RESUMO
Human haemoglobin or globin in its native form reacts with 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) with uptake of two 3-carboxylato-4-nitrothiophenol groups, one for each of the reactive thiols at the beta93 positions. Attempts to isolate the DTNB-treated globin by the acetone-HC1 method, which unfolds the protein chains, result in disulphide interchange and oxidation of almost all the uncoupled "masked" thiol groups. This modification is in marked contrast to the stability of haemoglobin or globin treated with reagents such as iodoacetic acid or N-ethylmaleimide that do not form disulphide bonds in blocking the thiol groups. The derivatized globin chains have been separated by urea-thiol buffer chromatography on carboxymethycellulose columns. Amino acid analysis and peptide mapping established the presence and location of disulphide bonds, whilst gel filtration in urea buffers and sodium dodecyl sulphate acrylamide gel electrophoresis defined the size of the products.
Assuntos
Ácido Ditionitrobenzoico , Globinas , Hemoglobinas , Nitrobenzoatos , Carbocisteína/análise , Fenômenos Químicos , Química , Cromatografia por Troca Iônica , Cistina/análise , Dissulfetos , Eletroforese em Acetato de Celulose , Etilmaleimida , Globinas/isolamento & purificação , Humanos , Peso Molecular , Fragmentos de Peptídeos/análise , TripsinaRESUMO
A case of Haemoglobin C trait and a family with Haemoglobin O Arab thalassaemia from Greece are described. Both Haemoglobin C and Haemoglobin O Arab were identified by peptide analysis.
