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1.
Cryolesions were produced by contact cryoprobes on male Wistar rat livers. The development of freezing damage was followed in vivo for 24 hr by morphological examinations, proton spin lattice relaxation times T1, and paramagnetic center concentration measurements. Significant proton T1 increase, related to an increased tissue water content, as well as a concentration decrease of the paramagnetic centers, was observed for the cryolesion, as compared to the undamaged liver tissue of the same animal. The concentration decrease was observed for the g = 2.00 free radicals and g = 1.94 reduced state iron protein centers, specified by the parameter g indicating the position of their absorption lines in the electron paramagnetic resonance spectrum.It was also found that the rate of damage development following a single freezethaw cycle depends significantly on the cooling capacity of the cryoprobe. The final changes produced by 6- and 4-mm-diameter liquid nitrogen-cooled cryotips are comparable, but the development of damage was different. 相似文献
2.
Background
Image contrast in clinical MRI is often determined by differences in tissue water proton relaxation behavior. However, many aspects of water proton relaxation in complex biological media, such as protein solutions and tissue are not well understood, perhaps due to the limited empirical data.Principal Findings
Water proton T1, T2, and T1ρ of protein solutions and tissue were measured systematically under multiple conditions. Crosslinking or aggregation of protein decreased T2 and T1ρ, but did not change high-field T1. T1ρ dispersion profiles were similar for crosslinked protein solutions, myocardial tissue, and cartilage, and exhibited power law behavior with T1ρ(0) values that closely approximated T2. The T1ρ dispersion of mobile protein solutions was flat above 5 kHz, but showed a steep curve below 5 kHz that was sensitive to changes in pH. The T1ρ dispersion of crosslinked BSA and cartilage in DMSO solvent closely resembled that of water solvent above 5 kHz but showed decreased dispersion below 5 kHz.Conclusions
Proton exchange is a minor pathway for tissue T1 and T1ρ relaxation above 5 kHz. Potential models for relaxation are discussed, however the same molecular mechanism appears to be responsible across 5 decades of frequencies from T1ρ to T1. 相似文献3.
G.Larry Cottam Michael R. Waterman B.Cecil Thompson 《Archives of biochemistry and biophysics》1977,181(1):61-65
Transverse water proton relaxation times (T2) have been measured as a function of time after deoxygenation of solutions containing hemoglobin S. The shortened T2 values observed upon deoxygenation of hemoglobin S result from an increase in the correlation time (τc) of the water fraction irrotationally bound to deoxyhemoglobin S as it polymerizes. Therefore, the change in τc as a function of time after deoxygenation can be used to measure the rate of polymer formation. The change in τc observed is reasonably fit by the first-order equation τ = τ0 (1 ? e?kt) + τoxy. At a total hemoglobin concentration of approximately 300 mg/ml, the pseudo-first-order rate constant in a heterozygous AS sample is 25 times slower than in a homozygous S sample, k = 0.019 and 0.47 s?1, respectively. Since the transit time for an erythrocyte in vivo is approximately 15 s, these results suggest that the heterozygous A/S erythrocyte would traverse the circulation and become reoxygenated before extensive polymerization and, therefore, cell sickling could occur. For the homozygous S/S erythrocyte, there is ample time for polymerization and for cell sickling during circulation. 相似文献
4.
B.M. Fung Dana L. Durham David A. Wassil 《Biochimica et Biophysica Acta (BBA)/General Subjects》1975,399(1):191-202
Careful experiments on the measurement of the intensity of the deuterium NMR signal for 2H2O in muscle and in its distillate were performed, and they showed that all 2H2O in muscles is “NMR visible.”The spin-lattice relaxation time (T1) of the water protons in the muscle and liver of mice and in egg white has been studied at six frequencies ranging from 4.5 to 6.0 MHz over the temperature range of +37 to −70°C. T1 values of deuterons in 2H2O of gastrocnemius muscle and liver of mice have been measured at three frequencies (4.5, 9.21 and 15.35 MHz) over the temperature range of +37 to −20°C. Calculations on T1 for both proton and deuteron have been made and compared with the experimental data. It is suggested that the reduction of the T1 values compared to pure water and the frequency dependence of T1 are due to water molecules in the hydration layer of the macromolecules, and that the bulk of water molecules in the biological tissues and egg white undergoes relaxation like ordinary liquid water. 相似文献
5.
B.M. Fung 《Biochimica et Biophysica Acta (BBA)/General Subjects》1977,497(1):317-322
Proton T1 of water in muscle and brain tissues was studied as a function of water content at 25°C and 5, 30, and 100 MHz. Muscle samples were bathed in modified Krebs solutions that have the same ionic strength but different osmolarity in order to change the water content. At all three frequencies their 1/T1 extrapolated to the same value of 0.6 s?1 for zero dry weight, indicating that T1 for the majority of water molecules in normal muscle and brain is frequency-independent. Dehydrated muscle, homogenized brain tissue suspended in modified Krebs solution and dehydrated brain tissue provide samples with wide ranges of water content. Their T1 values at all three frequencies can be well accounted for by a simple equation derived from the two-state model. 相似文献
6.
Kaoru Niki Hideo Namiki Sakae Kikuyama Katsutoshi Yoshizato 《Developmental biology》1982,94(1):116-120
In this paper we report on the requirement of the epidermal tissue for thyroid hormone-induced tadpole tail regression. The epidermis was removed by two different methods, i.e., surgically or chemically. Chemical removal included EDTA and trypsin treatment. Epidermis-free tail fin blocks were cultured in vitro according to A. Derby, 1968, J. Exp. Zool.168, 147–156. and the effect of 3,3′,5-tri-iodo-l-thyronine (T3) was followed up for 4 days. No tissue breakdown was observed at the concentration of 10?8M T3, which was enough to induce tissue resorption of the epidermis-containing normal tissue blocks. Tail muscle cubes with epidermis regressed in the T3-containing culture medium. However, the epidermis-deprived tail muscle cubes did not respond to the hormone. The tail fin mesenchymal connective tissue block deprived of the epidermis was cultured with epidermal tissues which had been removed surgically from the tail. The presence of T3 in this reconstituted culture induced the regression of the mesenchymal connective tissue blocks. These experiments clearly show that epidermal tissue plays a critical role in T3-induced tissue degradation. 相似文献
7.
The proton and deuterium longitudinal relaxation rates were Studied at room temperature up to the highest protein concentrations in oxyhaemoglobin solutions of different H2O/D2O composition. The deuterium relaxation rates followed the experimentally well known single linear dependence on protein concentration, the slopes being little influenced by solvent (D2O/H2O) composition. The proton ralaxation rates show two different liner dependences on haemoglobin concentration. The entire concentration range is described by two straight lines with the threshold concentration about 11 mM (in haem), The ratio of the slopes is 1.6 (high-to-low Hb-conc.). Only in the higher concentration range two T1's were observed if the solvent contained more than half of D2O. The slow relaxation phase of protons has T1's similar to those measured in solutions with less than half of D2O. The relaxation of the other phase was ten times faster. The ratio of the proton populations in these two phases was equal to 2 (slow-to-fast) and independent of protein concentration. The fast relaxing protons are attributed to water molecules encaged within two or more haemoglobin molecules which associate for times long enough on the PMR time-scale. 相似文献
8.
A Gram-negative, polar flagella, rod-shaped bacterium LV T was isolated from a soil sample subjected to long-term manganese pollution in Hunan Province, China. Cells grow optimally on Luria–Bertani agar medium at 30 °C in the presence of 0–5.0 % (w/v) NaCl and pH 7–8. 16S rRNA gene sequence analysis revealed that strain LV T belonged to the genus Pseudomonas, with sequence similarity values of 98.6, 98.2, 98.7, and 97.3 % to Pseudomonas monteilii BCRC 17520 T , Pseudomonas putida BCRC 10459 T , Pseudomonas plecoglossicida BCRC 17517 T , and Pseudomonas asplenii BCRC 17131 T , respectively. The level of DNA–DNA relatedness between the five strains was <30 %. The DNA G+C content of strain LV T is 68.8 mol%. Chemotaxonomic data revealed that the strain LVT possesses ubiquinone Q-9. The polar lipid profile of strain LV T contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylcholine, and phosphatidylethanolamine. The major cellular fatty acids present are C10:03-OH (12.33 %), C16:0 (23.99 %), summed feature 3(C16:1ω7c and/or C16:1ω6c), and summed feature 8(C18:1 ω7c and C18:1 ω6c). Based on the genotypic, chemotaxonomic and phenotypic data, strain LV T is distinguishable from related members of the genus Pseudomonas. Thus, strain LV T represents a novel species of the genus Pseudomonas, for which the name Pseudomonas hunanensis sp. nov. is proposed. The type strain is LV T (=CICC 10558T = NCCB 100446T). 相似文献
9.
Adam Zipp Irwin D. Kuntz Thomas L. James 《Archives of biochemistry and biophysics》1977,178(2):435-441
The dependence of the water proton magnetic resonance spin-lattice relaxation rate (T1??1) in the rotating frame on the strength of the spin-locking (H1) field has been investigated for packed oxy and deoxy normal and sickle erythrocytes at temperatures from 9 to 40 °C. The T1??1 of oxy or deoxy normal erythrocytes shows no dependence on H1 up to ~7 G at any temperature studied. On the other hand, T1??1 decreases from about 40 s?1 to 15 s?1 (H1 from 0 to ~7 G) for deoxygenated packed sickle cells at 40 °C. The magnitude of this variation of T1??1 with H1 decreases with decreasing temperature. Oxy packed sickle cells also show a dependence of T1??1 on H1 but the magnitude is <10% of that of the deoxygenated samples. These results suggest that water proton T1??1 measurements are a sensitive probe of hemoglobin S polymerization and provide a novel technique for the study of slow water motions in these systems. The T1??1 results are compared with low frequency T1?1 results of other investigators on hemoglobin S solutions. Analysis of the data suggests that water proton motions with correlation times of the order of 10?5 s are present in the deoxygenated sickle cell samples at temperatures above 10 °C. 相似文献
10.
The binding of Mn2+ to the anthranilate synthetase-phosphoribosyltransferase enzyme complex from Salmonella typhimurium was examined by electron paramagnetic resonance studies. Two types of binding sites were observed: one to two tight sites with a dissociation constant of 3–5 μm and five to six weaker sites with a dissociation constant of 40–70 μm. The activator constant for Mn2+ was found to be 9 μm for the glutamine-linked anthranilate synthetase activity and 4 μm for the phosphoribosyltransferase activity. These values are both in the range of the dissociation constant for the tight sites. Water proton relaxation rate measurements showed that the binary enhancement values for both classes of sites were equivalent, ?b = 10.7 ± 2.0. The addition of chorismate to the Mn2+-enzyme complexes when predominantly the tight Mn2+ sites were occupied resulted in a large decrease in the observed enhancement (?T = 2.0). Addition of 5-phosphoribosyl-1-pyrophosphate to the enzyme-Mn2+ complexes caused large decreases in the water proton relaxation rate (?T = 1.5) when tight or tight plus weaker Mn2+ sites were occupied. No changes in the water proton relaxation rate were observed when glutamine, pyruvate, or anthranilate were added; a small decrease was observed when enzyme-Mn2+ was titrated with tryptophan. Tryptophan significantly altered the effect of the binding of chorismate but not of 5-phosphoribosyl-1-pyrophosphate. The effect of tryptophan on the water proton relaxation rate of a Mn2+-enzyme-chorismate complex using a variant enzyme complex which is tryptophan hypersensitive (P. D. Robison, and H. R. Levy, 1976, Biochim. Biophys. Acta. 445, 475–485) occurred at lower concentrations than for the normal enzyme complex. The uncomplexed anthranilate synthetase subunit was titrated with Mn2+ and found to have one to two binding sites with a dissociation constant of 300 ± 100 μm. This dissociation constant is much larger than the activator constant for Mn2+ for uncomplexed anthranilate synthetase which was determined to be 4 μm. These results indicate that the Mn2+-binding sites on anthranilate synthetase are altered when the enzyme complex is formed and that both chorismate and 5-phosphoribosyl-1-pyrophosphate interact closely with enzyme-bound Mn2+ or cause a large effect upon its environment. 相似文献
11.
E Valensin M L Bianchi Bandinelli M L Di Cairano G Valensin E Gaggelli E Tiezzi 《Biophysical chemistry》1981,14(4):357-362
The water proton spin-lattice relaxation rate (1/T1) was measured in suspensions of erythrocytes adsorbed with the hemagglutinating Echovirus type 11. The observed 1/T1 enhancement, which was displaying a linear dependence on the virus concentration, was taken as a proof that the adsorption phase of the virus-cell interaction accounts, at least partially, for the previously observed phenomena in virus-infected HEp-2 cells. By injecting the Echovirus type 11 into suspensions of erythrocytes doped with Mn2+ or treated with concanavalin A, cylochalasin D and colchicinc. it was suggested that the observed 1/T1 enhancement could be related to modifications of the permeability properties of the red cell membrane, as well as to movements of the cell surface receptors. 相似文献
12.
Solvent1H T?11 values at magnetic fields between 2.3 × 10?4 and 1.2 T were measured for ethyleneglycol solutions of manganese(II), cobalt(II), nickel(II), copper(II), and gadolinium(III) salts in the temperature range ?10–+40 °C. The T?11 profiles were interpreted on the ground of the available theories according to whether the electronic relaxation times or the rotational times are the correlation times for the interaction. The comparison among systems experiencing different correlation times and electronic structures (metal ions in water, ethyleneglycol, and in proteins) allowed us to test the general theoretical approach regarding nuclear relaxation times in paramagnetic systems. Such theoretical approaches allow researchers to extract structural parameters and information on the correlation times and dynamic processes operative in the various investigated systems. 相似文献
13.
Florence Colliez Marta M. Safronova Julie Magat Nicolas Joudiou André P. Peeters Bénédicte F. Jordan Bernard Gallez Thierry Duprez 《PloS one》2015,10(8)
The clinical applicability of brain oxygenation mapping using the MOBILE (Mapping of Oxygen By Imaging Lipids relaxation Enhancement) magnetic resonance (MR) technique was assessed in the clinical setting of normal brain and of acute cerebral ischemia as a founding proof-of-concept translational study. Changes in the oxygenation level within healthy brain tissue can be detected by analyzing the spin-lattice proton relaxation (‘Global T
1
’ combining water and lipid protons) because of the paramagnetic properties of molecular oxygen. It was hypothesized that selective measurement of the relaxation of the lipid protons (‘Lipids T
1
’) would result in enhanced sensitivity of pO2 mapping because of higher solubility of oxygen in lipids than in water, and this was demonstrated in pre-clinical models using the MOBILE technique. In the present study, 12 healthy volunteers and eight patients with acute (48–72 hours) brain infarction were examined with the same clinical 3T MR system. Both Lipids R1 (R1 = 1/T1) and Global R1 were significantly different in the infarcted area and the contralateral unaffected brain tissue, with a higher statistical significance for Lipids R1 (median difference: 0.408 s-1; p<0.0001) than for Global R1 (median difference: 0.154 s-1; p = 0.027). Both Lipids R1 and Global R1 values in the unaffected contralateral brain tissue of stroke patients were not significantly different from the R1 values calculated in the brain tissue of healthy volunteers. The main limitations of the present prototypic version of the MOBILE sequence are the long acquisition time (4 min), hampering robustness of data in uncooperative patients, and a 2 mm slice thickness precluding accurate measurements in small infarcts because of partial volume averaging effects. 相似文献
14.
F E Evans 《Archives of biochemistry and biophysics》1979,193(1):63-75
The 40-MHz 31P nuclear magnetic resonance (nmr) spectrum of intact HeLa cells contains seven broad peaks with some detectable splittings. The linewidths were significantly broader than for those of cell-free systems such as cell extracts, indicating that the cellular environment is responsible for the unusual line broadening. Resolution of these peaks at 40 MHz is sufficient to make certain assignments and the relaxation parameters of some of the intracellular metabolites have been measured. The spin-lattice relaxation times (T1) ranged from 0.3 s for adenosine triphosphate (ATP) to about 3 s for inorganic phosphate (Pi) and monophosphate compounds. Nuclear Overhauser enhancements (NOE) were induced by proton irradiation with the possible exception of ATP. The relaxation parameters were compared to those of cell-free compounds and in all cases T1 and NOE were smaller for the intracellular metabolites. The relaxation parameters for ATP were affected the most. This behavior was mimicked with mixtures of cell-free metabolites containing paramagnetic ions. The larger change in both T1 and NOE of intracellular ATP could be accounted for by selective binding of paramagnetic ions. This phenomenon also explains some of the line broadening in the cell spectrum especially that of ATP. The spin-spin relaxation times (T2) of P1 and monophosphate compounds as measured by a pulse technique did not account for the observed linewidths. This is due to the presence of chemical shift envelopes arising from pH heterogeneity. All resonances were broader at 146 MHz because of the line broadening by paramagnetic ions and the presence of chemical shift envelopes. Other mechanisms of line broadening may also be significant. There was little difference in resolution of spectra at 40 and 146 MHz. Water proton linewidths and T2 values were measured for HeLa cells and for some minced tissue preparations. The water linewidth in tissue samples was broader than that in the cell suspension. The large linewidths in tissues arise mainly from chemical shift envelopes caused by magnetic field nonuniformity in the tissue samples. There appears to be a small chemical shift envelope from magnetic nonuniformity in HeLa cells as well. The 1H results on envelopes were extrapolated to 31P studies on cells and tissues. Possible methods for reducing linewidths arising from the various proposed broadening mechanisms were discussed. 相似文献
15.
A model mineralizing system was subjected to magnetic resonance microscopy to investigate how water proton transverse (T2) relaxation times and magnetization transfer ratios can be applied to monitor collagen mineralization. In our model system, a collagen sponge was mineralized with polymer-stabilized amorphous calcium carbonate. The lower hydration and water proton T2 values of collagen sponges during the initial mineralization phase were attributed to the replacement of the water within the collagen fibrils by amorphous calcium carbonate. The significant reduction in T2 values by day 6 (p < 0.001) was attributed to the appearance of mineral crystallites, which were also detected by x-ray diffraction and scanning electron microscopy. In the second phase, between days 6 and 13, magnetic resonance microscopy properties appear to plateau as amorphous calcium carbonate droplets began to coalesce within the intrafibrillar space of collagen. In the third phase, after day 15, the amorphous mineral phase crystallized, resulting in a reduction in the absolute intensity of the collagen diffraction pattern. We speculate that magnetization transfer ratio values for collagen sponges, with similar collagen contents, increased from 0.25 ± 0.02 for control strips to a maximum value of 0.31 ± 0.04 at day 15 (p = 0.03) because mineral crystals greatly reduce the mobility of the collagen fibrils. 相似文献
16.
The adenosylcobalamin- (coenzyme B12) dependent ethanolamine ammonia-lyase (EAL) plays a key role in aminoethanol metabolism, associated with microbiome homeostasis and Salmonella- and Escherichia coli-induced disease conditions in the human gut. To gain molecular insight into these processes toward development of potential therapeutic targets, reactions of the cryotrapped (S)-2-aminopropanol substrate radical EAL from Salmonella typhimurium are addressed over a temperature (T) range of 220–250 K by using T-step reaction initiation and time-resolved, full-spectrum electron paramagnetic resonance spectroscopy. The observed substrate radical reaction kinetics are characterized by two pairs of biexponential processes: native decay to diamagnetic products and growth of a non-native radical species and Co(II) in cobalamin. The multicomponent low-T kinetics are simulated by using a minimal model, in which the substrate-radical macrostate, S?, is partitioned by a free-energy barrier into two sequential microstates: 1) S1?, a relatively high-entropy/high-enthalpy microstate with a protein configuration that captures the nascent substrate radical in the terminal step of radical-pair separation; and 2) S2?, a relatively low-enthalpy/low-entropy microstate with a protein configuration that enables the rearrangement reaction. The non-native, destructive reaction of S1? at T ≤ 250 K is caused by a prolonged lifetime in the substrate-radical capture state. Monotonic S? decay over 278–300 K indicates that the free-energy barrier to S1? and S2? interconversion is latent at physiological T-values. Overall, the low-temperature studies reveal two protein-configuration microstates and connecting protein-configurational transitions that specialize the S? macrostate for the dual functional roles of radical capture and rearrangement enabling. The identification of new, to our knowledge, intermediate states and specific protein-fluctuation contributions to the reaction coordinate represent an advance toward development of novel therapeutic targets in EAL. 相似文献
17.
Probing water compartments and membrane permeability in plant cells by 1H NMR relaxation measurements
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1H NMR relaxation times (T1 and T2) in parenchyma tissue of apple can identify three populations of water with different relaxation characteristics. By following the uptake of Mn2+ ions in the tissue it is shown that the observed relaxation times originate from particular water compartments: the vacuole, the cytoplasm, and the cell wall/extracellular space.
Proton exchange between these compartments is controlled by the plasmalemma and tonoplast membranes. During the Mn2+ penetration experiment, conditions occur that cause the relaxation times of protons of cytoplasmic water to be much shorter than their residence time in the cytoplasm. Then the tonoplast permeability coefficient Pd for water can be calculated from the vacuolar T1 and T2 values to be 2.44 10-5 m·s-1.
相似文献18.
Wei-Wei Wang Shao-Hua Xu Ya-Zheng Zhao Chao Zhang Yuan-Yuan Zhang Bo-Yang Yu Jian Zhang 《Bioorganic & medicinal chemistry letters》2017,27(4):1026-1030
To discover new inhibitors on tissue factor procoagulant activity, 20 pentacyclic triterpenes were semi-synthetized through microbial transformation and assayed on the model of human THP-1 cells stimulated by lipopolysaccharide. In the biotransformation two types of reactions were observed, regio-selective hydroxylation and glycosylation. The bioassay results showed that most of tested compounds were significant effective on this model and two of the biotransformation products 23-hydroxy-28-O-β-d-glucopyranosyl betulinic acid (3d) and 28-O-β-d-glucopyranosyl oleanic acid (1a) exhibited most potential activities with the IC50 values of 0.028, 0.035 nM respectively. The preliminary structure and activity relationship analysis revealed that the aglycones with single free hydroxyl group on the skeleton (1, 1j) were less effective than that with more free hydroxyl groups (1d, 1f, 2), mono-glycosylation can significantly enhance their inhibitory effects. Our findings also provide some potential leading compounds for tissue factor-related diseases, such as cancer and cardiovascular diseases. 相似文献
19.
Characterization of heat injury in grapes using h nuclear magnetic resonance methods : changes in transverse relaxation times
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Transverse relaxation times (T2) of tissue water (1H) in leaves and suspension cultured cells of grape hybrids (Vitis spp. cv `Venus' and `Veeblanc') were measured by nuclear magnetic resonance at various temperatures. The tissue water was characterized by two T2 time constants. A sharp decrease in T2 for the major fraction of tissue water was observed in association with heat injury, as measured by electrolyte leakage and triphenyltetrazolium chloride reduction in both leaves and suspension cultured cells. The changes in T2 as a result of heat injury were irreversible, as indicated by a temperature dependent hysteresis of T2. Studies using a paramagnetic probe (Mn+2) indicated that the plasma membrane was irreversibly damaged at the killing temperature, resulting in a loss of cell compartmentalization. Tissue water in heat-killed samples was characterized by only a single T2. 相似文献
20.
Multi-proton spin-echo images were collected from cold-acclimated winter wheat crowns (Triticum aestivum L.) cv. Cappelle Desprez at 400 MHz between 4 and ?4 °C. Water proton relaxation by the spin-spin (T2) mechanism from individual voxels in image slices was found to be mono-exponential. The temperature dependence of these relaxation rates was found to obey Arrhenius or absolute rate theory expressions relating temperature, activation energies and relaxation rates, Images whose contrast is proportional to the Arrhenius activation energy (Ea), Gibb's free energy of activation (ΔG?), and the entropy of activation (ΔS?) for water relaxation on a voxel basis were constructed by post-image processing. These new images exhibit contrast based on activation energies rather than rules of proton relaxation. The temperature dependence of water proton T2 relaxation rates permits prediction of changes in the physical state of water in this tissue over modest temperature ranges. A simple model is proposed to predict the freezing temperature kof various tissue in wheat crowns. The average Ea and ΔH? for water proton T2 relaxation over the above temperature range in winter wheat tissue were ?6.4 ± 14.8 and ?8.6 ± 14.8kj mol?1, respectively. This barrier is considerably lower than the Ea for proton translation in ice at 0°C, which is reported to be between 46.0 and 56.5 kj mol?1 相似文献