A tesamorelin label can look straightforward until a laboratory record, calculation sheet, or certificate of analysis needs to be reconciled. The tesamorelin CAS number molecular weight, molecular formula, and listed salt form should agree across those records. When they do not, the issue is often not the peptide sequence itself. It is usually a question of how the material is named, expressed, or measured.

Core Tesamorelin Chemical Identifiers

Tesamorelin is a synthetic peptide based on growth hormone-releasing hormone research. It is commonly described as a 44-amino-acid peptide analog and is handled in laboratory settings as a high-molecular-weight peptide reagent rather than as a small molecule.

The primary identifiers generally used for tesamorelin are CAS number 218949-48-5, molecular formula C221H366N72O67S, and molecular weight 5135.9 g/mol. More precise references may report the molecular weight as approximately 5135.85 g/mol. The difference is simply a matter of rounding and should not affect ordinary molar calculations.

These numbers serve different functions. The CAS number is a standardized registry identifier used to reduce ambiguity in catalogs, records, and procurement systems. The molecular formula describes the elemental composition of the peptide. Molecular weight converts a weighed amount of material into an amount of substance, which is essential when a research method calls for a defined molar concentration.

A CAS number is a useful starting point, but it is not a quality certificate. It does not establish purity, peptide content, residual solvents, moisture level, or analytical identity for a specific vial. Those conclusions require batch-level documentation and appropriate analytical testing.

Why CAS Number 218949-48-5 Matters

Peptide names can be inconsistent across research papers, supplier catalogs, and internal laboratory notes. A registry number creates a more stable reference point. Searching or documenting tesamorelin under CAS number 218949-48-5 helps distinguish it from related GHRH-based materials, experimental analogs, blends, and products with similar naming conventions.

For purchasing teams and independent researchers, the CAS number is particularly useful during three stages: initial catalog comparison, incoming-material verification, and record retention. It provides a common identifier that can be checked against a supplier specification, certificate of analysis, and laboratory inventory entry.

That said, CAS matching alone is not enough. A label may correctly state the CAS number while leaving open practical questions about lyophilized mass, acetate content, assay basis, or the method used to determine purity. A complete material review considers the CAS number alongside the formula, molecular weight, stated form, lot number, and available analytical documentation.

Tesamorelin Molecular Weight and Molar Calculations

The reference molecular weight of tesamorelin is approximately 5135.9 g/mol. This value reflects the peptide itself and allows researchers to translate mass into molar amounts. Because tesamorelin is a large peptide, even a milligram-level mass represents a relatively small number of micromoles.

For example, one milligram of tesamorelin corresponds to approximately 0.195 micromoles when calculated using 5135.9 g/mol. The conversion follows the standard relationship: amount in moles equals mass in grams divided by molecular weight in grams per mole. The arithmetic is simple, but the material basis must be clear before a calculated concentration is treated as exact.

This distinction matters most when comparing a nominal vial amount with an assay result. A vial labeled by peptide equivalent may not be interpreted in the same way as a bulk mass measurement of a salt-containing, lyophilized material. If a controlled laboratory method requires tightly defined concentrations, use the supplier’s stated assay basis and the relevant batch documentation rather than assuming every listed milligram refers to identical material composition.

Molecular weight is also useful for evaluating analytical data. In mass spectrometry, intact-peptide results may be reported as multiply charged ions rather than one simple molecular-ion peak. The expected deconvoluted mass should align closely with the tesamorelin reference mass, subject to instrument tolerance, adduct formation, sample preparation, and the reporting convention used by the laboratory.

Formula, Salt Form, and What Can Change on Paper

The commonly reported formula, C221H366N72O67S, describes the tesamorelin peptide structure. It contains carbon, hydrogen, nitrogen, oxygen, and sulfur, with the sulfur arising from the peptide’s amino acid composition. Formula confirmation supports identity work, but it does not replace a method such as HPLC or LC-MS for evaluating an actual research sample.

Salt form is where product listings can appear inconsistent even when they refer to the same underlying peptide. Tesamorelin may be discussed as tesamorelin or tesamorelin acetate. Acetate is relevant because the peptide can be supplied as an acetate salt, and salt-associated components can affect how a manufacturer reports material weight, net peptide content, and product specifications.

A supplier may therefore state the standard molecular weight of the tesamorelin peptide while separately identifying the material as an acetate salt. Another supplier may describe its specification in terms of peptide content or a salt-adjusted value. Neither presentation should be accepted or rejected on wording alone. The appropriate interpretation depends on the certificate of analysis, stated assay method, and whether the listed quantity is a peptide-equivalent amount or total bulk material mass.

Water content is another practical variable. Lyophilized peptides can retain moisture, and hygroscopic handling can change measured mass after a container is opened. That does not change the molecular weight of the peptide structure, but it can affect gravimetric handling and concentration accuracy. For controlled evaluations, researchers should use documented storage conditions, minimize unnecessary exposure, and apply their laboratory’s established procedures for solution preparation and material tracking.

What to Verify Before Using Tesamorelin as a Research Reagent

A reliable identity review begins with the label. Confirm that the product name, CAS number 218949-48-5, molecular weight near 5135.9 g/mol, and stated form are internally consistent. Then compare those identifiers with the certificate of analysis for the specific lot.

For a high-purity peptide reagent, HPLC is commonly used to report chromatographic purity, while LC-MS or an equivalent mass-based method can support identity confirmation. These results answer different questions. HPLC helps evaluate the relative purity profile under the stated test conditions. Mass analysis helps establish that the observed material matches the expected peptide mass. A purity percentage without a clear testing method provides less value than a complete, lot-specific record.

Researchers should also inspect whether a supplier differentiates between assay, purity, and content. These terms are often used casually in peptide commerce, yet they are not interchangeable. Purity describes the proportion of a chromatographic signal under a defined method. Assay can describe measured active peptide content. Content may account for salt, water, or other material characteristics. The documentation should make clear what each reported number means.

For PEPTAS SHOP purchasers selecting tesamorelin for controlled laboratory evaluations, the practical objective is straightforward: match the material specification to the requirements of the research plan. If the work depends on molar precision, preserve the lot documentation with the calculation record. If the work is comparative, keep the same material basis and handling conditions across samples. Consistent documentation is often more valuable than a single impressive specification line.

A Better Way to Record Tesamorelin in the Laboratory

A clear inventory entry prevents confusion months after purchase. Record tesamorelin by its full name, CAS number 218949-48-5, reference molecular weight of 5135.9 g/mol, formula C221H366N72O67S, supplier lot number, stated salt form, and the date received. Include the certificate-of-analysis reference and any storage observations that could affect subsequent handling.

When preparing calculation sheets, identify whether the mass used is label claim, assay-adjusted peptide content, or directly measured bulk mass. This one line of context can prevent a misleading concentration calculation from being carried into later work. It also makes the experiment easier to review, reproduce, and compare with future lots.

The best tesamorelin record is not the longest one. It is the one that lets another qualified researcher identify exactly what material was used, how its molecular weight was applied, and which lot-specific data supported the work.