| haemoglobin a, glycosylated | Minor haemoglobin components of human erythrocytes designated a1a, a1b, and a1c. Haemoglobin a1c is most important since its sugar moiety is glucose covalently bound to the terminal amino acid of the beta chain. Since normal glycohemoglobin concentrations exclude marked blood glucose fluctuations over the preceding three to four weeks, the concentration of glycosylated haemoglobin a is a more reliable index of the blood sugar average over a long period of time. (12 Dec 1998) |
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| haemoglobin AIc | The major fraction of glycosylated haemoglobin. (05 Mar 2000) |
| haemoglobin Anti-Lepore | A group of abnormal haemoglobins similar to haemoglobin Lepore. These haemoglobins have normal a chains, but the non-a chain consists of the N-terminal portion of the b chain joined to the C-terminal portion of the d chain. This is the opposite crossing over pattern observed in haemoglobin Lepore. Examples of haemoglobin Anti-Lepore include HbMiyada, Hb PCongo, Hb PNilotic, and HbLincoln Park. There is also one variant that is both haemoglobin Lepore and haemoglobin Anti-Lepore (HbParchman). Compare: haemoglobin Lepore. (05 Mar 2000) |
| haemoglobin Bart's | A Hb homotetramer (all four polypeptides identical) of formula g4, found in the early embryo and in alpha-thalassaemia 2; not effective in oxygen transport; does not display a Bohr effect. (05 Mar 2000) |
| haemoglobin DPunjab | An abnormal Hb with a single b chain substitution, molecular formula a2Ab2121Glu→ Gln; heterozygotes are asymptomatic, homozygotes have mild haemolytic anaemia; there is an increase in O2 affinity; identical to haemoglobin DLos Angeles, haemoglobin DNorth Carolina, haemoglobin DPortugal, haemoglobin DChicago, and haemoblogin Oak Ridge. (05 Mar 2000) |
| haemoglobin E | <haematology> Haemoglobin E is an abnormal version of the protein haemoglobin, found in Southeast Asia, which plays a role in such medical conditions as microcythaemia, target cell formation, and mild haemolytic anaemia. The beta chain of the haemoglobin is altered because of a mutation. (09 Oct 1997) |
| haemoglobin electrophoresis | <investigation> A special diagnostic procedure which identifies abnormal haemoglobin proteins by the way they migrate in an electric field (electrophoresis). The electric field is used to separate haemoglobin proteins from each other and allow the identification of different components. This can be used to diagnose thalassaemia, sickle cell disease and haemoglobin C disease. (18 Nov 1997) |
| haemoglobin F | <haematology> Haemoglobin f is the normal form of the protein haemoglobin which is found in the foetus. (09 Oct 1997) |
| haemoglobin Gower-1 | A Hb of molecular formula ζ2&vepsilon;2, found as a minor Hb in the early embryo; disappears by the third month of pregnancy in favour of haemoglobin Gower-2 and haemaglobin Portland and then by Hb F; the ζ chain has 141 amino acid residues. Synthesis of the ζ chain is deficient in cases of hydrops foetalis. Compare: haemoglobin Gower-2, haemoglobin Portland. (05 Mar 2000) |
| haemoglobin Gower-2 | A normal Hb of molecular formula a2A&vepsilon;2, which is a major Hb component of the early embryo; production of &vepsilon; chains normally ceases at about the third month of foetal development and is replaced by Hb F. Compare: haemoglobin Gower-1, haemoglobin Portland. (05 Mar 2000) |
| haemoglobin H | <haematology> Haemoglobin H is an abnormal version of the protein haemoglobin. The normal haemoglobin is composed of two alpha and two beta polypeptide chains, haemoglobin H is composed of four beta chains. The molecule has a very high affinity to oxygen, but is very inefficient at transporting it. (09 Oct 1997) |
| haemoglobin I | An abnormal Hb with a single a chain substitution, molecular formula a216Lys→Glub2A; a thalassaemia-like syndrome has been found in individuals heterozygous for both Hb I and alpha-thalassaemia genes, with formation of about 70% Hb I. (05 Mar 2000) |
| haemoglobin J | <chemical> A group of abnormal haemoglobins with similar electrophoretic characteristics. They have faster electrophoretic mobility and different amino acid substitutions in either the alpha or beta chains than normal adult haemoglobin. Some of the variants produce haematologic abnormalities, others result in no clinical disorders. Chemical name: Haemoglobin J (12 Dec 1998) |
| haemoglobin JCapetown | An abnormal Hb with a single a chain substitution, molecular formula a292Arg→Glnb2A; heterozygotes have polycythemia because of increased oxygen affinity of this Hb. (05 Mar 2000) |
| haemoglobin Kansas | An abnormal Hb of molecular formula a2Ab2102Asn→Thr; found in association with familial cyanosis due to decreased oxygen affinity of this Hb. (05 Mar 2000) |