An approach to chiral amino acids via reductive amination of ketones: hydride reduction of 1-(S)-phenethyl amine derived Schiff bases of C-protected alpha-keto acids

Various 1-acyl-2,4,10-trioxaadamantanes were prepared from the corresponding 1-methoxycarbonyl derivatives, via conversion to the N-acylpiperidine derivatives followed by reaction with a Grignard reagent in refluxing THF. These alpha-keto orthoformates were converted to the corresponding imines with 1-(S)-phenethyl amine (TiCl4/Et3N/toluene/reflux), with the Schiff bases being reduced further with NaBH4 (MeOH/0 degrees C) into the corresponding 1-(S)-phenethyl amines (diastereomeric excess 91:9 by NMR). Hydrogenolysis of the phenethyl group (Pd-C/MeOH) finally led to the 1-(aminoalkyl)trioxaadamantanes, which are chiral C-protected alpha-amino acids, in excellent overall yields. (C) 2012 Elsevier Ltd. All rights reserved.

Cellular uptake and remarkable photocytotoxicity of pyrenylter pyridine oxovanadium(IV) complexes of dipyridophenazine bases

Pyrenylterpyridine (pytpy) oxovanadium(IV) complexes VO(pytpy)(L)]Cl-2 (1-6) of the dipyridophenazine bases (L), viz., dipyrido-6,7,8,9-tetrahydrophenazine (dpqC in 1), dipyrido3,2-a:2',3'-c]phenazine-2-carboxylic acid (dppzc in 2), dipyrido3,2-a:2',3'-c]phenazine-11-sulfonic acid (dppzs in 3), 7-aminodipyrido3,2-a:2',3'-c]phenazine (dppza in 4), benzo-i]dipyrido3,2-a:2',3'-c]phenazine (dppn in 5) and dipyrido3,2-a:2',3'-c]phenazine (dppz in 6) were prepared, characterized and their DNA binding, photocleavage activity and photocytotoxicity studied. The complexes which showed a d-d band near 750 nm in DMF are efficient binders to calf thymus DNA (K-b: 3.2 x 10(5)-2.9 x 10(6) M-1). The complexes showed significant pUC19 DNA cleavage in near-IR light of 785 nm forming center dot OH radicals and photocytotoxicity in HeLa cells in visible light with the benzo-i] dipyrido3,2-a:2',3'-c]phenazine complex 5 showing a remarkably low IC50 value of 0.036 mu M. Flow-cytometric analysis shows a high sub-G1 phase cell cycle arrest in HeLa cells by the complexes on photo-irradiation. The photocytotoxicity correlates well with the hydrophobicity, photosensitizing ability and DNA binding propensity of the complexes. (C) 2012 Elsevier B.V. All rights reserved.

Optimal sparsifying bases for frequency-domain optical-coherence tomography

We address the reconstruction problem in frequency-domain optical-coherence tomography (FDOCT) from under-sampled measurements within the framework of compressed sensing (CS). Specifically, we propose optimal sparsifying bases for accurate reconstruction by analyzing the backscattered signal model. Although one might expect Fourier bases to be optimal for the FDOCT reconstruction problem, it turns out that the optimal sparsifying bases are windowed cosine functions where the window is the magnitude spectrum of the laser source. Further, the windowed cosine bases can be phase locked, which allows one to obtain higher accuracy in reconstruction. We present experimental validations on real data. The findings reported in this Letter are useful for optimal dictionary design within the framework of CS-FDOCT. (C) 2012 Optical Society of America

Operator-splitting finite element algorithms for computations of high-dimensional parabolic problems

An operator-splitting finite element method for solving high-dimensional parabolic equations is presented. The stability and the error estimates are derived for the proposed numerical scheme. Furthermore, two variants of fully-practical operator-splitting finite element algorithms based on the quadrature points and the nodal points, respectively, are presented. Both the quadrature and the nodal point based operator-splitting algorithms are validated using a three-dimensional (3D) test problem. The numerical results obtained with the full 3D computations and the operator-split 2D + 1D computations are found to be in a good agreement with the analytical solution. Further, the optimal order of convergence is obtained in both variants of the operator-splitting algorithms. (C) 2012 Elsevier Inc. All rights reserved.

Riesz transforms and multipliers for the Grushin operator

We show that Riesz transforms associated to the Grushin operator G = -Delta - |x|(2 similar to) (t) (2) are bounded on L (p) (a''e (n+1)). We also establish an analogue of the Hormander-Mihlin Multiplier Theorem and study Bochner-Riesz means associated to the Grushin operator. The main tools used are Littlewood-Paley theory and an operator-valued Fourier multiplier theorem due to L. Weis.

Photocytotoxic ferrocene-appended (L-tyrosine)copper(II) complexes of phenanthroline bases

Copper(II) complexes of ferrocene(Fc)-conjugated reduced Schiff base of L-tyrosine (Fc-TyrH), viz., Cu(Fc-Tyr)(L)](ClO4), where L is 1,10-phenanthroline (phen, 1), dipyrido3,2-d:2',3'-f]quinoxaline (dpq, 2), dipyrido3,2-a:2',3'-c]phenazine (dppz, 3) and 2-(naphthalen-1-yl)-1H-imidazo4,5-f]1,10]phenanthroline (nip, 4), were prepared and tested for their photocytotoxicity in cancer cells. Cu(Fc-Phe)(phen)](-ClO4) (5) of L-phenylalanine and Cu(Ph-Tyr)(L)(ClO4)] of the reduced Schiff base Ph-TyrH derived from benzaldehyde and L-tyrosine having phen (6) and dppz (7), and Cu(Ph-Phe)(phen)(ClO4)] (8) using L-phenylalanine were prepared and used as controls. Complexes 5 and 6 were structurally characterized by X-ray crystallography. A copper(II)-based d-d band near 600 nm and a ferrocenyl band at similar to 450 nm were observed in DMF-Tris-HCI buffer (1:4 v/v) in respective complexes. The complexes are photocleavers of pUC19 DNA in visible light forming (OH)-O-center dot radicals. They are cytotoxic in HeLa (human cervical cancer) and MCF-7 (human breast cancer) cells showing an enhancement of cytotoxicity in visible light. Fluorescence imaging shows nuclear localization of the complexes.

Reduced Grobner bases and Macaulay-Buchberger Basis Theorem over Noetherian rings

In this paper, we extend the characterization of Zx]/(f), where f is an element of Zx] to be a free Z-module to multivariate polynomial rings over any commutative Noetherian ring, A. The characterization allows us to extend the Grobner basis method of computing a k-vector space basis of residue class polynomial rings over a field k (Macaulay-Buchberger Basis Theorem) to rings, i.e. Ax(1), ... , x(n)]/a, where a subset of Ax(1), ... , x(n)] is an ideal. We give some insights into the characterization for two special cases, when A = Z and A = ktheta(1), ... , theta(m)]. As an application of this characterization, we show that the concept of Border bases can be extended to rings when the corresponding residue class ring is a finitely generated, free A-module. (C) 2014 Elsevier B.V. All rights reserved.

Oxovanadium(IV) catecholates of terpyridine bases for cellular imaging and photocytotoxicity in red light

Oxovanadium(IV) catecholates of terpyridyl bases, viz. VO(cat)(L)] (L - phtpy, 1; stpy, 2) and VO(dopa-NBD)(L)] (L = phtpy, 3; stpy, 4), where cat is benzene-1,2-diolate, dopa-NBD is 4-(2-(4-nitrobenzoc]1,2,5]oxadiazol-7-ylamino)ethyl)benzene-1,2-di olate, phtpy is (4'-phenyl)-2,2':6',2 `'-terpyridine and stpy is (2,2':6',2 `'-terpyridin-4'-oxy)ethyl-beta-D-glucopyranoside, were prepared and characterized, and their DNA binding, DNA photo-cleavage activity, photocytotoxicity in red light (600-720 nm), cellular uptake and intracellular localization behaviour were studied. The complexes showed an intense ligand-to-metal charge transfer (LMCT) band at similar to 500 nm. The sugar appended complexes 2 and 4 showed significant uptake into the cancer cells. The dopa-NBD complexes 3 and 4 showing green emission were used for cellular imaging. The complexes showed diffused cellular localization mainly in the cytosol and to a lesser extent into the nucleus as evidenced from the confocal microscopy study. Complexes 1-4 showed significant photocytotoxicity in the PDT spectral window giving low IC50 values, while remaining relatively non-toxic in dark.

Improved quasiparticle wave functions and mean field for G(0)W(0) calculations: Initialization with the COHSEX operator

The GW approximation to the electron self-energy has become a standard method for ab initio calculation of excited-state properties of condensed-matter systems. In many calculations, the G W self-energy operator, E, is taken to be diagonal in the density functional theory (DFT) Kohn-Sham basis within the G0 W0 scheme. However, there are known situations in which this diagonal Go Wo approximation starting from DFT is inadequate. We present two schemes to resolve such problems. The first, which we called sc-COHSEX-PG W, involves construction of an improved mean field using the static limit of GW, known as COHSEX (Coulomb hole and screened exchange), which is significantly simpler to treat than GW W. In this scheme, frequency-dependent self energy E(N), is constructed and taken to be diagonal in the COHSEX orbitals after the system is solved self-consistently within this formalism. The second method is called off diagonal-COHSEX G W (od-COHSEX-PG W). In this method, one does not self-consistently change the mean-field starting point but diagonalizes the COHSEX Hamiltonian within the Kohn-Sham basis to obtain quasiparticle wave functions and uses the resulting orbitals to construct the G W E in the diagonal form. We apply both methods to a molecular system, silane, and to two bulk systems, Si and Ge under pressure. For silane, both methods give good quasiparticle wave functions and energies. Both methods give good band gaps for bulk silicon and maintain good agreement with experiment. Further, the sc-COHSEX-PGW method solves the qualitatively incorrect DFT mean-field starting point (having a band overlap) in bulk Ge under pressure.

DIMENSION FREE BOUNDEDNESS OF RIESZ TRANSFORMS FOR THE GRUSHIN OPERATOR

Let G = -Delta(xi) - vertical bar xi vertical bar(2) partial derivative(2)/partial derivative eta(2) be the Grushin operator on R-n x R. We prove that the Riesz transforms associated to this operator are bounded on L-p(Rn+1), 1 < p < infinity, and their norms are independent of dimension n.

An interior penalty method for distributed optimal control problems governed by the biharmonic operator

In this paper, a C-0 interior penalty method has been proposed and analyzed for distributed optimal control problems governed by the biharmonic operator. The state and adjoint variables are discretized using continuous piecewise quadratic finite elements while the control variable is discretized using piecewise constant approximations. A priori and a posteriori error estimates are derived for the state, adjoint and control variables under minimal regularity assumptions. Numerical results justify the theoretical results obtained. The a posteriori error estimators are useful in adaptive finite element approximation and the numerical results indicate that the sharp error estimators work efficiently in guiding the mesh refinement. (C) 2014 Elsevier Ltd. All rights reserved.

Remarkable visible light-triggered cytotoxicity of mitochondria targeting mixed-ligand cobalt(III) complexes of curcumin and phenanthroline bases binding to human serum albumin

Six new mixed-ligand cobalt(III) complexes of formulation Co(N-N)(2)(O-O)](ClO4)(2) (1-6), where N-N is a N,N-donor phenanthroline base, namely, 1,10-phenanthroline (phen in 1, 2), dipyrido3,2-d:2',3'-f] quinoxaline (dpq in 3, 4), and dipyrido3,2-a:2',3'-c]phenazine (dppz in 5, 6), O-O is acetylacetonate (acac in 1, 3, 5) or curcumin (bis(4-hydroxy-3-methoxyphenyl)-1,6-diene-3,5-dione, cur in 2, 4, 6), have been synthesized and characterized. The X-ray crystal structures of complex 1 (as PF6- salt, 1a) and 3 show distorted octahedral geometries formed by the CoN4O2 core. The complexes 1, 3 and 5 having the simple acac ligand are prepared as control species to understand the role of curcumin. The optimized geometries and the frontier orbitals of the curcumin complexes 2, 4, and 6 are obtained from the DFT calculations. The complexes 2, 4, and 6 having the photoactive curcumin moiety display an absorption band in the visible region near 420 nm and show remarkable photocytotoxicity in HeLa cancer cells with respective IC50 values of 7.4 mu M, 5.1 mu M and 1.6 mu M while being much less toxic in dark. MTT assay using complex 6 shows that it is not significantly photocytotoxic to MCF-10A normal cells. The control complexes having the acac ligand are non-toxic both in the presence and absence of light. The cell death is apoptotic in nature and triggered by the photogeneration of reactive oxygen species. Fluorescence imaging experiments on HeLa cells reveals that complex 6 accumulated primarily inside the mitochondria. Human serum albumin (HSA) binding experiments show that the complexes bind HSA with good affinity, but 6 binds with the highest affinity, with a K-b value of 9.8 x 10(5) M-1. Thus, complex 6 with its negligible toxicity in the dark and in normal cells but remarkable toxicity in visible light holds significant photochemotherapeutic potential.

L-p estimates for the wave equation associated to the Grushin operator

We prove that the solution of the wave equation associated to the Grushin operator G = -Delta -vertical bar x vertical bar(2)partial derivative(2)(t) is bounded on L-P (Rn+1), with 1 < p < infinity, when vertical bar 1/p - 1/2 vertical bar < 1/n+2.

A comparative study of a direct discretization and an operator-splitting solver for population balance systems

A direct discretization approach and an operator-splitting scheme are applied for the numerical simulation of a population balance system which models the synthesis of urea with a uni-variate population. The problem is formulated in axisymmetric form and the setup is chosen such that a steady state is reached. Both solvers are assessed with respect to the accuracy of the results, where experimental data are used for comparison, and the efficiency of the simulations. Depending on the goal of simulations, to track the evolution of the process accurately or to reach the steady state fast, recommendations for the choice of the solver are given. (C) 2015 Elsevier Ltd. All rights reserved.

Photoinduced DNA Crosslink Formation by Dichloridooxidovanadium(IV) Complexes of Polypyridyl Bases

Oxidovanadium(IV) complexes VO(pyphen)Cl-2] (1) and VO(pydppz)Cl-2] (2), where pyphen is 2-(2-pyridyl)-1,10-phenanthroline and pydppz is 3-(pyridin-2-yl)dipyrido3,2-a:2,3-c]phenazine, show remarkable photoinduced DNA crosslinking ability and photocytotoxicity. The complexes are non-electrolytes in DMF, 1:1 electrolytes in 20% aqueous DMF, and 1:2 electrolytes in 20% aqueous DMF upon photoirradiation with visible light of 400-700 nm. The paramagnetic complexes, which have one unpaired electron, show a d-d band near 780 nm in aqueous DMF. The IR data suggest a V=O moiety trans to a V-N bond. Complex VO(pydppz)Cl-2] (2), as a novel photoinducible nuclear ds-DNA crosslinking agent, shows visible-light-induced cytotoxicity in HeLa and MCF-7 cancer cells by an apoptotic pathway, giving IC50 values of 0.87 +/- 0.07 and 1.4 +/- 0.2 M, respectively, while being essentially nontoxic (IC50 > 40 M) in the dark and less toxic in normal MCF-10A cells.