Mercaptoethanesulphonic acid as a protecting and hydrolysing agent for the determination of the amino acid composition of proteins using an elevated temperature for protein hydrolysis

✍ Scribed by János Csapó; Zsuzsanna Csapó-Kiss; Staffan Folestad; Anna Tivesten

• Publisher: Elsevier Science
• Year: 1994
• Tongue: English
• Weight: 574 KB
• Volume: 289
• Category: Article
• ISSN: 0003-2670
• DOI: 10.1016/0003-2670(94)80013-8

✦ Synopsis

Mercaptoethanesulphonic

acid (ME!%OH) (3 M) was used for the hydrolysis of different samples (pure proteins, free tryptophan and milk powder with a high sugar content). Different temperatures (160, 170 and 180°C) and time periods (15-90 min) were compared under standard conditions to minimize side-reactions in order to obtain the best recovery of the amino acids (especially tryptophan and methionine). The materials used for testing the hydrolysis methods were bovine ribonuclease, lysoxyme, cytochrome c, free tryptophan and mare's milk powder. Hydrolysis at high temperature was successfully applied for the amino acid analysis of milk powder with high contents of carbohydrate and pure proteins. In some instances, such as in tryptophan and methionine determination at NO-170°C for 15-30 min, the results were better than those obtained by the original MES-OH method. A disadvantage of the MES-OH hydrolysis method is that it reduces cystine to cysteine, which co-elutes with proline from the ion-exchange column used to separate the released amino acids and it may interfere with the determination of proline in high-cystine proteins.