Direct determination of traces of Ag, Cd, Pb, Bi, Cr, Mn, Co, Ni, Li, Be, Cu and Sb in environmental waters and geological materials by simultaneous multi-element graphite furnace atomic absorption spectrometry with Zeeman-effect background correction

A method was developed for direct determination of minor and trace amounts of Cr, Mn, Cu, Ni, Co, Li, Pb, Cd, Bi, Sb, Be and Ag in silicate rock, lake and stream sediments using a microwave oven dissolution method and a multi-element graphite furnace atomic absorption spectrometer equipped with a Zeeman-effect background correction device. The measurement technique was also suitable for direct determination of trace and ultra-trace amounts of these elements in drinking and seawater samples. A rock or sediment sample was brought into solution in a Teflon vessel by heating in a microwave oven with a mixture of hydrofluoric acid and aqua regia, followed by a further heating with a mixture of boric acid and ethylenediaminetetraacetic acid. The specified elements were directly determined in a group of four elements in one firing and eight elements in two firings from this solution or from a diluted solution using the optimum operating parameters developed in this work. The method, tested with 23 international reference rocks and sediments and seven international quality control and reference water samples, showed good to excellent agreement with the recommended values.     

Promising therapeutics with natural bioactive compounds for improving learning and memory - a review of randomized trials

Cognitive disorders can be associated with brain trauma, neurodegenerative disease or as a part of physiological aging. Aging in humans is generally associated with deterioration of cognitive performance and, in particular, learning and memory. Different therapeutic approaches are available to treat cognitive impairment during physiological aging and neurodegenerative or psychiatric disorders. Traditional herbal medicine and numerous plants, either directly as supplements or indirectly in the form of food, improve brain functions including memory and attention. More than a hundred herbal medicinal plants have been traditionally used for learning and memory improvement, but only a few have been tested in randomized clinical trials. Here, we will enumerate those medicinal plants that show positive effects on various cognitive functions in learning and memory clinical trials. Moreover, besides natural products that show promising effects in clinical trials, we briefly discuss medicinal plants that have promising experimental data or initial clinical data and might have potential to reach a clinical trial in the near future.     

Isolation,purification, and characterization of thermophilic laccase from the xerophyte <Emphasis Type=Italic>Cereus pterogonus</Emphasis>

Three laccase temperature isoforms were isolated and purified to homogeneity from the xerophyte plant species Cereus pterogonus. This catalytically active protein exhibited an apparent molecular mass of 137 kDa, 90 kDa, and 43 kDa. Under reducing conditions the enzyme yielded a subunit molecular mass of 43 kDa alone, suggesting that the enzyme is a multimer of its subunits. The enzyme exhibited an optimum pH of 10 with 2,6-dimethoxyphenol used as a substrate. The 137 and 90 kDa forms yielded optimum activity at 90°C; whereas the 43 kDa molecular form yielded optimum activity at 60°C. The enzyme kinetic constant Km remained closely similar for all three enzyme forms, whereas Vmax varied by 25 % overall. The catalytic activity remained above its t_1/2 value in excess of the 30 min denaturation assay period at 60°C and 90°C. These high-temperature isoforms of the plant laccase enzyme with alkaline pH optima can find great industrial use.     

The striking influence of SWNT-COOH on self-assembled gelation

A miniscule amount of f-SWNTs remarkably improved (~17-fold) the gelation efficiency of amphiphilic molecules by triggering the formation of interconnecting self-assembled fibrillar networks (SAFIN) in supramolecular gelation.     

Development of a Mathematical Model for Growth and Oxygen Transfer in In Vitro Plant Hairy Root Cultivations

Genetically transformed, "Hairy roots" once developed can serve as a stable parent culture for in vitro production of plant secondary metabolites. However, the major bottleneck in the commercial exploitation of hairy roots remains its successful scale-up due to oxygen transfer limitation in three-dimensionally growing hairy root mass. Mass transfer resistances near the gas-liquid and liquid-solid boundary layer affect the oxygen delivery to the growing hairy roots. In addition, the diffusional mass transfer limitation due to increasing size of the root ball (matrix) with growth also plays a limiting role in the oxygen transfer rate. In the present study, a mathematical model is developed which describes the oxygen transfer kinetics in the growing Azadirachta indica hairy root matrix as a case study for offline simulation of process control strategies ensuring non-limiting concentrations of oxygen in the medium throughout the hairy root cultivation period. The unstructured model simulates the effect of oxygen transfer limitation in terms of efficiency factor (η) on specific growth rate (μ) of the hairy root biomass. The model is able to predict effectively the onset of oxygen transfer limitation in the inner core of the growing hairy root matrix such that the bulk oxygen concentration can be increased so as to prevent the subsequent inhibition in growth of the hairy root biomass due to oxygen transfer (diffusional) limitation.     

Lower rim 1,3-di{4-antipyrine}amide conjugate of calix[4]arene: synthesis, characterization, and selective recognition of Hg2+ and its sensitivity toward pyrimidine bases

The structurally characterized lower rim 1,3-di{4-antipyrine}amide conjugate of calix[4]arene (L) exhibits high selectivity toward Hg(2+) among other biologically important metal ions, viz., Na(+), K(+), Ca(2+), Mg(2+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), Pb(2+), and Ag(+) as studied by fluorescence, absorption, and ESI MS. L acts as a sensor for Hg(2+) by switch-off fluorescence and exhibits a lowest detectable concentration of 1.87 ± 0.1 ppm. The complex formed between L and Hg(2+) is found to be 1:1 on the basis of absorption and fluorescence titrations and was confirmed by ESI MS. The coordination features of the mercury complex of L were derived on the basis of DFT computations and found that the Hg(2+) is bound through an N(2)O(2) extending from both the arms to result in a distorted octahedral geometry with two vacant sites. The nanostructural features such as shape and size obtained using AFM and TEM distinguishes L from its Hg(2+) complex and were different from those of the simple mercuric perchlorate. L is also suited to sense pyrimidine bases by fluorescence quenching with a minimum detection limit of 1.15 ± 0.1 ppm in the case of cytosine. The nature of interaction of pyrimidine bases with L has been further studied by DFT computational calculations and found to have interactions through a hydrogen bonding and NH-π interaction between the host and the guest.     

Influence of 2'-deoxy sugar moiety on excited-state protonation equilibrium of adenine and adenosine with acridine inside SDS micelles: a time-resolved study with quantum chemical calculations

The protonation dynamics of the DNA base adenine (Ade) and its nucleoside 2'-deoxyadenosine (d-Ade) are investigated by monitoring the deprotonation kinetics of an N-heterocyclic DNA intercalator, acridine (Acr), in the confined environment of sodium dodecyl sulfate (SDS) micelles. Protonation of acridine (AcrH(+)) occurs at the hydrophilic interface and this species remains in dynamic equilibrium with its deprotonated counterpart (Acr) inside the hydrophobic core of SDS micelles. Quenching of the fluorescence of AcrH(+)* at 478 nm is observed after addition of Ade and d-Ade with Stern-Volmer constant (K(SV)) 298 and 75 M(-1), respectively, with a concomitant increment in Acr* at 425 nm. Time-resolved fluorescence studies reveal quenching in the lifetime of AcrH(+)*. The relative amplitude of AcrH(+)* decreases from 0.97 to 0.51 and 0.97 to 0.89 with equimolar addition of Ade and d-Ade, respectively. These observations are explained by excited-state proton transfer (ESPT) from AcrH(+)* to the bases. The reduced K(SV) value and negligible change in the relative amplitudes of AcrH(+)* with d-Ade infer that ESPT is hindered substantially by the presence of a 2'-deoxy sugar unit. Transient time-resolved absorption spectra of Acr reflect that Ade reduces the absorbance of (3)AcrH(+)*; however, d-Ade keeps it unaltered for more than a time delay of 2 μs. The optimized geometries calculated by quantum chemical methods reflect deprotonation of AcrH(+)* with protonation at the N1 position of Ade, while it remains protonated with d-Ade. The hindered ESPT between AcrH(+)* and d-Ade singles out the significance of the 2'-deoxy sugar moiety in controlling the deprotonation kinetics.     

Restricted conformational flexibility of a triphenylamine derivative on the formation of host-guest complexes with various macrocyclic hosts

Herein, we report the host-guest-type complex formation between the host molecules cucurbit[7]uril (CB[7]), β-cyclodextrin (β-CD), and dibenzo[24]crown-8 ether (DB24C8) and a newly synthesized triphenylamine (TPA) derivative 1X(3) as the guest component. The host-guest complex formation was studied in detail by using (1)H?NMR, 2D NOESY, UV/Vis fluorescence, and time-resolved emission spectroscopy. The chloride salt of the TPA derivative was used for recognition studies with CB[7] and β-CD in an aqueous medium. The restricted internal rotation of the guest molecule on complex formation with either of these two host molecules was reflected in the enhancement of the emission quantum yield and the average excited-state lifetime for the triphenylamine-based excited states. Studies with DB24C8 as the host molecule were performed in dichloromethane, a medium that maximizes the noncovalent interaction between the host and guest fragments. The F?rster resonance energy transfer (FRET) process involving DB24C8 and 1(PF(6))(3), as the donor and acceptor fragments, respectively, was established by electrochemical, steady-state emission, and time-correlated single-photon counting studies.     

Characterization of rhinovirus subviral A particles via capillary electrophoresis, electron microscopy and gas-phase electrophoretic mobility molecular analysis: Part I

During infection, enteroviruses, such as human rhinoviruses (HRVs), convert from the native, infective form with a sedimentation coefficient of 150S to empty subviral particles sedimenting at 80S (B particles). B particles lack viral capsid protein 4 (VP4) and the single-stranded RNA genome. On the way to this end stage, a metastable intermediate particle is observed in the cell early after infection. This subviral A particle still contains the RNA but lacks VP4 and sediments at 135S. Native (150S) HRV serotype 2 (HRV2) as well as its empty (80S) capsid have been well characterized by capillary electrophoresis. In the present paper, we demonstrate separation of at least two forms of subviral A particles on the midway between native virions and empty 80S capsids by CE. For one of these intermediates, we established a reproducible way for its preparation and characterized this particle in terms of its electrophoretic mobility and its appearance in transmission electron microscopy (TEM). Furthermore, the conversion of this intermediate to 80S particles was investigated. Gas-phase electrophoretic mobility molecular analysis (GEMMA) yielded additional insights into sample composition. More data on particle characterization including its protein composition and RNA content (for unambiguous identification of the detected intermediate as subviral A particle) will be presented in the second part of the publication.     

A series of trifacial Pd6 molecular barrels with porphyrin walls

Three new nanoscopic trigonal prisms, [(tmen)(6) Pd(6) (H(2)L)(3)](NO(3))(12) (1), [(Meen)(6) Pd(6)(H(2) L)(3)](NO(3))(12) (2), and [(2,2'-bipy)(6)Pd(6) (H(2)L)(3)](NO(3))(12) (3), have been synthesized in excellent yields through single-step metal-ligand-coordination-driven self-assembly using 5,10,15,20-tetrakis(3-pyridyl)porphyrin (H(2)L) as a donor and cis-blocked Pd(II) 90° acceptors. These complexes were fully characterized by spectroscopic studies and single-crystal X-ray diffraction. All of these barrels quantitatively bind Zn(II) ions in the N(4) pockets of the porphyrin walls at room temperature. Their corresponding zinc-embedded complexes, [(tmen)(6)Pd(6)(ZnL)(3)](NO(3))(12) (1?a), [(Meen)(6) Pd(6)(ZnL)(3)](NO(3))(12) (2?a), and [(2,2'-bipy)(6)Pd(6)(ZnL)(3)](NO(3))(12) (3?a), were synthesized under ambient conditions by the post-synthetic binding of Zn(II) ions into the H(2)N(4) pockets of the porphyrin walls of these complexes. These zinc-embedded complexes were characterized by electronic absorption, fluorescence emission, (1)H?NMR spectroscopy, as well as elemental analysis. Complexes 1-3 exhibited considerable microporosity in their solid state. Complex 1 was an efficient adsorbent for nitrogen gas and EtOH, MeOH, and water vapors.