Active reconfiguration of cytoplasmic lipid droplets governs migration of nutrient-limited phytoplankton

in Science Advances (2022), 8(44), 1-16

Nutrient availability, along with light and temperature, drives marine primary production. The ability to migrate vertically, a critical trait of motile phytoplankton, allows species to optimize nutrient ... [more ▼]

Nutrient availability, along with light and temperature, drives marine primary production. The ability to migrate vertically, a critical trait of motile phytoplankton, allows species to optimize nutrient uptake, storage, and growth. However, this traditional view discounts the possibility that migration in nutrient-limited waters may be actively modulated by the emergence of energy-storing organelles. Here, we report that bloom-forming raphidophytes harness energy-storing cytoplasmic lipid droplets (LDs) to biomechanically regulate vertical migration in nutrient-limited settings. LDs grow and translocate directionally within the cytoplasm, steering strain-specific shifts in the speed, trajectory, and stability of swimming cells. Nutrient reincorporation restores their swimming traits, mediated by an active reconfiguration of LD size and coordinates. A mathematical model of cell mechanics establishes the mechanistic coupling between intracellular changes and emergent migratory behavior. Amenable to the associated photophysiology, LD-governed behavioral shift highlights an exquisite microbial strategy toward niche expansion and resource optimization in nutrient-limited oceans. [less ▲]

Machine learning of material properties: Predictive and interpretable multilinear models

in Science Advances (2022)

Ferroelectric/paraelectric superlattices for energy storage

in Science Advances (2022), 8

Molecular ruler mechanism and interfacial catalysis of the integral membrane acyltransferase PatA

in Science Advances (2021), 7(42),

Glycolipids are prominent components of bacterial membranes that play critical roles not only in maintaining the structural integrity of the cell but also in modulating host-pathogen interactions. PatA is ... [more ▼]

Glycolipids are prominent components of bacterial membranes that play critical roles not only in maintaining the structural integrity of the cell but also in modulating host-pathogen interactions. PatA is an essential acyltransferase involved in the biosynthesis of phosphatidyl-myo-inositol mannosides (PIMs), key structural elements and virulence factors of Mycobacterium tuberculosis. We demonstrate by electron spin resonance spectroscopy and surface plasmon resonance that PatA is an integral membrane acyltransferase tightly anchored to anionic lipid bilayers, using a two-helix structural motif and electrostatic interactions. PatA dictates the acyl chain composition of the glycolipid by using an acyl chain selectivity “ruler.” We established this by a combination of structural biology, enzymatic activity, and binding measurements on chemically synthesized nonhydrolyzable acyl–coenzyme A (CoA) derivatives. We propose an interfacial catalytic mechanism that allows PatA to acylate hydrophobic PIMs anchored in the inner membrane of mycobacteria, through the use of water-soluble acyl-CoA donors. [less ▲]

Quantum mechanics of proteins in explicit water: The role of plasmon-like solute-solvent interactions

in Science Advances (2019), 5(12), 0024

Quantum-mechanical van der Waals dispersion interactions play an essential role in intraprotein and protein-water interactions—the two main factors affecting the structure and dynamics of proteins in ... [more ▼]

Quantum-mechanical van der Waals dispersion interactions play an essential role in intraprotein and protein-water interactions—the two main factors affecting the structure and dynamics of proteins in water. Typically, these interactions are only treated phenomenologically, via pairwise potential terms in classical force fields. Here, we use an explicit quantum-mechanical approach of density-functional tight-binding combined with the many-body dispersion formalism and demonstrate the relevance of many-body van der Waals forces both to protein energetics and to protein-water interactions. In contrast to commonly used pairwise approaches, many-body effects substantially decrease the relative stability of native states in the absence of water. Upon solvation, the protein-water dispersion interaction counteracts this effect and stabilizes native conformations and transition states. These observations arise from the highly delocalized and collective character of the interactions, suggesting a remarkable persistence of electron correlation through aqueous environments and providing the basis for long-range interaction mechanisms in biomolecular systems. [less ▲]

Liquid crystal elastomer shell actuators with negative order parameter

in Science Advances (2019), 5(4), 1

Liquid crystals (LCs) are nonsolids with long-range orientational order, described by a scalar order parameter ⟨P2⟩=1/2⟨3cos2β−1⟩. Despite the vast set of existing LC materials, one-third of the order ... [more ▼]

Liquid crystals (LCs) are nonsolids with long-range orientational order, described by a scalar order parameter ⟨P2⟩=1/2⟨3cos2β−1⟩. Despite the vast set of existing LC materials, one-third of the order parameter value range, −1/2< 〈P2〉 < 0, has until now been inaccessible. Here, we present the first material with negative LC order parameter in its ground state, in the form of elastomeric shells. The optical and actuation characteristics are opposite to those of conventional LC elastomers (LCEs). This novel class of anti-ordered elastomers gives access to the previously secluded range of liquid crystallinity with 〈P2〉 < 0, providing new challenges for soft matter physics and adding a complementary type of LCE actuator that is attractive for applications in, e.g., soft robotics [less ▲]

Reliable and practical computational description of molecular crystal polymorphs

in Science Advances (2019), 5

Reliable prediction of the polymorphic energy landscape of a molecular crystal would yield profound insight into drug development in terms of the existence and likelihood of late-appearing polymorphs ... [more ▼]

Reliable prediction of the polymorphic energy landscape of a molecular crystal would yield profound insight into drug development in terms of the existence and likelihood of late-appearing polymorphs. However, the computational prediction of molecular crystal polymorphs is highly challenging due to the high dimensionality of conformational and crystallographic space accompanied by the need for relative free energies to within 1 kJ/mol per molecule. In this study, we combine the most successful crystal structure sampling strategy with the most successful first-principles energy ranking strategy of the latest blind test of organic crystal structure prediction methods. Specifically, we present a hierarchical energy ranking approach intended for the refinement of relative stabilities in the final stage of a crystal structure prediction procedure. Such a combined approach provides excellent stability rankings for all studied systems and can be applied to molecular crystals of pharmaceutical importance. [less ▲]

Quantum mechanics of proteins in explicit water: The role of plasmon-like solute-solvent interactions

in Science Advances (2019)

Multiple-q noncollinear magnetism in an itinerant hexagonal magnet

in SCIENCE ADVANCES (2018), 4(11),

rticle Figures & Data Info & Metrics eLetters PDF Abstract Multiple-q spin order, i.e., a spin texture characterized by a multiple number of coexisting magnetic modulation vectors q, has recently ... [more ▼]

rticle Figures & Data Info & Metrics eLetters PDF Abstract Multiple-q spin order, i.e., a spin texture characterized by a multiple number of coexisting magnetic modulation vectors q, has recently attracted attention as a source of nontrivial magnetic topology and associated emergent phenomena. One typical example is the triple-q skyrmion lattice state stabilized by Dzyaloshinskii-Moriya interactions in noncentrosymmetric magnets, while the emergence of various multiple-q states of different origins is expected according to the latest theories. Here, we investigated the magnetic structure of the itinerant polar hexagonal magnet Y3Co8Sn4, in which several distinctive mechanisms favoring multiple-q states are allowed to become active. Small-angle neutron-scattering experiments suggest the formation of incommensurate triple-q magnetic order with an in-plane vortex-like spin texture, which can be most consistently explained in terms of the novel four-spin interaction mechanism inherent to itinerant magnets. The present results suggest a new route to realizing exotic multiple-q orders and that itinerant hexagonal magnets, including the R3M8Sn4 family with wide chemical tunability, can be a unique material platform to explore their rich phase diagrams. [less ▲]

Catalysis beyond frontier molecular orbitals: Selectivity in partial hydrogenation of multi-unsaturated hydrocarbons on metal catalysts

in Science Advances (2017), 3

The mechanistic understanding and control over transformations of multi-unsaturated hydrocarbons on transition metal surfaces remains one of the major challenges of hydrogenation catalysis. To reveal the ... [more ▼]

The mechanistic understanding and control over transformations of multi-unsaturated hydrocarbons on transition metal surfaces remains one of the major challenges of hydrogenation catalysis. To reveal the microscopic origins of hydrogenation chemoselectivity, we performed a comprehensive theoretical investigation on the reactivity of two a,b-unsaturated carbonyls—isophorone and acrolein—on seven (111) metal surfaces: Pd, Pt, Rh, Ir, Cu, Ag, and Au. In doing so, we uncover a general mechanism that goes beyond the celebrated frontier molecular orbital theory, rationalizing the C--C bond activation in isophorone and acrolein as a result of significant surface-induced broadening of high-energy inner molecular orbitals. By extending our calculations to hydrogen-precovered surface and higher adsorbate surface coverage, we further confirm the validity of the “inner orbital broadening mechanism” under realistic catalytic conditions. The proposed mechanism is fully supported by our experimental reaction studies for isophorone and acrolein over Pd nanoparticles terminated with (111) facets. Although the position of the frontier molecular orbitals in these molecules, which are commonly considered to be responsible for chemical interactions, suggests preferential hydrogenation of the C--O double bond, experiments show that hydrogenation occurs at the C--C bond on Pd catalysts. The extent of broadening of inner molecular orbitals might be used as a guiding principle to predict the chemoselectivity for a wide class of catalytic reactions at metal surfaces. [less ▲]