Peptide modification refers to the introduction of new functional peptide sequences at one or both ends of a peptide to obtain multifunctional fusion peptides. This can be achieved through solid-phase synthesis or biosynthesis.
For a list of our available modifications, select the modification options below
Definition and Types of N-terminal Modifications
N-terminal modifications refer to the chemical modification process that occurs at the amino terminal (N-terminus) of proteins or peptide chains. This modification plays an important physiological role in vivo and has extensive application value. Common types of N-terminal modifications include:
N-terminal acetylation: This is one of the most common protein modifications in eukaryotes, where an acetyl group is transferred to the N-terminal amino acid residue under the catalysis of acetyltransferase. Studies have shown that N-terminal acetylation plays a key role in regulating protein stability, acting as a “shield” to protect the proteome from degradation()].
Amino acid residue modification: The N-terminus can be modified by introducing specific amino acids with particular structures. For example, in the design and synthesis of Auristatin analogs, N-terminal modification involves the introduction of amino acids with ฮฑ,ฮฑ-disubstituted carbon atoms, which significantly alters the properties and activity of the compounds()].
Applications and Research of N-terminal Modifications in Different Fields
Applications in Drug Development
In drug development, N-terminal modification is an important means of optimizing the properties of drug molecules. Taking Auristatins as an example, they are synthetic analogs of the anticancer natural product Dolastatin 10 and are potent microtubule inhibitors used clinically as the payload of antibody-drug conjugates (ADCs). Researchers have conducted N-terminal modification on Auristatins, designing and synthesizing several new analogs, including the lead compound PF-06380101. This unprecedented structural modification of peptides has made these analogs exhibit excellent potency in tumor cell proliferation assays, and compared to other synthetic Auristatin analogs used for preparing ADCs, they have different ADME (absorption, distribution, metabolism, and excretion) properties()]. In addition, the crystal structure study of Auristatins with tubulin provides a possible way to investigate their binding modes in detail, revealing that all analyzed analogs adopt a cis conformation for the Val-Dilamine bond in the functionally relevant state bound to tubulin, while this bond is completely trans in solution. This discovery provides valuable tools for structure-based drug design()].
Exploration in Biological Research
In biological research, N-terminal modifications are of great significance for revealing the laws of life activities. In cell cycle research, MS-based experiments analyzing the modification patterns of histones in HeLa cells arrested in G, S, and G/M phases revealed that the core histones were modified similarly in G and S phases, but underwent significant changes during mitosis. Specifically, the phosphorylation levels of histones H3 and H4 increased significantly during mitosis, while the phosphorylation of H2A remained constant throughout the cell cycle; the loss of acetylation was observed for all histones in cells arrested in G/M phase; in G/M phase, the methylation levels of H3 Lys and Lys decreased, while those of H4 Lys increased()]. These dynamic changes provide important clues for a deeper understanding of cell cycle regulation mechanisms. In plant chloroplast research, N-terminal modifications are also closely related to the sorting signals and abundance of the chloroplast proteome, playing an important role in maintaining and regulating the functions of chloroplasts()].
Topic Overview
C-terminal modifications refer to the chemical modification processes occurring at the carboxyl terminus (C-terminus) of proteins or peptide chains. These modifications play a crucial role in regulating protein function, stability, and localization, making them an important area in biomedical research and drug development.
Subtopic Segmentation
Definition and Basic Concepts
Definition: C-terminal modifications refer to the chemical modification processes occurring at the carboxyl terminus (C-terminus) of proteins or peptide chains. These modifications can include acetylation, methylation, ubiquitination, etc.
Special amino acids refer to amino acid derivatives or modified amino acids with unique structures and functions, which play important roles in biological processes, disease treatment, and industrial applications. They are distinct from the 20 common amino acids encoded by the genome and often exhibit specific physiological activities or technical properties through structural modifications or functional adjustments
Stable Isotope Labeled Peptides overview
Stable isotope-labeled peptides are special peptides synthesized by incorporating stable isotopes (such as deuterium (ยฒH), ยนโตN, and ยนยณC). These isotopes do not undergo radioactive decay, thus offering higher safety in experiments and can be used in various research fields.
Main application areas
Stable isotope-labeled peptides have important applications in the following fields:
Nuclear Magnetic Resonance (NMR) Spectroscopy Study
Stable isotope-labeled peptides are important tools in NMR studies. They help scientists reduce spectral complexity and obtain new interatomic correlations by introducing NMR-active nuclei, thereby providing more complete structural information. For example, the combination of ยฒH (deuterium), ยนโตN, and ยนยณC can significantly enhance the resolution of protein structure and dynamics studies.
Protein Structure and Dynamics Analysis
By using stable isotope-labeled peptides, the three-dimensional structure of proteins and their dynamic changes can be determined more accurately. This technique is crucial for studying protein-protein interactions, protein folding, and functional regulation.
Targeted Proteomics and Absolute Quantification
In targeted proteomics, stable isotope-labeled peptides are used as standards for absolute quantification of specific protein expression levels. For example, by combining specific quantitative tag (Qtag) technology, precise quantification of stable isotope-labeled peptides can be achieved, thereby improving the accuracy of protein quantification.
Synthesis and Delivery Services
GenScript offers custom stable isotope-labeled peptide synthesis services, supporting various isotope labeling combinations, including ยฒH, ยนโตN, ยนยณC, or their combinations. These labels can be combined with any peptide modification techniques to meet diverse research requirements.
Deliverables include:
Specified purity and quantity of lyophilized isotopically labeled peptide
Quality control report (HPLC chromatogram, MS spectrum, certificate of analysis)
Protective packaging (such as ArgonShieldโข).
Technical advantages
Stable isotope-labeled peptides have the following technical advantages:
High resolution: Significantly improves the resolution of NMR spectra by introducing isotopic labeling.
Versatility: Can be combined with various peptide modification techniques to meet different experimental requirements.
Precise quantification: Provides high-precision absolute quantification capability in targeted proteomics.
Summary
Stable isotope-labeled peptides are a powerful research tool widely used in fields such as structural biology, proteomics, and drug development. Through the custom services provided by GenScript, researchers can efficiently obtain high-quality labeled peptides, offering reliable support for scientific research.
Fluorescent Peptide Modifications and FRET Pairs
Fluorescent peptide modifications involve the incorporation of fluorescent labels or dyes into peptides to enable detection, tracking, and functional studies. These modifications are widely used in biochemical assays, cellular imaging, drug delivery, and biosensor development. Fluorescently labeled peptides can be used to study enzyme activity, receptor binding, and intracellular signaling pathways. One of the most powerful applications of fluorescent peptide modifications is in ** Fรถrster Resonance Energy Transfer (FRET)** pairs, which allow for the real-time monitoring of molecular interactions and conformational changes 1.
1. Common Fluorescent Modifications for Peptides
Several fluorescent dyes are commonly used for labeling peptides:
FITC (Fluorescein isothiocyanate): Emits green fluorescence and is often used for labeling the N-terminal or lysine side chains.
FAM (5-carboxyfluorescein): Similar to FITC but with higher fluorescence intensity and better photostability.
Rhodamine (e.g., TAMRA, Rhodamine B): Emits red fluorescence and is often used as a FRET acceptor paired with FAM.
Cy3 and Cy5: Cyanine dyes that emit in the red and far-red regions, respectively, and are ideal for multiplex fluorescence imaging.
Dansyl: Emits blue-green fluorescence and is often used in studies involving hydrophobic environments.
BODIPY: Known for high photostability and brightness, suitable for long-term imaging experiments.
AMC (7-amino-4-methylcoumarin) and AFC (7-amino-4-trifluoromethylcoumarin): Fluorogenic substrates used in enzyme activity assays 1.
2. FRET Pairs in Peptide Studies
FRET is a non-radiative energy transfer mechanism that occurs between two fluorophores (donor and acceptor) when they are in close proximity (typically 1โ10 nm). In peptide-based FRET systems, the donor and acceptor are typically attached to different positions on the same peptide or to two interacting peptides. This technique is especially useful for studying:
Protease activity: FRET-based substrates can monitor protease cleavage in real time.
Conformational changes: FRET can detect structural changes in peptides or proteins upon ligand binding or post-translational modifications.
Molecular interactions: FRET is used to study proteinโprotein interactions, DNAโprotein interactions, and receptorโligand binding 1.
3. Synthesis and Application Examples
Fluorescent peptides are typically synthesized using solid-phase peptide synthesis (SPPS), where fluorescent dyes such as Fmoc-Lys(FITC)-OH, Fmoc-Lys(Biotin)-OH, or Fmoc-Lys(Dansyl)-OH are incorporated during the synthesis process. These labeled peptides can be further purified using HPLC and used in various applications:
Enzyme substrate development: Fluorescent peptides are widely used as substrates for proteases, kinases, and other enzymes.
Cellular imaging: Labeled peptides can be used to visualize specific cellular structures or track internalization pathways.
Drug delivery systems: Fluorescently labeled peptides can monitor the delivery and release of therapeutic agents.
Biosensors and diagnostics: FRET-based biosensors can detect biomarkers, ions, or small molecules in real time 1.
4. Custom Synthesis Services
Many companies offer custom synthesis of fluorescently labeled peptides, including:
PEGylated peptides: Peptides modified with polyethylene glycol (PEG) for enhanced solubility and stability.
Multi-labeled peptides: Peptides with multiple fluorescent labels or modifications for advanced imaging and FRET studies.
Cyclization and crosslinking: Introduction of disulfide bridges or other crosslinks to stabilize peptide structures.
Conjugation to carriers: Peptides conjugated to KLH, BSA, or OVA for immunological studies 1.
In conclusion, fluorescent peptide modifications, especially when used in FRET pairs, provide powerful tools for studying biological processes at the molecular level. These techniques are essential in modern biochemical and biomedical research, enabling real-time monitoring of dynamic interactions and enzymatic activities.
Peptide conjugates refer to composite structures formed by chemically or biologically linking peptide chains with other functional molecules (such as nanoparticles, metal chelators, drugs, fluorescent probes, etc.). These structures have broad applications in the biomedical field, including targeted drug delivery, molecular imaging, diagnostic reagents, and radiotherapy.
1ใ Cyclic modifications
The main types of enhancing peptide stability and biological activity through cyclic structures include:
End to end cyclization: The N-terminus and C-terminus of the peptide chain are directly connected to form a cyclic structure.
Stapled Peptides: Stabilize the alpha helix structure through special crosslinking agents (such as hydrocarbon chains), enhancing cell penetration and resistance to degradation.
Side chain looping:
Lactone/lactam ring: side chain carboxyl group condenses with amino group to form
Disulfide/diselenide cyclization: Cysteine (Cys) or selenocysteine (Sec) is oxidized to form a single or multi ring structure (such as 2-3 disulfide bonds).
Click on Chemical Cyclization: The azide and alkyne groups efficiently construct triazole ring 1 through Huisgen cycloaddition reaction.
Aromatic bridging: using xylene or mesitylene as the connecting arm 1.
Application value: Cyclization significantly prolongs the half-life of peptides in vivo, reduces immunogenicity, and is a key strategy for the development of anti-tumor/antiviral drugs12.
2ใ PEGylation modification
Coupling polyethylene glycol (PEG) chains to peptides to improve solubility and pharmacokinetics:
Common PEG molecular weights:
Small molecule PEG: PEG โ, PEG โ, PEG โ, PEG โโ, PEG โโ, PEG โโ
Large molecule PEG: PEG โโโโ, PEG โ
โโโ, PEG โโโโ, PEG โโแด, PEG โโแด 1.
Coupling site:
N-terminal amino modification (such as acetylation, biotinylation)
Side chain amino (lysine) modification (such as succinylation, fatty acid) 12.
Function: Reduce renal clearance rate, enhance water solubility, and reduce toxicity.
3ใ Multi antigen peptide system (MAPS)
Tree like multi branched structure for vaccine design:
Carrier protein coupling:
Keyhole hemocyanin (KLH), bovine serum albumin (BSA), and ovalbumin (OVA) are used as carriers to enhance immunogenicity.
Application: Build an efficient antibody production platform suitable for tumor vaccines and pathogen antigen presentation.
4ใ Other special modifications
Fatty acid modification:
Myristoxylated and Palmitoylated – enhance peptide membrane penetrability.
Methylation modification:
Side chain methylation: Lys (Me) โโโ, Arg (Me) โ (symmetric) D-Tyr(Me)
N-terminal methylation: N-Me Arg, N-Me Phe, etc. – regulates protein interactions.
Sulfonation modification: Sulfated Tyrosine – affects signaling pathway 2.
Peptoid is referring to a class of compounds synthesized chemically to structurally mimic natural peptides but with a modified backbone. Its key feature is replacing the ฮฑ-amino group of amino acids in natural peptides with N-substituted glycine residues, thereby retaining a peptide-like structure while improving stability, biological activity, or pharmacokinetic properties.
Case Study
Fluorescent Modification Case studies
Fluorescent peptide labels have numerous research applications, and GenScript has extensive experience synthesizing peptides with a variety of modifications.
Case Study 1
Sequence: LYRLGLGH
Modification: MCA/DNP
Quantity: 1-4 mg
Required purity >98%
Estimated Turnaround time:17days
Case Study 2
Sequence: IKDLSKEERLWEVQRILTALKRKLREA
Modification: 5-FAM (N-terminal)
Quantity: 10-14 mg
Case Study 3
Sequence: RAKWNNTLKQIASK
Modification: FITC-Ahx (N-terminal)
Quantity: 5-9 mg
26-O-acyl ฮฒ-amyloid (1-42) click peptide was successfully synthesized, the ฮฒ-ester bond in which can be quickly and quantitatively converted to a native Gly25-Ser26 amide bond via a pH-dependent O-N intramolecular acyl migration reaction (t1/2 =1 min, pH7.4, 37โ) at a hydroxyamino acid residue. Namely, upon this pH-triggered conversion (pH-click), the non-aggregative and water-soluble precursor (click peptide) can produce the monomer with a random-coil structure under physiological conditions (pH7.4, 37โ). The structure information is as follows.
ฮฒ-amyloid (1-42) click peptide
Scheme 2: ฮฒ-amyloid (1-42) click peptide
Result
ฮฒ-amyloid precursor(click peptide) has a water solubility of 15 mg/ml, while it is only 0.14 mg/ml for the native peptide.
The aggregative property of the peptides reduced significantly.
The O-acyl moiety was stable under acidic pH.
The following are HPLC reports of (Scheme 3) purified ฮฒ-amyloid (1-42) native peptide converted from ฮฒ-amyloid (1-42) click peptide (precursor) and (Scheme 4) purified 26-O-acyl ฮฒ-amyloid (1-42) click peptide (precursor).
Case Study
With proven technical capability and state-of-the-art in-house instruments and technologies, we have successfully synthesized many peptoids.
Modification: C-Terminal: Amidation
Purity: 94.7%
Theoretical MW: 892.95
Observed MW: 892.6
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