| muscle haemoglobin | <physiology> Protein (17.5 kD) found in red skeletal muscle. It was the first protein for which the tertiary structure was determined by X-ray diffraction, by J.C.Kendrew's group working on sperm whale myoglobin. It is a single polypeptide chain of 153 amino acids, containing a haem group bonded via its ferric iron to two histidine residues. It binds oxygen noncooperatively and has a higher affinity for oxygen than haemoglobin at all partial pressures. In capillaries oxygen is effectively removed from haemoglobin and diffuses into muscle fibres where it binds to myoglobin which acts as an oxygen store. (18 Nov 1997) |
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| haemoglobin | <cell biology, haematology> Four subunit globular oxygen carrying protein of the erythrocytes of vertebrates and some invertebrates. It is a conjugated protein containing four haem groups and globin. There are two alpha and two beta chains (very similar to myoglobin) in adult humans, the haem moiety (an iron containing substituted porphyrin) is firmly held in a nonpolar crevice in each peptide chain. There are four globin polypeptide chains, designated alpha, beta, gamma, delta in the adult. Each is composed of several hundred amino acids. (08 Mar 2000) |
| haemoglobin A | <haematology> Haemoglobin A is the normal form of the protein haemoglobin which is found in adults. It is composed of two alpha chains and two beta chains. (09 Oct 1997) |
| haemoglobin A1C | <haematology> The substance of red blood cells that carries oxygen to the cells and sometimes joins with glucose. Because the glucose stays attached for the life of the cell (about 4 months), a test to measure haemoglobin A1C shows what the person's average blood glucose level was for that period of time. (09 Oct 1997) |
| haemoglobin A2 | <chemical> An adult haemoglobin component normally present in haemolysates from human erythrocytes in concentrations of about 3%. The haemoglobin is composed of two alpha chains and two delta chains. The percentage of hba2 varies in some haematologic disorders, but is about double in beta-thalassaemia. Chemical name: Haemoglobin A2 (12 Dec 1998) |
| 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) |
| 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 C | <haematology> Haemoglobin C is an abnormal version of the protein haemoglobin. The sixth amino acid of the normal beta chain, glutamic acid, is replaced by lysine in haemoglobin C. This mutation causes the red blood cell to be less flexible. (09 Oct 1997) |
| haemoglobin C disease | <haematology> A rare genetic disease of the haemoglobin. Patients are anemic due to the premature breakdown of the blood cells in the spleen. Jaundice may be seen in some patients. There is no specific treatment other than supportive care. (27 Sep 1997) |
| haemoglobin Chesapeake | An abnormal Hb with a single a chain substitution, molecular formula a292Arg→Leub2A; heterozygotes have polycythemia, apparently to compensate for the increased oxygen affinity of this Hb, resulting in decreased liberation of oxygen in the tissues. (05 Mar 2000) |
| haemoglobin Constant Spring | An abnormal haemoglobin having an extended polypeptide chain (31 additional amino acid residues) on the a chain (thus, the a chain is 172 amino acids long); approximately 20% of the individuals with Hb H disease also have this defect. (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) |