Conceptions and troublesome knowledge on acid-base using the two-tier multiple-choice diagnostic test

Acid-base is one of the materials that tend to be difficult for students to understand. Acid-base is a material that is conceptually solid and requires an integrated understanding of many of the concepts of introductory chemistry. This research is descriptive research that aims to find conceptions of students on acid-base subjects and asking about concepts that are considered troublesome according to their learning experiences. The subjects of this research were 31 students of class XI IPA 4 at SMAN 3 Pariaman. The instruments in this research are diagnostic tests and interviews. The result of this research is the students of SMAN 3 Pariaman have difficulties in learning about the acid-base subject with high category. The percentage of conceptions experienced by students in each indicator is 56.3% of students understand the concept, 20.8% misconception, and 22.9% do not understand the concept. In the second indicator, 45.2% of students understood the concept, 18.3% had misconceptions and 36.5% did not understand the concept. In the 3rd indicator, 35.5% of students understood the concept, 31.2% had misconceptions and 33.3% did not understand the concept. In the 4th indicator, 21.9% of students understand the concept, 27.7% do not understand the concept and 50.3% do not understand the concept. Meanwhile, the acid-base theory, the calculation of pH or pOH, and the relationship between the degree of acidity (pH) and the degree of ionization (a), and the acid equilibrium constant (Ka) or the base equilibrium constant (Kb) are considered troublesome knowledge because they can be conceptually difficult.

Drug-like Properties and Fraction Lipophilicity Index as a combined metric

Fraction Lipophicity Index (FLI) has been developed as a composite drug-like metric combining logP and logD in a weighted manner. In the present study an extended data set confirmed the previously established drug-like FLI range 0-8 using two calculation systems for logP /logD assessment, the freeware MedChem Designer and ClogP. The dataset was split into two classes according to percentage of fraction absorbed (%FA) - class 1 including drugs with high to medium absorption levels and class 2 including poorly absorbed drugs. The FLI and FLI© (ClogP based FLI) drug-like range covers 93% and 90 % of class 1 drugs, respectively. The dependence of the degree of ionization to intrinsic lipophilicity within the FLI (FLI©) drug-like range as well as the inter-relation between the other Ro5 properties (Mw, HD, HA) was explored, so as to define drug-like / non drug-like combinations as a safer alternative to single properties for drug candidates’ prioritization. In this sense we propose a combined metric of Mw and number of polar atoms (Mw/NO) to account for both size and polarity. Setting the value 50 as cut off, a distinct differentiation between class 1 and class 2 drugs was obtained with Mw/NO>50 for more than 70% of class 1 drugs, while the opposite was observed for class 2 drugs.

Methodical approach for determination of the heterocyclic aromatic amines in meat products using HPLC–MS/MS

Heterocyclic aromatic amines (HAA) are formed in foods of animal origin during the Maillard reaction due to the high creatine and creatinine contents. HAA have carcinogenic and mutagenic effects. HAA content is not standardized in the Russian Federation and the Customs Union territory. However, in the EU countries, comprehensive monitoring studies are carried out on the HAA contents and effect on the human body. Due to constant expansion of the list of controlled contaminants in food products, analytical laboratories need to develop methods for determining HAA in food items. As a result of the research, a method for HAA determination was developed using high-performance liquid chromatography with mass spectrometry in the mode of specified reaction monitoring. Comparative tests of the two methods for sample preparation were carried out. The advantages and disadvantages of sample preparation approaches were substantiated. The existing SPE conditions were optimized, which made it possible to concentrate trace amounts of MeIQx and PhIP and to dispose of substances suppressing analyte ionization. The estimation of method accuracy and specificity was carried out. The degree of ionization suppression by the matrix for MeIQx and PhIP analytes was determined. The degree of HAA extraction was empirically established. For biological samples of animal origin, it was up to 90.9% for MeIQx and up to 89.4% for PhIP. It is shown that, in accordance with the developed methodology, HAA may be determined with an accuracy of 96.15 to 98.4% at the levels of 5 to 20 ng/g. The limit of quantification of the target substances was 3 ng/g.

Reaction of Chalcones with Cellular Thiols. The Effect of the 4-Substitution of Chalcones and Protonation State of the Thiols on the Addition Process. Diastereoselective Thiol Addition

Several biological effects of chalcones have been reported to be associated with their thiol reactivity. In vivo, the reactions can result in the formation of small-molecule or protein thiol adducts. Both types of reactions can play a role in the biological effects of this class of compounds. Progress of the reaction of 4-methyl- and 4-methoxychalcone with glutathione and N-acetylcysteine was studied by the HPLC-UV-VIS method. The reactions were conducted under three different pH conditions. HPLC-MS measurements confirmed the structure of the formed adducts. The chalcones reacted with both thiols under all incubation conditions. The initial rate and composition of the equilibrium mixtures depended on the ratio of the deprotonated form of the thiols. In the reaction of 4-methoxychalcone with N-acetylcysteine under strongly basic conditions, transformation of the kinetic adduct into the thermodynamically more stable one was observed. Addition of S-protonated N-acetylcysteine onto the polar double bonds of the chalcones showed different degrees of diastereoselectivity. Both chalcones showed a Michael-type addition reaction with the ionized and non-ionized forms of the investigated thiols. The initial reactivity of the chalcones and the equilibrium composition of the incubates showed a positive correlation with the degree of ionization of the thiols. Conversions showed systematic differences under each set of conditions. The observed differences can hint at the difference in reported biological actions of 4-methyl- and 4-methoxy-substituted chalcones.

Complexes with Atomic Gold Ions: Efficient Bis-Ligand Formation

Complexes of atomic gold with a variety of ligands have been formed by passing helium nanodroplets (HNDs) through two pickup cells containing gold vapor and the vapor of another dopant, namely a rare gas, a diatomic molecule (H2, N2, O2, I2, P2), or various polyatomic molecules (H2O, CO2, SF6, C6H6, adamantane, imidazole, dicyclopentadiene, and fullerene). The doped HNDs were irradiated by electrons; ensuing cations were identified in a high-resolution mass spectrometer. Anions were detected for benzene, dicyclopentadiene, and fullerene. For most ligands L, the abundance distribution of AuLn+ versus size n displays a remarkable enhancement at n = 2. The propensity towards bis-ligand formation is attributed to the formation of covalent bonds in Au+L2 which adopt a dumbbell structure, L-Au+-L, as previously found for L = Xe and C60. Another interesting observation is the effect of gold on the degree of ionization-induced intramolecular fragmentation. For most systems gold enhances the fragmentation, i.e., intramolecular fragmentation in AuLn+ is larger than in pure Ln+. Hydrogen, on the other hand, behaves differently, as intramolecular fragmentation in Au(H2)n+ is weaker than in pure (H2)n+ by an order of magnitude.

LIPOPHILICITY, AQUEOUS SOLUBILITY, AND DEGREE OF IONIZATION OF ATRACTYLODIN AND β-EUDESMOL, THE BIOACTIVE COMPOUNDS ISOLATED FROM ATRACTYLODES LANCEA

Objective: The study aimed to evaluate the critical physicochemical properties (lipophilicity, aqueous solubility, and degree of ionization) of atractylodin and β-eudesmol using in vitro testing. Methods: Lipophilicity (Log P and Log D) was determined using the shake-flask method (n-octanol/water partition). Aqueous solubility was determined using kinetic solubility assay in media with pH ranging from 1.2 to 7.4. The degree of ionization (pKa) was determined using the potentiometric titration method. Results: Log P and Log D values of 3.0-5.0 suggested moderate lipophilicity of both compounds. Both exhibited low aqueous solubility over the investigated pH range (0.08-0.93 and 1.97-32.48 μg/ml for atractylodin and β-eudesmol, respectively). Based on the pKa values of 9.63 (atractylodin) and 9.12 (b-eudesmol), both are classified as basidic compounds. Conclusion: Atractylodin and β-eudesmol are classified as BCS class II drugs. The physicochemical parameters of both compounds obtained from the current study will be further applied for in silico prediction of their ADME (absorption, distribution, metabolism, and excretion) properties. In addition, PBPK modeling will be used for the prediction of optimal dose regimens of the capsule formulation of the standardized extract of Atractylodes lancea for first-in-human (FIH) and phase II studies in patients with cholangiocarcinoma.

pH/Thermo-Responsive Grafted Alginate-Based SiO2 Hybrid Nanocarrier/Hydrogel Drug Delivery Systems

We report the preparation of mesoporous silica nanoparticles covered by layer by layer (LbL) oppositely charged weak polyelectrolytes, comprising poly(allylamine hydrochloride) (PAH) and a sodium alginate, highly grafted by N-isopropylacrylamide/N-tert-butylacrylamide random copolymers, NaALG-g-P(NIPAM90-co-NtBAM10) (NaALG-g). Thanks to the pH dependence of the degree of ionization of the polyelectrolytes and the LCST-type thermosensitivity of the grafting chains of the NaALG-g, the as-prepared hybrid nanoparticles (hNP) exhibit pH/thermo-responsive drug delivery capabilities. The release kinetics of rhodamine B (RB, model drug) can be controlled by the number of PAH/NaALG-g bilayers and more importantly by the environmental conditions, namely, pH and temperature. As observed, the increase of pH and/or temperature accelerates the RB release under sink conditions. The same NaALG-g was used as gelator to fabricate a hNP@NaALG-g hydrogel composite. This formulation forms a viscous solution at room temperature, and it is transformed to a self-assembling hydrogel (sol-gel transition) upon heating at physiological temperature provided that its Tgel was regulated at 30.7 °C, by the NtBAM hydrophobic monomer incorporation in the side chains. It exhibits excellent injectability thanks to its combined thermo- and shear-responsiveness. The hNP@NaALG-g hydrogel composite, encapsulating hNP covered with one bilayer, exhibited pH-responsive sustainable drug delivery. The presented highly tunable drug delivery system (DDS) (hNP and/or composite hydrogel) might be useful for biomedical potential applications.

Fabrication and Mechanical Properties of Cr2AlC MAX Phase Coatings on TiBw/Ti6Al4V Composite Prepared by HiPIMS

The high-power impulse magnetron sputtering (HiPIMS) technique is widely used owing to the high degree of ionization and the ability to synthesize high-quality coatings with a dense structure and smooth morphology. However, limited efforts have been made in the deposition of MAX phase coatings through HiPIMS compared with direct current magnetron sputtering (DCMS), and tailoring of the coatings’ properties by process parameters such as pulse width and frequency is lacking. In this study, the Cr2AlC MAX phase coatings are deposited through HiPIMS on network structured TiBw/Ti6Al4V composite. A comparative study was made to investigate the effect of average power by varying frequency (1.2–1.6 kHz) and pulse width (20–60 μs) on the deposition rate, microstructure, crystal orientation, and current waveforms of Cr2AlC MAX phase coatings. X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscopy (AFM) were used to characterize the deposited coatings. The influence of pulse width was more profound than the frequency in increasing the average power of HiPIMS. The XRD results showed that ex situ annealing converted amorphous Cr-Al-C coatings into polycrystalline Cr2AlC MAX phase. It was noticed that the deposition rate, gas temperature, and roughness of Cr2AlC coatings depend on the average power, and the deposition rate increased from 16.5 to 56.3 nm/min. Moreover, the Cr2AlC MAX phase coatings produced by HiPIMS exhibits the improved hardness and modulus of 19.7 GPa and 286 GPa, with excellent fracture toughness and wear resistance because of dense and column-free morphology as the main characteristic.