Effect Of Organic Phosphates Research Articles

Effects of myo-inositol hexakisphosphate, ferrihydrite coating, ionic strength and pH on the transport of TiO2 nanoparticles in quartz sand

Evaluating the fate and transport of nanoparticles (NPs) in the subsurface environment is critical for predicting the potential risks to both of the human health and environmental safety. It is believed that numerous environmental factors conspire to control the transport dynamics of nanoparticles, yet the effects of organic phosphates on nanoparticles transport remain largely unknown. In this work, we quantified the transport process of TiO2 nanoparticle (nTiO2) and their retention patterns in water-saturated sand columns under various myo-inositol hexakisphosphate (IHP) or phosphate (Pi) concentrations (0–180 μM P), ferrihydrite coating fractions (λ, 0–30%), ionic strengths (1–50 mM KCl), and pH values (4–8). The transport of nTiO2 was enhanced at increased P concentration due to the enhanced colloidal stability. As compared with Pi at the equivalent P level, IHP showed stronger effect on the electrokinetic properties of nTiO2 particles due to its relatively more negative charge and higher adsorption affinity, thereby facilitating the nTiO2 transport (and thus reduced retention) in porous media. At the IHP concentration of 5 μM, the retention of nTiO2 increased with increasing λ and ionic strength, while decreased with pH. In addition, the retention profiles of nTiO2 showed a typical hyperexponential pattern for most scenarios mainly due to the unfavorable attachment, and can be well described by a hybrid mathematical model that coupled convection dispersion equations with a two-site kinetic model and DLVO theory. These quantitative estimations revealed the importance of IHP on affecting the transport of nTiO2 typically in phosphorus-enriched environments. It provides new insights into advanced understanding of the co-transport of nanoparticles and phosphorus in natural systems, essential for both nanoparticle exposure and water eutrophication.

Influence of the A Helix Structure on the Polymerization of Hemoglobin S

Hb S variants containing Lys-beta132 --> Ala or Asn substitutions were engineered to evaluate the consequences of the A helix destabilization in the polymerization process. Previous studies suggested that the loss of the Glu-beta7-Lys-beta132 salt bridge in the recombinant Hb betaE6V/E7A could be responsible for the destabilization of the A helix. The recombinant Hb (rHb) S/beta132 variants polymerized with an increased delay time as well as decreased maximum absorbance and Hb solubility values similar to that of Hb S. These data indicate that the strength of the donor-acceptor site interaction may be reduced due to an altered conformation of the A helix. The question arises whether this alteration leads to a true inhibition of the polymerization process or to qualitatively different polymers. The oxygen affinity of the beta132 mutated rHbs was similar to that of Hb A and S, whereas the cooperativity and effects of organic phosphates were reduced. This could be attributed to modifications in the central cavity due to loss of the positively charged lysine. Since Lys-beta132 is involved in the stabilization of the alpha1-beta1 interface, the loss of the beta132(H10)-beta128(H6) salt bridge may be responsible for the marked thermal instability of the beta132 mutated rHbs.

Cell-Free Hemoglobin as an Oxygen Carrier Removes Nitric Oxide, Resulting in Defective Thromboregulation

Development of a clinically safe and effective substitute for erythrocytes that is capable of efficient oxygen delivery in vivo has progressed to the stage where cross-linked hemoglobin preparations are now undergoing clinical trials.1 Such preparations withstand storage for prolonged periods of time, can be administered without the need for cross-matching, and are free of contamination by infectious agents. Utilization of cell-free hemoglobin as an erythrocyte substitute was initially hampered by nephrotoxicity and an affinity for oxygen that prevented efficient oxygen delivery to tissues.2 These disadvantages were overcome when Bunn and Jandl3 chemically cross-linked the hemoglobin molecule to produce stable hemoglobin oligomers that do not pass through the glomerular filtrate. In addition, Benesch and Benesch4 developed reagents that modified the 2,3-diphosphoglycerate binding site of hemoglobin, thereby reducing its oxygen affinity. Administration of cell-free hemoglobin solutions results in systemic vasoconstriction in research animals.5 This is thought to be a consequence of the high avidity of hemoglobin for nitric oxide (NO, endothelium-derived relaxing factor [EDRF]), which it binds and inactivates. The NO-hemoglobin interaction results in rapid formation of nitrite/nitrate and methemoglobin. This blocks vasodilation induced by …

Role of gamma 87 Gln in the inhibition of hemoglobin S polymerization by hemoglobin F

Previous studies suggested that gamma 87 Gln in hemoglobin (Hb) F is an important site for promoting inhibition of Hb S (alpha 2 beta 2(6 Glu-->Val) polymerization by Hb F. We engineered and isolated the double mutant (Hb alpha 2 beta 2(6 Glu-->Val,87 Thr-->Gln) using a yeast expression system and characterized polymerization properties of this modified tetramer in an effort to clarify the role of Gln at position 87 in inhibiting Hb S polymerization. Electrophoretic mobility and absorption spectra of this double mutant were the same as that of Hb S, while oxygen affinity was higher, and effects of organic phosphates on oxygen affinity were reduced. The deoxy form of the double mutant showed a characteristic delay time prior to polymerization in vitro. The critical concentration for polymerization of the double mutant was about 1.5 times higher than Hb S, and delay and polymerization times were much longer than Hb S at the same hemoglobin concentrations. The logarithmic plot of delay time versus hemoglobin concentration for the double mutant showed a straight line that was intermediate between lines for AS and FS mixtures. These results and those of kinetics of polymerization of Hb S/double mutant mixtures indicate that substitution of Gln for Thr at beta 87 in Hb S prolongs delay time and inhibits polymerization, although the double mutant forms polymers like Hb S.

Angina Pectoris Caused by Pernicious Anemia

Angina Pectoris Caused by Pernicious Anemia

Arctic life and adaptation—III. the function of whale ( Balaenoptera acutorostrata) hemoglobin

1. 1. The oxygen binding properties of the hemoglobin from the Lesser Rorqual, Balaenoptera acutorostrata, has been investigated with respect to the possible effects of organic phosphates on gas transport in arctic environments. 2. 2. The intrinsic oxygen affinity of the hemoglobin is high and strongly modulated by the effects of organic phoshates. 3. 3. In the absence of organic phosphates, the temperature sensitivity of oxygen binding expressed by the heat of oxygenation, ΔH is − 16.2 kcal/mol when corrected for the heat of oxygen in solution. 4. 4. In the presence of organic phosphates there is a marked decreased in the temperature sensitivity ΔH ∼ − 5 kcal/mol) . 5. 5. This feature is of great importance for oxygen unloading in the flippers and the tail, where the temperature is lower than the trunk of the whale. 6. 6. Furthermore the organic phoshates strongly increase the Bohr coefficient, Δlog P 50/Δ pH , from less than −0.3 in stripped hemoglobin to about −1.5 when the hemoglobin is saturated with P 6-inositol. 7. 7. This feature may be of great physiological importance by reducing the CO 2 tension and acidosis after a prolonged dive.

Oxidation of hemoglobin and myoglobin by alkyl nitrites inhibition by oxygen.

The reactions of human hemoglobin and sperm whale myoglobin with ethyl nitrite under aerobic conditions have been examined in kinetic detail. Ethyl nitrite converts two equivalents of oxyhemoglobin or oxymyoglobin to their oxidized counterparts with concurrent production of one equivalent each of molecular oxygen, nitrate ion, and ethyl alcohol. Inverse first order kinetic dependence on the concentration of molecular oxygen has been observed and is interpreted by a mechanism in which oxygen dissociation from the oxyhemoprotein occurs prior to rate-limiting oxidation by ethyl nitrite. The rate constant for ethyl nitrite oxidation of hemoglobin from which the fourth oxygen has dissociated is calculated to be 45 times greater than the corresponding rate constant for oxidation of deoxyhemoglobin. This rate enhancement is proposed to be a reflection of the oxidative susceptibility of the R and T conformational states of hemoglobin. Results obtained for the oxidation of myoglobin confirm this interpretation as do kinetic data for hemoglobin and myoglobin oxidations by iron(III) and copper(II) complexes. The effects of organic phosphates on rates for hemoglobin oxidations are interpreted in terms of oxidation inhibition by molecular oxygen.

Nucleation-controlled aggregation of deoxyhemoglobin S effect of organic phosphates on the kinetics of aggregation of deoxyhemoglobin S in concentrated phosphate buffer

The kinetics of the aggregation of deoxyhemoglobin S in concentrated phosphate buffer were studied turbidimetrically in the presence of organic phosphates. The addition of inositol hexaphosphate shortened the delay time by 35–80%, the range depending on the hemoglobin concentration. The logarithmic plot of delay time versus hemoglobin concentration in 1.85 M potassium phosphate buffer, pH 7.34, showed a linear relationship with a slope ( n value) of 2.5 ± 0.14 in the absence of inositol hexaphosphate, while the slope was decreased to 2.1 in the presence of inositol hexaphosphate. The turbidity ( A 700) of aggregates per g deoxy Hb S was found to be lower in the presence of inositol hexaphosphate than in the absence of inositol hexaphosphate. The solubility of deoxy Hb S was decreased by inositol hexaphosphate. 2,3-Diphosphoglyceric acid also showed an effect similar to that of inositol hexaphosphate. However, if the pentacyclohexylammonium salt of diphosphoglyceric acid were used, the delay time was increased significantly. The opposite effect of the pentacyclohexylammonium salt of diphosphoglyceric acid on the delay time was found to be attributed to the anti-gelation effect of the pentacyclohexoxylammonium ion. The difference in the effect of inositol hexaphosphate and diphosphoglyceric acid on the delay time appears to be related to their effect on the solubility of deoxy Hb S.

Effect of organic phosphates on the sulfhydryl reactivities of oxyhemoglobins A and S.

The beta 93 sulfhydryl groups of oxyhemoglobins A and S display a difference in reactivity with 5,5'-dithiobis-2-nitrobenzoic acid. It is concluded that this difference arises from differences in tertiary structure in the vicinity of the beta 93 site. Organic phosphates decrease the beta 93 sulfhydryl reactivity. We have used this effect to measure the organic phosphate binding constants. Hemoglobin S binds organic phosphates very weakly compared to hemoglobin A. This result indicates that the structure at the organic phosphate binding site is different in the two oxyhemoglobins and may be the result of differences in the structure of the NH2-terminal ends of the beta chains.

The effect of organic phosphates on the oxygen equilibrium function of hemoglobin M Iwate.

Hemoglobin M Iwate is a mutant in which the proximal histidine residue (F8) of the α chain is replaced by tyrosine. One of consequences of this mutation is the oxidation of the iron atom of the α chain, while the β chain of the tetramer remains in the ferrous state, capable of binding oxygen. NMR experiments (1) and X ray analysis (2) have shown that the quaternary structure of this mutant hemoglobin is almost frozen in the T state, no matter whether its normal β hemes are unliganded or liganded, in solution as well as in the crystal. Baldwin has estimated the allosteric equilibrium constant for Hb M Iwate in phosphate buffer as about 105 in favor of the T state (3). It was of interest, therefore, to see the effect of organic phosphate on the oxygen equilibrium function of ferrous β hemes of the mutant.

Enzymatic methemoglobin reduction - effect of organic phosphate

The enzymatic reduction of aquomethemoglobin A, A 1C, fluoro-methemoglobin A (high spin) and cyanomethemoglobin A (low spin) by NADH-methemoglobin reductase was studied in the presence and absence of IHP and NaCl. It is shown that at alkaline pH, IHP accelerates the rate of reduction of high spin methemoglobins only. This effect is specific for IHP and cannot be produced by NaCl, although NaCl does exert similar effect as IHP at acid pH. Blocking of the NH 2- termini of β-chains (Hb A 1C) does not alter the effect of IHP on methemoglobin reduction.

The effect of organic phosphates on the drying rate of grass leaves and dry-matter losses during drying

SummaryTri-w-butyl phosphate has previously been shown to increase the drying rate of cut grass leaves. It also markedly inhibited respiration and thus reduced loss of dry matter during drying. In the work reported here, some other commercially available phosphate esters were tested for the same effects, except for the inhibition of respiration. Four mixtures of ethoxylated phosphate esters increased the drying rate of excised S. 24 perennial ryegrass leaves, and three of these also reduced the loss of dry matter during drying.The results suggest the possibility of devising single chemical treatments for both increasing the drying rate and reducing the respiration rate of forage crops conserved by drying in the field. The potential advantages of such treatments, together with the difficulties of realizing these advantages in practice, are briefly discussed.

The Effects of Organic Phosphates and Univalent Cations on the Activity of Adenylate Deaminase from Rabbit Skeletal Muscle

The Effects of Organic Phosphates and Univalent Cations on the Activity of Adenylate Deaminase from Rabbit Skeletal Muscle

Opposite effect of organic phosphates on hemoglobin oxidation by hydroxylamine under aerobic and anaerobic conditions.

The effect of organic phosphates such as inositol hexaphosphate (IHP), ATP, and 2,3-diphosphoglycerate (2,3-DPG) on hemoglobin oxidation by hydroxylamine was studied under aerobic and anaerobic conditions. Under aerobic conditions, the oxidation rate of hemoglobin by hydroxylamine was accelerated as much as about 1.6 times, 1.4 times, and 1.4 times in the presence of IHP, ATP, and 2,3-DPG, respectively; however, under anaerobic conditions it was inhibited as much as 2.2 times, 2 times, and 2 times in the presence of these organic phosphates compared with the case for the absence of these organic phosphates. The effects of these organic phosphates on hemoglobin oxidation by hydroxylamine under aerobic conditions were elucidated by the two state models of hemoglobin including the R and the T state, however, the opposite effects under anaerobic conditions cannot be explained without the assumption of the existence of a third conformation of hemoglobin. The dissociation constant of IHP to deoxyhemoglobin was estimated from the rate of the hemoglobin oxidation by hydroxylamine in different concentrations of IHP under anaerobic conditions.

Effects of organic phosphate on the growth and morphology of Scenedesmus obtusiusculus (Chlorophyceae)

Abstract Growth and morphogenic responses of Scenedesmus obtusiusculus to organic and inorganic forms of phosphate were investigated in laboratory cultures. Organic phosphate (as glycerophosphate) supports a higher rate of growth than does inorganic phosphate. Colony production in excess of 90% was achieved with actively growing cultures utilizing an organic phosphate source. Although algae like S. obtusiusculus are commonly observed in field collections, these organisms resist colony formation in laboratory culture. Unsuccessful laboratory attempts to control colony formation with these spineless polymorphic algae have utilized inorganic phosphates. However, in nature most phosphorus is in organic forms and their use in laboratory media should more closely approximate conditions in freshwater. The form of phosphate is a morphogenic factor with S. obtusiusculus and may operate similarly with other micro-algae.

Effect of organic phosphates on methemoglobin reduction by ascorbic acid.

The rate of methemoglobin reduction by ascorbic acid was accelerated in the presence of ATP,2,3-diphosphoglycerate (2,3-DPG), and inositol hexaphosphate (IHP). The acceleration was as much as three times, four times, and ten times in the presence of ATP, 2.3-DPG, and IHP at pH 7.0, respectively. The changes of the concentrations of methemoglobin and ascorbic acid during the methemoglobin reduction were determined, and the reaction was found to proceed stoichiometrically in the presence of IHP. The reduction rate of methemoglobin by ascorbic acid was compared at different concentrations of organic phosphates (ATP,2,3-DPG, and IHP) at various pH values (6.3, 7.0, 7.7). From the changes in the reduction rate under different concentrations of organic phosphates, the dissociation constants of ATP, 2,3-DPG, and IHP to methemoglobin could be determined and were estimated to be 3.3 X 10(-4) M, 2 X 10(-3) M, and 8 X 10(-6) M at pH 7.0, respectively. On the basis of these results, the acceleration mechanism of methemoglobin reduction by ascorbic acid due to the presence of organic phosphates was described. The physiological role of 2,3-DPG in human red cells was discussed in relation to the reduction of methemoglobin by ascorbic acid.

Kinetics of co-operative ligand binding in proteins: The effects of organic phosphates on hemoglobin oxygenation

A master equation approach to the kinetics of co-operative ligand binding reactions in proteins is developed. As a specific example, equations based on the Perutz description are applied to several reactions of hemoglobin, both in the absence and in the presence of organic phosphates. The observed time dependence of O 2 binding to stripped hemoglobin is fitted with a total of four parameters, of which two are held fixed at values determined from the experimentally measured rate constants for the last step of ligand binding. An analysis of Gibson's data (1970a) for oxygen-binding kinetics of unstripped hemoglobin shows that phosphate binding not only stabilizes the deoxy quaternary conformation of hemoglobin but also increases both the strength of the quaternary conformational constraints and the kinetic time scaling parameter for the deoxy quaternary conformation. A single set of five parameters is used to fit the deoxygenation data of Salhany et al. (1970) in the presence of varying concentrations of P 2Glyc § § Abbreviations used: P in2Glyc, 2,3-diphosphoglycerate; IHP, inositol hexaphosphate; HPT, 8-hydroxy-l,3,6-pyrenetrisulfonate; Hb, hemoglobin. . The five parameters are determined by fitting the theory to the data in the absence of P 2Glyc and at a single concentration of P 2Glyc. The predictive ability of the model is then tested by using these same parameter values to calculate the curves for intermediate P 2Glyc concentrations, and then comparing the predicted curves with experimental data. Whereas deoxygenation data in the presence of P 2Glyc can be fitted with the subunits considered as equivalent, we find that α, β subunit inequivalence is particularly important in interpreting deoxygenation data in the presence of the inhibitor, IHP. Since the phosphate dependence of the reaction is explicitly included, the model can also describe biphasic deoxygenation, as observed by Gray & Gibson (1971) for the deoxygenation reaction in the presence of IHP. In the deoxygenation reaction, the quaternary conformation is found to change from oxy to deoxy just prior to the release of the second oxygen molecule; the switch occurs somewhat earlier in the presence of organic phosphates. As a consequence of this switch, the release of oxygen lags behind the binding of organic phosphates; the lag is more pronounced for IHP than for P 2Glyc. The analogous result of MacQuarrie & Gibson (1972) concerning the lag between the release of HPT and binding of CO is well reproduced; the fractional saturation of hemoglobin with CO and the fraction of HPT released are both fitted with a single set of five parameters. The dependence of the Adair (1925a,b) rate constants (for α = β) and Olson-Gibson (1972) rate constants (for α ≠ β) on the concentration of organic phosphate is calculated. It is found that (i) the experimentally observed increase in the overall deoxygenation rate with increasing organic phosphate concentration is primarily due to the increase in the rate of dissociation of the second oxygen molecule, (ii) the “on” rate constants most affected by organic phosphate are k 1′ and k 2′ the rate constants for the binding of the first and second oxygen molecules, (iii) the “off” rate constants, k j , are affected more than the “on” rate constants, k j ′ (iv) the rate constants for the reactions of the β subunits are affected more by IHP than those of the α subunits, and (v) the rate constants involving the intermediate species with two β subunits and one α subunit liganded are influenced the most by the binding of phosphates.

Studies on avian erythrocyte metabolism: Effect of organic phosphates on oxygen affinity of embryonic and adult-type hemoglobins of the chick embryo

The effects of 2,3 diphosphoglyceric acid (2,3-DPG), adenosine triphosphate (ATP), and inositol hexaphosphate (IHP) on the oxygen affinity of whole “stripped” hemoglobin (WSH), hemoglobin H (Hb-H), hemoglobin A (Hb-A) and hemoglobin D (Hb-D) isolated from 18-day chick embryo blood have been determined. The effect of the three organic phosphates upon the oxygen dissociation curves is similar and the following order of decreasing oxygen affinity of the organic phosphates was observed for each hemoglobin: 2,3-DPG < ATP < IHP. 2,3-DPG appears to have a slightly greater effect upon the P 50 of Hb-H than upon that of either of the two adult-type hemoglobins. However, this effect seems insufficient to suggest a preferential interaction of 2,3-DPG with Hb-H which would account for either the large amounts of 2,3-DPG in the erythrocytes of embryos or the higher oxygen affinity of the whole blood. The effects of the organic phosphates upon the Hill constant of the purified hemoglobins are variable. It is concluded that since the distribution of hemoglobins H, A, and D in the erythrocytes during the developmental period from 18-day embryos to 6-day chicks remains fairly constant, the previously described progressive decrease in oxygen affinity of the whole blood during this period results from changes in the total amount and distribution of the intraerythrocytic organic phosphates. 2 2 Abbreviations used: 2,3-DPG, 2,3-diphosphoglyceric acid; IHP, inositol hexaphosphate; IPP, inositol pentaphosphate; Hb-A, major hemoglobin of adult chicken; Hb-D, minor hemoglobin of adult chicken; Hb-H, embryonic or hatching chick hemoglobin; WSH, whole stripped hemoglobin; P 50, pO 2, in millimeters of Hg, required to produce 50% saturation.

The effects of organic phosphates on the oxygenation behavior of eel multiple hemoglobins

1. 1. The effects of guanosine triphosphate (GTP) † † GTP, guanosine triphosphate; ATP, adenosine triphosphate; DPG, 2,3-diphosphoglycerate Hb, hemoglobin. and adenosine triphosphate (ATP) on the oxygenation behavior of the two major hemoglobins of the American eel, Antuilla rostrata, were determined. 2. 2. Both phosphates lower the oxygen affinities of the individual hemoglobins but the effect of GTP is greater than that of ATP. 3. 3. The allosteric effect of these phosphates is more pronounced with HbI than with HbII. 4. 4. Combinations of GTP and ATP at intraerythrocytic ocnentrations lower the oxygen affinities of the pigments to a greater extent than either phosphate alone. 5. 5. Sodium chloride decreases the affinity of HbI but increases the affinity of HbII. 6. 6. The interaction between these phosphates and NaCl in modulating the oxygenation behavior of the multiple hemoglobins of marine and fresh-water eels is discussed.

The effects of inositol hexaphosphate on the allosteric properties of two beta-99-substituted abnormal hemoglobins, hemoglobin Yakima and hemoglobin Kempsey.

Hemoglobins (Hb) Yakima and Kempsey were purified from patients' blood with diethylaminoethyl cellulose column chromatography. The oxygen equilibrium curves of the two hemoglobins and the effects of organic phosphates on the function were investigated. In 0.1 M phosphate buffer, Hill's constants n for Hb Yakima and Hb Kempsey were 1.0 to 1.1 at the pH range for 6.5 to 8.0 and the oxygen affinities of both the mutant hemoglobins were about 15 to 20 times that of Hb A at pH 7.0. The Bohr effect was normal in Hb Yakima and one-fourth normal in Hb Kempsey. In the presence of inositol hexaphosphate, the oxygen affinities to Hb Yakima and Hb Kempsey were greatly decreased, and an interesting result revealed that these hemoglobins showed clear cooperativity in oxygen binding. Hill's constant n in the presence of inositol hexaphosphate was 1.9 for Hb Kempsey and 2.3 for Hb Yakima at pH 7.0. The cooperativities of these mutant hemoglobins were pH-dependent, and Hb Kempsey showed high cooperativity at low pH (n equal 2.1 at pH 6.6) and low cooperativity at high pH (n equal 1.0 at pH 8.0). Hb Yakima showed similar pH dependence in cooperativity. In the presence of inositol hexaphosphate, Hb A showed a pH-dependent cooperativity different from those of Hb Yakima and Hb Kempsey, namely, Hill's n was the highest in alkaline pH (n equal 3.0 at pH 8.0) and decreased at lower pH (n equal 1.5 at pH 6.5). 2,3Diphosphoglycerate bound with the deoxygenated Hb Yakima and Hb Kempsey, however, had no effect on the oxygen binding of these abnormal hemoglobin. The pH-dependent cooperativity of alpha1beta2 contact anomalous hemoglobin and normal hemoglobin was explained by the shifts in the equilibrium between the high and low ligand affinity forms.