The Science Behind
Amino Acid Fingerprinting
Our 4-zone test system uses classical analytical chemistry techniques that have been used in laboratories worldwide for decades.
Why Fingerprinting Works
Every peptide has a unique amino acid composition. By testing for different classes of amino acids, we create a "fingerprint" pattern that can help identify what peptide is in your sample.
For example, Semaglutide contains arginine (detected by Sakaguchi) and tyrosine (detected by Xanthoproteic), but no cysteine (negative Lead test). This pattern is different from TB-500, which lacks arginine and aromatic amino acids.
While this cannot provide the same level of detail as mass spectrometry or HPLC, it offers a quick, accessible way to verify that your sample matches the expected profile of your target peptide.
The Chemistry
Bradford Assay
Coomassie Brilliant Blue G-250 dye binding
Principle
The Bradford assay uses Coomassie Blue dye that shifts from brown to blue when it binds to protein/peptide. The blue color intensity correlates with protein concentration. This confirms that your sample contains peptide material.
Detects
General protein/peptide presence
References
- Bradford, M.M. (1976) Analytical Biochemistry
Sakaguchi Reaction
Alpha-naphthol + sodium hypobromite reaction
Principle
The Sakaguchi reaction specifically detects the guanidino group found in arginine residues. A red-orange color develops when arginine-containing peptides react with alpha-naphthol in the presence of an oxidizing agent. Many GLP-1 agonists and other important peptides contain arginine.
Detects
Arginine-containing peptides
References
- Sakaguchi, S. (1925) Journal of Biochemistry
Lead Acetate Test
Lead sulfide precipitation
Principle
Sulfur-containing amino acids (cysteine, cystine, methionine) release sulfide ions when heated with alkali. These ions react with lead acetate to form black lead sulfide precipitate. This helps identify peptides with disulfide bonds or sulfur-containing residues.
Detects
Cysteine, cystine, methionine
References
- Standard biochemical assay
Xanthoproteic Test
Nitric acid nitration of aromatic rings
Principle
Concentrated nitric acid nitrates the benzene ring of aromatic amino acids (tyrosine, tryptophan, phenylalanine), producing yellow-colored nitro compounds. The intensity of yellow color indicates the presence and relative amount of aromatic residues.
Detects
Tyrosine, tryptophan, phenylalanine
References
- Classical organic chemistry test
Limitations
What this is: A qualitative screening tool for identity verification based on amino acid composition.
What this is not:
- A purity test - cannot determine exact percentage purity
- A sequencing tool - cannot confirm exact amino acid order
- A replacement for HPLC/MS - professional lab analysis is more definitive
- A contaminant detector - may not detect all possible impurities
- A medical diagnostic - for research and personal use only
For definitive analysis, we recommend submitting samples to an accredited analytical laboratory. Our test provides a useful first-line screening that can help identify obvious issues before you proceed.
Smartphone Colorimetry
We're developing a companion app that uses your phone's camera to analyze test results. This will enable semi-quantitative analysis and automatic fingerprint matching against our database.
Stay Updated on Our Research
Get notified about new test capabilities and smartphone colorimetry features.