Lewis acids are frequently used as catalysts in glycosylation reactions, however these reagents often suffer from significant limitations such as sensitivity to moisture and poor stereocontrol. Chalco...

Asparagine-linked protein glycosylation is among the most frequent modifications of proteins trafficking through the secretory pathway. These glycans are manufactured in an assembly line process to a common precursor that is then subject to individual modifications with different levels of complexity. An important biosynthetic modulator is the incorporation of N-acetylglucosamine (GlcNAc) at distinct positions in N-linked glycan biosynthesis, commencing with the activity of the glycosyltransferase MGAT1. While mapping of N-glycans to their corresponding protein attachment sites is generally possible, not much is known about the glycoprotein substrate choice for MGAT1 and related transferases. Analogs of GlcNAc with small bioorthogonal tags can be incorporated into N-glycans. However, due to the promiscuity of some GlcNAc transferases, incorporation is of little specificity towards individual positions. Here, we report an iterative bump-and-hole approach in the design of a bioorthogonal precision tool for the activity of MGAT1 in mammalian cells. Structure-informed protein engineering abrogated the activity of MGAT1 towards the nucleotide-sugar UDP-GlcNAc while retaining activity towards bumped, azide-modified analogs. Kinetic and computational analyses using a neural network approach informed the synthesis of a tailored UDP-GlcNAc analog with preferential acceptance by the engineered enzyme. Following substrate biosynthesis, the strategy allowed selective incorporation of a chemical tag on MGAT1 substrate proteins in living mammalian cells with little background incorporation by other GlcNAc transferases. Our work expands the toolbox for glycan-based reporter compounds. ### Competing Interest Statement C.R.B. is a co-founder and scientific advisory board member of GanNA Bio, Neuravid, Firefly Bio, Lycia Therapeutics, Palleon Pharmaceuticals, Enable Bioscience, Redwood Biosciences (a subsidiary of Catalent), OliLux Bio, Grace Science and InterVenn Biosciences. C.R.B. is a member of the Board of Directors of Alnylam, Xaira Therapeutics, Acepodia and OmniAb. Wellcome Trust, https://ror.org/029chgv08, CC2127, 312750/Z/24/Z Cancer Research UK, https://ror.org/054225q67, CC2127, DRCMDP-Nov22/100011 Medical Research Council, https://ror.org/03x94j517, CC2127 UK Research and Innovation, https://ror.org/001aqnf71, EP/X042383/1, EP/Y032527/1, MR/V02213X/1, UKRI2014 Howard Hughes Medical Institute, https://ror.org/006w34k90, CC31920 Children's Tumor Foundation

Thioflavin T (ThT) is a well-established fluorescence probe with selectivity for G-quadruplex (G4) structures. Over the past few years, G4 ligands have emerged as promising candidates for the development of antiparasitic agents. Building on this concept, we explored extending ThT’s benzothiazole scaffold by introducing various 2-ethenyl aromatic and heteroaromatic moieties, aiming to enhance G4 binding affinity and potential therapeutic effect. A series of benzothiazolium derivatives were synthesized and evaluated for their antiproliferative and antiparasitic activity. Several 2-ethenyl benzothiazole derivatives showed submicromolar activity against Leishmania spp. and Trypanosoma brucei parasites, with up to 200-fold selectivity over MRC-5 human lung fibroblasts. Notably, compound 2b demonstrated remarkable potency, with an IC50 of 0.48 nM and a selectivity index of 46,151 against Leishmania major amastigotes, and an IC50 of 0.019 nM and a selectivity index of 79,206 against T. brucei. In fact, compound 2b demonstrated superior efficacy and selectivity in comparison to the clinically used drugs suramin, fexinidazole, miltefosine, and amphotericin B. Biophysical studies revealed that all tested derivatives exhibited significant G4 stabilization, surpassing ThT. Location of compound 2b inside the nucleus and the kinetoplast, as well as partially in the mitochondria, opens up the possibility of 2b acting against the parasite through binding to G4.

The ability to selectively control DNA conformation using light as an external stimulus offers unique opportunities to control specific DNA sequences in biological settings and to develop nucleotide-b...

Carbon-based functional nanomaterials with distinct photoluminescent properties have gained significant attention for their diverse applications in bioimaging, biomedicine, and antimicrobial treatment...