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The Nest is a concave-shaped structural motif in proteins formed by consecutive enantiomeric left-handed (L) and right-handed (R) helical conformation of the backbone. This important motif subsumes many turn and helix capping structures and binds electron-rich ligands. Simple Nests are either RL or LR. Larger Nests (>2 residues long) may be RLR, LRL, RLRL, and so forth, being considered as composed of overlapping simple Nests. The larger Nests remain under-explored despite their widely known contributions to protein function. In our study, we address whether the recurrence of enantiomeric geometry in the larger Nests constrains the peptide backbone such that distinct compositional and conformational preferences are seen compared to simple Nests. Our analysis reveals the critical role of the L helical torsion angle in the formation of larger Nests. This can be observed through the higher propensity of residue or secondary structure combinations in LR and LRL backbone conformation in comparison to RL or RLR, although LR/LRL is considerably lower by occurrence. We also find that the most abundant doublets and triplets in Nests have a propensity for particular secondary structures, suggesting a strong sequence-structure relationship in the larger Nest. Overall, our analysis corroborates distinct features of simple and the larger Nests. Such insights would be helpful towards in-vitro design of peptides and peptidomimetic studies.  相似文献   
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  • Opuntia (Cactaceae) is known for high rates of hybridization and ploidisation, resulting in the formation of new species. The occurrence of two sympatric and closely related species of Opuntia, O. elata and O. retrorsa, in Brazilian Chaco enabled us to test the hypothesis that pre‐zygotic reproductive isolation mechanisms operate in both species.
  • We monitored the flowering period, as well as floral biology, and compared the morphological variation of floral structures through measurements, performed intra‐ and interspecific cross‐pollination tests, and recorded the guild of floral visitors and pollinators.
  • Flowering was seasonal and highly synchronous. Floral biology exhibits similar strategies, and although floral morphology differs significantly in many of the compared structures, such morphological variation does not result in the selection of exclusive pollinators. Floral visitors and pollinators are oligolectic bees shared by both species. Opuntia elata and O. retrorsa are self‐compatible. While interspecific cross‐pollination (bidirectional) resulted in germination, the pollen tube did not penetrate the stigma.
  • Opuntia elata and O. retrorsa are closely related; however, they are isolated and do not hybridise in Brazilian Chaco. We found that both have weak pre‐pollination barriers, but that they are strongly isolated by pollen–pistil incompatibility, i.e. post‐pollination barrier.
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植物与植食性昆虫之间存在着复杂的化学相互作用。一方面,当遭受植食性昆虫为害时,植物能识别植食性昆虫相关分子模式,触发早期信号事件和激素信号转导途径,并由此引起转录组与代谢组重组、直接和间接防御化合物含量升高,最后提高对植食性昆虫的抗性。另一方面,植食性昆虫也能识别植物的防御反应,并能通过分泌效应子、选贮、解毒以及降低敏感性等反防御措施抑制或适应植物的化学防御。深入剖析植物与植食性昆虫的化学互作,不仅可在理论上丰富对昆虫与植物互作关系的理解,而且可在实践上为作物害虫防控新技术的开发提供重要的理论与技术指导。  相似文献   
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Hantavirus (HV), a pathogen of animal infectious diseases that poses a threat to humans, has attracted extensive attention. Clinically, HV can cause hemorrhagic fever with renal syndrome (HFRS) and hantavirus pulmonary syndrome (HPS), between which HFRS is mostly in Eurasia, and HPS is mostly in the Americas. This paper reviews the research progress of small-molecule inhibitors of HV.  相似文献   
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We report the discovery and characterization of a series of benzoisothiazolone inhibitors of PHOSPHO1, a newly identified soluble phosphatase implicated in skeletal mineralization and soft tissue ossification abnormalities. High-throughput screening (HTS) of a small molecule library led to the identification of benzoisothiazolones as potent and selective inhibitors of PHOSPHO1. Critical structural requirements for activity were determined, and the compounds were subsequently derivatized and measured for in vitro activity and ADME parameters including metabolic stability and permeability. On the basis of its overall profile the benzoisothiazolone analogue 2q was selected as MLPCN probe ML086.  相似文献   
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In the flowers ofApios americana the vexillum remains ± in its bud position. In this way, a dark cavity is formed displaying a bright window at its base. Insect visitors are attracted to the hidden inflorescences by scent. In their attempt to reach the window they trigger an explosive release of stigma and pollen. Stigmatic fluid glues pollen to the visitor. All characters of the flower fit well into the myiophilous syndrome and thus flies are expected to be the proper pollinators.Apios americana seems to be the only myiophilous exception within the predominantly melittophilousFabaceae.  相似文献   
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A technique is reported for the long-term application of surface electrodes for ambulatory electromyographic (EMG) recording. Prior to electrode application the surrounding skin is lightly painted with tincture of benzoin. This treatment improves adherence to the skin of disposable electrodes and electrode attachment collars, reduces skin trauma associated with electrode removal, and minimizes sensitivity to electrode adhesives.This research was supported in part by NIH grant No. NS25114.  相似文献   
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