Search results for "Hemoglobin"
showing 10 items of 504 documents
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…
Protein dynamics: conformational disorder, vibrational coupling and anharmonicity in deoxy-hemoglobin and myoglobin.
1993
In this work we study the temperature dependence of the Soret band lineshape of deoxymyoglobin and deoxyhemoglobin, in the range 300-20 K. To fit the measured spectra we use an approach originally proposed by Champion and coworkers (Srajer et al. 1986; Srajer and Champion 1991). The band profile is modelled as a Voigt function that accounts for the coupling with low frequency vibrational modes, whereas the coupling with high frequency modes is responsible for the vibronic structure of the spectra. Moreover, owing to the position of the iron atom out of the mean heme plane, inhomogeneous broadening brings about a non-Gaussian distribution of 0-0 electronic transition frequencies. The reporte…
Dynamic properties of some β-chain mutant hemoglobins
1995
The thermal behavior of the Soret band relative to the carbonmonoxy derivatives of some beta-chain mutant hemoglobins is studied in the temperature range 300-10 K and compared to that of wild-type carbonmonoxy hemoglobin. The band profile at various temperatures is modeled as a Voigt function that accounts for homogeneous broadening and for the coupling with high- and low-frequency vibrational modes, while inhomogeneous broadening is taken into account with a gaussian distribution of purely electronic transition frequencies. The various contributions to the over-all bandwidth are singled out with this analysis and their temperature dependence, in turn, gives information on structural and dy…
Structure-dynamics-function relationships in Asian elephant (Elephas maximus) myoglobin. An optical spectroscopy and flash photolysis study on functi…
1993
In this work we report the thermal behavior (10–300 K) of the Soret band lineshape of deoxy and carbonmonoxy derivatives of Asian elephant (Elephas maximus) and horse myoglobins together with their carbon monoxide recombination kinetics after flash photolysis; the results are compared to analogous data relative to sperm whale myoglobin. The Soret band profile is modeled as a Voigt function that accounts for the coupling with high and low frequency vibrational modes, while inhomogeneous broadening is taken into account with suitable distributions of purely electronic transition frequencies. This analysis makes it possible to isolate the various contributions to the overall lineshape that; in…
Spinodal lines and Flory-Huggins free-energies for solutions of human hemoglobins HbS and HbA
1991
Gelation of deoxygenated solutions of sickle-cell human Hemoglobin (HbS) is of high theoretical interest and it has serious pathological consequences. For this reason HbS is probably the most studied protein capable of self-organization. This notwithstanding, the location in the T, c plane of the region of thermodynamic instability of solutions of deoxy-HbS (as bounded by the spinodal line and as distinct from the gelation region) has remained unknown, along with related values of Flory-Huggins enthalpies and entropies. In the present work this information is derived from experiments for the two cases of (deoxy) HbS and of human adult hemoglobin (HbA). Experiments also show critical exponen…
Rational backbone redesign of a fructosyl peptide oxidase to widen its active site access tunnel
2020
Fructosyl peptide oxidases (FPOXs) are enzymes currently used in enzymatic assays to measure the concentration of glycated hemoglobin and albumin in blood samples, which serve as biomarkers of diabetes. However, since FPOX are unable to work directly on glycated proteins, current enzymatic assays are based on a preliminary proteolytic digestion of the target proteins. Herein, to improve the speed and costs of the enzymatic assays for diabetes testing, we applied a rational design approach to engineer a novel enzyme with a wider access tunnel to the catalytic site, using a combination of Rosetta design and molecular dynamics simulations. Our final design, L3_35A, shows a significantly wider …
Ventilatory chemosensitivity, cerebral and muscle oxygenation, and total hemoglobin mass before and after a 72-day mt. Everest expedition.
2014
Abstract. Cheung, Stephen S, Niina E. Mutanen, Heikki M. Karinen, Anne S. Koponen, Heikki Kyro ̈ la ̈ inen, Heikki O. Tikkanen, and Juha E. Peltonen. Ventilatory chemosensitivity, cerebral and muscle oxygenation, and total hemoglobin mass before and after a 72-day Mt. Everest expedition. High Alt Med Biol 15:331–340, 2014.— Background: We investigated the effects of chronic hypobaric hypoxic acclimatization, performed over the course of a 72-day self-supported Everest expedition, on ventilatory chemosensitivity, arterial saturation, and tissue oxygenation adaptation along with total hemoglobin mass (tHb-mass) in nine experienced climbers (age 37 – 6 years, _ VO 2peak 55 – 7mL $ kg - 1 $ min…
Changes in Salivary Amylase and Glucose in Diabetes: A Scoping Review
2021
Background and Objective: Diabetes mellitus (DM) is a common long-term disease which can be related with salivary amylase levels. DM has recently been associated with salivary amylase diagnostics that could further impair diagnoses in the diabetic population, as well as being an interesting alternative to traditional methods of determine glucose levels. The main advantage of this method is related to the fact that it is a fast diagnostic method. The DM population experiences changes to their metabolism which affects their salivary parameters, making this an alternative procedure for diagnosis and follow-up of the illness due to the non-invasive nature of salivary analyzes. The objective of …
Active site conformation in the αH87G mutant hemoglobin: An optical absorption and FTIR study
2000
We have studied the active site conformation in the carbonmonoxy derivative of the αH87G mutant hemoglobin by means of optical absorption and FTIR spectroscopies. A red shift (≈30 cm−1) of the Soret band peak frequency, together with a concomitant red shift (≈2 cm−1) of the bound CO stretching frequency has been observed for the mutant protein. This indicates an altered electrostatic environment of the heme group in the mutated subunits. In view of the FTIR data showing that the bound CO molecule experiences an increased positive electrostatic field, we attribute the observed effects to a closer interaction of the CO ligand with the partially positively charged imidazole side chain of the p…
8 Å cryo-EM structure of the giant hemoglobin from the planorbid snail Biomphalaria glabrata
2008
Until 2006, snail red hemoglobin remained a phylogenetic enigma because it occurs quite isolated in a single gastropod family, the Planorbidae, whereas all other gastropods use blue hemocyanin as a respiratory protein (for recent cryo-EM of hemocyanin, see [1,2]). Moreover, sequence data on this snail hemoglobin were completely lacking. In 2006, our group published the complete cDNA and predicted amino acid sequence of two Biomphalaria glabrata hemoglobin polypeptides, termed BgHb1 and BgHb2 [3]. (Biomphalaria is intermediate host of the human parasite Schistosoma mansoni that causes Bilharziosis.) Resembling pearl-chains, both polypeptide subunits encompass 13 different, cysteine-free glob…