Cytocompatible nanofibrous thixotropic supramolecular hydrogel based on a low molecular weight bis-urea derivative.

In this article, an analytical methodology to investigate the proteinaceous content in atmospheric size-resolved aerosols collected at the Zeppelin observatory (79 °N, 12 °E) at Ny Ålesund, Svalbard, from September to December 2015, is proposed. Quantitative determination was performed after acidic hydrolysis using ultrahigh-performance liquid chromatography in reversed-phase mode coupled to electrospray ionization tandem mass spectrometry. Chromatographic separation, as well as specificity in the identification, was achieved by derivatization of the amino acids with N-butyl nicotinic acid N-hydroxysuccinimide ester prior to the analysis. The chromatographic run was performed within 11 min and instrumental levels of detection (LODs) were between 0.2 and 8.1 pg injected on the column, except for arginine which exhibited an LOD of 37 pg. Corresponding method LODs were between 0.01 and 1.9 fmol/m, based on the average air sampling volume of 57 m. The sum of free amino acids and hydrolyzed polyamino acids was shown to vary within 6-2914 and 0.02-1417 pmol/m for particles in sizes < 2 and 2-10 μm in equivalent aerodynamic diameter, respectively. Leucine, alanine, and valine were the most abundant among the amino acids in both aerosol size fractions. In an attempt to elucidate source areas of the collected aerosols, 5- to 10-day 3D backward trajectories reaching the sampling station were calculated. Overall, the method described here provides a first time estimate of the proteinaceous content, that is, the sum of free and polyamino acids, in size-resolved aerosols collected in the Arctic. Graphical Abstract ᅟ.

The current approach to designing low‐molecular‐weight gelators relies on a laborious trial‐and‐error process, mainly because of the lack of an accurate description of the noncovalent interactions crucial for supramolecular gelation. In this work, we report a multiscale bottom‐up approach composed of several computational techniques to unravel the key interactions in a library of synthesized bis‐urea‐based gelators and rationalize their experimentally observed hydrogelation performance. In addition to density functional theory calculations and molecular dynamics, the noncovalent interaction index is applied as a tool to visualise and identify the different types of noncovalent interactions. Interestingly, as well as hydrogen bonds between urea moieties, hydrogen bonds between a urea moiety and a pyridine ring were shown to play a detrimental role in the early aggregation phase. These findings enabled us to explain the hydrogelation performance observed in a library of twelve bis‐urea derivatives, which were synthesized with 58–95 % yields. From this library, three compounds were discovered to effectively gel water, with the most efficient hydrogelator only requiring a concentration of 0.2 w/v%.

holding, protection against biochemical stress or addition of strength and structure; and hemicellulose, which coordinates cellulose together with lignin (Boerjan et al. 2003; Hansen and Björkman 1998; Panshin and De Zeeuw 1980). Cellulose, as the main constituent of plant cell walls, provides the structural support. It consists of b-D-glucopyranose sugar units, which contain three hydroxyl groups at the C-2, C-3 and C-6 positions. They can form strong hydrogen bonds, constituting the crystalline and amorphous regions within the fibers, which interact with each other to form cellulose microfibrils. Cellulose is known to exist in different polymorphs depending on the molecular orientation and hydrogen-bonding network in crystalline domains. The four main polymorphs of cellulose are cellulose I, cellulose II, cellulose III and cellulose IV. The most extensively investigated are cellulose I, which is the dominant form in natural wood and plants, and cellulose II that can be obtained from cellulose I either by chemical regeneration or mercerization, due to its relatively low thermal stability. Cellulose I, present in native cellulose, exists as cellulose Ia (triclinic unit cell) and cellulose Ib (monoclinic unit cell), both with cellulose chains adopting parallel configurations. In contrast, the chains of cellulose II are in an antiparallel configuration and exist in a monoclinic unit cell (Gong et al. 2017). Despite cellulose I exhibits much better mechanical properties than cellulose II (O'Sullivan 1997; Yu et al. 2014), the later has a more stable structure, making it preferable for various applications. Cellulose can be submitted to a wide variety of chemical modifications due to the three hydroxyl groups present in its structure. Furthermore, reactivity of cellulose can be enhanced through previous Keywords Cellulose Á Jute fibers Á Ball milling Á Isocyanate

The cover picture shows the clustering of bis‐urea‐based hydrogelator molecules as the reflection in a camera lens. A combination of computational techniques, such as density functional theory, molecular dynamics and the noncovalent interaction index, is used to virtually zoom in on the self‐assembly behavior of these molecules. This integrated approach allows rationalization of the experimentally observed gelation performance in a library of newly synthesized bis‐urea based derivatives, from which three efficient hydrogelators were discovered. More details are given in the Full Paper by M. Alonso and co‐workers on page 267 in Issue 2, 2020 (DOI: 10.1002/cplu.201900551).