Search for: All records

Sulfation is a fundamental post-translational modification that imparts negative charge and structural complexity to biomolecules, thereby regulating molecular recognition, signaling, and homeostasis across all domains of life. Yet, the ability to interrogate the biological functions of sulfation has long been hindered by the difficulty of constructing molecules with defined sulfation patterns. This Account summarizes our efforts to develop chemical strategies that enable precise control over sulfation in glycans and proteins. We describe an organobase-promoted sulfur(VI) fluoride exchange (SuFEx) chemistry that allows early stage, chemoselective O-sulfation across a broad substrate scope, providing a general solution to sulfate installation in complex settings. Building on this foundation, we introduce an iterative “clickable disaccharide” platform for the programmable assembly of sequence-defined heparan sulfate glycomimetics, enabling systematic dissection of sulfation-dependent glycan–protein interactions. Extending these concepts to the protein realm, we developed a fluorosulfate tyrosine strategy that installs latent sulfates into peptides and proteins, which can be unmasked under physiological conditions or light control via hydroxamic-acid-mediated Lossen rearrangement, offering spatiotemporal control of sulfation in living systems. Collectively, these approaches delineate a unified chemical framework for constructing and manipulating sulfated biomacromolecules with molecular precision, opening new opportunities to elucidate and engineer the biological roles of sulfation. 

Abstract In this work, we propose a geometric non-linear current response induced by magnetic resonance in magnetic Weyl semimetals. This phenomenon is in analog to the quantized circular photogalvanic effect (de Juan et al., Nat. Commun. 8:15995, 2017) previously proposed for Weyl semimetal phases of chiral crystals. However, the non-linear current response in our case can occur in magnetic Weyl semimetals where time-reversal symmetry, instead of inversion symmetry, is broken. The occurrence of this phenomenon relies on the special coupling between Weyl electrons and magnetic fluctuations induced by magnetic resonance. To further support our analytical solution, we perform numerical studies on a model Hamiltonian describing the Weyl semimetal phase in a topological insulator system with ferromagnetism. 

Abstract We revisit “silent coercion” where an adversary gains access to a voter’s credential without the voter’s knowledge in an E2E verifiable, coercion-resistant Internet voting system. We argue that in this setting, casting an intended vote is impossible since the cryptographic backend can no longer distinguish the voter and adversary. However, we affirm that the voter can still act to nullify adversarial ballots, which is preferable to inaction. We provide a new instantiation of nullification using zero-knowledge proofs and multiparty computation, which improves on the efficiency of the current state-of-the-art. We also demonstrate an example voting system—VoteXX—that uses nullification. Our nullification protocol can complement new and existing techniques for coercion resistance (which all require voters to hide cryptographic keys from the coercer), providing a failsafe option for voters whose keys leak.