A vinyl monomer that has the nitrile or carbonyl group conjugated to the CC double bond, such as acrylonitrile, methyl acrylate, and methyl methacrylate, forms a complex with an alkylaluminum halide, and the complex reacts spontaneously with a hydrocarbon monomer such as styrene, propylene, or ethylene, giving a high molecular weight copolymer. The copolymers always contain the two monomer units in 1:1 ratio. Thus styrene, copolymerized with methyl acrylate or methyl methacrylate in the presence of ethylaluminum sesquichloride in homogeneous toluene solution, gives such an equimolar copolymer regardless of the initial monomer compositions. The NMR spectra of these copolymers are distinctly different from those of the equimolar copolymers obtained with azobisisobutyronitrile as initiator and have simpler and well separated patterns. The copolymers and the corresponding radical copolymers appear to be amorphous, judged by their x‐ray diffraction patterns and their differential thermal analyses. Their infrared spectra resemble each other very closely. Hence, the difference in the NMR spectra may be ascribed to the matter of the sequence distribution. The infrared spectrum of ethylene–methyl acrylate copolymer shows no absorption near 720 cm.−1 due to the methylene sequence arising from ethylene–ethylene linkage. These experimental data lead to the inference that the equimolar copolymers obtained in this work may have an alternating sequence.
Protein−protein interactions that can be controlled by environmental triggers have immense potential in various biological and industrial applications. In the current study, we aimed to engineer a pH-dependent protein−protein interaction that employs intramolecular electrostatic repulsion through a structure-guided histidine substitution approach. We implemented this strategy on Streptococcal protein G, an affinity ligand for immunoglobulin G, and showed that even a single point mutation effectively improved the pH sensitivity of the binding interactions without adversely affecting its structural stability or its innate binding function. Depending on the pH of the environment, the protein−protein interaction was disrupted by the electrostatic repulsion between the substituted histidine and its neighboring positively charged residues. Structurally, the substituted histidine residue was located adjacent to a lysine residue that could form hydrogen bonds with immunoglobulin G. Thermodynamically, the introduced electrostatic repulsion was reflected in the significant loss of the exothermic heat of the binding under acidic conditions, whereas accompanying enthalpy−entropy compensation partly suppressed the improvement of the pH sensitivity. Thus, the engineered pH-sensitive protein G could enable antibody purification under mildly acidic conditions. This intramolecular design can be combined with conventional protein−protein interface design. Moreover, the method proposed here provides us with additional design criteria for optimization of pH-dependent molecular interactions.
The absorption spectrum of the nitrogen molecule in the 30 A region has been studied photographically, using synchrotron radiation from a 1.3-BeV electron synchrotron as the background continuum. A 2-m grazing incidence spectrograph with a glass grating was used to take the absorption spectrum. Discrete structure has been observed near the K edge of nitrogen. On the basis of electron configuration, the absorption data obtained are compared with the optical spectroscopic data of the NO molecule and it is found that the absorption structure is well explained as due to the excitations of a Is electron to outer-shell orbitals of the nitrogen molecule. The energy value of 409.5 ±0.1 eV is obtained for the K level of the nitrogen molecule.
We demonstrated a polarization-resolved high resolution spectroscopy of a visible emission line of highly charged tungsten ions ( 0 = 668.899 nm, M. Shinohara et al, Phys. Scr., Submitted) for the Large Helical Device (LHD) plasma, where the tungsten ions were introduced by a pellet injection. Its spectral profile shows broadening and polarization dependence, which are attributed to the Doppler and Zeeman effects, respectively. The tungsten ion temperature was evaluated for the first time from the broadening of visible the emission line, with its emission location determined by the Abel inversion of the chord-integrated emission intensities observed with multiple chords. The tungsten ion temperature was found to be close to the helium-like argon ion temperature, which is used as an ion temperature monitor in LHD.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.