Glycated haemoglobin analysis.

Abstract

Haemoglobin (Hb) in the adult human consists of predominantly HbA, with a small amount of HbA2, and a trace of HbF. HbA contains a number of minor haemoglobins identified as HbAla, HbA1b, and HbA!c, collectively referred to as HbA l, 'fast haemoglobins', glycosylated or glycated haemoglobins or simply glycohaemoglobins. The first description of fast haemoglobin was made by Kunkel and Wallenuis' in 1955. These workers were using starch gel electrophoresis to separate haemoglobin in the blood of diabetics, and identified the fast fraction as 'new' haemoglobins. For more than a decade methods used to isolate HbA I were based on ion exchange chromatography; Allen and co-workers? in 1958, described a cation exchange column that was capable of separating the fast fraction. Under modified conditions this method could further separate this fraction into HbA1a, HbA1b, and HbA le. It was confirmed in 1961 that these fractions were all contained in the fast electrophoretic fraction.! In 1957, Rhinesmith and co-workers'> suggested that there was some abnormality present in the N-terminus of the fJ chain of HbA\. Most of the attention to the structural characterization was given to HbA le, which constitutes the major portion of the fast haemoglobins. Holmquist and Schroeder in 1966, concluded that HbAle is a condensation product (Schiff base) of HbA and a ketone or an aldehyde (R = 0). The point of linkage of R = 0 to the haemoglobin was the N terminus of the fJ chain. The investigations of Bookchin and Gallop? strongly indicated that a hexose was linked to the Nterminal valine of the f1 (Ale) chain. The exact nature of the hexose molecules was elucidated by Bunn and co-workers who were able to isolate the reducing sugars by mild acid hydrolysis and showed them to be glucose and mannose in a