HCG

What is HCG?

HCG is a dimer glycoprotein: two non-covalently bonded protein chains that together form a single complex, with a total molecular mass of approximately 36,700 Da. The compound is known under CAS number 9002-61-3. The α-subunit has ninety-two amino acid residues; the β-subunit is specific to this compound. Approximately one-third of the molecular mass consists not of amino acids but of carbohydrate chains, and this glycosylation largely determines the folding and stability of the intact complex.

Because it is a large, glycosylated protein with two subunits, there is no single empirical formula as with small molecules: the carbohydrate chains vary in composition, meaning the mass is a distribution rather than a single number. This is precisely what makes HCG an instructive model compound within protein chemistry — it is a well-documented example of a heterodimeric glycoprotein in which subunit assembly, disulfide bridges, glycan heterogeneity, and mass distribution can be analytically studied. For the same reason, the content is expressed in international units (IU) rather than milligrams: that is the standard unit of specification for this type of glycosylated protein.

Applications in a laboratory context

Within protein and peptide chemistry and analytical work, HCG is found in the following in vitro research areas, among others:

• Structure-activity relationship research to the contribution of the individual subunits and of the carbohydrate chains to the folding, assembly, and thermal stability of the intact complex.
• Protein and peptide chemistry research towards solubility, aggregation behavior, and subunit dissociation of heterodimeric glycoproteins under varying pH and salt conditions.
• Enzymatic stability studies in which the sensitivity of the protein chains and glycan structures to degradation in vitro is systematically compared.
• Analytical method development and validation (HPLC, LC-MS, peptide mapping) where the material serves as a reference standard for intact mass determination, glycan profiling, and content determination in international units.

Specifications

Shape, handling and storage

The material is supplied as freeze-dried powder (lyophilisate) in a sealed glass vial with a rubber septum and aluminium shrink cap, in two research sizes: 5,000 IU and 10,000 IU. The lyophilisate is white to off-white and hygroscopic. The vial remains closed and in the original packaging until the material is processed in the laboratory.

Store the closed lyophilisate at 2–8 °C, in a dark and dry place, protected from light and moisture. Because the two subunits are non-covalently bonded, the complex is sensitive to mechanical stress: swirl a liquid sample gently rather than shaking it vigorously, and avoid repeated freeze-thaw cycles. Furthermore, handle the material with the usual laboratory precautions: a clean working environment, gloves and eye protection, and disposal of residual material according to applicable guidelines.

Analytical quality

HCG is a glycosylated protein standardized to international units (IU); an HPLC purity percentage, as is common for short synthetic peptides, is not the appropriate measure for this type of compound, because the glycan heterogeneity cannot be represented as a single sharp peak. The material is therefore supplied under a controlled specification, with documentation regarding the content and identity of the supplied batch. The available certificates of analysis can be viewed on our website. lab results page.

Important disclaimer

We supply this product strictly for laboratory research and analytical work. It is not intended for diagnostic or therapeutic applications, and expressly not for use in humans or animals. This product is not a foodstuff, a supplement, a cosmetic product, or a registered medicinal product. By purchasing this product, the purchaser confirms that they are 18 years of age or older and will use the product exclusively within a controlled research or laboratory environment.