Saturated Commutative Spaces of Heisenberg Type

In this paper, we give a partial classification of commutative spaces of Heisenberg type. Several classification results were known previously. In order to avoid complicated technical details, we restrict ourselves to saturated commutative spaces. Our results are presented in Table II.     

Large Deviation Probabilities for Square-Gaussian Stochastic Processes

We investigate properties of square-Gaussian stochastic processes. These processes are formed by quadratic forms of Gaussian processes or by limits in the mean square of quadratic forms of Gaussian processes. Special classes of these processes are determined and investigated. For processes from these classes estimates of large deviation probability are obtained. These estimates we use to estimate the probability that Gaussian vector-valued process leave some region on some interval of time. We construct asymptotic confidence regions for estimates of covariance functions of vector-valued Gaussian processes. Criterion of hypothesis testing on covariance functions of these processes is constructed.     

Novel solvable many-body problems

Novel classes of dynamical systems are introduced, including many-body problems characterized by nonlinear equations of motion of Newtonian type (“acceleration equals forces”) which determine the motion of points in the complex plane. These models are solvable, namely their con?guration at any time can be obtained from the initial data by algebraic operations, amounting to the determination of the zeros of a known time-dependent polynomial in the independent variable z. Some of these models are multiply periodic, isochronous or asymptotically isochronous; others display scattering phenomena.     

Mechanistic studies of UV assisted [4 + 2] cycloadditions in synthetic efforts toward vibsanin E

Quantum chemical DFT calculations at the B3LYP/6-31G(d) level have been used to study the stereochemical course of the photochemical cycloaddition of enone 9 with dienes. The observed products of this photochemically induced cycloaddition showed a stereoselectivity, which is opposite to what would be expected by FMO considerations. The quantum chemical calculations revealed that the unusual stereoselectivity of the reaction can be rationalized by assuming a stereospecific photochemical cis-trans isomerization of enone 9 to trans isomer 9a followed by a thermal Diels-Alder reaction of the diene onto the highly reactive trans enone. The photochemical reaction step involves the selective formation of a twisted triplet intermediate, which accounts for the selectivity of the reaction.     

New evidence of appropriate fruit juice redox conditions for citric acid acting as a proton-carrier on Pt electrode: the effect on evaluating antioxidant properties

Journal of Solid State Electrochemistry - Recent scientific data in respect of the different effect of citric acid on antioxidant activity of plant polyphenols in pure solutions (no polyphenol...     

Synthesis of new-type 1,3,6-triazocine via intramolecular reactions of iodocyclization and [3+2] azido cycloaddition

Selective iodocyclization of 6-(alkenylamino)-1-allylpyrazolo[3,4-d]pyrimidines provided hydrogenated derivatives of 1-allyl-8(9)-iodomethylimidazo(pyrimido)[1,2-a]pyrazolo[4,3-e]pyrimidines which were further reacted with NaN₃ at 75°С to 80°С to give a series of new-type 1,3,6-triazocines annulated with the pyrazole, pyrimidine, imidazole (or pyrimidine), and 1,2,3-triazole rings. The compounds synthesized were structurally characterized by analytical, spectral (IR, ¹H and ¹³C NMR, HPLC-mass), and X-ray diffraction data.     

Partial Sn‐atom ordering in Sm3Ga0.80–2.48Sn4.20–2.52

Trisamarium digallide tristannide crystallizes with a partially ordered Pu₃Pd₅‐type structure in space group Cmcm. In a single crystal of Sm₃Ga_1.89(4)Sn_3.11(4), the 8g position is mostly occupied by Sn atoms (93% Sn and 7% Ga), while the 4c and 8f positions are occupied by a Ga/Sn statistical mixture. The evolution of the structure as a function of the Ga content has been studied by X‐ray powder diffraction on ten Sm₃Ga_5−xSn_x samples. It is shown that the 8g position remains occupied essentially exclusively by Sn atoms within the whole homogeneity range, with x ranging from 2.52 to 4.20.     

Designed helical peptides inhibit an intramembrane protease

gamma-Secretase cleaves the transmembrane domain of the amyloid precursor protein, a process implicated in the pathogenesis of Alzheimer's disease, and this enzyme is a founding member of an emerging class of intramembrane proteases. Modeling and mutagenesis suggest a helical conformation for the substrate transmembrane domain upon initial interaction with the protease. Moreover, biochemical evidence supports the presence of an initial docking site for substrate on gamma-secretase that is distinct from the active site, a property predicted to be generally true of intramembrane proteases. Here we show that short peptides designed to adopt a helical conformation in solution are inhibitors of gamma-secretase in both cells and enzyme preparations. Helical peptides with all d-amino acids are the most potent inhibitors and represent potential therapeutic leads. Subtle modifications that disrupt helicity also substantially reduce potency, suggesting that this conformation is critical for effective inhibition. Fluorescence lifetime imaging in intact cells demonstrates that helical peptides disrupt binding between substrate and protease, whereas an active site-directed inhibitor does not. These findings are consistent with helical peptides interacting with the initial substrate docking site of gamma-secretase, suggesting a general strategy for the development of potent and specific inhibitors of intramembrane proteases.     

Hole Migration in Telomere-Based Oligonucleotide Anions and G-Quadruplexes

Vacuum ultraviolet photoionization of a gas-phase oligonucleotide anion leads to the formation of a valence hole. This hole migrates towards an energetically favorable site where it can weaken bonds and ultimately lead to bond cleavage. We have studied Vacuum UV photoionization of deprotonated oligonucleotides containing the human telomere sequence dTTAGGG and G-quadruplex structures consisting of four dTGGGGT single strands, stabilized by NH₄⁺ counter ions. The oligonucleotide and G-quadruplex anions were confined in a radiofrequency ion trap, interfaced with a synchrotron beamline and the photofragmentation was studied using time-of-flight mass spectrometry. Oligonucleotide 12-mers containing the 5'-TTAGGG sequence were found to predominantly break in the GGG region, whereas no selective bond cleavage region was observed for the reversed 5'-GGGATT sequence. For G-quadruplex structures, fragmentation was quenched and mostly non-dissociative single and double electron removal was observed.     

Photoelectron spectra of some antibiotic building blocks: 2-azetidinone and thiazolidine-carboxylic Acid

X-ray photoelectron spectra of the core and valence levels of the fundamental building blocks of β-lactam antibiotics have been investigated and compared with theoretical calculations. The spectra of the compounds 2-azetidinone and the 2- and 4-isomers of thiazolidine-carboxylic acid are interpreted in the light of theoretical calculations. The spectra of the two isomers of thiazolidine-carboxylic acid are rather similar, as expected, but show clear effects due to isomerization. Both isomers are analogues of proline, which is well-known to populate several low energy conformers in the gas phase. We have investigated the low energy conformers of thiazolidine-4-carboxylic acid theoretically in more detail and find some spectroscopic evidence that multiple conformers may be present. The measured valence levels are assigned for all three compounds, and the character of the frontier orbitals is identified and analyzed.