Kinetics of decomposition of the liquid phase of the ternary system LiOH-H2O2-H2O in the presence of the solid phase of Li2O2 · H2O

The kinetics of decomposition of hydrogen peroxide in the liquid phase of the ternary system LiOH-H₂O₂-H₂O was studied in the presence the solid phase of Li₂O₂·H₂O and without it. The main kinetic parameters of the processes studied were determined.     

The Studies of the Reactions of 2, 4, 6-Triphenylpyrylium Tetrafluoroborate with Amino Acids

The reactions of triphenylpyrylium salt 1 with various amino acids were explored and compared. The reactions with most α-amino acids yielded decarboxylation products 2 viadecarboxylation. The reactions with glutamic acid, lysine and ACC (1-aminocyclopropyl-carboxylic acid) gave triphenylpyridine 8, dimer 9 and acid 5a-ace, respectively. The reactionswith β and γ-amino acids yielded triphenylpyridine by intramolecular elimination.     

Measurement of the rate constants for the reactions of the IO• radical with sulfur-containing compounds H2S, (CH3)2S, and SO2

The reactions of iodine monoxide (IO^•) with sulfur-containing compounds, which are important for the atmospheric chemistry, are studied. An attempt is made to distinguish between the heterogeneous and homogeneous reaction pathways. It is shown that, under the experimental conditions, the reactions proceed on the wall and generate iodine atoms into the gas phase. It is found that, at room temperature, the rate constants for the gas-phase reactions of IO^• with (CH₃)₂S and H₂S are lower than 2.5 × 10⁻¹⁴ and 8.0 × 10⁻¹⁴ cm³ molecule⁻¹ s⁻¹, respectively; the rate constant for the gas-phase reaction of iodine monoxide with SO₂ ≤ 5.6 × 10⁻¹⁵ cm³ molecule⁻¹ s⁻¹.     

Acuminatanol, the first 2′,2?-bis-dihydrobiflavonol from the aqueous extract of Trichoscypha acuminata

One new 3′,4′,5′,5,7-pentahydroxy-2′,2?-bis-dihydrobiflavonol, acuminatanol (1), was obtained from the aqueous extract of Trichoscypha acuminata. The structure elucidation process was performed primarily utilizing a capillary scale NMR probe. Acuminatanol (1) is the first example of a bis-dihydroflavonol linked exclusively via the B-rings at C-2′ and C-2? positions. To date, it is the first naturally-occurring compound reported from the genus Trichoscypha, and the first new natural product published from our compound libraries generated from the aqueous extracts of American and African plants.     

Construction of the Skeleton of Phthalascidin, Mechanism of the Formation of the Key Tricyclic Lactam Intermediate

Phthalascidin is a structurally simplified version of Et-743, which is a potent anti-tumor marine natural product isolated from Ecteinascidia turbinata. Its antiproliferative activity is greater than that of the agents taxol, camptothecin, adriamycin, mitomycin C, cisplatin, bleomycin, and etoposide by 1-3 orders of magnitude. An elegant synthesis of Et-743 and phthalascidin has been reported by E. J. Corey and co-workers1,2. As part of our continuing program, we have also engaged in dev…     

The Isomeric Structures of H_2GeLiF, the Prototype Germylenoid

Thepropertiesandreactionsofgermylene,R,Gef,anditsderivativeshavebeenwellstudiedl.Germylenereactions,however,canbeperformedusingintermediatesofthetype.MR'GeMX(M=alkalimetal,X=halogen),analogoustocarbenoidsandsilylenoids,Re'CMXandRR'SiMX2'3.Recently,Gasparandhiscoworkerhavesuggestedthatgermylenoid,Me,GeLiCI,shouldbeinvolvedinthereactionofdichlorodimethylgermanewithsubstitutedbutadiene',butlittleisknownexperimentallyandtheoreticallyaboutitsenergy,geometryorelectronicstructure.Soitisnece…     

A Convenient Method for the Synthesis of Chiral N-Protected 1, 2-Amino Alcohols via the Reduction of the Aminoketones

A series of optically active N-protected 1,2-amino alcohols were synthesized via the reduction of the corresponding α-aminoketones starting from the readily available L-amino acids.     

Influence of the Length of the Alanine Spacer on the Acidic–Basic Properties of the Ac–Lys–(Ala) n –Lys–NH2 Peptides (n?=?0, 1, 2, …, 5)

By using the potentiometric titration method, we have determined the pK _a values of the two terminal lysine groups in six alanine-based peptides differing in the length of the alanine chain: Ac?CLys?CLys?CNH₂ (KK), Ac?CLys?CAla?CLys?CNH₂ (KAK), Ac?CLys?CAla?CAla?CLys?CNH₂ (KAK2), Ac?CLys?CAla?CAla?CAla?CLys?CNH₂ (KAK3), Ac?CLys?CAla?CAla?CAla?CAla?CLys?CNH₂ (KAK4), and Ac?CLys?CAla?CAla?CAla?CAla?CAla?CLys?CNH₂ (KAK5) in aqueous solution. For each compound, the model of two stepwise acid?Cbase equilibria was fitted to the potentiometric-titration data. As expected, the pK _a values of the lysine groups increase with increasing length of the alanine spacer, which means that the influence of the electrostatic field between one charged group on the other decreases with increasing length of the alanine spacer. However, for KAK3, the pK _a1 value (8.20) is unusually small and pK _a2 (11.41) is remarkably greater than pK _a1, suggesting that the two groups are close to each other and, in turn, that a chain-reversal conformation is present for this peptide. Starting with KAK3, the differences between pK _a1 and pK _a2 decrease; however, for the longest peptide (KAK5), the values of pK _a1 and pK _a2 still differ by about 1 unit, i.e., by more than the value of log₁₀ (4)?=?0.60 that is a limiting value for the pK _a difference of dicarboxylic acids with increasing methylene-spacer length. Consequently, some interactions between the two charged groups are present and, in turn, a bent shape occurs even for the longest of the peptides studied.     

Calculated vibrational structure of the first band of the photoelectron spectrum of HO 2 − and the electron affinity of HO2

The vibrational structure of the first band of the photoelectron (PE) spectrum of HO ₂ ^? and DO ₂ ^? has been calculated on the basis of (slightly modified) ab initio potentials. The best agreement with the experimental spectrum of HO ₂ ^? is obtained for a vibrational temperature of ca. 600 K. “Peak D”, which has been under debate in earlier work, is composed of two transitions, with the “hot” transition 3 ₁ ¹ being more intense than the adiabatic transition. Since thev ₂ bending mode of DO₂ has significant OO stretching character, the vibrational structure of the PE spectrum of DO ₂ ^? is more complex than that of HO ₂ ^? . Large-scale RCCSD(T) calculations of the equilibrium electron affinity of HO₂ yield 1.058 eV which agrees with the experimental value of 1.044 ± 0.020 eV.     

Predicting the Impact of Deleterious Mutations in the Protein Kinase Domain of FGFR2 in the Context of Function, Structure, and Pathogenesis—a Bioinformatics Approach

Fibroblast growth factor receptor 2 (FGFR2) controls a wide range of biological functions by regulating the cellular proliferation, survival, migration and differentiation. A growing body of preclinical data demonstrated that deregulation of the FGFR signalling through genetic modification was observed in various types of cancers. However, the extent to which genetic modifications interfere with gene regulation and their involvement in cancer susceptibility remains largely unknown. In this work, we performed in silico profiling of harmful non-synonymous single nucleotide polymorphisms (SNPs) in the protein kinase domain of FGFR2. Tolerance index, position-specific independent count score, change in free energy score (ΔΔG), Eris and FoldX indicated that seven mutations were found to be deleterious and may alter the protein function and structure. Furthermore, based on physico-chemical properties, two mutations K659N and R747H were found to be most deleterious in protein kinase domain and taken for further structural analysis. Docking study showed a complete loss of binding affinity followed by interference in hydrogen bonding and surrounding residues due to K659N and R747H mutations. In order to elucidate the mechanism behind the impact of mutation that can generate a ripple effect throughout the protein structure and ultimately affect the function, in-depth molecular dynamics simulation and principal component analysis were performed. The obtained results indicate that K659N and R747H mutations have a distinct effect on the dynamic behaviour of FGFR2 protein. Our strategy may be helpful for understanding SNP effects on proteins with function and their role in human genetic diseases and for the development of novel pharmacological strategies.