytical QC

HPLC, LC-MS, MALDI-TOF, UV-Vis and project-specific documentation.

FAQ

What is the best general thiol modifier?
For most maleimide coupling workflows, a 5′-Thiol Modifier C6 S-S or related protected C6 thiol is a good starting point because it balances spacing, stability and conjugation accessibility.
When should I choose a free thiol?
Free thiols are useful when the oligo will be coupled immediately or attached directly to gold surfaces. For storage or shipment, protected thiols are often preferred.
Can thiol-modified oligos be attached to gold nanoparticles?
Yes. Thiol oligos are widely used for gold nanoparticle functionalization through strong sulfur–gold interactions.
Can thiol modifiers be placed internally?
Yes. Internal thiol placement may be possible using thiol-bearing nucleosides, internal thiol linkers or flexible thiol spacers.
Is HPLC purification recommended?
 HPLC purification is commonly recommended for modified and conjugated thiol oligos, especially for post-synthetic conjugation or high-performance assay applications.
Can Bio-Synthesis support custom thiol linkers?
 Yes. Bio-Synthesis can evaluate custom thiol linkers, PEG spacers, protected thiol designs, dual handles and customer-supplied building blocks.
More FAQ'sAll FAQ's
Contact & Quote Request

Need help choosing the right thiol modifier?

Send your sequence, desired thiol position, intended conjugation partner, scale, purification preference and QC requirements. Bio-Synthesis can recommend the appropriate thiol modifier, protection strategy, linker length and conjugation chemistry for your application.
Request a Quote Speak to a Scientist

Need help before quoting?

Email: info@biosyn.com
Phone: 800-227-0627 (US/CAN)
Phone: +001-972-420-8505 (INT)

What to Send

  • Oligo sequence and orientation
  • SH position: 5′, 3′, internal or multiple
  • Protected or free thiol preference
  • Payload, surface or conjugation partner
  • Scale, purity target and QC needs

What We Review

Our team evaluates synthesis feasibility, thiol protection, linker spacing, conjugation chemistry, purification strategy and final analytical release needs.

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.
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