Search Results (3)

The new mineral chenowethite, Mg(H₂O)₆[(UO₂)₂(SO₄)₂(OH)₂]·5H₂O, was found in efflorescence crusts on tunnel walls at the Blue Lizard, Green Lizard and Markey uranium mines in Red Canyon, San Juan County, Utah, USA. The crystals are long, thin blades up to about 0.5 mm long, occurring in irregular sprays and subparallel groups. Chenowethite is pale green yellow. It has white streak, vitreous to silky luster, brittle tenacity, splintery and stepped fracture and two cleavages: {010} perfect and {001} good. It has a hardness (Mohs) of about 2 and is nonfluorescent in both long- and short-wave ultraviolet illumination. The density is 3.05(2) g/cm³. Optically, crystals are biaxial (−) with α = 1.530(2), β = 1.553(2) and γ = 1.565(2) (white light). The 2V is 72(2)° and dispersion is r > v (slight). The optical orientation is X = b, Y = a, Z = c and the mineral exhibits weak pleochroism in shades of pale green yellow: X < Y < Z. The Raman spectrum is consistent with the presence of UO₂²⁺, SO₄²⁻ and OH^–/H₂O. The empirical formula from electron microprobe analysis and arranged in accordance with the structure is (Mg_0.71Fe²⁺_0.09Co_0.05Ni_0.04)_∑0.89(H₂O)₆[(UO₂)₂(SO₄)₂(OH)₂]·[(H₂O)_4.78(NH₄)_0.22]_∑5.00. Chenowethite is orthorhombic, space group Cmcm; the unit-cell parameters are a = 6.951(2), b = 19.053(6), c = 16.372(5) Å, V = 2168.19(7) ų and Z = 4. The crystal structure of chenowethite (R₁ = 0.0396 for 912 I > 2σI reflections) contains [(UO₂)₂(SO₄)₂(OH)₂]²⁻ sheets that are topologically equivalent to those in deliensite, feynmanite, greenlizardite, johannite, meitnerite and plášilite. Full article

Glycosylation, which is catalyzed by UDP-glycosyltransferases (UGTs), is an important biological modification for the structural and functional diversity of ginsenosides. In this study, the promiscuous UGT109A1 from Bacillus subtilis was used to synthesize unnatural ginsenosides from natural ginsenosides. UGT109A1 was heterologously expressed in Escherichia coli and then purified by Ni-NTA affinity chromatography. Ginsenosides Re, Rf, Rh1, and R1 were selected as the substrates to produce the corresponding derivatives by the recombinant UGT109A1. The results showed that UGT109A1 could transfer a glucosyl moiety to C3-OH of ginsenosides Re and R1, and C3-OH and C12-OH of ginsenosides Rf and Rh1, respectively, to produce unnatural ginsenosides 3,20-di-O-β-d-glucopyranosyl-6-O-[α-l-rhamnopyrano-(1→2)-β-d-glucopyranosyl]-dammar-24-ene-3β,6α,12β,20S-tetraol (1), 3,20-di-O-β-d-glucopyranosyl-6-O-[β-d-xylopyranosyl-(1→2)-β-d-glucopyranosyl]-dammar-24-ene-3β,6α,12β,20S-tetraol (6), 3-O-β-d-glucopyranosyl-6-O-[β-d-glucopyranosyl-(1→2)-β-d-glucopyranosyl]-dammar-24-ene-3β,6α,12β,20S-tetraol (3), 3,12-di-O-β-d-glucopyranosyl-6-O-[β-d-glucopyranosyl-(1→2)-β-d-glucopyranosyl]-dammar-24-ene-3β,6α,12β,20S-tetraol (2), 3,6-di-O-β-d-glucopyranosyl-dammar-24-ene-3β,6α,12β,20S-tetraol (5), and 3,6,12-tri-O-β-d-glucopyranosyl-dammar-24-ene-3β,6α,12β,20S-tetraol (4). Among the above products, 1, 2, 3, and 6 are new compounds. The maximal activity of UGT109A1 was achieved at the temperature of 40 °C, in the pH range of 8.0–10.0. The activity of UGT109A1 was considerably enhanced by Mg²⁺, Mn²⁺, and Ca²⁺, but was obviously reduced by Cu²⁺, Co²⁺, and Zn²⁺. The study demonstrated that UGT109A1 was effective in producing a series of unnatural ginsenosides through enzymatic reactions, which could pave a way to generate promising leads for new drug discovery. Full article

Two mononuclear complexes, [Ni(acac)2]·0.5CH₃OH (1) and[Co(acac)₂NO₃]·2H₂O (2) (acac = pentane-2,4-dione), have been synthesized andcharacterized by single crystal X-ray analysis. Complex 1 crystallizes in the monoclinicspace group P21/c with a = 9.295(4), b = 11.450(5), c = 12.974(6) å, V = 1379.1(11) å³,β = 92.854(7), and Z = 4. Complex 2 crystallizes in the triclinic space group P(-1) with a= 8.153(9), b = 9.925(11), c = 10.355(12), V = 746.3(15) å³, α = 70.530(16), β =71.154(15), γ = 80.698(16) and Z = 2. Complex 1 has a one-dimensional chain-likestructure, which is extended by weak hydrogen contacts, while complex 2 shows a three–dimensional network structure. Full article