Cyclic dinucleotides (CDNs) are widely used secondary signaling molecules in bacterial and mammalian cells. The family of CDNs includes c-di-GMP, c-di-AMP and two distinct versions of hybrid cGAMPs. Studies related to these CDNs require large doses that are relatively expensive to generate by current methods. Here we report what to our knowledge is the first feasible microbial-based method to prepare these CDNs including c-di-GMP, 3′3′-cGAMP and 2′3′-cGAMP. The method mainly includes two parts: producing high yield of CDNs by engineering the overexpression of the proper dinucleotide cyclases (DNCs) and other related proteins in Escherichia coli, and purifying the bacteria-produced CDNs by a unified and simple process involving a STING affinity column, macroporous adsorption resin and C18 reverse-phase liquid chromatography. After purification, we obtained the diammonium salts of c-di-GMP, 3′3′-cGAMP and 2′3′-cGAMP with weight purity of >99, >96, >99% and in yields of >68, >26, and >82 milligrams per liter of culture, respectively. This technological platform enables the production of CDNs from cheaper material, provides a sustainable source of CDNs for scientific investigation, and can easily be further developed to prepare CDNs on a large scale for industry.

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Turbulence modulation by finite-size particles in homogeneous isotropic turbulence (HIT) has been investigated numerically and experimentally in many studies, but its controlling parameters are not fully clear. In this work, four non-dimensional parameters governing the turbulent modulation by non-settling particles, i.e. $Re_\lambda$ of the background HIT, the particle-to-fluid density ratio $\rho _p/\rho _f$ , the relative particle size $d_p/\eta$ and the particle volume fraction $\phi _v$ , are identified through dimensional analysis. Then, a parameterization study is conducted based on results from fully resolved direct numerical simulations to investigate the influence of the above non-dimensional parameters on the modulation of turbulent kinetic energy (TKE) and viscous dissipation rate. Empirical models that quantitatively predict the modulation of TKE and dissipation rate are then developed by fitting in the simulation results. These models are used to examine the turbulence modulation results reported in the literature. The model predictions and the data points of TKE modulation show reasonable agreement, but the model predicting the modulation of dissipation rate needs further deliberation as the credibility of the available data points is currently difficult to assess. The generality and the physics behind these empirical models also require further investigation.

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We developed an enantioselective organocascade Michael/Henry reaction in the presence of a bifunctional organocatalyst to construct chiral polyfunctionalized 3,4-dihydro-2H-thiopyrano[2,3-b]quinolines. The resulting optically active products with three contiguous stereocenters, one quaternary and two tertiary, were obtained in moderate to good yields and with good to excellent enantioselectivities. Remarkably, the resulting products were readily converted into polyfunctionalized optically active furo[2′,3′:4,5]thiopyrano[2,3-b]quinoline, 3,4-dihydro-2H-thiopyrano[2,3-b]quinoline 1-oxide and 2,3-dihydro-4H-thiopyrano[2,3-b]quinolin-4-one derivatives.