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At least 487 records · Page 27Linked to original sources
PubMed1993

Use of protein database for the computation of the dipole moments of normal and abnormal hemoglobins.

Previously, we discussed the calculation of the dipole moments of small proteins using the three-dimensional protein data-base. Our results demonstrate that the calculated dipole moments are in acceptable agreement with measured values. We, however, noted the difficulty of the calculation with larger proteins, in particular those consisting of several subunits. Hemoglobin (Hb) is a protein having a molecular weight of 64,000 that consists of four subunits, a typical case where the computation was found to be difficult. To circumvent the difficulties, we calculated the dipole moment of each subunit separately. The dipole moment of the whole protein was calculated by the vectorial summation of subunit moments. With this method, the calculated net dipole moment is in good agreement with the experimental value. Our calculation shows that the dipole moment vectors of subunits are, by and large, antiparallel in tetramers causing partial cancellation of the net dipole moment. In addition to normal HbA, the dipole moment of abnormal HbS was calculated using an approximate computational technique. Because of the loss of two negative changes as a result of the replacement of glutamic acid with valine in beta-chains, the dipole moment of HbS was found, experimentally and theoretically, to be significantly smaller than that of HbA.

Biophysical Phenomena↗
PubMed2005

Oxidative reactions of normal and abnormal hemoglobins in the presence of phosphatidylserine vesicles.

We have monitored a sequence of reactions involving hemoglobin (Hb) oxidation in the presence of phospholipid bilayers in carefully characterized buffer systems in order to delineate molecular events that may have cytotoxic effects, some of which may even lead to cellular death of erythrocytes. We followed reactions of subunit cross-linking, heme iron oxidation, heme destruction and iron release in normal (Hb A) and sickle [Hb S or beta6(A3)Glu-->Val] Hbs under different experimental conditions. Our results show that, in the presence of lipid surfaces, the reaction rates for heme Fe+2 to Fe+3 oxidation in Hb A and Hb S molecules were both enhanced by lipid surfaces. However, the extent of the enhancement in Hb A and Hb S was quite different in T5K6.5, a Tris buffer with low ionic strength and low pH. In T5K6.5, the rate constants were 0.8 h(-1) for Hb A and 4.3 h(-1) for Hb S, a 5-fold difference. This finding supports a published suggestion that sickle Hb exhibits abnormal heme oxidation in erythrocytes of sickle cell disease patients. We found that the rates were quite similar in P110N7.4, a phosphate buffer near physiological conditions. Even in T5K6.5, the lipid surface did not enhance Hb S reactions involving subunit cross-linking, heme destruction, or iron release. These findings suggest that heme oxidation and related reactions may not be responsible for detrimental cellular events in sickle erythrocytes under physiological conditions, as suggested in the literature.

Heme↗
PubMed1988

[Evaluation of the cost-effectiveness of school screening for hereditary hemoglobin abnormalities: prospective study in Bouches-du-Rhône. School screening for hemoglobinopathies].

Screening in schools for heterozygote carriers of haemoglobinopathies traits has been carried out experimentally in southeast France ("Bouches du Rhône", the Marseille region) since 1977. The study compares, in cost-effectiveness terms, the screening strategy now followed with 27 alternative strategies in all the pupils (14-16 years). Although the frequency of heterozygote carriers in this school population as a whole is only 7.9% carriers for beta-thalassaemia gene and 2.5% carriers for HbS, prospective costs per diagnosis still seem reasonable: from 1544 to 4997 French francs (1987) depending on the strategy, and 2099 to 7380 francs if beta-thalassaemia alone is screened. In comparison with the current screening strategy, cost-effectiveness ratios could be improved by using haemoglobin electrophoresis as a preselection test, or a blood count if beta-thalassaemia alone is screened. Further improvement of cost-effectiveness ratios could be obtained by limiting screening to ethnic groups most "at risk"; but such strategies raise ethical and acceptability issues.

Adolescent↗
PubMed1984

Hemoglobin abnormalities in a black family with HB S, hereditary persistence of HB F, and a gamma chain variant; a reevaluation through gene mapping.

Members of a Black family from Georgia who were investigated for the first time in 1960 and several times thereafter were reinvestigated through DNA restriction endonuclease analyses and haplotyping, while the gamma chain heterogeneity of the Hb F was reevaluated using a newly developed HPLC procedure. Four different abnormalities were present. (a) Heterozygosity for G gamma A gamma-HPFH type II characterized by a large deletion involving the delta and beta globin genes with a 5' end within the psi beta gene. (b) Heterozygosity for an -epsilon-G gamma-G gamma-psi beta-delta-beta S-chromosome, thus carrying a beta S globin gene and two G gamma genes instead of one G gamma and one A gamma gene. (c) Heterozygosity for an -epsilon-G gamma-A gamma T-psi beta-delta-beta S-chromosome, carrying the beta S globin gene and an allele of the A gamma (or A gamma I) gene. These three chromosomes occurred in combination with each other, resulting in SS and S-HPFH conditions, and with a normal -epsilon-G gamma-A gamma-psi beta-delta-beta A-chromosome resulting in the HPFH and Hb S heterozygosities. The presence of the -G gamma-G gamma- and -G gamma-A gamma T-chromosomes in the one SS patient was responsible for the high G gamma value (average 75%), 25% A gamma T chain, and for the absence of the A gamma I chain. (d) An alpha-thalassemia-2 heterozygosity in one member.

Black People↗
PubMed1998

The molecular spectrum of beta-thalassemia and abnormal hemoglobins in the allochthonous and autochthonous dutch population.

The prevalence at birth of hemoglobin defects in the autochthonous North-European population is low. However, the long immigration and colonial history of the Netherlands has resulted in a group of about 1-2 million 'autochthonous' inhabitants, with Asian, South-European or African ancestors, in whom a moderate birth prevalence of globin gene mutations can be expected. Furthermore, at least 10% of the Dutch population consists of recent immigrants from different countries with high birth prevalence of hemoglobinopathies. Because of the endogamous partner choice, which is prevalent in this population, the risk for homozygous progeny remains elevated. At least 100,000 carriers of hemoglobinopathies of recent allochthonous origin are present in the Netherlands, and the number of homozygous children is rising. Prevention by prenatal diagnosis requires a suitable protocol and knowledge about the molecular defects present in the country. Therefore we have analyzed a large number of patients and carriers, both at the hematological and at the DNA level. Our survey revealed 47 different beta-thalassemia determinants, characterized on 223 independent chromosomes from individuals of different ethnic origins. As expected, the most prevalent mutations were largely represented. The cd39 (C-->T) mutation was found in 70% of the immigrants from Morocco, Sardinia and other Central-West-Mediterranean regions while the IVS-I-110 (G-->A) was prevalent in the East-Mediterranean populations. The IVS-I-5 (G-->C) mutation was found in 45% of the patients of Indonesian origin. We also registered 308 independent chromosomes with common structural defects (HbS, HbC, HbE, Hb Lepore, Hb Constant Spring and HbD Punjab) and 33 chromosomes with 19 different, less frequent, rare or very rare mutants. Seven structural mutants were described for the first time and published separately. Furthermore, 139 independent chromosomes with deletional and nondeletional alpha-thalassemia defects were characterized.

Journal Article↗
PubMed1978

Effects of abnormal hemoglobin concentration in human blood on membrane diffusing capacity of the lung and on pulmonary capillary blood volume.

In 13 patients with chronic anemia or polycythemia but normal lung function, and in 7 healthy students a statistically significant correlation between hemoglobin concentration and membrane diffusing capacity of the lung for CO was found. A membrane diffusing constant resulting from extrapolation for hemoglobin concentration 0 g/ was 13.4% of the predicted value (100% for Hb = 14.5 g%). A change of 1 g hemoglobin/100 ml changes membrane diffusing capacity for 6.3% of the predicted value. This result confirms the theory of Koyama and Mochizuki that the diffusing capacity of the pulmonary membrane is a function of the hemoglobin concentration of pulmonary capillary blood. In 3 healthy subjects with normal hemoglobin concentration the effect of DL/VA inhomogenities in the lung on single-breath diffusing capacity and its subdivisions was examined. An increase of DLCO for 20% of predicted normal at decreasing apnea time (tA = 5 sec) resulted from an increased pulmonary capillary blood volume for 50--90% of the predicted value (at tA = 10 sec), whereas membrane diffusing capacity remained unchanged over the range of apnea times. The reasons for this finding are still unknown; alteration of pulmonary perfusion at changing apnea time is taken into account.

Anemia↗