Difficult & Hydrophobic Peptide Synthesis

Difficult Peptide Synthesis | Hydrophobic Peptide Customization | Difficult Peptide Synthesis | Cluster Sequence Synthesis | Science-Peptide

Peptide sequence too hydrophobic? Aggregate easily? Multiple pairs of disulfide bonds? Science-Peptide's Difficult Peptide Synthesis and Hydrophobic Peptide Synthesis services specialize in all kinds of "can't get it done". 20 years of experience, special solvent systems, stable delivery. Please feel free to contact us.

What kind of peptides are considered "difficult"?
Having been in the peptide synthesis business for 20 years, I have seen all kinds of difficult peptides. When customers come to us, they have already asked several companies, and the answer they get is either "I can't do it" or "Try it, no guarantee".

Peptide with strong hydrophobicity: transmembrane region, signal peptide, hydrophobic amino acid, when synthesized, it will be clumped together on the resin, and the amino acid behind it will not be able to enter.
Peptides that are easily aggregated, such as amyloid and antimicrobial peptides, are piled up when synthesized and clog the column when purified.
Peptides with multiple pairs of disulfide bonds: more than three pairs, one wrong step in the pairing order and the whole molecule is ruined.
Long peptide: more than 60 amino acids, each step of the yield is decreasing, and in the end nothing left.
Complex combination of modifications: phosphorylation, fluorescence, cyclization, and conditions that fight each other.
We can take them all, and it's not "try", it's "have a plan".

1. Hydrophobic peptides: with specialized solvent systems
The difficulty of hydrophobic peptides lies in the fact that they cannot be dissolved in conventional solvents, and when synthesized, the peptide chain "clumps together" on the resin, making it impossible for the amino acids behind it to enter.

Our solution:
Special solvent combination: DMF, NMP, DCM mixed system, plus a little liquid release agent, so that the peptide chain has been kept stretched.
Temperature optimization: some reactions are better at 40°C than room temperature, some have to be lowered to 0°C, we have tried them one by one.
Resin selection: Use high solubility resin for hydrophobic peptides to leave enough space for peptide chains.
Solubilized labels: If you can't, add a hydrophilic label and cut it off after synthesis.

Real case: a 35aa transmembrane peptide, hydrophobic amino acids accounted for 70%, the customer looked for three companies can not be done. We changed the solvent system and added solubilizing label, finally the purity was 92%, and the customer did the structure study smoothly.

2. Multiple pairs of disulfide bonds: no luck, strategy
The more disulfide bonds there are, the harder it is to pair them. Two pairs are fine, but three or more pairs, and one wrong step and it's all over.
Our Strategy:
Orthogonal protection: Cys can be opened and paired in steps using different protecting groups, such as Trt, Acm, tBu.
Optimization of oxidation conditions: air oxidation, glutathione oxidation, iodine oxidation, different methods for different peptides.
Intermediate QC: After each pair, take a sample for MS and confirm the pairing before moving on.
MS/MS confirmation (optional): final break-up with secondary mass spectrometry to see where the disulfide bonds are actually attached.

A real case: A conotoxin peptide containing four pairs of disulfide bonds was rejected by many companies. We designed a four-step oxidation strategy, which took six weeks, and delivered >90% purity, correctly paired disulfide bonds, and the crystal structure was subsequently solved by the customer.

3. Aggregation-prone peptides: synthesizing while defending
Some peptides naturally love to aggregate, such as amyloid protein and antibacterial peptide. They start to aggregate when they are synthesized, block the column when they are purified, and cannot be dissolved when they are in hand.
Our solution:
Pseudoproline: Pseudoproline is introduced at Ser/Thr position to disrupt the aggregation tendency and change back after synthesis.
Segmental synthesis: Peptides that are too polymerized are cut into several segments and synthesized separately, and then reconnected at the end.
Optimization of purification conditions: high temperature, acidic pH, addition of organic solvents to find conditions that make it non-polymerizing.

4. Complex modifier combinations: conditions without fights
Some peptides have multiple requirements: phosphorylation, fluorescent labeling, and cyclization. These modifications may conflict with each other - for example, phosphorylation is acid-phobic, fluorescent labeling is light-phobic, and cyclization requires a specific pH.
Our approach:
Conservation strategy design: which trim to do first, which trim to do later, designed in advance.
Orthogonal conditions:The conditions of each step of the reaction do not affect the modifications already made.
Intermediate QC: After each step of modification, take a sample to make sure it is done correctly before moving on.

5. Purity: Depending on What You Are Doing with It

Each peptide is accompanied by an HPLC and MS report, making the purity data transparent.

1. We've been doing this for 20 years
Difficult Peptide Synthesis is not something that anyone can do. Over the years, we have handled a lot of difficult peptides: transmembrane proteins, viral fusion peptides, conotoxins, amyloid proteins, antimicrobial peptides, etc. We have a good idea of which sequences are prone to problems, and which conditions are able to save them. At least you don't have to try every single one of them if you come to us for difficult and Hydrophobic Peptide Synthesis.

2. It's not "try", it's "have a program".
A lot of companies take on difficult peptides and say, "We'll try it, but we don't guarantee it". We don't play that way. Before accepting an order, we will evaluate the sequence, what is the proportion of hydrophobic amino acids, whether there is any known aggregation tendency, how many pairs of disulfide bonds, and whether the modification is complex or not. After evaluation, we will tell you: what is the success rate and how long is the cycle time.

We don't take orders that can't be done, and we have to hand over orders that we have taken.

3. Specialized solvent systems for hydrophobicity
Hydrophobic peptide is our strong point. If the conventional solvent cannot be dissolved, we will change the solvent; if the conventional temperature does not react, we will adjust the temperature; if the conventional resin does not hold out, we will change the resin. There is also the solubilizing label as a back way out.

4. Multiple pairs of disulfide bonds, step-by-step
If there are more than three pairs of disulfide bonds, we will take a step-by-step approach: the first step is to protect A and open the first pair; protect B and open the second pair; protect C and open the third pair. After each step, we take samples for MS and confirm the pairing before moving on. Finally, the MS/MS will be broken and verified, and the data will be given to you without your guessing.

5. Quality control: data at every step
Quality control of difficult peptides needs to be more careful:
Intermediate QC: After each fragment and each step of modification, measure the purity and molecular weight first.
End product: HPLC for purity, MS for molecular weight.
Solubility test: Provide recommended solvents and solubilization methods, so that you do not get peptides that do not dissolve.
Doing difficult and Hydrophobic Peptide Synthesis, the data speaks for itself, every step can be traced.

• Delivery form: lyophilized powder, centrifuge tubes or vials.
• Accompanying documents:COA (HPLC profile + MS spectrum), synthesis report (optional).
• Optional tests: peptide content, endotoxin, moisture, amino acid composition, solubility test.
• Customized Packaging: portioning and marking according to your requirements.
• Every difficult and Hydrophobic Peptide Synthesis product is reviewed to ensure the sequence is correct and the purity is up to standard before it is sent out.

Whether you have been rejected by others, or you can't do it in your own lab, you can talk to us. If you are looking for Science-Peptide to do difficult and Hydrophobic Peptide Synthesis, at least you don't have to try one by one.

I need you to tell me:
Peptide sequence (or target information)
Have you had anyone else do it before? What's the result?
How much (milligrams)
purity requirements

When do you want it?

Give you a feasibility assessment and program quote within 24 hours.