Search results for "Sodium"

Salt effects on the protonation of l-histidine and l-aspartic acid: a complex formation model

1991

Abstract Protonation constants of l -histidine (histidinate: his − ) and l -aspartic acid (aspartate: asp 2− ) were determined potentiometrically, using the (H + ) glass electrode, in aqueous tetraethylammonium iodide (Et 4 NI), calcium chloride and sodium chloride solutions, at 0 −3 and 10 ⩽, T ⩽, 45 ° C. Differences in protonation constants determined in different salt media were explained by a complex formation model and, according to this model, the presence of the following species was hypothesized: Ca(his) + , CaH(his) 2+ , CaH 2 (his) 3+ Na(his) 0 , H 3 (his)X + , H 2 (his)X 0 , Et 4 N(his) 0 , Et 4 NH(his) + , Ca(asp) 0 , CaH(asp) + , CaH 2 (asp) 2+ , Na(asp) − , NaH(asp) 0 , H 3 (a…

Computer simulations of undercooled fluids and the glass transition

2000

Abstract Two model studies are presented that attempt to describe the static and dynamic properties of glass-forming fluids via molecular dynamics simulations: The first model is an atomistically realistic model of SiO 2 , the second model provides a coarse-grained description of polymer liquids, i.e., typical `fragile' glassformers, while SiO 2 is the prototype of a `strong glassformer'. For both models, attention is given to the questions as to which range of temperatures are properties in equilibrium, and whether such simulations can help to interpret experiments and/or check theoretical predictions. While in the simulation of SiO 2 using the potential of van Beest, Kramer and van Santen…

Determination of albendazole and ivermectin residues in cattle and poultry-derived samples from India by micellar liquid chromatography

2021

We have developed a method, based on micellar liquid chromatography, to determine albendazole and ivermectin in dairy products and biological waste from bovine, as well as edible tissues from poultry. Anthelmitics were resolved in less than 10 min using a C18 column and a mobile phase of 0.15 mol/L sodium dodecyl sulfate – 6% 1-pentanol at buffered at pH 7 with a 0.01 M phosphate salt, running under isocratic mode at 1 mL/min. Detection was by absorbance at 292 nm. Method was successfully validated following official validation guidelines, in terms of: selectivity, sensitivity, calibration range (0.0125−0.5 mg/kg to 25−50 mg/kg), linearity (r2 > 9990), trueness (86.3–105.6%), precision (<12…

Influence of negative allosteric cooperativity in cation transport.

1992

Abstract The bis-macrocyclic ether5 seems to have a negative allosteric cooperativity and is able to transport double the amount of Na+ and K+ cations as monocyclic systems. This compound could be used as a simple model of the plasma membrane Na+−K+ ATPase which actively pumps Na+ out and K+ into the cell, respectively.

In vivo digestibility and nutritive value of Atriplex halimus alone and mixed with wheat straw

2002

In vivo digestibility trials were carried out using six young rams fed with Atriplex halimus biomass harvested in summer (A) and in early autumn (B), and with a mixture of mid-autumn Atriplex halimus and wheat straw (5[ratio ]1 ratio on fresh matter basis) (C). Atriplex halimus had a high protein content (139·0, 135·9 and 193·4 g/kg DM in A, B and C respectively), but was rich in sodium chloride, especially in summer (145·9 g/kg DM), limiting its use as feed. The summer forage had a higher organic matter (OM) digestibility coefficient than the autumn forage (0·663 v. 0·530) but lower digestible OM intake (16·8 v. 29·4 g/day per kg BW0·75). In autumn forage, the combination with straw did no…

A giant hybrid organic-inorganic octahedron from a narrow rim carboxylate calixarene.

2020

Here we discovered an unprecedented giant octahedral coordination compound bearing 16 Zn2+, 12 Na+, 8 O2-, 4 OH-, 13 H2O and 6 L4- ligands [L4- = fully deprotonated tetra(carboxymethoxy)calix[4]arene]. Its structure was elucidated by single-crystal X-ray diffraction, wavelength-dispersive X-ray spectroscopy and MALDI-TOF mass spectrometry. This compound, Zn8Na6L6⊃Zn8Na6O8(OH)4(H2O)13 (external⊃internal), has eight tetrahedral zinc ions forming the coordination vertices of an outermost cube where carboxylate groups from the sodium calixarenes are anchored. Its core consists of eight Zn2+, six Na+, eight O2-, and four OH- distributed over three layers, besides thirteen coordinated H2O molecul…

1981

1983

To obtain a carrier polymer for pharmacologically active components, linear polyethyleneimine (LPEI) was chemically modified by reactions with acrylic acid (1a), acrylamide (1b), acrylic acid esters (1c and 1d), sodium chloroacetate, and hydrochloric acid. All product polymers 2a – 2e are soluble in water. Among these, 2a and 2e, β- and α-amino acid derivatives, respectively, show no acute toxicity in mice up to dosages of 1 g/kg i. v. Similar types of polymers 5a and 5b and a polymer containing phosphonic acid moieties (5d) derived from branched polyethyleneimine (BPEI) were prepared. 5a and 5b are also nontoxic regardless of the molecular weight of four kinds of BPEI and of the wide range…

Enantioselective addition of sodium bisulfite to nitroalkenes. A convenient approach to chiral sulfonic acids

2021

An enantioselective organocatalytic addition of sodium bisulfite to (E)-nitroalkenes has been developed by using a chiral bifunctional organocatalyst. The present methodology provides a variety of chiral β-nitroethanesulfonic acid compounds (17 examples) with excellent results: up to 99% yield and excellent enantioselectivity (up to 96% ee). The reaction tolerates (hetero)aryl and alkyl substituents on the β-nitroalkenes, and β,β-disubstituted nitroalkenes.

Umsetzung von amino-aziminen mit basen

1980

Abstract Amino-azimines of type (1) react at room temperature with bases (ammonia, aliphatic amines, hydrazine and methyl-hydrazine, aqueous/ethanolic sodium hydroxide) by cleavage of the to the and the NNN moieties (azide).