Exchange Counterion in Polycationic Hydrogels: Tunability of Hydrophobicity, Water State, and Floating Capability for a Floating pH Device

Smart gel materials are capable of controlling and switching swelling, water state, and wettability properties triggered by external stimuli. In this study, we fabricated a series of polyelectrolyte hydrogels bearing a 3-trimethylammoniumpropyl pendant to a methacrylamide-based backbone and examined the switchability with hydrophobic-like counteranions. The exchange between the initial chloride and camphor sulfate (CaS), dodecyl sulfate (DS), and perfluorooctanoate (PFO) counterions was investigated. The kinetics of the exchange showed that the fast exchange (within 4 h) of PFO allowed for a favorable coordination for ion pairing, resulting in a decrease in hydration. The reversibility of the exchange to the Cl- ion was only enabled for the CaS ion due to its bulkiness, while the PFO and DS hydrogels were unable to exchange, even by using tetrabutylammonium chloride, which is a structurally similar reagent, due to aggregation or the coagulates in the collapsed state of the linear tails of the counterions. The hydrogels exhibited a modulable water state and water swelling. Moreover, the hydrogels containing DS and PFO, as counterions, showed surface hydrophobic (contact angle 90°) and high hydrophobic (110°) behavior, respectively. The Raman spectrometry fluorescence with a pyrene probe indicated an increase in strong hydrogen-bonded water molecules, water confinement, and hydrophobic domains in the PFO hydrogel. Moreover, the PFO-modified hydrogel demonstrated a free-floating ability on the water surface, with a strong water repellency, showing that it has the potential to be applied in a floating pH detection device to distinguish between volatile and nonvolatile bases in a controlled manner.

Sosialisasi Pentingnya Menguasai Bahasa Inggris Bagi Mahasiswa

English is a language that has generally been used as a forum for communication with an international scope, so that English can be said to be universal, where its use is not only a communication bridge in everyday life in the international world but has also penetrated cyber communication. Especially in the current era of globalization, the very fast exchange of information related to scientific developments requires students to have proficiency in mastering English. English proficiency is not only a requirement for students to study abroad, but also for exploring more global knowledge, where available materials such as those in international journals are generally available in English. The problem that arises is that students are constrained in mastering English as a compulsory skill that must be possessed at this time. Therefore, this activity aims to motivate and provide awareness regarding the importance of mastering English among students. This activity was carried out at the FKIP Syiah Kuala University Auditorium which was attended by approximately 120 students. This activity aims to make students more motivated and motivated to hone their mastery of English, so that they have international insights and are useful as a tool to answer the challenges of scientific development in the era of globalization.

Nongaussian Intravoxel Incoherent Motion Diffusion Weighted and Fast Exchange Regime Dynamic Contrast-Enhanced-MRI of Nasopharyngeal Carcinoma: Preliminary Study for Predicting Locoregional Failure

The aim of the present study was to identify whether the quantitative metrics from pre-treatment (TX) non-Gaussian intravoxel incoherent motion (NGIVIM) diffusion weighted (DW-) and fast exchange regime (FXR) dynamic contrast enhanced (DCE)-MRI can predict patients with locoregional failure (LRF) in nasopharyngeal carcinoma (NPC). Twenty-nine NPC patients underwent pre-TX DW- and DCE-MRI on a 3T MR scanner. DW imaging data from primary tumors were fitted to monoexponential (ADC) and NGIVIM (D, D*, f, and K) models. The metrics Ktrans, ve, and τi were estimated using the FXR model. Cumulative incidence (CI) analysis and Fine-Gray (FG) modeling were performed considering death as a competing risk. Mean ve values were significantly different between patients with and without LRF (p = 0.03). Mean f values showed a trend towards the difference between the groups (p = 0.08). Histograms exhibited inter primary tumor heterogeneity. The CI curves showed significant differences for the dichotomized cutoff value of ADC ≤ 0.68 × 10−3 (mm2/s), D ≤ 0.74 × 10−3 (mm2/s), and f ≤ 0.18 (p < 0.05). τi ≤ 0.89 (s) cutoff value showed borderline significance (p = 0.098). FG’s modeling showed a significant difference for the K cutoff value of ≤0.86 (p = 0.034). Results suggest that the role of pre-TX NGIVIM DW- and FXR DCE-MRI-derived metrics for predicting LRF in NPC than alone.

Elucidating dissociation activation energies in host–guest assemblies featuring fast exchange dynamics

GEST-NMR is utilized for quantifying the dissociation activation energy (Ea,out) in host-guest systems featuring fast dissociation dynamics.

Deposition of MoSe2 flakes using cyclic selenides

Diselenadisiletanes possess easy preparation, tailored stability, reactivity, volatility and fast exchange ALD reaction to afford MoSe2 flakes of high quality.

Molecular Recognition of the HPLC Whelk-O1 Selector towards the Conformational Enantiomers of Nevirapine and Oxcarbazepine

The presence of stereogenic elements is a common feature in pharmaceutical compounds, and affording optically pure stereoisomers is a frequent issue in drug design. In this context, the study of the chiral molecular recognition mechanism fundamentally supports the understanding and optimization of chromatographic separations with chiral stationary phases. We investigated, with molecular docking, the interactions between the chiral HPLC selector Whelk-O1 and the stereoisomers of two bioactive compounds, the antiviral Nevirapine and the anticonvulsant Oxcarbazepine, both characterized by two stereolabile conformational enantiomers. The presence of fast-exchange enantiomers and the rate of the interconversion process were studied using low temperature enantioselective HPLC and VT-NMR with Whelk-O1 applied as chiral solvating agent. The values of the energetic barriers of interconversion indicate, for the single enantiomers of both compounds, half-lives sufficiently long enough to allow their separation only at critically sub-ambient temperatures. The chiral selector Whelk-O1 performed as a strongly selective discriminating agent both when applied as a chiral stationary phase (CSP) in HPLC and as CSA in NMR spectroscopy.

Polyelectrolyte interactions enable rapid association and dissociation in high-affinity disordered protein complexes

Highly charged intrinsically disordered proteins can form complexes with very high affinity in which both binding partners fully retain their disorder and dynamics, exemplified by the positively charged linker histone H1.0 and its chaperone, the negatively charged prothymosin α. Their interaction exhibits another surprising feature: The association/dissociation kinetics switch from slow two-state-like exchange at low protein concentrations to fast exchange at higher, physiologically relevant concentrations. Here we show that this change in mechanism can be explained by the formation of transient ternary complexes favored at high protein concentrations that accelerate the exchange between bound and unbound populations by orders of magnitude. Molecular simulations show how the extreme disorder in such polyelectrolyte complexes facilitates (i) diffusion-limited binding, (ii) transient ternary complex formation, and (iii) fast exchange of monomers by competitive substitution, which together enable rapid kinetics. Biological polyelectrolytes thus have the potential to keep regulatory networks highly responsive even for interactions with extremely high affinities.

Al/N-based active Lewis pairs: isocyanate insertion products as efficient nucleophiles employed for the facile generation of highly functional molecules

The previously reported active Lewis pair (ALP) iBu2Al–N(2-Ad)NC5H10 (1) (2-Ad = 2-adamantyl) is readily accessible by hydroalumination of the hydrazone H10C5N–N=(2-C10H14) with H–AliBu2. Treatment of 1 with two equivalents of isocyanates R-N=C=O yields six-membered AlC2N2O heterocycles 2 (2a, R = Ph; 2b, R = p-Tol) by dual insertion into the Al–N bonds. 2a reacts as a nucleophile with carboxylic acid chlorides R-C(O)–Cl [R = CH2tBu, p-Tol, H2CCH(Me)C6H4(4-CH2CHMe2) (Ibu-profen acid chloride), 0.5 (1,4-C6H4)] to afford by elimination of iBu2AlCl and hydrolysis new triuret derivatives R-C(O)[N(Ph)C(O)]2–N(2-Ad)NC5H10 (3a to 3d) as colourless, sparingly soluble solids in moderate (3c) to high (3b) yields. The analogous reaction of 2a with (p-Tol)–C(Cl)=N(p-Tol) leads to the imidoyl derivative (p-Tol)N=C(p-Tol)[N(Ph)C(O)]2–N(2-Ad)NC5H10 (4a), which showed a fast exchange of phenyl and tolyl groups to yield a mixture of isomers. The analogous reaction of 2b affords the corresponding compound 4b for which a single isomer is isolated despite the scrambling of substituents.

Isolation and structure determination of a tetrameric sulfonyl dilithio methandiide in solution based on crystal structure analysis and 6Li/13C NMR spectroscopic data

Dilithio sulfonyl methandiides are a synthetically and structurally highly interesting group of functionalized geminal dianions. Although very desirable, knowledge of the structure of dilithio methandiides in solution was lacking up to now. Herein, we describe the isolation and determination of the structure of tetrameric dilithio (trimethylsilyl)(phenylsulfonyl) methandiide in solution and in the crystal. The elucidation of the structure of the tetramer is based on crystal structure analysis and 13C/6Li NMR spectroscopic data. A characteristic feature of the structure of the tetramer is the C 2 symmetric C–Li chain, composed of four doubly Li-coordinated dianionic carbon and five Li atoms. Three Li atoms are devoid of a contact to a dianionic C atom. The tetramer, the dianionic C atoms of which undergo fast exchange, is in THF solution in fast equilibrium with a further aggregate, which is stable only at low temperatures.