Structure and dynamics at soft-matter interfaces play an important role in nature and technical applications. Optical single-molecule investigations are noninvasive and capable to reveal heterogeneities at the nanoscale. In this work we develop an autocorrelation function (ACF) approach to retrieve tracer diffusion parameters obtained from fluorescence correlation spectroscopy (FCS) experiments in thin liquid films at reflecting substrates. This approach then is used to investigate structure and dynamics in 100-nm-thick 8CB liquid crystal films on silicon wafers with five different oxide thicknesses. We find a different extension of the structural reorientation of 8CB at the solid-liquid interface for thin and for thick oxide. For the thin oxides, the perylenediimide tracer diffusion dynamics in general agrees with the hydrodynamic modeling using no-slip boundary conditions with only a small deviation close to the substrate, while a considerably stronger decrease of the interfacial tracer diffusion is found for the thick oxides.

Circular RNAs (circRNAs) are a large class of relatively stable RNA molecules that are highly expressed in animal brains. Many circRNAs have been associated with CNS disorders accompanied by an aberrant wake–sleep cycle. However, the regulation of circRNAs in brain homeostasis over daily light–dark (LD) cycles has not been characterized. Here, we aim to quantify the daily expression changes of circRNAs in physiological conditions in healthy adult animals. Using newly generated and public RNA-Seq data, we monitored circRNA expression throughout the 12:12 h LD cycle in various mouse brain regions. We identified that Cdr1as, a conserved circRNA that regulates synaptic transmission, is highly expressed in the suprachiasmatic nucleus (SCN), the master circadian pacemaker. Despite its high stability, Cdr1as has a very dynamic expression in the SCN throughout the LD cycle, as well as a significant regulation in the hippocampus following the entry into the dark phase. Computational integration of different public datasets predicted that Cdr1as is important for regulating light entrainment in the SCN. We hypothesize that the expression changes of Cdr1as in the SCN, particularly during the dark phase, are associated with light-induced phase shifts. Importantly, our work revises the current beliefs about natural circRNA stability and suggests that the time component must be considered when studying circRNA regulation.

The evolution and functional integration of new genes, especially those that become core to key functions, remains enigmatic. We consider the mammal-specific gene, piggyBac transposable element derived 1 (PGBD1), implicated in neuronal disorders. While it no longer recognises piggyBac transposon-like inverted repeats and transposase functionality having been lost, it has evolved a core role in neural homeostasis. Depletion of PGBD1 triggers accumulation of mammal-specific paraspeckles and neural differentiation. It acts by two modalities, DNA binding and protein-protein interaction. As a transcriptional repressor of (lnc)NEAT1, the backbone of paraspeckles, it inhibits paraspeckle formation in neural progenitor cells (NPCs). At the protein level it is associated with the stress response system, a function partially shared with (lnc)NEAT1. PGBD1 thus presents as an unusual exemplar of new gene creation, being a recently acquired multi-function, multi-modal gene. Mammalian specificity associated with control of a mammal-specific structure implies coevolution of new genes with new functions.