Options to Improve the Mechanical Properties of Protein-Based Materials

While bio-based but chemically synthesized polymers such as polylactic acid require industrial conditions for biodegradation, protein-based materials are home compostable and show high potential for disposable products that are not collected. However, so far, such materials lack in their mechanical properties to reach the requirements for, e.g., packaging applications. Relevant measures for such a modification of protein-based materials are plasticization and cross-linking; the former increasing the elasticity and the latter the tensile strength of the polymer matrix. The assessment shows that compared to other polymers, the major bottleneck of proteins is their complex structure, which can, if developed accordingly, be used to design materials with desired functional properties. Chemicals can act as cross-linkers but require controlled reaction conditions. Physical methods such as heat curing and radiation show higher effectiveness but are not easy to control and can even damage the polymer backbone. Concerning plasticization, effectiveness and compatibility follow opposite trends due to weak interactions between the plasticizer and the protein. Internal plasticization by covalent bonding surpasses these limitations but requires further research specific for each protein. In addition, synergistic approaches, where different plasticization/cross-linking methods are combined, have shown high potential and emphasize the complexity in the design of the polymer matrix.

The Effect of Deoxyfluorination on Intermolecular Interactions in the Crystal Structures of 1,6-Anhydro-2,3-epimino-hexopyranoses

The effect of substitution on intermolecular interactions was investigated in a series of 1,6-anhydro-2,3-epimino-hexopyranoses. The study focused on the qualitative evaluation of intermolecular interactions using DFT calculations and the comparison of molecular arrangements in the crystal lattice. Altogether, ten crystal structures were compared, including two structures of C4-deoxygenated, four C4-deoxyfluorinated and four parent epimino pyranoses. It was found that the substitution of the original hydroxy group by hydrogen or fluorine leads to a weakening of the intermolecular interaction by approximately 4 kcal/mol. The strength of the intermolecular interactions was found to be in the following descending order: hydrogen bonding of hydroxy groups, hydrogen bonding of the amino group, interactions with fluorine and weak electrostatic interactions. The intermolecular interactions that involved fluorine atom were rather weak; however, they were often supported by other weak interactions. The fluorine atom was not able to substitute the role of the hydroxy group in molecular packing and the fluorine atoms interacted only weakly with the hydrogen atoms located at electropositive regions of the carbohydrate molecules. However, the fluorine interaction was not restricted to a single molecule but was spread over at least three other molecules. This feature is a base for similar molecule arrangements in the structures of related compounds, as we found for the C4-Fax and C4-Feq epimines presented here.

Designing luminescent diimine-Cu (I)-phosphine complexes by tuning N-ligand and counteranions: correlation of weak interactions, luminescence and THz absorption spectra

Herein, six new [Cu(N^N)(P^P)]+/0 complexes with different N-ligand and counteranions [Cu2(dmp)2(bdppmapy)I2] (1), [Cu2(dmp)2(bdppmapy)(CN)2]·3CH3OH (2), [Cu(dmp)(bdppmapy)](BF4) (3), [Cu(dmp)(bdppmapy)](ClO4) (4), [Cu(phen)(bdppmapy)](BF4) (5), [Cu(phen)(bdppmapy)](ClO4) (6) have been synthesized and characterized (bdppmapy = N,N-bis[(diphenylphosphino)methyl]-2-pyridinamine,...

Distinguishment of Weak Interactions of Hydrogen Atoms Bound to Carbon Atoms: X-Ray Crystal Structural and Hirshfeld Surface Analyses of 2-Hydroxy-7-methoxy-3-(2,4,6-trimethylbenzoyl)naphthalene with the 2-Methoxylated Homologue

X-ray crystal and Hirshfeld surface analyses of 2-hydroxy-7-methoxy-3-(2,4,6-trimethylbenzoyl)naphthalene and its 2-methoxylated homologue show quantitatively and visually distinct molecular contacts in crystals and minute differences in the weak intermolecular interactions. The title compound has a helical tubular packing, where molecules are piled in a two-folded head-to-tail fashion. The homologue has a tight zigzag molecular string lined up behind each other via nonclassical intermolecular hydrogen bonds between the carbonyl oxygen atom and the hydrogen atom of the naphthalene ring. The dnorm index obtained from the Hirshfeld surface analysis quantitatively demonstrates stronger molecular contacts in the homologue, an ethereal compound, than in the title compound, an alcohol, which is consistent with the higher melting temperature of the former than the latter. Stabilization through the significantly weak intermolecular nonclassical hydrogen bonding interactions in the homologue surpasses the stability imparted by the intramolecular C=O…H–O classical hydrogen bonds in the title compound. The classical hydrogen bond places the six-membered ring in the concave of the title molecule. The hydroxy group opposingly disturbs the molecular aggregation of the title compound, as demonstrated by the distorted H…H interactions covering the molecular surface, owing to the rigid molecular conformation. The position of effective interactions predominate over the strength of the classical/nonclassical hydrogen bonds in the two compounds.

Crystal structure and computational studies of N-((2-ethoxynaphthalen-1-yl)methylene)-4-fluoroaniline

The Schiff base compound, N-((2-ethoxynaphthalen-1-yl)methylene)-4-fluoroaniline, has been synthesized and characterized by X-ray diffraction method. The title compound, C19H16FNO, crystallizes in triclinic, space group P-1 (no. 2), a = 10.6343(9) Å, b = 11.4720(10) Å, c = 13.8297(13) Å, α = 102.466(7)°, β = 104.763(7)°, γ = 98.972(7)°, V = 1552.7(2) Å3, Z = 4, T = 293(2) K, μ(MoKα) = 0.086 mm-1, Dcalc = 1.255 g/cm3, 24355 reflections measured (3.16° ≤ 2Θ ≤ 51°), 5779 unique (Rint = 0.0794, Rsigma = 0.0696) which were used in all calculations. The final R1 was 0.0373 (I > 2σ(I)) and wR2 was 0.0763 (all data). The title compound contains two molecules with a similar structure in the asymmetric unit cell. The packing of the crystal structure is determined by weak C–H···F and C-H···N intermolecular hydrogen bonds. The contributions of these weak interactions in the crystal structure were calculated by the Hirshfeld surfaces and examined by the intermolecular interactions within the structure. The existence, nature and percentage contribution of different intermolecular interactions H···H, C···H, N···H, and F···H were determined using Hirshfeld surface analysis and fingerprint plots.

Two Tautomers of Thiobarbituric Acid in One Crystal: The Experimental Charge Density Perspective

High-quality crystals of a certain polymorphic form of thiobarbituric acid containing both keto and enol tautomers in the asymmetric unit were obtained. High-resolution X-ray diffraction data up to sinθ/λ = 1.0 Å−1 were collected and subsequently successfully used for the refining of the multipolar model of electron density distribution. The use of a crystal containing both ketone and enol forms allowed a direct comparison of the topological analysis results and a closer look at the differences between these two forms. The similarities and differences between the deformation densities, electrostatic potentials, Laplacian maps and bond characteristics of the tautomers were analysed. Additionally, the spectrum of the intermolecular interactions was identified and studied from classical, relatively strong N-H···O and O-H···O hydrogen bonds through weaker N-H···S hydrogen bonds to weak interactions (for instance, C-H···O, C-H···S and N···O). The results of these studies point toward the importance of including both the geometrical features and the details of the electron density distribution in the analysis of such weak interactions.

Reactivity and selectivity modulation within a molecular assembly: recent examples from photochemistry

In recent years, photochemical reactions have emerged as powerful transformations which significantly expand the repertoire of organic synthesis. However, a certain lack of selectivity can hamper their application and limit their scope. In this context, a major research effort continues to focus on an improved control over stereo- and chemoselectivity that can be achieved in molecular assemblies between photosubstrates and an appropriate host molecule. In this tutorial review, some recent, representative examples of photochemical reactions have been collected whose unique outcome is dictated by the formation of a molecular assembly driven by non-covalent weak interactions. Graphical Abstract

Review on Higgs Hidden-Dark Sector Physics

The Standard Model (SM), while extremely powerful as a description of the strong, electromagnetic and weak interactions, does not provide a natural candidate to explain Dark Matter (DM). Theoretical as well as experimental motivation exists for the existence of a hidden or dark sector of phenomena that couples either weakly or in a special way to SM fields. Hidden sector or dark sector states appear in many extensions to SM to provide a particular candidate DM in the universe or to explain astrophysical observations. If there is such a family of Beyond the Standard Model (BSM) particles and interactions, they may be accessible experimentally at the Large Hadron Collider (LHC) at CERN and at future High Energy Colliders. In this paper, the main focus is given on selected searches conducted at LHC experiments related to Higgs Hidden-Dark Sector Physics. The current constraints and future prospects of these studies are summarized.

Question of Parity Non-Conservation in Weak Interactions

In order to reasonably explain the phenomenon of cell bioelectricity, we proposed the conservation law of cell membrane area, established the ion inequality equation, and therefore paid attention to the mystery of "θ-τ". We researched and analyzed the "θ-τ" mystery, discussed the parity non-conservation in weak interactions, suggested possible experiments to test the parity non-conservation in weak interactions, and gave our research and analysis conclusions: The experimental scheme proposed by C. N. Yang and T. D. Lee in the hypothesis cannot be used as a positive evidence of whether the weak interaction parity is conserved, nor can it directly answer whether θ and τ in the "θ-τ" mystery are the same particle; The Co60 β decay experiment such as C. S. Wu is a pseudo-mirror experiment, and it has not overturned the so-called "parity conservation law" or proved the "parity non-conservation" in weak interactions; The "θ-τ" mystery is a "man-made" mystery. θ and τ are two different particles, which may be the result of the same precursor particle being divided into two. Parity conservation or non-conservation under mirror image has no physical significance. The work of C. N. Yang, T. D. Lee, C. S. Wu et al. have brought quantum physicists from the "Little black house" to the "Big black house" or "smaller black house". The right and wise choice is to go back through "the door that came in". With the development of science today, it is time for some contents to reform from the bottom.