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Published: 1 June 2024

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1

Wolff, Steven D., and Robert S. Balaban. "NMR imaging of labile proton exchange." Journal of Magnetic Resonance (1969) 86, no. 1 (January 1990): 164–69. http://dx.doi.org/10.1016/0022-2364(90)90220-4.

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2

Novakovic, Mihajlo, Ricardo P. Martinho, Gregory L. Olsen, Michael S. Lustig, and Lucio Frydman. "Sensitivity-enhanced detection of non-labile proton and carbon NMR spectra on water resonances." Physical Chemistry Chemical Physics 20, no. 1 (2018): 56–62. http://dx.doi.org/10.1039/c7cp07046b.

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3

Pattison, S. E., and R. J. Cousins. "Kinetics of zinc uptake and exchange by primary cultures of rat hepatocytes." American Journal of Physiology-Endocrinology and Metabolism 250, no. 6 (June 1, 1986): E677—E685. http://dx.doi.org/10.1152/ajpendo.1986.250.6.e677.

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The kinetics of 65Zn2+ uptake and exchange by hepatocytes in primary culture have been examined in detail to provide a basis for analyzing hormonal regulation of hepatic zinc metabolism. 65Zn2+ uptake was found to be a biphasic process. The slow phase represents an exchange between Zn2+ in the medium and preexisting, intracellular zinc pools. This exchange rate was saturable with a medium zinc concentration of 9.5 microM eliciting one-half the maximum exchange rate and a maximum exchange rate of 9.9 pmol Zn2+ . min-1 . mg protein-1 in the presence of bovine serum albumin. In the absence of albumin, a secondary, nonsaturable uptake rate was observed. The slow phase was relatively selective, and of the divalent transition metal ions tested, only Cd2+ and Mn2+ caused inhibition. The rate of exchange suggests total hepatocyte zinc has a turnover rate of approximately 30 h. The fast phase of 65Zn2+ reflects net Zn2+ accumulation into a labile pool. The initial rates for this process were too fast to be measured accurately, but steady-state measurements allowed determination of the labile pool size. The pool dimensions saturated in the presence [Kapp = 28.6 microM; pool capacity = 0.44 nmol Zn2+/mg protein] and absence [Kapp = 11.8 microM; pool capacity = 0.34 nmol Zn2+/mg protein] of bovine serum albumin. Kinetics and equilibria of Zn2+ uptake into the labile pool suggest that the latter acts as a source of Zn2+ for the slow-exchange phase. Dexamethasone stimulated slow Zn2+ exchange and also increased the labile pool size. The data suggest physiological factors alter hepatic zinc metabolism by influencing both intracellular Zn2+ pools.
4

Mullins, R. E., and G. E. Austin. "Sensitivity of isoelectric focusing, ion exchange, and affinity chromatography to labile glycated hemoglobin." Clinical Chemistry 32, no. 8 (August 1, 1986): 1460–63. http://dx.doi.org/10.1093/clinchem/32.8.1460.

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Abstract We examined the effect of labile glycated hemoglobin on measurements of glycated hemoglobin by several commercial procedures. Erythrocytes from diabetic and nondiabetic patients were incubated in vitro with various concentrations of glucose, to generate labile glycated hemoglobin, and the species of glycated and nonglycated hemoglobin in each sample were identified by isoelectric focusing. Glycated hemoglobin was then assayed by the Bio-Rad A1 column method (I), the Bio-Rad A1c column method (II), and the Pierce affinity column method (III). I was sensitive to the labile (aldimine) fraction of glycated hemoglobin, and percentages of glycated hemoglobin so determined represented the sum of the labile fraction plus hemoglobin A1c and other stable glycated species. This spurious increase in glycated hemoglobin concentration by the aldimine could be obviated by any of three wash procedures, which eliminated the labile fraction from the samples: incubating the erythrocytes (a) in phosphate-buffered saline (pH 7.4) for 18 h at 22 degrees C, (b) in 100 mmol/L citrate (pH 5.0) for 30 min at 37 degrees C, or (c) in saline containing, per liter, 30 mmol of semicarbazide and 12 mmol of aniline hydrochloride (pH 5.0) for 30 min at 37 degrees C. Methods II and III did not detect the labile fraction. However, treatments a-c decreased the concentrations of stable glycated hemoglobin as determined by all three column-chromatographic methods as compared with unwashed sample. By isoelectric focusing we determined that blood with high glucose content had concentrations of aldimine roughly proportional to the blood glucose concentration. The kinetics of formation of labile glycated hemoglobin in these cells were consistent with the reported rate constants determined by using purified hemoglobin preparations in vitro.
5

Gabka, Grzegorz, Piotr Bujak, Kamila Giedyk, Kamil Kotwica, Andrzej Ostrowski, Karolina Malinowska, Wojciech Lisowski, Janusz W. Sobczak, and Adam Pron. "Ligand exchange in quaternary alloyed nanocrystals – a spectroscopic study." Phys. Chem. Chem. Phys. 16, no. 42 (2014): 23082–88. http://dx.doi.org/10.1039/c4cp03850a.

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Detailed NMR and XPS studies of the exchange of initial ligands for pyridine in quaternary nanocrystals enabled us to demonstrate, for the first time, direct binding of this labile ligand to the nanocrystal surface.
6

Foster, Jonathan A., Sebastian Henke, Andreas Schneemann, Roland A. Fischer, and Anthony K. Cheetham. "Liquid exfoliation of alkyl-ether functionalised layered metal–organic frameworks to nanosheets." Chemical Communications 52, no. 69 (2016): 10474–77. http://dx.doi.org/10.1039/c6cc05154e.

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7

Yee, A. M., J. P. Buyon, and Y. K. Yip. "Interferon alpha associated with systemic lupus erythematosus is not intrinsically acid labile." Journal of Experimental Medicine 169, no. 3 (March 1, 1989): 987–93. http://dx.doi.org/10.1084/jem.169.3.987.

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The physicochemical properties of apparently acid-labile IFN-alpha from patients with SLE have been studied. The antigenicity, apparent molecular size, and isoelectric point of SLE IFN-alpha are indistinguishable from those of conventional, previously characterized, acid-stable subspecies of IFN-alpha. However, after partial purification by anion-exchange chromatography, SLE IFN-alpha no longer exhibits acid lability, suggesting that other plasma factor(s) are responsible for the acid lability of SLE IFN-alpha. Addition of SLE plasma, but not normal plasma, to conventional acid-stable IFN-alpha renders the exogenous IFN-alpha acid labile. Preliminary results demonstrate that an acid-dependent IFN-inactivating activity can be partially purified from SLE plasma by anion-exchange chromatography.
8

Braos, Lucas Boscov, Mara Cristina Pessôa da Cruz, Manoel Evaristo Ferreira, and Fernando Kuhnen. "ORGANIC PHOSPHORUS FRACTIONS IN SOIL FERTILIZED WITH CATTLE MANURE." Revista Brasileira de Ciência do Solo 39, no. 1 (February 2015): 140–50. http://dx.doi.org/10.1590/01000683rbcs20150137.

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Inorganic phosphorus (Pi) usually controls the P availability in tropical soils, but the contribution of organic P (Po) should not be neglected, mainly in systems with low P input or management systems that promote organic matter accumulation. The aims of this study were to evaluate the changes in the Po fractions over time in soil fertilized and not fertilized with cattle manure and to correlate Po forms with available P extracted by anion exchange resin. The experiment was carried out under field conditions, in a sandy-clay loam Haplustox. The experimental design was a 2 × 9 randomized complete block factorial design, in which the first factor was manure application (20 t ha-1) or absence, and the second the soil sampling times (3, 7, 14, 21, 28, 49, 70, 91, and 112 days) after manure incorporation. Labile, moderately labile and non-labile Po fractions were determined in the soil material of each sampling. Manure fertilization increased the Po levels in the moderately labile and non-labile fractions and the total organic P, but did not affect the Po fraction proportions in relation to total organic P. On average, 5.1 % of total Po was in the labile, 44.4 % in the moderately labile and 50.5 % in the non-labile fractions. Available P (resin P) was more affected by the manure soluble Pi rather than by the labile Po forms. The labile and non-labile Po fractions varied randomly with no defined trend in relation to the samplings; for this reason, the data did not fit any mathematical model.
9

Clark, Andrew, and Nikolaos Kontoudakis. "Increasing the Efficiency and Accuracy of Labile Cu Measurement in Wine with Screen-Printed Electrodes." Chemosensors 6, no. 3 (August 17, 2018): 35. http://dx.doi.org/10.3390/chemosensors6030035.

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Development of oxidative and reductive flavors in wine can be influenced by the concentration and form of Cu within the wine. Electrochemical techniques have been devised to quantitate electrochemically active Cu (labile) in wine, as opposed to inactive Cu (non-labile). However, the electrochemical methods to measure labile Cu may be biased by the wine matrix, require lengthy calibration processes and/or unduly perturb the wine matrix during measurement. In this study, medium exchange stripping potentiometry was utilized with a thin mercury film on a screen-printed carbon electrode to provide a quantitation method that could largely overcome these limitations. The best average recoveries for 0.040 mg/L of labile Cu of 101 ± 15% (n = 12) were observed using composite calibration graphs prepared in oxidized wines and on multiple electrodes and using Pb as an internal standard. Composite calibration curves performed on different electrodes to the sample analysis were as effective in quantifying labile Cu as calibration curves performed on the same electrode as the sample. The results allow selection of a quantitation procedure that will suit the required speed and accuracy of labile Cu determination.
10

Wang, Yanan, Esko Makkonen, Xi Chen, and Thomas Bürgi. "Absolute configuration retention of a configurationally labile ligand during dynamic processes of thiolate protected gold clusters." Chemical Science 12, no. 27 (2021): 9413–19. http://dx.doi.org/10.1039/d1sc01702k.

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The ligand exchange between a configurationally labile BiDi ligand and intrinsically chiral Au38 gold nanoclusters is diastereoselective. More importantly, the adsorbed ligand retains its configuration during dynamic cluster processes.
11

Pranckevicius, Conor, Marco Weber, Ivo Krummenacher, Ashwini K. Phukan, and Holger Braunschweig. "Phosphinoborylenes as stable sources of fleeting borylenes." Chemical Science 11, no. 40 (2020): 11055–59. http://dx.doi.org/10.1039/d0sc04826g.

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A room-temperature stable phosphinoborylene provides a source of a reactive two-coordinate borylene via dissociation of a labile phosphine upon gentle heating. Ligand exchange, the capture of unsaturated molecules, and oxidation have been explored.
12

McKenzie, R. H., J. W. B. Stewart, J. F. Dormaar, and G. B. Schaalje. "Long-term crop rotation and fertilizer effects on phosphorus transformations: I. In a Chernozemic soil." Canadian Journal of Soil Science 72, no. 4 (November 1, 1992): 569–79. http://dx.doi.org/10.4141/cjss92-047.

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The objective of this study was to determine effects of different cropping systems and nitrogen (N) and phosphorus (P) fertilizers on soil P fractions and transformations in long-term rotation plots on a Chernozemic soil at Lethbridge, Alberta. Continuous wheat, wheat-wheat-fallow, and wheat-fallow crop rotations and fertilizer application significantly affected the amount and distribution of phosphorus among labile and stable inorganic (Pi) and organic (Po) forms as determined by a sequential fractionation procedure. Without N and P fertilizer, the proportion of total soil P in more labile forms that were sequentially extractable with an anion exchange resin (resin-Pi), sodium bicarbonate (bicarb-Pi and Po) and sodium hydroxide (NaOH-Pi and Po) were reduced to a greater extent in continuous wheat than in wheat-wheat-fallow and wheat-fallow rotations. The addition of P fertilizer significantly increased total P and all Pi fractions, with the greatest change in more labile Pi forms (resin, bicarb and NaOH), but had no effect on labile Po forms. In contrast, N fertilizer addition increased the proportion of P in labile Po fractions in all rotations, and decreased the proportion of P in labile Pi forms. The combination of fertilizer N and P generally increased both Pi and Po labile forms. The continuous wheat rotation, coupled with N and P fertilizer inputs, had the most positive effect on P cycling and transformations. Key words: Soil P transformations, Chernozemic soils, P bioavailability, sequential extraction
13

Zhang, Shuai, Xiuling Zhu, and Cuihong Jin. "Development of a high-performance anion exchange membrane using poly(isatin biphenylene) with flexible heterocyclic quaternary ammonium cations for alkaline fuel cells." Journal of Materials Chemistry A 7, no. 12 (2019): 6883–93. http://dx.doi.org/10.1039/c8ta11291f.

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A series of quaternary ammonium-tethered poly(isatin biphenylene)s (PIBs) were prepared devoid of alkaline labile aryl ether bonds via superacid-catalyzed polymerization and explored as highly alkaline stable backbones of anion exchange membranes (AEMs).
14

Juranic, Nenad, Zsolt Zolnai, and Slobodan Macura. "Two-dimensional exchange spectroscopy revisited: Accounting for the number of participating spins." Journal of the Serbian Chemical Society 65, no. 5-6 (2000): 285–301. http://dx.doi.org/10.2298/jsc0006285j.

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The magnetization exchange between two groups of equivalent spins each having different populations and overall relaxation rates has been analyzed. The results suggest that either the spin population difference or the overall relaxation rate difference in an exchange spectrum can produce cross-peaks with volumes larger than that of the corresponding diagonal line. This is important for interpretation of the magnetization exchange between water and macromolecular protons where both the population differences and auto-relaxation rate differences can be very large. Theoretical predictions of peak volume evolution were experimentally verified in the intermolecular magnetization exchange between the water and labile amide proton in a model system N-acetylglycine/water.
15

Schmitt, Djalma Eugênio, Jucinei José Comin, Luciano Colpo Gatiboni, Tales Tiecher, Felipe Lorensini, George Wellington Bastos de Melo, Eduardo Girotto, Renato Guardini, Janaína Heinzen, and Gustavo Brunetto. "Phosphorus fractions in sandy soils of vineyards in southern Brazil." Revista Brasileira de Ciência do Solo 37, no. 2 (April 2013): 472–81. http://dx.doi.org/10.1590/s0100-06832013000200018.

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Phosphorus (P) applications to vineyards can cause P accumulation in the soil and maximize pollution risks. This study was carried out to quantify the accumulation of P fractions in sandy soils of vineyards in southern Brazil. Soil samples (layers 0-5, 6-10 and 11-20 cm) were collected from a native grassland area and two vineyards, after 14 years (vineyard 1) and 30 years (vineyard 2) of cultivation, in Santana do Livramento, southern Brazil, and subjected to chemical fractionation of P. Phosphorus application, especially to the 30-year-old vineyard 2, increased the inorganic P content down to a depth of 20 cm, mainly in the labile fractions extracted by anion-exchange resin and NaHCO3, in the moderately labile fraction extracted by 0.1 and 0.5 mol L-1 NaOH, and in the non-labile fraction extracted by 1 mol L-1 HCl, indicating the possibility of water eutrophication. Phosphorus application and grapevine cultivation time increased the P content in the organic fraction extracted by NaHCO3 from the 0-5 cm layer, and especially in the moderately labile fraction extracted by 0.1 mol L-1 NaOH, down to a depth of 20 cm.
16

Stumborg, C., and J. J. Schoenau. "Evaluating phosphorus loading from repeated manure applications to two Saskatchewansoils." Canadian Journal of Soil Science 88, no. 3 (May 2, 2008): 377–87. http://dx.doi.org/10.4141/s06-048.

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An understanding of the impact of repeated manure additions on soil phosphorus (P) is needed to determine appropriate manure application rates for prairie soils and manure sources. The objective of this study was to assess the loading of manure-derived phosphorus using P budgets and soil P measurement techniques applied to two Saskatchewan soils with known histories of manure application. Liquid hog manure (LHM) and solid cattle manure (SCM) treatments were applied annually over 8 yr to Black Chernozemic soils (Dixon site), and LHM was applied to Dark Brown Chernozemic soils (Plenty site) over 6 yr. Soil samples were collected in the spring of 2003 and 2004 and analyzed for labile P (Modified Kelowna extractable, Olsen extractable, water extractable, and Plant Root Simulator exchange resin methods) and total P. The P budgets were in good agreement with the observed patterns in labile soil P at the two sites. The annual application of LHM (37000 L ha-1 yr-1) at agronomic nitrogen (N) rates with no additional P fertilizer (Dixon only) did not significantly elevate soil labile P compared with the unfertilized controls at both Dixon and Plenty. The annual application of SCM (7.6 Mg ha-1 yr-1) at agronomic N rates did not significantly elevate soil labile P compared with the unfertilized control at Dixon; whereas of SCM at higher rates (15.2 Mg ha-1 yr-1 and 30.4 Mg ha-1 yr-1) showed some elevation in labile soil P. Measures of labile P were sensitive to P surpluses or deficits predicted by P balances, and all methods of measuring labile soil P were strongly correlated with one another at both sites (r ≥ 0.803 at P ≤ 0.01). Key words: Manure, cattle manure, nitrogen, phosphorus, soil test phosphorus
17

Juranić, Nenad, Zsolt Zolnai, and Slobodan Macura. "Elucidation of Deceptively Slow Magnetization Exchange between Protein Labile Protons and Water by Dilution-Enhanced Exchange Spectroscopy." Journal of the American Chemical Society 120, no. 38 (September 1998): 9963–64. http://dx.doi.org/10.1021/ja982298n.

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18

Cooperband, L. R., and T. J. Logan. "Measuring In Situ Changes in Labile Soil Phosphorus with Anion-Exchange Membranes." Soil Science Society of America Journal 58, no. 1 (January 1994): 105–14. http://dx.doi.org/10.2136/sssaj1994.03615995005800010015x.

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19

Sibbesen, E., and G. H. Rubaek. "Labile, organic phosphorus in incubated soils estimated by macroporous anion‐exchange resin." Communications in Soil Science and Plant Analysis 25, no. 9-10 (June 1994): 1671–83. http://dx.doi.org/10.1080/00103629409369143.

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20

Burba, Peter. "Labile/inert metal species in aquatic humic substances: an ion-exchange study." Fresenius' Journal of Analytical Chemistry 348, no. 4 (1994): 301–11. http://dx.doi.org/10.1007/bf00324039.

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21

Leeflang, Bas R., and Johannes F. G. Vliegenthart. "Relayed NOE experiments for discrimination of exchange effects of overlapping labile protons." Journal of Magnetic Resonance (1969) 89, no. 3 (October 1990): 615–19. http://dx.doi.org/10.1016/0022-2364(90)90347-c.

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22

Kitada, Atsushi, Kohei Kintsu, Shun Takeoka, Kazuhiro Fukami, Masayuki Saimura, Takashi Nagata, Masato Katahira, and Kuniaki Murase. "A Hydronium Solvate Ionic Liquid: Ligand Exchange Conduction Driven by Labile Solvation." Journal of The Electrochemical Society 165, no. 9 (2018): H496—H499. http://dx.doi.org/10.1149/2.0971809jes.

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23

Beveridge, A. "Evaluation of “labile” metal in sediments by use of ion-exchange resins." Talanta 36, no. 5 (May 1989): 535–42. http://dx.doi.org/10.1016/0039-9140(89)80120-1.

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24

Slavek, J. "Labile metal content of sediments—fractionation scheme based on ion-exchange resins." Talanta 37, no. 4 (April 1990): 397–406. http://dx.doi.org/10.1016/0039-9140(90)80231-4.

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25

Helfenstein, Julian, Chiara Pistocchi, Astrid Oberson, Federica Tamburini, Daniel S. Goll, and Emmanuel Frossard. "Estimates of mean residence times of phosphorus in commonly considered inorganic soil phosphorus pools." Biogeosciences 17, no. 2 (January 30, 2020): 441–54. http://dx.doi.org/10.5194/bg-17-441-2020.

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Abstract. Quantification of turnover of inorganic soil phosphorus (P) pools is essential to improve our understanding of P cycling in soil–plant systems and improve representations of the P cycle in land surface models. Turnover can be quantified using mean residence time (MRT); however, to date there is little information on MRT of P in soil P pools. We introduce an approach to quantify MRT of P in sequentially extracted inorganic soil P pools using data from isotope exchange kinetic experiments. Our analyses of 53 soil samples from the literature showed that MRT of labile P (resin- and bicarbonate-extractable P) was on the order of minutes to hours for most soils, MRT in NaOH-extractable P (NaOH-P) was in the range of days to months, and MRT in HCl-extractable P (HCl-P) was on the order of years to millennia. Multiple-regression models were able to capture 54 %–63 % of the variability in MRT among samples and showed that land use was the most important predictor of MRT of P in labile and NaOH pools. MRT of P in HCl-P was strongly dependent on pH, as high-pH soils tended to have longer MRTs. This was interpreted to be related to the composition of HCl-P. Under high pH, HCl-P contains mostly apatite, with a low solubility, whereas under low-pH conditions, HCl-P may contain more exchangeable P forms. These results suggest that current land surface models underestimate the dynamics of inorganic soil P pools and could be improved by reducing model MRTs of the labile and NaOH-P pools, considering soil-type-dependent MRTs rather than universal exchange rates and allowing for two-way exchange between HCl-P and the soil solution.
26

Kolář, L., V. Vaněk, S. Kužel, J. Peterka, J. Borová-Batt, and J. Pezlarová. "Relationships between quality and quantity of soil labile fraction of the soil carbon in Cambisols after liming during a 5-year period." Plant, Soil and Environment 57, No. 5 (May 16, 2011): 193–200. http://dx.doi.org/10.17221/453/2010-pse.

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The labile fraction of soil organic carbon (SOC) in terms of its quantity is a sensitive but dynamic indicator of the reactive agent in soils. If it is to be considered as a feature of soil quality, the value of its quantity should be completed by data on its quality. It can be expressed by the value of the rate constant of microbial oxidation k<sub>bio</sub> of this fraction or by data on chemical stability during hydrolysis or oxidation. If the quality of SOC labile fraction is not determined, at least the ratio of C<sub>MIC</sub>: C<sub>org</sub> should be given. The adjustment of soil acidity increases the microbial activity of soils, therefore the quantity of SOC labile fraction decreases and at the same time kbio decreases proportionately to the increasing stability of soil organic matters. During a 5-year period after the liming the soils acidify again and this process passes the faster the lesser their ion exchange capacity and buffering are. The quantity of the labile fraction of SOC raises again, its stability decreases and k<sub>bio</sub> raises again. The conversion pH value has secondary relevance.
27

STEWART, J. W. B., I. P. O'HALLORAN, and R. G. KACHANOSKI. "INFLUENCE OF TEXTURE AND MANAGEMENT PRACTICES ON THE FORMS AND DISTRIBUTION OF SOIL PHOSPHORUS." Canadian Journal of Soil Science 67, no. 1 (February 1, 1987): 147–63. http://dx.doi.org/10.4141/cjss87-013.

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Changes in soil phosphorus (P) forms, as determined by a sequential fractionation procedure, were used to assess the influence of soil texture and management practices on the forms and distribution of soil P in a Brown Chernozemic loam soil at Swift Current, Saskatchewan. Significant proportions of the variability of all P fractions except residual-P could be attributed to changes in sand content. Changes in the forms and distribution of soil P with decreasing sand content followed patterns similar to those associated with a weathering sequence. The proportion of total soil P in inorganic and organic extractable forms that were extractable sequentially with anion exchange resin (resin-Pi), sodium bicarbonate (bicarb-Pi and -Po), and sodium hydroxide (NaOH-Pi and -Po) increased with decreasing sand content. Acid-extractable inorganic P (HCl-Pi) was the only P fraction positively correlated with sand content. The presence of a crop increased the proportion of soil P present as the more labile organic-P fractions (bicarb-Po and NaOH-Po) but not as total soil organic P (soil-Po). The presence of a crop also increased the proportion of soil P present as the labile inorganic fractions (resin-Pi and bicarb-Pi), possibly due to a decrease in soil pH. Application of inorganic-P fertilizer caused significant increases in the proportion of soil P as these labile inorganic-P fractions (resin-Pi and bicarb-Pi) and as total soil organic-P (soil-Po), but did not affect the more labile organic-P fractions. Key words: P fractionation, labile P, organic P, inorganic P, texture, management practices
28

Thureau, Pierre, Bernard Ancian, Stéphane Viel, and André Thévand. "Determining chemical exchange rates of the uracil labile protons by NMR diffusion experiments." Chem. Commun., no. 2 (2006): 200–202. http://dx.doi.org/10.1039/b513580j.

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29

Clark, Andrew C, and Geoffrey R Scollary. "Medium Exchange Stripping Potentiometry for the Measurement of Labile Copper in White Wine." Electroanalysis 18, no. 18 (September 2006): 1793–99. http://dx.doi.org/10.1002/elan.200603588.

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30

Schenk, Wolfdieter A., Ute Karl, and Michael R. Horn. "Kationische Schwefeldioxid-Komplexe des Eisens und Rutheniums vom Halbsandwich-Typ [1] / Cationic Halfsandwich-Type Sulfur Dioxide Complexes of Iron and Ruthenium [1]." Zeitschrift für Naturforschung B 44, no. 12 (December 1, 1989): 1513–18. http://dx.doi.org/10.1515/znb-1989-1208.

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Cationic halfsandwich-type complexes of sulfur dioxide, [C5R5M(PR3)2(SO2)]+ (R = H, Me, M = Fe, Ru, (PR3)2 = mono- or bidentate phosphorus ligands) and [C5Me5Fe(CO)(PR3)(SO2)]+, are obtained by ligand exchange from labile cationic (M = Fe) or neutral (M = Ru) precursors. The new compounds are characterized by IR, 1H131H, 13C and 31P NMR spectroscopy. Their stability increases with increasing electron density at the metal.
31

Bo, Shaowei, Dong Zhang, Mengjie Ma, Xukai Mo, Julia Stabinska, Michael T. McMahon, Changzheng Shi, and Liangping Luo. "Acyl Hydrazides and Acyl Hydrazones as High-Performance Chemical Exchange Saturation Transfer MRI Contrast Agents." Pharmaceuticals 16, no. 5 (April 23, 2023): 639. http://dx.doi.org/10.3390/ph16050639.

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Chemical exchange saturation transfer (CEST) MRI is a versatile molecular imaging approach that holds great promise for clinical translation. A number of compounds have been identified as suitable for performing CEST MRI, including paramagnetic CEST (paraCEST) agents and diamagnetic CEST (diaCEST) agents. DiaCEST agents are very attractive because of their excellent biocompatibility and potential for biodegradation, such as glucose, glycogen, glutamate, creatine, nucleic acids, et al. However, the sensitivity of most diaCEST agents is limited because of small chemical shifts (1.0–4.0 ppm) from water. To expand the catalog of diaCEST agents with larger chemical shifts, herein, we have systematically investigated the CEST properties of acyl hydrazides with different substitutions, including aromatic and aliphatic substituents. We have tuned the labile proton chemical shifts from 2.8–5.0 ppm from water while exchange rates varied from ~680 to 2340 s−1 at pH 7.2, which allows strong CEST contrast on scanners down to B0 = 3 T. One acyl hydrazide, adipic acid dihydrazide (ADH), was tested on a mouse model of breast cancer and showed nice contrast in the tumor region. We also prepared a derivative, acyl hydrazone, which showed the furthest shifted labile proton (6.4 ppm from water) and excellent contrast properties. Overall, our study expands the catalog of diaCEST agents and their application in cancer diagnosis.
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Jin, Tao, Joonas Autio, Takayuki Obata, and Seong-Gi Kim. "Spin-locking versus chemical exchange saturation transfer MRI for investigating chemical exchange process between water and labile metabolite protons." Magnetic Resonance in Medicine 65, no. 5 (November 30, 2010): 1448–60. http://dx.doi.org/10.1002/mrm.22721.

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Nguyen, Hong Lien, Anh Tuan Phung, Trung Kien Tran, Trung Hai Huynh, and Bich Huong La. "Evaluating the Performance of a Diffusive Gradient in Thin Film Embedded with Montmorillonite for the Determination of Labile Cd, Pb, Mn, and Zn in Natural River Water." Journal of Chemistry 2020 (November 16, 2020): 1–12. http://dx.doi.org/10.1155/2020/1483909.

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Montmorillonite (MMT), a natural clay mineral with high ion-exchange capacity and trace metal adsorbability, has been demonstrated to be a suitable binding phase in the diffusive gradient in thin film (DGT) technique for the determination of labile trace metals in synthetic water samples. However, in situ working performance of DGT-MMT with natural river water has not yet been investigated. The present study examined the performance of a DGT containing montmorillonite (MMT) for the in situ isolation and determination of labile Cd, Pb, Mn, and Zn fractions in Lach Tray River water, North Vietnam. The repeatability and accuracy of the DGT-MMT probe were assessed on the basis of seven measurement replicates performed on Cd2+, Pb2+, Mn2+, and Zn2+ standard solutions. Then, the DGT-MMT probes were deployed in Lach Tray River water at different sampling sites to determine the labile metal fractions present in river water. By comparing the total and dissolved metal concentrations in the river water, the distributions of the four tested trace metals were constructed. The proportions of the dissolved fractions of Cd, Pb, Mn, and Zn were 46.7–73.7%, 38.5–63.9%, 36.4–41.6%, and 49.8–67.7%, respectively. The results also showed that the high accuracy and reproducibility of the DGT-MMT data were comparable with measurements obtained by the commonly used DGT-Chelex-100 method. In comparison with the data obtained from anodic stripping voltammetry (ASV), a traditional technique for the determination of non-in situ speciation of trace metals, labile metal concentrations measured by DGT-MMT were in similar ranges. These findings indicate that naturally available montmorillonite can be used as an alternative binding material in DGT probes for the in situ determination of labile metal concentrations in natural watercourses.
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Podrebarac, Frances A., Sharon A. Billings, Kate A. Edwards, Jérôme Laganière, Matthew J. Norwood, and Susan E. Ziegler. "Soil profile connectivity can impact microbial substrate use, affecting how soil CO<sub>2</sub> effluxes are controlled by temperature." Biogeosciences 18, no. 16 (August 20, 2021): 4755–72. http://dx.doi.org/10.5194/bg-18-4755-2021.

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Abstract. Determining controls on the temperature sensitivity of heterotrophic soil respiration remains critical to incorporating soil–climate feedbacks into climate models. Most information on soil respiratory responses to temperature comes from laboratory incubations of isolated soils and typically subsamples of individual horizons. Inconsistencies between field and laboratory results may be explained by microbial priming supported by cross-horizon exchange of labile C or N. Such exchange is feasible in intact soil profiles but is absent when soils are isolated from surrounding depths. Here we assess the role of soil horizon connectivity, by which we mean the degree to which horizons remain layered and associated with each other as they are in situ, on microbial C and N substrate use and its relationship to the temperature sensitivity of respiration. We accomplished this by exploring changes in C : N, soil organic matter composition (via C : N, amino acid composition and concentration, and nuclear magnetic resonance spectroscopy), and the δ13C of respiratory CO2 during incubations of organic horizons collected across boreal forests in different climate regions where soil C and N compositions differ. The experiments consisted of two treatments: soil incubated (1) with each organic horizon separately and (2) as a whole organic profile, permitting cross-horizon exchange of substrates during the incubation. The soils were incubated at 5 and 15 ∘C for over 430 d. Enhanced microbial use of labile C-rich, but not N-rich, substrates were responsible for enhanced, whole-horizon respiratory responses to temperature relative to individual soil horizons. This impact of a labile C priming mechanism was most emergent in soils from the warmer region, consistent with these soils' lower C bioreactivity relative to soils from the colder region. Specifically, cross-horizon exchange within whole soil profiles prompted increases in mineralization of carbohydrates and more 13C-enriched substrates and increased soil respiratory responses to warming relative to soil horizons incubated in isolation. These findings highlight that soil horizon connectivity can impact microbial substrate use in ways that affect how soil effluxes of CO2 are controlled by temperature. The degree to which this mechanism exerts itself in other soils remains unknown, but these results highlight the importance of understanding mechanisms that operate in intact soil profiles – only rarely studied – in regulating a key soil–climate feedback.
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Shimano, H., N. Yamada, S. Ishibashi, H. Mokuno, N. Mori, T. Gotoda, K. Harada, Y. Akanuma, T. Murase, and Y. Yazaki. "Oxidation-labile subfraction of human plasma low density lipoprotein isolated by ion-exchange chromatography." Journal of Lipid Research 32, no. 5 (May 1991): 763–74. http://dx.doi.org/10.1016/s0022-2275(20)42028-0.

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Waller, Pamela A., and William F. Pickering. "Determination of ‘labile’ phosphate in lake sediments using anion exchange resins: a critical evaluation." Chemical Speciation & Bioavailability 4, no. 2 (July 1992): 59–68. http://dx.doi.org/10.1080/09542299.1992.11083179.

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Otmar, Miroslav, Milena Masojídková, Ivan Votruba, and Antonín Holý. "An Alternative Synthesis of HPMPC and HPMPA Diphosphoryl Derivatives." Collection of Czechoslovak Chemical Communications 66, no. 3 (2001): 500–506. http://dx.doi.org/10.1135/cccc20010500.

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In (S)-1-[3-hydroxy-2-(phosphonomethoxy)propyl]cytosine (HPMPC) and (S)-9-[3-hydroxy-2-(phosphonomethoxy)propyl]adenine (HPMPA) with 3-hydroxy functions protected with 4,4'-dimethoxytrityl (DMTr) groups, phosphonate groups were transformed to the morpholides and treated with bis(tributylammonium) diphosphate. Selective cleavage of the DMTr group in the presence of the labile diphosphate residue was achieved in water at pH 2.5. Purification by charcoal adsorption followed by anion exchange chromatography afforded phosphonate-diphosphate compounds (HPMPCpp, HPMPApp).
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Schmitt, Djalma Eugênio, Jucinei José Comin, Carlos Alberto Ceretta, Luciano Colpo Gatiboni, Tales Tiecher, Felipe Lorensini, Janaina Heinzen, Vítor Gabriel Ambrosini, Marcel Pires de Moraes, and Gustavo Brunetto. "Accumulation of phosphorus fractions and contamination potential in vineyard soils in the southern region of the state of Santa Catarina, Brazil." Revista Brasileira de Ciência do Solo 37, no. 5 (October 2013): 1256–66. http://dx.doi.org/10.1590/s0100-06832013000500015.

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In vineyards, if phosphate is applied both before planting and at intervals during growth without consideration of technical criteria, the soil P fractions may be increased and their proportions altered. This study was carried out to evaluate the accumulation of P fractions and the parameters of the adsorption isotherm in a sandy Typic Hapludalf soil in vineyards with a history of successive and excessive phosphate fertilization. In December 2010, two vineyards were selected, one 4 and the other 15 years old, in Urussanga, State of Santa Catarina (Brazil). Three trenches were dug in each area and soil was collected from the 0-5, 5-10 and 10-20 cm depth ranges. The soil samples were dried in a forced-air oven, sieved and subjected to chemical analyses, P chemical fractionation and P adsorption isotherms. Excessive phosphate fertilization, before and during cultivation, particularly in the older vineyard and, consequently, with a longer history of phosphate fertilization, increased the inorganic P concentrations to the depth of 20 cm, especially in labile fractions extracted by anion exchange resin and NaHCO3 in the non-labile fraction, as well as in the non-labile fraction extracted by 1.0 mol L-1 HCl. The application of phosphate fertilizers and the long cultivation period increased the P levels in the organic labile fraction extracted by 0.5 mol L-1 NaHCO3, and especially in the moderately labile fraction extracted by 0.1 and 0.5 mol L-1 NaOH. Phosphate fertilization of older vineyards, i.e., cultivated for 15 years, increased the amounts of P desorbed in water, indicating a risk of contamination of surface waters and groundwater. The phosphate fertilization before planting, without considering the results of soil analysis, and during cultivation, disregarding the results of soil analysis, leaf analysis and expected yield, led to a reduction in the maximum P adsorption capacity in the 0-5 cm layer of vineyard 2, indicating saturation of part of the reactive particle adsorption sites.
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Seifert, Sepp, Antje Gupta, Rosemarie Syhre, Hartmut Spies, and Bernd Johannsen. "Ligand-exchange reaction of labile “3+1”99mTc(V) complexes with SH group-containing proteins." Applied Radiation and Isotopes 54, no. 4 (February 2001): 637–44. http://dx.doi.org/10.1016/s0969-8043(00)00309-2.

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Ferrante, Andrea, and Jack Gorski. "A peptide/MHCII conformer generated in the presence of exchange peptide is the substrate for HLA-DM editing (106.30)." Journal of Immunology 188, no. 1_Supplement (May 1, 2012): 106.30. http://dx.doi.org/10.4049/jimmunol.188.supp.106.30.

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Abstract The mechanism of HLA-DM (DM) activity is still unclear. We have shown that peptide release from HLA-DR (DR) in the presence of DM is dependent on the presence of an exchange peptide. However, DM also promotes a small but measurable peptide release in the absence of exchange peptide. Here we show that non-denaturing SDS-PAGE separates purified peptide/DR1 (pDR1) complexes into two conformers whose ratio is dependent on peptide KD. In the absence of an exchange peptide, DM only releases peptide from the slower migrating conformer. Upon the addition of an exchange peptide, a portion of the DM-resistant conformer can be converted to the slower migrating conformer, which in turn is DM labile. Our results indicate that exchange peptide generates a conformer of the pDR1 complex, which constitutes the intermediate for peptide exchange and is also the substrate for DM activity. The resolution of the intermediate favors the peptide with the greatest ability to fold itself and the groove into a stable, low-energy complex. However, once folded into the DM-resistant conformer, even a low affinity peptide can be presented in the absence of free peptide, increasing the peptide repertoire available for presentation.
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Loureiro, Diego Campana, Helvécio De-Polli, Marcos Bacis Ceddia, and Adriana Maria de Aquino. "Spatial variability of microbial biomass and organic matter labile pools in a haplic planosol soil." Bragantia 69, suppl (2010): 85–95. http://dx.doi.org/10.1590/s0006-87052010000500010.

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The objective of this work was to study the spatial variability of soil microbial biomass (SMB) and labile soil organic matter pools (labile SOM), under different management systems and plant cover. The experiment was conducted in a Haplic Planosol soil on an Integrated Agroecological Production System (SIPA), in Seropédica, Rio de Janeiro. The evaluated management systems were: alley cropping, pasture, and bush garden, the late one was used as reference area. Three grids of regular spacing of 2.5 x 2.5 meters were used for sampling, consisting of 25 georeferenced points each, where soil samples were taken at 0-10 cm depth. The following labile constituents of soil organic matter were determined: free light fraction (FLF), water soluble C and N, C and N of SMB (SMB-C and SMB-N), and glomalin content. The textural fractions (sand, silt, and clay), pH in water, and chemical attributes (organic C, total N, Ca, Mg, Al, P, K, and CEC-cation exchange capacity) were also determined. The areas of alley cropping and pasture showed spatial dependence to the attributes of SOM. The occurrence of high spatial dependence for the attributes associated to microbial biomass in the alley cropping system (C, FLF, SMB-N and respiration), probably was due to external factors related to management, such as: intensive rotational cropping system, diversity of crops and different inputs of organic matter to soil such as pruning material and organic compost.
42

Degel, F., P. Zuman, P. Jandik, and G. Gilch. "Effect of pretreating samples with boric acid before liquid-chromatographic determination of urinary catecholamines." Clinical Chemistry 33, no. 1 (January 1, 1987): 108–12. http://dx.doi.org/10.1093/clinchem/33.1.108.

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Abstract Isolation of catecholamines on prepacked gravity-fed ion-exchange columns in conjunction with liquid-chromatographic separation is occasionally subject to disturbances of unknown origin, especially after injection of H3BO3 eluates from the ion-exchange columns onto the chromatography column. Peak spreading, sometimes even peak splitting, has been observed in many laboratories--effects easily confused with those sometimes caused by voided columns or by impurities. To elucidate the origins of these interferences, we performed a combined voltammetric and chromatographic investigation. We show that complexation of the catechol group by borate ions and dissociation of those pH-labile complexes in the course of the chromatographic separation is the cause of those peak distortions. Addition of a small volume of diluted HCI to the borate eluates eliminates such interference and leads to reproducible, easily interpretable chromatographic separations.
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Kislyuk, Victor, Andrii Melnyk, Yuliia Bondar, and Volodymyr Trachevskij. "A conceptual approach to the formation of paramagnetic nanospecies of noble metals." Journal of Electrical Engineering 70, no. 7 (December 1, 2019): 83–88. http://dx.doi.org/10.2478/jee-2019-0046.

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Abstract The general concepts are analyzed regarding the approach for the formation of paramagnetic species of noble metals, with a non-rigid (labile) molecule being used as a supporting matrix. The formation of the metal nanospecies follows three stages: (i) the metal ions are captured by the matrix, (ii) the reducing agent causes formation of individual atoms separated by the matrix fragments, (iii) the individual atoms agglomerate due to conformational transformations of the labile molecule-matrix. This algorithm is realized in two distinct systems: Ag-containing nanospecies embedded within the system of polyacrylic acid (PAA) chains grafted to the film of fluorinated ethylene propylene copolymer (FEP) and Au-containing nanospecies in the free matrix of tannin-citrate- oxo-hydroxo aluminate. The evolution of the electron paramagnetic resonance (EPR) spectra while cooling down demonstrates the appearance of the exchange interaction which is suppressed at higher temperatures by the vibrational modes of the molecule-matrix. The role of the oxo-hydroxo aluminate form is one of a molecular motor sorting the individual nanospecies by their size and charge state.
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Huff, Tyler C., Vladimir Camarena, David W. Sant, Zachary Wilkes, Derek Van Booven, Allegra T. Aron, Ryan K. Muir, et al. "Oscillatory cAMP signaling rapidly alters H3K4 methylation." Life Science Alliance 3, no. 1 (December 27, 2019): e201900529. http://dx.doi.org/10.26508/lsa.201900529.

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Epigenetic variation reflects the impact of a dynamic environment on chromatin. However, it remains elusive how environmental factors influence epigenetic events. Here, we show that G protein–coupled receptors (GPCRs) alter H3K4 methylation via oscillatory intracellular cAMP. Activation of Gs-coupled receptors caused a rapid decrease of H3K4me3 by elevating cAMP, whereas stimulation of Gi-coupled receptors increased H3K4me3 by diminishing cAMP. H3K4me3 gradually recovered towards baseline levels after the removal of GPCR ligands, indicating that H3K4me3 oscillates in tandem with GPCR activation. cAMP increased intracellular labile Fe(II), the cofactor for histone demethylases, through a non-canonical cAMP target—Rap guanine nucleotide exchange factor-2 (RapGEF2), which subsequently enhanced endosome acidification and Fe(II) release from the endosome via vacuolar H+-ATPase assembly. Removing Fe(III) from the media blocked intracellular Fe(II) elevation after stimulation of Gs-coupled receptors. Iron chelators and inhibition of KDM5 demethylases abolished cAMP-mediated H3K4me3 demethylation. Taken together, these results suggest a novel function of cAMP signaling in modulating histone demethylation through labile Fe(II).
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SHAFII, NOORAZLIYANA, NOOR AZLIN AZRAINI CHE SOH, TUAN SALWANI TUAN ISMAIL, JULIA OMAR, WAN NORLINA WAN AZMAN, ANIZA MAT JELANI, WAN NOR FAZILA HAFIZAN WAN NIK, et al. "INTERFERENCES OF HbA1c ANALYSIS IN HOSPITAL UNIVERSITI SAINS MALAYSIA – 3 YEARS STUDY." Malaysian Applied Biology 50, no. 2 (November 30, 2021): 19–23. http://dx.doi.org/10.55230/mabjournal.v50i2.1978.

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Haemoglobin A1c (HbA1c) is used to monitor glycaemic control and predict diabetic complications. Measurement of HbA1c can be interfered by haemoglobin (Hb) variant and other Hb derivatives include carbamylated Hb and elevated labile A1c. This study is to determine the percentages and type of interferences during HbA1c analysis and the percentages of non- reportable HbA1c results. This is a cross-sectional study using retrospective data of HbA1c. The HbA1c is measured on Biorad D10 using the ion-exchange high-performance liquid chromatography method. The data were analyzed using descriptive statistics. A total of 26,560 patients were included. The result showed the presence of interferences of 2269 (8.56%). The most common causes of the interferences were the Hb variant (8.48%) followed by carbamylated Hb and labile A1c (0.03% each). The non-reportable HbA1c results were 0.46% with the Hb variant contributed most of the causes. By knowing the presence of interferences particularly the Hb variant, the HbA1c results hopefully are interpreted with caution and correct management can be given to the patients.
46

Shoji, S., K. A. Rickard, R. F. Ertl, J. Linder, and S. I. Rennard. "Lung fibroblasts produce chemotactic factors for bronchial epithelial cells." American Journal of Physiology-Lung Cellular and Molecular Physiology 257, no. 2 (August 1, 1989): L71—L79. http://dx.doi.org/10.1152/ajplung.1989.257.2.l71.

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The interaction between the epithelial cells and the subjacent mesenchymal cells in the airway is thought to play a major role during tissue repair and morphogenesis. To evaluate this interaction, we cultured human lung fibroblasts and bovine bronchial epithelial cells and determined that fibroblast-conditioned medium has chemotactic activity for bronchial epithelial cells. This activity was nondialyzable, heat labile, pepsin labile, acid stable, lipid inextractable, and eluted from Sephadex G-150 column chromatography in the high-molecular-weight range. DEAE-Sephacyl ion exchange and gelatin-Sepharose affinity chromatography revealed two peaks containing chemotactic activity, one of which may be fibronectin, since it binds to gelatin, reacts in a specific immunoassay, and is inhibited of chemotactic activity by anti-fibronectin antiserum, and another of which does not appear to be fibronectin, since it does not bind to gelatin nor react in the immunoassay. Thus lung fibroblasts can produce at least two chemotactic factors for bronchial epithelial cells that may play a role during lung tissue repair and morphogenesis by modulating bronchial epithelial cell migration.
47

Dinu, Marina. "Seasonal Changes in Qualitative and Quantitative Characteristics of Humic Substances in Waters of Different Genesis: Membrane Technologies and Equilibrium Processes." Membranes 13, no. 3 (March 15, 2023): 340. http://dx.doi.org/10.3390/membranes13030340.

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Membrane filtration methods were applied in this study to research natural waters specification (and speciation). Lysimetric waters (soil waters) of background territories in different seasons are considered. Features of the change in molecular weights, elemental composition, and zeta potential of organic matter during fractionation from 8 μm to 100 kDa were found. The number of labile and non-labile speciation of some elements obtained by membrane filtration and ion-exchange separation methods were found and compared. The highest molecular weights of organic substances were found in summer samples of lysimetric waters (more than 100 kDa) with a predominance of the aromatic component in the IR spectra of the samples. Several maxima were also found in the molecular weight distribution, including the increase in autochthonous organic substances. The most stable negative zeta potential, as a stabilized colloid matter, are represented in summer (near −26 mV) and in autumn (near −22 mV) lysimetric water. A slight increase in metal ions bound into organic complexes is typical for summer and autumn samples.
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Kopecký, Marek, Ladislav Kolář, Kristýna Perná, Radka Váchalová, Petr Mráz, Petr Konvalina, Yves Theoneste Murindangabo, Mohammad Ghorbani, Ladislav Menšík, and Miroslav Dumbrovský. "Fractionation of Soil Organic Matter into Labile and Stable Fractions." Agronomy 12, no. 1 (December 29, 2021): 73. http://dx.doi.org/10.3390/agronomy12010073.

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The present study aims to test and evaluate the efficiency of a new modified method of organic matter evaluation. It allows the assessment of the quality and quantity of the primary soil organic matter and the stable organic fractions separately. The new method was tested in six soil samples of different localities in the Czech Republic. This method is based on observing reaction kinetics during the oxidation of soil organic matter and measuring the cation-exchange capacity of stable organic fractions. The results were compared with classical methods, which rely on the isolation of humic substances, determination of the content of humic acids and fulvic acids and their ratio CHA:CFA, quotient E4/6, and fractionation of soil organic matter according to resistance to oxidation. It turned out that the results of the new modified method are more sensitive in comparison with the results obtained by classical procedures. The linear regression demonstrated the dependence between the amounts of soil organic matter determined by the classical method compared with the modified method. Moreover, the new modified method was found to be faster and not demanding on laboratory equipment. The new method has been improved to be easily repeatable, and some shortcomings of the previous method were eliminated. Based on our results and other recent studies, the modified method may be recommended for the practical evaluation of soil organic matter conditions.
49

Prosser, S., and H. Peemoeller. "Nature of lysozyme–water interactions by proton NMR." Biochemistry and Cell Biology 69, no. 5-6 (May 1, 1991): 341–45. http://dx.doi.org/10.1139/o91-053.

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Proton spin-lattice relaxation measurements were performed in 10 mM lysozyme solution as a function of temperature and degree of substitution of solvent H2O with D2O. The results show that in the temperature range from 274 to 323 K, the intermolecular lysozyme proton water proton coupling contributes appreciably to the observed water proton relaxation rate. In this system exchange between water protons and labile protein protons does not dominate the behaviour with temperature of the water–lysozyme intermolecular contribution to the spin-lattice relaxation.Key words: NMR, lysozyme, relaxation-contributions.
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Miller, James E., and Dennis H. Brown. "Studies of Ammonia Uptake and Loss by Lichens." Lichenologist 31, no. 1 (January 1999): 85–93. http://dx.doi.org/10.1006/lich.1998.0178.

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AbstractThe passive uptake of ammonium ions to extracellular cation binding sites has been demonstrated for a range of lichen species. The possible competitive effect of other cations on ammonium binding is discussed. Binding of uncharged gaseous ammonia to exchange sites was also shown. The rapid loss of exchangeable ammonium from extracellular sites has been demonstrated and, because the greatest losses occur in living material, intracellular uptake is inferred. The labile nature of bound ammonium means that transfer of material to the laboratory for analysis may result in the underestimation of the amount bound.

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