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91.
First total syntheses of the isoechinulin-type alkaloids: Tardioxopiperazine A, Isoechinulin A, and Variecolorin C have been achieved from a common key intermediate 5, which was derived from a regiocontrolled Stille cross-coupling reaction of an allylindium reagent. 相似文献
92.
Xu ZL Wang H Shen YD Nichkova M Lei HT Beier RC Zheng WX Yang JY She ZG Sun YM 《The Analyst》2011,136(12):2512-2520
The type of hapten linkage to a carrier protein can play an important role in determining the nature of the resulting antibody response. Generic haptens using three types of linkers were synthesized (a monocarboxylic acid, an unsaturated hydrocarbon and a carboxamido spacer). These haptens were conjugated to bovine serum albumin (BSA) and used as immunogens to produce broad-specificity monoclonal antibodies (MAbs) to organophosphorus pesticides (OPs). Three-dimensional (3D) structures of hapten-lysine conjugates were optimized using molecular modeling (MM) to mimic conformations of hapten-BSA conjugates. The results from MM studies revealed a change of the 3D conformation and electrostatic potential of hapten 1 when the monocarboxylic acid linker was coupled to lysine. This result was consistent with the observed high-cross-reactivity of the corresponding MAb-H1 for the OPs. The competitive indirect enzyme-linked immunosorbent assay based on MAb-H1 is ideally suited to be used as a screening method for OP contaminants. 相似文献
93.
Chang‐Xin Zhou Xue‐Yao Wang Jian‐Xia Mo Jian Zhang Li‐She Gan 《Helvetica chimica acta》2011,94(2):347-354
Two new indolizidine alkaloids, (±)‐3‐oxoisoelaeocarpine ( 1 ) and (±)‐elaeocarpine N‐oxide ( 2 ), along with three known alkaloids, (±)‐isoelaeocarpine ( 3 ), (±)‐elaeocarpine ( 4 ), and (?)‐isoelaeocarpiline ( 5 ), were isolated from an EtOH extract of the branches and leaves of Elaeocarpus sphaericus. The structures of these compounds were determined by spectroscopic and chemical methods. Furthermore, enantiomers of compounds 1 and 3 were separated on a chiral CD‐Ph column, and their absolute configurations were determined by TD‐DFT (=time‐dependent density‐functional theory) quantum‐chemical calculations of their electronic circular dichroism (ECD) spectra. 相似文献
94.
95.
She Ying Dong Chun Xia Xue Ting Lin Huang College of Sciences Xi''''an University of Architecture Technology Xi''''an Shaanxi China School of Environment Municipal Engineering Xi''''an University of Architecture Technology Xi''''an Shaanxi China 《中国化学快报》2007,18(6):726-729
The interaction between clarithromycin (CAM) and bovine serum albumin (BSA) was investigated using linear-sweep voltammetry in pH 7.4 phosphate buffer solution where CAM caused two irreversible reduction waves P2 and P3 on mercury electrode. The study showed that the formation constant and formation ratio for the interaction between CAM and BSA were 1.51×1012 and 3:1 for P2,4.53×105 and 1:1 for P3, respectively. The ion strength enhanced the hydrophobic interaction between CAM and BSA. 相似文献
96.
97.
A method for improving the quality of all-optical switching is presented. Pumping poly(methyl methacrylate) (PMMA) films doped with azobenzene chromophore Disperse Red 1 (DR1) with two beams (a linearly and a circularly polarized), all-optical switching effects with very low background and high stability are demonstrated. High frequency switching, which is hard to be realized under pump of a single beam, is obtained. The circularly polarized pump beam can erase the photoinduced birefringence and quicken the relaxation process, thus lowering the background and improving the stability and the extinction ratio of the switching signal. PACS 42.70.Jk; 42.25.Lc; 82.30.Qt; 78.20.Fm; 77.80.Fm 相似文献
98.
Certificateless signature: a new security model and an improved generic construction 总被引:2,自引:0,他引:2
Bessie C. Hu Duncan S. Wong Zhenfeng Zhang Xiaotie Deng 《Designs, Codes and Cryptography》2007,42(2):109-126
Certificateless cryptography involves a Key Generation Center (KGC) which issues a partial key to a user and the user also
independently generates an additional public/secret key pair in such a way that the KGC who knows only the partial key but
not the additional secret key is not able to do any cryptographic operation on behalf of the user; and a third party who replaces
the public/secret key pair but does not know the partial key cannot do any cryptographic operation as the user either. We
call this attack launched by the third party as the key replacement attack. In ACISP 2004, Yum and Lee proposed a generic
construction of digital signature schemes under the framework of certificateless cryptography. In this paper, we show that
their generic construction is insecure against key replacement attack. In particular, we give some concrete examples to show
that the security requirements of some building blocks they specified are insufficient to support some of their security claims.
We then propose a modification of their scheme and show its security in a new and simplified security model. We show that
our simplified definition and adversarial model not only capture all the distinct features of certificateless signature but
are also more versatile when compared with all the comparable ones. We believe that the model itself is of independent interest.A
conventional certificateless signature scheme only achieves Girault’s Level 2 security. For achieving Level 3 security, that
a conventional signature scheme in Public Key Infrastructure does, we propose an extension to our definition of certificateless
signature scheme and introduce an additional security model for this extension. We show that our generic construction satisfies
Level 3 security after some appropriate and simple modification.
A preliminary version of the extended abstract of partial results appeared in ACISP 2006 [9]. 相似文献
99.
克尔型非线性薄膜波导的TE模 总被引:4,自引:1,他引:3
对于芯区为克尔型非线性介质,覆盖层和衬底为线性介质的平板波导,用Krylov-Bogoliubov-Mitropolsky的渐近法导出了色散方程及场分布的二阶近似数学表达式,计算量大为减少且结果精确。给出了对称和非对称情况的典型实例。 相似文献
100.