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Concept: Fourier transform spectroscopy

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Collisions of excitation pulses in dissipative systems lead usually to their annihilation. In this paper, we report electrochemical experiments exhibiting more complex pulse interaction with collision survival and pulse splitting, phenomena that have rarely been observed experimentally and are only poorly understood theoretically. Using spatially resolved in-situ Fourier transform infrared spectroscopy (FTIR) in the attenuated total reflection configuration, we monitored reaction pulses during the electrochemical oxidation of CO on Pt thin film electrodes in a flow cell. The system forms quasi-1d pulses that align parallel to the flow and propagate perpendicular to it. The pulses split once in a while, generating a second solitary wave in the backward moving direction. Upon collision, the waves penetrate each other in a soliton-like manner. These unusual pulse dynamics could be reproduced with a 3-component reaction-diffusion-migration model with two inhibitor species, one of them exhibiting a long-range spatial coupling. The simulations shed light on existence criteria of such dissipative solitons.

Concepts: Spectroscopy, Light, Refraction, Electrochemistry, Fourier transform, Electrochemical cell, Infrared spectroscopy, Fourier transform spectroscopy

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Time-resolved Fourier transform infrared (FTIR) spectroscopy is a powerful tool to elucidate label-free the reaction mechanisms of proteins. After assignment of the absorption bands to individual groups of the protein, the order of events during the reaction mechanism can be monitored and rate constants can be obtained. Additionally, structural information is encoded into infrared spectra and can be decoded by combining the experimental data with biomolecular simulations. We have determined recently the infrared vibrations of GTP and guanosine diphosphate (GDP) bound to Gαi1, a ubiquitous GTPase. These vibrations are highly sensitive for the environment of the phosphate groups and thereby for the binding mode the GTPase adopts to enable fast hydrolysis of GTP. In this study we calculated these infrared vibrations from biomolecular simulations to transfer the spectral information into a computational model that provides structural information far beyond crystal structure resolution. Conformational ensembles were generated using 15 snapshots of several 100 ns molecular-mechanics/molecular-dynamics (MM-MD) simulations, followed by quantum-mechanics/molecular-mechanics (QM/MM) minimization and normal mode analysis. In comparison with other approaches, no time-consuming QM/MM-MD simulation was necessary. We carefully benchmarked the simulation systems by deletion of single hydrogen bonds between the GTPase and GTP through several Gαi1 point mutants. The missing hydrogen bonds lead to blue-shifts of the corresponding absorption bands. These band shifts for α-GTP (Gαi1-T48A), γ-GTP (Gαi1-R178S), and for both β-GTP/γ-GTP (Gαi1-K46A, Gαi1-D200E) were found in agreement in the experimental and the theoretical spectra. We applied our approach to open questions regarding Gαi1: we show that the GDP state of Gαi1 carries a Mg(2+), which is not found in x-ray structures. Further, the catalytic role of K46, a central residue of the P-loop, and the protonation state of the GTP are elucidated.

Concepts: DNA, Protein, Spectroscopy, Infrared spectroscopy, Fourier transform spectroscopy, Mode shape, Normal mode, Guanosine triphosphate

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Improved methods are required for the recycling of waste printed circuit boards (WPCBs). In this study, WPCBs (1-1.5 cm2 in size) were separated into their components using dimethyl sulfoxide (DMSO) at 60°C for 45 min and a metallographic microscope used to verify their delamination. An increased incubation time of 210 min yielded a complete separation of WPCBs into their components, and copper foils and glass fibers were obtained. The separation time decreased with increasing temperature. When the WPCB size was increased to 2-3 cm2, the temperature required for complete separation increased to 90°C. When the temperature was increased to 135°C, liquid photo solder resists could be removed from the copper foil surfaces. The DMSO was regenerated by rotary decompression evaporation, and residues were obtained. Fourier transform infrared spectroscopy (FT-IR), thermal analysis, nuclear magnetic resonance, scanning electron microscopy and energy-dispersive x-ray spectroscopy were used to verify that these residues were brominated epoxy resins. From FT-IR analysis after the dissolution of brominated epoxy resins in DMSO it was deduced that hydrogen bonding may play an important role in the dissolution mechanism. This novel technology offers a method for separating valuable materials and preventing environmental pollution from WPCBs.

Concepts: Spectroscopy, Nuclear magnetic resonance, Scientific techniques, Fourier transform, Infrared spectroscopy, Fourier transform spectroscopy, Printed circuit board, FR-4

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The purpose of this study is to develop a green strategy to synthesize the cellulose-based nanocomposites and open a new avenue to the high value-added applications of biomass. Herein, we reported a microwave-assisted ionic liquid route to the preparation of cellulose/CuO nanocomposites, which combined three major green chemistry principles: using environmentally friendly method, greener solvents, and sustainable resources. The influences of the reaction parameters including the heating time and the ratio of cellulose solution to ionic liquid on the products were discussed by X-ray powder diffraction, Fourier transform infrared spectrometry, and scanning electron microscopy. The crystallinity of CuO increased and the CuO shape changed from nanosheets to bundles and to particles with increasing heating time. The ratio of cellulose solution to ionic liquid also affected the shapes of CuO in nanocomposites. Moreover, CuO crystals were obtained by thermal treatment of the cellulose/CuO nanocomposites at 800 °C for 3 h in air.

Concepts: Electron, Spectroscopy, Crystal, Solvent, Ionic liquid, Infrared spectroscopy, Fourier transform spectroscopy, Green chemistry

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A significant challenge to realize the full potential of nanotechnology for therapeutic and diagnostic applications is to understand and evaluate how live cells interact with an external stimulus, such as a nanosized particle, and the toxicity and broad risk associated with these stimuli. It is difficult to capture the complexity and dynamics of these interactions by following omics-based approaches exclusively, which can be expensive and time-consuming. Attenuated total reflectance-Fourier transform infrared spectroscopy is well suited to provide noninvasive live-cell monitoring of cellular responses to potentially toxic nanosized particles or other stimuli. This alternative approach provides the ability to carry out rapid toxicity screenings and nondisruptive monitoring of live-cell cultures. We review the technical basis of the approach, the instrument configuration and interface with the biological media, the various effects that impact the data, subsequent data analysis and toxicity, and present some preliminary results on live-cell monitoring.

Concepts: Spectroscopy, Particle physics, Infrared spectroscopy, Fourier transform spectroscopy, Infrared, Near infrared spectroscopy, Applied spectroscopy, Rotational spectroscopy

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Abstract Objective: This work deals with the preparation, characterization and in vitro release study of IBU-loaded gel graft copolymer nanoparticles. Method: Gelatin (Gel) graft copolymer nanoparticles were prepared using styrene (Sty) and/or 2-hydroxyethyl methacrylate (HEMA) monomers in the presence of potassium persulfate and glutaraldehyde as an initiator and cross-linker, respectively. The prepared nanoparticles as sustained release drug carriers were investigated using the nonsteriodal anti-inflammatory model drug, ibuprofen (IBU). Results: The prepared nanoparticles as sustained release drug carriers were investigated using the nonsteriodal anti-inflammatory model drug, IBU. The prepared Gel/HEMA and Gel/Sty nanoparticles exhibited particles size ranging from 15 to 17 nm and from 0.42 to 5 mm, respectively. The dissolution of IBU in phosphate buffer, pH 7.4, at 37°C from the prepared nanoparticles was evaluated using UV spectroscopy. In addition, the prepared nanoparticles were characterized using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), transmitting electron microscope (TEM) and zeta potential/particle size analyzer. In vitro dissolution study showed that the dissolution rates of the crosslinked nanoparticles were retarded relative to the uncrosslinked ones. Moreover, the released amount constantly decreases with increasing gluteraldehyde content in the gel nanoparticles. Conclusion: Crosslinked gel-based graft copolymers exhibited slow IBU release within six hours. Furthermore, results from different characterization techniques such as TEM, particles size and zeta potential measurements confirmed the formation of pH-responsive gel-graft copolymer nanoparticles.

Concepts: Spectroscopy, Polymer, Polymer chemistry, Colloid, Differential scanning calorimetry, Scientific techniques, Infrared spectroscopy, Fourier transform spectroscopy

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Water-soluble dendritic ligands based on tris-2-(5-sulfonato salicylaldimine ethyl)amine (5) and DAB-(5-sulfonato salicylaldimine) (6) (DAB = diaminobutane) were synthesized by means of Schiff base condensation and sulfonation reactions. These dendritic ligands were fully characterized by (1)H NMR, (13)C NMR and FT-IR spectroscopy, elemental analysis and mass spectrometry. Dendritic ligands (5 and 6) in combination with [RhCl(COD)](2) (COD = 1,5-cyclooctadiene) were evaluated in aqueous biphasic hydroformylation of 1-octene. New water-soluble mononuclear 5-sulfonato propylsalicylaldimine Rh(i) complexes (7 and 8) were synthesized and characterized using (1)H NMR, (13)C NMR and FT-IR spectroscopy, elemental analysis as well as mass spectrometry. These complexes were applied as catalyst precursors in aqueous biphasic hydroformylation reactions. All the catalyst precursors were active in the hydroformylation of 1-octene under the investigated conditions. Optimal conditions were realized at 75 °C (40 bars), where the best selectivity for aldehydes was noticed. Catalyst recycling was achieved up to 5 times with minimal loss in conversion and consistent chemoselectivities and regioselectivities. Less Rh leaching was observed in the dendritic systems (5 and 6)/[RhCl(COD)](2) as compared to mononuclear catalyst precursors (7 and 8) as determined by inductively coupled plasma-mass spectrometry (ICP-MS).

Concepts: Spectroscopy, Mass spectrometry, Analytical chemistry, Functional groups, Scientific techniques, Chemical structure, Infrared spectroscopy, Fourier transform spectroscopy

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The transport of proteins through skin can be facilitated potentially by using terpenes as chemical enhancers. However, we do not know about the effects of these enhancers on the stability and biological activity of proteins which is crucial for the development of safe and efficient formulations. Therefore, this project investigated the effects of terpene-based skin penetration enhancers which are reported as nontoxic to the skin (e.g., limonene, p-cymene, geraniol, farnesol, eugenol, menthol, terpineol, carveol, carvone, fenchone, and verbenone), on the conformational stability and biological activity of a model protein lysozyme. Terpene (5% v/v) was added to lysozyme solution and kept for 24 h (the time normally a transdermal patch remains) for investigating conformational stability profiles and biological activity. Fourier transform infrared spectrophotometer was used to analyze different secondary structures, e.g., α-helix, β-sheet, β-turn, and random coil. Conformational changes were also monitored by differential scanning calorimeter by determining midpoint transition temperature ™ and calorimetric enthalpy (ΔH). Biological activity of lysozyme was determined by measuring decrease in A (450) when it was added to a suspension of Micrococcus lysodeikticus. The results of this study indicate that terpenes 9, 10, and 11 (carvone, L-fenchone, and L-verbenone) decreased conformational stability and biological activity of lysozyme significantly (p < 0.05) less than other terpenes used in this study. It is concluded that smaller terpenes containing ketones with low lipophilicity (log K (ow) ∼2.00) would be optimal for preserving conformational stability and biological activity of lysozyme in a transdermal formulation containing terpene as permeation enhancer.

Concepts: DNA, Gene, Transdermal patch, Differential scanning calorimetry, Terpene, Terpenes and terpenoids, Fourier transform spectroscopy, Limonene

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Polyhexamethylene biguanide (PHMB) is a cationic biocide. The antibacterial mode of action of PHMB (at concentrations not exceeding its minimal inhibitory concentration) upon Listeria innocua LRGIA 01 was investigated by Fourier transformed infrared spectroscopy and fluorescence anisotropy analysis. Fourier transformed infrared spectra of bacteria treated with or without PHMB presented some differences in the lipids region: the CH(2)/CH(3) (2924 cm(-1)/2960 cm(-1)) band areas ratio significantly increased in the presence of PHMB. Since this ratio generally reflects membrane phospholipids and membrane microenvironment of the cells, these results suggest that PHMB molecules interact with membrane phospholipids and, thus, affect membrane fluidity and conformation. To assess the hypothesis of PHMB interaction with L. innocua membrane phospholipids and to clarify the PHMB mode of action, we performed fluorescence anisotropy experiments. Two probes, 1,6-diphenyl-1,3,5-hexatriene (DPH) and its derivative 1-[4-(trimethyl-amino)-phenyl]-6-phenylhexa-1,3,5-triene (TMA-DPH), were used. DPH and TMA-DPH incorporate inside and at the surface of the cytoplasmic membrane, respectively. When PHMB was added, an increase of TMA-DPH fluorescence anisotropy was observed, but no changes of DPH fluorescence anisotropy occurred. These results are consistent with the hypothesis that PHMB molecules perturb L. innocua LRGIA 01 cytoplasmic membrane by interacting with the first layer of the membrane lipid bilayer.

Concepts: Spectroscopy, Cell membrane, Lipid, Membrane biology, Lipid bilayer, Infrared spectroscopy, Fourier transform spectroscopy, PAPB