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Custom PACE phosphonoacetate linkage engineering for ASO, gapmer, siRNA, splice-switching and advanced RNA-targeting programs requiring deliberate control of backbone stability, charge behavior, protein interactions and pharmacological performance.
Phosphonoacetate (PACE) is an engineered internucleotide backbone linkage that introduces an acetate-bearing phosphonate group into the chemical connection between adjacent nucleotides. PACE reengineers the linkage region—not the nucleobase or sugar—and can change the local charge distribution, steric environment, nuclease recognition and protein interactions while preserving sequence-directed hybridization.
PACE may be introduced at selected positions, patterned across a sequence, or combined with phosphodiester, phosphorothioate and sugar-modified nucleotides. Its effects are design dependent: sequence context, linkage position, modification density, modality, conjugation and formulation can all influence hybridization, RNase H or RNAi compatibility, cellular behavior and pharmacology.
The internucleotide linkage connecting neighboring nucleotides—from a conventional phosphate environment to an acetate-bearing phosphonate linkage.
Selected PACE placement may improve biological stability relative to unmodified phosphodiester regions.
Linkage pattern may influence serum persistence, exposure and tissue distribution.
PACE changes the local steric and charge environment and may alter nonspecific protein binding.
PACE can be evaluated in ASO, gapmer, siRNA, splice-switching and conjugated architectures.
Backbone redesign may support candidate optimization, but safety must be confirmed for the complete construct.
Evaluate PACE placement to tune serum persistence, protein interaction, tissue exposure and overall pharmacological behavior.
Use phosphonoacetate as a distinct linkage option beyond conventional phosphodiester and phosphorothioate chemistries.
Assess PACE in gapmer ASOs, steric-blocking oligonucleotides, siRNA constructs and other RNA-targeting programs.
Bio-Synthesis supports sequence review, defined linkage placement, mixed-backbone designs, purification and analytical characterization.
Use the tabs to compare PACE with native phosphodiester and phosphorothioate backbones, then review placement guidance for gapmer, steric-blocking, RNAi and conjugated designs.
Native phosphodiester linkages provide the natural anionic backbone. PACE introduces a phosphonoacetate-containing linkage that adds a different steric and electronic environment while retaining sequence-programmed recognition.
Design interpretation: PACE is an additional optimization lever—not a universal replacement for native PO linkages. Effects on stability, protein interaction, distribution and activity depend on sequence and placement.
Both are anionic, but PACE redistributes charge and steric presentation around phosphorus.
Selected PACE placement may improve resistance relative to unmodified PO regions.
Compatibility is architecture dependent; preserve a suitable DNA gap when cleavage is required.
Evaluate PACE together with sugar chemistry, conjugation and formulation.
Phosphorothioate replaces a non-bridging oxygen with sulfur and commonly increases nuclease resistance and protein binding. PACE introduces an acetate-bearing phosphonate linkage and can be used as a complementary linkage rather than an interchangeable substitute.
Practical approach: mixed PS/PACE patterns should be designed as a complete architecture because linkage order, density, stereochemistry, purification and analytical resolution are interconnected.
PS often increases protein binding; PACE may alter that interaction profile differently.
Both chemistries can add phosphorus-centered complexity that may affect product heterogeneity.
Mixed-linkage patterns can change chromatographic behavior and impurity separation.
Evaluate side-by-side patterns instead of assuming one linkage can replace the other position-for-position.
The number and position of PACE linkages should reflect whether the oligonucleotide must recruit RNase H, load into RISC, block a splice site, or carry a targeting conjugate.
Preserve an RNase H-compatible DNA gap; evaluate PACE in selected wing or transition positions.
Use affinity and stability requirements—not RNase H cleavage—as the main placement constraints.
Protect RISC recognition, strand selection and duplex geometry while testing stability gains.
Coordinate PACE placement with GalNAc, lipid, peptide or terminal-label manufacturing.
Begin with one or a small number of defined PACE positions when sequence-specific behavior is unknown.
Compare PO, PS and PACE variants with identical sequence and formulation whenever possible.
Measure RNase H, RNAi or steric-blocking function independently from nuclease stability.
Modification count and mixed-linkage composition should be reflected in the mass and purity strategy.
Consider expanded base pairs when natural Watson-Crick recognition does not provide enough information capacity, orthogonality or chemical diversity.
Expanded genetic alphabets, synthetic biology, aptamer selection, molecular diagnostics, data storage and protein engineering research.
PACE is most useful when its placement is planned as part of the complete oligonucleotide architecture. The wing chemistry, central gap, linkage pattern and conjugation strategy must work together to preserve target recognition and the intended mechanism of action.
Use LNA, BNA, cEt, 2′-MOE, 2′-OMe or other affinity-enhancing sugars to stabilize target binding and protect the oligonucleotide ends.
For RNase H-active gapmers, retain a sufficiently long DNA region with duplex geometry compatible with RNase H1 recruitment and RNA cleavage.
Introduce PACE selectively in wing, transition or other evaluated positions rather than assuming uniform placement will preserve activity.
Coordinate GalNAc, lipid, peptide, fluorophore or other terminal conjugates with the linkage pattern, purification route and analytical strategy.
Application-first design: PACE should not be placed by a single universal rule. Start with a defined architecture, use matched PO or PS controls, and confirm the required biological mechanism independently from nuclease-stability gains.
PACE can be evaluated across multiple RNA-targeting modalities. The optimal linkage pattern depends on the biological mechanism, sequence architecture, delivery strategy and required analytical controls.
PACE chemistry can be evaluated in antisense programs for RNA knockdown, transcript modulation and therapeutic candidate optimization.
mRNA and lncRNA targeting
Mixed-backbone optimization
Target-validation studies
Preclinical ASO development
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PACE may be incorporated into gapmer architectures to tune stability and pharmacology while preserving an RNase H-compatible DNA gap.
RNase H-compatible design
Modified wing strategies
PS/PACE mixed linkages
Target RNA degradation
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PACE-containing duplexes can be assessed for stability and delivery compatibility while maintaining strand selection, RISC loading and silencing activity.
siRNA stability optimization
LNP and ligand compatibility
Guide/passenger strand design
In vivo persistence studies
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PACE may support steric-blocking and splice-modulation programs that require improved stability without RNase H-mediated cleavage.
Exon skipping or inclusion
Pre-mRNA targeting
Steric-blocking mechanisms
Rare-disease research
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Application design note: PACE should be evaluated as part of the complete oligonucleotide architecture. Sequence, linkage density, sugar chemistry, conjugation and formulation can all influence biological performance.
Bio-Synthesis combines advanced backbone-linkage development, scientific design review, analytical characterization and cGMP-aligned manufacturing practices for research, preclinical and advanced development programs.
PACE projects are supported from early feasibility through scale-up with documented manufacturing and fit-for-purpose analytical release.
Defined PACE patterns, mixed-backbone designs and customer-specific architecture review.
RP-HPLC, IE-HPLC, LC-MS, HR-LC-MS, MALDI-TOF and project-specific testing.
Guidance on linkage placement, mechanism preservation, purification and QC.
Process continuity from feasibility quantities through larger development supply.
PACE is one component of a broader oligonucleotide engineering toolbox. Explore complementary linkage, backbone, sugar and therapeutic-development services.
Overview of linkage modification and complete backbone-replacement technologies.
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Defined phosphorus stereochemistry for antisense and structure–activity studies.
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Phosphorus–nitrogen backbone-linkage reengineering for custom oligonucleotides.
Charge-neutral internucleotide chemistry for hybridization and stability studies.
Charge-neutral peptide-like backbone architecture for high-affinity recognition.
Phosphorodiamidate backbone technology for steric-blocking designs.
RNase H-active architectures combining advanced sugar and backbone patterns.
Steric-blocking oligonucleotides for exon skipping and pre-mRNA modulation.
LNA, BNA, ENA, cEt, 2′-O-NMA, 2′-AmNA and UNA design options.
Integrated synthesis, conjugation, analytical characterization and scale-up support.
PACE phosphonoacetate backbone chemistry should be discussed within the broader scientific context of therapeutic oligonucleotide backbone engineering, ASO pharmacology, RNase H activity, nuclease resistance, and delivery optimization.
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