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The glycan epitopes of natural and synthetic glycoconjugates exist as covalent attachments of well-defined inner structures or scaffolds. Macromolecules such as proteins, peptides, lipids, and saccharides and synthetic structures serve as scaffolds of glycoconjugates. It is generally perceived that the biological activities of glycoconjugates are determined mainly by the attached glycans, while the seemingly inert inner scaffolds play a passive role by providing physical support to the attached glycan epitopes. However, our data show that scaffolds actively influence lectin recognition and can potentially modulate lectin-mediated signaling properties of glycoconjugates. Through in vitro experiments, we found that the scaffolds significantly altered the thermodynamic binding properties of the covalently attached glycan epitopes. When a free glycan was attached to a scaffold, its lectin binding entropy became more positive. The level of positive entropic gain was dependent on the types of scaffolds tested. For example, protein scaffolds of glycoproteins were found to generate more positive entropy of binding than synthetic scaffolds. Certain scaffolds were found to have limiting effects on glycoconjugate affinity. We also found that scaffold-bearing glycans with a similar affinity or an identical valence demonstrated different kinetics of lattice formation with lectins, when the scaffold structures were different. Our data support the view that scaffolds of glycoconjugates (i) help the covalently attached glycans become more spontaneous in lectin binding and (ii) help diversify the lattice forming or cross-linking properties of glycoconjugates. [ABSTRACT FROM AUTHOR]

Reverse intersystem crossing (RISC) is the rate-limited step for the radiative process of thermally activated delayed fluorescence (TADF) materials, which is important to achieve ideal photoluminescence and electroluminescence efficiency. Herein, we propose a new strategy of introducing a lone pair (n) electron with p orbital character to enhance spin-orbit coupling (SOC) for promoting the RISC process. A proof-of-concept TADF molecule with p orbital lone pairs, namely, MoCz-PCN, was developed, and three counterparts without any p lone pairs, namely, DMAc-PCN, DPAc-PCN, and SpiroAc-PCN, were constructed for comparison. The experimental data revealed that MoCz-PCN exhibits a ca. 1.9 times higher RISC rate than the counterparts, which can be ascribed to enhanced SOC. Moreover, a significant increase in external quantum efficiency is observed in the MoCz-PCN-based OLED device. These findings provide a feasible strategy to develop highly efficient TADF emitters by introducing a lone pair (n) electron with p orbital character.

An efficient procedure has been developed for the preparation of tetrasubstituted unsymmetrical 1,4-enediones via copper-promoted autotandem catalysis and air as the oxidant. Various N-nucleophiles are compatible with this reaction, such as morpholine, piperidine, pyrrolidine, arylamines, pyrazole, imidazole, benzimidazole, and benzotriazole. This reaction also has significant advantages in easily available substrates, atom economy, bond-forming efficiency, and environmental benignity.