A small-molecule screen in C. elegans yields a new calcium channel antagonist

Small-molecule inhibitors of protein function are powerful tools for biological analysis and can lead to the development of new drugs. However, a major bottleneck in generating useful small-molecule tools is target identification. Here we show that Caenorhabditis elegans can provide a platform for both the discovery of new bioactive compounds and target identification. We screened 14,100 small molecules for bioactivity in wild-type worms and identified 308 compounds that induce a variety of phenotypes. One compound that we named nemadipine-A induces marked defects in morphology and egg-laying. Nemadipine-A resembles a class of widely prescribed anti-hypertension drugs called the 1,4-dihydropyridines (DHPs) that antagonize the alpha1-subunit of L-type calcium channels. Through a genetic suppressor screen, we identified egl-19 as the sole candidate target of nemadipine-A, a conclusion that is supported by several additional lines of evidence. egl-19 encodes the only L-type calcium channel alpha1-subunit in the C. elegans genome. We show that nemadipine-A can also antagonize vertebrate L-type calcium channels, demonstrating that worms and vertebrates share the orthologous protein target. Conversely, FDA-approved DHPs fail to elicit robust phenotypes, making nemadipine-A a unique tool to screen for genetic interactions with this important class of drugs. Finally, we demonstrate the utility of nemadipine-A by using it to reveal redundancy among three calcium channels in the egg-laying circuit. Our study demonstrates that C. elegans enables rapid identification of new small-molecule tools and their targets.     

Robustness in operational research and decision aiding: A multi-faceted issue

In Introduction, I explain the meaning I give to the qualifier term ”robust” and justify my preference for the expression robustness concern rather than robustness analysis, which I feel is likely to be interpreted too narrowly. In Section 2, I discuss this concern in more details and I try to clarify the numerous raisons d’être of this concern. As a means of examining the multiple facets of robustness concern more comprehensively, I explore the existing research about robustness, attempting to highlight what I see as the three different territories covered by these studies (Section 3). In Section 4, I refer to these territories to illustrate how responses to robustness concern could be even more varied than they currently are. In this perspective, I propose in Section 5 three new measures of robustness. In the last section, I identify several aspects of the problem that should be examined more closely because they could lead to new avenues of research, which could in turn yield new and innovative responses.     

具有两参数的非线性椭圆型方程边值问题解的渐近性态

讨论一类具有双参数的非线性椭圆型方程边值问题. 引入多重尺度变量, 构造问题的形式渐近解. 利用微分不等式理论, 证明边值问题渐近解的存在性和一致有效性. 由解的结构指出, 在两参数一定的情况下,相应问题的解只具有一个边界层.     

一类非线性奇摄动分数阶微分方程的渐近解

研究了一类奇摄动非线性分数阶微分方程边值问题.在适当的条件下,首先求出了原问题的外部解,然后利用伸长变量、合成展开法和幂级数展开理论构造出解的边界层项,并由此得到解的渐近展开式.最后利用微分不等式理论,讨论了问题解的渐近性态,得到了原问题解的一致有效的渐近估计式.     

精度与程度的逻辑或近似算子的性质

本文目的是探讨精度与程度的复合,探索新的粗糙集拓展模型.从精度与程度的逻辑或运算出发,定义了精度与程度的逻辑或粗糙集模型.在该模型中,通过变精度近似与程度近似的转化公式,研究了精度与程度的逻辑或近似算子,并得到了该近似算子的幂作用等性质.用精度与程度的逻辑或粗糙集模型统一了变精度粗糙集模型、程度粗糙集模型和经典粗糙集模型,并在这些粗糙集模型中得到了近似算子幂作用的相应性质.     

Femtosecond study of partially folded states of cytochrome C by solvation dynamics

Using femtosecond time-resolved fluorescence spectroscopy, it is shown that the solvation dynamics in the two partially folded states (IS' and IS' ') of a protein, cytochrome C, are very different. In the case of IS' (formed by the addition of 2 mM sodium dodecyl sulfate, SDS) almost the entire dynamic solvent shift of coumarin 153 (C153) is captured in a picosecond setup and the contribution of the ultrafast component (0.5 ps) is very small (5%). Solvation dynamics of IS' ' (formed by 2 mM SDS and 5 M urea) displays a major component (47%) of 1.3 ps. This indicates that the structure of IS' ' is much more open and exposed compared to that of IS'. The difference in the dynamics of IS' and IS' ' is attributed to differences in their structure, particularly near the heme region, and the presence of urea in IS' '.     

Hinge peptide combinatorial libraries for inhilbitors of botulinum neurotoxins and saxitoxin: Deconvolution strategy

Combinatorial library screening offers a rapid process for identifying potential therapies to toxins. Hinge peptide libraries, which rely on conformational diversity rather than traditional molecular diversity, reduce the need for huge numbers of syntheses and screening steps and greatly expedite the discovery process of active molecules. Hinge peptide libraries having the structures: Acetyl-X₁–X₂–hinge–X₃–X₄–NH₂ (capped) and X₁–hinge–X₂–X₃ (uncapped), where X₁ through X₄ are near-equimolar mixtures of twelve L-amino acids and hinge = 4-aminobutyric acid, were screened for inhibitory activity in bioassays for botulinum neurotoxins A and B (BoNT/A, BoNT/B) and saxitoxin. The zinc protease activity of the reduced light chains of BoNT/A and /B was assayed by measuring the cleavage of synthetic substrates. Saxitoxin activity was measured by the restoration of the viability of neuroblastoma cells treated with ouabain and veratridine. Deconvolution of libraries was accomplished by fixing one position at a time beginning with the C-terminus. Primary library subsets in which position 4 was fixed showed moderate levels of inhibition for BoNT/A. Secondary library subsets showed stronger inhibition in the bioassays. In each of the bioassays, inhibitory potency was stronger when the second position to be fixed was on the opposite side of the hinge, rather than on the same side with respect to the C-terminus, suggesting that the hinge facilitates the interaction of side chains. Inhibitors for all three of the toxins studied were discovered within library subsets, although not necessarily in primary subsets. These studies demonstrate that (1) the best strategy for deconvoluting hinge peptide libraries is by fixing residues alternately on each side of the hinge moiety, and (2) it is essential to investigate secondary subsets even when primary subsets are inactive. The present findings support the concept that the increased flexibility imposed by the inclusion of a central hinge residue in small peptides increases the opportunity for side chain interactions, providing a distinct advantage for hinge peptide libraries over conventional peptide libraries. Hinge peptide libraries are a rich source of novel ligands for modulation of biomechanisms. The library subsets uncovered in this study may possess peptides that will lead to effective therapies to neurotoxin poisoning.     

Lag and anticipatory synchronization based parameter estimation scheme in modulated time-delayed systems

In this article, we have shown that using delay dynamical systems as base, one can use the modulation of the various parameters, to transmit multiple signals through a single chaotic time series. It is shown that under certain conditions the original signals and parameters of the driving signals can be recovered with the help of an adaptive demodulator. An important aspect of the present method is that the communication is possible between two time-delayed systems with parameter mismatch using lag and anticipatory synchronization. The whole idea is presented on the basis of Mackey–Glass system, with variable time delay.