The Kinetics and Mechanism of a Reaction in Which Ligand Substitution is Accompanied by a Spin-State Change: Observation of the Elusive Monodithiocarbamatonickel(II) Complex in Dimethyl Sulfoxide

1979 ◽  
Vol 32 (8) ◽  
pp. 1679 ◽  
Author(s):  
PJ Nichols ◽  
MW Grant
Keyword(s):  
Dimethyl Sulfoxide ◽  
Electronic Spectrum ◽  
Ligand Substitution ◽  
The Other ◽  
Direct Reaction ◽  
State Change ◽  
Low Concentrations ◽  
High Concentrations ◽  
Dimerization Reaction ◽  
Very High

In solutions in Me2SO containing low concentrations of diethyldithiocarbamate ion (dtc-) and very high concentrations of Ni(Me2SO)62+ ion, the hitherto undetected Ni(dtc)+ complex is kinetically stabilized and its electronic spectrum can be recorded. The mono complex is thermodynamically unstable and is converted into Ni(dtc)2 by two independent pathways, one involving direct reaction between Ni(dtc)+ and dtc-, the other being a dimerization reaction, 2Ni(dtc)+ → Ni2+ + Ni(dtc)2. Analysis of the mechanistic scheme Ni2+ + dtc ↔ Ni(dtc)2 Ni(dtc)+ + dtc- → Ni(dtc)2 2Ni(dtc)+ → Ni2+ + Ni(dtc)2 gives k1 = 3 × 103 l, mol-1 s-1, k-1 ≈ 0.01 s-1, k2 ≈ 4 × 105 l, mol-1 s-1 and k3 ≈ 1 × 103 l. mol-1 s-1. Coordinated dtc- exerts a significant labilizing effect on coordinated Me2SO molecules in Ni(dtc)+.

scholarly journals The clinical cross-reactivity and immunological cross-antigenicity of wheat and barley

2021 ◽  
Author(s):  
Shohei Kubota ◽  
Yuji Aoki ◽  
Tomomi Sskai ◽  
Katsumasa Kitamura ◽  
Teruaki Matsui ◽  
...  
Keyword(s):  
Oral Immunotherapy ◽  
Cross Reactivity ◽  
The Other ◽  
Enzyme Linked Immunosorbent Assay ◽  
Wheat Allergy ◽  
Extract Concentration ◽  
Low Concentrations ◽  
High Concentrations ◽  
Food Challenges ◽  
Elisa Inhibition

Background: Some patients with a wheat allergy have been reported to show clinical cross-reactivity to barley. However, it is not clear whether the development of barley allergy in patients with a wheat allergy is due to cross-antigenicity between wheat and barley. In our study, we aimed to determine the clinical cross-reactivity and immunological cross-antigenicity of wheat and barley. Methods: We compared the results of barley oral food challenges (OFCs) before oral immunotherapy (OIT) for wheat with those after OIT in nine patients with a wheat allergy to estimate the clinical cross-reactivity of wheat and barley. Moreover, we performed enzyme-linked immunosorbent assay (ELISA) inhibition and immunoblotting inhibition using serum from seven patients allergic to wheat and barley. Results: Nine patients who had positive barley-OFC results performed before OIT for wheat were all negative on barley-OFC performed after OIT. In ELISA inhibition, preincubation of serum from patients allergic to wheat and barley with a high barley extract concentration inhibited binding of IgE to wheat extract by less than 10%. On the other hand, wheat and barley extracts equally inhibited binding to barley sIgE at high concentrations. In the immunoblotting inhibition test, the spots of wheat were inhibited but weakly by barley extracts, and most of the spots of barley were inhibited even by low concentrations of the wheat and barley extract. Conclusion: We showed that barley allergy associated with wheat allergy is caused by cross-reactivity from wheat. The OIT for wheat was one of the promising options for barley allergy.

scholarly journals Detection of endotoxins with the Limulus test in burned and unburned mice infected with different species of gramnegative bacteria

1975 ◽  
Vol 75 (1) ◽  
pp. 99-112 ◽  
Author(s):  
R. J. Jones ◽  
E. A. Roe ◽  
R. E. Dyster
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Gram Negative Bacteria ◽  
Gram Negative ◽  
Low Concentrations ◽  
High Concentrations ◽  
Very High ◽  
Limulus Test

SUMMARYThe Limulus test detected endotoxins in the plasma of burned and unburned mice infected with different species of gram-negative bacteria. Individual strains of different species of gram-negative bacteria produced different amounts of endotoxin in the plasma of infected mice. Plasma from mice given lethal infections showed very high concentrations of endotoxin. Low concentrations of endotoxin in the plasma were tolerated by mice but high concentrations were invariably fatal. A polyvalent pseudomonas vaccine reduced endotoxin in the plasma of mice given lethal infections of Pseudomonas aeruginosa.

The influence of type and timing of protein supplementation on wool growth and protein synthesis in the skin of young Merino sheep

1999 ◽  
Vol 50 (4) ◽  
pp. 497 ◽  
Author(s):  
D. G. Masters ◽  
G. Mata ◽  
S. M. Liu
Keyword(s):  
Protein Synthesis ◽  
Experimental Period ◽  
Protein Supplementation ◽  
The Other ◽  
Canola Meal ◽  
Protein Supplements ◽  
Wool Growth ◽  
Low Concentrations ◽  
High Concentrations ◽  
Dietary Treatments

There is limited evidence that the response in wool growth resulting from feeding protected protein supplements continues after the feeding has stopped. Feeding such proteins, alternated with traditional supplements, may increase wool growth as much as continuous feeding but at a lower cost. This experiment aimed to determine whether the response to protected protein continued after the sheep were switched to a cereal supplement. Over a 2-month experimental period, 56 weaners (5 months old, weighing 26 kg) were used in a 2 × 2 factorial experiment. Half were fed a diet containing 25% canola meal [partially protected protein with high concentrations of sulfur amino acids (SAA)] mixed with oaten hay, urea, and minerals. The other half were fed the same diet but with lupin seed (highly degradable protein with low concentrations of SAA) replacing the canola meal. Within each of the 2 dietary treatments and in each of 2 months, half of the weaners were fed the diet continuously, the other half were fed the diet for 2 weeks followed by 2 weeks of a barley, oats, hay, urea, and minerals diet. Another group of 8 weaners was fed the oats–barley diet continuously for 2 months. All sheep were fed to lose 35 g liveweight/day. Weaners fed canola meal grew 11% more wool during the experiment and had a higher rate of protein synthesis in the skin than weaners fed lupins. The response to canola meal of wool and skin was the same whether feeding was continuous or alternated with oats–barley, indicating that the benefits from feeding partially protected proteins continues after feeding has stopped.

Copper, nickel, and thallium uptake by the lichen Cladina rangiferina

1981 ◽  
Vol 59 (1) ◽  
pp. 91-100 ◽  
Author(s):  
M. A. S. Burton ◽  
P. LeSueur ◽  
K. J. Puckett
Keyword(s):  
Metal Uptake ◽  
Deionized Water ◽  
Metabolic Inhibitors ◽  
Temperature Dependent ◽  
Low Concentrations ◽  
Nickel Uptake ◽  
High Concentrations ◽  
Uptake Studies ◽  
Cladina Rangiferina ◽  
Very High

Metal uptake studies with Cladina rangiferina showed that the affinity for nickel was much lower than for copper or thallium. Nickel uptake was not decreased by the absence of light or oxygen or by pretreatment with metabolic inhibitors. Nickel uptake was not temperature dependent but was very dependent upon pH.Cation-exchange studies demonstrated that there was a stoichiometric exchange of Ni2+ for Sr2+, and Cu2+ for Sr2+. The exchange of Tl+ for Sr2+ was not stoichiometric, excess Tl+ was accumulated in relation to the Sr2+ released. The ratio of Sr2+:Tl+ exchange increased with increasing Tl+ availability from 1:9 (12.5 μmol Tl+ available/g of lichen) to 1:2 (500 μmol Tl+ available). Acid-treated lichen gave the expected exchange ratio of 1:2. Washing of the thalli with deionized water resulted in the continued loss of Tl+ from acid-treated and live C. rangiferina. Copper and nickel were not released in this manner.Increasing concentrations of copper and thallium produced a corresponding loss of potassium from the thallus. The potassium loss was initiated at low concentrations of copper and thallium whereas very high concentrations of manganese and nickel were required to bring about the same response.

scholarly journals Etude, dans le raisin, de l'activité β-glucosidase

OENO One ◽  
1988 ◽  
Vol 22 (2) ◽  
pp. 125
Author(s):  
C. Biron ◽  
Robert Cordonnier ◽  
Ollivier Glory ◽  
Ziya Günata ◽  
Jean-Claude Sapis
Keyword(s):  
Plant Material ◽  
Grape Berry ◽  
Cabernet Sauvignon ◽  
Mature Fruit ◽  
Glucosidase Activity ◽  
Low Concentrations ◽  
High Concentrations ◽  
Grape Leaf ◽  
Method Of Extraction ◽  
Very High

<p style="text-align: justify;">Dans ce travail, on étudie l'activité β-glucosidase du raisin. Une méthode d'extraction de l'enzyme à partir du matériel végétal a été mise au point et optimisée. L'activité enzymatique est mesurée spectrophotométriquement avec le paranitrophénylglucopyranoside comme substrat. Dans la baie de raisin, la β-glucosidase est concentrée dans les parties solides, pellicule et pulpe. Dans le jus, elle est en faible quantité. Dans la feuille de vigne, l'activité est élevée dans le limbe, faible dans le pétiole. Au cours de la maturation du raisin l'activité β-glucosidase augmente jusqu'à la maturité. Au-delà, jusqu'au stade de surmaturation, elle reste constante. Dans les raisins mars, la β-glucosidase est présente dans toutes les variétés étudiées, aussi bien dans les variétés aromatiques (Muscat d'Alexandrie, Muscat de Frontignan, Muscat de Hambourg) que dans celles non aromatiques (Carignan, Grenache, Cinsaut, Baroque, Cabernet-Sauvignon, Syrah, Merlot). Pour un millésime donné, l'activité β-glucosidase varie selon la variété. Les activités les plus élevées ont été rencontrées dans les Muscats, le Carignan, la Syrah et le Merlot. Elles sont environ 2,8 fois plus élevées que les activités les plus faibles. Pour une variété donnée, les niveaux d'activité varient fréquemment selon le millésime.</p><p style="text-align: justify;">+++</p><p style="text-align: justify;">β-glucosidase activity in grape was studied. A method of extraction of the enzyme from plant material was optimized and glucosidase activity measured spectrophotometrically using paranitrophenylglucopyranoside as substrate. High concentrations of β-glucosidase were found in grape berry solids (skin and pulp) and low concentrations in the juice. This distribution is similar to that of free terpenols in the same parts of the berry. The β-glucosidase content were very high in grape leaf blades and low in stems. Activity of the enzyme increased during maturation of the fruit. It was found in mature fruit of both aromatic (Muscat of Alexandria, Muscat of Frontignan, Muscat of Hamburg) and non-aromatic (Carignane, Grenache, Cinsaut, Baroque, Cabernet-Sauvignon, Sirah, Merlot) varieties. β-glucosidase activity varied according to variety for a given vintage. The highest activities (approximately 2.8 times higher than the lowest observed) were found in the differents Muscats and also in non-aromatic varieties such as Sirah, Merlot and Carignane. β-glucosidase activity in a given variety was frequently found to vary considerably from one vintage to another.</p>

Fibrinolytic Activity of Thrombin Preparations

1964 ◽  
Vol 11 (01) ◽  
pp. 234-242 ◽  
Author(s):  
Pieter Brakman ◽  
Panpit Klug ◽  
Tage Astrup
Keyword(s):  
Protease Activity ◽  
Fibrinolytic Activity ◽  
The Other ◽  
Fibrinolytic Agents ◽  
Fibrinolytic Agent ◽  
Low Concentrations ◽  
Fibrin Plate ◽  
Simple Chemical ◽  
Per Se ◽  
High Concentrations

SummarySome thrombin samples have a slight unspecific protease activity probably caused by contaminating plasmin. All investigated samples were fibrinolytically active. This activity was caused by an activator of plasminogen. Fibrinolytic activity was apparently produced by two components of the thrombin preparations. One of these components was a contaminant with fibrinolytic activity but with no thrombin activity. This component could be separated from the thrombin by simple chemical procedures. The other fibrinolytic component appeared to be the thrombin molecule per se. It was not fibrinolytically active when used in the low concentrations required for clotting of fibrinogen, but in high concentrations, assayed on the fibrin plate, it activated plasminogen. In the accurate assay of fibrinolytic agents it is necessary to use preparations of thrombin from which the contaminating fibrinolytic agent has been removed.

Transport and exchange diffusion of l-tryptophan in Ehrlich cells

1961 ◽  
Vol 200 (5) ◽  
pp. 1063-1068 ◽  
Author(s):  
John A. Jacquez
Keyword(s):  
Amino Acid ◽  
Initial Velocity ◽  
The Other ◽  
Preliminary Loading ◽  
Exchange Diffusion ◽  
Diaminobutyric Acid ◽  
Low Concentrations ◽  
Ehrlich Ascites ◽  
Ehrlich Ascites Cells ◽  
High Concentrations

The initial velocity of uptake of l-tryptophan by Ehrlich ascites cells can be explained as the sum of two processes: diffusion and an active transport that shows a saturation effect. Azaserine, l-2,4 diaminobutyric acid, l-histidine, and l-leucine, at low concentrations, increase the initial velocity of uptake of l-tryptophan but compete with l-tryptophan at high concentrations. Preliminary loading of the cells with glycine decreases the initial tryptophan flux: preliminary loading of the ascites cells with azaserine or tryptophan markedly increases the initial flux of uptake of the other amino acid.

PATTERNS OF PLASMA PROLACTIN IN POST-PARTUM SUCKLED COWS

1981 ◽  
Vol 90 (3) ◽  
pp. 391-396 ◽  
Author(s):  
R. WEBB ◽  
G. E. LAMMING
Keyword(s):  
Post Partum ◽  
Significant Negative Correlation ◽  
Prolactin Secretion ◽  
The Other ◽  
Plasma Prolactin ◽  
Blood Samples ◽  
Biphasic Pattern ◽  
Stage Of Lactation ◽  
Low Concentrations ◽  
High Concentrations

Blood samples taken on alternate days through indwelling jugular venous catheters from 12 suckled cows between days 14 and 48 post partum contained significantly less prolactin than samples collected on intermediate days by jugular venepuncture. Samples taken through the catheter every 2 h for 72 h periods revealed a repetitive daily biphasic pattern of prolactin secretion with low concentrations at 09.00 and 19.00 h and high concentrations at 13.00 and 23.00 h. In two groups of cows, one group calving at the beginning of March (increasing photoperiod) and the other calving during June (decreasing photoperiod), there was a significant negative correlation between stage of lactation and plasma prolactin concentrations in samples taken by venepuncture.

Mitotic blocking agents for suspension cultures of maize 'Black Mexican Sweet' cell lines

Genome ◽  
1989 ◽  
Vol 32 (3) ◽  
pp. 475-478 ◽  
Author(s):  
J. Stadler ◽  
R. Phillips ◽  
M. Leonard
Keyword(s):  
Mitotic Index ◽  
Culture Medium ◽  
Colchicine Treatment ◽  
Mitotic Arrest ◽  
Suspension Cultures ◽  
Metaphase Arrest ◽  
Low Concentrations ◽  
High Concentrations ◽  
Very High ◽  
Black Mexican Sweet

Good metaphase arrest (25% mitotic index) in maize (Zea mays L.) 'Black Mexican Sweet' suspension cultures can be obtained with colchicine treatment alone, but only if very high concentrations (0.5%; 12.5 mM) are used. This colchicine concentration is 5- to 10-fold greater than that required for optimum mitotic arrest in cell cultures of other plant species. In contrast, we report that the herbicide amiprophos methyl (APM) is a much more efficient metaphase inhibitor for 'Black Mexican Sweet' suspension cultures than colchicine. Low concentrations (50 μm) of APM applied for 21–28 h produce a similar 25% mitotic index, and the growth-inhibiting effects of this treatment are undetectable 24 h after the removal of APM from the culture medium, APM, therefore, may be a useful agent for mitotic arrest in experiments which require survival of the treated cells. Another antitubulin herbicide, trifuralin, also was tested for ability to promote metaphase arrest in 'Black Mexican Sweet' cultures, but it proved to be ineffective.Key words: mitotic arrest, colchicine, phosphoric amide herbicide.

Yeast actin with a subdomain 4 mutation (A204C) exhibits increased pointed-end critical concentration

2007 ◽  
Vol 85 (3) ◽  
pp. 319-325 ◽  
Author(s):  
David J. Teal ◽  
John F. Dawson
Keyword(s):  
Actin Polymerization ◽  
Critical Concentration ◽  
Structural Studies ◽  
Wild Type ◽  
Low Concentrations ◽  
Engineering Strategy ◽  
High Concentrations ◽  
Pointed End ◽  
Very High

Characterizing mutants of actin that do not polymerize will advance our understanding of the mechanism of actin polymerization and will be invaluable for the production of short F-actin structures for structural studies. To circumvent the problem of expressing dominant lethal nonpolymerizing actin in yeast, we adopted a cysteine engineering strategy. Here we report the characterization of a mutant of yeast actin, AC-actin, possessing a single pointed-end mutation, A204C. Expression of this mutant in yeast results in actin-polymerization-deficient phenotypes. When copolymerized with wild-type actin, ATP–AC-actin is incorporated into filaments. ADP–AC-actin participates in the nucleation and elongation of wild-type filaments only at very high concentrations. At low concentrations, ADP–AC-actin appears to participate only in the nucleation of wild-type filaments, suggesting that Ala-204 is involved in modulating the critical concentration of the pointed end of actin.

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