| 3. |
- Beal, Jacob, et al.
(författare)
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Robust estimation of bacterial cell count from optical density
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data.
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| 4. |
- Castillo, Ivan, et al.
(författare)
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Structural, spectroscopic, and electrochemical properties of tri- and tetradentate N-3 and N3S copper complexes with mixed benzimidazole/thioether donors
- 2012
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9234 .- 1477-9226. ; 41:31, s. 9394-9404
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Tidskriftsartikel (refereegranskat)abstract
- Cupric and cuprous complexes of bis(2-methylbenzimidazolyl)(2-methylthiophene) amine (L-1), bis(2-methylbenzimidazolyl)benzylamine (L-2), bis(2-methylbenzimidazolyl)(2,4-dimethylphenylthioethyl)-amine (L-3), bis(1-methyl-2-methylbenzimidazolyl)benzylamine (Me2L2), and bis(1-methyl-2-methylbenzimidazolyl)(2,4-dimethylphenylthioethyl)amine (Me2L3) have been spectroscopically, structurally, and electrochemically characterised. The thioether-containing ligands L-3 and Me2L3 give rise to complexes with Cu-S bonds in solution and in the solid state, as evidenced by UV-vis spectroscopy and X-ray crystallography. The Cu2+ complexes [(LCuCl2)-Cu-1] (1), [(LCuCl2)-Cu-2] (2) and [(Me2LCuCl)-Cu-3]ClO4 (3(Me,ClO4)) are monomeric in solution according to ESI mass spectrometry data, as well as in the solid state. Their Cu+ analogues [(LCu)-Cu-1]ClO4, [(LCu)-Cu-2]ClO4, [(LCu)-Cu-3]ClO4 (4-6), [(BOC2LCu)-Cu-1(NCCH3)]ClO4 (4(BOC)), [(Me2LCu)-Cu-2(NCCH3)(2)]PF6 (5(Me)) and [(Me2LCu)-Cu-3](2)(ClO4)(2) (6(Me)) are also monomeric in acetonitrile solution, as confirmed crystallographically for 4(BOC) and 5(Me). In contrast, 6(Me) is dimeric in the solid state, with the thioether group of one of the ligands bound to a symmetry-related Cu+ ion. Cyclic voltammetry studies revealed that the bis(2-methylbenzimidazolyl) amine-Cu2+/Cu+ systems possess half-wave potentials in the range -0.16 to -0.08 V (referenced to the ferrocenium-ferrocene couple); these values are nearly 0.23 V less negative than those reported for related bis(picolyl) amine-derived ligands. Based on these observations, the N-3 or N3S donor set of the benzimidazole-derived ligands is analogous to previously reported chelating systems, but the electronic environment they provide is unique, and may have relevance to histidine and methionine-containing metalloenzymes. This is also reflected in the reactivity of [(Me2LCu)-Cu-2(NCCH3)(2)](+) (5(Me)) and [(Me2LCu)-Cu-3](+) (6(Me)) towards dioxygen, which results in the production of the superoxide anion in both cases. The thioether-bound Cu+ centre in 6(Me) appears to be more selective in the generation of O-2(center dot-) than 5(Me), lending evidence to the hypothesis of the modulating properties of thioether ligands in Cu-O-2 reactions.
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