Fluorescence correlation spectroscopy (FCS) is a potential tool to measure the dynamics of fluorescent molecules, either in solution or in a cell. FCS can quantify the diffusion coefficient, the target molecule concentration, and brightness of a single molecule. These parameters allow estimations of the molecular size, the molecular shape, and the affinities of molecular interactions. Moreover, varieties of FCS methods have been developed on the concept of the fluorescence lifetime, triplet state, decrease of fluorescent intensity and toward two-dimensional imaging, in order to reveal the molecular interaction in live cell and molecular crowding.
Opsins are animal photoreceptor proteins that use retinal as their chromophore (ligand) and are classified into several groups based on sequence similarity. Opn5 forms one phylogenetically separate opsin group and includes three vertebrate-specific subgroups, Opn5m, Opn5L1 and Opn5L2. In this article, we introduce highly diversified functionalities of vertebrate Opn5. Three Opn5 subgroups show characteristic spectral sensitivity, preference for retinal isomers and photoreaction process, and work as bistable photoreceptor, retinal chemoreceptor or unidirectional photoreceptor. Such broad spectrum of functionalities may be attributed to optimization for respective physiological functions.
Proteins do not instantaneously finish the synthesis and folding into functioning products, but experience the nascent peptidyl-tRNAs, defined as “nascent chains”, during the translation. So far, nascent chains are regarded as transient intermediates during the protein synthesis. However, recent advances have revealed that nascent chains are directly involved in a variety of cellular processes including self-maturation and the quality control system of protein and mRNA. In this review, we summarize recent progress on noncanonical translation dynamics and co-translational folding.