Gorenstein平坦预包络和预解式

我们在［７］中引进了Ｇｏｒｅｎｓｔｅｉｎ平坦模。本文将这类模的刻画推广到任意ｎ－Ｇｏｒｅｎｓｔｅｉｎ环上，并利用这类模刻画了ｎ－Ｇｏｒｅｓｔｅｉｎ环。而且，我们证明了任意ｎ－Ｇｏｒｅｎｓｔｅｉｎ环上Ｇｏｒｅｎｓｔｅｉｎ平坦预包络的存在性，并证得得这种环关于Ｇｏｒｅｎｓｔｅｉｎ平坦模的内射类的整体维数至多为ｎ－２，当ｎ≤１时，该整体维数为零。     

Adaptation of pineal expressed teleost exo-rod opsin to non-image forming photoreception through enhanced Meta II decay

Photoreception by vertebrates enables both image-forming vision and non-image-forming responses such as circadian photoentrainment. Over the recent years, distinct non-rod non-cone photopigments have been found to support circadian photoreception in diverse species. By allowing specialization to this sensory task a selective advantage is implied, but the nature of that specialization remains elusive. We have used the presence of distinct rod opsin genes specialized to either image-forming (retinal rod opsin) or non-image-forming (pineal exo-rod opsin) photoreception in ray-finned fish (Actinopterygii) to gain a unique insight into this problem. A comparison of biochemical features for these paralogous opsins in two model teleosts, Fugu pufferfish (Takifugu rubripes) and zebrafish (Danio rerio), reveals striking differences. While spectral sensitivity is largely unaltered by specialization to the pineal environment, in other aspects exo-rod opsins exhibit a behavior that is quite distinct from the cardinal features of the rod opsin family. While they display a similar thermal stability, they show a greater than tenfold reduction in the lifetime of the signaling active Meta II photoproduct. We show that these features reflect structural changes in retinal association domains of helices 3 and 5 but, interestingly, not at either of the two residues known to define these characteristics in cone opsins. Our findings suggest that the requirements of non-image-forming photoreception have lead exo-rod opsin to adopt a characteristic that seemingly favors efficient bleach recovery but not at the expense of absolute sensitivity.     

Addition of human melanopsin renders mammalian cells photoresponsive

A small number of mammalian retinal ganglion cells act as photoreceptors for regulating certain non-image forming photoresponses. These intrinsically photosensitive retinal ganglion cells express the putative photopigment melanopsin. Ablation of the melanopsin gene renders these cells insensitive to light; however, the precise role of melanopsin in supporting cellular photosensitivity is unconfirmed. Here we show that heterologous expression of human melanopsin in a mouse paraneuronal cell line (Neuro-2a) is sufficient to render these cells photoreceptive. Under such conditions, melanopsin acts as a sensory photopigment, coupled to a native ion channel via a G-protein signalling cascade, to drive physiological light detection. The melanopsin photoresponse relies on the presence of cis-isoforms of retinaldehyde and is selectively sensitive to short-wavelength light. We also present evidence to show that melanopsin functions as a bistable pigment in this system, having an intrinsic photoisomerase regeneration function that is chromatically shifted to longer wavelengths.