Cholesterol binding to G protein-coupled receptors (GPCRs) and modulation of their activities in membranes is a fundamental issue for understanding their function. Despite the identification of cholesterol binding sites in high-resolution x-ray structures of the ?2 adrenergic receptor (β2AR) and other GPCRs, the binding affinity of cholesterol for this receptor and exchange rates between the free and bound cholesterol remain unknown. In this study we report the existence of two classes of cholesterol binding sites in β2AR. By analyzing the β2AR unfolding temperature in lipidic cubic phase (LCP) as a function of cholesterol concentration we observed high-affinity cooperative binding of cholesterol with sub-nM affinity constant. In contrast, saturation transfer difference (STD) NMR experiments revealed the existence of a second class of cholesterol binding sites, in fast exchange on the STD NMR timescale. Titration of the STD signal as a function of cholesterol concentration provided a lower limit of 100 mM for their dissociation constant. However, these binding sites are specific for both cholesterol and β2AR, as shown with control experiments using ergosterol and a control membrane protein (KpOmpA). We postulate that this specificity is mediated by the high-affinity bound cholesterol molecules and propose the formation of transient cholesterol clusters around the high-affinity binding sites.

The addition of cholesterol to the monoolein-based lipidic cubic phase (LCP) has been instrumental in obtaining high-resolution crystal structures of several G protein-coupled receptors. Here, we report the use of high resolution magic angle spinning NMR spectroscopy to record and assign the isotropic 13C chemical shifts of cholesterol in lipidic lamellar and cubic phases at different hydration levels with monoolein and chain deuterated DMPC as host lipids. The hydrogen bonding patterns of cholesterol in these phases were determined from the NMR data by quantum chemical calculations. The results are consistent with the normal orientation of cholesterol in lipid bilayers and with the cholesterol hydroxyl group located at the hydrophobic/hydrophilic interface. The 13C chemical shifts of cholesterol are mostly affected by the host lipid identity with little or no dependency on the hydration (20% vs. 40%) or the phase identity (lamellar vs. LCP). In chain deuterated DMPC bilayers, the hydroxyl group of cholesterol forms most of hydrogen bonds with water, while in monoolein bilayers it predominately interacts with monoolein. Such differences in the hydrogen-bonding network of cholesterol may have implications for the design of experiments in monoolein-based LCP.

Although vitamin D3 (VD3), which is the main form of vitamin D, can be produced in human skin under the sunlight, vitamin D deficiency emerged as a major public health problem worldwide. Mainly, oral supplements or vitamin D-fortified foods are distributed to help supplementation of vitamin D. However, those oral methods are limitedly supplied in the Middle East countries, and oral absorption has low efficiency due to many barriers and various changes of conditions along the route. Then, it is recommended to take them every day in order to maintain the adequate serum level of vitamin D. Alternatively, transdermal delivery system could provide a convenient way to get sustained supplement of vitamin D by its advantages like avoiding first-pass effect of the liver and providing release for long periods of time. In this study, we introduced transdermal delivery system for sustained vitamin D release using coating microneedles that easily pierce the skin layer with enough mechanical strength and allow the localization of drugs within the dermal region. According to the experimental results, poly (lactic-co-glycolic acid) (PLGA) successfully encapsulated VD3 as a nanoparticle form with appropriate properties for transdermal delivery such as size distribution, skin compatibility, and effective release of encapsulated compound. Finally, PVD3 layers coated on solid microneedles were completely dissolved into intradermal region in porcine skin model and revealed better performance for VD3 release into plasma compared to ointment base transdermal method.

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The physiological state of a cell is governed by a multitude of processes and can be described by a combination of mechanical, spatial and temporal properties. Quantifying cell dynamics at multiple scales is essential for comprehensive studies of cellular function, and remains a challenge for traditional end-point assays. We introduce an efficient, non-invasive computational tool that takes time-lapse images as input to automatically detect, segment and analyze unlabeled live cells; the program then outputs kinematic cellular shape and migration parameters, while simultaneously measuring cellular stiffness and viscosity. We demonstrate the capabilities of the program by testing it on human mesenchymal stem cells (huMSCs) induced to differentiate towards the osteoblastic (huOB) lineage, and T-lymphocyte cells (T cells) of naïve and stimulated phenotypes. The program detected relative cellular stiffness differences in huMSCs and huOBs that were comparable to those obtained with studies that utilize atomic force microscopy; it further distinguished naïve from stimulated T cells, based on characteristics necessary to invoke an immune response. In summary, we introduce an integrated tool to decipher spatiotemporal and intracellular dynamics of cells, providing a new and alternative approach for cell characterization.

Abstract-Memristors have been suggested as neuromorphic computing elements. Spike-time dependent plasticity and the Hodgkin-Huxley model of the neuron have both been modelled effectively by memristor theory. The d.c. response of the memristor is a current spike. Based on these three facts we suggest that memristors are well-placed to interface directly with neurons. In this paper we show that connecting a spiking memristor network to spiking neuronal cells causes a change in the memristor network dynamics by: removing the memristor spikes, which we show is due to the effects of connection to aqueous medium; causing a change in current decay rate consistent with a change in memristor state; presenting more-linear I − t dynamics; and increasing the memristor spiking rate, as a consequence of interaction with the spiking neurons. This demonstrates that neurons are capable of communicating directly with memristors, without the need for computer translation.

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