RESUMO
Thousands of Down syndrome cell adhesion molecule (Dscam1) isoforms and â¼60 clustered protocadhrein (cPcdh) proteins are required for establishing neural circuits in insects and vertebrates, respectively. The strict homophilic specificity exhibited by these proteins has been extensively studied and is thought to be critical for their function in neuronal self-avoidance. In contrast, significantly less is known about the Dscam1-related family of â¼100 shortened Dscam (sDscam) proteins in Chelicerata. We report that Chelicerata sDscamα and some sDscamß protein trans interactions are strictly homophilic, and that the trans interaction is meditated via the first Ig domain through an antiparallel interface. Additionally, different sDscam isoforms interact promiscuously in cis via membrane proximate fibronectin-type III domains. We report that cell-cell interactions depend on the combined identity of all sDscam isoforms expressed. A single mismatched sDscam isoform can interfere with the interactions of cells that otherwise express an identical set of isoforms. Thus, our data support a model by which sDscam association in cis and trans generates a vast repertoire of combinatorial homophilic recognition specificities. We propose that in Chelicerata, sDscam combinatorial specificity is sufficient to provide each neuron with a unique identity for self-nonself discrimination. Surprisingly, while sDscams are related to Drosophila Dscam1, our results mirror the findings reported for the structurally unrelated vertebrate cPcdh. Thus, our findings suggest a remarkable example of convergent evolution for the process of neuronal self-avoidance and provide insight into the basic principles and evolution of metazoan self-avoidance and self-nonself discrimination.
Assuntos
Proteínas de Artrópodes/metabolismo , Artrópodes/metabolismo , Animais , Proteínas de Artrópodes/genética , Artrópodes/classificação , Artrópodes/genética , Moléculas de Adesão Celular/química , Moléculas de Adesão Celular/genética , Moléculas de Adesão Celular/metabolismo , Comunicação Celular , Drosophila/genética , Drosophila/metabolismo , Proteínas de Drosophila/química , Proteínas de Drosophila/genética , Proteínas de Drosophila/metabolismo , Neurônios/metabolismo , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismoRESUMO
Benalaxyl is widely applied as a fungicide during grape planting processing. In this experiment, the stereoselective behavior of benalaxyl was studied during the grape growth and wine-making process. A simple method based on high-performance liquid chromatography (HPLC) equipped with a chiral column and UV detector was established to separate and determine the enantiomers of benalaxyl. Stereoselective degradation of the two enantiomers of benalaxyl was found in grapes. The degradation of both enantiomers followed pseudofirst-order kinetics, and the degradation rate of R-(-)-benalaxyl was faster than S-(+)-benalaxyl. The half-life of R-(-)-benalaxyl was 27 h, while the half-life of S-(+)-benalaxyl was 31 h. The enantiomer fraction value decreased from 0.50 to 0.34 and finally only S-(+)-benalaxyl could be detected. In the fermentation process, both enantiomers of benalaxyl were hardly degraded, and no configuration interconversion was observed. Meanwhile, both enantiomers of benalaxyl showed little influence on the growth of the yeast, consumption of carbon sources, or production of alcohol. The result of this study might provide more sufficient data for the evaluation of food safety and potential risk. Chirality 28:394-398, 2016. © 2016 Wiley Periodicals, Inc.
