Direct X‐ray Observation of Trapped CO2 in a Predesigned Porphyrinic Metal–Organic Framework

Metal–organic frameworks (MOFs) are emerging microporous materials that are promising for capture and sequestration of CO₂ due to their tailorable binding properties. However, it remains a grand challenge to pre‐design a MOF with a precise, multivalent binding environment at the molecular level to enhance CO₂ capture. Here, we report the design, synthesis, and direct X‐ray crystallographic observation of a porphyrinic MOF, UNLPF‐2, that contains CO₂‐specific single molecular traps. Assembled from an octatopic porphyrin ligand with [Co₂(COO)₄] paddlewheel clusters, UNLPF‐2 provides an appropriate distance between the coordinatively unsaturated metal centers, which serve as the ideal binding sites for in situ generated CO₂. The coordination of Co^II in the porphyrin macrocycle is crucial and responsible for the formation of the required topology to trap CO₂. By repeatedly releasing and recapturing CO₂, UNLPL‐2 also exhibits recyclability.     

Selective Interactions of O-Methylated Flavonoid Natural Products with Human Monoamine Oxidase-A and -B

A set of structurally related O-methylated flavonoid natural products isolated from Senecio roseiflorus (1), Polygonum senegalense (2 and 3), Bhaphia macrocalyx (4), Gardenia ternifolia (5), and Psiadia punctulata (6) plant species were characterized for their interaction with human monoamine oxidases (MAO-A and -B) in vitro. Compounds 1, 2, and 5 showed selective inhibition of MAO-A, while 4 and 6 showed selective inhibition of MAO-B. Compound 3 showed ~2-fold selectivity towards inhibition of MAO-A. Binding of compounds 1–3 and 5 with MAO-A, and compounds 3 and 6 with MAO-B was reversible and not time-independent. The analysis of enzyme-inhibition kinetics suggested a reversible-competitive mechanism for inhibition of MAO-A by 1 and 3, while a partially-reversible mixed-type inhibition by 5. Similarly, enzyme inhibition-kinetics analysis with compounds 3, 4, and 6, suggested a competitive reversible inhibition of MAO-B. The molecular docking study suggested that 1 selectively interacts with the active-site of human MAO-A near N5 of FAD. The calculated binding free energies of the O-methylated flavonoids (1 and 4–6) and chalcones (2 and 3) to MAO-A matched closely with the trend in the experimental IC_50′s. Analysis of the binding free-energies suggested better interaction of 4 and 6 with MAO-B than with MAO-A. The natural O-methylated flavonoid (1) with highly potent inhibition (IC₅₀ 33 nM; Ki 37.9 nM) and >292 fold selectivity against human MAO-A (vs. MAO-B) provides a new drug lead for the treatment of neurological disorders.     

Recognition of Dimethylarginine Analogues by Tandem Tudor Domain Protein Spindlin1

Epigenetic readout of the combinatorial posttranslational modification comprised of trimethyllysine and asymmetric dimethylarginine (H3K4me3R8me2a) takes place via biomolecular recognition of tandem Tudor-domain-containing protein Spindlin1. Through comparative thermodynamic data and molecular dynamics simulations, we sought to explore the binding scope of asymmetric dimethylarginine mimics by Spindlin1. Herein, we provide evidence that the biomolecular recognition of H3K4me2R8me2a is not significantly affected when R8me2a is replaced by dimethylarginine analogues, implying that the binding of K4me3 provides the major binding contribution. High-energy water molecules inside both aromatic cages of the ligand binding sites contribute to the reader–histone association upon displacement by histone peptide, with the K4me3 hydration site being lower in free energy due to a flip of Trp151.     

Use of FTIR spectroscopy coupled with ATR for the determination of atmospheric compounds

Attenuated total reflection Fourier transformed infrared spectroscopy (ATR-FTIR) can be successfully used for the quantitative determination of small amounts of pollutants like the organic fraction of aerosols. The relation between sample concentration and reflectance is described by the Kubelka-Munk equation and was found to be linearly proportional to the absorption band of some functional group. Several parameters like the matter of solid matrix, the cleaning of the sampling support, the treatment of reflectance spectra and the base line correction considerably influenced the reflectance spectra and facilitated data interpretations. The feasibility of the ATR-FTIR was evaluated by the monitoring of specific organic group bands on filters collected in the French cities of Grenoble and Clermont-Ferrand. We have obtained for hydroxyl group a calibration curve by plotting the relative intensity of reflectance versus the concentration. The linearity was obtained for OH from 1 × 10⁻¹ to 1 × 10⁰ mol L⁻¹ with r² = 0.9959. We can consider that for a direct measurement of the intensity of reflectance, it is possible to perform quantitative ATR-FTIR organic group analysis.     

Optimization of Biocompatibility for a Hydrophilic Biological Molecule Encapsulation System

Despite considerable advances in recent years, challenges in delivery and storage of biological drugs persist and may delay or prohibit their clinical application. Though nanoparticle-based approaches for small molecule drug encapsulation are mature, encapsulation of proteins remains problematic due to destabilization of the protein. Reverse micelles composed of decylmonoacyl glycerol (10MAG) and lauryldimethylamino-N-oxide (LDAO) in low-viscosity alkanes have been shown to preserve the structure and stability of a wide range of biological macromolecules. Here, we present a first step on developing this system as a future platform for storage and delivery of biological drugs by replacing the non-biocompatible alkane solvent with solvents currently used in small molecule delivery systems. Using a novel screening approach, we performed a comprehensive evaluation of the 10MAG/LDAO system using two preparation methods across seven biocompatible solvents with analysis of toxicity and encapsulation efficiency for each solvent. By using an inexpensive hydrophilic small molecule to test a wide range of conditions, we identify optimal solvent properties for further development. We validate the predictions from this screen with preliminary protein encapsulation tests. The insight provided lays the foundation for further development of this system toward long-term room-temperature storage of biologics or toward water-in-oil-in-water biologic delivery systems.     

Ultrasonic characterization of shrinkage microporosity in aluminum castings

Shrinkage microporosity in cast aluminum was characterized utilizing the frequency dependence of ultrasonic attenuation caused by scattering from the pores. Measurements were made with the plate specimen immersed in water, and, by using a focused transducer, spatial resolution of about 2 mm was obtained. An accurate measure of attenuation was obtained by comparing the specimen’s ultrasonic signal with that from a pore-free reference specimen. Although the attenuation could be fitted using a single spherical pore size, better fits were obtained by assuming a lognormal distribution of spheres. Pore volume fraction inferred from the lognormal fits overestimates the actual volume fraction, determined from density measurements, by the same factor for all volume fractions. The actual volume fraction is overestimated by more than 100%, due to the complicated, nonspherical pore shapes, and must be taken into account to obtain accurate values of porosity. The strong correlation (r²=0.97) between ultrasonic and density-derived volume fractions permits reliable, nondestructive laboratory measurements of porosity.     

The interaction of O2 with the surface of polycrystalline gadolinium at the temperature range 300–670 K

Auger-Electron-Spectroscopy (AES) and Direct-Recoils-Spectrometry (DRS) were applied to study the interaction of O₂ with a polycrystalline gadolinium surface, in the temperature range 300–670 K and oxygen pressure up to 2 × 10^? 6 Torr. It has been found that initial uptake of oxygen, at coverage measurable by the techniques used here, results in rapid oxide island formation. The subsurface is believed to be a mixture of oxide particles and oxygen dissolved in the Gd metal, the latter being the mobile species, even at relatively low temperatures.Enhanced inward diffusion of oxygen starts as early as 420 K and dictates the surface oxygen concentration and effective thickness of the forming oxide. The oxygen accumulation rate at the near-surface region, as measured by the O(KLL) AES signal intensity, goes through a maximum as a function of temperature at 420 K. This is a result of the combination of still efficient oxygen chemisorption that increases surface occupation and slow inward diffusion. The thickest oxide, ~ 1.7 nm, is formed at 300 K and its effective thickness was found to decrease with increasing temperature (due to oxygen dissolution into the metal bulk).Diffusion coefficients of the oxygen dissolution into the bulk were evaluated for various temperatures utilizing models for infinitely thin oxide layer and thick oxide layer, respectively. The best fit under our experimental procedure was obtained by the thick layer model, and the coefficients that were calculated are D₀ = 2.2 × 10^? 16m²s^? 1 and E_a = 46kJ/mol.     

Mean-field versus microconvection effects in nanofluid thermal conduction

Transient hot-wire data on thermal conductivity of suspensions of silica and perfluorinated particles show agreement with the mean-field theory of Maxwell but not with the recently postulated microconvection mechanism. The influence of interfacial thermal resistance, convective effects at microscales, and the possibility of thermal conductivity enhancements beyond the Maxwell limit are discussed.     

Coherent optical measurement techniques in profilometric determination of local mass transfer coefficients

Some measurement techniques using a coherent light source in profilometric determination of local mass transfer coefficients are described in this paper. Different optical setups for holographic interferometry coupled with the two basic profilometric techniques: the swollen polymer technique and the sublimation technique, are described in detail. Finally, the application of electronic speckle pattern interferometry to profilometric measurements is also discussed.     

Black Holes Are One-Dimensional

The holographic principle has revealed that phyical systems in 3-D space, black holes included, are basically two-dimensional as far as their information content is concerned. This conclusion is complemented by one sketched here: as far as entropy or information flow is concerned, a black hole behaves as a one-dimensional channel. We define a channel in flat spacetime in thermodynamic terms, and contrast it with common entropy emitting systems. A black hole is more like the former: its entropy output is related to the emitted power as it would be for a one-dimensional channel, and disposal of an information stream down a black hole is limited by the power invested in the same way as for a one-dimensional channel.