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- Beal, Jacob, et al.
(author)
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Robust estimation of bacterial cell count from optical density
- 2020
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In: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Journal article (peer-reviewed)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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2. |
- Liu, Xue, et al.
(author)
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Isomorphous Incorporation of Tin Ions into Germanosilicate Framework Assisted by Local Structural Rearrangement
- 2016
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In: ACS Catalysis. - : American Chemical Society (ACS). - 2155-5435. ; 6:12, s. 8420-8431
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Journal article (peer-reviewed)abstract
- The crystalline structure of UTL zeolite experienced an unusual orientated collapse and reconstruction within an extremely narrow time window during the structural stabilization process by nitric acid treatment at elevated temperature. Taking full advantage of this unique structural change, extra-large pore Sn-UTL zeolites were postsynthesized via the reaction between the SnCl4 molecules and the silanols in the hydroxyl nests, which occurred concomitantly with the removal of Ge and/or Si species from the dense layer. The original UTL topology was restored thereafter, leading to a Sn-incorporated analogue. The usage of the most seriously collapsed intermediate structure, which was captured by timing during the precisely controlled acid treatment, was vital for achieving Sn-UTL zeolites with a larger amount of isolated Sn species effectively incorporated. With tetrahedrally coordinated Sn ions in the highly stabilized UTL topology consisting of intersecting 12- and 14-membered ring (MR) pore channels, Sn-UTL showed promising catalytic performance in the Meerwein-Pondorf-Verley reaction as well as in the Baeyer-Villiger oxidation reactions of ketones using H2O2 or even bulky tert-butyl hydroperoxide (TBHP) as an oxidant.
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