Projector quantization method of systems with linearly dependent constraints

The local free coordinates on the constraint surface are obtained within symplectic projector method when the constraints are linearly dependent. One example is investigated in details. Presented at the International Colloquium “Integrable Systems and Quantum Symmetries”, Prague, 16–18 June 2005.     

Fabrication of Thymoquinone‐Loaded Albumin Nanoparticles by Microfluidic Particle Synthesis and Their Effect on Planarian Regeneration

Thymoquinone is the main bioactive component of the plant Nigella sativa, which is commonly known as black seeds and has several therapeutic effects. However, clinical applications of thymoquinone are limited due to its hydrophobic nature. In this study, thymoquinone is encapsulated in albumin nanoparticles by using a microfluidic platform to overcome this limitation. The mean particle sizes of empty and thymoquinone‐loaded nanoparticles are determined as 271.3 and 315.6 nm, respectively, with polydispersity index values both lower than 0.25. In addition to particle size distribution measurements, characterizations of the prepared nanoparticles such as zeta potential measurements, in vitro release studies, as well as scanning electron microscopy, Fourier‐transform infrared, and differential scanning calorimetry analyses are also carried out. To determine the effect of thymoquinone on neural regeneration, planarians are used as the model organism. After application of free and encapsulated thymoquinone, planarians are amputated and the fragments are observed in terms of head and tail regeneration, swimming pattern, and behavior. The results indicate that thymoquinone affects their behavior and primarily enhances head regeneration of planarians. In addition, it is shown that encapsulation of thymoquinone not only enhances the thermal stability of the molecule but also decreases its toxicity.     

Synthesis,structure and in vitro anticancer activity of ruthenium(II) and platinum(II) complexes with chiral aminophosphine ligands

Transition Metal Chemistry - (R)-[Ru(η6-p-MeC6H4iPr)Cl2{Ph2PNHCH(CH3)(C6H4-4-F)}] (1) and cis-(R,R)-[PtCl2{Ph2PNHCH(CH3)(C6H4-4-F)}2] (2) have been obtained by the reaction of the chiral...     

Spectral characterization of a newly synthesized fluorescent semicarbazone derivative and its usage as a selective fiber optic sensor for copper(II)

In this work photoluminescent properties of highly Cu(2+) selective organic fluoroionophore, semicarbazone derivative; bis(naphtho[2,1-b]furan-2-yl)methanone semicarbazone (BNF) was investigated in different solvents (dichloromethane, tetrahydrofuran, toluene and ethanol) and in polymer matrices of polyvinylchloride (PVC) and ethyl cellulose (EC) by absorption and emission spectrometry. The BNF derivative displayed enhanced fluorescence emission quantum yield, Q(f)=6.1 x 10(-2) and molar extinction coefficient, epsilon=29,000+/-65 cm(-1)M(-1) in immobilized PVC matrix, compared to 2.6 x 10(-3) and 24,573+/-115 in ethanol solution. The offered sensor exhibited remarkable fluorescence intensity quenching upon exposure to Cu(2+) ions at pH 4.0 in the concentration range of 1.0 x 10(-9) to 3.0 x 10(-4)M [Cu(2+)] while the effects of the responding ions (Ca(2+), Hg(+), Pb(2+), Al(3+), Cr(3+), Mn(2+), Mg(2+), Sn(2+), Cd(2+), Co(2+) and Ni(2+)) were less pronounced.     

Pore hierarchy in mesoporous silicas evidenced by in-situ SANS during nitrogen physisorption

The pore hierarchy of a hierarchical porous SiO2 with 14 nm spherical mesopores and 3 nm worm-like pores (KLE1C16) is studied by small-angle neutron scattering (SANS) in combination with in-situ nitrogen sorption at 77 K. A novel setup is used developed at Hahn-Meitner Institute, Berlin. It is demonstrated that in these materials indeed all of the large mesopores are connected through the smaller ones, thus providing invaluable insights into the general phenomenon of pore connectivity in mesoporous materials.     

Subtle pH differences trigger single residue motions for moderating conformations of calmodulin

This study reveals the essence of ligand recognition mechanisms by which calmodulin (CaM) controls a variety of Ca(2+) signaling processes. We study eight forms of calcium-loaded CaM each with distinct conformational states. Reducing the structure to two degrees of freedom conveniently describes main features of the conformational changes of CaM via simultaneous twist-bend motions of the two lobes. We utilize perturbation-response scanning (PRS) technique, coupled with molecular dynamics simulations. PRS is based on linear response theory, comprising sequential application of directed forces on selected residues followed by recording the resulting protein coordinates. We analyze directional preferences of the perturbations and resulting conformational changes. Manipulation of a single residue reproduces the structural change more effectively than that of single/pairs/triplets of collective modes of motion. Our findings also give information on how the flexible linker acts as a transducer of binding information to distant parts of the protein. Furthermore, by perturbing residue E31 located in one of the EF hand motifs in a specific direction, it is possible to induce conformational change relevant to five target structures. Independently, using four different pK(a) calculation strategies, we find this particular residue to be the charged residue (out of a total of 52), whose ionization state is most sensitive to subtle pH variations in the physiological range. It is plausible that at relatively low pH, CaM structure is less flexible. By gaining charged states at specific sites at a pH value around 7, such as E31 found in the present study, local conformational changes in the protein will lead to shifts in the energy landscape, paving the way to other conformational states. These findings are in accordance with Fluorescence Resonance Energy Transfer (FRET) measured shifts in conformational distributions towards more compact forms with decreased pH. They also corroborate mutational studies and proteolysis results which point to the significant role of E31 in CaM dynamics.     

The Optimization of Dilute Acid Hydrolysis of Cotton Stalk in Xylose Production

Cotton stalk, a lignocellulosic waste material, is composed of xylose that can be used as a raw material for production of xylitol, a high-value product. There is a growing interest in the use of lignocellulosic wastes for conversion into various chemicals because of their low cost and the fact that they are renewable and abundant. The objective of the study was to determine the effects of H₂SO₄ concentration, temperature, and reaction time on the production of sugars (xylose, glucose, and arabinose) and on the reaction by-products (furfural and acetic acid). Response surface methodology was used to optimize the hydrolysis process in order to obtain high xylose yield and selectivity. The optimum reaction temperature, reaction time, and acid concentration were 140 °C, 15 min, and 6%, respectively. Under these conditions, xylose yield and selectivity were found to be 47.88% and 2.26 g g⁻¹, respectively.     

Simultaneous determination of potassium guaiacolsulfonate, guaifenesin, diphenhydramine HCl and carbetapentane citrate in syrups by using HPLC-DAD coupled with partial least squares multivariate calibration

A simple and rapid analytical procedure was proposed for the determination of chromatographic peaks by means of partial least squares multivariate calibration (PLS) of high-performance liquid chromatography with diode array detection (HPLC-DAD). The method is exemplified with analysis of quaternary mixtures of potassium guaiacolsulfonate (PG), guaifenesin (GU), diphenhydramine HCI (DP) and carbetapentane citrate (CP) in syrup preparations. In this method, the area does not need to be directly measured and predictions are more accurate. Though the chromatographic and spectral peaks of the analytes were heavily overlapped and interferents coeluted with the compounds studied, good recoveries of analytes could be obtained with HPLC-DAD coupled with PLS calibration. This method was tested by analyzing the synthetic mixture of PG, GU, DP and CP. As a comparison method, a classsical HPLC method was used. The proposed methods were applied to syrups samples containing four drugs and the obtained results were statistically compared with each other. Finally, the main advantage of HPLC-PLS method over the classical HPLC method tried to emphasized as the using of simple mobile phase, shorter analysis time and no use of internal standard and gradient elution.