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Isotope Labeled Peptide Synthesis

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Isotope labeled peptides, which retain the same physicochemical properties and chemical reactivity as unlabeled peptides, have long been a staple of NMR spectroscopy studies, mass spectrometry, and pharmacokinetics. CD Formulation offers high-quality, cost-effective, and customized custom isotope-labeled peptide services. Our custom services allow peptide labeling at one or more positions based on a large selection of 2H (deuterium), 15N (nitrogen-15), 13C (carbon-13), or 15N/13C isotope-labeled amino acids.

When Should Isotope-Labeled Peptides Be Used?

Stable isotope-labeled peptides are meticulously crafted by substituting particular atoms within natural amino acids with their heavier isotopic counterparts, a practice that has found extensive application in the realms of nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS), as well as in the evaluations of pharmacokinetics. This intricate synthesis often leverages the economical Fmoc solid-phase method, utilizing uniformly labeled amino acids that boast an impressive isotopic purity exceeding 99%.

Fig. 1 Synthesis of stable isotopically labeled peptides with filter-assisted enzymatic labeling. (Tsai HF, et al., 2017)

Explore Our Custom Isotope Labeled Peptide Synthesis Services

At CD Formulation, we harness a wealth of experience cultivated over decades in the nuanced art of peptide synthesis, conjuring bespoke peptides adorned with stable isotopes. Our tailor-made services dance to the rhythm of your needs, enabling precise labeling at one or multiple pivotal positions. Choose from a diverse arsenal of isotopic wonders, including 2H (deuterium), 15N (nitrogen-15), and 13C (carbon-13).

Our custom stable isotope peptide synthesis service includes:

All stable isotope labeled peptides are optimized for best mass spectrometry performance.
Isotopic purity of all standard heavy peptides is >99%.
In-house amino acid analysis for accurate quantitation.
Individual peptide purities include crude, >75%, >85%, >90%, >95%, and >98%.
Custom sizes and quantities.
Available in 96-peptide array format.
Various isotope labels available, including 2H (deuterium), 15N, 13C, 15N and 13C combinations.

Fig. 2 Isotope labeling of peptide. Fig. 2 Schematic diagram of isotope labeling of peptide. (CD Formulation)

Stable Isotope Labeled Amino Acid Option

CD Formulation offers a comprehensive selection of stable isotope labeled amino acids, with custom options available upon request. Below is a list of some of the most commonly synthesized labeled amino acids:

Amino Acid	Code	Mass Difference	Isotope
Alanine	Ala, A	+ 4Da	U-¹³C₃, ¹⁵N
Arginine	Arg, R	+ 10Da	U-¹³C₆, ¹⁵N₄
Isoleucine	Ile, I	+ 7Da	U-¹³C₆, ¹⁵N
Leucine	Leu, L	+ 7Da	U-¹³C₆, ¹⁵N
Lysine	Lys, K	+ 8Da	U-¹³C₆, ¹⁵N₂
Phenylalanine	Phe, F	+ 10Da	U-¹³C₉, ¹⁵N
Proline	Pro, P	+ 6Da	U-¹³C₅, ¹⁵N
Valine	Val, V	+ 6Da	U-¹³C₅, ¹⁵N
Threonine	Thr, T	+ 5Da	U-¹³C₄, ¹⁵N
Glycine	Gly, G	+ 3Da	U-¹³C₂, ¹⁵N
Asparagine	Asn, N	+ 6Da	U-¹³C₄, ¹⁵N₂
Aspartic Acid	Asp, D	+ 5Da	U-¹³C₄, ¹⁵N
Glutamine	Gln, Q	+ 7Da	U-¹³C₅, ¹⁵N₂
Methionine	Met, M	+ 6Da	U-¹³C, ¹⁵N
Tyrosine	Tyr, Y	+ 10Da	U-¹³C₉, ¹⁵N
Serine	Ser, S	+ 4Da	U-¹³C₃, ¹⁵N

Isotope Labeled Peptide Modification

Isotope-labeled peptides can be modified by different methods to meet the needs of different customers. Common modification methods for stable isotope-labeled peptides are:

Phosphotyrosine, serine, threonine (single or multiple).
Sulfotyrosine (single or multiple).
Methylated arginine, lysine.
Chlorotyrosine.
Methoxylation.
Pyroglutamic acid.

Specifications of Final Delivered Isotope-Labeled Peptide

Specifications	Description
Scale	10 or 40 nmol
Purity	>98%
Labeling	C-terminal, most often R or K (¹³C, ¹⁵N)
Isotopic enrichment	>98%
Formulation	Fully solubilized and in aliquots (1nmol each)
Solvent	5% ACN/water; Concentration: 5 pmole/µl.
Concentration precision	Within 10%
Delivery temperature	On dry ice
Quality control	Liquid chromatography and mass spectrometry
Custom specifications	Upon customer request, supply with other specifications is possible

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:

Peptide identification (ESI-MS).
Peptide Molecular weight determination.
Peptide sequencing.
Peptide quantification/peptide content determination.
Peptide purity and impurity analysis (HPLC/UV).
Amino acid sequence.
Amino acid composition determination.
Net peptide content.

Enantiomeric purity testing (GC/MS; LC).
Residual counterion testing (e.g. TFA).
Elemental analysis.
Residual solvent testing.
Water content testing (GC or KF).
Peptide solubility testing.
Peptide stability testing.

Optical rotation determination.
Bioburden testing(TAMC/TYMC).
Bacterial endotoxin testing.
Sterility testing.
Cytotoxicity testing.
Process/product related impurity testing.
Other pharmacopoeia testing.

Publication

Published Data

Technology: Synthesis of Isotope-Labeled Recombinant Peptide

Journal: Mol Cell Proteomics.

IF: 5.96

Published: 2016

Results:

The authors unveil a dazzlingly intricate methodology for the biosynthesis of peptides affixed with stable isotopes and a quantitative tag, all accomplished within the confines of a cleverly designed in vitro expression system. An Escherichia coli cell-free protein expression system using recombinant elements for protein synthesis was used to synthesize isotope-labeled peptides fused to a Strep-tag. Through a series of optimizations and enrichments, efficient expression of the labeled peptides was achieved and successfully used for multiple reaction monitoring. Using this technique, four isotope-labeled glutathione S-transferase (GST) peptides were synthesized and added to mouse serum as internal standards. Then, quantitative analysis of the synthesized GST peptides confirmed that absolute GST quantification in mouse serum was measurable and reproducible.

Fig. 3 PURE-expressed isotope-labeled peptides. Fig. 2 Design and application of PURE-expressed isotope-labeled peptides. (Xian F, et al., 2016)

CD Formulation is a trusted partner for peptide synthesis. Please don't hesitate to contact us if you are considering using isotope labeled peptides in your project. We look forward to cooperating with you.

References

Tsai HF, Hsiao HH. Synthesis of stable isotopically labeled peptides with filter-assisted enzymatic labeling for the diagnosis of hepatitis B virus infection utilizing mass spectrometry-based proteomics strategy. Anal Chim Acta. 2017 Mar 1;956:32-39.
Xian F, Zi J, Wang Q, et al. Peptide Biosynthesis with Stable Isotope Labeling from a Cell-free Expression System for Targeted Proteomics with Absolute Quantification. Mol Cell Proteomics. 2016 Aug;15(8):2819-28.

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