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1.
Hongyu Zhang Guanglin Xia Jian Zhang Dalin Sun Zaiping Guo Xuebin Yu 《Liver Transplantation》2018,8(13)
Due to their ultrahigh theoretical capacity, metal borohydrides are considered to be one of the most promising candidate hydrogen storage materials. Their application still suffers, however, from high operating temperature, sluggish kinetics, and poor reversibility. Designing nanostructures is an effective way of addressing these issues, but seeking suitable approaches remains a big challenge. Here, a space‐confined solid‐gas reaction to synthesize Mg(BH4)2 nanoparticles supported on grapheme is reported, which serves as the structural support for the dispersed Mg(BH4)2 nanoparticles. More notably, density functional theory calculations reveal that graphene could weaken both the Mg? H bonds of MgH2 and B? B bonds of B2H6, which could thermodynamically and kinetically facilitate the chemical transformation to synthesize Mg(BH4)2 with high purity. Because of the synergistic effects of both the significant reduction in particle size and the catalytic effect of graphene, an onset dehydrogenation temperature of ≈154 °C is observed for Mg(BH4)2 nanoparticles, and a complete dehydrogenation could be achieved at a temperature as low as 225 °C, with the formation of MgB2 as the by‐product. This work provides a new perspective to tailoring the thermodynamics and kinetics of chemical reactions toward the favorable synthesis of functional inorganic materials. 相似文献
2.
Complex hydrides exhibit various energy‐related functions such as hydrogen storage, microwave absorption, and neutron shielding. Furthermore, another novel energy‐related function was recently reported by the authors; lithium fast‐ionic conduction, which suggests that complex hydrides may be a potential candidate for solid electrolytes in lithium‐ion batteries. This review presents the recent progress in the development of lithium fast‐ionic conductors of complex hydrides. First, the fast‐ionic conduction in LiBH4 as a result of clarifying the mechanism of microwave absorption is presented, and then the conceptual development of complex hydrides as a new type of solid‐state lithium fast‐ionic conductors in LiBH4–, LiNH2–, and LiAlH4‐based complex hydrides is discussed. Finally, the future prospects of this study from both application and fundamental viewpoints are described: possible use as solid electrolytes for batteries, formation of ionic liquids in complex hydrides, and similarity between complex hydrides and Laves‐phase metal hydrides. 相似文献
3.
Han Wang Guotao Wu Hujun Cao Claudio Pistidda Anna‐Lisa Chaudhary Sebastiano Garroni Martin Dornheim Ping Chen 《Liver Transplantation》2017,7(13)
Reversible hydrogen storage over hydrides of light elements (HLEs) under ambient condition has been pursued actively for nearly two decades. However, because of unfavorable thermodynamics and/or severe kinetic barrier of HLEs, limited progress has been made. Here, it is demonstrated that the interaction of LiBH4 with Mg(NH2)2 and LiH, three of the most investigated HLEs, can lead to a fully reversible dehydrogenation/rehydrogenation cycle at temperatures below 373 K. More importantly, with the desorption enthalpy of 24 kJ (mol H2)?1 the dehydrogenation process at 1.0 bar H2 is theoretically possible to be as low as 266 K. Characterization of this combination of HLEs shows that LiBH4 serves as a reagent complexing with intermediates and products of the dehydrogenation of Mg(NH2)2‐LiH, and significantly alters the overall thermodynamic and kinetic properties of the system. 相似文献
4.
A multi‐component catalyst Ni‐VOx/AC (VOx is comprised of V2O5 and VO2, x = 2.18) was synthesized by a wet impregnation method. The synthesized Ni‐VOx/AC shows a superior catalytic effect on de/hydrogenation of Mg. The MgH2+Ni‐VOx/AC composites can absorb 6.2 wt.‐% hydrogen within only 1 min at 150 °C under a hydrogen pressure of 2 MPa and desorb 6.5 wt.‐% hydrogen within 10 min at 300 °C under an initial hydrogen pressure of 1 KPa, which overcomes a critical barrier for practical use of Mg as a hydrogen storage material. A significant decrease of activation energy (Ea) indicates that Ni‐VOx/AC catalyst is highly efficient for Mg de/hydrogenation, which may be ascribed to the synergistic effect of bimetals (metal oxides) and nanocarbon. 相似文献
5.
Calcium borohydride is a potential candidate for onboard hydrogen storage because it has a high gravimetric capacity (11.5 wt.%) and a high volumetric hydrogen content (~130 kg m?3). Unfortunately, calcium borohydride suffers from the drawback of having very strongly bound hydrogen. In this study, Ca(BH4)2 was predicted to form a destabilized system when it was mixed with LiBH4, NaBH4, or KBH4. The release of hydrogen from Ca(BH4)2 was predicted to proceed via two competing reaction pathways (leading to CaB6 and CaH2 or CaB12H12 and CaH2) that were found to have almost equal free energies. Using a set of recently developed theoretical methods derived from first principles, we predicted five new hydrogen storage reactions that are among the most attractive of those presently known. These combine high gravimetric densities (>6.0 wt.% H2) with have low enthalpies [approximately 35 kJ/(mol?1 H2)] and are thermodynamically reversible at low pressure within the target window for onboard storage that is actively being considered for hydrogen storage applications. Thus, the first-principles theoretical design of new materials for energy storage in future research appears to be possible. Figure
Calculated van’t Hoff plot for reactions (10-24*) listed in the Ca-M(Li, Na, K)-B-H system (Tables 2–4). The region within the rectangular box corresponds to desirable temperatures and pressures for on-board hydrogen storage PH2 = 1-700 bar and T = 233 to +355 K 相似文献
6.
Geometrical structures and relative stabilities of (LiNH2)n (n = 1–5) clusters were studied using density functional theory (DFT) at the B3LYP/6-31G* and B3LYP/6-31++G* levels. The electronic
structures, vibrational properties, N–H bond dissociation energies (BDE), thermodynamic properties, bond properties and ionization
potentials were analyzed for the most stable isomers. The calculated results show that the Li–N and Li–Li bonds can be formed
more easily than those of the Li–H or N–H bonds in the clusters, in which NH2 is bound to the framework of Li atomic clusters with fused rings. The average binding energies for each LiNH2 unit increase gradually from 142 kJ mol−1 up to about 180 kJ mol−1 with increasing n. Natural bond orbital (NBO) analysis suggests that the bonds between Li and NH2 are of strong ionicity. Three-center–two-electron Li–N–Li bonding exists in the (LiNH2)2 dimer. The N–H BDE values indicate that the change in N–H BDE values from the monomer a1 to the singlet-state clusters is small. The N–H bonds in singlet state clusters are stable, while the N–H bonds in triplet
clusters dissociate easily. A study of their thermodynamic properties suggests that monomer a1 forms clusters (b1, c1, d2 and e1) easily at low temperature, and clusters with fewer numbers of rings tend to transfer to ones with more rings at low temperature.
E
g, E
HOMO and E
av decrease gradually, and become constant. Ring-like (LiNH2)3,4 clusters possess higher ionization energy (VIE) and E
g, but lower values of E
HOMO. Ring-like (LiNH2)3,4 clusters are more stable than other types. A comparison of structures and spectra between clusters and crystal showed that
the NH2 moiety in clusters has a structure and spectral features similar to those of the crystal. 相似文献
7.
Quantum chemical calculations were performed for LiNH2–HMgX (X?=?H, F, Cl, Br, CH3, OH, and NH2) complexes to propose a new interaction mechanism between them. This theoretical survey showed that the complexes are stabilized through the combinative interaction of magnesium and lithium bonds. The binding energies are in the range of 63.2–66.5 kcal mol?1, i.e., much larger than that of the lithium bond. Upon complexation, both Mg–H and Li–N bonds are lengthened. Substituents increase Mg-H bond elongation and at the same time decrease Li-N bond elongation. These cyclic complexes were characterized with the presence of a ring critical point and natural population analysis charges. Figure
A new interaction mechanism has been suggested for the LiNH2-HMgH complex. It was found that the combinative interaction of magnesium and lithium bonds is responsible for the stability of the complex. The effect of subsitutents on its stability has also been investigated 相似文献
8.
Intraperitoneally injected [14C]biopterin (B), dihydrobiopterin (BH2), and tetrahydrobiopterin (BH4) penetrated the brain rapidly, but in amounts sufficient to represent only a minor source of supply. Unlike isobiopterin, B was rapidly reduced to BH2 in brain. The distribution of BH4 and BH2, but not of B, could be correlated with the tryptophan and tyrosine hydroxylase activity of various cerebral areas. In the whole brain, the sizes of pools were 0.117 for B, 0.204 for BH2, and 0.341 g/g for BH4, while the cerebral turnover rates of B, BH2, and BH4 were 0.25, 0.43, and 0.71 nmol/g per h, respectively. From birth through development, the cerebral levels of B remained constant, whereas the levels of the reduced biopterins increased. After subcellular fractionation, 65% of the biopterins (B, BH2, and BH4) were recovered from the supernatant. Of the organelles, microsomes contained the largest concentration of pterins. About 1/6 of all pterins in the brain was present in the synaptosomes. 相似文献
9.
Ten naturally occurring chlorophylls (a, b, c
2, d) and bacteriochlorophylls (a, b, c, d, e, g) were purified and studied using the optical spectroscopic techniques of both steady state and time-resolved absorption and
fluorescence. The studies were carried out at room temperature in nucleophilic solvents in which the central Mg is hexacoordinated.
The comprehensive studies of singlet excited state lifetimes show a clear dependency on the structural features of the macrocycle
and terminal substituents. The wide-ranging studies of triplet state lifetime demonstrate the existence of an energy gap law
for these molecules. The knowledge of the dynamics and the energies of the triplet state that were obtained in other studies
allowed us to construct an energy gap law expression that can be used to estimate the triplet state energies of any (B)chlorophyll
molecule from its triplet lifetime obtained in a liquid environment. 相似文献
10.
Stephan L. Kohnen Ange A. Mouithys-Mickalad Ginette P. Deby-Dupont Carol M.T. Deby Maurice L. Lamy Alfred F. Noels 《Free radical research》2013,47(6):709-721
The molecular mechanisms of tetrahydrobiopterin (BH4) oxidation by peroxynitrite (ONOO-) was studied using ultra-weak chemiluminescence, electron paramagnetic resonance (EPR) and UV-visible diodearray spectrophotometry, and compared to BH4 oxidation by oxoferryl species produced by the myoglobin/hydrogen peroxide (Mb/H2O2) system. The oxidation of BH4 by ONOO- produced a weak chemiluminescence, which was altered by addition of 50 mM of the spin trap α-(4-pyridyl-1-oxide)-N-tert butylnitrone (POBN). EPR spin trapping demonstrated that the reaction occurred at least in part by a radical pathway. A mixture of two spectra composed by an intense six-line spectrum and a fleeting weak nine-line one was observed when using ONOO-. Mb/H2O2 produced a short-living light emission that was suppressed by the addition of BH4. Simultaneous addition of POBN, BH4 and Mb/H2O2 produced the same six-line EPR spectrum, with a signal intensity depending on BH4 concentration. Spectrophotometric studies confirmed the rapid disappearance of the characteristic peak of ONOO- (302 nm) as well as substantial modifications of the initial BH4 spectrum with both oxidant systems. These data demonstrated that BH4 oxidation, either by ONOO- or by Mb/H2O2, occurred with the production of activated species and by radical pathways. 相似文献
11.
Russell G. Egdell 《Inorganica chimica acta》2008,361(2):462-466
He I and He II PE spectra of Ti(BH4)3 are reported and assigned by reference to density functional calculations on the molecule and cation. The performance of different functionals in predicting the first vertical ionization energy is assessed. Calculations based on hybrid functionals are found to give ionisation energies closer to the experimental value than those using pure density functionals. The accuracy of the ΔSCF method and time dependent density functional theory in calculating higher vertical ionization energies is also examined. 相似文献
12.
Zirconium tetrahydroborate Zr(BH4)4 and its deuteride compound Zr(BD4)4 were successfully synthesized by mechanochemical reaction between NaBH4 or NaBD4 and ZrCl4, reaching yields of 55% and 46%, respectively. The influence of the synthesis parameters on the yield of Zr(BH4)4 was analyzed. The composition of the ZrCl4:NaBH4 starting mixture and the use of LiBH4 instead of NaBH4 as reactive show a clear effect on the Zr(BH4)4 yield. Instead, milling atmosphere does not affect the amount of the obtained product. FTIR analysis of atmosphere inside of milling vial allows to determine the formation of diborane during milling from Zr(BH4)4 decomposition. Thermal stability of pure Zr(BH4)4 and its deuterated compound was studied by combined gas-phase FTIR and DSC measurements under flowing Ar. We found that Zr(BH4)4/Zr(BD4)4 melt at about 305/303 K, decompose at about 430 K from the gas-phase and show evolution of B2H6/B2D6 under heating. 相似文献
13.
Sodium alanate (NaAlH4) is one of the metal complex hydrides most often investigated for use as a hydrogen‐storage material. Doped with transition or rare earth metal compounds, NaAlH4 can absorb and release hydrogen in low and medium temperature ranges with excellent reversibility and cycling stability. The properties of NaAlH4 doped with CeCl3 differ from materials with other dopants, with faster sorption kinetics and a more stable capacity. In this paper, various precursors of Ce are applied to investigate their catalytic effects on the sorption performance of this material. The re‐hydrogenation is found to be completed in approximately 10 min. Although all the Ce precursors investigated in this work result in reversible hydrogen storage materials, desorption kinetics are enhanced upon formation of cerium aluminide (CeAl4) in the composites. While the use of CeAl4 instead of CeCl3 can increase the hydrogen capacity by bypassing the formation of the ineffective NaCl, the highest capacity of 4.9 wt%—close to the theoretical value—is obtained from NaAlH4 doped directly with metallic cerium. Furthermore, dehydriding under back pressures is also investigated to evaluate the H2 desorption rates under practical conditions. At 3 bar H2 pressure, the second desorption step of NaAlH4 is fully suppressed at 150 °C and only 2.5 wt% H was released, whereas at 180 °C the capacity is not much affected, which is interesting for combination in a system with a high‐temperature PEM fuel cell. 相似文献
14.
Liuzhang Ouyang Wei Chen Jiangwen Liu Michael Felderhoff Hui Wang Min Zhu 《Liver Transplantation》2017,7(19)
Sodium borohydride (NaBH4) is regarded as an excellent hydrogen‐generated material, but its irreversibility of hydrolysis and high cost of regeneration restrict its large‐scale application. In this study a convenient and economical method for NaBH4 regeneration is developed for the first time without hydrides used as starting materials for the reduction process. The real hydrolysis by‐products (NaBO2 · 2H2O and NaBO2 · 4H2O), instead of dehydrated sodium metaborate (NaBO2), are applied for the regeneration of NaBH4 with Mg at room temperature and atmospheric pressure. Therefore, the troublesome heat‐wasting process to obtain NaBO2 using a drying procedure at over 350 °C from NaBO2 · xH2O is omitted. Moreover, the highest regeneration yields of NaBH4 are achieved to date with 68.55% and 64.06% from reaction with NaBO2 · 2H2O and NaBO2 · 4H2O, respectively. The cost of NaBH4 regeneration shows a 34‐fold reduction compared to the previous study that uses MgH2 as the reduction agent, where H2 is obtained from a separate process. Furthermore, the regeneration mechanism of NaBH4 is clarified and the intermediate compound, NaBH3(OH), is successfully observed for the first time during the regeneration process. 相似文献
15.
Endothelial dysfunction is associated with increase in oxidative stress and low NO bioavailability. The endothelial NO synthase (eNOS) uncoupling is considered an important factor in endothelial cell oxidative stress. Under increased oxidative stress, the eNOS cofactor tetrahydrobiopterin (BH4) is oxidized to dihydrobiopterin, which competes with BH4 for binding to eNOS, resulting in eNOS uncoupling and reduction in NO production. The importance of the ratio of BH4 to oxidized biopterins versus absolute levels of total biopterin in determining the extent of eNOS uncoupling remains to be determined. We have developed a computational model to simulate the kinetics of the biochemical pathways of eNOS for both NO and O2•− production to understand the roles of BH4 availability and total biopterin (TBP) concentration in eNOS uncoupling. The downstream reactions of NO, O2•−, ONOO−, O2, CO2, and BH4 were also modeled. The model predicted that a lower [BH4]/[TBP] ratio decreased NO production but increased O2•− production from eNOS. The NO and O2•− production rates were independent above 1.5 μM [TBP]. The results indicate that eNOS uncoupling is a result of a decrease in [BH4]/[TBP] ratio, and a supplementation of BH4 might be effective only when the [BH4]/[TBP] ratio increases. The results from this study will help us understand the mechanism of endothelial dysfunction. 相似文献
16.
Mathilde Dubois Estelle Delannoy Lucie Duluc Ellen Closs Huige Li Christian Toussaint Alain-Pierre Gadeau Axel G?decke Véronique Freund-Michel Arnaud Courtois Roger Marthan Jean-Pierre Savineau Bernard Muller 《PloS one》2013,8(11)
Tetrahydrobiopterin (BH4), which fosters the formation of and stabilizes endothelial NO synthase (eNOS) as an active dimer, tightly regulates eNOS coupling / uncoupling. Moreover, studies conducted in genetically-modified models demonstrate that BH4 pulmonary deficiency is a key determinant in the pathogenesis of pulmonary hypertension. The present study thus investigates biopterin metabolism and eNOS expression, as well as the effect of sepiapterin (a precursor of BH4) and eNOS gene deletion, in a mice model of hypoxic pulmonary hypertension. In lungs, chronic hypoxia increased BH4 levels and eNOS expression, without modifying dihydrobiopterin (BH2, the oxidation product of BH4) levels, GTP cyclohydrolase-1 or dihydrofolate reductase expression (two key enzymes regulating BH4 availability). In intrapulmonary arteries, chronic hypoxia also increased expression of eNOS, but did not induce destabilisation of eNOS dimers into monomers. In hypoxic mice, sepiapterin prevented increase in right ventricular systolic pressure and right ventricular hypertrophy, whereas it modified neither remodelling nor alteration in vasomotor responses (hyper-responsiveness to phenylephrine, decrease in endothelium-dependent relaxation to acetylcholine) in intrapulmonary arteries. Finally, deletion of eNOS gene partially prevented hypoxia-induced increase in right ventricular systolic pressure, right ventricular hypertrophy and remodelling of intrapulmonary arteries. Collectively, these data demonstrate the absence of BH4/BH2 changes and eNOS dimer destabilisation, which may induce eNOS uncoupling during hypoxia-induced pulmonary hypertension. Thus, even though eNOS gene deletion and sepiapterin treatment exert protective effects on hypoxia-induced pulmonary vascular remodelling, increase on right ventricular pressure and / or right ventricular hypertrophy, these effects appear unrelated to biopterin-dependent eNOS uncoupling within pulmonary vasculature of hypoxic wild-type mice. 相似文献
17.
The structure and reactivity of cobalt(II), nickel(II), and copper(II) halides have been investigated in 0.20 M CTAX (X = Cl, Br) |CHCl3 reversed micelles. The former two metal ions adopt a tetrahedral configuration at low water concentrations in the micelle. The tetrahedral complexes are converted to octahedral aqua complexes by increasing the water concentration (solvochromism) or by lowering the temperature (thermochromism). Upon reaction with imidazole, the tetrahedral cobalt and nickel halide complexes also undergo a structural transformation into an octahedral configuration with imidazole coordination. At low water concentrations, copper halides form a polynuclear complex bridged by halide ions and these halogen bridges are easily broken upon addition of water or imidazole. The copper complexes produced by reaction with imidazole were deduced to be CuIm2X2 and CuIm4X2 at intermediate and high ligand concentrations, respectively. It was also found that the cupric ion in reversed micelles is readily reduced to the cuprous ion with 2-mercaptoethanol, and the cuprous ion is oxidized to the cupric ion by reaction with hydrogen peroxide. 相似文献
18.
Samples of quinonoid-l -erythrodihydrobiopterin (q-BH2) and quinonoid-6-methyl-dihydro-pterin (q-6-MPH2) were prepared by oxidation of l -erythro-5,6,7,8-tetrahydrobiopterin (BH4) and 5,6,7,8-tetrahydro-6-methylpterin (6-MPH4) and separated from D-erythro-7,8-dihydrobiopterin (7,8-BH2) and 6-methyl-7,8-dihydropterin (7,8-6-MPH2) as well as from the tetrahydropterins on phosphocellulose column by high-pressure liquid chromatography. The quinonoid dihydropterins were identified and quantitated by scan of their ultraviolet absorption and fluorescence emission spectra through their rearrangement to their 7,8-tautomer and also by gas chromatography of their rapidly synthesized trimethylsilyl derivative. Identification was also achieved by the enzymatic reduction of [3H]q-BH2to [3H]BH4 by dihydrofolate reductase (DHFR). Direct proof for the enzymatic synthesis of the q-BH2 from GTP or from 2-amino-6-(5′-triphosphoribosyl)-amino-5- or -6-formamido-6-hydroxypyrimi-dine (FPyd-P3) was obtained by isolation of the compound which was identical in all respects to the q-BH2 obtained by chemical synthesis from BH4. The reduction of enzymatically synthesized q-BH2 by dihydropteridine reductase (DHPR) to BH4 was not inhibited by methotrexate (MTX). When the enzymatically synthesized q-BH2 was converted to 7,8-BH2, it was reduced only by DHFR. This reduction, however, was inhibited by MTX. On the biosynthetic pathway from GTP to dihydrobiopterin, the enzyme responsible for the appearance of the quinonoid structure is the d -erythro-dihydroneopterin triphosphate synthetase, the product of which (quinonoid d -erythro-dihydroneopterin triphosphate) is converted to quinonoid dihydrobiopterin by l -erythro-dihydrobiopterin synthetase. Experiments in vivo established that DHFR does not participate in the reduction of dihydrobiopterin to tetra-hydrobiopterin when the former is synthesized from GTP de novo. MTX at 5 × 10?6M exerted no inhibition on the reduction of the biosynthetic dihydrobiopterin to tetrahydrobiopterin in vivo, yet completely inhibited the reduction of intraventricularly injected tritiated dihydrofolate ([3H]FH2) to tritiated tetrahydrofolate ([3H]FH4). 相似文献
19.
《Inorganica chimica acta》1988,141(1):119-123
Synthesis and characterization of new cobalt-substituted phenylazo 2,4-dinitrosoresorcinol complexes have been carried out. The analytical data depict the formation of complex compounds with the stoichiometry 2:3 (o-COOH, m-NO2) and 1:2 (o-Cl, o-CH3, m-Cl, m-CH3). All the complexes are of low spin in octahedral and square planar or distorted tetrahedral environments. The octahedral ⇄ tetrahedral equilibria are evident. The complexes in the presence of basic compounds gave some addition products. The electronic transitions and the ligand field parameters are assigned and calculated. The complex formation occurred through the azo group and the phenolic oxygen atom in most complexes. In the o-carboxy ligand, the COO−, NN and the oximic groups participate through complexation. 相似文献
20.
Tsin W. Yeo Daniel A. Lampah Enny Kenangalem Emiliana Tjitra Ric N. Price J. Brice Weinberg Keith Hyland Donald L. Granger Nicholas M. Anstey 《PLoS pathogens》2015,11(3)
Tetrahydrobiopterin (BH4) is a co-factor required for catalytic activity of nitric oxide synthase (NOS) and amino acid-monooxygenases, including phenylalanine hydroxylase. BH4 is unstable: during oxidative stress it is non-enzymatically oxidized to dihydrobiopterin (BH2), which inhibits NOS. Depending on BH4 availability, NOS oscillates between NO synthase and NADPH oxidase: as the BH4/BH2 ratio decreases, NO production falls and is replaced by superoxide. In African children and Asian adults with severe malaria, NO bioavailability decreases and plasma phenylalanine increases, together suggesting possible BH4 deficiency. The primary three biopterin metabolites (BH4, BH2 and B0 [biopterin]) and their association with disease severity have not been assessed in falciparum malaria. We measured pterin metabolites in urine of adults with severe falciparum malaria (SM; n=12), moderately-severe malaria (MSM, n=17), severe sepsis (SS; n=5) and healthy subjects (HC; n=20) as controls. In SM, urinary BH4 was decreased (median 0.16 ¼mol/mmol creatinine) compared to MSM (median 0.27), SS (median 0.54), and HC (median 0.34)]; p<0.001. Conversely, BH2 was increased in SM (median 0.91 ¼mol/mmol creatinine), compared to MSM (median 0.67), SS (median 0.39), and HC (median 0.52); p<0.001, suggesting increased oxidative stress and insufficient recycling of BH2 back to BH4 in severe malaria. Overall, the median BH4/BH2 ratio was lowest in SM [0.18 (IQR: 0.04-0.32)] compared to MSM (0.45, IQR 0.27-61), SS (1.03; IQR 0.54-2.38) and controls (0.66; IQR 0.43-1.07); p<0.001. In malaria, a lower BH4/BH2 ratio correlated with decreased microvascular reactivity (r=0.41; p=0.03) and increased ICAM-1 (r=-0.52; p=0.005). Decreased BH4 and increased BH2 in severe malaria (but not in severe sepsis) uncouples NOS, leading to impaired NO bioavailability and potentially increased oxidative stress. Adjunctive therapy to regenerate BH4 may have a role in improving NO bioavailability and microvascular perfusion in severe falciparum malaria. 相似文献