Fluorescence properties of recombinant tropomyosin containing tryptophan, 5-hydroxytryptophan and 7-azatryptophan

Tropomyosin mutants containing either tryptophan (122W), 5-hydroxytryptophan (5OH122W) or 7-azatryptophan (7N122W) have been expressed in Escherichia coli and their fluorescence properties studied. The fluorescent amino acids were located at position 122 of the tropomyosin primary sequence, corresponding to a solvent-exposed position c of the coiled-coil heptapeptide repeat. The emission spectrum of the probe in each mutant is blue-shifted slightly with respect to that of the probe in water. The fluorescence anisotropy decays are single exponential, with a time constant of 2-3 ns while the fluorescence lifetimes of the probes incorporated into the proteins, in water, are nonexponential. Because tryptophan in water has an intrinsic nonexponential fluorescence decay, it is not surprising that the fluorescence decay of 122W is well described by a triple exponential. The fluorescence decays in water of the nonnatural amino acids 5-hydroxytryptophan and 7-azatryptophan (when emission is collected from the entire band) are single exponential. Incorporation into tropomyosin induces triple-exponential fluorescence decay in 5-hydroxytryptophan and double-exponential fluorescence decay in 7-azatryptophan. The range of lifetimes observed for 5-hydroxyindole and 5-hydroxytryptophan at high pH and in the nonaqueous solvents were used as a base with which to interpret the lifetimes observed for the 5OH122W and indicate that the chromophore exists in several solvent environments in both its protonated and unprotonated forms in 5OH122W.     

Sorption behaviour of some actinides on silica gel from mineral acids and alcoholic solutions

Sorption of Th, Pa, U, Np and Pu on silica gel from HNO₃, HCl and HCl−ROH solutions was investigated. Equilibrium studies indicated sorption behaviour to vary greatly with the acid used. In mixtures of HCl with different alcohols, distribution coefficints were found to depend on alcohol percentage as well as on acidity. Results were discussed and conditions for possible separations were indicated.     

Global well-posedness and blow-up on the energy space for the inhomogeneous nonlinear Schrödinger equation

We consider the supercritical inhomogeneous nonlinear Schrödinger equation

$$i\partial_t u+\Delta u+|x|^{-b}|u|^{2\sigma}u=0,$$

where \({(2 - b)/N < \sigma < (2 - b)/(N-2)}\) and \({0 < b < \rm min\{2,N\}}\). We prove a Gagliardo–Nirenberg-type estimate and use it to establish sufficient conditions for global existence and blow-up in \({H^1(\mathbb{R}^N)}\).

     

Approximate Homomorphisms II: Group Homomorphisms

Received October 13, 1998     

A novel chaotic Jaya algorithm for unconstrained numerical optimization

Nonlinear Dynamics - Jaya algorithm is one of the recent algorithms developed to solve optimization problems. The basic concept of this algorithm consists in moving the obtained solution, for a...     

Novel valuable fluorine free copper(I) precursors for copper chemical vapor deposition

Novel fluorine free (β-diketonate)Cu^(I)BTMSA precursors (where BTMSA is bis(trimethylsilyl) acetylene) were prepared in good yield (63–80%) by a simple acid–base reaction. The starting β-diketone structure was modified for tailoring physico-chemical properties of synthesized precursors. High volatile, relative thermally stable and low-melting precursors were prepared when asymmetric β-diketones were used. By using the (1-(cyclobutyl)-1,3-butandionate)Cu^(I)BTMSA precursor, highly pure, compact and smooth copper films were deposited on Ta/TaN substrates at deposition temperatures as low as 150 °C.     

Recoverable salen-based macrocyclic chiral complexes; catalysts for enantioselective Henry reactions

Cobalt and chromium complexes have been prepared from chiral calix–salen cyclic ligands. The corresponding tetrahydrosalen reduced forms have been used for copper salt complexation. These new chiral catalysts have been tested for their ability to promote asymmetric Henry reactions between various aldehydes and nitromethane under heterogeneous conditions. The best results were obtained by using tetrahydrosalen-based copper macrocycles, in terms of activity, selectivity, and stability during the recycling process. Ten consecutive runs could indeed be performed with the same catalyst batch to produce the target 1-(2-methoxy-phenyl)-2-nitro-ethanol with highly stable values in terms of yield and enantioselectivity (up to 94% ee).     

Isolation,preparation, and characterization of nanofibers from oil palm empty-fruit-bunch (OPEFB)

Cellulose nanofibers were produced by hydrolyzing oil palm empty-fruit-bunches with sulfuric acid. The effect of hydrolysis time on the structure and properties of the nanofibers was investigated. Fourier transform infrared spectroscopy was employed to evaluate the change of chemical composition. Atomic force microscope images showed that the average thickness of the nanofibers ranged from 1 to 3.5 nm as the hydrolysis time was varied. Longer hydrolysis time produced a higher yield of dispersed nanofibers; whereas the degree of crystallinity and the degree of polymerization decreased with increasing hydrolysis time. The degradation of nanofibers with higher sulfate group content started at a lower temperature.     

Effects of gamma rays on a restored painting from the XVIIth century

The subject of this study is a Peruvian painting from the 17th century, which has been recently restored and then contaminated by mould. It received different unsuccessful treatments. Therefore, radiation process was suggested as an alternative once it is an effective technology for decontamination and conservation purposes. The aim of this study is to investigate the influence of irradiation process on the original painting and on the products used in the restoration process. These products were irradiated with ⁶⁰Co gamma rays applying doses in the range of 6–25 kGy. The polymeric materials were characterized by thermal analysis techniques before and after irradiation. The colour of the pigments irradiated and non-irradiated were compared by spectrophotometric analysis. Small samples removed of the original painting were also irradiated and investigated. The results obtained until now allowed concluding that the irradiation with the appropriated dose of 6.0 kGy, according to the literature, will not damage the restored painting.