Search results for "Bohr effect"
showing 8 items of 8 documents
Molecular and Functional Characterisation of Hemocyanin of the Giant African Millipede Archispirostreptus gigas
2013
SummaryIn contrast to other terrestrial arthropods where gaseous O2 that fuels aerobic metabolism diffuses to the tissues in tracheal tubes, and most other metazoans where O2 is transported to tissues by circulating respiratory proteins, the myriapods (millipedes and centipedes) strikingly have tracheal systems as well as circulating hemocyanin (Hc). In order to elucidate the evolutionary origin and biological significance of millipede Hc we report the molecular structure (subunit composition and amino acid sequence) of multimeric (36-mer) Hc from the forest-floor dwelling giant African millipede Archispirostreptus gigas and its allosteric oxygen binding properties under various physico-che…
Molecular heterogeneity of the hemocyanin isolated from the king crabParalithodes camtschaticae
2000
Native Paralithodes camtschaticae hemocyanin is found as a mixture of dodecamers (24S; 80%) and hexamers (16S; 20%). Removal of Ca2+ ions by dialysis against EDTA-containing buffer solution at neutral pH induces complete dissociation of the 24S form into the 16S form. Under these conditions, a further increase in pH to 9.2 produces complete dissociation of the hexamers into monomers (5S). In both cases, the dissociation process is reversible. The dodecamer (24S) is composed of two different hexamers which can be discriminated only by ion-exchange chromatography in the presence of Ca2+ ions. At alkaline pH and in the presence of EDTA, two major monomeric fractions can be separated by ion-exc…
The Proton Bohr Factor of Native and Crosslinker Treated Hemoglobins - Its Possible Significance for the Efficacy of Hemoglobin Based Artificial Oxyg…
1994
Especially the (alkaline) proton Bohr effect seems to provide an important self regulating mechanism of the organism to deliver specifically oxygen into tissues suffering from O2 deficit. In this way these tissues switch from aerobic to anaerobic metabolism, get lactacid, thereby shifting oxygen hemoglobin binding curve to the right and thus facilitating the oxygen release. The higher the absolute value of the proton Bohr factor (: delta logP50/ delta pH) is the better this mechanism works. To get one characteristic number the proton Bohr factor at pH 7.1 is taken. This pH in blood is about a lower limit for organism and human blood has at this pH its maximum proton Bohr factor which is abo…
Binding of urate and caffeine to hemocyanin of the lobster Homarus vulgaris (E.) as studied by isothermal titration calorimetry.
2000
Hemocyanin serves as an oxygen carrier in the hemolymph of the European lobster Homarus vulgaris. The oxygen binding behavior of the pigment is modulated by metabolic effectors such as lactate and urate. Urate and caffeine binding to 12-meric hemocyanin (H. vulgaris) was studied using isothermal titration calorimetry (ITC). Binding isotherms were determined for fully oxygenated hemocyanin between pH 7.55 and 8.15. No pH dependence of the binding parameters could be found for either effector. Since the magnitude of the Bohr effect depends on the urate concentration, the absence of any pH dependence of urate and caffeine binding to oxygenated hemocyanin suggests two conformations of the pigme…
Temperature adaptation influences the aggregation state of hemocyanin from Astacus leptodactylus.
2000
When Astacus leptodactylus were kept at various temperatures for several weeks, different ratios between di-hexameric and hexameric hemocyanins were observed in their hemolymph. The higher the temperature the more hexamers were present. This long-term adaptation to different temperatures or/and to temperature-induced pH-shifts as observed in the hemolymph has different effects on the expression of subunit types building up hexamers and those which covalently link two hexamers within the di-hexamers. The oxygen binding behaviour of di-hexameric hemocyanins from cold and warm adapted animals do not show differences with respect to affinity, Bohr effect and cooperativity.
Bohr-effect and buffering capacity of hemocyanin from the tarantula E. californicum.
2003
A previous report showed that binding of oxygen to the 24-meric hemocyanin from E. californicum does not correlate linearly with the release of protons as known from hemoglobin. However, this unusual complex phenomenological observation could not be explained at that time. Here, I present a full analysis of the thermodynamic coupling between protons and oxygen for the 24-meric tarantula hemocyanin in Ringer-solution based on the Nested-MWC-model. A strategy is presented which allows to reduce the number of free parameters when fitting the model to the data by including explicitly the equilibrium constants for binding of protons to the different conformations. The results show that the Neste…
The respiratory gas values of the fetal and maternal blood in cartesian nomograms
1966
Respiratory gas values of maternal and fetal blood taken at delivery are represented in two Cartesian nomograms. They are based on data, published by vogel, fischer und thews (1965) and Fischer, Vogel und Thews (1965). The nomograms depict the interdependence of O2 pressure, O2 content, CO2 pressure and CO2 content, established by the O2 and CO2 dissociation curves, as well as by the Bohr effect and the Haldane effect. If two of the values are known, the remaining ones can be read from the nomograms.
Oxygen binding and its allosteric control in hemoglobin of the primitive branchiopod crustacean Triops cancriformis
2007
Branchiopod crustaceans are endowed with extracellular, high-molecular-mass hemoglobins (Hbs), the functional and allosteric properties of which have largely remained obscure. The Hb of the phylogenetically ancient Triops cancriformis (Notostraca) revealed moderate oxygen affinity, cooperativity and pH dependence (Bohr effect) coefficients: P50 = 13.3 mmHg, n50 = 2.3, and ϕ = −0.18, at 20 °C and pH 7.44 in Tris buffer. The in vivo hemolymph pH was 7.52. Bivalent cations increased oxygen affinity, Mg2+ exerting a greater effect than Ca2+. Analysis of cooperative oxygen binding in terms of the nested Monod–Wyman–Changeux (MWC) model revealed an allosteric unit of four oxygen-binding sites and…