Internal standards are particularly useful for mass spectrometry (MS), especially LC-ES-MS and MALDI-MS in proteomic analyses, allowing the represented peptides and proteins to be quantified. The best internal standards are peptides that have identical sequences as the peptides of Interest and carry stable isotopic labels. Except for the increased mass from the additional neutrons, the stable isotope-labeled (SIL) internal standard and the analyte are essentially indistinguishable, setting the basis for the use of SIL peptides in a variety of applications, such as:

• Reference material for MS experiments in proteomics
• Structure determination by NMR
• Reference material for pharmacokinetic analyses
• Metabolite identification
• Post-translational modified protein quantification
• Verification of outcomes derive from RNAi
• Protein expression tracking
• Cell signal profiling and pathway recognition
• Biomarker discovery

Our SIL Peptide Standards

Creative Proteomics has produced thousands of custom SIL peptide standards. They are labeled with 2H, 13C, and 15N, and with scales and purities surpassing the ever-increasing needs for peptides in the development target assays. Our isotope-labeled MS peptide standards are designed and optimized to provide the best mass spec performance for your MS assay. Design your peptides with the expected mass difference by choosing the plural SIL amino acids. Our SIL peptide standards can be a useful tool for the absolute quantification of complex protein mixtures at a very low concentration.

For products not available in our catalog, we can customize for you using our quality controlled Peptide/Protein Custom Synthesis Service!

Most common stable isotopically labeled amino acids

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