Showing papers in "Journal of Biochemistry in 1969"

Reaction of Fluorescein-Isothiocyanate with Proteins and Amino Acids: I. Covalent and Non-Covalent Binding of Fluorescein-Isothiocyanate and Fluorescein to Proteins

Abstract: 1. The reaction of fluorescein-isothiocyanate (FITC) with proteins was studied under various conditions. 2. It was found that the a-amino groups of the N-terminal amino acids were the prime target of the reaction (at pH<9.5) of FITC with neocarzinostatin and insulin although the a-amino groups became reactive at higher pH. 3. Egg white lysozyme [EC 3.2. 1. 17] and bovine serum albumin were found to bind with FITC even at low pH, while ovomucoid and neocarzinostatin did not bind below pH 7. 4. Trifluoroacetic acid treatment of fluorescein-thiocarbamylated insulin (FTC insulin) resulted in the release of terminal FTH-amino acids (Phe and Gly) only. These FTH-amino acids were identified for the first time. 5. Non-covalent binding of this fluorochrome to proteins was studied with fluoro seein. The results indicated non-covalent dye-binding of the fluorescein with albumin and Iysozyme [EC 3.2.1. 17]. 6. Above results showed that FITC is a useful reagent but that non-covalent dye binding should be born in mind when used with some proteins.