Metal biology: aspects of beneficial effects

Do natural spring waters in Australia and New Zealand affect health? A systematic review

Therapeutic use of spring waters has a recorded history dating back to at least 1550 BC and includes both bathing in and drinking such waters for their healing properties. In Australia and New Zealand the use of therapeutic spring waters is a much more recent phenomenon, becoming a source of health tourism from the late 1800s. We conducted a systematic review aimed at determining the potential health outcomes relating to exposure to Australian or New Zealand natural spring water. We found only low-level evidence of adverse health outcomes relating to this spring water exposure, including fatalities from hydrogen sulphide poisoning, drowning and primary amoebic meningoencephalitis. We found no studies that investigated the therapeutic use of these waters, compared with similar treatment with other types of water. From the broader literature, recommendations have been made, including fencing potentially harmful spring water, and having signage and media messages to highlight the potential harms from spring water exposure and how to mitigate the risks (e.g. not putting your head under water from geothermal springs). Sound research into the potential health benefits of Australian and New Zealand spring waters could provide an evidence base for the growing wellness tourism industry.

Specific anion effects in Artemia salina

The specific anion effect on the vitality of Artemia salina was investigated by measuring the Lethal Time LT50 of the crustaceans in the presence of different sodium salts solutions at room temperature and at the same ionic strength as natural seawater. Fluoride, thiocyanate and perchlorate are the most toxic agents, while chloride, bromide and sulfate are well tolerated. The rates of oxygen consumption of brine shrimps were recorded in mixed NaCl+NaF or NaCl+NaSCN solutions as a function of time. The results are discussed in terms of the Hofmeister series, and suggest that, besides the biochemical processes that involve F(-), SCN(-) and ClO4(-), the different physico-chemical properties of the strong kosmotropic and chaotropic anions may contribute in determining their strong toxicity for A. salina.

Electrostatic effects on proton coupled electron transfer in oxomanganese complexes inspired by the oxygen-evolving complex of photosystem II

The influence of electrostatic interactions on the free energy of proton coupled electron transfer in biomimetic oxomanganese complexes inspired by the oxygen-evolving complex (OEC) of photosystem II (PSII) are investigated. The reported study introduces an enhanced multiconformer continuum electrostatics (MCCE) model, parametrized at the density functional theory (DFT) level with a classical valence model for the oxomanganese core. The calculated pKa's and oxidation midpoint potentials (E(m)'s) match experimental values for eight complexes, indicating that purely electrostatic contributions account for most of the observed couplings between deprotonation and oxidation state transitions. We focus on pKa's of terminal water ligands in [Mn(II/III)(H2O)6](2+/3+) (1), [Mn(III)(P)(H2O)2](3-) (2, P = 5,10,15,20-tetrakis(2,6-dichloro-3-sulfonatophenyl)porphyrinato), [Mn2(IV,IV)(μ-O)2(terpy)2(H2O)2](4+) (3, terpy = 2,2':6',2″-terpyridine), and [Mn3(IV,IV,IV)(μ-O)4(phen)4(H2O)2](4+) (4, phen = 1,10-phenanthroline) and the pKa's of μ-oxo bridges and Mn E(m)'s in [Mn2(μ-O)2(bpy)4] (5, bpy = 2,2'-bipyridyl), [Mn2(μ-O)2(salpn)2] (6, salpn = N,N'-bis(salicylidene)-1,3-propanediamine), [Mn2(μ-O)2(3,5-di(Cl)-salpn)2] (7), and [Mn2(μ-O)2(3,5-di(NO2)-salpn)2] (8). The analysis of complexes 6-8 highlights the strong coupling between electron and proton transfers, with any Mn oxidation lowering the pKa of an oxo bridge by 10.5 ± 0.9 pH units. The model also accounts for changes in the E(m)'s by ligand substituents, such as found in complexes 6-8, due to the electron withdrawing Cl (7) and NO2 (8). The reported study provides the foundation for analysis of electrostatic effects in other oxomanganese complexes and metalloenzymes, where proton coupled electron transfer plays a fundamental role in redox-leveling mechanisms.

Soil cadmium enrichment: Allocation and plant physiological manifestations

Cadmium (Cd) in soil is enriched through several leaky management agricultural practices and natural resources. Cd enriched soil is inevitable cause of nutritional stress besides Cd induced toxicity symptoms and physiological malfunctions. Redox signals shift toward oxidative stress which accelerates cellular damage and elicits defense mechanism at the cost of growth. Plants get enriched with this toxic, abundant and undesirable element through 'mineral uptake system' non-specifically. Different components and pathways have been marked cooperating in cellular sequestration and systemic localization of Cd, escaped from avoidance and efflux. Cd induced metabolic alteration led to electron leakage as ROS, reduced photosynthesis and carbon fixation. Compromised primary metabolism negatively feedbacks the plant growth, result into loss of potential crop yield.