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991.
Vivian?Regina?Trist?o Fernando?Felippe?de?Carvalho Cinthia?Zanini?Gomes Adriana?Regina?Miranda Cíntia?C.?Vequi-Suplicy Maria?Teresa?Lamy Nestor?Schor Maria?Helena?Bellini 《Journal of fluorescence》2010,20(3):665-669
The progression to end-stage renal failure is independent of the initial pathogenic mechanism. Metabolic acidosis is a common
consequence of chronic renal failure that results from inadequate ammonium excretion and decreased tubular bicarbonate reabsorption.
Protoporphyrin IX (PpIX) is the immediate metabolic precursor of the heme molecule. The purpose of this study was to evaluate
the levels of erythrocytes protoporphyrin IX at an animal model during progressive renal disease. A total of 36 eight-week-old
male Wistar rats were divided into six groups: Normal, 4 and 8 weeks after 5/6 nephrectomy (NX). Renal function was evaluated
by creatinine clearance and plasma creatinine levels. The autofluorescence of erythrocytes porphyrin of healthy and NX rats
was analyzed using fluorescence spectroscopy. Emission spectra were obtained by exciting the samples at 405 nm. Significant
differences between normal and NX rats autofluorescence shape occurred in the 600–700 nm spectral region. A correlation was
observed between emission band intensity at 635 nm and progression of renal disease. 相似文献
992.
Carlos?M.?Matias Jo?o?M.?Sousa M.?Emília?Quinta-Ferreira Mona?Arif Hugh?D.?Burrows 《Journal of fluorescence》2010,20(1):377-380
Fura-2 is widely used as a fluorescent probe to monitor dynamic changes in cytosolic free calcium in cells, where Ca2+ can enter through several types of voltage-operated or ligand-gated channels. However, Fura-2 is also sensitive to other
metal ions, such as zinc, which may be involved in ionic channels and receptors. There is interest, in particular, in studying
the synapses between mossy fibers and CA3 pyramidal cells which contain both calcium and high quantities of free or loosely
bound zinc. We have found, through fluorescence probing, that endogenous zinc inhibits mossy fiber calcium transients. However,
since these results might be explained by an effect of the zinc chelator N,N,N’,N’-tetrakis(2-pyridylmethyl)ethylenediamine
(TPEN) on the spectral properties of Fura-2, we have carried out a validation of the method through fluorescence excitation
spectra of the complex Fura-2/calcium, and show that TPEN does not affect these spectra. This supports the idea that the observed
calcium enhancement is related to a zinc inhibition of presynaptic calcium mechanisms, and confirms the use of the chelator
TPEN as a general procedure for the biophysical study of Ca(II) in the presence of Zn(II) using Fura-2. 相似文献
993.
994.
Juvocimene I is prepared by a non ambiguous synthesis based on the regioselective alkylation of 4-methylhexa-2,4-dienoic acid, and Wittig olefination of the aldehyde corresponding to the alkylated acid. 相似文献
995.
Photonic crystal behavior of a rotating Bose-Einstein condensate with a triangular vortex lattice is reviewed and a scheme for getting much wider band gaps is proposed. It is shown that photonic band gaps can be widened an order of magnitude more by using a Raman scheme of index enhancement, in comparison to previously considered upper level microwave scheme. 相似文献
996.
Carlos Alvarez-Ibarra Juan F. Collados Luján María L. Quiroga-Feijóo 《Tetrahedron: Asymmetry》2010,21(19):2334-2345
Enantiopure [(2S,4R)-1-cyclohexyl-4-methylpiperidin-2-yl]methanol 5a and [(2S,4R)-1-cyclohexyl-4-methylpiperidin-2-yl]-(diphenyl)methanol 5b, new β-amino alcohols based on l-pipecolinic acid (homoproline), have been prepared straightforwardly from rac-alaninol and rac-2-amino-1,1-diphenylpropan-1-ol, respectively. The described route constitutes as a model procedure for the preparation of other related C(4) or/and C(3)-substituted 2-piperidinylmethanols.The new chiral ligands have shown a singular behaviour on the stereocontrol of the benchmark reaction of benzaldehyde and diethylzinc compared with other C(4)-unsubstituted analogues prepared by ourselves from l-pipecolinic acid (compounds 5c, 5d, 5e and 5f). The catalytic activity, the sense of asymmetric induction and the degree of the enantioselectivity depend on the appropriate combination of the substituents on the structural scaffold, but also on the metal-alkoxide involved in the catalysis (zinc or lithium alkoxides). The enantioselective addition of diethylzinc to benzaldehyde mediated by ligands 5a and 5c has been studied with DFT methods. The theoretical evaluation was performed in connection with a working hypothesis based on the different loadings of cis- and trans-catalysts in the reaction medium. 相似文献
997.
Noe Oña Antonio Romero Carmen Assiego Claudia Bello Pierre Vogel M. Soledad Pino-González 《Tetrahedron: Asymmetry》2010,21(17):2092-2099
An approach to the synthesis of polyhydroxyazepane derivatives from sugar-based epoxyamides or epoxyalcohols, in which the total regioselective epoxide opening by nitrogen nucleophiles is the key step, is described. Thus, novel polyhydroxyazepane carboxamides and aminomethyl polyhydroxyazepanes, with potential pharmacological interest, are synthesized from diacetone d-mannose. Configurational assignments of the obtained products were determined. 相似文献
998.
999.
1000.
A different approach to enzyme kinetics stressing the cyclic nature of the catalytic process is presented. The time-dependence
of the substrate concentration is derived in a simple way not invoking the quasi-steady-state approximation. According to
this approach the turnover rate can be written as the ratio of two parameters with a direct meaning: enzyme efficiency and
average cycle duration. Real kinetic data for two enzyme-substrate pairs is used to show that the enzyme kinetic efficiency
is best measured by the turnover rate. 相似文献