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21.
Zouali M 《Applied biochemistry and biotechnology》2000,83(1-3):13-28; discussion 28-9, 145-53
B-cell superantigens (SAgs) interact with normal human nonimmune immunoglobulins (Igs) independently of the light-chain isotype, and activate a large proportion of the B-cell repertoire. Recently, the major envelope protein of human immunodeficiency virus 1 (HIV-1), gp120, was found to exhibit SAg-like properties for B cells with potential pathological consequences for the infected host, including accelerated apoptosis and progressive loss of B cells. This unconventional mode of interaction contrasts with its binding to immunization-induced antibodies, which requires the tertiary structure of the heavy- and light-chain variable regions. Examining the temporal development of V(H)3+ antibodies in HIV-1-infected subjects over a 7-yr period showed that V(H)3+ antibodies specific for the gp120 SAg-binding site are deficient. Quantification of V(H)3+ antibodies, which impart protective responses to infectious agents, in serum samples from HIV-seropositive slow progressors and from patients who progressed to AIDS-related manifestations reveals that paucity in V(H)3+ antibodies is a marker of rapid clinical decline. Remarkably, anti-gp160 V(H)3+ antibodies show a gradual decrease in progressors and vary with time, depending on the viral load. Thus, V(H)3+ antibodies could play an important role in protection, and their underexpression may accelerate disease progression. Investigation of the structural basis of the interaction between human Igs and gp120 shows that the viral gp120 SAg can interact only with a subset of human V(H)3+ Igs. A number of amino acid-positions present primarily in the first and third framework regions of the Ig heavy-chain variable regions correlate with gp120 binding. These residues partially overlap with the Staphylococcus aureus protein A-binding site for V(H)3+ Igs. Overall, these interactions could represent a novel mechanism of humoral deficiency resulting from the capacity of a viral SAg to impact an important subset of the B-cell repertoire and to induce B-cell death by apoptosis. 相似文献
22.
Mejri Imen Kouissi Taoufik Toumi Adel Ouerfelli Noureddine Bounaz Moncef 《Journal of solution chemistry》2021,50(9-10):1131-1168
Journal of Solution Chemistry - Density, speed of sound and viscosity data for the binary mixtures (1,4-dioxane (1)?+?water (2)), were measured over the whole composition range at... 相似文献
23.
Selective Detection of Dopamine in Presence of Ascorbic Acid by Use of Glassy‐Carbon Electrode Modified with Amino‐β‐Cyclodextrin and Carbon Nanotubes
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Aymen Gaied Nejmeddine Jaballah Moncef Tounsi Mohamed Braiek Nicole Jaffrezic‐Renault Mustapha Majdoub 《Electroanalysis》2014,26(12):2747-2753
A glassy carbon electrode modified with per‐6‐amino‐β‐cyclodextrin (β‐CDNH2) and functionalized single‐walled carbon nanotubes (SWCNT‐COOH) was elaborated. This structure was investigated for the detection of dopamine acid (DA) in presence of ascorbic acid (AA). The sensor behavior was studied by cyclic voltammetry, square wave voltammetry and electrochemical impedance spectroscopy. The analysis results show that the electrode modification with CD derivative improves the sensitivity and selectivity of the DA recognition; the electrochemical response was further improved by introduction of SWCNT‐COOH. The sensor shows good and reversible linear response toward DA within the concentration range of 7×10?7–10?4 M with a detection limit of 5×10?7 M. 相似文献
24.
Abstract 1,3-Dipolar cycloaddition reaction of 2-diazopropane 1 with 1,4-benzoquinone 2 carried out at ?20 °C led to a minor mono-cycloadduct 4 and mixture of bis-cycloadducts 6 and 7. The same addition realized with 3H-pyrazole 7 at ?60 °C for 2 h yields a mixture of compounds 8 and 9 and results in O-alkylation. The reaction of 3H-pyrazoles 4 and 7 with dimethylsulfoxide and oxalyl chloride under Swern conditions led to pyrazolenines 11 and 12. 相似文献
25.
In this paper, we give three polynomial algorithms which detect a kernel in comparability graphs relatively to an M-orientation,
in permutation graphs and in P4-free graphs with a normal orientation.
MSC classification:
05C69, 05C85
Correspondence to: Saoula Youcef 相似文献
26.
Moncef Zouali 《Applied biochemistry and biotechnology》1994,47(2-3):135-142
We undertook an analysis of the B cell repertoire at both the germline and somatic levels. To assess the content and organization of the IgH-V and IgK-V loci in SLE, endonuclease-generated polymorphisms were used to characterize individual variations within the human V gene segments. The results are compatible with the conclusion that this disease is not caused by major abnormalities in the structure, size, or organization of the IgV loci. We propose that hyperproduction and lupus-associated autoantibodies arises through a two-stage mechanism whereby a general activation of the multireactive preimmune B-cell repertoire precedes oligoclonal expansion of selected B cell clonotypes. 相似文献
27.
Hatem ElloumiMongi Stambouli Jean Jacques DamelincourtBrahim Mrabet 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,74(6):731-744
In this paper, we present the detail calculations of the indirect spectral irradiance E(λ) as a function of the spectral radiant flux Φt(λ) of a radiating source. This relation is used to predict the integrating cylinder irradiance for a given input radiant flux as a function of the geometrical parameters and reflectivity called “multiplier constant”. The radiation transfer within a cylindrical enclosure composed of three different surfaces, the inside circular surface and the two bases in the ends, has been examined. The configuration factor is introduced. Then all the configuration factors needed for our calculation have been given in analytical form. 相似文献
28.
Amel Haouas Naoufel Ben Hamadi Moncef Msaddek 《Journal of heterocyclic chemistry》2015,52(6):1765-1768
In explorations of synthesis and chemistry of spiroheterocycles, we found that the reaction of 2‐diazopropane with arylidene‐benzofuran‐2(3H)‐one and arylidene‐benzofuran‐3(2H)‐one derivatives generated the spirocyclopropane products. In addition to the expected cycloadducts, an unexpected oxadiazole was formed in some cases. The structures of the obtained adducts have been assigned by means of spectroscopic methods. 相似文献
29.
The reactions of arylnitrile oxides 2 and 2-diazopropane 5 with 5-hydroxy-3-methyl-1,5-dihydropyrrol-2-one derivatives 1 have been studied. 1,3-dipolar cycloaddition of arylnitrile oxides and 2-diazopropane with 5-hydroxy-3-methyl-1,5-dihydropyrrol-2-one derivatives is taking place regiospecifically. The asymmetric induction expected by the chiral centre of the 5-hydroxy-3-methyl-1,5-dihydropyrrol-2-one derivatives was very effective, diastereoisomers 3 and 4 were formed in an approximate 90:10 ratio. The stereoselectivity of the 1,3-dipolar cycloaddition of the 2-diazopropane with the 5-hydroxy-3-methyl-1,5-dihydropyrrol-2-one derivatives are investigated. The attack of the 1,3-dipole occurred from the less hindered face of the dipolarophile, giving the isomer 6. 相似文献
30.
Ali Nel-H Hmidet N Ghorbel-Bellaaj O Fakhfakh-Zouari N Bougatef A Nasri M 《Applied biochemistry and biotechnology》2011,164(7):1096-1110
Alkaline proteases from the viscera of the striped seabream (Lithognathus mormyrus) were extracted and characterized. Interestingly, the crude enzyme was active over a wide range of pH from 6.0 to 11.0, with
an optimum pH at the range of 8.0–10.0. In addition, the crude protease was stable over a broad pH range (5.0–12.0). The optimum
temperature for enzyme activity was 50 °C. The crude alkaline proteases showed stability towards various surfactants and bleach
agents and compatibility with some commercial detergents. It was stable towards several organic solvents and retained more
than 50% of its original activity after 30 days of incubation at 30 °C in the presence of 25% (v/v) dimethyl sulfoxide, N,N-dimethylformamide, diethyl ether, and hexane. The crude enzyme extract was also tested for shrimp waste deproteinization
in the preparation of chitin. The protein removal with a ratio enzyme/substrate of 10 was about 79%. 相似文献