This Article Full Text (PDF) References Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to Saved Citations Download to citation manager Request Permissions Request Reprints Add to My Marked Citations Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Marmer, W. N. Articles by Farrell, H. M. Search for Related Content Social Bookmarking                   What's this?

Pyrolysis Gas Chromatography of Wool

Part II: Detection and Quantitation of Tryptophan in Wool and Simple Proteins

USDA, ARS, Eastern Regional Research Center, Philadelphia, Pennsylvania 19118, U.S.A.

Paul Magidman

USDA, ARS, Eastern Regional Research Center, Philadelphia, Pennsylvania 19118, U.S.A.

Harold M. Farrell, JR

USDA, ARS, Eastern Regional Research Center, Philadelphia, Pennsylvania 19118, U.S.A.

Although determination of tyrosine and most other amino acids is straightforward by conventional methods of amino acid analysis, determination of tryptophan is dif ficult and time-consuming due to its sensitivity to acid-catalyzed protein hydrolysis. Pyrolysis gas chromatography (Py-GC) therefore was investigated as an alternative method for tryptophan analysis. Py-GC revealed that wool gives rise to indole and skatole from degradation of its tryptophanyl residues, along with phenol' and para- cresol from its tyrosyl residues. To test Py-GC for determining tryptophan content relative to tyrosine content, mixtures of poly-tryptophan and poly-tyrosine were used to establish a linear relationship between the peak area ratio indole/(phenol + para- cresol) and the tryptophan / tyrosine molar ratio (Trp/Tyr). The polypeptide data were supplemented with data from pyrolysis of several proteins of known Trp/Tyr ratio. The supplemental data also were used to confirm the utility of the linear rela tionship in deriving a Trp/Tyr ratio for an unknown protein. The accuracy of the derived Trp/Tyr ratio diminished somewhat when the tryptophan content was low; using Py-GC, wool was predicted to have one tryptophan for every eight to nine tyrosines, as opposed to one for every seven tyrosines using conventional amino acid analysis. The method permitted facile monitoring of tryptophan degradation in wool during treatment with dimethyl sulfoxide in hydrochloric and acetic acid. There also was a strong indication of tryptophan degradation during wool carbonizing.

CiteULike    Connotea    Del.icio.us    Digg    Reddit    Technorati    What's this?