Dataset on the spatial distribution of groundwater quality for pH, Electrical Conductivity (EC), Total Hardness (TH), Ca2+, Mg2+, HCO3-, F-, and NO3- in Dodoma, Singida, and Tabora regions located in central Tanzania.

Groundwater is an important source of water for drinking and irrigation purposes in semi-arid regions like central Tanzania. Groundwater quality is degraded by anthropogenic and geogenic pollution. Anthropogenic pollution depends on the disposal of contaminants from human activities into the environment, which can leach and pollute groundwater. Geogenic pollution depends on the presence and dissolution of mineral rocks. High geogenic pollution is observed in aquifers that are rich in carbonates, feldspars, and mineral rocks. Consumption of polluted groundwater has negative health effects. Therefore, protection of public health necessitates the evaluation of groundwater in order to identify a general pattern and spatial distribution of groundwater pollution. A literature search uncovered no publications that describe the spatial distribution of hydrochemical parameters across central Tanzania. Central Tanzania is located within East Africa Rift Valley, Tanzania craton and is made up of Dodoma, Singida and Tabora regions. To fill the gap, this article contains a data set for pH, Electrical Conductivity (EC), Total Hardness (TH), Ca2+, Mg2+, HCO3-, F-, and NO3- from 64 groundwater samples collected from Dodoma region (22 samples), Singida region (22 samples) and Tabora region (20 samples). Data collection covered a total distance of 1344 km, which was divided into east-west along B129, B6, and B143 roads and north-south along A104, B141, and B6 roads. The present dataset can be used to model the geochemistry and spatial variation of physiochemical parameters across these three regions.

Anhydrous Monoalkylguanidines in Aprotic and Nonpolar Solvents: Models for Deprotonated Arginine Side Chains in Membrane Environments.

In this study, the synthesis of crystalline dodecylguanidine free base and its spectroscopic characterization in nonpolar environments are described. IR as well as 1H and 15N NMR spectra of the free base dissolved in aprotic solvents are substantially different from the previously reported spectra of arginine, or other monoalkylguanidinium compounds, at high hydroxide concentrations. The current results provide improved modeling for the spectroscopic signals that would be expected from a deprotonated arginine in a nonpolar environment. On the basis of our spectra of the authentic dodecylguanidine free base, addition of large amounts of aqueous hydroxide to arginine or other monoalklyguanidinium salts does not deprotonate them. Instead, hydroxide addition leads to the formation of a guanidinium hydroxide complex, with a dissociation constant near ∼500 mM that accounts for the established arginine pK value of ∼13.7. We also report a method for synthesizing a compound containing both phenol and free-base guanidine groups, linked by a dodecyl chain that should be generalizable to other hydrocarbon linkers. Such alkyl-guanidine and phenolyl-alkyl-guanidine compounds can serve as small-molecule models for the conserved arginine-tyrosine groupings that have been observed in crystallographic structures of both microbial rhodopsins and G-protein-coupled receptors.

Experimental and Computational Modeling of H-Bonded Arginine-Tyrosine Groupings in Aprotic Environments.

H-bonds between neutral tyrosine and arginine in nonpolar environments are modeled by small-molecule phenol/guanidine complexes. From the temperature and concentration dependence of UV spectra, a value of ΔH° = -74 ± 4 kJ mol-1 is deduced for the formation of H-bonded p-cresol/dodecylguanidine in hexane. ΔE = -71 kJ mol-1 is computed with density functional theory (in vacuo). In dimethyl sulfoxide or crystals, (p-phenolyl)alkylguanidines form head-to-tail homodimers with two strong H-bonding interactions, as evidenced by UV, IR, and NMR spectral shifts, strong IR continuum absorbance bands, and short O···N distances in X-ray crystal structures. Phenol/alkylguanidine H-bonded complexes consist of polarizable rapidly interconverting tautomers, with the proton shift from phenol to guanidine increasing with increase in the polarity of the aprotic solvent. As measured by NMR, both groups in these strongly H-bonded neutral complexes can simultaneously appear to be predominantly protonated. These systems serve as models for the hypothetical hydrogen-Bonded Uncharged (aRginine + tYrosine), or "BU(RY)", motifs in membrane proteins.

Enzymatic detection of γ-hydroxybutyrate using aldo-keto reductase 7A2.

Gamma-hydroxybutyrate (GHB) is a prescribed medication as well as a drug of abuse. Its detection in various matrices for in-field forensic scientists remains a challenge. We have developed an assay that uses aldo-keto reductase 7A2 (AKR7A2) for the specific determination of GHB in various drinks. AKR7A2 was purified using Ni-affinity chromatography. The Michaelis-Menten constant for the GHB oxidation reaction was 10 mM, and the minimum detection limit was 4 mM. Ethanol was not a substrate for AKR7A2. In a coupled reaction with NADP(+), phenazine methosulfate (PMS), and 2,6-dichlorophenolindophenol, various beverages (orange juice, milk, soda, and numerous alcoholic drinks) containing GHB turned from blue to light yellow. In a second coupled reaction where diaphorase replaced PMS, the presence of GHB also caused the expected change of color in various beers.