143 research outputs found
It Takes Two to Tango, Part II : Synthesis of A-Ring Functionalised Quinones Containing Two Redox-Active Centres with Antitumour Activities
In 2021, our research group published the prominent anticancer activity achieved through
the successful combination of two redox centres (ortho-quinone/para-quinone or quinone/seleniumcontaining triazole) through a copper-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The
combination of two naphthoquinoidal substrates towards a synergetic product was indicated, but
not fully explored. Herein, we report the synthesis of 15 new quinone-based derivatives prepared
from click chemistry reactions and their subsequent evaluation against nine cancer cell lines and
the murine fibroblast line L929. Our strategy was based on the modification of the A-ring of paranaphthoquinones and subsequent conjugation with different ortho-quinoidal moieties. As anticipated,
our study identified several compounds with IC50 values below 0.5 ”M in tumour cell lines. Some
of the compounds described here also exhibited an excellent selectivity index and low cytotoxicity
on L929, the control cell line. The antitumour evaluation of the compounds separately and in their
conjugated form proved that the activity is strongly enhanced in the derivatives containing two
redox centres. Thus, our study confirms the efficiency of using A-ring functionalized para-quinones
coupled with ortho-quinones to obtain a diverse range of two redox centre compounds with potential
applications against cancer cell lines. Here as well, it literally takes two for an efficient tango
Fractionation of cellulose nanocrystals : enhancing liquid crystal ordering without promoting gelation
Colloids of electrically charged nanorods can spontaneously develop a fluid yet ordered liquid crystal phase, but this ordering competes with a tendency to form a gel of percolating rods. The threshold for ordering is reduced by increasing the rod aspect ratio, but the percolation threshold is also reduced with this change; hence, prediction of the outcome is nontrivial. Here, we show that by establishing the phase behavior of suspensions of cellulose nanocrystals (CNCs) fractionated according to length, an increased aspect ratio can strongly favor liquid crystallinity without necessarily influencing gelation. Gelation is instead triggered by increasing the counterion concentration until the CNCs lose colloidal stability, triggering linear aggregation, which promotes percolation regardless of the original rod aspect ratio. Our results shine new light on the competition between liquid crystal formation and gelation in nanoparticle suspensions and provide a path for enhanced control of CNC self-organization for applications in photonic crystal paper or advanced composites
Intentional creation of carbon-rich dark earth soils in the Amazon.
Fertile soil known as Amazonian dark earth is central to the debate over the size and ecological impact of ancient human populations in the Amazon. Dark earth is typically associated with human occupation, but it is uncertain whether it was created intentionally. Dark earth may also be a substantial carbon sink, but its spatial extent and carbon inventory are unknown. We demonstrate spatial and compositional similarities between ancient and modern dark earth and document modern Indigenous practices that enrich soil, which we use to propose a model for the formation of ancient dark earth. This comparison suggests that ancient Amazonians managed soil to improve fertility and increase crop productivity. These practices also sequestered and stored carbon in the soil for centuries, and we show that some ancient sites contain as much carbon as the above-ground rainforest biomass. Our results demonstrate the intentional creation of dark earth and highlight the value of Indigenous knowledge for sustainable rainforest management
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