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Trk/Ktr/HKT transporters probably were evolved from simple K+ channels KcsA. HKT transporters, which mediate Na+-uniport or Na+/K+-symport, maintain K+/Na+ homeostasis and increase salinity tolerance, can be classified into three subfamilies in higher plants. In this review, we systematically analyzed the characteristics of amino acids sequences and physiological functions of HKT transporters in higher plant. Furthermore, we depicted the hypothetical models of cations selection and transportation mediated by HKT transporters according to the highly conserved structure for the goal of better understanding the cations transportation processes. [ABSTRACT FROM AUTHOR]

Trk/Ktr/HKT transporters probably were evolved from simple K+ channels KcsA. HKT transporters, which mediate Na+-uniport or Na+/K+-symport, maintain K+/Na+ homeostasis and increase salinity tolerance, can be classified into three subfamilies in higher plants. In this review, we systematically analyzed the characteristics of amino acids sequences and physiological functions of HKT transporters in higher plant. Furthermore, we depicted the hypothetical models of cations selection and transportation mediated by HKT transporters according to the highly conserved structure for the goal of better understanding the cations transportation processes. [ABSTRACT FROM AUTHOR]

Maintenance of monovalent cation homeostasis (mainly K+ and Na+) is vital for cell survival, and cation toxicity is at the basis of a myriad of relevant phenomena, such as salt stress in crops and diverse human diseases. Full understanding of the importance of monovalent cations in the biology of the cell can only be achieved from a systemic perspective. Translucent is a multinational project developed within the context of the SysMO (System Biology of Microorganisms) initiative and focussed in the study of cation homeostasis using the well-known yeast Saccharomyces cerevisiae as a model. The present review summarize how the combination of biochemical, genetic, genomic and computational approaches has boosted our knowledge in this field, providing the basis for a more comprehensive and coherent vision of the role of monovalent cations in the biology of the cell. [ABSTRACT FROM AUTHOR]

Abstract: Four mRNA variants in pooled cDNA samples of the glassy-winged sharpshooter, Homalodisca coagulata, encoding a putative regulator of cation transporters were identified. RT-PCR showed that the hc-chaC variants were expressed during different stages of insect development and in different tissues and sexes. Structural analysis of the hc-chaC gene indicated that intron and exon sequences of the mRNA variants were identical, and similar to chaC-like genes of other insects. The Hc-ChaC protein (22.5kDa) contained the conserved FGYGSL K+-binding motif near its amino-terminus, and the carboxy-terminal region contained two coiled-coil motifs, which had similarity to the PDZ domain present in well-characterized Na+/H+ exchanger regulatory factors. Our analyses suggest that Hc-ChaC is a regulator of K+ transporters such as K+/H+ antiporters. [Copyright &y& Elsevier]

• Novel zeolite loaded sulfonated polyethersulfone/ polyvinylidene fluoride membrane. • High proton conductivity with low oxygen diffusivity was achieved. • Maximum power density with high COD removal efficiency. • Molecular dynamics simulation study to understand the impact of different cations. • Potassium containing component is more favorable in MFC anolyte solution preparation. A high proton conductivity with low oxygen diffusivity novel composite membrane consisting 15 wt. % zeolite 4A incorporated in 2:1 blend ratio of sulfonated polyethersulfone (SPES) and polyvinylidene fluoride (PVDF) has been synthesized for energy generation through a microbial fuel cell (MFC). The prepared membrane was found to have desired functional groups, with semi-crystalline nature, high thermal stability (490 °C), and uniform morphology. The inclusion of zeolite 4A in SPES/PVDF blend induces a high-water sorption capacity (30 %), proton conductivity (0.141 Scm−1), and ion exchange capacity (1.51 meq g−1) in the composite membrane. A maximum power density of 208 ± 5 mWm-2with high COD (14,000 mg L−1) removal efficiency of 82.1 % along with low oxygen diffusivity of 7.21 × 10-8 cm2s−1 was obtained. Moreover, the impact of different cations (Na+, Ca2+, and K+) on oxygen and hydronium ion (H 3 O+) diffusivity on the composite membrane is investigated using the COMPASS forcefield molecular dynamic (MD) simulations. The results showed that the K+ cation has low oxygen diffusivity (4.50 × 10-8 m2s−1) with high H 3 O+ diffusivity (1.5 × 10-10 m2s−1) as compared to Na+ and Ca2+due to their higher cationic radius with lower electrostatic interactions. This result implies that potassium containing compound is more beneficial for the preparation of MFC solution, as K+ cation shows the desired behavior required for MFC. [ABSTRACT FROM AUTHOR]

Biogeochemical cycling was studied in Sitka spruce [Picea sitchensis(Bong.) Carr.] and western hemlock--Douglas-fir [Tsuga heterophylla (Raf.) Sarg.--Pseudotsuga menziesii (Mirbel) Franco] ecosystems on a chronosequence of five uplifted marine terraces in coastal Oregon. The terraces occur 0.25 to 8.6 km from the Pacific Ocean and range from80 to ~ 500 kyr in age. The soils are highly weathered and include Inceptisols on the youngest terrace and Spodosols with clay-enriched horizons and Ultisols on the older terraces. Bulk precipitation, throughfall, and soil solutions (four depths) were collected monthly from November 1992 through April 1993. The solutions were analyzed for pH,dissolved cations (Na, Mg, Ca, K, Fe, Al, and Si), anions (Cl, SO{sub}4{end}, HCO{sub}3{end}, NO{sub}3{end}, and PO{sub}4{end}), and organic C. Cations (mu mol{sub}c{end} L{sup}-1{end}) in all solutions were ranked: Na greater than Mg greater than Ca greater than K H; anionswere ranked: Cl greater than SO{sub}4{end} greater than NO{sub}3{end} greater than greater than HCO{sub}3{end}. The Na/Cl ratio in all solutions was comparable to that of seawater. The mean sums of cations and anions in all solutions declined sharply with distance from the coast. Throughfall enrichment of all ions suggests that aerosol impaction of sea salts is a dominant process within the coastal fogbelt of Oregon. In that the soils have low inherent fertility, the trees appear to obtain Ca, Mg, K, and S primarily from atmospheric sources. These nutrients are utilized by abundant fine roots in the forest floor and upper 5 to 20 cm of mineral soil. Net cation loss is less than inother areas of the Pacific Northwest and is controlled by organic anions rather than the bicarbonate anion. [ABSTRACT FROM AUTHOR]