C-Terminal Modified Peptide Synthesis

C-terminal modifications can induce properties of peptides or proteins, which makes them very useful tools in research and therapeutic industries. CD Formulation provides a variety of peptide C-terminal modification services, including amidation, esterification, PEGylation, and post-translational modification. In addition, our C-terminal modification services also can be used to produce labeled peptides with specific functions, such as biotin peptides and fluorescently labeled peptides.

C-Terminal Modification Necessity

The C-terminus, also called the carboxyl terminus or C-terminus, is the end of an amino acid chain where the last amino acid in the sequence has a free carboxyl group (-COOH). In general, the C-terminus determines how a peptide interacts with other molecules, including enzymes and proteins. By modifying this terminus, scientists can improve the physicochemical properties of a peptide to increase its stability or create new functional properties, including:

• Enhanced stability.
• Improved biocompatibility.
• Improved cellular uptake.
• Regulating biological activity.
• Providing labels and probes.

Fig. 1 The recent strategies for C-terminally modified peptides. (Arbour CA, et al., 2020)

Explore Our Custom C-Terminal Modified Peptide Synthesis Services

As experts in peptide modification, CD Formulation provides unparalleled peptide C-terminal modification services to customers around the world. We have reliable synthesis procedures and excellent peptide analysis technology to solve any possible challenges in developing and producing peptide therapeutics.

Our team of peptide modification experts can perform a variety of C-terminal modifications, including amidation, esterification, and the addition of various functional groups or labels. Importantly, we can also perform more complex modifications, including the attachment of lipids, polymers, or other molecules.

The following are the C-terminal modification options that CD Formulation can provide:

Amide (NH2)

C-terminal amide modification involves converting the carboxyl group (-COOH) at the end of the peptide chain into an amide group (-CONH2). When the C-terminus of the peptide is modified to a carboxamide, the negative charge of the carboxylic acid is removed and the hydrophobicity of the molecule is increased, thus its activity is increased. This carboxamide subsequently forms hydrogen bonds, mimicking the native protein and reducing its vulnerability to carboxypeptidases, thereby increasing its stability. In addition, the cell permeability of the C-terminally amidated peptide is increased.

Aldehydes

C-terminal aldehyde modification refers to the introduction of an aldehyde group (-CHO) at the carboxyl terminus of a peptide. This modification can be done by chemically introducing an aldehyde group directly into the C-terminus of a peptide, thereby changing its physicochemical properties, enhancing its biological activity, or for subsequent functionalization steps. Aldehyde peptides are inhibitors of proteases such as serine, aspartate, cysteine, and metalloproteinases, which can be used as key intermediates in the process of synthesizing pseudo peptides.

Esters

C-terminal ester modification is a common chemical modification method, which refers to the introduction of an ester group at the carboxyl terminus of a peptide to change its physical and chemical properties, thereby changing its stability, solubility, and biological activity. Since C-terminal esters are key targets for cleavage by endogenous esterases, these molecules can be used as prodrugs. If the methyl ester is located on the C-terminal cysteine residue, the peptide can be used to study protein prenylation.

Biotin

Biotinylation of peptides is an effective technique for binding specific peptides to streptavidin-coated surfaces. This modification can be synthesized at the N-terminus or the C-terminus. At the C-terminus, the primary epsilon amino group on lysine is biotinylated to remove the positive charge of lysine. Biotinylated peptides are often used in immunoassays and fluorescence-based flow cytometry.

Fluorescent Labeling

p-Nitroaniline (pNA) and 7-amino-4-methylcoumarin (AMC) are the most widely used chromogenic and fluorogenic substrates for C-terminal modification. These fluorescently labeled peptides can be used to study the activity, rate, and selectivity of proteolytic enzymes.

p-Nitroaniline (pNA)	Peptide p-nitroanilide is a compound used to study protease activity.
AMC (7-amino-4-methylcoumarin)	AMC is linked to the peptide via an amide bond formed between the coumarin amine and the carboxyl group on the C-terminal residue. AMC-based enzyme substrates are a common tool for studying protease activity and specificity. Common excitation/emission wavelengths are 342/441 nm.

Design Your C-Terminally Modified Peptide

When performing C-terminal modification, our peptide modification experts will focus on the following key factors to ensure that the peptide modification solution is designed to meet your needs and expected effects:

• Charge: The charge at the C-terminus affects the solubility of the peptide and its interaction with the target molecule.
• Modification Type: Different C-terminal modifications are designed according to the purpose of the peptide, such as enhancing stability, improving biocompatibility, and improving drug delivery efficiency. Modifications such as pNA and Amc are useful in activity assays.
• Modification Position: Determine whether the modification at the C-terminal position affects the structure, stability, and binding ability of the peptide chain with the target protein.
• Sequence Compatibility: Some modifications, such as aldehydes or chloromethyl ketones, may not be suitable for all peptide sequences.
• Steric Hindrance: Some C-terminal modifications may increase the molecular volume of the peptide or introduce additional chemical groups, thereby affecting its spatial conformation and further affecting its binding to the target molecule.
• Stability: Some modifications, such as amides and esters, enhance the stability of the peptide, which is crucial for therapeutic peptides.
• Synthesis Method: Optimize the synthesis route to increase the yield and purity of the modified peptide to ensure that it can meet the needs of large-scale production.

Peptide Manufacturing & Analytical Services

In addition to peptide synthesis capabilities, CD Formulation combines flexible GMP manufacturing facilities with cutting-edge peptide analytical knowledge to provide a full range of quality control testing services to accelerate the commercialization of your products, including:

Publication

CD Formulation has extensive experience in custom peptide synthesis with C-terminal modifications. Each synthesis step is subject to our strict quality control. Please don't hesitate to contact us if you want to learn more about the possibilities of incorporating C-terminal modification into your peptides. We look forward to cooperating with you.

How It Works

STEP 1

Submit a service request describing your specific research or development need.

STEP 2

We'll email you to provide your quote and confirm order details if applicable.

STEP 3

Execute the project with real-time communication, and deliver the final report promptly.