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41.
Francesco Zilio Grandi Lidia Szpyrkowicz 《Fresenius' Journal of Analytical Chemistry》1991,341(10):625-630
Summary Air quality and in particular acid rain composition has gained a great importance in the recent years all over the world. A vast research program has been undertaken also in the Venice Region. A network of 8 sampling stations, remote from motor traffic and industrial sources of air pollutants, was realized in 1988 according to the EMEP statements. It gives meteorological and physical data on the air quality and produces the wet-only samples of meteorological precipitations, of which the chemical composition is determined in laboratory. An automatic analyzer based on colorimetric methods is used for ammonium, sulfate, nitrate, phosphate and chloride determination and an Atomic Absorption spectrometer for Ca, Mg, K and Na analysis. The methods used are based on those recommended by U.S. Standard Methods for water samples. From all of them the method for sulfate determination needed the most serious modifications, due to the interferences of cations. This paper describes the analytical methods used and their detection limits. Data on the rain quality of the region, in the period February–June 1989 for the first 6 stations installed are reported together with their statistical elaborations. The relationships between single ions and the total amount of ions allow to interpret the rain water composition and to check the validity of the analytical methods. The average rain composition approximates a H2SO4/HNO3 mixture with a volume-weighted average of pH of 5.42 and SO
4
2–
/NO
3
–
molar ratio of 1.10. 相似文献
42.
Voliani V Bizzarri R Nifosì R Abbruzzetti S Grandi E Viappiani C Beltram F 《The journal of physical chemistry. B》2008,112(34):10714-10722
Photochromic variants of fluorescent proteins are opening the way to a number of opportunities for high-sensitivity regioselective studies in the cellular environment and may even lead to applications in information and communication technology. Yet, the detailed photophysical processes at the basis of photoswitching have not been fully clarified. In this paper, we used synthetic FP chromophores to clarify the photophysical processes associated with the photochromic behavior. In particular, we investigated the spectral modification of synthetic chromophore analogues of wild-type green fluorescent protein (GFP), Y66F GFP (BFPF), and Y66W GFP (CFP) upon irradiation in solutions of different polarities. We found that the cis-trans photoisomerization mechanism can be induced in all the chromophores. The structural assignments were carried out both by NMR measurements and DFT calculations. Remarkably, we determined for the first time the spectra of neutral trans isomers in different solvents. Finally, we calculated the photoconversion quantum yields by absorption measurements under continuous illumination at different times and by a nanosecond laser-flash photolysis method. Our results indicate that cis-trans photoisomerization is a general mechanism of FP chromophores whose efficiency is modulated by the detailed mutant-specific protein environment. 相似文献
43.
Dr. Eleonora Grandi Dr. Fatma Feyza Özgen Dr. Sandy Schmidt Prof. Gerrit J. Poelarends 《Angewandte Chemie (International ed. in English)》2023,62(48):e202309012
Biocatalytic cascades are a powerful tool for building complex molecules containing oxygen and nitrogen functionalities. Moreover, the combination of multiple enzymes in one pot offers the possibility to minimize downstream processing and waste production. In this review, we illustrate various recent efforts in the development of multi-step syntheses involving C−O and C−N bond-forming enzymes to produce high value-added compounds, such as pharmaceuticals and polymer precursors. Both in vitro and in vivo examples are discussed, revealing the respective advantages and drawbacks. The use of engineered enzymes to boost the cascades outcome is also addressed and current co-substrate and cofactor recycling strategies are presented, highlighting the importance of atom economy. Finally, tools to overcome current challenges for multi-enzymatic oxy- and amino-functionalization reactions are discussed, including flow systems with immobilized biocatalysts and cascades in confined nanomaterials. 相似文献
44.
Dr. Paul Bamborough Dr. Chun‐wa Chung Dr. Emmanuel H. Demont Dr. Rebecca C. Furze Dr. Andrew J. Bannister Dr. Ka Hing Che Dr. Hawa Diallo Clement Douault Dr. Paola Grandi Prof. Tony Kouzarides Dr. Anne‐Marie Michon Darren J. Mitchell Dr. Rab K. Prinjha Dr. Christina Rau Dr. Samuel Robson Robert J. Sheppard Dr. Richard Upton Dr. Robert J. Watson 《Angewandte Chemie (International ed. in English)》2016,55(38):11382-11386
ATAD2 is a cancer‐associated protein whose bromodomain has been described as among the least druggable of that target class. Starting from a potent lead, permeability and selectivity were improved through a dual approach: 1) using CF2 as a sulfone bio‐isostere to exploit the unique properties of fluorine, and 2) using 1,3‐interactions to control the conformation of a piperidine ring. This resulted in the first reported low‐nanomolar, selective and cell permeable chemical probe for ATAD2. 相似文献
45.
Stefania Grandi Piercarlo Mustarelli Simonpietro Agnello Marco Cannas Andrea Cannizzo 《Journal of Sol-Gel Science and Technology》2003,26(1-3):915-918
Optical and structural properties of silica materials with controlled Ge-content were investigated in aerogels samples with Ge concentration up to 100000 molar ppm prepared by a sol-gel method and densified at 1150°C. An optical absorption band centered at 242 nm, commonly ascribed to an under-coordinated germanium point defect, was observed in all doped samples, and its amplitude was found to be almost linearly correlated with the Ge-content. This feature may be ascribed to the new preparation technique so that this is potentially useful to produce materials with controlled defect content for specific optical applications. 相似文献
46.
We report an experimental study of the concentration growth by γ-ray irradiation of germanium lone pair center (GLPC) in 104 part per million molar Ge-doped sol–gel silica. The data show that γ-ray induced GLPC concentration increases linearly up to ~5 MGy and then it seems to reach a limit value. In addition to the dose dependence, we have studied the thermal stability of the radiation induced GLPC in ambient atmosphere up to 415 °C. We found that the concentration of this latter GLPC starts to decrease at ~300 °C, at variance to native GLPC, suggesting that the annealing is related to irradiation products. After the thermal treatments the photoluminescence (PL) activity of the γ induced GLPC shows some spectroscopic differences with respect to that related to the native. These differences have been investigated both as a function of excitation energy and by recording the photoluminescence time decay at low temperature. The obtained results are interpreted on the basis of thermally induced changes in the environment of the defect. 相似文献
47.
Giovanna Navarra Eleonora Vella Stefania Grandi Maurizio Leone Roberto Boscaino 《Journal of Non》2009,355(18-21):1028-1033
In this report we will show the changes of the band shape of the hydroxyl group (SiOH) infrared (IR) absorption band (~3670 cm?1) in silica glass induced by lowering temperature in the range from 290 to 20 K. This band is considered as the overlap of several spectral components associated to the vibrational activity of hydroxyl groups in different bond configurations. By a suitable analysis of the experimental band profile in terms of different sub-bands, we studied the thermal evolution of each component and we reconsidered their assignations. For comparison we examined the SiOD absorption band (~2710 cm?1) as a function of temperature as well. Our data can be interpreted as an evidence of a conversion process of free into H(D)-bonded SiOH(D) groups. Moreover, we estimated the ratio between the molar extinction coefficients of the two main species involved in this process finding that this ratio is appreciably influenced by the isotopic exchange. 相似文献
48.
Claudio M. Poffo Joo C. de Lima Sergio M. Souza Daniela M. Trichês Tarciso A. Grandi Ronaldo S. de Biasi 《Journal of Raman spectroscopy : JRS》2010,41(12):1606-1609
The ball milling process was used to obtain nanocrystalline cubic silicon. Between 5 and 10 h of milling, amorphous silicon was also formed. The differential scanning calorimetry (DSC) spectrum of a powder milled for 10 h showed that the amorphous–crystalline phase transition occurs at about 450 °C. According to Raman spectroscopy and X‐ray diffraction results, volume fractions of the crystalline, interfacial and amorphous phases were about 30, 39 and 31%, respectively. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
49.
We propose a model for nonisothermal ferromagnetic phase transition based on a phase field approach, in which the phase parameter is related but not identified with the magnetization. The magnetization is split in a paramagnetic and in a ferromagnetic contribution, dependent on a scalar phase parameter and identically null above the Curie temperature. The dynamics of the magnetization below the Curie temperature is governed by the order parameter evolution equation and by a Landau–Lifshitz type equation for the magnetization vector. In the simple situation of a uniaxial magnet, it is shown how the order parameter dynamics reproduces the hysteresis effect of the magnetization. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
50.
K.D. Machado A.A.M. Gasperini C.E. Maurmann T.A. Grandi 《Solid State Communications》2005,136(8):466-469
Two alloys of the Co-Ge system were produced by mechanical alloying starting from the elemental powders in the compositions Co20Ge80 and Co40Ge60. The crystalline structures of the CoxGe100−x (x=20, 40) alloys obtained were investigated using the X-ray diffraction (XRD) technique. The measured XRD patterns showed the presence of the peaks corresponding to the crystalline m-CoGe phase and also to the high pressure and temperature phase c-CoGe in the as-milled sample for Co20Ge80, although it was milled at room temperature and pressure. For Co40Ge60, the crystalline Co3Ge2 phase was obtained, and structural data for all phases were determined by means of a Rietveld refinement procedure. The thermal stability of the phases was investigated performing a heat treatment of the alloys at 450 °C for 6 h and, after that, new XRD measurements were collected and were also studied using a Rietveld refinement procedure. The m-CoGe and Co3Ge2 phases seem to be very stable, but the relative amount of c-CoGe decreases a little, indicating a less stable phase, which can be explained by the fact that it is produced usually under extreme conditions. 相似文献