| 1. |
- 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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| 2. |
- Fan, Yanmiao, et al.
(författare)
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Detection of gemcitabine metabolism using 19F-NMR and its impacts on E. coli morphology
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- 19F-NMR spectroscopy is a sensitive analytical method to detect the metabolism of fluorine-containing drugs by bacteria. In this study, 19F-NMR was used to achieve the real time detection of metabolic process of gemcitabine (2′, 2′-difluorodeoxycytidine) by Escherichia Coli (E. coli) in the nutrient broth. Both E. coli and Staphylococcus aureus (S. aureus) were used in the metabolism study. E. coli can metabolize gemcitabine, while gemcitabine cannot be metabolized by S. aureus. Our results showed that gemcitabine can be totally metabolized to its inactive form 2′, 2′-difluorodeoxyuridine (dFdU) by E. coli both in Mueller-Hinton broth and M9 minimal salt. The metabolic rate of gemcitabine has a positive correlation with the bacterial concentrations. The metabolism is due to the presence of bacterial cytidine deaminase, and the enzyme inhibitor tetrahydrouridine (THU) can inhibit the gemcitabine metabolism. Scanning electron microscope (SEM) was used to study the effects of gemcitabine metabolism on E. coli morphological changes, and the treated E. coli was 2-3 times longer than the normal bacteria. 19F–NMR was capable to achieve real time detection of gemcitabine metabolism process considering there was no need to separate the bacterial cells from the nutrient medium, this study provided a fast and facile way to detect fluorine-containing drug metabolism by bacteria.
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| 3. |
- Hu, Lei, et al.
(författare)
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Chirality Control in Enzyme-Catalyzed Dynamic Kinetic Resolution of 1,3-Oxathiolanes
- 2015
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Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 80:16, s. 8478-8481
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Tidskriftsartikel (refereegranskat)abstract
- The origin of enantioenrichment in enzyme-catalyzed dynamic kinetic resolution of 1,3-oxathiolane derivatives, key intermediates for asymmetric lamivudine synthesis, was elucidated. The chirality control could be determined by chiral HPLC and NOE NMR spectroscopy using a modified 1,3-oxathiolane compound obtained through enzyme-catalyzed selective hydrolysis. Solvent-dependent stereoselectivity was observed under biphasic conditions using different organic solvents with phosphate buffer.
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| 4. |
- Ren, Yansong, et al.
(författare)
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A Multicontrolled Enamine Configurational Switch Undergoing Dynamic Constitutional Exchange
- 2018
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 57:21, s. 6256-6260
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Tidskriftsartikel (refereegranskat)abstract
- A multiresponsive enamine-based molecular switch is presented, in which forward/backward configurational rotation around the C=C bond could be precisely controlled by the addition of an acid/base or metal ions. Fluorescence turn-on/off effects and large Stokes shifts were observed while regulating the switching process with CuII. The enamine functionality furthermore enabled double dynamic regimes, in which configurational switching could operate in conjunction with constitutional enamine exchange of the rotor part. This behavior was used to construct a prototypical dynamic covalent switch system through enamine exchange with primary amines. The dynamic exchange process could be readily turned on/off by regulating the switch status with pH.
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| 5. |
- REN, Yansong, et al.
(författare)
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Configurational and Constitutional Dynamics in Enamine Molecular Switches
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Dual configurational and constitutional dynamics in systems based on enamine molecularswitches has been systematically studied. pH-responsive moieties, such as 2-pyridyl and 2-quinolinyl units, were required on the “stator” part, also providing enamine stability throughintramolecular hydrogen-bonding (IMHB) effects. Upon protonation or deprotonation, forward andbackward switching could be rapidly achieved. Extension of the stator π-system in the 2-quinolinylderivative provided a higher E-isomeric equilibrium ratio under neutral conditions, pointing to ameans to achieve quantitative forward/backward isomerization processes. The ‘rotor’ part of theenamine switches exhibited constitutional exchange ability with primary amines. Interestingly,considerably higher exchange rates were observed with amines containing ester groups, indicatingpotential stabilization of the transition state trough IMHB. Acids, particularly BiIII, were found toefficiently catalyze the constitutional dynamic processes. In contrast, the enamine and the formeddynamic enamine system showed excellent stability under basic conditions. This coupledconfigurational and constitutional dynamics expand the scope of dynamic C-C and C-N bonds, andpotentiates further studies and applications in the fields of molecular machinery and systemschemistry.
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| 6. |
- Ren, Yansong, 1988-, et al.
(författare)
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Configurational and Constitutional Dynamics of Enamine Molecular Switches
- 2020
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 26:67, s. 15654-15663
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Tidskriftsartikel (refereegranskat)abstract
- Dual configurational and constitutional dynamics in systems based on enamine molecular switches has been systematically studied. pH-responsive moieties, such as 2-pyridyl and 2-quinolinyl units, were required on the „stator“ part, also providing enamine stability through intramolecular hydrogen-bonding (IMHB) effects. Upon protonation or deprotonation, forward and backward switching could be rapidly achieved. Extension of the stator π-system in the 2-quinolinyl derivative provided a higher E-isomeric equilibrium ratio under neutral conditions, pointing to a means to achieve quantitative forward/backward isomerization processes. The „rotor“ part of the enamine switches exhibited constitutional exchange ability with primary amines. Interestingly, considerably higher exchange rates were observed with amines containing ester groups, indicating potential stabilization of the transition state through IMHB. Acids, particularly BiIII, were found to efficiently catalyze the constitutional dynamic processes. In contrast, the enamine and the formed dynamic enamine system showed excellent stability under basic conditions. This coupled configurational and constitutional dynamics expands the scope of dynamic C−C and C−N bonds and potentiates further studies and applications in the fields of molecular machinery and systems chemistry.
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| 7. |
- REN, Yansong
(författare)
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Dynamic Chemistry for Asymmetric Synthesis, Molecular Motion and Constitutional Exchange
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Living matter is built on complex dynamic systems consisting of numerus biotransformations. By exploiting the adaptive and evolutive behaviors ofmolecular matter, dynamic chemistry has developed as an important tool tounderstand the organization of nonliving matter into complex living systems.This thesis concerns three aspects of dynamic chemistry with a general focus onthe influence of different stimuli on the structures and functions of dynamicsystems.The first section focuses on dynamic kinetic resolution, where enzymes areutilized for asymmetric synthesis of an enantiopure (2R,5R)-1,3-oxathiolane. Byemploying surfactant-treated subtilisin Carlsberg and Candida antarcticalipase B, the absolute configuration of the resulting 1,3-oxathiolane ring couldbe efficiently controlled.The second section addresses the motional dynamics of configurational enamineswitch systems controlled by multiple stimuli. Complete forward and backwardrotation around the enamine C=C bond could be precisely regulated uponaddition of acid/base or metal ions. The enamine switches exhibited specificsensing ability for CuII ions in solution. Moreover, the enamines exhibitedswitchable aggregation-induced emission in the solid state, which could beapplied in the development of sensors as well as fluorescent organogel.Lastly, the enamine switches could readily undergo constitutional exchange withprimary amines under catalytic acidic conditions, resulting in dynamic enaminesystems. However, under basic conditions or in the presence of excessive acid,this process exhibited extremely slow kinetics, leading to an efficient regulationof the exchange process by controlling the switch status with regulation of pHin the system.
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| 8. |
- REN, Yansong, et al.
(författare)
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Multienzymatic Cascade Synthesis of an Enantiopure (2R,5R)-1,3-Oxathiolane Anti-HIV Agent Precursor
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- An enantiopure (2R,5R)-1,3-oxathiolane derivative was obtained using amultienzymatic cascade protocol. By employing a combination of surfactant-treatedsubtilisin Carlsberg and Candida antarctica lipase B, the absolute configuration of theresulting 1,3-oxathiolane ring was efficiently controlled, resulting in an excellentenantiomeric excess (> 99%). This enantiopure 1,3-oxathiolane derivative is a keyprecursor to anti-HIV agents, such as lamivudine, through subsequent N-glycosylation.
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| 9. |
- Ren, Yansong, 1988-, et al.
(författare)
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Multienzymatic cascade synthesis of an enantiopure (2R,5R)-1,3-oxathiolane anti-HIV agent precursor
- 2019
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Ingår i: Molecular Catalysis. - : Elsevier. - 2468-8274 .- 2468-8231. ; 468, s. 52-56
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Tidskriftsartikel (refereegranskat)abstract
- An enantiopure (2R,5R)-1,3-oxathiolane was obtained using a multienzymatic cascade protocol. By employing a combination of surfactant-treated subtilisin Carlsberg and Candida antarctica lipase B, the absolute configuration of the resulting 1,3-oxathiolane ring was efficiently controlled, resulting in an excellent enantiomeric excess (> 99%). This enantiopure 1,3-oxathiolane derivative is a key precursor to anti-HIV agents, such as lamivudine, through subsequent N-glycosylation.
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| 10. |
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