Metal–organic framework of amine‐MIL‐53(Al) as active and reusable liquid‐phase reaction inductor for multicomponent condensation of Ugi‐type reactions

Metal–organic framework of NH₂‐MIL‐53(Al), with coordinative unsaturated aluminium sites, has been shown to be active in the Groebke–Blackburn–Bienaymé multicomponent coupling reaction based on Ugi‐type amine and aldehyde condensation over isocyanide and then a cyclization process. Interestingly this reaction occurred under solvent‐free conditions with high yield, in which the NH₂‐MIL‐53(Al) could be recovered and reused for five reaction cycles, giving a total turnover number of 455.     

Lewis acid-base surface interaction of some boron compounds with N-doped graphene; first principles study

We studied density functional theory (DFT) calculations in terms of energetic and electronic properties toward adsorption of some boron compounds (B(OCH₃)₃, BF₃ and BC1₃) on the surface of pristine as well as N-doped graphene using WB97XD/6-31 + G(d,p) level of theory. The net charge transfer of mentioned molecules on the surface of pristine and N-doped graphene was calculated with above-mentioned basis set using natural bond orbital and Mulliken charge analysis during complex formation. The computed dipole moment shows when above-mentioned molecules approach to the surface of N-doped graphene, the amount of the dielectric (μD) will change depending on the kind of molecule. Our calculations reveal that N-doped graphene system has much higher adsorption energy, higher net charge transfer value than pristine graphene due to Lewis acid-base interaction. Comparing B(OCH₃)₃ as an organic boron derivative with boron trihalides (BF₃ and BCl₃), the Lewis acidity increases in the order of BF₃ < BC1₃< B(OCH₃)₃ with adsorption energies (E_ads) of −8.7, −18.3 and −26.5 kJ/mol (BSSE) respectively, while low adsorption energies were calculated on pristine graphene for mentioned molecules.     

Is the rigid-body assumption reasonable?: Insights into the effects of dynamics on the electrostatic analysis of barnase-barstar

Electrostatically-driven association of proteins is important to many biological functions, and understanding which amino acid residues contribute to these interactions is crucial to protein design. Theoretical calculations that are used to elucidate the role of electrostatics in association are typically based on a single experimentally determined protein structure, while an underlying rigid-body assumption is adopted. The goal of this study was to investigate the role of conformational fluctuations on electrostatic interaction energies, as applied to the electrostatic analysis of barnase-barstar. For our calculations, we apply theoretical alanine-scan mutagenesis to introduce charge perturbations by replacing every ionizable residue with alanine, one at a time. Electrostatic clustering and free energy calculations based on the Poisson-Boltzmann method are used to evaluate the effects of each perturbation. Molecular dynamics simulations are performed for the barnase-barstar parent complex and seven experimental alanine mutations from the literature, in order to introduce relaxation before and after mutation. We discuss the effects of dynamics, in the form of pre- and post-mutation relaxation, on electrostatic clustering and free energies of association in light of experimental data. We also examine the utility of nine electrostatic similarity methods for clustering of barnase alanine-scan mutants. Our calculations suggest that the rigid-body assumption is reasonable for electrostatic calculations of barnase-barstar.     

Instance-optimality in probability with an -minimization decoder

Let Φ(ω), ωΩ, be a family of n×N random matrices whose entries _i,j are independent realizations of a symmetric, real random variable η with expectation WB3-4W7J14W-1-W/0?wchp=dGLbVzW-zSkzS" alt="View the MathML source" title="View the MathML source" align="absbottom" border="0" height=13 width="45"/> and variance WB3-4W7J14W-1-X/0?wchp=dGLbVzW-zSkzS" alt="View the MathML source" title="View the MathML source" align="absbottom" border="0" height=16 width="64"/>. Such matrices are used in compressed sensing to encode a vector WB3-4W7J14W-1-Y/0?wchp=dGLbVzW-zSkzS" alt="View the MathML source" title="View the MathML source" align="absbottom" border="0" height=13 width="43"/> by y=Φx. The information y holds about x is extracted by using a decoder WB3-4W7J14W-1-3/0?wchp=dGLbVzW-zSkzS" alt="View the MathML source" title="View the MathML source" align="absbottom" border="0" height=13 width="79"/>. The most prominent decoder is the ℓ₁-minimization decoder Δ which gives for a given WB3-4W7J14W-1-5/0?wchp=dGLbVzW-zSkzS" alt="View the MathML source" title="View the MathML source" align="absbottom" border="0" height=14 width="42"/> the element WB3-4W7J14W-1-6/0?wchp=dGLbVzW-zSkzS" alt="View the MathML source" title="View the MathML source" align="absbottom" border="0" height=16 width="65"/> which has minimal ℓ₁-norm among all WB3-4W7J14W-1-8/0?wchp=dGLbVzW-zSkzS" alt="View the MathML source" title="View the MathML source" align="absbottom" border="0" height=13 width="43"/> with Φz=y. This paper is interested in properties of the random family Φ(ω) which guarantee that the vector WB3-4W7J14W-1-C/0?wchp=dGLbVzW-zSkzS" alt="View the MathML source" title="View the MathML source" align="absbottom" border="0" height=14 width="70"/> will with high probability approximate x in WB3-4W7J14W-1-D/0?wchp=dGLbVzW-zSkzS" alt="View the MathML source" title="View the MathML source" align="absbottom" border="0" height=18 width="17"/> to an accuracy comparable with the best k-term error of approximation in WB3-4W7J14W-1-G/0?wchp=dGLbVzW-zSkzS" alt="View the MathML source" title="View the MathML source" align="absbottom" border="0" height=18 width="17"/> for the range kan/log₂(N/n). This means that for the above range of k, for each signal WB3-4W7J14W-1-J/0?wchp=dGLbVzW-zSkzS" alt="View the MathML source" title="View the MathML source" align="absbottom" border="0" height=13 width="43"/>, the vector WB3-4W7J14W-1-K/0?wchp=dGLbVzW-zSkzS" alt="View the MathML source" title="View the MathML source" align="absbottom" border="0" height=14 width="70"/> satisfies

WB3-4W7J14W-1-M/0?wchp=dGLbVzW-zSkzS" alt="View the MathML source" title="View the MathML source">

with high probability on the draw of Φ. Here, Σ_k consists of all vectors with at most k nonzero coordinates. The first result of this type was proved by Wojtaszczyk [P. Wojtaszczyk, Stability and instance optimality for Gaussian measurements in compressed sensing, Found. Comput. Math., in press] who showed this property when η is a normalized Gaussian random variable. We extend this property to more general random variables, including the particular case where η is the Bernoulli random variable which takes the values WB3-4W7J14W-1-P/0?wchp=dGLbVzW-zSkzS" alt="View the MathML source" title="View the MathML source" align="absbottom" border="0" height=15 width="46"/> with equal probability. The proofs of our results use geometric mapping properties of such random matrices some of which were recently obtained in [A. Litvak, A. Pajor, M. Rudelson, N. Tomczak-Jaegermann, Smallest singular value of random matrices and geometry of random polytopes, Adv. Math. 195 (2005) 491–523].     

Accelerating gradient projection methods for -constrained signal recovery by steplength selection rules

We propose a new gradient projection algorithm that compares favorably with the fastest algorithms available to date for ℓ₁-constrained sparse recovery from noisy data, both in the compressed sensing and inverse problem frameworks. The method exploits a line-search along the feasible direction and an adaptive steplength selection based on recent strategies for the alternation of the well-known Barzilai–Borwein rules. The convergence of the proposed approach is discussed and a computational study on both well conditioned and ill-conditioned problems is carried out for performance evaluations in comparison with five other algorithms proposed in the literature.     

Novel Antifungal Antibiotic, WB Produced by the Fungus Strain 38

InthecourseofourscreeningnewantifungalantibioticsusingPyriculariaoryzaeasindicatorstrain,wehavepreviouslyreportedseveralcompoundssuchasWAandA73.Inthecontinuation,wehaverecentlyisolatedanove1antifungalcompoundfromthemetabolitesofthesoilfungusstrain38l.Taxonomy,fermentation,isolationandbiologicalpropertiesofWBwillbereportedinanotherpaper.InthispaPer,wereportthephysico-chendcalpropertiesandstructureelucidationofthenoveIantifungaIcompoundWB.WBwasobtainedasyellowpowder.Itsmolecularformula,C19…     

The analysis of N-glycolylneuraminic acid(NeuGc) of hepatoma tissue and K562 cell ferritins using HPLC and mass spectrometry

Ferritin is an iron-storage protein and its serum level is known to increase in the patient of with inflammation and malignant tumor. To further elucidate the difference between ferritins from normal human liver tissue and that of cancer cells, their sialic acids were analyzed. The Western blot analysis and the cytochemical staining using anti-NeuGc antiserum indicated that ferritins from the human hepatocarcinoma tissue and malignant K562 cells contain NeuGc, but that from the normal liver does not. The result was also confirmed by HPLC analysis and MALDI-TOF/MS analysis of sialic acids which were derivatized by the DMB method. It was also shown that the sialic acid content in hepatocarcinoma ferritin was much higher than that in the normal liver ferritin. These results suggest that normal and cancerous liver ferritins are qualitatively and quantitatively different in sialylation. In addition, K562 cells were shown to express NeuGc even if the cells were cultured in serum-free media which lack NeuGc. This is of interest from the current concept that expression of NeuGc in human cells is due to uptake and utilization of exogenous NeuGc.     

Crystal growth of the quasi-one dimensional spin-magnet LiCuVO4

The phase relationships in the Li–Cu–V–O and Li–Cu–V–O–Cl systems were investigated and the phase diagrams determined. Based on these diagrams single crystals of the low-dimensional spin compound LiCuVO₄ with maximal dimensions up to 12×3×3 mm³ were grown from a solution of LiCuVO₄ in a LiVO₃ or a LiVO₃–LiCl melt. The stoichiometry of the grown crystals is discussed.