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Diss Factsheets

Physical & Chemical properties

Endpoint summary

Administrative data

Description of key information

The physical state:       Insulin human methyl ester is a solid at 20 C.

Melting point:       Melting point could not determined. Thermal transition/ decomposition at 185 -205 °C (read-across data)

Boiling point:       Could not be determined due to decomposition (read-across data)

Relative density:       About 1.342 at 20.1oC for dryed substance (read-across data)

Particle size distribution:       not relevant as only used in suspension

Vapour pressure:       4.9 x 10-6 Pa at 20oC or 25oC (read-across data)

Partition coefficient:       LogPow = approximately 0.4 (estimated at pH 7 .9 for aquaous solution; read-across data).

Water solubility:       very pH dependent with a solubility of about 43 g/L at pH 3.6 and 393 mg/L at pH 7.9. In the interval of pH 4.5-6.5 the substance can be considered as insoluble (read-across data).

Surface tension:       surface tension of a 90% saturated solution: 58.0 mN/m (read-across data)

Flash point:       negligible vapour pressure and consequently will not emit flammable vapours (Read-across data)

Auto-flammability:       No self-ignition observed when heated to 400 ºC (Read-across data)

Flammability:       not flammable (read-across data)

Explosiveness:       not explosive (read-across data)

Oxidising properties:       no chemical groups with oxidising properties in the molecule

Additional information

The molecular structure the target substance is a small protein consisting of 51 amino acids have at least 48 amino acids in common with the source substances (consisting of 50-53 amino acids) and having very identical amino acid sequences.

Based on these structural similarities very similar physicochemical properties would be expected. This is further documented by the results from physicochemical guideline testing for the read-across substances MI3 (S2) and X14DesB30 (S3), where the test results found for melting point, boiling point, flammability, self-ignition, and explosion were identical. The vapour pressure determined for S2 is extremely low but consistent to what would be expected, as a single amino acid on its own has a very low vapour pressure (below 0.4 Pa) and thus, a protein of more than 50 amino acids would have an even lower vapour pressure. Based on these data and the marginal differences in composition between the target and the source chemicals a read-across approach for physicochemical properties using data on S1(Human insulin), S2 and S3 is considered scientifically justified.  

For further details, please refer to read across justification document in section 13