D-Homocystine is a sulfur-containing, non-proteinogenic amino acid derivative composed of two D-homocysteine units linked by a disulfide bond, forming a homocystine disulfide dimer with a total of two amino groups and two carboxyl groups. Each homocysteine subunit bears a side-chain thiol that is oxidized to the disulfide, and the molecule retains the D stereochemical designation at the α-carbon while presenting the disulfide as the primary redox-active structural feature. In biochemical and synthetic workflows, D-homocystine is used as a defined disulfide-containing substrate or precursor for preparing sulfur redox analogues and for studying disulfide exchange, thiol/disulfide interconversion, and related peptide or protein chemistry under controlled conditions.
D-Homocystine is the disulfide-linked dimer of the d-configured amino acid side chain, corresponding to a homocysteine-derived thiol pair that is locked as a cystine analog. The molecule contains two stereogenic centers on the amino acid backbone (d-configuration) and a central disulfide bond that governs redox stability, while the free amino acid functionality is typically presented as a diacid/diamine framework suitable for conversion into protected derivatives. The disulfide can participate in controlled thiol-disulfide exchange under nucleophilic or reducing conditions, enabling downstream formation of thiol-bearing intermediates for peptide and bioconjugation chemistry. The chiral amino acid composition and disulfide architecture make D-Homocystine a structurally defined building block for stereochemically controlled sulfur-containing motifs and for synthetic routes that require a protected sulfur handle.
1. Peptide Disulfide Building
D-Homocystine is applied in peptide synthesis strategies that require sulfur-sulfur connectivity, where the disulfide core can serve as a cystine-like element for forming intramolecular or intermolecular S-S patterns in peptide scaffolds. The homocysteine-derived side chains provide a longer sulfur spacing compared with cystine, which can influence folding propensity and conformational constraints when incorporated into peptide sequences. The disulfide bond can be introduced as a pre-assembled motif or transformed into thiol equivalents for subsequent coupling and controlled reoxidation, supporting peptide coupling chemistry that is compatible with standard amide-forming steps. The resulting sulfur-rich peptide analogs can be used to probe disulfide topology effects in sequence design and to generate defined redox-responsive peptide materials. D-Homocystine thus functions as a stereochemically specified sulfur building block for disulfide-containing peptide construction.
2. Chemical Biology Redox Probes
D-Homocystine is suitable for chemical biology research focused on redox-state manipulation and thiol/disulfide exchange studies, leveraging the chiral disulfide architecture as a defined sulfur redox handle. The disulfide linkage supports controlled conversion to thiol-bearing species, which can be used to model or perturb protein-like redox microenvironments in vitro. The amino acid backbone enables derivatization into conjugatable forms, including attachment to electrophiles or linkers that target biomolecular residues while maintaining stereochemical definition. The downstream thiol or disulfide derivatives can be employed as probes for monitoring exchange kinetics, mapping redox-active pathways, or generating redox-sensitive linkages in molecular tools. D-Homocystine therefore supports amino acid-based redox probe preparation and mechanistic studies in sulfur chemistry.
3. Bioconjugation Linker Chemistry
D-Homocystine is used in bioconjugation workflows that require a stable yet transformable disulfide-containing linker for connecting biomolecules to functional payloads. The disulfide bond provides a chemical motif that can remain intact during coupling steps and can later undergo thiol-disulfide exchange to enable intracellularly or chemically triggered remodeling of the conjugate. The d-configured amino acid framework can be incorporated into linker designs where stereochemical consistency is required for reproducible conjugate properties and for constructing defined sulfur spacing. The molecule can be converted into activated derivatives for amide coupling, thioester formation, or thiol release strategies, enabling downstream attachment to peptides, proteins, or polymer backbones. D-Homocystine thus serves as a chiral sulfur-containing intermediate for constructing disulfide-bridged bioconjugates and modular conjugation reagents.
4. Chiral Sulfur Intermediate Synthesis
D-Homocystine is applied as a chiral sulfur-containing intermediate for synthetic organic chemistry routes that require stereodefined thiol or disulfide functionality. The disulfide core can be selectively reduced to generate thiol equivalents, which can then undergo further functional group transformations such as alkylation, acylation, or incorporation into heteroatom-containing motifs. The homocysteine-derived side chain length supports access to sulfur chemistry with tunable steric and electronic properties relative to cystine analogs, which can matter for building thioether, thioester, sulfenamide, or thioamide derivatives. The amino acid backbone also enables conversion into protected amino acid derivatives for sequential coupling steps in multi-component syntheses. D-Homocystine therefore supports chiral intermediate preparation for downstream sulfur-functionalized molecules and stereocontrolled synthesis.
5. Analytical Standard And Method Development
D-Homocystine is suitable for analytical research and method development where defined disulfide-containing amino acid standards are required for calibration, identification, and redox-speciation workflows. The presence of a chiral, disulfide-linked homocysteine dimer provides a chemically distinct reference material for chromatographic or mass spectrometric discrimination of sulfur redox species. The disulfide can be transformed into characteristic thiol forms under controlled conditions, enabling derivatization-based quantification strategies that distinguish between oxidized and reduced states. The amino acid framework supports compatibility with derivatization chemistries used for amino acid profiling and sulfur metabolite analysis. D-Homocystine thus functions as a stereochemically defined analytical reference and a feedstock for developing redox-aware analytical methods.
6. Pharmaceutical Intermediate Manufacturing
D-Homocystine is relevant to pharmaceutical intermediate preparation where controlled sulfur functionality and stereochemical definition are required for manufacturing routes toward disulfide-containing building blocks. The disulfide bond provides a handle for late-stage conversion into thiol-reactive intermediates or for installation of redox-stable linkages in peptide-like or peptidomimetic scaffolds during process chemistry. The amino acid backbone can be protected and deprotected in a manner consistent with protected amino acid synthesis and peptide coupling compatibility, supporting scalable synthesis of sulfur-rich intermediates. The chiral d-configuration can be maintained through protecting-group strategies that minimize racemization during conversion to activated derivatives. D-Homocystine therefore serves as a chiral sulfur-containing intermediate for industrial fine chemical synthesis and downstream production of disulfide-structured molecular entities.
2. Emu oil in combination with other active ingredients for treating skin imperfections
5. SERS spectrum of the peptide thymosin‐β4 obtained with Ag nanorod substrate
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