Metasurface‐Based Molecular Biosensing Aided by Artificial Intelligence

Molecular spectroscopy provides unique information on the internal structure of biological materials by detecting the characteristic vibrational signatures of their constituent chemical bonds at infrared frequencies. Nanophotonic antennas and metasurfaces have driven this concept towards few‐molecule sensitivity by confining incident light into intense hot spots of the electromagnetic fields, providing strongly enhanced light‐matter interaction. In this Minireview, recently developed molecular biosensing approaches based on the combination of dielectric metasurfaces and imaging detection are highlighted in comparison to traditional plasmonic geometries, and the unique potential of artificial intelligence techniques for nanophotonic sensor design and data analysis is emphasized. Because of their spectrometer‐less operation principle, such imaging‐based approaches hold great promise for miniaturized biosensors in practical point‐of‐care or field‐deployable applications.     

Determination of the effective correlation time modulating 1H NMR relaxation processes of bound water in protein solutions

The relaxation in protein solutions has mainly been studied by nuclear magnetic relaxation dispersion (NMRD) techniques. NMRD data have mostly been analyzed in terms of fast chemical exchange of water between free water and water bound to proteins. Several approaches were used for the estimation of correlation time modulating the relaxation mechanism of bound water. On the other hand, in a nuclear magnetic resonance experiment, the relaxation rates of protein solutions (1/T1 and 1/T2) and also those of free water (1/T1f and 1/T2f) are measurable. However, the relaxation rates of bound water (1/T1b and 1/T2b) are not. Despite this, equating (1/T1-1/T1f)/2(1/T2-1/T2f) to (1/T1b)/2(1/T2b) leads to an expression involving only an effective tau that is related to the rotational correlation time (tau r) of proteins. Equating the ratios may therefore give a simple alternative method for the determination of tau r even if this method is limited to a single resonance frequency. In this work, a formula was derived for the solution of the effective tau. Then, the 1/T1 and 1/T2 in solutions of two globular proteins (lysozyme and albumin) and one nonglobular protein (gamma-globulin) were measured for different amounts of each protein. Next, the values of 1/T1 and 1/T2 were plotted vs. protein concentrations, and then the slopes of the fits were used in the derived equation for determining the effective tau values. Finally, the rotational correlation time tau r, calculated from tau, was used in the Stokes-Einstein relation to reproduce relevant radii. The effective tau values of lysozyme, albumin and gamma-globulin were found to be 5.89 ns, 7.03 ns and 8.8 ns, respectively. tau r values of albumin and lysozyme produce their Stokes radii. The present data suggest that use of the measurable ratio in the derived formula may give a simple way for the determination of the correlation times of lysozyme and albumin.     

Preparation of poly(vinyl alcohol) hydrogels with radiation grafted citric and succinic acid groups

Ternary mixtures of PVA/Citric acid (CA)/water and PVA/Succinic acid (SA)/water were gamma irradiated to various doses in air at ambient temperature. Gelation % vs dose curves were constructed and swelling behavior of gels with maximum conversions was studied. In maximum gelled systems 80% of CA used in the feed composition was retained in the gel structure whereas this was only 20% for SA. The volume of swelling of ionic PVA gels increased from 230% to 530% for PVA/CA systems when pH was increased from 2.6 to 7.5. Less significant increase in swelling was observed for PVA/SA gels, from 250% to 330% in the same pH interval. The incorporation of SA and CA groups onto PVA networks improved remarkably the affinity of these structures for Co²⁺ and Ni²⁺ ion uptake.     

Photophysical and antimicrobial properties of new double-armed benzo-15-crown-5 ligands and complexes

Research on Chemical Intermediates - New double-armed crown ether ligands linked to pyridine derivatives have been synthesized and characterized. These macrocyclic ligands (1–5) have been...     

Correlations between microstructure and crystallization of the fluorinated terpolymer of tetrafluoroethylene,hexafluoropropylene, and vinylidene fluoride

Random THV terpolymers consisting of tetrafluoroethylene (TFE), hexafluoropropylene (HFP), and vinylidene fluoride (VDF) are viable alternatives to polytetrafluoroethylene (PTFE) combining excellent chemical stability and thermoplastic processability. Although the properties of THV may be modified by crystallization, little is known on how crystallization is influenced by the chain microstructure of THV. We analyzed the chain microstructure of THV‐221G by solid‐state ¹⁹F NMR spectroscopy under fast magic angle spinning, revealing that THV‐221G contains 43.8 mol % TFE, 46.0 mol % VDF, and 10.2 mol % HFP. Sequence analysis revealed that the TFE units are preferentially located next to other TFE units. The HFP units, which are obstacles to crystallization because of their bulky CF₃ side groups, are preferentially located next to VDF units. WAXS measurements correspondingly revealed the presence of THV‐221G crystals with PTFE‐like packing and of further THV‐221G crystal populations with widened d‐spacings caused by the incorporation of certain amounts of HFP units into the THV‐221G crystals. Under confinement imposed by the cylindrical nanopores of self‐ordered alumina, the THV‐221G melting point decreased with decreasing pore diameter. Although direct impingement of the growing THV‐221G crystals on the pore walls is unlikely, the geometric confinement limits the access of growing THV‐221G crystals to crystallizable THV‐221G chain segments. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019 , 57, 1402–1408     

Crystal Structures of 2-Chloro-3-((3-(trifluoromethyl)phenyl)amino)naphthalene-1,4-dione and 2-Chloro-3-((4-(trifluoromethyl)phenyl)amino)naphthalene-1,4-dione

Crystallography Reports - 2-Chloro-3-((3-(trifluoromethyl)phenyl)amino)naphthalene-1,4-dione (1) and 2-chloro-3-((4-(trifluoromethyl)phenyl)amino)naphthalene-1,4-dione (2) were obtained according...     

Synthesis,antimicrobial and thermal studies of nitropyridine-substituted double armed benzo-15-crown-5 ligands; alkali (Na+ and K+) and transition metal (Ag+) complexes; reduction of nitro compounds

Journal of Inclusion Phenomena and Macrocyclic Chemistry - Nitropyridine substituted double-armed benzo 15-crown-5 compounds (1–4) were synthesized by the reactions of...     

Pre-service mathematics teachers’ concept images of radian

This study investigates pre-service mathematics teachers’ concept images of radian and possible sources of such images. A multiple-case study was conducted for this study. Forty-two pre-service mathematics teachers completed a questionnaire, which aims to assess their understanding of radian. Six of them were selected for individual interviews on the basis of theoretical sampling. The data indicated that participants’ concept images of radian were dominated by their concept images of degree. As the data in this study suggested, pre-service mathematics teachers were reluctant to accept trigonometric functions with the inputs of real numbers but rather they use value in degrees. More interestingly, they have two distinct images of π : π as an angle in radian and π as an irrational number.