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11.
The hexasubstituted benzenes 7 and 9b were synthesized starting from 3 and 8b, respectively. In the crystal, 9b adopts the fully alternated conformation with all arylmethyl groups oriented syn. 相似文献
12.
Silva Silvio S. Ribeiro JoÃo D. Felipe Maria G. A. Vitolo Michelle 《Applied biochemistry and biotechnology》1997,(1):557-564
Batch fermentations of sugar cane bagasse hemicellulosic hydrolysate treated for removing the inhibitors of the fermentation
were performed byCandida guilliermondii FTI20037 for xylitol production. The fermentative parameters agitation and aeration rate were studied aiming the maximization
of xylitol production from this agroindustrial residue. The maximal xylitol volumetric productivity (0.87 g/L h) and yield
(0.67 g/g) were attained at 400/min and 0.45 v.v.m. (KLa 27/h). According to the results, a suitable control of the oxygen input permitting the xylitol formation from sugar cane
bagasse hydrolysate is required for the development of an efficient fermentation process for large-scale applications. 相似文献
13.
Silvio Aime Mauro Botta Giancarlo Cravotto Luca Frullano GiovanniB. Giovenzana Simonetta GeninattiCrich Giovanni Palmisano Massimo Sisti 《Helvetica chimica acta》2005,88(3):588-603
Four new ligands for lanthanide ions based on the H3do3a (=1,4,7,10‐tetraazacyclododecane‐1,4,7‐triacetic acid) structure and bearing one N‐sulfonylacetamide arm were synthesized, i.e., H4dota‐NHSO2R=10‐{2‐[(R)sulfonylamino]‐2‐oxoethyl}‐1,4,7,10‐tetraazacyclododecane‐1,4,7‐triacetic acids 1a – e . A 15N‐NMR study of the 15N‐labelled Eu3+ complex of one such ligands, 1d , showed that the coordination of the N‐sulfonylacetamide arm involves the carbonyl O‐atom rather than the N‐atom. The relaxometric properties of the corresponding Gd3+ complexes were investigated as a function of pH and temperature. These complexes have relaxivities in the range 4.5–5.3 mM ?1 s?1, at 20 MHz and 25°, and are characterized by a single H2O molecule in their inner coordination sphere. The mean residence lifetime of this molecule is relatively long (500–700 ns) compared to other anionic complexes. The slow rate of H2O exchange can be justified by the extensive delocalization of the negative charge on the N‐sulfonylacetamide arm. The long residence time of the coordinated H2O allowed the observation of the effect of the prototropic exchange on the relaxivity. The study of the interaction between the complex [Gd( 1e )]‐ and HSA revealed a weak affinity constant highlighting the importance of a localized negative charge on the complex to promote a strong interaction with the protein. 相似文献
14.
2-Amino-5-alkyl and 2-amino-5-aryl-1,3,4-thiadiazoles were prepared by the dehydration of 2-acylthiosemicarbazides with molar equivalents of methanesulfonic acid in refluxing toluene. The synthesis appears to be general. 相似文献
15.
Alessandro?De?Robertis Concetta?De?Stefano Demetrio?Milea Silvio?SammartanoEmail author 《Journal of solution chemistry》2005,34(10):1211-1226
Complex formation constants were determined potentiometrically (by a ISE-H+, glass electrode) in the systems, M2+ – Lz – H+ [M2+ = (C2H5)2Sn2+, Lz = malonate, glycinate and ethylenediamine] at t = 25 ∘C and 0.1 mol-L−1≤ I/ ≤ 1 mol-L−1 in NaClaq (0.1 mol-L−1 ≤ I ≤ 0.75 mol-L−1 for the ethylenediamine system). Thermodynamic values of formation constants, at infinite dilution, are [± 95% confidence
interval, Tβpqr refer to the equilibrium, pM2+ + qLz + rH+ = MpLqHr(2+z+r)]: for malonate, log10 Tβ110 = (5.47 ± 0.10); for glycinate, log10 Tβ110 = (9.54 ± 0.08), log10 Tβ111 = (12.97 ± 0.10); and for ethylenediamine, log10 Tβ110 = (10.47 ± 0.10), log10 Tβ120 = (16.17 ± 0.12) and log10 Tβ111 = (15.46 ± 0.10). The dependence on ionic strength of the formation constants was modeled by a simple Debye–Hückel type equation
and by the SIT approach. By analyzing the stability of the species in the three different systems we found a simple additivity
rule that can be expressed by the relationship: log10 K = 6.46 nN + 3.96 nO − 0.60 (nN2+ nO2), with a mean deviation, ε(log10 K) = 0.15 (K = equilibrium constant for the interaction of the organometal cation with the unprotonated or protonated ligand, nN = number of amino groups and nO = number of carboxylic groups of the ligand(s) involved in the formation reaction of complex species). 相似文献
16.
Fontana Jose D. Franco Valeria C. De Souza Silvio J. Lyra Ivone N. De Souza Angelita M. 《Applied biochemistry and biotechnology》1991,28(1):341-351
Caffeine and related xanthines were identified as potent stimulators for the bacterial cellulose production in A. xylinum. These compounds are present in several plants whose infusions are useful as culture-medium supplements for this acetobacterium.
The proposed target for these native purine-like inhibitory substances is the novel diguanyl nucleotide phosphodiesterase(s) that participate(s) in the bacterial cellulogenic complex.
A better understanding of this feature of A. xylinum physiology may facilitate the preparation of bacterial cellulose pellicles, which are applied as a biotechnological tool in the treatment of skin burns and other dermal injuries.
相似文献17.
Stefano Banfi Fernando Montanari Silvio Quici Gaguik Torossian 《Journal of inclusion phenomena and macrocyclic chemistry》1992,12(1-4):159-173
Reaction rates of alkene epoxidations, promoted by aqueous NaOCl and catalyzed by Mn(III)-tetrakis(2,6-dichlorophenyl)porphyrin chloride1 (P) in the presence of a lipophilic axial ligand (L) (e.g.N-hexylimidazole) and carried out under H2O/CH2Cl2 two phase conditions at 0°C, are strongly enhanced by lowering the pH of the aqueous phase from 12.7 to 9.5. Under these conditions, a further relevant increase in the reaction rates can be achieved by adding phase-transfer catalysts (PT), e.g. quaternary ammonium salt 3, lipophilic crown ether4 or cryptand5, provided that the amount of L is very small (L/P=1 for very reactive alkenes, e.g. cyclooctene, and 10 for poorly reactive ones, e.g. 1-dodecene). In the case of cyclooctene epoxidation, the use of 0.006–0.03 mol. equiv. of PT completes the reaction in 1–10 min., the initial rates being up to 600 turnovers/min. with (2.2.2,C10) cryptand. In the absence of the axial ligand, the quaternary ammonium salt3 and cryptand5 show an inhibitory effect. Such an effect is due to the formation of the poorly reactive Mn(P)CI species, by Cl– extraction to the organic phase. However, dibenzo crown ether 4 does not show this effect. In the presence of 4, and with L/P =1, the 1-dodecene epoxidation reaches 94% in 1 min. The unique behavior of crown ethers can be explained by their ineffectiveness in extracting alkali chlorides, providing a very low concentration of Cl– in the organic phase and thus avoiding the Mn(III)-porphyrin deactivation.This paper is dedicated to the memory of the late Dr C. J. Pedersen. 相似文献
18.
Thierry Wesley de Albuquerque Aguiar Jos Josenildo Batista Silvio Assis de Oliveira Ferreira Maíra de Vasconcelos Lima Sampaio Dewson Rocha Pereira Magda Rhayanny Assuno Ferreira Luiz Alberto Lira Soares Ana Maria Mendona de Albuquerque Melo Mnica Camelo Pessoa de Azevedo Albuquerque Andr de Lima Aires Hallysson Douglas Andrade de Araújo Luana Cassandra Breitenbach Barroso Coelho 《Molecules (Basel, Switzerland)》2022,27(15)
Biomphalaria glabrata snails constitute the main vector of schistosomiasis in Brazil, and Bauhinia monandra Kurz, the leaves of which contain BmoLL lectin with biocidal action, is a plant widely found on continents in which the disease is endemic. This work describes the composition of B. monandra preparations and the effect on embryos and adult snails, their reproduction parameters and hemocytes. We also describe the results of a comet assay after B. glabrata exposure to sublethal concentrations of the preparations. Additionally, the effects of the preparations on S. mansoni cercariae and environmental monitoring with Artemia salina are described. In the chemical evaluation, cinnamic, flavonoid and saponin derivatives were detected in the two preparations assessed, namely the saline extract and the fraction. Both preparations were toxic to embryos in the blastula, gastrula, trochophore, veliger and hippo stages (LC50 of 0.042 and 0.0478; 0.0417 and 0.0419; 0.0897 and 0.1582; 0.3734 and 0.0974; 0.397 and 0.0970 mg/mL, respectively) and to adult snails (LC50 of 6.6 and 0.87 mg/mL, respectively), which were reproductively affected with decreased egg deposition. In blood cell analysis, characteristic cells for apoptosis, micronucleus and binucleation were detected, while for comet analysis, different degrees of nuclear damage were detected. The fraction was able to cause total mortality of the cercariae and did not present environmental toxicity. Therefore, B. monandra preparations are promising in combating schistosomiasis since they can control both the intermediate host and eliminate the infectious agent, besides being safe to the environment. 相似文献
19.
Antonella Battisti Silvio Panettieri Gerardo Abbandonato Emanuela Jacchetti Francesco Cardarelli Giovanni Signore Fabio Beltram Ranieri Bizzarri 《Analytical and bioanalytical chemistry》2013,405(19):6223-6233
The arsenal of fluorescent probes tailored to functional imaging of cells is rapidly growing and benefits from recent developments in imaging strategies. Here, we present a new molecular rotor, which displays strong absorption in the green region of the spectrum, very little solvatochromism, and strong emission sensitivity to local viscosity. The emission increase is paralleled by an increase in emission lifetime. Owing to its concentration-independent nature, fluorescence lifetime is particularly suitable to image environmental properties, such as viscosity, at the intracellular level. Accordingly, we demonstrate that intracellular viscosity measurements can be efficiently carried out by lifetime imaging with our probe and phasor analysis, an efficient method for measuring lifetime-related properties (e.g., bionalyte concentration or local physicochemical features) in living cells. Notably, we show that it is possible to monitor the partition of our probe into different intracellular regions/organelles and to follow mitochondrial de-energization upon oxidative stress. 相似文献
20.
Clemente Bretti Concetta De Stefano Claudia Foti Silvio Sammartano 《Journal of solution chemistry》2013,42(7):1452-1471
The protonation constants and solubilities of three complexons [ethylenediamine-N,N′-disuccinic acid (EDDS), ethylene glycol bis(2-aminoethyl ether)-N,N,N′,N′-tetraacetic acid (EGTA) and 1,2-cyclohexanediamine-N,N,N′,N′-tetraacetic acid (CDTA)] are reported in aqueous solutions of NaCl with different ionic strength values (0 ≤ I ≤ 4.8 mol·L?1) and, in the case of CDTA, in (CH3)4NCl (0.1 ≤ I ≤ 2.7 mol·L?1). The dependence on ionic strength of the protonation constants of these three complexons and four other complexons that were previously reported (NTA, EDTA, DTPA and TTHA), is analyzed in NaCl solution; the ionic strength influences quite strongly the protonation constants (as an example for CDTA, log10 K 1 = 10.54 and 9.25 at I = 0.1 and 1 mol·L?1, respectively), while the effect of (CH3)4NCl concentration is lower. Based on the total solubility S T and the protonation constant data at different salt concentrations, the solubility of the neutral species S 0 and the solubility products K S0 are obtained. The Setschenow coefficients k m and the solubility values S 0 0 in pure water are also reported (S 0 0 = 0.55, 0.21 and 0.75 mmol·kg?1 for EDDS, EGTA and CDTA, respectively). The dependence of the protonation constants on ionic strength is also interpreted in terms of ion pair formation, and the formation constants of Na+ species are reported. 相似文献