40+ years of excellence in custom synthesis and bioconjugation services.
Calculators, design tools, and educational content to support your research.
Engineering internucleotide linkages and alternative backbone architectures for next-generation oligonucleotides.
Natural DNA and RNA use a repeating phosphodiester backbone. For advanced research, diagnostic, and therapeutic designs, that backbone can be stereochemically controlled, chemically modified, or completely replaced to alter stability, charge, recognition, cellular behavior, and biological mechanism.
Bio-Synthesis supports six major backbone platforms: chiral phosphorothioate (Rp/Sp), methylphosphonate, phosphonoacetate (PACE), phosphoramidate, peptide nucleic acid (PNA), and Morpholino (PMO/TMO).
Platform distinction: Chiral PS, methylphosphonate, PACE, and phosphoramidate modify the phosphorus-containing backbone. PNA and Morpholino replace the natural sugar-phosphate architecture with alternative scaffolds.
Choose the primary objective to see the backbone chemistries commonly considered for that goal.
Click a design goal to update the recommendation.
The preferred starting point for RNase H-compatible antisense and gapmer development. Stereodefined phosphorothioate patterns can improve control over nuclease stability, protein interactions, potency, and therapeutic performance.
Mechanism
Stability
Charge
Design Level
A neutral phosphorus-containing backbone used when reduced charge, altered electrostatic behavior, and strong nuclease resistance are desired. It can support steric-blocking, diagnostic, and surface-hybridization designs.
PACE is considered when advanced backbone engineering, strong nuclease resistance, and emerging therapeutic performance are priorities. It may be combined with other chemistries in sequence- and position-specific designs.
TNeutral alternative backbones are usually the strongest starting point when the goal is to occupy a target site and block translation, splicing, or regulatory binding without recruiting RNase H.
PNA is often the primary recommendation for high-affinity hybridization, mismatch discrimination, clamp designs, and FISH. Methylphosphonate or chiral PS may also be considered when handling, stability, or charge effects are important.
Therapeutic programs require a balance of potency, stability, delivery, manufacturability, impurity control, and analytical release. Chiral PS is often preferred for RNase H-active ASOs, while PNA and Morpholino fit steric-blocking programs.
Click any backbone chemistry below to compare its structure, properties, biological mechanism, common applications, and manufacturing considerations. Each panel also links to a dedicated technical guide.
Replacing one non-bridging phosphate oxygen with sulfur creates a stereogenic phosphorus center. Rp/Sp control allows defined stereochemical patterns.
RNase H
Best Known For
View Full Chiral Phosphorothioate Guide →
A methyl group replaces a non-bridging phosphate oxygen, creating a neutral linkage with altered charge and hybridization behavior.
View Full Methylphosphonate Guide →
PACE introduces a phosphonoacetate-derived substituent to balance charge, stability, and biological performance.
View Full PACE Guide →
Phosphoramidate chemistry creates P–N linkages with tunable charge, stability, and recognition properties.
View Full Phosphoramidate Guide →
PNA replaces the sugar-phosphate backbone with a neutral peptide-like scaffold while retaining sequence-specific base recognition.
View Full PNA Guide →
Morpholino oligomers use morpholine rings and nonionic linkages to create highly stable steric-blocking oligos.
View Full Morpholino Guide →
Select the application to see the backbone chemistries most often considered, the preferred biological mechanism, key design priorities, and the main tradeoff to review before synthesis.
For RNase H-active antisense programs, chiral phosphorothioate backbones are the most established starting point. A DNA-like gap supports RNase H recruitment, while stereochemical patterning and affinity-enhancing flanks can improve stability and target engagement.
Fully neutral backbones such as PNA and Morpholino do not support RNase H cleavage.
Steric-blocking oligos bind the target and prevent translation, regulatory-factor binding, or other molecular interactions without degrading the RNA. Neutral alternative backbones are especially well suited to this mechanism.
Affinity
Delivery
Maximum backbone stability does not compensate for poor target accessibility or weak delivery.
PNA is often preferred for high-affinity recognition, mismatch discrimination, clamp designs, and FISH. Methylphosphonate or phosphoramidate may also be considered when reduced charge or specialized surface behavior is important.
Specificity
Labels
Formats
Very high-affinity probes may require stronger wash or hybridization stringency.
Splice-switching oligos require strong, sequence-specific occupancy of pre-mRNA regulatory regions. Morpholino and PNA are widely used because they provide high nuclease resistance and steric-blocking activity without RNase H cleavage.
Target
Delivery can be the dominant limitation even when sequence binding is strong.
Therapeutic programs should select the backbone only after defining the biological mechanism, delivery route, required stability, scale, impurity profile, and analytical release strategy. No single backbone is best for every program.
Scale-Up
QC
The most stable backbone is not necessarily the most developable or effective.
Biosensors and immobilized capture systems may benefit from neutral or reduced-charge backbones that improve hybridization near surfaces and reduce electrostatic repulsion. PNA and methylphosphonate are common starting points.
Surface
Handles
Surface density and linker geometry can matter more than intrinsic duplex affinity.
Chiral PS Rp/Sp
PNA / Morpholino
PNA-led designs
Backbone engineering may be combined with affinity-enhancing sugars, targeting ligands, imaging labels, delivery conjugates, and multifunctional handles.
Affinity-enhanced antisense and gapmer architectures.
Liver-targeted oligonucleotide research.
Imaging, PNA FISH, and diagnostics.
Cell-penetrating and targeted PNA constructs.
Delivery-enhanced steric-blocking constructs.
Neutral probes and biosensor designs.
Emerging delivery research.
Specialty conjugation and multifunctional probes.
Advanced backbone projects often need more than standard synthesis. This streamlined workflow shows how Bio-Synthesis evaluates chemistry feasibility, develops the route, purifies the product, confirms identity and quality, and prepares the program for scale-up.
Each project moves through a defined technical review rather than a collection of separate service cards.
Sequence, backbone pattern, monomer availability, conjugation needs, and intended application are reviewed.
Synthesis conditions, coupling strategy, deprotection, and chemistry-specific process controls are defined.
HPLC or project-specific purification is selected based on backbone, length, charge, and hydrophobicity.
Identity, purity, yield, and chemistry-compatible QC are reviewed before release.
Successful methods are transferred to larger scale with defined documentation, packaging, and handling.
Chiral PS, methylphosphonate, PACE, phosphoramidate, PNA, Morpholino, and combination designs.
HPLC/UPLC, UV quantification, MS where compatible, COA, and project-specific documentation.
Research screening, lead optimization, pilot production, and larger manufacturing campaigns.
Best starting information: sequence, backbone chemistry and placement, intended mechanism, scale, purity target, conjugation requirements, and analytical expectations.
↗
Backbone compatibility, stereochemistry, synthesis route, conjugation, purification, analytical characterization, and scale-up feasibility.
Advanced backbone chemistries require controlled synthesis, purification, analytical review and project-specific documentation. Bio-Synthesis supports research, diagnostic and therapeutic-development programs through an ISO-supported oligonucleotide manufacturing platform.
Bio-Synthesissupports chiral phosphorothioate, methylphosphonate, PACE, phosphoramidate, PNA and Morpholino programs with controlled synthesis, purification, analytical QC, documentation and project-specific packaging.
Sequence-specific route planning for advanced backbone chemistries and analogs.
HPLC and project-specific purification strategies based on chemistry and scale.
COA, analytical traces, UV quantification and MS where compatible.
Aliquoting, packaging, counterion review and scale-up planning.
Trusted by biotech leaders worldwide for over 45+ years of delivering high quality, fast and scalable synthetic biology solutions.