Mimicking Tyrosine Phosphorylation in Human Cytochrome c by the Evolved tRNA Synthetase Technique

Phosphorylation of tyrosine 48 of cytochrome c is related to a wide range of human diseases due to the pleiotropic role of the heme‐protein in cell life and death. However, the structural conformation and physicochemical properties of phosphorylated cytochrome c are difficult to study as its yield from cell extracts is very low and its kinase remains unknown. Herein, we report a high‐yielding synthesis of a close mimic of phosphorylated cytochrome c, developed by optimization of the synthesis of the non‐canonical amino acid p‐carboxymethyl‐L ‐phenylalanine (pCMF) and its efficient site‐specific incorporation at position 48. It is noteworthy that the Y48pCMF mutation significantly destabilizes the Fe?Met bond in the ferric form of cytochrome c, thereby lowering the pK_a value for the alkaline transition of the heme‐protein. This finding reveals the differential ability of the phosphomimic protein to drive certain events. This modified cytochrome c might be an important tool to investigate the role of the natural protein following phosphorylation.     

Enzymatic pretreatment of kraft pulps from pinus radiata D don with xylanolytic complex of pénicillium canescens (CP1) fungi

After screening 14 strains exhibiting high xylanase activities,Penicillium canescens (CP1) andPenicillium janthinellum Biourge (CP2) strains were selected. The β-xylanases produced had an optimum temperature and pH of 50°C and 4.0, respectively. Using a bleaching sequence of D₁₀₀EP, D₈₀EP, and XD₈₀EP, the effluent color obtained with XD₈₀EP was lower for CP1 and CP2 than at the D₁₀₀ stage. The color was slightly higher at the XD₈₀EP stage than with the D₈₀EP sequence. In the final pulp obtained with XD₈₀EP pretreatment, the viscosity increase and the Kappa number was similar to that of D₁₀₀EP in the CP1 and CP2 strains. Brightness in the final pulp was slightly lower than that of control. The selectivity ratio was better for the CP1 and CP2 strains as compared to control. In the XD₈₀EP stage using xylanase extract from CP1 with a pulp consistency of 8 to 15%, the Kappa number was not changed, but the viscosity, brightness, and selectivity ratio were improved proportional to the rise in consistency and delignification. Breaking length, burst and tear index, porosity, and elongation, in the final paper did not change after enzymatic treatment. AOX decreased (26%) in the D₈₀ stage effluent as compared with D₁₀₀, whereas in the XD₈₀ stage diminished 42%. The enzymatic treatment with CP1 facilitates the lignin release, decreases the CL0₂ load by 20%, and reduces the AOX without any negative effects on the physical properties of the pulp and paper.     

Electrospray ionization mass spectrometry of tributyltin(IV) complexes and their larvicidal activity on mosquito larvae: crystal and molecular structure of polymeric (Bu3Sn[O2CC6H4{NN(C6H3‐4‐OH(C(H)NC6H4OCH3‐4))}‐o])n

A series of tributyltin(IV) complexes of 2‐[(E)‐2‐(3‐formyl‐4‐hydroxyphenyl)‐1‐diazenyl]benzoic acid and 4‐[((E)‐1‐{2‐hydroxy‐5‐[(E)‐2‐(2‐carboxyphenyl)‐1‐diazenyl]phenyl}methylidene)amino]aryls have been investigated by electrospray mass spectrometry (ESI‐MS) and tandem mass spectrometry (MSⁿ) techniques. The assignments are facilitated by agreement between observed and calculated isotopic patterns and MSⁿ studies. Single‐crystal X‐ray crystallography of (Bu₃Sn[O₂CC₆H₄{N?N(C₆H₃‐4‐OH(C(H)?NC₆H₄OCH₃‐4))}‐o])_n reveals a polymeric structure. Toxicity studies of the tributyltin(IV) complexes of the 4‐[((E)‐1‐{2‐hydroxy‐5‐[(E)‐2‐(2‐carboxyphenyl)‐1‐diazenyl]phenyl}methylidene)amino]aryls on the second larval instar of the Aedes aegypti and Anopheles stephensi mosquito larvae are also reported. The LC₅₀ values indicate that the complexes are effective larvicides, which range from a low of 0.36 ppm to a high of 0.69 ppm against the Ae. aegypti larvae and between 0.82 and 1.17 ppm against the An. stephensi larvae. Copyright © 2005 John Wiley & Sons, Ltd.     

Purification of Uranium‐based Endohedral Metallofullerenes (EMFs) by Selective Supramolecular Encapsulation and Release

Supramolecular nanocapsule 1 ?(BArF)₈ is able to sequentially and selectively entrap recently discovered U₂@C₈₀ and unprecedented Sc₂CU@C₈₀, simply by soaking crystals of 1 ?(BArF)₈ in a toluene solution of arc‐produced soot. These species, selectively and stepwise absorbed by 1 ?(BArF)₈, are easily released, obtaining highly pure fractions of U₂@C₈₀ and Sc₂CU@C₈₀ in one step. Sc₂CU@C₈₀ represents the first example of a mixed metal actinide‐based endohedral metallofullerene (EMF). Remarkably, the host–guest studies revealed that 1 ?(BArF)₈ is able to discriminate EMFs with the same carbon cage but with different encapsulated cluster and computational studies provide support for these observations.     

Combined effects of solar ultraviolet radiation and nutrients addition on growth, biomass and taxonomic composition of coastal marine phytoplankton communities of Patagonia

Experiments (6-8 days) were conducted during late summer, late fall and late winter, 2003 with waters collected off Bahía Nueva, Chubut, Argentina (42.7 degrees S, 65 degrees W) to determine the combined effects of solar ultraviolet radiation (UVR, 280-400 nm) and nutrient addition on phytoplankton communities. Samples were put in UVR-transparent containers and incubated under two radiation treatments: (a) Samples exposed to full solar radiation (PAB treatment, 280-400 nm) and (b) Samples exposed only to PAR (PAR treatment, 400-700 nm). At the beginning of the experiments, nutrients (i.e., NaPO(4)H(2) and NaNO(3)) were added to one set of samples from each radiation treatment (N cultures) whereas in the other set, nutrients remained at the concentration of the seawater. Chlorophyll a, biomass, UV-absorbing compounds and taxonomic composition were recorded throughout the experiments. N cultures always had significantly higher growth rates (P<0.05) than that in non-enriched cultures. At the beginning of experiments, phytoplankton communities were generally dominated by monads and flagellates but by the end, diatoms comprised the bulk of biomass, with only one to four taxa dominating, suggesting a selection towards more tolerant/less sensitive species. Over the experimental time frame, the observed taxonomic changes were mostly due to nutrient availability, and to a lesser extent to solar UVR exposure. Overall, the results indicate that environmental conditions (i.e., light history, nutrient concentration) together with the physiological status of the cells play a very important role at the time to assess the combined effect of nutrient addition and solar radiation on coastal phytoplankton assemblages from Patagonia.     

The Kohn-Sham kinetic energy density as indicator of the electron localization: atomic shell structure

In this report, it is shown that the Kohn-Sham (KS) kinetic energy density (KED) contains the average local electrostatic potential (ALEP) and the average local ionization energy (ALIE); the shell structure in atomic systems is presented as one application of the KS-KED. By writing the KS-KED from the KS equations, this quantity was divided in three contributions: orbital, Coulomb, and exchange correlation. By studying several closed and open shell atoms, the shell structure was established by the maxima presented by the Coulomb contribution and the minima in the orbital contribution of the KS-KED. The exchange-correlation contribution to the KS-KED does not show maxima or minima, but this quantity shows bumps where the division between shells is expected. The results obtained in this work were compared with other shell structure indicators such as the electron localization function, the ALEP, the ALIE, and the radial distribution function. The most important result in this work is related to the fact that even when the ALEP and the ALIE functions were built with different arguments to each other, they are contained in the KS-KED. In this way, the KS-KED shows its importance to reveal the electron localization in atomic systems.     

Comparative spectroscopic and electrochemical study of nitroindazoles: 3-alcoxy, 3-hydroxy and 3-oxo derivatives

Cyclic voltammetry and electron spin resonance techniques were used in the investigation of novel 3-alkoxy- and 3-hydroxy-1-[omega-(dialkylamino)alkyl]-5-nitroindazole derivatives. A self-protonation process involving the protonation of the nitro group was observed. The reactivity of the nitro-anion radical for these derivatives with glutathione, a biological relevant thiol, was also studied by cyclic voltammetry. These studies demonstrated that glutathione could react with radical species from 5-nitroindazole system. Also we demonstrated that nitro-anion radicals show three different patterns of delocalization where the indazole 1-lateral chain does not have major influence.     

Optimisation of the headspace-solid phase microextraction for organomercury and organotin compound determination in sediment and biota

Headspace solid-phase microextraction was optimised for the simultaneous preconcentration of methylmercury (MeHg+), monobutyltin, dibutyltin, tributyltin, monophenyltin (MPhT), diphenyltin (DPhT), and triphenyltin (TPhT) from sediments and biota. Extraction time (3-24 min), extraction temperature (20-90 degrees C), desorption time (1-10.4 min), desorption temperature (152-260 degrees C), and sample volume (5-22 mL) were simultaneously optimised, while variables such as fibre type (30 microm polydimethylsiloxane, PDMS), pH (acetic acid/sodium acetate, HOAc/NaOAc, 2 mol/L, pH approximately 4.8), the concentration of the derivatisation agent (sodium tetraethylborate, NaBEt4, 0.1% m/v), and the ionic strength (fixed by the buffer solution) were kept constant. The variables were optimised according to the experiments proposed by the MultiSimplex program and the responses were considered in order to establish the optimum conditions. The repeatability (relative standard deviation, RSD, 5-20.6%) and limits of detection (LODs, 0.05-0.97 ng/g) of the overall method were also estimated. The lowest precisions were obtained for DPhT and TPhT. The optimised preconcentration method was applied to the determination of MeHg+), butyl- and phenyltins in certified reference materials (IAEA-405 MeHg+) in estuarine sediment, BCR-646 butyl- and phenyltins in marine sediment, BCR-463 MeHg+ in tuna fish, DOLT-2 MeHg+ in dogfish liver, and BCR-477 butyltins in mussel tissue) by GC with microwave-induced plasma/atomic-emission detection.     

A study of the effects of thiols on the frontal polymerization and pot life of multifunctional acrylate systems with cumene hydroperoxide

In an effort to create frontal polymerization systems with a “fail‐safe” curing mechanism, we studied the effects of thiols on the thermal frontal polymerization velocity and pot life of a mixture of a multifunctional acrylate, kaolin clay (filler), and cumene hydroperoxide with either trimethylolpropane tris(3‐mercaptopropionate) or 1‐dodecanethiol (DDT). The acrylates were trimethylolpropane triacrylate, trimethylolpropane ethoxylate triacrylate, 1,6‐hexanediol diacrylate, and di(ethylene glycol) diacrylate. Without a thiol, frontal polymerization did not occur. The front velocity increased with the concentration of either thiol, which has not been observed with peroxide initiators. The use of DDT yielded longer pot lives than the trithiol. The front velocities were inversely related to the pot lives. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 3850–3855