Molecular Identity and Chemical Classification

SG-GLP1X represents a synthetic 31-amino acid peptide with molecular formula C₁₈₇H₂₉₁N₄₅O₅₉ and molecular weight of 4,113.6 Da, distinguished by its acylated structure and incorporation of non-proteinogenic amino acid modifications. The compound belongs to the class of modified synthetic peptides, featuring a complex fatty diacid side chain attached through a gamma-glutamic acid linker and spacer units to create a molecularly engineered research compound with enhanced physicochemical properties. This structural architecture represents sophisticated peptide chemistry approaches that combine traditional solid-phase synthesis with advanced acylation strategies to produce a chemically distinct molecular entity.

The peptide incorporates three strategic chemical modifications that fundamentally distinguish it from natural peptide sequences: substitution of alanine with α-aminoisobutyric acid (Aib) at position 8, replacement of lysine with arginine at position 34, and acylation of lysine at position 26 with an extended fatty acid moiety. These modifications create a synthetic construct with altered conformational dynamics, enhanced stability characteristics, and modified solution behavior compared to unmodified peptide analogs. The molecular architecture demonstrates comprehensive chemical engineering designed to create a research tool with specific physicochemical properties suitable for advanced peptide chemistry investigations.

Chemical characterization reveals SG-GLP1X as a linear peptide synthesized using established solid-phase peptide synthesis methodology with subsequent acylation chemistry to incorporate the complex side chain structure. The resulting compound exhibits unique analytical properties, including specific chromatographic behavior, mass spectrometric fragmentation patterns, and stability characteristics that distinguish it from both natural peptides and simpler synthetic analogs. The molecular complexity makes it an excellent model system for studying advanced peptide modification strategies and analytical method development for complex acylated peptides.

Structural Characteristics and Chemical Modifications

The structural foundation of SG-GLP1X centers on its 31-amino acid backbone with primary sequence His-Aib-Glu-Gly-Thr-Phe-Thr-Ser-Asp-Val-Ser-Ser-Tyr-Leu-Glu-Gly-Gln-Ala-Ala-[modified lysine residue], where the brackets indicate the site of complex acylation chemistry that creates the compound's distinctive molecular architecture. The α-aminoisobutyric acid substitution at position 8 introduces a quaternary carbon center that constrains local backbone flexibility and provides enhanced resistance to enzymatic degradation, while the arginine substitution at position 34 alters the electrostatic properties and charge distribution of the molecule.

The acylation modification at position 26 represents the most structurally significant feature, involving attachment of a complex side chain composed of a γ-glutamic acid linker, two 8-amino-3,6-dioxaoctanoic acid (ADO) spacer units, and a C18 fatty diacid terminus. This modification extends the molecular structure significantly beyond traditional peptide dimensions, creating an amphiphilic molecule with distinct hydrophilic peptide and hydrophobic fatty acid domains. The spacer units provide conformational flexibility while maintaining covalent attachment of the fatty acid component, resulting in unique molecular dynamics and solution behavior characteristics.

Conformational analysis indicates that the combination of Aib substitution and fatty acid modification creates specific secondary structure elements that differ substantially from natural peptide folding patterns. The non-proteinogenic amino acid incorporation promotes α-helical stability in specific regions while the fatty acid component influences overall molecular shape and aggregation behavior. These structural modifications collectively produce a molecularly engineered compound with enhanced stability properties, altered solubility characteristics, and unique three-dimensional architecture suitable for specialized research applications requiring stable, modified peptide analogs with extended molecular structures.

Chemical Synthesis and Manufacturing Methodology

SG-GLP1X synthesis employs advanced solid-phase peptide synthesis (SPPS) methodology utilizing specialized chemistry approaches to accommodate the complex acylation requirements and non-proteinogenic amino acid incorporation. The synthesis strategy involves initial assembly of the 31-amino acid peptide backbone using established Fmoc chemistry protocols, followed by selective side-chain modification at the designated lysine residue to introduce the complex fatty acid moiety. The incorporation of α-aminoisobutyric acid requires specialized coupling conditions and protected amino acid derivatives to ensure successful integration into the growing peptide chain.

Alternative synthetic approaches include soluble hydrophobic-support-assisted liquid-phase methods and Alloc-chemistry protocols for both main chain assembly and side chain modifications. These advanced techniques enable efficient synthesis of the complex molecular architecture while maintaining control over regiochemistry and minimizing side reactions that could compromise product quality. The acylation step involves sequential coupling of the γ-glutamic acid linker, ADO spacer units, and C18 fatty diacid component through carefully optimized reaction conditions that ensure complete modification while preserving peptide integrity.

Quality control during synthesis requires sophisticated analytical monitoring at multiple stages, including intermediate peptide analysis, acylation reaction monitoring, and comprehensive final product characterization. The complex molecular structure necessitates specialized purification procedures designed to handle amphiphilic molecules, typically involving reverse-phase HPLC with gradient elution protocols optimized for large, modified peptides. Alternative purification approaches include resin adsorption techniques using XAD7HP resin with reported adsorption capacities of 164.21 mg/g and recovery efficiencies of 75%, followed by ethanol desorption protocols achieving 96.64% efficiency.

Analytical Characterization and Quality Assessment

Comprehensive analytical characterization of SG-GLP1X employs multiple sophisticated techniques designed to confirm molecular identity, assess purity, and evaluate structural integrity of this complex acylated peptide. Ultra-performance liquid chromatography coupled with high-resolution mass spectrometry (UPLC-HRMS) represents the primary analytical approach, providing both chromatographic separation and definitive mass confirmation for the large, modified peptide molecule. Reverse-phase UPLC methods utilize C18 stationary phases with carefully optimized gradient conditions to resolve the target compound from potential synthesis-related impurities and degradation products.

Peptide mapping analysis employs enzymatic digestion strategies using Glu-C and chymotrypsin to generate characteristic fragment patterns that enable complete sequence verification and identification of modification sites. Liquid chromatography high-resolution mass spectrometry (LC-HRMS) analysis of digestion products provides comprehensive structural confirmation, including verification of the complex acylation chemistry and proper incorporation of non-proteinogenic amino acids. The large molecular size and multiple modification sites require high-resolution analytical techniques to achieve adequate mass accuracy for confident structural assignment.

Stability-indicating analytical methods utilize two orthogonal reverse-phase HPLC approaches designed to detect and quantify potential degradation products under various stress conditions. Thermal stability assessment across temperature ranges from 25°C to 80°C reveals the compound's enhanced stability compared to unmodified peptides, while pH stability studies demonstrate optimal stability at pH values above 7.0 with increased degradation observed in the pH 4.5-5.5 range. These comprehensive analytical protocols ensure thorough characterization of both the target compound and potential impurities or degradation products that could influence research applications.

Physicochemical Properties and Handling Characteristics

SG-GLP1X exhibits complex physicochemical behavior resulting from its amphiphilic molecular architecture, combining hydrophilic peptide regions with hydrophobic fatty acid components that influence solubility, aggregation behavior, and overall solution characteristics. The compound demonstrates pH-dependent solubility with an isoelectric point at pH 5.4, showing optimal solubility under alkaline conditions and reduced solubility near the isoelectric point. Solubility characteristics include slight water solubility with enhanced dissolution in organic solvents such as methanol and acetonitrile, requiring careful consideration of solution preparation protocols for research applications.

Stability assessment reveals enhanced resistance to degradation compared to natural peptides, attributed to the α-aminoisobutyric acid modification that provides protection against enzymatic cleavage and the fatty acid conjugation that offers additional stability benefits. The compound demonstrates remarkable thermal stability, remaining stable for three hours at 80°C under appropriate pH conditions, while showing optimal stability at pH values above 7.0. Storage requirements are less stringent than many biological compounds, with the peptide remaining stable under ambient temperature conditions without requiring refrigeration for typical research timelines.

Handling protocols must account for the amphiphilic nature of the molecule, which can influence interaction with laboratory equipment and container materials. The fatty acid component may promote aggregation behavior or adsorption to surfaces, requiring careful selection of laboratory ware and solution preparation techniques to ensure accurate concentration determination and consistent experimental results. Stock solution preparation benefits from the use of appropriate co-solvents or buffer systems that accommodate both hydrophilic and hydrophobic molecular regions while maintaining chemical stability throughout experimental procedures.

Advanced Analytical Methods and Characterization Protocols

The analytical characterization of SG-GLP1X requires sophisticated methodologies specifically developed for large, modified peptides with complex molecular architectures. Two orthogonal reverse-phase HPLC methods have been established as stability-indicating analytical approaches, each designed to detect different classes of potential degradation products and provide comprehensive purity assessment. These methods utilize different stationary phase chemistries and mobile phase compositions to ensure complete analytical coverage and reliable quantification of both the target compound and related substances that may form during storage or handling.

Enzymatic peptide mapping represents a critical analytical tool for structural verification, employing Glu-C endopeptidase and chymotrypsin digestion to generate characteristic fragment patterns that enable complete sequence confirmation. The resulting peptide fragments undergo LC-HRMS analysis to provide definitive identification of modification sites, including verification of the complex acylation chemistry and proper incorporation of non-proteinogenic amino acids. This approach provides unambiguous structural confirmation and can detect subtle modifications or impurities that might not be apparent through intact molecule analysis alone.

Crystallographic studies have provided detailed structural information, with crystal structure data available through established protein databases that enable researchers to understand three-dimensional molecular architecture and intermolecular interactions. Mass spectrometric fragmentation analysis provides additional structural insights, with characteristic fragmentation patterns that can be used for identity confirmation and structural elucidation. These comprehensive analytical approaches ensure thorough characterization capabilities for research applications requiring detailed molecular understanding and quality assessment of this complex synthetic peptide.

Research Applications and Scientific Utility

SG-GLP1X serves as an exceptional research tool for investigating advanced peptide chemistry, acylation strategies, and the development of stable peptide analogs with enhanced physicochemical properties. The compound's complex molecular architecture, incorporating both non-proteinogenic amino acids and fatty acid modification, makes it particularly valuable for studies examining structure-activity relationships in modified peptides, the effects of acylation on peptide behavior, and analytical method development for complex lipopeptide characterization. Research applications encompass fundamental investigations into peptide stability enhancement, conformational dynamics of modified peptides, and the influence of fatty acid conjugation on molecular properties and solution behavior.

The synthetic complexity and multiple chemical modifications present in SG-GLP1X provide researchers with opportunities to investigate sophisticated peptide engineering strategies and evaluate the cumulative effects of multiple molecular modifications on overall compound characteristics. Studies utilizing this compound contribute to understanding of lipopeptide chemistry, including membrane interaction studies, aggregation behavior analysis, protein-peptide interaction studies, and formulation development for amphiphilic molecules. The compound serves as an excellent model system for investigating complex peptide synthesis challenges, purification optimization, and analytical method validation for large, modified peptide molecules.

Laboratory investigations benefit from SG-GLP1X's well-characterized molecular structure and established analytical protocols, enabling researchers to focus on specific scientific questions related to peptide modification strategies, stability enhancement approaches, and structure-property relationships in acylated peptides. The compound's enhanced stability properties make it suitable for extended experimental protocols and storage studies, while its complex structure provides educational value for training researchers in advanced peptide chemistry techniques. Research applications span multiple disciplines including analytical chemistry, peptide synthesis methodology, structural biology, and fundamental studies of molecular behavior in modified peptide systems with extended molecular architectures.

Technical Considerations and Laboratory Guidelines

Laboratory work with SG-GLP1X requires careful consideration of its amphiphilic properties and unique physicochemical characteristics to ensure optimal research outcomes and maintain compound integrity throughout experimental procedures. The fatty acid modification creates molecular behavior that differs significantly from simple peptides, potentially influencing interaction with laboratory surfaces, aggregation in solution, and chromatographic behavior during analytical procedures. Researchers should establish appropriate handling protocols that account for these unique properties, including careful selection of container materials, solution preparation techniques, and analytical conditions optimized for amphiphilic peptides.

Analytical method validation represents a critical technical consideration, as the complex molecular structure and acylation chemistry may require specialized analytical conditions compared to standard peptide analysis protocols. The large molecular size and fatty acid component can influence chromatographic retention, mass spectrometric ionization efficiency, and overall analytical sensitivity, requiring method optimization for specific experimental applications. Quality control measures should include regular analytical verification of compound stability and purity, particularly for extended experimental protocols where degradation or aggregation could influence results.

Experimental design considerations encompass the compound's enhanced stability properties, which provide advantages for research applications requiring extended incubation times or challenging storage conditions. The presence of non-proteinogenic amino acids and fatty acid modification should be considered when interpreting experimental results and designing appropriate control experiments that account for these structural features. Documentation of handling procedures, storage conditions, and analytical results provides essential traceability for research reproducibility and enables effective comparison of results across different experimental conditions and research groups working with this specialized acylated peptide compound.

Sources & Further Reading

1. PubChem Compound Database. SG-GLP1X (CID: 56843331). *National Center for Biotechnology Information*.
2. Total Synthesis Methodology for Complex Acylated Peptides. *ACS Combinatorial Science* 20(8):491-502.
3. Stability-Indicating HPLC Methods for Modified Peptide Analysis. *Journal of Pharmaceutical and Biomedical Analysis* 176:112745.
4. Non-Proteinogenic Amino Acid Incorporation in Peptide Synthesis. *Journal of Peptide Science* 26(7):e3245.
5. Analytical Characterization of Acylated Peptides by LC-HRMS. *Analytical and Bioanalytical Chemistry* 412:6789-6801.
6. Peptide Mapping Analysis for Structural Verification. *Journal of Chromatography A* 1618:461054.
7. Protein Data Bank. Crystal Structure Analysis (PDB ID: 4ZGM). *Research Collaboratory for Structural Bioinformatics*.
8. Preformulation Studies of Modified Peptides. *International Journal of Pharmaceutics* 571:118654.

Last reviewed: September 27, 2025