| Popis: |
The interaction of nucleophilic, electron-donating, compounds with complement components has a long history. The inhibitory effect of ammonia on the fourth component of complement was reported in 1926 [1]. These early experiments showed that ammonia was an effective inhibitor only at pH values greater than 8, at which the NH3, nucleophilic, form will be present. Inhibition of C4 by ammonia contributed to the development of ideas on the complement system because it demonstrated that the opsonic activity of complement could be separated from the fourth component. Treatment of serum with ammonia or hydrazine was routinely used in the past as a means of generating serum lacking C4 activity which is required for quantification of C4 activity in other samples [2]. Nucleophile-treated serum has now been replaced mainly by guinea pig serum genetically deficient in C4 [3]. Within the past ten years the molecular basis of the effect of fluid phase nucleophiles on C3 and C4 has been established: these compounds react with an unusual structure, a thiolester, within the proteins. The root of the differences in the reactivities of the homologous complement components C3 and C4 has also been identified. |
