Weak NH Research Articles

Interactions of amylose with certain bases

Results of the interaction of NaOH, KOH, Ca(OH) 2, and NH 4OH with amylose, over a temperature range of 283–313 K, using conductometric, viscometric, and equilibrium-dialysis methods, are presented. The specific conductance of the strong bases decreases in the presence of the biopolymer. Examination of the Walden product at a fixed concentration of a base and various concentrations of the polymer revealed binding of the base with the biopolymer. The results followed the Langmuirian isotherm, indicating weak binding, accompanied by a free-energy change of ∼12 kJ/mol. The interaction of amylose and the weak base NH 4OH was conspicuous. The specific conductance showed an increment in the presence of amylose, as well as of d-glucose and poly(ethylene glycol), all of which are polyoxygen-centered non-electrolytes. An increase in the Walden product at a fixed concentration of base and various concentrations of polymer indicated an increase in the degree of dissociation of the weak base over and above its binding with amylose. Evaluation of the degree of dissociation of NH 4OH in the presence of d-glucose and amylose has been attempted.

N-H..S hydrogen bonds

Infrared spectra of some compounds containing weak and medium-strong NH..S hydrogen bonds have been investigated. Spectroscopic and structural data have been correlated and compared with those obtained for NH..O and NH..N systems. At the same strength, the N..S distance is 0.51 and 0.36 Å longer than the corresponding N..O and N..N distances, respectively.

Intracellular calcium release and the mechanisms of parthenogenetic activation of the sea urchin egg

Parthenogenetic activation of Lytechinus pictus eggs can be monitored after injection with the Ca-sensitive photoprotein aequorin to estimate calcium release during activation. Parthenogenetic treatments, including the nonelectrolyte urea, hypertonic sea water, and ionophore A23187, all acted to release Ca 2+ from intracellular stores. Ionophore and urea solutions release Ca 2+ from the same intracellular store as normal fertilization. This intracellular store can be reloaded after 40 min and discharged again. Hypertonic medium appears to release Ca 2+ from a different intracellular store. Treatment with the weak base NH 4Cl did not release intracellular Ca 2+ but did result in a momentary Ca 2+ influx if Ca 2+ was present in the external solution. Ca 2+ influx was not required for ammonia activation.

Uptake of phosphorus from sediment by aquatic plants, Myriophyllum spicatum and Hydrilla verticillata

Eurasian water milfoil( Myriophyllum spicatum L.) and hydrilla ( Hydrilla verticillata Royle) took up most or all of their P from the hydrosoil (sediment) when the water contained 0.015 μg P ml −1 Myriophyllum continued to utilize largely hydrosoil-P with 0.5 μg P ml −1 in the water; however, when 2.0 μg P ml -1 was present in the water, the uptake of hydrosoil-P decreased and the of uptake of water-P increased. Stems of Myriophyllum cut off 2 cm above the crown transferred only 4–20 μg P/plant of hydrosoil-P into the water in the first 18 h after decapitation; thereafter, no further P release occurred. A harvesting operation would thus result in the direct transfer of only a small amount of hydrosoil-P into the water; however, the organically bound-P removed in the harvested Eurasian water milfoil plants would be derived largely from the hydrosoil, not the water body. The procedure would not be effective in reducing the P content of the lake unless its P content was higher than 0.5 μg ml −1. The specific activity of the P taken up by hydrilla was similar to that of the water extracted from the hydrosoil. It differed greatly from the specific activity of the P adsorbed on the sediment that was extracted from the hydrosoil by a weak NH 4FHCI extract. This adsorbed-P fraction, believed to be important in non-aquatic soils, was not supplying the P to the solution feeding the aquatic plant roots or was not in equilibrium with the hydrosoil solution-P.

Ammonia release experiments in the high atmosphere and dissociation processes in comets

The mechanism of formation of radicals and ions observed in comets (CN, C 2, NH 2, CO +, N 2 +, CO 2 +) is one of the major problems of cometaryphysics. Photodissociation and photoionization have been proposed as sources of these species. Two releases of ammonia at an altitude of 180 km have been carried through in July 1964 by ESRO in order to test the relevance of such experiments for the photodecomposition hypothesis. NH 3 absorption in the range λ2250 to λ1500 Å yields the radical NH 2, which has resonance bands in the yellow-red. The released masses of about 42 kg appeared in the twilight sky as diffuse rings expanding with a velocity of 0.5 to 0.8 km/sec, and decresed rapidly in brightness. The configuration remained visible for only 20 seconds and a spectrum of the expanding mass of material obtained between 12 and 20 seconds after the beginning of the release showed only the twilight continuum with no trace of any NH 2 bands. An upper limit on the concentration of NH 2 within the cloud was determined from the brightness of the sky background. The low upper limit so derived points to a space lifetme of the NH 3 molecules of at least 10 3.5 to 10 4 seconds. Stimulated by the release experiments, a study has been made of the space lifetimes of the precursor particles of the radicals and ions in cometary atmospheres. It seems highly probable that the lifetimes of these precursors at solar distance of 1 a.u. are <10 3 seconds, a result incompatible with the photodissociation hypothesis. It shows further that the production rate of CO + ions is orders of magnitude too fast to be explained by a photoionization mechanism. The radicals and ions have the same local source close to the nucleus, a volume with a radius of only a few hundred kilometers. Outbursts of radicals and ions happen simultaneously. Bredohl observed the same releases and those repeated in 1966. Although the results are perhaps not absolutely convincing, he may have detected a weak NH 2 emission on an intense continuous background. Such an observation does not contradict the conclusions drawn above.

Infrared Absorption Spectra and Polymeric Structures of Three s-Triazine Herbicides and Their Metabolites

Abstract The infrared spectra of three 2-chloro- 4,6-bis (alkylamino) s-triazincs and their metabolites in solid (KBr) phase are described, and the characteristic infrared absorption frequencies are given. These compounds may -exist as dimers in the solid state when hydrogen bonding occurs through one or both of the amino groups. In addition, the metabolic products, 2-hydroxy derivatives, may also exist as dimers by hydrogen bonding of the enol (OH) to the keto tautomers in equilibrium. Evidently the weak NH hydrogen bonding of the cis cyclic lactam dimer is partially depolymerized when the compound is ground in an adequate amount of Nujol, and the equilibrium shifts to yield the dimer resulting from strong hydrogen bonding of the enol (OH) to the keto form of the tautomers