What are Anemias caused by a violation of the structure of globin chains?
Anemias, characterized by a violation of the structure of globin chains (the so-called hemoglobinopathies), represent a group of diseases caused by the disruption of the normal structure (amino acid) of the hemoglobin chain. Such defects as the absence of the whole chain segment, its elongation, and also the replacement of one or several amino acids in the globin chain are quite common.
For the first time, hemoglobin with a modified structure was described in 1949, when the scientist Pauling detected hemoglobin in children, which is moving more slowly during alkaline electrophoresis than hemoglobin of an adult.
In 1956, another Ingram scientist, using the method of peptide maps, proved that the hemoglobin detected in sickle cell anemia and called hemoglobin S differs from hemoglobin A in a healthy adult only in the replacement of one amino acid in the beta chain.
Symptoms of Anemias caused by the violation of the structure of globin chains
The clinical picture of the disease is directly dependent on the location of the defect in the hemoglobin chain.
So, hemoglobinopathies can be characterized by anemia, or, on the contrary, there is an increase in the content of both hemoglobin and red blood cells in the blood. Quite often, the disease is absolutely asymptomatic.
Diagnosis of Anemias caused by the violation of the structure of globin chains
To identify abnormal hemoglobin, it is necessary to isolate a fraction of pathological hemoglobin and determine the sequence of amino acids in it. Most hemoglobinopathies do not produce clinical manifestations in either heterozygous or homozygous carriage. This happens when amino acid substitutions do not upset the tertiary or quaternary structure of hemoglobin and the basic functions of hemoglobin are not disturbed. Conversely, some hemoglobinopathies have vivid clinical manifestations in homozygous carriage, as well as in combination with thalassemia. There is a group of pathological hemoglobins in which the clinical picture of the disease appears in heterozygous carriers of the pathological gene.
With these hemoglobinopathies, the most important functional amino acids are replaced. They are involved in fixing the heme to the globin and the globin chains between themselves.
To identify abnormal hemoglobin, it is necessary to establish the presence of abnormal hemoglobin in a patient.
After the detection of hemoglobin abnormalities, it is necessary to separate it from normal hemoglobin A, clarify the chain in which there is a substitution.
The next step is the study of the amino acid composition of abnormal chains and, if necessary, the determination of the sequence of amino acids.
When referring to hemoglobin, in addition to its name, the chain in which there is a substitution is indicated, the number of the amino acid in the chain (starting from the nitrogen end), the name of the amino acid that is in this place, and what it should be.