Ammonium transporters

Kleiner, D. (1985) Bacterial ammonium transport. FEMS Microbiol. Rev. 32, 87-100. 

Hildebrand, M. (2005). Cloning and functional characterization of ammonium transporters from the marine diatom Cylindrotheca fusiformis (BaciUariophyceae). J. Phycol. 41, 105-113. doi 10.1111/j. 1529-8817.2005.04108. X. 

SLC42 Rh ammonium transporter (pending) 3 Rh-null regulator... 

SONODA, Y., IKEDA, A., SAIKI, S., VON WIREN, N., YAMAYA, T., YAMAGUCHl, J., Distinct expression and function of three ammonium transporter genes (OsAMTl l-l 3) in rice, Plant Cell Physiol., 2003, 44, 726-734. 

Cao Z, Mo Y, Thiel W (2007) Deprotonation mechanism of NH4-I- in the Escherichia coli ammonium transporter AmtB insight from QM and QM/MM calculations. Angew Chem Int Ed 46 6811... 

Mixed with additives, urea is used in soHd fertilizers of various formulations, eg, urea—ammonium phosphate (UAP), urea—ammonium sulfate (UAS), and urea—phosphate (urea + phosphoric acid). Concentrated solutions of urea and ammonium nitrate (UAN) solutions (80—85 wt%) have a high nitrogen content but low crystallization point, suitable for easy transportation, pipeline distribution, and direct spray appHcation. 

Transportation. Ammonium nitrate is safely transported by rad, road, and water. However, its transportation on U.S. navigable waterways is restricted. Good ventilation must be provided and precautions taken against leakage and contamination. The material must be completely isolated from other cargo and must be kept free of extraneous combustible materials. 

Health and Safety Factors. Malononitrile is usually available as a soHdifted melt in plastic-Hned dmms. Remelting has to be done carefully because spontaneous decomposition can occur at elevated temperatures, particularly above 100°C, in the presence of impurities such as alkaHes, ammonium, and 2inc salts. Melting should be carried out by means of a water bath and only shordy before use. Occupational exposure to malononitrile mainly occurs by inhalation of vapors and absorption through the skin. Malononitrile has a recommended workplace exposure limit of 8 mg/m, an LD q (oral, rats) of 13.9 mg/kg, and is classified as slight irritant (skin irritation, rabbits). Transport classification RID/ADR 61, IMDG-Code 6.1, lATA/ICAO 6.1. 

Hard rock mining of these ore bodies requkes drilling and blasting with ammonium nitrate and dynamite. After blasting, the ore is reduced in size with a drop ball and then loaded on tmcks for transportation to the processing plant. Mica, quartz, and feldspar concentrates are separated, recovered, and sold from the hard rock ore. 

Pipeline systems for transporting anhydrous ammonia that are urea and ammonium nitrate (UAN) and LNG compatible, exist in Europe, Mexico, and the Soviet Union. Export-oriented ammonia producing countries utilize huge ocean-going tankers that contain up to 50,000 t for distribution of ammonia. Co-shipment in refrigerated LNG tankers is usuaky done. 

Biochemically, most quaternary ammonium compounds function as receptor-specific mediators. Because of their hydrophilic nature, small molecule quaternaries caimot penetrate the alkyl region of bdayer membranes and must activate receptors located at the cell surface. Quaternary ammonium compounds also function biochemically as messengers, which are generated at the inner surface of a plasma membrane or in a cytoplasm in response to a signal. They may also be transferred through the membrane by an active transport system. 

Sulfuric acid (H1SO4) and ammonium bisulfate (NH4HSO4) contribute importantly to ambient acid aerosols, particularly in geographic locations where sulfur-rich coal is used for power plant fuel, such as the eastern United States.Studies on animals and human subjects have shown that H2SO4 and NH4HSO4 alter mucociliary transport in a dose-dependent fashion and... 

Phase-transfer catalysis (Section 22.5) Method for increasing the rate of a chemical reaction by transporting an ionic reactant from an aqueous phase where it is solvated and less reactive to an organic phase where it is not solvated and is more reactive. Typically, the reactant is an anion that is carried to the organic phase as its quaternary ammonium salt. 

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