Asymmetric synthesis of steroidal Tröger's base analogues. X-Ray molecular structure of methyl 3?,12?-{6H,12H-5,11-methanodibenzo[b,f][1,5]diazocine-2,8-bisacetoxy}-5?-cholan-24-oate

Cyclization of compound 5c in trifluoroacetic acid/hexamethylenetetramine produces Tröger's base analogue 6c in 75% yield with 70% diastereoselectivity.

Design and realization of high-performance wave-pipelined 8×8 b multiplier in CMOS technology

Wave pipelining is a design technique for increasing the throughput of a digital circuit or system without introducing pipelining registers between adjacent combinational logic blocks in the circuit/system. However, this requires balancing of the delays along all the paths from the input to the output which comes the way of its implementation. Static CMOS is inherently susceptible to delay variation with input data, and hence, receives a low priority for wave pipelined digital design. On the other hand, ECL and CML, which are amenable to wave pipelining, lack the compactness and low power attributes of CMOS. In this paper we attempt to exploit wave pipelining in CMOS technology. We use a single generic building block in Normal Process Complementary Pass Transistor Logic (NPCPL), modeled after CPL, to achieve equal delay along all the propagation paths in the logic structure. An 8×8 b multiplier is designed using this logic in a 0.8 ?m technology. The carry-save multiplier architecture is modified suitably to support wave pipelining, viz., the logic depth of all the paths are made identical. The 1 mm×0.6 mm multiplier core supports a throughput of 400 MHz and dissipates a total power of 0.6 W. We develop simple enhancements to the NPCPL building blocks that allow the multiplier to sustain throughputs in excess of 600 MHz. The methodology can be extended to introduce wave pipelining in other circuits as well

Synthetic approaches to homogynolides A and B

A four step, efficient and general methodology for the conversion of a cyclic ketone into the corresponding alpha-spiro-beta-methylene-gamma-butyrolactone, the key structural feature present in tricyclic sesquiterpenes bakkanes, has been developed employing a regiospecific 5-exo dig radical cyclisation reaction as the key step. The methodology has been extended to the total synthesis of bakkanes including homogynolide-B and chiral homogynolide-A.

What makes a cell tick? The A, B and C of the matter

Nuclear lamina in an eukaryotic cell is primarily composed of the lamins A, B and C. The A type lamins are found only in differentiated cell types while the B type lamins are present both in differentiated and undifferentiated cells. Lamin B interacts with the inner nuclear membrane, In recent years there have been extensive studies on the relationship between the dynamic state of lamin B and the nuclear envelope integrity with respect to the fate of a particular cell, In this article, we have analysed the recent developments and have considered the sequence of events that might be contributing to the fate of a cell either to undergo normal cell division or uncontrolled cellular proliferation or apoptosis.

Enantioselective total synthesis of iso-cladospolide B, cladospolide C and cladospolide B from tartaric acid

The enantioselective synthesis of the natural products cladospolide B, cladospolide C, and iso-cladospolide B has been accomplished from tartaric acid. Key reactions in the synthetic sequence include the elaboration of a gamma-hydroxy amide derived from tartaric acid via alkene cross metathesis, Yamaguchi lactonization, and ring closing metathesis. (C) 2011 Elsevier Ltd. All rights reserved.

B Physics: WHEPP-XI working group report

We present the report of the B physics working group of the Workshop on High Energy Physics Phenomenology (WHEPP-XI), held at the Physical Research Laboratory, Ahmedabad, in January 2010.

Synthesis and biological evaluation of novel 2-aralkyl-5-substituted-6-(4 `-fluorophenyl)-imidazo2,1-b]1,3,4]thiadiazole derivatives as potent anticancer agents

Levamisole, the imidazo2,1-b]thiazole derivative has been reported as a potential antitumor agent. In the present study, we synthesized, characterized and evaluated biological activity of its novel analogues with substitution in the aralkyl group and on imidazothiadiazole molecules with same chemical backbone but different side chains namely 2-aralkyl-6-(4'-fluorophenyl)-imidazo2,1-b]1,3,4]thiadiazoles (SCR1), 2-aralkyl-5-bromo-6-(4'-fluorophenyl)-imidazo2,1-b]1,3,4]-thiadiaz oles (SCR2), 2-aralkyl-5-formyl-6-(4'-fluorophenyl)-imidazo2,1-b]1,3,4]-thiadia zoles (SCR3) and 2-aralkyl-5-thiocyanato-6-(4'-fluorophenyl)-imidazo2,1-b]1,3,4]-th iadiazoles (SCR4) on leukemia cells. The cytotoxic studies showed that 3a, 4a, and 4c exhibited strong cytotoxicity while others had moderate cytotoxicity. Among these we chose 4a (IC50, 8 mu M) for understanding its mechanism of cytotoxicity. FACS analysis in conjunction with mitochondrial membrane potential and DNA fragmentation studies indicated that 4a induced apoptosis without cell cycle arrest suggesting that it could be used as a potential chemotherapeutic agent. (C) 2011 Elsevier Masson SAS. All rights reserved.

LiSr1.65 square 0.35B1.3B ' O-1.7(9) (B = Ti, Zr; B ' = Nb, Ta): New lithium ion conductors based on the perovskite structure

We describe the design and synthesis of new lithium ion conductors with the formula, LiSr(1.65)rectangle(0.35)B(1.3)B'O-1.7(9) (rectangle = vacancy; B = Ti, Zr; B' = Nb, Ta), on the basis of a systematic consideration of the composition-structure-property correlations in the well-known lithium-ion conductor, La-(2/3-x)Li(3x)rectangle((1/3)-2x)TiO3 (I), as well as the perovskite oxides in Li-A-B,B'-O (A = Ca, Sr, Ba; B = Ti, Zr; B' = Nb, Ta) systems. A high lithium-ion conductivity of ca. 0.12 S/cm at 360 degrees C is exhibited by LiSr(1.65)rectangle(0.35)Ti(1.3)Ta(1.7)O(9) (III) and LiSr(1.65)rectangle(0.35)Zr(1.3)Ta(1.7)O(9) (IV), of which the latter containing stable Zr(IV) and Ta(V) oxidation states is likely to be a candidate electrolyte material for all-solid-state lithium battery application. More importantly, we believe the approach described here could be extended to synthesize newer, possibly better, lithium ion conductors.

J. B. S. Haldane, Ernst Mayr and the Beanbag Genetics Dispute

Starting from the early decades of the twentieth century, evolutionary biology began to acquire mathematical overtones. This took place via the development of a set of models in which the Darwinian picture of evolution was shown to be consistent with the laws of heredity discovered by Mendel. The models, which came to be elaborated over the years, define a field of study known as population genetics. Population genetics is generally looked upon as an essential component of modern evolutionary theory. This article deals with a famous dispute between J. B. S. Haldane, one of the founders of population genetics, and Ernst Mayr, a major contributor to the way we understand evolution. The philosophical undercurrents of the dispute remain relevant today. Mayr and Haldane agreed that genetics provided a broad explanatory framework for explaining how evolution took place but differed over the relevance of the mathematical models that sought to underpin that framework. The dispute began with a fundamental issue raised by Mayr in 1959: in terms of understanding evolution, did population genetics contribute anything beyond the obvious? Haldane's response came just before his death in 1964. It contained a spirited defense, not just of population genetics, but also of the motivations that lie behind mathematical modelling in biology. While the difference of opinion persisted and was not glossed over, the two continued to maintain cordial personal relations.

First-principles electronic structure of the delafossites ABO(2) (A=Cu, Ag, Au; B=Al, Ga, Sc, In, Y): evolution of d(10)-d(10) interactions

While bonding between d(10) atoms and ions in molecular systems has been well studied, less attention has been paid to interactions between such seemingly closed shell species in extended inorganic solids. In this contribution, we present visualizations of the electronic structures of the delafossites ABO(2) (A = Cu, Ag, Au) with particular emphasis on the nature of d(10)-d(10) interactions in the close packed plane of the coinage metal ion. We find that on going from Cu to Ag to Au, the extent of bonding between A and A increases. However, the structures (in terms of distances) of these compounds are largely determined by the strongly ionic 13,11 0 interaction and for the larger B ions Sc, In and Y, the A atoms are sufficiently well-separated that A-A bonding is almost negligible. We also analyze some interesting differences between Ag and Au, including the larger A-O covalency of the Au. The trends in electronic structure suggest that the Ag and Au compounds are not good candidate transparent conducting oxides. (C) 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.

Mapping of B-cell epitopes of hemagglutinin protein of rinderpest virus

Monoclonal antibodies (mAbs) against secreted hemagglutinin (H) protein of rinderpest virus (RPV) expressed by a recombinant baculovirus were generated to characterize the antigenic sites on H protein and regions of functional significance. Three of the mAbs displayed hemagglutination inhibition activity and these mAbs were unable to neutralize virus infectivity. Western immunoblot analysis of overlapping deletion mutants indicated that three mAbs recognize antigenic regions at the extreme carboxy terminus (between amino acids 569 and 609) and the fourth mAb between amino acids 512 and 568. Using synthetic peptides, aa 569-577 and 575-583 were identified as the epitopes for E2G4 and D2F4, respectively. The epitopic domains of A12A9 and E2B6 mAbs were mapped to regions encompassing aa 527-554 and 588-609. Two epitopes spanning the extreme carboxy terminal region of aa 573 to 587 and 588 to 609 were shown to be immunodominant employing a competitive ELISA with polyclonal sera form vaccinated cattle. The D2F4 mAb which recognizes a unique epitope on RPV-H is not present on the closely related peste des petits ruminant virus FIN protein and this mAb could serve as a tool in the seromonitoring program after rinderpest vaccination. (C) 2002 Elsevier Science (USA).

Structural model for the Cu-B site of dopamine beta-hydroxylase: Crystal structure of a copper(II) complex showing N3OS coordination with an axial sulfur ligation

A copper(II) complex containing a NSO-donor Schiff base and NN-donor 2,2'-bipyridine has been prepared and structurally characterized. The square pyramidal complex with an axial sulfur ligation is a structural model for the CUB site of dopamine-hydroxylase in its oxidized form. The copper(II) complex is catalytically active in the oxidation of ascorbic acid by dioxygen mediated by a copper(I) species which is proposed to have a four-coordinate structure with a N3S coordination geometry.