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Biomedical subjects

R W Noble

Publications and source records attributed to R W Noble.

At least 55 records · Page 3Linked to original sources
PubMed1980

Variability of the magnetic moment of carbon monoxide hemoglobin from carp.

Deionized carp carbon monoxide hemoglobin in distilled water or in bis(2-hydroxyethyl)imino-tris(hydroxymethyl)methane or Tris buffer exhibits a slight but significant paramagnetism. This is most clearly demonstrated by the decrease in this paramagnetism that is caused by the addition of inositol hexaphosphate to this protein in the former buffer at pH 6.3-6.4. No such effect is seen when inositol hexaphosphate is added to carp cyanomethemoglobin, demonstrating that the change observed with carbon monoxide derivative is not due to a modification in the diamagnetic properties of the protein.

Animals↗
PubMed1978

Idiotypic cross-reactivity between antibodies of different specificities.

Cross-idiotypic specificity has been demonstrated between antibody populations of different specificities using antibodies directed toward human sickle cell hemoglobin (HbS). A site-specific antibody directed toward the beta6-position of HbS, anti-Val, was used to elicit an anti-idiotypic response in rabbits. Using this anti-idiotypic serum, idiotypic cross-reactivity was demonstrated between antibody populations that bind to human adult hemoglobin (HbA). It was demonstrated that in the case of the goat antibodies, these idiotypically cross-reacting antibodies are directed towards the beta6-position of the hemoglobin molecule. However, they differ in their specificity, binding to this site on HbA, whereas anti-Val binds only to HbS. The sheep antibody populations directed toward HbS differ qualitatively from those of the goat. Using rabbit anti-idiotypic serum specific for sheep anti-Val, cross-reactivity could be demonstrated with antibodies directed toward the alpha-chain of the hemoglobin molecule, as well as the beta-chain. There was also a low level of cross-reactivity with antibodies from a goat immunized with HbA.

Animals↗
PubMed1978

Influence of quaternary structure of the globin on thermal spin equilibria in different methemoglobin derivatives.

We have measured the paramagnetic susceptibilities of sperm whale azide metmyoglobin and of carp azide, thiocyanate, and nitrite methemoglobin in the quaternary oxy (R) and deoxy (T) structures between about 300 and 90 K, using a new sensitive superconducting magnetometer. We have also measured the pressure dependence of the high- and low-spin optical absorption bands of azide metmyoglobin and of carp azide methemoglobin in the R and T structures between 1 and 2000-4000 atmospheres. At low temperatures all the derivatives show normal Curie behavior, but above 200-250 K this is reversed, so that a thermal spin equilibrium is set up and the paramagnetic susceptibilities rise steeply with rising temperature. At all temperatures the effective magnetic moments in the T structure are higher than in the R structure. The magnetic data for azide methemoglobin have been subjected to detailed analysis. Below 250 K the magnetic moment in the R structure is 1.98 microB, characteristic of pure low spin, but that in the T structure is 2.80 microB, suggestive of a random mixture of high- and low-spin centers which have become frozen in by the immobility of the surrounding protein. Comparison of the thermal spin equilibria above 250 K shows that in the T structure the equilibrium is biased toward higher spin by the equivalent of about 1 kcal/mol relative to the R structure. Hydrostatic pressure reduces the optical density of the high-spin band at 630 nm and increases that of the low-spin bands at 541 and 573 nm. We have calibrated the optical density of the band at 630 nm against the measured paramagnetic susceptibilities of sperm whale azide metmyoglobin and carp azide methemoglobin in the R and T structures and have used this calibration to determine the dependence of the spin equilibria on hydrostatic pressure; this has allowed us to calculate the volume contraction associated with the transition from the fully high to the fully low-spin state. This amounts to -6.7 and -13.3 mL/mol heme for carp azide methemoglobins in the R and T structures, respectively, and to -12.5 mL/mol heme for azide metmyoglobin. These volume contractions are larger than those of about -4 mL/mol Fe found in synthetic iron chelates. Apparently stereochemical changes of the globin surrounding the heme also contribute to the volume changes; these must be larger in the T than in the R structure. The significance of these observations for the mechanism of heme-heme interaction is discussed.

Animals↗
PubMed1978

The kinetics and equilibria of squirrel-fish hemoglobin. A Root effect hemoglobin complicated by large subunit heterogeneity.

The functional properties of squirrel-fish hemoglobin have been measured by studying ligand binding equilibria and kinetics. The results show that squirrel-fish hemoglobin has a Root effect with a corresponding stabilization of the low affinity state. The properties of this state are pH dependent even in the absence of cooperativity. The effect of ATP shifts the overall ligant affinity towards the low affinity state and is characteristic of the allosteric effect caused by organic phosphates. Under pH and ATP conditions favoring the low affinity conformational state, a 10-fold difference in the binding kinetics of carbon monoxide to the alpha and beta subunits is observed.

Adenosine Triphosphate↗
PubMed1978

Specific antibodies to hemoglobin A1 (anti-Glu) and hemoglobin S (anti-Val) in the guinea pig: immunologic and structural correlations.

Like goats and sheep, guinea pigs can produce, in response to human sickle cell hemoglobin (beta6 Glu leads to Val), an antibody population (anti-Val) that will bind sickle cell hemoglobin but not normal hemoglobin HbA. Unlike goats and sheep, guinea pigs can produce in response to human hemoglobin A1 an antibody fraction, anti-Glu, that will not react with human sickle cell hemoglobin. These anti-Glu antibodies have been isolated by affinity chromatography and their specificity confirmed by fluorescence-quenching titrations. The sequence of the first 10 amino acids of the beta-chain of guinea pig hemoglobin has been determined. This sequence differs from those of both hemoglobin HbA and sickle cell hemoglobin by two residues, those at positions 5 and 6. This explains the similarity of the immunogenicity of this site on the two human hemoglobins when administered to guinea pigs. Both goats and sheep are identical to hemoglobin A1 at the beta-6 position.

Amino Acids↗
PubMed1977

Evolution of an idiotypic determinant: anti-Val.

An antibody population which reacts only with human sickle cell hemoglobin (HbS) and not with normal human hemoglobin, has been isolated from goat, sheep, and guinea pig antisera. These antibody populations termed anti-Val (Val), isolated from an individual goat (no. 6) and sheep (no. 26) have been used to elicit anti-idiotypic responses in rabbits. These anti-idiotypic sera were used to study the idiotypic cross-reactions between the goat and sheep anti-Val. Strong cross-reactions were present using either Ra anti-goat anti-Val or Ra anti-sheep anti-Val. Guinea pig anti-Val did not cross-react with these anti-idiotypic sera. Binding of HbS to the anti-Val of the goat and sheep could be blocked by the anti-idiotypic sera, but the binding of HbS to the guinea pig anti-Val could not. These data demonstrate idiotypic cross-reactivity between two closely related species.

Animals↗
PubMed1977

Ligand-induced conformational changes in spin label-modified human hemoglobins and chains and their carboxypeptidase A-digested derivatives.

The reactive sulfhydryls of human adult and fetal hemoglobin and the single sulfhydryl of isolated gamma chains have been spin labeled with N-(1-oxyl-2,2,5,5-tetramethyl-3-pyrrolidinyl) iodoacetamide. Similar electron paramagnetic spectral differences between oxy- and deoxy-modified hemoglobins were observed for both these hemoglobins and for the isolated chains, indicating that ligand-induced conformational changes occur in isolated hemoglobin subunits as well as intact hemoglobin tetramers. Ligand induced changes in the reactivity of p-hydroxymercuribenzoate with the sulfhydryl groups of both intact hemoglobins and isolated subunits, observed by McDonald and Noble (1974) J. Biol. Chem. 249, 3161-3165), led them to draw a similar conclusion. Following carboxypeptidase A digestion of these modified hemoglobins and gamma chains, a procedure which specifically removes the two C-terminal residues of the beta or gamma chains, spectral differences between the liganded and unliganded spin-labeled derivatives still persisted. However, the magnitude of this difference was not only more reduced in the case of the hemoglobins than in that of the subunits but the spectra of both the oxy and deoxy derivatives of the hemoglobins were characteristic of the oxy derivative of a cooperative tetrameric hemoglobin. These findings support the premise that the COOH-terminal end of the beta or gamma chain contributes, although possibly to different extents, to the spectral differences exhibited by both the spin-labeled hemoglobins and chains.

Carboxypeptidases↗
PubMed1976

Kinetic studies on the binding affinity of human hemoglobin for the 4th carbon monoxide molecule, L4.

L4, the affinity of hemoglobin for the 4th CO molecule, has been determined for human adult hemoglobin (HbA) as a function of pH and the presence of organic phosphates by measuring the kinetic parameters for the reaction. l'4, the rate of combination of CO with the triliganded molecule, was measured by flash photolysis while l4, the rate of CO dissociation for the ligand-saturated molecule, was measured by ligand replacement. L4 is pH-dependent and affected by 2,3-diphosphoglycerate. Additionally, this pH dependence of the high affinity state is largely eliminated by carboxypeptidase A digestion. L4 for human fetal hemoglobin (HbF) in phosphate buffers was also determined and found to be pH-dependent. These results cannot be reconciled within the framework of the two-state allosteric model. Additional structures in the conformational equilibrium due to either intermediates in the T to R transition or two or more R states must exist.

Binding Sites↗
PubMed1976

The virtual absence of antigenic cross-reactivity between functionally distinct trout hemoglobins.

The antigenic properties of the hemoglobins of two species of rainbow trout, Salmo irideus and Salmo gairdneri, have been compared. Each of these species possess two different classes of hemoglobins, the members of the first of which have no Bohr effect while those of the second exhibit a pronounced pH dependence of their ligand affinities. The hemoglobins from these two species are antigenically indistinguishable. However, between the two classes of hemoglobins there is almost no immunological cross-reactivity.

Animals↗
PubMed1975

Structural states and transitions of carp hemoglobin.

The wide ligand affinity range previously observed for carp hemoglobin is bounded at both extremes by regions of constant affinity. Within these regions, pH, organic phosphates, and the extent of ligand binding have no effect on the measured affinity and the cooperativity of ligand binding is greatly reduced or absent. The rates of CO recombination to fully and partially unliganded carp hemoglobin, under various organic phosphate and pH conditions, are shown to reflect this behavior. Constant kinetic rates are seen to directly correspond to the regions of constant affinity. Therefore, these are taken to be single protein conformations, one of high and one of low ligand affinity. In the simplest view, these conformations represent the R and T states of a two-state model, and most of the properties of carp hemoglobin are explained quite well within this framework. Increases in either hydrogen or phosphate ion concentrations favor the stabilization of the low affinity structure of even fully liganded carp hemoglobin. We have studied the structural transition from high to low affinity by monitoring the absorption spectra of carp hemoglobins at constant pH as a function of organic phosphate concentration. We find that different spectra are induced in both carp methemoglobin and cyanomethemoglobin by inositol hexaphosphate addition. Furthermore, the dependence of the magnitude of the spectral changes on pH and organic phosphate concentration is the close agreement with that predicted from studies of the ligand binding properties of the molecule.

Animals↗