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Biomedical subjects

L Tentori

Publications and source records attributed to L Tentori.

At least 91 records · Page 5Linked to original sources
PubMed1978

Thin-layer isoelectric focusing of hemoglobin variants: screening and determination of isoelectric points.

The high resolving power of thin-layer isoelectric focusing was applied for screening some hemoglobin variants classified on the basis of their electrophoretic mobility in: electrophoretically slow variants (as Hb A2), electrophoretically slow variants (as Hb S), electrophorectically fast variants (Hbs type J). An analysis of the variant compounds has been performed, and the corresponding pI values were determined in whole hemolysate.

Genetic Variation↗
PubMed1978

Properties of hemoglobin G. Ferrara (beta57(E1) Asn replaced by Lys).

Hemoglobin G. Ferrara is an abnormal human hemoglobin in which an asparagine residue is replaced by a lysyl residue at position beta57 (beta57 Asn replaced by Lys). Oxygen equilibria show that cooperativity and alkaline Bohr effect are maintained to normal levels while the acid Bohr effect appears increased; in addition, a smaller effect of diphosphoglycerate is also observed. Flash photolysis experiments performed as a function of protein concentration show that the fraction of quickly reacting form is always higher than that of human hemoglobin A. This fact, together with the increase of the oxygen affinity observed at acid pH values, may be related to an enhanced dissociation of the molecule into dimers. Several attempts to isolate the native chains by treatment of the protein with p-chloromercuribenzoate were unsuccessful due to the great instability of the isolated variant beta-chains, which precipitated completely during incubation with p-chloromercuribenzoate. Therefore, although the substitution is on the surface of the molecule, there are several properties of hemoglobin G. beta Ferrara which are clearly different from hemoglobin A.

Diphosphoglyceric Acids↗
PubMed1978

Fetal haemoglobin in early malignant osteopetrosis.

The characteristics of the fetal haemoglobin (HbF) in two children with osteopetrosis and high levels of HbF have been studied. The structural analysis of the gamma chains demonstrated a fetal Ggamma/Agamma ratio. HbF was distributed inside only 30% of the peripheral red blood cells. In vitro globin chain synthesis studies showed that there was balanced globin chain production, despite the increased level of HbF.

Alanine↗
PubMed1978

Hemoglobin Legnano (alpha2 141 (HC3) Arg replaced by Leu beta2): a new abnormal human hemoglobin with high oxygen affinity.

An abnormal, fast moving hemoglobin was noted in a 34-yr-old male patient living in Legnano (northern Italy) affected with renal failure and iron deficiency anemia, not related to the presence of the Hb variant. Structural studies have demonstrated a previously undescribed amino acid substitution, alpha 141 Arg replaced by Leu. This new variant has been named Hb Legnano, and is characterized by an increased oxygen affinity and a low cooperativity, at least as far as preliminary functional studies carried out on whole blood have indicated. Family studies are reported: three other heterozygous carriers were observed among the relatives of the propositus, all showing a mild polycythemia which, however, does not seem to produce appreciable clinical consequences.

Adult↗
PubMed1977

Hemoglobinometry: A comparison between the hemiglobincyanide method and the Coulter S counter.

The relative accuracy and precision of the Coulter S Counter have been evaluated in comparison with manual hemiglobincyanide determination according to the recommendations of the International Committee for Standardization in Hematology. Some improvements in the manual procedure, such as centrifugation of hemiglobincyanide solutions and the use of the detergent Triton X-100, were also tested. The Coulter S Counter generally gives higher precision in comparison with the manual method. Nevertheles, Coulter S determinations are systematically lower due to both constant and proportional errors. The available data ranged between hemoglobin values of 11.5 and 18.5%, giving differences of 0-8% between hemoglobin values determined by the Coulter S Counter and the hemiglobincyanide method.

Detergents↗
PubMed1977

Hemoglobin Gavello - alpha 2 beta 2 47 (CD6) Asp replaced by Gly. A new hemoglobin variant from Polesine (Italy).

During a survey for abnormal hemoglobins in Polesine (a region north of the Po river, where beta-thalassemia is very frequent) a slow moving variant was noted in a 79-yr-old woman living in Gavello, a small town in the province of Rovigo. Structural studies demonstrated a previously undescribed amino acid substitution, beta47 Asp replaced by Gly. This new variant has been named Hb Gavello.

Aged↗
PubMed1975

Allosteric interactions in non-alpha chains isolated from normal human hemoglobin, fetal hemoglobin, and hemoglobin Abruzzo (beta143 (H21) His replaced by Arg).

Oxygen-linked effects of inositol hexaphosphate occur in heme-containing non-alpha chains isolated from normal human hemoglobin, fetal hemoglobin, and the abnormal human hemoglobin Abruzzo, beta143(H21) His leads to Arg. The occurrence of these effects implies that the chains undergo ligand-linked conformational changes. Inositol hexaphosphate lowers the oxygen affinity of isolated beta and gamma chains by differential binding to their deoxy conformations. Neither 2,3-diphosphoglycerate nor inorganic phosphate produces such an effect. In the case of Abruzzo beta chains, the binding of inorganic phosphate and 2,3-diphosphoglycerate is also oxygen-linked. Stripped beta chains isolated from hemoglobin Abruzzo have much higher oxygen affinity than beta chains isolated from HbA. Their higher oxygen affinity and enhanced allosteric interactions with phosphates account, in large part, for the abnormal functional behavior of the hemoglobin Abruzzo tetramer. In this hemoglobin variant the substitution of arginine for histidine at beta143 involves a residue known to interact with anionic allosteric effectors of hemoglobin. It is of interest that the effect of inositol hexaphosphate observed with isolated gamma chains is comparable to the effect observed with isolated beta chains, even though the gamma143 position is occupied by an uncharged serine residue.

Allosteric Regulation↗
PubMed1975

Hemoglobin Abruzzo (beta143 (H21) His replaced by Arg). Consequences of altering the 2,3-diphosphoglycerate binding site.

Hemoglobin Abruzzo is an abnormal human hemoglobin with a substitution at a residue known to be involved in the binding of 2,3-diphosphoglyceric acid. It has increased oxygen affinity and reduced heme-heme interaction in the absence of organic or inorganic phosphate cofactors. In inorganic phosphate buffers the Bohr effect and heme-heme interaction are normal, but the oxygen affinity remains higher than that of hemoglobin A. CO combination in inorganic phosphate is more strongly autocatalytic than in normal hemoglobin and a slower rate of oxygen dissociation is observed. Although many of the functional differences of this variant may be attributed to the high oxygen affinity of the mutant beta chains, the interactions between subunits are also affected by the histidine to arginine substitution at beta143. Stripped hemoglobin Abruzzo appears to be significantly more dissociated than hemoglobin A. Kinetic studies indicate that interaction with organic or inorganic phosphates decreases its subunit dissociation. In all of the functional properties examined, hemoglobin Abruzzo is more sensitive to the allosteric influence of organic and inorganic anions than is hemoglobin A.

Amino Acid Sequence↗