New Synthetic Analogs of Retinoids: Synthesis of Aromatic Analogs of 9‐Methylidene‐ and 13‐Demethyl‐9‐methylidene‐retinol, ‐retinal,and Ethyl 13‐Demethyl‐9‐methylideneretinoate

Aromatic analogs of 9‐methylidene and 13‐demethyl‐9‐methylideneretinol, ‐retinal, and ethyl 13‐demethyl‐9‐methylideneretinoate were synthesized via a new β‐methylidene‐aldehyde synthon.     

On the Nonseparable Subspaces of J(η) and C([1, η])

Let η be a regular cardinal. It is proved, among other things, that: (i) if J(η) is the corresponding long James space, then every closed subspace Y ⊆ J(η), with Dens (Y) = η, has a copy of 𝓁₂(η) complemented in J(η); (ii) if Y is a closed subspace of the space of continuous functions C([1, η]), with Dens (Y) = η, then Y has a copy of c₀(η) complemented in C([1, η]). In particular, every nonseparable closed subspace of J(ω₁) (resp. C([1, ω₁])) contains a complemented copy of 𝓁₂(ω₁) (resp.c₀(ω₁)). As consequence, we give examples (J(ω₁), C([1, ω₁]), C(V), V being the “long segment”) of Banach spaces X with the hereditary density property (HDP) (i.e., for every subspace Y ⊆ X we have that Dens (Y) = w*–Dens (Y*)), in spite of these spaces are not weakly Lindelof determined (WLD).     

Exploring the Role of L10 Loop in New Delhi Metallo-β-lactamase (NDM-1): Kinetic and Dynamic Studies

Four NDM-1 mutants (L218T, L221T, L269H and L221T/Y229W) were generated in order to investigate the role of leucines positioned in L10 loop. A detailed kinetic analysis stated that these amino acid substitutions modified the hydrolytic profile of NDM-1 against some β-lactams. Significant reduction of k_cat values of L218T and L221T for carbapenems, cefazolin, cefoxitin and cefepime was observed. The stability of the NDM-1 and its mutants was explored by thermofluor assay in real-time PCR. The determination of T_mB and T_mD demonstrated that NDM-1 and L218T were the most stable enzymes. Molecular dynamic studies were performed to justify the differences observed in the kinetic behavior of the mutants. In particular, L218T fluctuated more than NDM-1 in L10, whereas L221T would seem to cause a drift between residues 75 and 125. L221T/Y229W double mutant exhibited a decrease in the flexibility with respect to L221T, explaining enzyme activity improvement towards some β-lactams. Distances between Zn1-Zn2 and Zn1-OH- or Zn2-OH- remained unaffected in all systems analysed. Significant changes were found between Zn1/Zn2 and first sphere coordination residues.     

20‐Hydroxy­imino‐5α‐pregna‐9(11),16‐dien‐3β‐yl acetate and 17‐oxo‐5α‐androst‐9(11)‐en‐3β‐yl acetate

In the title compounds, C₂₃H₃₃NO₃ and C₂₁H₃₀O₃, respectively, the ester linkage in ring A is equatorial. In these steroids, the six‐membered rings A and B have chair conformations, but ring C can be better described as a half‐chair. The five‐membered ring D adopts a 14α‐envelop conformation. The A/B, B/C and C/D ring junctions are trans.     

Novel Peak Assignments of in VivoC MRS in Human Brain at 1.5 T

¹³C MRS studies at natural abundance and after intravenous 1-¹³C glucose infusion were performed on a 1.5-T clinical scanner in four subjects. Localization to the occipital cortex was achieved by a surface coil. In natural abundance spectra glucose C_3β,5β, myo-inositol, glutamate C_1,2,5, glutamine C_1,2,5, N-acetyl-aspartate C_1-4,C=O, creatine CH₂, CH₃, and C_C=N, taurine C_2,3, bicarbonate HCO⁻₃ were identified. After glucose infusion ¹³C enrichment of glucose C_1α,1β, glutamate C_1-4, glutamine C_1-4, aspartate C_2,3, N-acetyl-aspartate C_2,3, lactate C₃, alanine C₃, and HCO⁻₃ were observed. The observation of ¹³C enrichment of resonances resonating at >150 ppm is an extension of previously published studies and will provide a more precise determination of metabolic rates and substrate decarboxylation in human brain.     

A discrete variable representation study of the dynamics of the double proton transfer in bicyclic oxalamidines

DFT electronic calculations are performed for the double proton transfer in bicyclic oxalamidines 2,2^′-bis-(3,4,5,6-tetrahydro-1,3-diazine) (OA6) and 2,2^′-bis-(4,5,6,7-tetrahydro-1,3-diazepine) (OA7). Bidimensional potential energy surfaces retaining the characteristics of the stationary points located in the whole potential are built to calculate the vibrational levels through the discrete variable representation (DVR) method. Zero-point tunneling splittings are similar for both systems but for a given energy there are much less tunneling doublets available in OA6, this being the key factor responsible for the different temperature dependence of the rate for the two systems.     

Thomas–Fermi approximation for the quasi‐two‐dimensional electron gas

To take into account static correlation effects in the quasi‐two‐dimensional electron gas a screened Coulombic interaction between particles is studied. The Thomas–Fermi approximation is used and the potential screening appears as a function of the Wigner–Seitz density parameter r_s and the effective width t of the system. With the self‐consistent field theory applied to the modified deformable jellium, the ground‐state energy per particle and the conditions for electron localization are obtained in terms of the interparticle distance and the screening parameter μ. A critical minimum characteristic width t_c is obtained; below t_c no long‐range order is obtained. For larger widths a stable localized state is predicted at finite densities. © 2001 John Wiley & Sons, Inc. Int J Quant Chem 82: 269–276, 2001     

The Effect of the Compatibilization Route of PA/PO Blends on the Physico-chemical Phenomena Developing Along a Twin-screw Extruder

The effect of the compatibilization method (ex-situ, in-situ, cross linking) on the chemical conversion, morphological and rheological evolution of polyamide/polyolefin blends along a twin screw extruder is investigated. For this purpose, samples were quickly collected from the extruder at specific barrel locations, quenched and subsequently characterized off-line. While significant changes occur very quickly in the melting zone for the ex-situ and in-situ routes, changes of the cross linking system could be detected along all the extruder. Correlations between chemical conversion, particle size and linear viscoelastic response could be established.