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51.
Chen Liu Nadeem Wajih Xiaohua Liu Swati Basu John Janes Madison Marvel Christian Keggi Christine C. Helms Amber N. Lee Andrea M. Belanger Debra I. Diz Paul J. Laurienti David L. Caudell Jun Wang Mark T. Gladwin Daniel B. Kim-Shapiro 《The Journal of biological chemistry》2015,290(2):1281-1294
Nitrite signaling likely occurs through its reduction to nitric oxide (NO). Several reports support a role of erythrocytes and hemoglobin in nitrite reduction, but this remains controversial, and alternative reductive pathways have been proposed. In this work we determined whether the primary human erythrocytic nitrite reductase is hemoglobin as opposed to other erythrocytic proteins that have been suggested to be the major source of nitrite reduction. We employed several different assays to determine NO production from nitrite in erythrocytes including electron paramagnetic resonance detection of nitrosyl hemoglobin, chemiluminescent detection of NO, and inhibition of platelet activation and aggregation. Our studies show that NO is formed by red blood cells and inhibits platelet activation. Nitric oxide formation and signaling can be recapitulated with isolated deoxyhemoglobin. Importantly, there is limited NO production from erythrocytic xanthine oxidoreductase and nitric-oxide synthase. Under certain conditions we find dorzolamide (an inhibitor of carbonic anhydrase) results in diminished nitrite bioactivation, but the role of carbonic anhydrase is abrogated when physiological concentrations of CO2 are present. Importantly, carbon monoxide, which inhibits hemoglobin function as a nitrite reductase, abolishes nitrite bioactivation. Overall our data suggest that deoxyhemoglobin is the primary erythrocytic nitrite reductase operating under physiological conditions and accounts for nitrite-mediated NO signaling in blood. 相似文献
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54.
Mechanism of Dimercaptosuccinic Acid Coated Superparamagnetic Iron Oxide Nanoparticles with Human Serum Albumin
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Lining Zhao Wei Song Jing Wang Yunxing Yan Jiangwei Chen Rutao Liu 《Journal of biochemical and molecular toxicology》2015,29(12):579-586
To research the mechanism of dimercaptosuccinic acid coated‐superparamagnetic iron oxide nanoparticles (SPION) with human serum albumin (HSA), the methods of spectroscopy, molecular modeling calculation, and calorimetry were used in this paper. The inner filter effect of the fluorescence intensity was corrected to obtain the accurate results. Ultraviolet–visible absorption and circular dichroism spectra reflect that SPION changed the secondary structure with a loss of α‐helix and loosened the protein skeleton of HSA; the activity of the protein was also affected by the increasing exposure of SPION. Fluorescence lifetime measurement indicates that the quenching mechanism type of this system was static quenching. The isothermal titration calorimetry measurement and molecular docking calculations prove that the predominant force of this system was the combination of Van der Waals’ force and hydrogen bonds. 相似文献
55.
Oostenbrink C Soares TA van der Vegt NF van Gunsteren WF 《European biophysics journal : EBJ》2005,34(4):273-284
The quality of biomolecular dynamics simulations relies critically on the force field that is used to describe the interactions between particles in the system. Force fields, which are generally parameterized using experimental data on small molecules, can only prove themselves in realistic simulations of relevant biomolecular systems. In this work, we begin the validation of the new 53A6 GROMOS parameter set by examining three test cases. Simulations of the well-studied 129 residue protein hen egg-white lysozyme, of the DNA dodecamer d(CGCGAATTCGCG)2, and a proteinogenic 3-dodecapeptide were performed and analysed. It was found that the new parameter set performs as well as the previous parameter sets in terms of protein (45A3) and DNA (45A4) stability and that it is better at describing the folding–unfolding balance of the peptide. The latter is a property that is directly associated with the free enthalpy of hydration, to which the 53A6 parameter set was parameterized. 相似文献
56.
IR spectroscopic studies are reported for N-stearyl-d-erythro-phytosphingosine (Cer NP) and N-stearyl-2-hydroxy-d-erythro-phytosphingosine (Cer AP) in a hydrated model of the skin lipid barrier comprised of equimolar mixtures of each ceramide with cholesterol and d35-stearic acid. Examination of the methylene stretching, rocking and bending modes reveal some rotational freedom and hexagonal packing in both the ceramide and stearic acid chains. Analysis of the acid carbonyl stretch and the ceramide Amide I modes show both shift to higher frequencies, indicating weaker hydrogen bonding, in the mixed systems compared to the pure materials. For both systems, the fatty acid chain disordering temperatures are significantly increased from those of the pure acids. The observed behaviors of these phytosphingosine ceramide systems are fundamentally different from the previously reported analogous sphingosine ceramide systems. The implications of these observations for lipid organization in the stratum corneum are briefly discussed. 相似文献
57.
Large stretching and un-stretching force response of adherent fibroblasts is measured by micromachined mechanical force sensors. The force sensors are composed of a probe and flexible beams. The probe, functionalized by fibronectin, is used to contact the cells. The flexible beams are the sensing element. The sensors are made of single crystal silicon and fabricated by the SCREAM process. The maximum cell stretch reached is approximately 50 microm, which is about twice of the cell initial size, and the time delay between two consecutive stretching/un-stretching steps is 75 s unless otherwise stated. We find that the force response of the cells is strongly linear, reversible, and repeatable, with a small stiffening at the initial deformation stage. Force response of single cells measured before and after cytochalasin D treatment suggests that actin filaments take almost all the cell internal forces due to stretch. These findings may shed light on the increasing understanding on the mechanical behavior of cells and provide clues for making new classes of biological materials having uncommon properties. 相似文献
58.
The influence of sugars in pre-cultivation media suspended plant cells on the kinetics of the sugar uptake and the ethanol
production was studied by mid-infrared spectroscopy using a Fourier transform infrared spectrometer (FT-IR) equipped with
an attenuate total reflection accessory (ATR). We performed the plant cell cultivation with Nicotiana tabacum cv. Bright Yellow No.2 (TBY-2) cells and Oryza sativa L., Japonica, cv. Nipponbare (rice) cells, respectively, in pre-culture and culture media, which had various types of glucose,
fructose, sucrose or glucose–fructose mixtures. The results confirmed the kinetic differences between the TBY-2 cells and
rice cells. These results suggested that the TBY-2 cells consumed sugar before growth and the rice cells consumed sugar after
growth, moreover, the ethanol content increased just after cell growth was activated based on the non-dimensional cultivation
time for the cell growth behavior. 相似文献
59.
Kalliri E Grzyska PK Hausinger RP 《Biochemical and biophysical research communications》2005,338(1):191-197
Co(II), Ni(II), and N-oxalylglycine (NOG) are well-known inhibitors of Fe(II)/alpha-ketoglutarate (alphaKG)-dependent hydroxylases, but few studies describe their kinetics and no spectroscopic investigations have been reported. Using taurine/alphaKG dioxygenase (TauD) as a paradigm for this enzyme family, time-dependent inhibition assays showed that Co(II) and Ni(II) follow slow-binding inhibition kinetics. Whereas Ni(II)-substituted TauD was non-chromophoric, spectroscopic studies of the Co(II)-substituted enzyme revealed a six-coordinate site (protein alone or with alphaKG) that became five-coordinate upon taurine addition. The Co(II) spectrum was not perturbed by a series of anions or oxidants, suggesting the Co(II) is inaccessible and could be used to stabilize the protein. NOG competed weakly (Ki approximately 290 microM) with alphaKG for binding to TauD, with the increased electron density of NOG yielding electronic transitions for NOG-Fe(II)-TauD and taurine-NOG-Fe(II)-TauD at 380 nm (epsilon380 90-105 M(-1) cm(-1)). The spectra of the NOG-bound TauD species did not change significantly upon oxygen exposure, arguing against the formation of an oxygen-bound state mimicking an early intermediate in catalysis. 相似文献
60.
Resting insects are extremely tolerant of hypoxia. However, oxygen requirements increase dramatically during flight. Does the critical atmospheric P (O)(2) (P(c)) increase strongly during flight, or does increased tracheal conductance allow even flying insects to possess large safety margins for oxygen delivery? We tested the effect of P(O)(2) on resting and flying CO(2) emission, as well as on flight behavior and vertical force production in flying locusts, Schistocerca americana. The P(c) for CO(2) emission of resting animals was less than 1 kPa, similar to prior studies. The P(c) for flight bout duration was between 10 and 21 kPa, the P(c) for vertical force production was between 3 and 5 kPa, and the P(c) for CO(2) emission was between 10 and 21 kPa. Our study suggests that the P(c) for steady-state oxygen consumption is between 10 and 21 kPa (much higher than for resting animals), and that tracheal oxygen stores allowed brief flights in 5 and 10 kPa P(O)(2) atmospheres to occur. Thus, P(c) values strongly increased during flight, consistent with the hypothesis that the excess oxygen delivery capacity observed in resting insects is substantially reduced during flight. 相似文献