H-Lys-pNA · 2 HBr

H-Lys-pNA · 2 HBr is a lysine-based amino acid derivative bearing a p-nitroanilide (pNA) chromogenic leaving group, provided as a dihydrobromide salt that enhances handling of the basic side chain. The structure contains the α-amino and α-carboxyl functional motif of L-lysine, while the ε-amino group is converted into the p-nitroanilide functionality, creating a defined amide linkage and a strongly electron-withdrawing nitro substituent on the aniline ring. The salt form increases aqueous solubility and stabilizes the protonated ε-amide environment, which can influence enzyme recognition and reaction kinetics in analytical formats. The p-nitroanilide moiety is designed for measurable color development upon cleavage, making the compound a practical biochemical and synthetic intermediate for lysine-targeted substrate and labeling chemistries.

1. Enzyme Substrate Assays

H-Lys-pNA · 2 HBr is used in enzyme activity screening and mechanistic studies where lysine-directed proteases, amidases, or peptidase-like catalysts can cleave the p-nitroanilide linkage to generate a spectroscopically detectable p-nitroaniline signal. The L-lysine backbone provides a stereodefined recognition element, while the ε-amide-to-pNA design translates cleavage events into quantifiable colorimetric readouts. The dihydrobromide salt form supports reproducible preparation in buffered aqueous media by maintaining protonation states of the lysine-derived functionality during assay setup. Downstream, the same substrate logic can guide selection of substrate analogs for process monitoring and comparative enzyme characterization in biochemical research and industrial biocatalysis workflows.

2. Protected Amino Acid Building Block

H-Lys-pNA · 2 HBr functions as a lysine-derived protected amino acid derivative in synthetic organic chemistry when the pNA amide serves as a stable handle for controlled transformations of the ε-position. The compound's defined stereochemistry at the α-carbon and the presence of a carboxyl group enable conversion into activated intermediates for peptide coupling strategies, while the ε-amide can be retained or selectively manipulated depending on the desired product profile. The salt counterions can be leveraged to improve handling and facilitate stepwise protection-group strategies that keep the reactive amine functionality masked during coupling. Generated downstream derivatives include lysine-containing peptide fragments, chromogenic peptide analogs, and intermediate scaffolds for constructing larger amide-rich molecules with lysine side-chain functionality.

3. Peptide Coupling Chemistry

H-Lys-pNA · 2 HBr is applicable to peptide building block preparation and fragment assembly where lysine side-chain incorporation is required with a built-in chromogenic reporter element. The α-carboxyl functionality can be activated for amide bond formation, while the ε-p-nitroanilide motif can be carried through coupling sequences to produce lysine-containing peptide substrates or standards. The stereochemical integrity of the L-lysine framework supports consistent incorporation into peptide chains used for structure-activity relationship studies and sequence-dependent enzyme investigations. Downstream utility includes synthesis of peptidomimetic constructs, analytical peptide standards, and substrate libraries that translate specific cleavage or binding events into measurable spectroscopic outputs.

4. Analytical Research Standards

H-Lys-pNA · 2 HBr is used to develop analytical research assays and reference materials that rely on p-nitroaniline generation for sensitive, time-resolved detection. The pNA chromophore provides a direct optical handle, while the lysine-derived structural context improves relevance to lysine-recognizing enzymatic systems and lysine-directed binding motifs. The dihydrobromide salt form supports consistent solubilization and reproducible assay conditions, which can be important for method development and comparative studies across reagent lots. Downstream derivative formation includes calibration reagents, enzyme specificity probes, and chromogenic substrate panels used in biochemical characterization and quality-oriented process studies.

5. Specialty Chemical Synthesis

H-Lys-pNA · 2 HBr can serve as a chiral amino acid-based intermediate for specialty chemical production where lysine functionalization and amide construction are central steps. The compound's lysine framework provides a stereodefined scaffold bearing a carboxyl-derived functionality and an ε-amide linked to a nitroaniline reporter, enabling downstream transformations into functional amide derivatives, labeled intermediates, or chromophore-containing building blocks. The presence of the nitroanilide group supports further synthetic elaboration through standard organic chemistry operations while maintaining a defined structural motif for downstream detection or conjugation. Broader relevance extends to industrial fine chemical synthesis routes that require lysine-derived, chromogenic-functional intermediates for method development, analytical reagent manufacture, and specialized biochemical tool generation.

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