Methods for Cleaving Peptides from Solid-Phase Resins
Following Fmoc solid-phase peptide synthesis (SPPS), choosing the correct cleavage strategy is critical to maximizing crude purity and retaining delicate structural modifications. Below are the two standard chemical cleavage protocols utilized in our laboratories.
1. Strong Acid Cleavage Method (Standard TFA Protocol)
Dry peptide-conjugated resin is placed in a reaction flask. A cleavage cocktail based on Trifluoroacetic Acid (TFA) supplemented with appropriate organic scavengers is added at a ratio of 10–25 mL/g of resin. The mixture is sealed and agitated via intermittent rotary shaking at room temperature. The resin is filtered, rinsed 2–3 times with fresh TFA, and the filtrates are combined. Ice-cooled diethyl ether (8–10 times the filtrate volume) is added dropwise to precipitate the crude peptide. (Optionally, partial evaporation of TFA under reduced pressure prior to ether addition can optimize precipitation efficiency). The precipitated crude peptide pellet is collected by centrifugation or filtration.
2. Weak Acid Cleavage Method (Dilute TFA or AcOH Protocols)
Protocol A: 1% TFA System
Add 1g of peptide-bound resin to a glass flask containing 1% TFA in Dichloromethane (DCM). Seal and agitate via shaking for 2 minutes. Purge with nitrogen gas to press the filtrate into a separate collection flask pre-charged with 10% pyridine in methanol. Repeat this operational cycle 10 times. Subsequently, rinse the remaining resin sequentially with 30mL DCM and 30mL MeOH three times to wash off residual fully-protected peptides. Monitor the resin washes via TLC or analytical HPLC. Combine all filtrates, concentrate under reduced pressure to 5% volume, add 40mL water, and chill in an ice bath to accelerate precipitation. Filter, wash the collected product 3 times with pure water, and dry in a vacuum desiccator over KOH or P2O5.
Protocol B: Dilute Acetic Acid System
Treat the resin-bound peptide with a cleavage cocktail composed of AcOH / TFE / DCM (ratio 2:2:6) for 2 hours. Filter the resin and rinse three times with the same cleavage solution. Mix the combined filtrates with 15 times the volume of n-hexane, then remove excess acetic acid via rotary evaporation. Recover fully protected peptide fragments according to standard operational workflows.
Peptide Labeling & Modification Classification
Genixpep provides comprehensive modification services at N-termini, C-termini, side chains, and backbones for structural stabilization, cellular imaging, and immunological conjugations.
C-Terminal Modifications
- Amidation (C-terminal Amidation)
- Aldehydes & Alcohols Conversion
- pNA (p-Nitroanilide) / AMC / AFC Labeling
- Cysteamine / Esterification
- N-Alkyl Amides
N-Terminal Modifications
- Acetylation / Formylation
- Palmitoylation / Myristoylation
- Biotinylation (Biotin Labeling)
- Bromoacetylation (Br-Acetylation)
- Chelating Conjugation (DOTA, DTPA, HYNIC)
- Succinylations
Fluorescent & Dye Labeling
- C-Terminus: AFC, AMC, Dap(Dnp), Lys(Dye), pNA, Rh110
- N-Terminus: Bodipy-FL, Cy3, Cy5, Texas Red, 5-Tamra
- General Dyes: FAM, FITC, MCA, Rox, 5-TAMRA, Sulforhodamine 101
Cyclization & Backbones
- Head-to-Tail / Side-Chain Cyclization
- Multiple Disulfide Bonds (S-S Monomer/Trisulfide Control)
- Cyclic-natural peptides / Amide Rings
- Click Chemistry Synthesis
Methylation & Special Side Chains
- Lys(For), Lys(Me), Lys(Me)2, Lys(Me)3, Arg(Me)2
- N-Methylation (N-Me-Ala, N-Me-Asp, N-Me-Glu, N-Me-Leu, etc.)
- Phosphorylation (Phosphoserine, Phosphothreonine, Phosphotyrosine)
- Sulfated Tyrosine or Serine
Immunological Conjugations
- Carrier Protein Conjugation (BSA, KLH, OVA)
- MAPS (Multiple Antigenic Peptide)
- Glycopeptides & PEGylation
- Isotope Labeling (C13, H2, N15)
Premium Custom Modification Price List
Prices listed below are strictly for premium custom modifications per peptide sequence. All values are commercial standard reference rates in USD ($) and scaled for strict laboratory-grade synthesis execution.
| Modification Category & Service Type | 5 mg | 10 mg | 20 mg |
|---|---|---|---|
| N-Terminal Modifications | |||
| N-Acetylation | Free | Free | Free |
| N-Formylation | Free | Free | Free |
| N-Myristoylation / Palmitoylation | $115.00 | $143.00 | $172.00 |
| N-Succinylations | $115.00 | $143.00 | $172.00 |
| N-Biotinylation (Biotin Labeling) | $143.00 | $200.00 | $258.00 |
| N-Terminal Fatty Acid Modification | $115.00 | $143.00 | $143.00 |
| N-Rhodamine B Labeling | $172.00 | $200.00 | $258.00 |
| N-FITC / 5-FAM / 6-FAM | $115.00 | $172.00 | $229.00 |
| N-Bromoacetylated (Br-Acetylation) | $200.00 | $258.00 | $315.00 |
| N-Alkyl Amides Alkylations | $200.00 | $258.00 | $315.00 |
| DOTA, DTPA, Hynic Conjugated Chelators | $258.00 | $343.00 | $458.00 |
| N-BODIPY, Cy3, Cy5 Dye Labeling | Inquire | Inquire | Inquire |
| C-Terminal Modifications | |||
| C-Amidation | Free | Free | Free |
| C-Aldehydes Formulation | $258.00 | $343.00 | $458.00 |
| C-Alcohols Reduction | $258.00 | $343.00 | $458.00 |
| C-Chloromethyl Ketones | $258.00 | $343.00 | $458.00 |