STUDIES ABOUT SYNTHESIS,CHARACTERIZATION, AND THE EFFECT OF 2-n-PROPYL-3-ETHYL-3-METHYL-1,4,2-BENZOXAZA-PHOSPHORINE-2-OXIDE ON GROWTH PARAMETERS AND CHLOROPHYLL CONTENT OF WHEAT

This article presents the synthesis and characterization of a new phosphorus heterocycle, namely 2-n-propyl-3-ethyl-3-methyl-1,4,2-benzoxaza-phosphorine-2-oxide, by a Mannich-type reaction between n-propyl-dichlorophosphine, methyl ethyl ketone, and o-aminophenol.

Taking into consideration that chlorophyll contents in plants were revealed to have connection with nitrogen and phosphorus concentrations at early growth stage, and because the above-mentioned heterocyclic compound can be considered as a phosphonic analogous of naturally occuring α-aminoacids, it was expected to develop biological activity from it. That is the reason why 2-n-propyl-3-ethyl-3-methyl-1,4,2-benzoxaza-phosphorine-2-oxide was subjected for biological tests on wheat.

The present study was also undertaken to investigate the interrelationship between chlorophyll content, dry matter, and other growth parameters of wheat, after treatment with different concentrations of 2-n-propyl-3-ethyl-3-methyl-1,4,2-benzoxaza-phosphorine-2-oxide.     

Determination of gadolinium‐based magnetic resonance imaging contrast agents by micellar electrokinetic capillary chromatography

MEKC with DAD was applied to detect six Gd‐based contrasting agents (CAs) (Gd‐DTPA‐BMA (Omniscan), Gd‐HPDO3A (ProHance), Gd‐DOTA (Dotarem), Gd‐AAZTA, Gd‐BOPTA (Multihance) and Gd‐DTPA (Magnevist)) commonly used in MRI diagnostics. The achieved LODs ranged between 0.40 and 20 μM and the optimized method gave excellent precision, especially when two internal standards were applied (less than 0.34 RSD% for migration time). The MEKC technique made it possible to determine the CAs in urine and serum samples of patients having a therapeutic dose. Due to the SDS content of the running buffer, the serum samples can be directly injected to analyze Gd‐based CAs without interference of high protein content.     

Modelling peptide-metal dication interactions: formamide-Ca(2+) reactions in the gas phase

The collision induced dissociation of formamide-Ca(2+) complexes produced in the gas phase through nanoelectrospray ionization yields as main products ions [CaOH](+), [HCNH](+), [Ca(NH(2))](+), HCO(+) and [Ca(NH(3))](2+) and possibly [Ca(H(2)O)](2+) and [C,O,Ca](2+), the latter being rather minor. The mechanisms behind these fragmentation processes have been established by analyzing the topology of the potential energy surface by means of B3LYP calculations carried out with a core-correlated cc-pWCVTZ basis set. The Ca(2+) complexes formed by formamide itself and formimidic acid play a fundamental role. The former undergoes a charge separation reaction yielding [Ca(NH(2))](+) + HCO(+), and the latter undergoes the most favorable Coulomb explosion yielding [Ca-OH](+) + [HCNH](+) and is the origin of a multistep mechanism which accounts for the observed loss of water and HCN. Conversely, the other isomer of formamide, amino(hydroxyl)carbene, does not play any significant role in the unimolecular reactivity of the doubly charged molecular cation.     

Tailoring the physical properties of some high birefringence isothiocyanato-based liquid crystals

This paper describes the synthesis and characterization of several liquid crystal compounds having a tolane or terphenyl core structure and a high polarizability, isothiocyanato (NCS), terminal group. The synthesized compounds have high optical birefringerce (0.35 and 0.52), the highest being exhibited by the olefin-tolanes. Several eutectic mixtures are formulated and show improved properties over the single compounds, such as a broad nematic range, low melting temperature and relatively high clearing point. The birefringence of these mixtures is in the range 0.35-0.37. UV, viscosity and electro-optical measurements of the synthesized compounds are also reported. Dipole moment and polarizability calculations were made using CS-MOPAC and Hyperchem software computational programmes.     

Effect of Sr2+ association on the tautomerization processes of uracil and its dithio- and diseleno-derivatives

The structures and relative stabilities of the complexes formed by uracil and its thio- and seleno-derivatives with the Sr(2+) cation, in the gas phase, have been analyzed by means of G96LYP density functional theory (DFT) calculations. The attachment of the Sr(2+) cation to the heteroatom at position 4 is preferred systematically. Although the enolic forms of uracil and its derivatives should not be observed in the gas phase, the corresponding Sr(2+) complexes are the most stable. The enhanced stability of these tautomers is two-fold, on the one hand Sr(2+) interacts with two basic sites simultaneously, and on the other hand an aromatization of the six-membered ring takes place upon Sr(2+) association. Sr(2+) attachment also has a clear catalytic effect in the tautomerization processes involving uracil and its derivatives. This catalytic effect increases when oxygen is replaced by sulfur or selenium. The Sr(2+) binding energy with uracil and its derivatives is bigger than the tautomerization barriers connecting the dioxo forms with the corresponding enolic tautomers. Consequently, when associated with Sr(2+), all tautomers are energetically accessible and should all be observed in the gas phase.     

Co-localization of PCNA, VCAM-1 and caspase-3 with nestin in xenografts derived from human anaplastic astrocytoma and glioblastoma multiforme tumor spheres

The cancer stem cell hypothesis proposes that tumors contain a small subset of cancer cells, the cancer stem cells, which constitute a reservoir of self-sustaining cells with the exclusive ability to self-renew and maintain the tumor. Markers that define cancer stem cells that are capable of recapitulating brain tumors as xenografts in mice has not been described. We investigated the relationship between expression of nestin and that of PCNA, VCAM-1 and caspase-3 in the xenografts developed from human anaplastic astrocytoma and glioblastoma tumor-derived spheres in the brain of nude mouse. Xenografts obtained from astrocytoma tumor stem cells (ATSC) and glioblastoma tumor stem cells (GTSC) have showed a large number of cells positive for both PCNA and the nestin, demonstrating that nestin expressing cells have a high rate of proliferation. Xenografts from GTSC showed heterogeneous staining pattern with cells that express both nestin and VCAM-1, whereas others cells remained complete negative. In this case it was noticed that most tumor cells with large or multinucleated nuclei coexpress nestin and VCAM-1. In xenografts from ATSC most cells positive for nestin express VCAM-1 and in this case the two proteins appear to occupy the same cytoplasmic region. Both GTSC and ATSC derived xenografts showed cells positive for both caspase-3 and for nestin detected mainly as single cells and as cell clusters located near or around a blood vessel.     

The geometry of pyrazole: A test for ab initio calculations

Ab initio calculations on the structure of pyrazole have been carried out at different levels of accuracy. At the Hartree-Fock (HF) level, the performance of several basis sets, namely 3-21G, 6-31G, 6-31G**, and 6–311G** was investigated. The influence of electron correlation effects also was studied by carrying out geometry optimizations at the MP2, MP4, and QCISD levels. The performance of a density functional method also was evaluated. We have also investigated the possible influence of the frozen core approximation on the final optimized geometry. Three different statistical analyses were considered in determining which geometry is closest to the experimental microwave geometry—namely Paul Curtin's diagrams, cluster analysis, and multidimensional scaling. From these analyses, we conclude that there is no asymptotic approach to the experimental geometry by increasing the quality of the theoretical model, although, as expected, the more reliable structures are those obtained at the MP2, MP4, and QCISD levels, as well as those obtained by the B3LYP density functional method. We have also found that the values of the rotational constants are a tight criterion to define the quality of a molecular geometry. © 1995 by John Wiley & Sons, Inc.     

19F-19F spin-spin coupling constant surfaces for (HF)2 clusters: the orientation and distance dependence of the sign and magnitude of J(F-F)

Ab initio calculations using the equation-of-motion coupled cluster method have been carried out to investigate 19F-19F spin-spin coupling constants for a pair of HF molecules. The overall features of the J(F-F) coupling surface with respect to the F-F distance and the orientation of the pair of HF molecules reflect those of the Fermi-contact (FC) surface, although the FC term may not be a good quantitative estimate of J(F-F). The hydrogen-bonded HF dimer exhibits unusual behavior compared to other hydrogen-bonded complexes, since both the FC term and 2hJ(F-F) exhibit variations in sign and magnitude as the F-F distance changes and the linearity of the hydrogen bond is destroyed. The FC term for F-F coupling is relative small and negative for the equilibrium dimer. At the dimer F-F distance, the maximum negative value for the FC term is found for the linear arrangement F-H...H-F, while the maximum positive value is found for the linear H-F...F-H arrangement, despite the fact that neither of these structures is bound. Changes in the sign and magnitude of the FC term are analyzed using the nuclear magnetic resonance triplet wave function model, which relates the orientation of magnetic nuclei to the phases of the wave functions for excited triplet states that couple to the ground state. The FC term for a particular orientation is a result of competing positive and negative contributions from different triplet states, the sign of each contribution being determined by the alignment of the nuclear magnetic moments in that state. Factors are identified which must play a role in determining which types of wave functions dominate.     

Is allylphosphine a carbon or a phosphorus base in the gas phase?

The gas-phase basicity of allylphosphine (2-propenylphosphine) was measured by means of Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry techniques. A complete survey of the allylphosphine-H(+) potential energy surface, carried out through the use of high-level G2(MP2) and B3LYP/6-311+G(3df,2p) calculations, allows us to conclude that, under low-pressure, low-energy ICR conditions, the interaction between the protonated reference base, B(ref)H(+), and allylphosphine leads to a complex in which B(ref)H(+) attaches to the phosphorus atom of allylphosphine, where the electrostatic potential is strongly attractive. Hence, in the first step only the phosphorus protonated species should be formed. Its isomerization to yield the C(beta)-protonated form, which is the global minimum of the potential energy surface, implies a very high activation barrier that cannot be overtaken under normal experimental ICR conditions. Therefore, the main conclusion of our study is that allylphosphine behaves as a phosphorus base in the gas phase, even though the C(beta)-protonated structure is the most stable protonated species. We have also shown that both C(beta)- and C(gamma)-protonation triggers a cyclization of the system. An analysis of the bonding of the different protonated species as compared with that of the neutral system is presented.     

Antibacterial and Photocatalytic Properties of ZnO Nanoparticles Obtained from Chemical versus Saponaria officinalis Extract-Mediated Synthesis

In the present work, the properties of ZnO nanoparticles obtained using an eco-friendly synthesis (biomediated methods in microwave irradiation) were studied. Saponaria officinalis extracts were used as both reducing and capping agents in the green nanochemistry synthesis of ZnO. Inorganic zinc oxide nanopowders were successfully prepared by a modified hydrothermal method and plant extract-mediated method. The influence of microwave irradiation was studied in both cases. The size, composition, crystallinity and morphology of inorganic nanoparticles (NPs) were investigated using dynamic light scattering (DLS), powder X-ray diffraction (XRD), SEM-EDX microscopy. Tunings of the nanochemistry reaction conditions (Zn precursor, structuring agent), ZnO NPs with various shapes were obtained, from quasi-spherical to flower-like. The optical properties and photocatalytic activity (degradation of methylene blue as model compound) were also investigated. ZnO nanopowders’ antibacterial activity was tested against Gram-positive and Gram-negative bacterial strains to evidence the influence of the vegetal extract-mediated synthesis on the biological activity.