Structural Repertoire of HIV-1-Neutralizing Antibodies Targeting the CD4 Supersite in 14 Donors

The site on the HIV-1 gp120 glycoprotein that binds the CD4 receptor is recognized by broadly reactive antibodies, several of which neutralize over 90% of HIV-1 strains. To understand how antibodies achieve such neutralization, we isolated CD4-binding-site (CD4bs) antibodies and analyzed 16 co-crystal structures –8 determined here– of CD4bs antibodies from 14 donors. The 16 antibodies segregated by recognition mode and developmental ontogeny into two types: CDR H3-dominated and VH-gene-restricted. Both could achieve greater than 80% neutralization breadth, and both could develop in the same donor. Although paratope chemistries differed, all 16 gp120-CD4bs antibody complexes showed geometric similarity, with antibody-neutralization breadth correlating with antibody-angle of approach relative to the most effective antibody of each type. The repertoire for effective recognition of the CD4 supersite thus comprises antibodies with distinct paratopes arrayed about two optimal geometric orientations, one achieved by CDR H3 ontogenies and the other achieved by VH-gene-restricted ontogenies

Icephobicity of Penguins <i>Spheniscus Humboldti</i> and an Artificial Replica of Penguin Feather with Air-Infused Hierarchical Rough Structures

Although penguins live in the world’s coldest environment, frost and ice are seldom found on their feathers. That is to say, their feathers exhibit excellent antifrosting or anti-icing properties. We found that their air-infused microscale and nanoscale hierarchical rough structures endow the body feathers of penguins <i>Spheniscus humboldti</i> with hydrophobicity (water CA ≈ 147°) and antiadhesion characteristics (water adhesive force ≈ 23.4 μN), even for supercooled water microdroplets. A polyimide nanofiber membrane with novel microstructures was prepared on an asymmetric electrode by electrospinning, acting as an artificial replica of a penguin’s body feather. The unique microstructure of the polyimide nanofiber membrane results in a density gradient of the surface chemical substance, which is crucial to the formation of gradient changes of the contact angle and adhesive force. With decrease of the density of the surface chemical substance (i.e., with increase of the distance between adjacent fibers), the static water contact angles decreased from ∼154° to ∼105° and the water adhesion forces increased from 37 to 102 μN. Polyimide nanofibers pin a few supercooled water microdroplets. By increasing the distance of adjacent polyimide fibers, coalescence between the pinned water microdroplets was prevented. The polyimide fiber membrane achieved icephobicity

Outstanding thermal stability of cold-rolled Al–Y alloy revealed using in-situ synchrotron X-ray diffraction and ex-situ microscopy

This paper describes the main results from an experimental investigation into the thermal stability of a cold-rolled Al–Y alloy. Tensile tests performed on specimens of the alloy and pure Al in annealed states reveal superior anti-softening properties of the former specimens relative to the latter counterparts. Origins of such thermal stability and underlying recovery and recrystallization kinetics are studied using electron microscopy and high energy X-ray diffraction (HEXRD) techniques. Microscopic observations reveal that recovery and recrystallization begin in the specimens of pure Al at a much lower temperature than in the specimens of Al–Y alloy. Onset of the recovery process in the Al–Y alloy is observed to begin with dislocation rearrangements in the β-Al3Y phases. The onset is followed by more substantial reduction in dislocation density, shrinkage of the β-Al3Y phases, and coarsening of the α-Al grains. The alloy contains stacking faults, which interestingly remain stable during the annealing treatments contributing to the thermal stability. The observed mechanisms are further confirmed by tracking the evolution of peaks under the in-situ synchrotron X-ray diffraction with heating. Onset of recovery was observed at 280 °C in both α-Al and β-Al3Y phases, while substantial shrinkage and spheroidization of β-Al3Y phases and decrease in dislocation density were detected at 400 °C causing loss of the alloy strength. Thermodynamic calculation showed that solubility of Y rapidly increases in α-Al at temperatures above 400 °C explaining the spheroidization and shrinkage of the β-Al3Y phases by diffusion of Y into the Al matrix

A facile synthesis of heterojunctional BiVO₄/Bi₅O₇I with enhanced photocatalytic activity for organic dyes degradation

Abstract Photocatalysis technology has risen to effectively degrade the hardly-degraded organic pollutants in recent years and the photocatalysts play an important role in striding the obstacles of the visible light response. Herein, a high-efficiency BiVO₄/Bi₅O₇I heterojunctional photocatalysts have been purposefully designed by controlling the reactant ratios and ultrasonic time of reaction at room temperature. Photocatalytic experimentals confirm that the prepared optimal BiVO₄/Bi₅O₇I composites displayed enhanced photocatalytic ability to degrade rhodamine B and quinoline blue under visible light irradiation. Furthermore, the photocatalysts exhibits high photostability and reusability proved by four consecutive cycling experiments. A possible mechanism of p–n heterojunctional BiVO₄/Bi₅O₇I composites enhanced the photocatalytic performance was discussed in detail on the basis of the reactive species trapping experiments in photocatalytic degradation process

Interaction of Organic Cation with Water Molecule in Perovskite MAPbI₃: From Dynamic Orientational Disorder to Hydrogen Bonding

Microscopic understanding of interaction between H₂O and MAPbI₃ (CH₃NH₃PbI₃) is essential to further improve efficiency and stability of perovskite solar cells. A complete picture of perovskite from initial physical uptake of water molecules to final chemical transition to its monohydrate MAPbI₃·H₂O is obtained with in situ infrared spectroscopy, mass monitoring, and X-ray diffraction. Despite strong affinity of MA to water, MAPbI₃ absorbs almost no water from ambient air. Water molecules penetrate the perovskite lattice and share the space with MA up to one H₂O per MA at high-humidity levels. However, the interaction between MA and H₂O through hydrogen bonding is not established until the phase transition to monohydrate where H₂O and MA are locked to each other. This lack of interaction in water-infiltrated perovskite is a result of dynamic orientational disorder imposed by tetragonal lattice symmetry. The apparent inertness of H₂O along with high stability of perovskite in an ambient environment provides a solid foundation for its long-term application in solar cells and optoelectronic devices