KAT Ligation for Rapid and Facile Covalent Attachment of Biomolecules to Surfaces

Rapid Formation of Non-canonical Phospholipid Membranes by Chemoselective Amide-Forming Ligations with Hydroxylamines

There has been increasing interest in methods to generate synthetic lipid membranes as key constituents of artificial cells or to develop new tools for remodeling membranes in living cells. However, the biosynthesis of phospholipids involves elaborate enzymatic pathways that are challenging to reconstitute in vitro. An alternative approach is to use chemical reactions to non-enzymatically generate natural or non-canonical phospholipids de novo. Previous reports have shown that synthetic lipid membranes can be formed in situ using various ligation chemistries, but these methods lack biocompatibility and/or suffer from slow kinetics at physiological pH. Thus, it would be valuable to develop chemoselective strategies for synthesizing phospholipids from water-soluble precursors that are compatible with synthetic or living cells Here, we demonstrate that amide-forming ligations between lipid precursors bearing hydroxylamines and α-ketoacids (KAs) or potassium acyltrifluoroborates (KATs) can be used to prepare non-canonical phospholipids at physiological pH conditions. The generated amide-linked phospholipids spontaneously self-assemble into cell-like micron-sized vesicles similar to natural phospholipid membranes. We show that lipid synthesis using KAT ligation proceeds extremely rapidly, and the high selectivity and biocompatibility of the approach facilitates the in situ synthesis of phospholipids and associated membranes in living cells.

Calcium carbonate as sorbent for lead removal from wastewaters

Low-cost and largely available industrial by-products such as calcite (CaCO₃) have been considered as sorbents to remediate wastewaters from toxic elements, such as lead, in compliance with the European circular economy strategy. To date few articles are reporting results on lead sorption at the calcite-water solution interface by X-ray photoelectron spectroscopy (XPS) and this investigation aims to clarifying the mechanism of the interaction of Pb²⁺ model solutions over a wide concentration range, from 0.1 μM to 80 mM, with commercial calcite. X-ray powder diffraction (XRPD), scanning electron microscopy (SEM, EDX) and XPS analysis indicate that when CaCO₃ particles are soaked in Pb²⁺ 0.1 mM and 1 mM solutions, hexagonal platelets of hydrocerussite [(PbCO₃)₂ Pb(OH)₂] precipitate on its surface. When the concentration of Pb²⁺ is equal or higher than 40 mM, prismatic acicula of cerussite [PbCO₃] precipitate. Solution analysis by atomic emission spectroscopy (ICP-AES) and ICP-mass spectrometry (ICP-MS) indicate that Pb²⁺ removal efficiency is nearly 100%; when the initial Pb²⁺ concentration was equal to 0.1 μM it was below the limit of detection (LOD) and the efficiency could not be determined. The sorption capacity (q_e) increases linearly with increasing initial Pb²⁺ concentration up to a value of 1680 (20) mg/g when the initial Pb²⁺concentration is 80 mM. These findings suggest that heterogeneous nucleation and surface co-precipitation occur and calcite can be well considered a very promising sorbent for Pb²⁺ removal from wastewaters within a wide initial concentration range.

Controlling Protein Enrichment in Lipid Sponge Phase Droplets using SNAP-tag Bioconjugation

All cells use organized lipid compartments to facilitate specific biological functions. Membrane-bound organelles create defined spatial environments that favor unique chemical reactions while isolating incompatible biological processes. Despite the fundamental role of cellular organelles, there is a scarcity of methods for preparing functional artificial lipid-based compartments. Here, we demonstrate a robust bioconjugation system for sequestering proteins into zwitterionic lipid sponge phase droplets. Incorporation of benzylguanine (BG)-modified phospholipids that form stable covalent linkages with an O6-methylguanine DNA methyltransferase (SNAP-tag) fusion protein enables programmable control of protein capture. We show that this methodology can be used to anchor hydrophilic proteins at the lipid-aqueous interface, concentrating them within an accessible but protected chemical environment. SNAP-tag technology enables the integration of proteins that regulate complex biological functions in lipid sponge phase droplets, and should facilitate the development of advanced lipid-based artificial organelles.