Effects of ammonium sulfate and sodium chloride concentration on PEG/protein liquid-liquid phase separation

When added to protein solutions, poly(ethylene glycol) (PEG) creates an effective attraction between protein molecules due to depletion forces. This effect has been widely used to crystallize proteins, and PEG is among the most successful crystallization agents in current use. However, PEG is almost always used in combination with a salt at either low or relatively high concentrations. Here the effects of sodium chloride and ammonium sulfate concentration on PEG 8000/ovalbumin liquid-liquid (L-L) phase separation are investigated. At low salt the L-L phase separation occurs at decreasing protein concentration with increasing salt concentration, presumably due to repulsive electrostatic interactions between proteins. At high salt concentration, the behavior depends on the nature of the salt. Sodium chloride has little effect on the L-L phase separation, but ammonium sulfate decreases the protein concentration at which the L-L phase separation occurs. This trend is attributed to the effects of critical fluctuations on depletion forces. The implications of these results for designing solution conditions optimal for protein crystallization are discussed.     

Diastereoselective aziridination of chiral electron-deficient olefins with N-chloro-N-sodiocarbamates catalyzed by chiral quaternary ammonium salts

Chiral quaternary ammonium salt-catalyzed diastereoselective aziridination of electron-deficient olefins that possess a chiral auxiliary with N-chloro-N-sodiocarbamates was developed. The key to high stereoselectivity was found to be the employment of the "matching" stereochemical combination of chiral auxiliary/ammonium salt. For example, when 3-phenyl-(4R,7S)-4-methyl-7-isopropyl-4,5,6,7-tetrahydroindazole (L-menthopyrazole) as a chiral auxiliary and a cinchonidine-derived chiral ammonium salt as a catalyst were applied to the reaction system, perfect diastereoselectivity was realized. Furthermore, the preparation of enantiomerically pure aziridines by removal of the chiral auxiliary was demonstrated.     

Decylammonium chloride/ammonium chloride aqueous solutions A Raman scattering study

Aqueous solutions of decylammonium chloride and decylammonium chloride/ammonium chloride between 20 and 50 per cent of DACl have been studied by Raman scattering. The spectral behaviour was followed as a function of temperature and phase transitions were observed for all samples. We have focused our study on the intensity variations of both the symmetric and the antisymmetric stretching vibration modes of CH₂ groups situated in the region 2800-3000cm^-1. The study of the high frequency part of the spectrum showed the characteristics of order disorder transitions already studied for other materials. We have observed that the existence of a nematic phase in the ternary systems is caused by the addition of the salt.     

Solute induced liquid crystalline behaviour of a quaternary ammonium salt and its application to structure determination

A new liquid crystalline phase, induced by the addition of small amounts of a non-mesogenic solute (such as dimethyl sulphoxide or methyl iodide) to a quaternary ammonium salt, N -methyl- N, N, N-trioctadecylammonium iodide (MTAI), has been detected by NMR and optical microscopic studies. In some cases, there is a coexistence of nematic and smectic phases. Information on the ordering of the phases in the magnetic field of the spectrometer has been derived from NMR spectra of a dissolved molecule, 13C-enriched methyl iodide. The low order parameter of the pure thermotropic nematic phase of the salt provides firstorder spectra of the dissolved oriented molecules. Analyses of spectra of cis , cis -mucononitrile exemplifies the utility of the MTAI nematic phase in the determination of structural parameters of the solute.     

Phase stabilization of ammonium nitrate by double addition of potassium nitrate and melamine

Methods for providing stabilization of ammonium nitrate and expanding the application field of this oxidizing agent in gas-generating compositions used for various purposes were sought for. The results of a study of the physicochemical properties of ammonium nitrate with a melamine–potassium nitrate double additive introduced by mechanical mixing and crystallization from an aqueous (nonaqueous) solution at the boiling point are presented. The phase diagrams of the ammonium nitrate–melamine and ammonium nitrate–melamine–potassium nitrate systems, based on the results of a differential-thermal analysis, demonstrated that a phase-stable ammonium nitrate can be formed by using the method of crystallization from an aqueous (nonaqueous) solution at the boiling point. The resulting samples were examined by IR spectroscopy and X-ray diffraction analysis, and a conclusion was made that a new thermodynamically stable phase can be formed in the system with individual additives, and the introduction of a double additive leads to a combined effect: a thermodynamically stable crystal structure is formed, with the simultaneous slowing down of the nucleation and growth of a new phase in the course of a phase transformation.     

Solid/Liquid phase diagram of the ammonium sulfate/maleic acid/water system

We have studied the low temperature phase diagram and water activities of the ammonium sulfate/maleic acid/water system using differential scanning calorimetry and infrared spectroscopy of thin films. Using the results from our experiments, we have mapped the solid/liquid ternary phase diagram, determined the water activities based on the freezing point depression, and determined the ice/maleic acid phase boundary as well as the ternary eutectic composition and temperature. We also compare our results to the predictions of the extended AIM aerosol thermodynamics model and find good agreement for the ice melting points in the ice primary phase field of this system; however significant differences were found with respect to phase boundaries, maleic acid dissolution, and ammonium sulfate dissolution.     

Thermolysis of ammonium nitrate/potential donor of active chlorine compositions

The thermal stability of the ammonium nitrate (AN)/sodium salt of 1,3-dichlor-2,4,6-trioxo-1,3,5-triazacyclohexane (DC) composition has been studied. The factors of influence on the rates of reactions in the composition, namely, a water content, composition wetting methods, a dispersion of composition components, sample mass values, have been examined. The water presence in the composition reduces its thermal stability. The mechanism includes the partial dissociation of AN to HNO₃ and NH₃ and the hydrolysis of DC with the formation of some unstable Cl-containing compounds (chloramines, nitrogen chloride). The reaction of ammonium cation with active chlorine has been found to give rise to the explosion of the AN/DC composition. Such a situation is typical for other ammonium salt/DC compositions.     

Na2CrO4-(NH4)2CrO4-H2O体系的相图

铬盐工业是无机盐工业的一个主要分支,其主要产品有重铬酸钠、铬酸酐、铬酸铵、氧化铬等,广泛用于合金材料、电镀、制革、印染、橡胶等部门,是国民经济中重要的基础化工原料工业．铬盐生产系先将铬铁矿制成铬酸钠及重铬酸钠,然后再进一步加工制成其它铬盐产品．在铬盐...     

新型二茂铁甲基季铵盐离子液体的合成与表征

以二茂铁与二甲胺为原料合成了碘化二茂铁甲基季铵盐,再经复分解反应得到乙酸二茂铁甲基季铵盐离子液体;表征了离子液体的结构,测定了其熔点和溶解性.结果表明,合成的乙酸二茂铁甲基季铵盐离子化合物熔点低于100℃,是一种新型的二茂铁甲基季铵盐离子液体.     

Spectrophotometric determination of some penicillins with ammonium vanadate

A spectrophotometric method for determining some penicillins has been developed. A known volume of the penicillin solution-in phosphate buffer of pH 6.8 is boiled with ammonium vanadate solution-in sulphuric acid medium-for 10 min and the absorbance of the colour formed is measured at 750 nm. The excess of vanadate can also be determined volumetrically. The method has been successfully applied for the determination of penicillin G sodium, phenoxymethyl penicillin, ampicillin sodium, phenethicillin potassium, cloxacillin sodium and methicillin sodium. The procedure is also used for analysing some pharmaceutical preparations of these drugs, e.g., injections. The results obtained are in agreement with those of the B P 1973 methods.     

IRMPD spectra of Gly.NH4 + and proton-bound betaine dimer: evidence for the smallest gas phase zwitterionic structures

Zwitterionic structures exist extensively in biological systems and the electric field resulting from zwitterion formation is the driving force for determination of the properties, function and activity of biological molecules, such as amino acids, peptides and proteins. It is of considerable interest and import to investigate the stabilization of zwitterionic structures in the gas phase. Infrared multiple photon dissociation (IRMPD) spectroscopy is a very powerful and sensitive technique, which may elucidate clearly the structures of both ions and ionic clusters in the gas phase, since it provides IR vibrational fingerprint information. The structures of the clusters of glycine and ammonium ion and of the betaine proton-bound homodimer have been investigated using IRMPD spectroscopy, in combination with electronic structure calculations. The experimental and calculated results indicate that zwitterionic structure of glycine may be effectively stabilized by an ammonium ion. This is the smallest zwitterionic structure of an amino acid to be demonstrated in the gas phase. On the basis of the experimental IRMPD and calculated results, it is very clear that a zwitterionic structure exists in the proton-bound betaine dimer. The proton is bound to one of the carboxylate oxygens of betaine, rather than being equally shared. Investigations of zwitterionic structures in the isolated state are essential for an understanding of the intrinsic characteristics of zwitterions and salt bridge interactions in biological systems.     

Phase-transfer-catalyzed free-radical polymerization: Kinetics of polymerization of methyl methacrylate using ammonium peroxydisulfate/hexadecyl pyridinium chloride in ethyl acetate/water

The kinetics of phase-transfer-catalyzed free-radical polymerization of methyl methacrylate using the system ammonium peroxydisulfate/hexadecyl pyridinium chloride have been investigated in the temperature range of 50–60°C in ethyl acetate/water two-phase systems. The superior efficiency of the phase-transfer-catalyzed reaction in comparison with polymerization initiated by oil soluble initiators such as 2,2′-azobisisobutyronitrile and benzoylperoxide has been demonstrated. Rate of polymerization increased with increase in concentration of the quaternary salt but showed a tendency to level off at higher concentrations. Increase in the peroxydisulfate concentration also resulted in an increase in the rate at lower concentrations, but was found to decrease at higher concentrations. The order with respect to the monomer was found to be approximately unity. The title reaction has been found to be not truly phase-transfer catalyzed in character as claimed by previous workers. A suitable kinetic scheme has been proposed to account for the experimental data and its significance discussed.     

季铵盐在油田化学品中的研究进展

介绍了季铵盐分子的特性(安全低毒、性能稳定、水溶性强)以及合成工艺,综述了季铵盐分子近年来在缓蚀剂、杀菌剂、页岩抑制剂以及有机改性剂方面的研究进展,以及作用机理.对于同一类处理剂的优缺点,季铵盐分子易生物降解、作用效果强使其使其广泛地应用于油田化学品中并符合钻井、完井、采油环保以及抗高温要求.结合上述四种油田化学处理剂...     

Condensation of ammonium ion with acetone

Recrystallization of ammonium anthranilate or ammonium salicylate from acetone-hexane results in conversion of the ammonium salts to diacetoneammonium salts. The reaction is general for the ammonium salts of amino- and hydroxy-substituted benzoic acids, all of which are converted at least in part to diacetoneammonium salts when treated with acetone. Under similar conditions ammonium benzoate is converted to the triacetoneammonium salt. These reactions constitute convenient laboratory procedures for the preparation of diacetoneammonium and triacetoneammonium salts, and explain the frequent incursion of diacetoneamine and triacetoneamine as artifacts when natural systems are extracted with acetone.     

Infrared studies of the ferroelectric transition in ammonium sulphate

The pressure and temperature dependence of the symmetric stretching vibration band, ν1, of the the sulphate ion in ammonium sulphate (rendered weakly infrared active by the crystal field) was investigated. The sudden increase in intensity at the transition temperature has been found to be accompanied by an equally sharp shift in frequency. A pressure-temperature phase diagram for the ferroelectric phase transition of ammonium sulphate has been obtained. The contributions to the transition mechanism made by the order-disorder change for the NH⁺₄ orientations, the strengthening of the hydrogen bond and the distortion of the SO⁼₄ ions are discussed.     

Raman scattering study of diglycine sulphate and ammonium sulphate double salt crystals

Raman spectra have been recorded for diglycine sulphate and ammonium sulphate double salt crystals (DGSAS) at room temperature. From a comparison between our results and the i.r. and Raman spectra of the amino acids and ammonium sulphate crystals, the functional groups have been ascribed to particular positions of the bands in the Raman spectra of DGSAS crystals.     

Photopolymerization of vinyl monomers with quaternary ammonium salts

Photopolymerization of vinyl monomers with a series of quaternary ammonium salts has been investigated. However, quaternary ammonium salts used are not photosensitizers but rather photoinitiators. The salts photoinitiation activity was observed to vary widely with the counteranion in quaternary salts used and also with the alkyl group in their amine components. In general, the halide salts were more effective than tetrafluoroborate salts. It was also found that the overall activation energy for the photopolymerization of methyl methacrylate with dimethylbenzylanilinium tetrafluoroborate was 5.9 kcal/mole, and its rate was proportional to the 0.32 and 1.0 order of the concentration of the salt and the monomer used, respectively. An endgroup similar to dimethylaniline was found to be present in the methyl methacrylate polymer obtained by above system; this is probably a methylanilinomethyl group, from the characteristics of its ultraviolet spectrum.     

Investigation of diterpenoid isosteviol ammonium derivatives by matrix-assisted laser desorption/ionization mass spectrometry

Matrix-assisted laser desorption/ionization (MALDI) mass spectra of diterpenoid isosteviol ammonium derivatives have been analyzed. The compounds were synthesized as antibacterial agents. It has been found that peaks of salt cations were detected in positive ion MALDI mass spectra of mono-quaternary derivatives. The fragmentation of bis-quaternary salts depended on the distance between the ammonium centers. Clusters containing dication and acidic matrix anion have been observed for compounds with two quaternized nitrogen atoms connected by a nonanomethylene or a longer spacer. Similar clusters did not form for compounds containing pentamethylene or a shorter spacer between two quaternized nitrogen atoms.     

Synthesis and application of novel carbohydrate-based ammonium and triazolium salts

The synthesis of nine new carbohydrate-based quaternary ammonium salts and two new triazolium salts starting from d-glucose has been accomplished. Our synthesis utilized the regio- and stereoselective ring opening reaction of 2,3-anhydro sugars by nucleophilic reagents to afford the key intermediates. In these new types of phase transfer catalysts, the ammonium and triazolium functions are directly attached to the carbohydrate scaffold in different positions (2-, 3-, 6-positions of the sugar). The efficiency of the altrose- and glucose-based quaternary salts were tested in the alkylation of N-(diphenyl) methylene glycine tert-butyl ester with benzyl bromide. To our knowledge this is the first example when sugar-based quaternary ammonium or triazolium salts were used successfully as phase transfer catalysts. The enantiomeric recognition ability of the synthesized salts towards racemic Mosher’s acid silver salt was also investigated by ¹⁹F NMR spectroscopy.     

Phase diagrams and water activities of aqueous ammonium salts of malonic acid

Malonic acid has been observed in the free troposphere and as a component of tropospheric aerosol, among other dicarboxylic acids. These aerosols can uptake ammonia, which partially or completely neutralizes the acids. Therefore, the impact of ammoniated dicarboxylic acids on the phases that can exist in aerosols at atmospheric temperatures needs investigation. To that end, the low temperature, solid/liquid phase diagrams of ammonium hydrogen malonate/water, ammonium malonate/water, and triammonium hydrogen malonate/water have been investigated with differential scanning calorimetry and infrared spectroscopy of thin films. Results show that the order of increasing solubility is triammonium hydrogen malonate, ammonium hydrogen malonate, malonic acid, and ammonium malonate. We have also determined a hydrate may form in the ammonium malonate system and decompose below 240 K. We report water activities at the ice melting points for each system up to the respective eutectic concentrations, and find for a given mole fraction of water, increasing ammonium content leads to decreasing water activity coefficients.