Peptide Modifications

PEG and lipid architectures can alter hydrodynamic size, protein association, clearance, and proteolytic exposure.

• Select attachment site and linker length carefully.
• Evaluate potency after adding a bulky or hydrophobic group.
• Plan LC-MS and HPLC methods for heterogeneous or high-mass constructs.

Spectral compatibility, dye charge, hydrophobicity, and attachment position can strongly affect signal and peptide behavior.

• Match excitation and emission to available instrument channels.
• Use a spacer when the dye may interfere with binding.
• Protect a unique attachment site to avoid mixed labeling products.

A defined isotope label supports accurate peak-area normalization while retaining the native peptide sequence and chemistry.

• Place the label in a residue retained in the monitored fragment.
• Avoid labels near likely metabolic or cleavage sites when inappropriate.
• Specify isotopic enrichment, purity, and quantity requirements.

Affinity tags simplify enrichment, while orthogonal handles provide more control over orientation and coupling chemistry.

• Use a spacer to improve tag accessibility.
• Choose cleavable or reversible capture when recovery is required.
• Avoid placing the tag within a critical binding epitope.

Membrane interaction can be increased through charge and hydrophobicity, but the optimal balance is sequence and application dependent.

• Evaluate solubility and aggregation before scale-up.
• Consider a cleavable linker when the delivery group may impair activity.
• Test multiple lipid or spacer lengths when possible.

Chemically defined PTM peptides provide controlled standards and substrates that are difficult to obtain from biological sources.

• Specify the exact modified residue and positional isomer.
• Include modified and unmodified controls when appropriate.
• Choose purification and storage conditions compatible with the PTM.

Orthogonal handles improve site definition and reduce unintended reactions with native peptide functional groups.

• Choose copper-free chemistry for sensitive biological payloads.
• Confirm handle compatibility with protecting groups and purification.
• Define which partner carries each complementary reactive group.