Organic Crystals with Response to Multiple Stimuli: Mechanical Bending, Acid-Induced Bending and Heating-Induced Jumping.

Multiple stimuli-responsive molecular crystals are attracting extensive attentions due to their potential as smart materials, such as molecular machines, actuators, and sensors. However, the task of giving a single crystal multiple stimuli-responsive properties remains extremely challenging. Herein, we found two polymorphs (Form O and Form R) of a Schiff base compound, which could respond to multiple stimuli (external force, acid, heat). Form O and Form R have different elastic deformability, which can be attributed to the differences in the molecular conformation, structural packing and intermolecular interactions. Moreover, both polymorphs exhibit reversible bending driven by volatile acid vapor, which we hypothesize is caused by reversible protonation reaction of imines with formic acid. In addition, jumping can be triggered by heating due to the significant anisotropic expansion. The integration of reversible bending and jumping into one single crystal expands the application scope of stimuli-responsive crystalline materials.

Outcomes of structure, function and flavor of pea protein isolate treated by AC, DC and pulsed electric fields.

Based on the standpoint of low carbon footprint processing and less denaturation of plant protein ingredient, the effects of pulsed electric field (PEF), direct current electric field (DCEF), and alternating current electric field (ACEF) treatments on the structure, functional properties and volatile compounds of pea protein isolate were investigated. The results showed that the electric fields (EFs) caused both blueshifts (max. âˆ¼8 cm-1) and redshifts (max. âˆ¼7 cm-1) in the IR spectra and blueshifts (max. âˆ¼5 nm) in the UV spectra. PEF caused an increase of emulsifying activity index and a decrease of emulsion stability index to DCEF and ACEF. A total of 27 volatile compounds were identified and the EFs could cause emerging of new volatiles and disappearing of inherent volatiles potentially to modify the flavor of products. Alterations were significantly observed among the types of EF, but seldomly among the operating parameter levels in the same EF.

Enhancement of lysozyme crystallization under ultrasound field.

With the increasing demand for biopharmaceuticals, a method to crystallize biomolecule products with high quality, high yield and uniform size distribution as well as regular crystal habit is needed. In this work, ultrasound was used as a nucleation accelerator to decrease the energy barrier for lysozyme crystal formation. Crystallization experiments on egg-white lysozyme were carried out with and without ultrasound. The effect of ultrasound on induction time, metastable zone width, crystal size and morphology and process yield was investigated in detail. The nucleation-promoting effect produced by ultrasound is illustrated by the reduction of metastable zone width and induction time. By inducing faster nucleation, ultrasound leads to protein crystals grow at lower supersaturation levels with shorter induction time. It was found that ultrasound could result in uniform size distribution of the product due to the preventing of aggregation. However, long time continuous application of ultrasound could result in smaller particle size. Hence, ultrasonic-stop method was found to be a more appropriate strategy to enhance the crystallization process of proteins such as lysozyme.

Total syntheses of schilancidilactones A and B, schilancitrilactone A, and 20-epi-schilancitrilactone A via late-stage nickel-catalyzed cross coupling.

The first total syntheses of schilancidilactones A and B, schilancitrilactone A, and 20-epi-schilancitrilactone A have been accomplished using a nickel-catalyzed cross coupling of alkyl bromide with vinyl stannane as the final step. The other key steps include late-stage C(sp3)-H bromination, the oxidative cleavage of a diol to provide the requisite ketone and ester for schilancidilactones A and B, and Dieckmann-type condensation to generate the A ring of schilancitrilactone A and 20-epi-schilancitrilactone A.