Helix-coil stability constants for the naturally occurring amino acids in water. XIII. The presence of by-products in amino-acid analysis of copolymers and their effect on the guest parameters; recomputed values of σ and s for L-serine
✍ Scribed by J. W. Van Nispen; D. J. Hill; H. A. Scheraga
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 1977
- Tongue
- English
- Weight
- 315 KB
- Volume
- 16
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
Abstract
Previously used procedures for processing the amino acids from 6__N__ hydrochloric acid hydrolysis of poly[N^5^‐(4‐hydroxybutyl)‐L‐glutamine], poly[N^5^‐(3‐hydroxypropyl)‐L‐glutamine], and several random copolymers derived from these, led to the formation of spurious products. These have been isolated and characterized as the γ‐ester of glutamic acid and the hydroxyalkyl amine, and chloro‐alkyl amine hydrochloride. The former reduces the observed values for glutamic acid, but the latter has no effect on them. A method is used to avoid formation of these artifacts in the amino‐acid analysis. Of all the copolymers studied previously in this series, the compositions of only those containing L‐serine are in error as a result of the formation of the γ‐ester. A redetermination of the amino‐acid compositions of the copolymer fractions studied earlier leads to slightly revised values for the Zimm‐Bragg parameters σ and s of serine.