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101.
Luciana Malavolta 《Tetrahedron》2004,60(42):9417-9424
Dissociation of peptide when in solution or attached to a polymer was investigated. Magnified solvation of peptide-resins occurred in solvent with similar polarity. Conversely the solubilization of peptides was not usually directly related to the medium polarity. The greater the difference between acidity and basicity of solvent and its potential to form van der Waals interaction, the stronger its solubilization strength. Solvents with similar electrophilicity and nucleophilicity usually did not solvate aggregated peptide-resins nor dissolve peptides. The peptide solubilization in water-containing mixed solvents depended on combination of acidity/basicity of both components. Some criteria for choosing suitable solvents for peptide-resin solvation or peptide solubilization could be advanced. 相似文献
102.
Gianni Podda Antonio Maccioni Luciana Corda Enrico Vecchi Sergio Daolio Pietro Traldi 《Journal of heterocyclic chemistry》1985,22(1):17-20
The electron impact mass spectrometric behaviour of some new diastereoisomeric macrocycles containing diglycolyl moiety as subcyclic unit is reported and discussed in detail with the aid of linked scans, exact mass measurements and collisionally activated decomposition mass analyzed ion kinetic energy spectra. 相似文献
103.
Luciana A. I. de Azeredo Leda R. Castilho Selma G. F. Leite Rosalie R. R. Coelho Denise M. G. Freire 《Applied biochemistry and biotechnology》2003,108(1-3):749-755
Streptomyces are important microorganisms because of their capacity to produce numerous bioactive molecules. In the present work protease
production, by Streptomyces sp. 594 isolated from a Brazilian Cerrado soil, was maximized by optimizing a low-cost culture medium composition (casitone
and sugarcane molasses) using statistical experimental design. The final protease activity (56 U/mL) was 2.8-fold and 58-fold
higher than that obtained in the beginning of this study, and in a previous work, using an actinomycete selection medium,
respectively. Protease production, not growth associated, appeared to be modulated by an inducer system, whereby the C/N ratio
seemed to play a significant role. 相似文献
104.
Nilo Zanatta Fabio M. da Silva Luciana S. da Rosa Louíse Jank Helio G. Bonacorso Marcos A.P. Martins 《Tetrahedron letters》2007,48(37):6531-6534
A simple one-pot procedure to obtain a series of new 3-alkoxy-3-cyanocarboxylic acids from the reaction of 4-alkoxy-1,1,1-trichloro-but-3-en-2-ones with sodium cyanide is described. 相似文献
105.
Vandenberghe LP Soccol CR Prado FC Pandey A 《Applied biochemistry and biotechnology》2004,118(1-3):293-303
Studies were conducted to evaluate citric acid production by solid-state fermentation (SSF) using cassava bagasse as substrate
employing a fungal culture of Aspergillus niger LPB 21 at laboratory and semipilot scale. Optimization of the process parameters temperature, pH, initial humidity, aeration,
and nutritive composition was conducted in flasks and column fermentors. The results showed that thermal treatment of cassava
bagasse enhanced fungal fermentation efficacy, resulting in 220 g of citric acid/kg of dry cassava bagasse with only treated
cassava bagasse as substrate. The results obtained from the factorial experimental design in a column bioreactor showed that
an aeration rate of 60 mL/min (3 mL/[g·min]) and 60% initial humidity were optimum, resulting in 265.7 g/kg of dry cassava
bagasse citric acid production. This was almost 1.6 times higher than the quantities produced under unoptimized conditions
(167.4 g of citric acid/kg of dry cassava bagasse). The defined parameters were transferred to semipilot scale, which showed
high promise for large-scale citric acid production by SSF with cassava bagasse. Respirometry assays were carried out in order
to follow indirectly the biomass evolution of the process. Citric acid production reached 220, 309, 263, and 269 g/kg of dry
cassava bagasse in Erlenmeyer flasks, column fermentors, a tray bioreactor, and a horizontal drum bioreactor, respectively. 相似文献
106.
Lopes Jesus AJ Tomé LI Eusébio ME Redinha JS 《The journal of physical chemistry. B》2005,109(38):18055-18060
The enthalpies of sublimation of erythritol and L-threitol have been determined at 298.15 K by calorimetry. The values obtained for the two diastereomers differ from one another by 17 kJ mol(-1). An interpretation of these results is based on the decomposition of this thermodynamic property in a term coming from the intermolecular interactions of the molecules in the crystal (delta(int)H degrees) and another one related with the conformational change of the molecules on going from the crystal lattice to the most stable forms in the gas phase (delta(conf)H degrees). This last term was calculated from the values of the enthalpy of the molecules in the gas state and of the enthalpy of the isolated molecules with the crystal conformation. Both quantities were obtained by density functional theory (DFT) calculations at the B3LYP/6-311G++(d,p) level of theory. The results obtained in this study show that the most important contribution to the differences observed in the enthalpy of sublimation are the differences in the enthalpy of conformational change (13 kJ mol(-1)) rather than different intermolecular forces exhibited in the solid phase. This is explained by the lower enthalpy of threitol in the gas phase relative to erythritol, which is attributed to the higher strength of the intramolecular hydrogen bonds in the former. The comparison of the calculated infrared spectra obtained for the two compounds in the gas phase supports this interpretation. 相似文献
107.
Luciana Corda Giovanna Delogu Elias Maccioni Gianni Podda Jos Manuel Blanco Fernandez 《Journal of heterocyclic chemistry》1994,31(6):1337-1342
The mass spectrometric behavior of new tris(polyoxalkyl)amines (tridents) 1–5 have been studied and compared with N-(3,6,9,12-tetraoxatridecyl)-16-aza-18-crown-6 ( 6 ) and 1-morpholino-3,6,9-trioxadecane ( 7 ). The peculiar fragmentation patterns are emphasized. 相似文献
108.
109.
Paulo C. Nascimento Luciana Didonet Del-Fabro Cristiane Luisa Jost Denise Bohrer Leandro Machado de Carvalho Marcelo Barcellos Rosa 《Journal of Analytical Chemistry》2009,64(7):677-682
A spectrophotometric method for simultaneous determination of Al(III) and Fe(III) using the chelator Desferal® (desferrioxamine B) was developed. Partial least squares (PLS) regression was performed to resolve the overlapped signals obtained from Al(III) and Fe(III) complexes. The parameters controlling behavior of the system were investigated and optimum conditions were selected. PLS was the choice for the analysis of binary mixtures of Fe(III) and Al(III) over the range of 0.1 to 0.8 mg L?1 by using the data of first derivative spectra. Absorbance data were taken between 200 and 600 nm. The calculated sensitivity values for the multivariate method were 4.88 and 5.64 for Al(III) and Fe(III), respectively. Multivariate detection limits were 0.075 and 0.064 mg L?1 for Al(III) and Fe(III), respectively. The method was applied to real post-hemodialysis samples, and sample digestion by UV irradiation was discussed. 相似文献
110.
Species arising from Fe(II) hydrolysis in aqueous solution have been investigated using density-functional methods (DFT). The different tautomers and multiplicities of each species have been calculated. The solvation energy has been estimated using the UAHF–PCM method. The hydrolysis free energies have been estimated and compared with the available experimental data. The different hydrolysis species have distinct geometries and electronic structures. The estimated ionization potential of the hydrolyzed species is linearly dependent to the number of hydroxyls present in the complex. The estimated Fe(II)/Fe(III) oxidation potential is in good agreement with previously published results about 0.29 V larger than the experimental value. The results highlight the importance of the chemical speciation in describing electron transfer processes at a molecular level. The PBE/TZVP/UAHF–PCM method has been found to describe correctly the hydrolysis free energies of Fe(II) with an average error about 5 kcal mol−1 from the experimental values. 相似文献