Iodoacetic add

Poly-L-cysteine (XXXIV) was prepared by polymerization of S-carbobenzoxy-N-carboxy-L-cysteine anhydride (XXXIII), followed by reduction with sodium in liquid ammonia 47). The reactivity of the thiol groups in this polymer toward iodoacetic add indicated that quantitative liberation of mercapto groups had beat effected but selective reactivity was observed with methyl mercuric nitrate in the presence of sodium nitroprusside, an internal indicator. These reactivity differences result from sterk exclusion of the nitroprusside dye from about one third of the available mercaptan moities. Thus the concept of sluggish-SH groups in a protein has been demonstrated with a synthetic homopolymer. 

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