H-Cys(SO3H)-OH · sodium salt

H-Cys(SO3H)-OH · sodium salt is the sodium salt form of a cysteine derivative in which the thiol functionality is presented as a sulfonic acid (SO3H) substituent on the cysteine side chain, while the molecule retains a free amino group and a carboxylic acid. The structure therefore combines a chiral amino acid backbone with a strongly polar, anionic sulfonate motif that behaves differently from native thiols in oxidation state and nucleophilicity. The presence of the carboxylate and sulfonate groups increases water compatibility and supports salt-state handling during synthesis, purification, and downstream coupling chemistry. The sulfonic acid side chain can participate in acid-base equilibria and can serve as a stable functional handle for amino acid derivatization, ionic patterning, and controlled incorporation into peptide-like or biomolecule conjugate frameworks.

1. Peptide Synthesis

H-Cys(SO3H)-OH · sodium salt is applicable to peptide synthesis workflows where a cysteine-derived side-chain functionality is required without thiol oxidation sensitivity. The amino acid backbone supports standard amide bond formation at the alpha-carboxyl group, while the SO3H/sulfonate side chain provides a highly polar, anionic residue that can influence local solubility and electrostatics in peptide sequences. Protection-group strategies can be designed around the free amino and carboxylate functionalities, enabling conversion to appropriately protected derivatives for coupling while preserving the sulfonate motif through subsequent steps. Downstream, peptide building blocks containing this residue can be used to generate sulfonate-bearing peptides and peptide analogs for structure-function investigations and materials-oriented peptide constructs.

2. Chemical Biology

H-Cys(SO3H)-OH · sodium salt can be used in chemical biology research requiring stable, water-soluble anionic side chains for studying biomolecular recognition and charge-dependent interactions. The sulfonate side chain provides a persistent negative charge that can mimic aspects of phosphorylated or carboxylated motifs while avoiding redox chemistry associated with thiols. The amino acid's chiral center enables stereochemically defined incorporation into peptide scaffolds, supporting structure-activity relationship studies focused on how side-chain charge distribution affects binding and conformational preferences. Conjugation strategies can leverage the amino acid backbone to introduce sulfonate-containing linkers into biomolecule-modifying reagents, enabling downstream formation of labeled or functionalized biomolecular probes.

3. Bioconjugation Chemistry

H-Cys(SO3H)-OH · sodium salt is suitable for bioconjugation chemistry where a sulfonate-functional amino acid is needed to tune hydrophilicity, reduce nonspecific adsorption, or create defined ionic interfaces on conjugates. The molecule's amino and carboxy functionality can be transformed into activated derivatives for amide coupling to carrier proteins, peptides, or polymer backbones, while the sulfonate group remains stable under conditions that may otherwise compromise thiol-based handles. The sodium salt form supports reproducible salt-state behavior during conjugate preparation and can help maintain solubility of conjugates containing multiple anionic groups. Downstream products include sulfonate-bearing conjugate linkers and biomolecule-modified constructs used in analytical research, reagent development, and platform building for further functionalization.

4. Process Chemistry Intermediate

H-Cys(SO3H)-OH · sodium salt functions as a practical amino acid-based intermediate for industrial and process chemistry routes that require incorporation of a sulfonate side chain with robust stability. The strong polarity of the SO3H group supports aqueous handling and can reduce variability associated with redox-active sulfur species during multi-step manufacturing. The compound's defined amino acid stereochemistry and functional-group pattern enable conversion into protected amino acid derivatives or coupling-ready forms that align with peptide-manufacturing and fine-chemical synthesis practices. Downstream, this intermediate can be used to prepare sulfonate-containing building blocks for peptide analog production, charged linker synthesis, and scalable preparation of functional amino acid derivatives used in applied chemical manufacturing.

5. Analytical Research Standards

H-Cys(SO3H)-OH · sodium salt can be employed in analytical research as a reference material for monitoring sulfonate-bearing amino acid derivatives, peptide fragments, or conjugate linkers. The presence of both carboxylate and sulfonate groups gives characteristic ionization behavior that can support LC-MS or capillary electrophoresis method development and calibration for charged analytes. The chiral amino acid backbone allows stereochemically defined standards when enantiopure incorporation into peptides or derivatized intermediates is required for method validation. Downstream, the compound can serve as an internal or external standard for quantifying sulfonate-containing species generated during peptide coupling, deprotection, or conjugation workflows, supporting reproducible analytical characterization in research and manufacturing environments.

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