Nanometer arrays of functional light harvesting antenna complexes by nanoimprint lithography and host-guest interactions

We show an approach based on a combination of site-directed mutagenesis, NIL and multivalent host-guest interactions for the realization of engineered ordered functional arrays of purified components of the photosynthetic system, the membrane-bound LH2 complex. In addition to micrometer-scale patterned structures, we demonstrated the use of nanometer-scale hard NIL stamps to generate functional protein arrays approaching molecular dimensions.     

Uranium(IV) polyoxotungstophosphates

Two tris(oxouranium)-substituted Keggin and Dawson sandwich-type tungstophosphate heteropolyanions Na₁₂[(UO)₃(H₂O)₆(PW₉O₃₄)₂]·21 H₂O (1) and Na₁₈[(UO)₃(H₂O)₆(P₂W₁₅O₅₆)₂]·27 H₂O (2) have been prepared by reaction of uranium sulphate with [PW₉O₃₄]⁹⁻ and [P₂W₁₅O₅₆]¹²⁻, respectively, in aqueous media at 4.7 pH. The products were characterized by elemental and thermal analyses, IR, UV-Vis spectroscopy and magnetical susceptibility. The results of these studies suggest that the compounds obtained from Keggin and Dawson trilacunary anions are 2∶3 sandwich-type complexes and both exhibit a square antiprismatic stereochemistry for uranium(IV) with retention of polyoxometallate parent structure.     

Gas‐phase fragmentation reactions of protonated benzofuran‐ and dihydrobenzofuran‐type neolignans investigated by accurate‐mass electrospray ionization tandem mass spectrometry

We have investigated gas‐phase fragmentation reactions of protonated benzofuran neolignans (BNs) and dihydrobenzofuran neolignans (DBNs) by accurate‐mass electrospray ionization tandem and multiple‐stage (MSⁿ) mass spectrometry combined with thermochemical data estimated by Computational Chemistry. Most of the protonated compounds fragment into product ions B ([M + H–MeOH]⁺), C ([ B –MeOH]⁺), D ([ C –CO]⁺), and E ([ D –CO]⁺) upon collision‐induced dissociation (CID). However, we identified a series of diagnostic ions and associated them with specific structural features. In the case of compounds displaying an acetoxy group at C‐4, product ion C produces diagnostic ions K ([ C –C₂H₂O]⁺), L ([ K –CO]⁺), and P ([ L –CO]⁺). Formation of product ions H ([ D –H₂O]⁺) and M ([ H –CO]⁺) is associated with the hydroxyl group at C‐3 and C‐3′, whereas product ions N ([ D –MeOH]⁺) and O ([ N –MeOH]⁺) indicate a methoxyl group at the same positions. Finally, product ions F ([ A –C₂H₂O]⁺), Q ([ A –C₃H₆O₂]⁺), I ([ A –C₆H₆O]⁺), and J ([ I –MeOH]⁺) for DBNs and product ion G ([ B –C₂H₂O]⁺) for BNs diagnose a saturated bond between C‐7′ and C‐8′. We used these structure‐fragmentation relationships in combination with deuterium exchange experiments, MSⁿ data, and Computational Chemistry to elucidate the gas‐phase fragmentation pathways of these compounds. These results could help to elucidate DBN and BN metabolites in in vivo and in vitro studies on the basis of electrospray ionization ESI‐CID‐MS/MS data only.     

Synthesis of New Highly Functionalized 1H-Indole-2-carbonitriles via Cross-Coupling Reactions

An approach for the preparation of polysubstituted indole-2-carbonitriles through a cross-coupling reaction of compounds 1-(but-2-ynyl)-1H-indole-2-carbonitriles and 1-benzyl-3-iodo-1H-indole-2-carbonitriles is described. The reactivity of indole derivatives with iodine at position 3 was studied using cross-coupling reactions. The Sonogashira, Suzuki–Miyaura, Stille and Heck cross-couplings afforded a variety of di-, tri- and tetra-substituted indole-2-carbonitriles.     

Effect of Elevated Carbon Dioxide Exposure on Nutrition-Health Properties of Micro-Tom Tomatoes

(1) Background: The anthropogenically induced rise in atmospheric carbon dioxide (CO₂) and associated climate change are considered a potential threat to human nutrition. Indeed, an elevated CO₂ concentration was associated with significant alterations in macronutrient and micronutrient content in various dietary crops. (2) Method: In order to explore the impact of elevated CO₂ on the nutritional-health properties of tomato, we used the dwarf tomato variety Micro-Tom plant model. Micro-Toms were grown in culture chambers under 400 ppm (ambient) or 900 ppm (elevated) carbon dioxide. Macronutrients, carotenoids, and mineral contents were analyzed. Biological anti-oxidant and anti-inflammatory bioactivities were assessed in vitro on activated macrophages. (3) Results: Micro-Tom exposure to 900 ppm carbon dioxide was associated with an increased carbohydrate content whereas protein, minerals, and total carotenoids content were decreased. These modifications of composition were associated with an altered bioactivity profile. Indeed, antioxidant anti-inflammatory potential were altered by 900 ppm CO₂ exposure. (4) Conclusions: Taken together, our results suggest that (i) the Micro-Tom is a laboratory model of interest to study elevated CO₂ effects on crops and (ii) exposure to 900 ppm CO₂ led to the decrease of nutritional potential and an increase of health beneficial properties of tomatoes for human health.     

Controlling the fluorescence quantum yields of benzothiazole-difluoroborates by optimal substitution

Precise tuning of the fluorescence quantum yield, vital for countless applications of fluorophores, remains exceptionally challenging due to numerous factors affecting energy dissipation phenomena often leading to its counterintuitive behavior. In contrast to the absorption and emission wavelength which can be precisely shifted to the desired range by simple structural changes, no general strategy exists for controllable modification of the fluorescence quantum yield. The rigidification of the molecular skeleton is known to usually enhance the emission and can be practically realized via the limiting molecular vibrations by aggregation. However, the subtle balance between the abundant possible radiative and non-radiative decay pathways makes the final picture exceptionally sophisticated. In the present study, a series of nine fluorophores obtained by peripheral substitution with two relatively mild electron donating and electron withdrawing groups are reported. The obtained fluorescence quantum yields range from dark to ultra-bright and the extreme values are obtained for the isomeric molecules. These severe changes in emission efficiency have been shown to arise from the complex relationship between the Franck–Condon excited state and conical intersection position. The experimental findings are rationalized by the advanced quantum chemical calculations delivering good correlation between the measured emission parameters and theoretical radiative and internal conversion rate constants. Therefore, the described substituent exchange provides a method to rigorously adjust the properties of molecular probes structurally similar to thioflavin T.

A full palette of FQY (form ca. 0 to 98%) was covered by exchanging two groups in a series of nine compounds. The darkest (OMe/CF₃) and brightest (CF₃/OMe) are isomers. All experimental data are supported by TD-DFT calculations.     

Understanding dispersity control in photo-atom transfer radical polymerization: Effect of degree of polymerization and kinetic evaluation

In photo-atom transfer radical polymerization (ATRP), dispersity can be efficiently controlled by varying the deactivator concentration. In this work, we provide mechanistic insight into dispersity-controlled photo-ATRP by conducting detailed kinetics under a range of conditions. For the lower dispersity polymers, a conventional first-order kinetic profile was observed accompanied by a linear evolution of number average molecular weight (M_n) with conversion while the reactions reached moderate to high conversions (between 66% and 93%). Whereas, when polymers of high dispersity were targeted, the M_n remained relatively constant throughout the polymerization and the reactions ceased at less than 50% of conversion. In particular, for Р= 1.84, a significant deviation between theoretical and experimental molecular weights was evident. This deviation was unambiguously attributed to slow initiation as indicated by ¹H NMR, where significant percentages of unreacted initiator were observed. Importantly, the addition of ligand at the polymerization plateau re-initiated the polymerization and led to the complete consumption of the unreacted initiator, thus enabling the synthesis of one-pot diblock copolymers. We subsequently evaluated the effect of the degree of polymerization (DP) on the obtained dispersity when a constant catalyst ratio was maintained. Based on the interpolation of those experiments results, we could predict experimental conditions for any desirable DPs and dispersities.     

Targeting an Interaction Between Two Disordered Domains by Using a Designed Peptide

Intrinsically disordered regions in proteins (IDRs) mediate many disease-related protein–protein interactions. However, the unfolded character and continuous conformational changes of IDRs make them difficult to target for therapeutic purposes. Here, we show that a designed peptide based on the disordered p53 linker domain can be used to target a partner IDR from the anti-apoptotic iASPP protein, promoting apoptosis of cancer cells. The p53 linker forms a hairpin-like structure with its two termini in close proximity. We designed a peptide derived from the disordered termini without the hairpin, designated as p53 LinkTer. The LinkTer peptide binds the disordered RT loop of iASPP with the same affinity as the parent p53 linker peptide, and inhibits the p53–iASPP interaction in vitro. The LinkTer peptide shows increased stability to proteolysis, penetrates cancer cells, causes nuclei shrinkage, and compromises the viability of cells. We conclude that a designed peptide comprising only the IDR from a peptide sequence can serve as an improved inhibitor since it binds its target protein without the need for pre-folding, paving the way for therapeutic targeting of IDRs.     

Bacteria‐Resistant Single Chain Cyclized/Knotted Polymer Coatings

Further to conventional linear, branched, crosslinked, and dendritic polymers, single chain cyclized/knotted polymers (SCKPs) have emerged as a new class of polymer structure with unique properties. Herein, the development of bacteria‐resistant SCKPs is reported and the effect of this structure on the resistance of polymer materials to bacteria is investigated. Four SCKPs were synthesized by reversible addition fragmentation chain transfer (RAFT) homopolymerization of multivinyl monomers (MVMs) and then crosslinked by UV light to form SCKP films. Regardless of MVM type used, the resulting SCKP films showed much higher resistance to bacteria, and up to 75 % less bacterial attachment and biofilm formation, in comparison with the corresponding non‐SCKP films. This is due to the altered surface morphology and hydrophobicity of the SCKP films. These results highlight the critical role of the SCKP structure in enhancing the resistance of polymeric materials to bacteria.     

Tuning Dispersity by Photoinduced Atom Transfer Radical Polymerisation: Monomodal Distributions with ppm Copper Concentration

Dispersity significantly affects the properties of polymers. However, current methods for controlling the polymer dispersity are limited to bimodal molecular weight distributions, adulterated polymer chains, or low end‐group fidelity and rely on feeding reagents, flow‐based, or multicomponent systems. To overcome these limitations, we report a simple batch system whereby photoinduced atom transfer radical polymerisation is exploited as a convenient and versatile technique to control dispersity of both homopolymers and block copolymers. By varying the concentration of the copper complex, a wide range of monomodal molecular weight distributions can be obtained (?=1.05–1.75). In all cases, high end‐group fidelity was confirmed by MALDI‐ToF‐MS and exemplified by efficient block copolymer formation (monomodal, ?=1.1–1.5). Importantly, our approach utilises ppm levels of copper (as low as 4 ppm), can be tolerant to oxygen and exhibits perfect temporal control, representing a major step forward in tuning polymer dispersity for various applications.