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Human hemoglobin cross-linked through the polyphosphate-binding site. Functional properties and evidence for conformers.
No full textThe properties of human hemoglobin reacted with 2-nor-2-formylpyroxidal 5'-phosphate, a bifunctional derivative of pyroxidal 5'-phosphate, have been investigated both from an equilibrium and kinetic point of view. The experimental data, interpreted in terms of the two-state allosteric model, indicate that a perturbed R state is characteristic of this modified low ligand affinity hemoglobin. In flash photolysis experiments, a quickly reacting component is always observed, in spite of the lack of dissociation into free dimers; this kinetic behavior is thought to reflect the presence of functionally independent αβ dimers, still connected by the flexible cross-link but forming an open hemoglobin tetramer. Two possible models for the interpretation of the kinetics of CO and/or haptoglobin binding are presented and discussed
Xenopus laevis hemoglobin and its hybrids with hemoglobin A+.
No full textIsolated α and βchains from Xenopus laevis hemoglobin have been purified. The isolation procedure yields native α chains whose functional behavior has been characterized and compared with that of human α chains. Isolated β chains in the presence of oxygen are characterized by low stability, and hence their functional characterization was limited to the CO binding kinetics. When stoichiometric amounts of the isolated α and β chains are mixed, a tetramer characterized by heme-heme interactions and oxygen affinity comparable to that of the native molecule is readily reconstituted. Moreover, both chains, under appropriate conditions, form stable hybrid tetramers with the partner subunits from human hemoglobin; results on the functional properties of these hybrid hemoglobins are presented and discussed in relation to the stereochemical model of the Root effect
Tadpole Xenopus laevis hemoglobin. Correlation between structure and functional properties.
No full textPerutz & Brunori (1982) proposed that the COOH-terminal His and Ser F9 of the β-chains of fish and amphibian hemoglobins are responsible for their Root effect and part of their alkaline Bohr effect. Analysis of the kinetics of carbon monoxide binding by hemoglobin from the tadpole of Xenopus laevis supports that model and suggests an explanation for the absence of an alkaline Bohr effect in many aquatic Anura and Urodel
Lobster hemocyanin: influence of acclimatization on subunit composition and functional properties
No full textA comparative study of the temperature dependence of the oxygen-binding properties of mammalian hemoglobins
No full textOn the oxygen-linked anion-binding sites in human hemoglobin. Functional properties of human hemoglobin reacted with 4-isothiocyanatobenzenesulphonic acid and its hybrids.
No full textHuman hemoglobin, reacted at the four amino termini with 4-isothiocyanatobenzenesulphonic acid (Hb-ICBS), was separated into its constituent chains. Recombination of the ICBS-reacted chains with the unmodified mate chains produced the hybrid tetramers modified at either the beta or the alpha chains: alpha 2 beta 2ICBS and alpha 2ICBS beta 2. All of the modified tetramers show a reduced oxygen affinity and reduced cooperativity; furthermore the oxygen affinity of the Hb-ICBS and alpha 2 beta 2ICBS is unaffected by 2,3-bisphosphoglycerate while the oxygen affinity of alpha 2ICBS beta 2 is decreased in the presence of this organic phosphate. The oxygen affinity of Hb-ICBS and alpha 2ICBS beta 2 is independent of chloride concentration, while the alpha 2 beta 2ICBS hybrid shows a reduced response to this anion. The tetramers alpha 2ICBS beta 2 and alpha 2ICBS beta 2ICBS show a decreased alkaline Bohr effect, which can be rationalized as being due to disruption of the oxygen-linked chloride-binding sites; in the case of alpha 2 beta 2ICBS the Bohr effect is instead (partially) maintained. The functional properties of artificial tetramers have been studied also from a kinetic point of view by CO combination and the results obtained compare satisfactorily with equilibrium data. The possibility of obtaining selectively modified hemoglobins promises to provide further insight into the properties of the oxygen-linked anion-binding sites in hemoglobin
Spectroscopic properties of the nitric oxide derivative of ferrous man, horse, and ruminant hemoglobins: a comparative study
No full textPeriodontal bacteria in the genital tract: are they related to adverse pregnancy outcome?
No full textOne of the most important factors implicated in preterm birth (PTB) is acute genitourinary tract infection. The bacteria causing chronic periodontal inflammation include Gram-negative rods and anaerobes similar to those found in women with bacterial vaginosis. The aim of this prospective study is to investigate the relationship between oral and vaginal microflora and preterm low birth weight. Real-time polymerase chain reaction was used to detect both the presence and level of six periodontitis-related species: Aggregatibacter actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), Tannerella forsythia (Tf), Treponema denticola (Td), Fusobacterium nucleatum ssp(Fn), and Prevotella intermedia (Pi) for both oral samples of subgingival plaque and cervical samples, obtained from 80 patients, during gynaecological examinations. The more representative oral pathogen (less than 60 percent) species in oral samples of preterm and term group were Tf, Td, and Fn. 24.4 percent of pregnant women presented periodontal pathogens in vaginal swab; the most representative species with a percentage over 0.1 percent of total bacteria in genital tract of preterm group were Tf, Td, and Piwith a positive correlation (less than 0.5). The presence of the bacterium T. denticolain the vagina, regardless of the amount, adversely affects preterm delivery
Effect of inositol hexakisphosphate on the spectroscopic properties of the nitric oxide derivative of ferrous horse and bovine hemoglobin
No full textFunctional, spectroscopic and structural properties of haemoglobin from chamois (Rupicapra rupicapra) and steinbock (Capra hircus ibex)
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