β-Cyclodextrin as a Precursor to Holey C-Doped g-C3 N4 Nanosheets for Photocatalytic Hydrogen Generation

A green, template-free and easy-to-implement strategy was developed to access holey g-C₃ N₄ (GCN) nanosheets doped with carbon. The protocol involves heating dicyandiamide with β-cyclodextrin (βCD) prior to polymerization. The local symmetry of the GCN skeleton is broken, yielding CxGCN (x corresponds to the initial amount of βCD used) with pores and a distorted structure. The electronic, emission, optical and textural properties of the best-performing material, C2GCN, were significantly modified as compared to bulk GCN. The spectroscopic and luminescent features of C2GCN show the characteristic π-π* electronic transition of GCN, accompanied by much stronger n-π* electronic transitions owing to the porous and distorted network. These new electronic transitions, along with the presence of additional carbon synergistically contributed to enhanced visible light absorption and restrained recombination of electron-hole pairs. Steady-state and time-resolved photoluminescence showed an effective quench of the fluorescence emission, accompanied by a decrease of fluorescence lifetime of C2GCN (2.20 ns) in comparison with GCN (5.85 ns), owing to the delocalization of electron and holes to new recombination centers. The photocatalytic activity of C2GCN was attributed to efficient charge carrier separation and improved visible-light absorbing ability. As result, C2GCN exhibited ∼5 times higher photocatalytic H₂ generation under visible light than bulk GCN.

Membrane Order Is a Key Regulator of Divalent Cation-Induced Clustering of PI(3,5)P2 and PI(4,5)P2

Although the evidence for the presence of functionally important nanosized phosphorylated phosphoinositide (PIP)-rich domains within cellular membranes has accumulated, very limited information is available regarding the structural determinants for compartmentalization of these phospholipids. Here, we used a combination of fluorescence spectroscopy and microscopy techniques to characterize differences in divalent cation-induced clustering of PI(4,5)P₂ and PI(3,5)P₂. Through these methodologies we were able to detect differences in divalent cation-induced clustering efficiency and cluster size. Ca²⁺-induced PI(4,5)P₂ clusters are shown to be significantly larger than the ones observed for PI(3,5)P₂. Clustering of PI(4,5)P₂ is also detected at physiological concentrations of Mg²⁺, suggesting that in cellular membranes, these molecules are constitutively driven to clustering by the high intracellular concentration of divalent cations. Importantly, it is shown that lipid membrane order is a key factor in the regulation of clustering for both PIP isoforms, with a major impact on cluster sizes. Clustered PI(4,5)P₂ and PI(3,5)P₂ are observed to present considerably higher affinity for more ordered lipid phases than the monomeric species or than PI(4)P, possibly reflecting a more general tendency of clustered lipids for insertion into ordered domains. These results support a model for the description of the lateral organization of PIPs in cellular membranes, where both divalent cation interaction and membrane order are key modulators defining the lateral organization of these lipids.

Long term post PrePex male circumcision outcomes in an urban population in Uganda: a cohort study

Objective

The objective of this study was to determine the long term adverse events profile at least a year after safe male circumcision.

Results

A cohort study, investigating patients who had undergone a non surgical circumcision procedure called Prepex. The study variables included scar appearance and sexual experiences. Clients were contacted for a phone interview and data were collected using a questionnaire, for some, a physical examination was done. We obtained ethical committee approval. Data from 304 out of a possible 625 men were analyzed, the rest was lost to follow up. The follow up period was 12–24 months. The mean age was 28 years. Up to 97% were satisfied with the penile scar appearance and the absence of pain. There was no keloids formation, though one developed a hypertrophic scar. Participants reported improved sexual intercourse enjoyment (post circumcision). Up to 17% resumed sexual intercourse before the 6-week long mandatory abstinence period. The average self-reported healing time was 4.7 weeks. There was a high level of scar appearance satisfaction, there was no keloids formation. There was a perceived improvement of sexual enjoyment after circumcision.

Trial registration ClinicalTrials. Gov Identifier: NCT02245126 (Date of registration: September 19, 2014)

Time-resolved fluorescence in lipid bilayers: selected applications and advantages over steady state

Fluorescence methods are versatile tools for obtaining dynamic and topological information about biomembranes because the molecular interactions taking place in lipid membranes frequently occur on the same timescale as fluorescence emission. The fluorescence intensity decay, in particular, is a powerful reporter of the molecular environment of a fluorophore. The fluorescence lifetime can be sensitive to the local polarity, hydration, viscosity, and/or presence of fluorescence quenchers/energy acceptors within several nanometers of the vicinity of a fluorophore. Illustrative examples of how time-resolved fluorescence measurements can provide more valuable and detailed information about a system than the time-integrated (steady-state) approach will be presented in this review: 1), determination of membrane polarity and mobility using time-dependent spectral shifts; 2), identification of submicroscopic domains by fluorescence lifetime imaging microscopy; 3), elucidation of membrane leakage mechanisms from dye self-quenching assays; and 4), evaluation of nanodomain sizes by time-resolved Förster resonance energy transfer measurements.

Religious and spiritual implication in the assessment and management of bipolar disorder

Introduction

Religion/spirituality and medicine have been related in one way or another sense the beginning of our know History. Patients’ beliefs, values and practices influence the way disease is perceived and managed. In order to provide adequate care the physician must have proper knowledge of the patients’ spiritual/religious context, otherwise it may fall prey to errors of diagnostic, inappropriate management and subsequent poor compliance.

Objectives

To present the case of an adult male (a preacher whose beliefs include mediunity) with delusional ideation of mystical content and mood elation, identified during a religious ceremony.

Aims

Questioning the frontier between spiritual/religious beliefs and psychopathology.

Methods

A case report is presented and a literature review of the theme is shortly surveyed.

Results

The case reports to a 53 years old man, who during a religious ceremony presented himself with agitation and disinhibition, removing all his cloths and living the church naked. Additionally it was identified the presence of insomnia, heteroaggressiveness, accelerated speech, mood elation and delusional ideation of mystical and megalomaniac content. Several studies demonstrate the importance of acknowledging the religious/spiritual beliefs of patients. This knowledge allows the psychiatry to correctly identify the existing psychopathology and organize an appropriate intervention plan for the patient.

Conclusions

Spiritual and religious beliefs’ influence the way disease is perceiver and managed. Physician should collect a brief spiritual story of the patient and learn about the different religious/spiritual beliefs and practices of their community, in order to understand the full dimension of the individual illness.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Implications of immunity and inflammation in schizophrenia and related psychotic disorders

Introduction

Intricate interactions between the immune system and the brain might have important etiological and therapeutic implications for neuropsychiatric brain disorders. A probable association between schizophrenia and the immune system was postulated over a century ago, and is supported by epidemiological and genetic studies pointing to links with infection and inflammation.

Objective

To describe some important areas of research regarding immune response in schizophrenia and related psychotic disorders and discuss potential mechanisms and therapeutic implications of these findings.

Aims

Associations between immune response, inflammation and schizophrenia and related psychotic disorders are reviewed.

Methods

A literature review of the theme is surveyed. Several articles were search on MEDLINE with the keywords: schizophrenia, psychosis, inflammation, immunity, infection.

Results

Schizophrenia is a multifactorial disease. It is associated with multiple genetic loci that confer risk, in addition to developmental and postnatal risk factors. Antipsychotic-naive first-episode psychosis and acute psychotic relapse seems to be associated with increased serum concentrations of interleukin 6 and other proinflammatory cytokines, which are normalized after remission of symptoms with antipsychotic treatment.

Conclusions

Inflammation and immune dysfunction might contribute to cognitive, negative, and positive symptoms in schizophrenia. Identification of specific inflammatory pathways for neuropsychiatric symptoms would provide novel targets for therapeutic intervention.

Disclosure of interest

The authors have not supplied their declaration of competing interest.

Accurate quantification of inter-domain partition coefficients in GUVs exhibiting lipid phase coexistence

Giant unilamellar vesicles (GUVs) with phase coexistence allow for the recovery of inter-domain partition coefficients (K_p) of fluorescent molecules through comparison of fluorescence intensities in each phase.

Deoxycholic acid modulates cell death signaling through changes in mitochondrial membrane properties

Cytotoxic bile acids, such as deoxycholic acid (DCA), are responsible for hepatocyte cell death during intrahepatic cholestasis. The mechanisms responsible for this effect are unclear, and recent studies conflict, pointing to either a modulation of plasma membrane structure or mitochondrial-mediated toxicity through perturbation of mitochondrial outer membrane (MOM) properties. We conducted a comprehensive comparative study of the impact of cytotoxic and cytoprotective bile acids on the membrane structure of different cellular compartments. We show that DCA increases the plasma membrane fluidity of hepatocytes to a minor extent, and that this effect is not correlated with the incidence of apoptosis. Additionally, plasma membrane fluidity recovers to normal values over time suggesting the presence of cellular compensatory mechanisms for this perturbation. Colocalization experiments in living cells confirmed the presence of bile acids within mitochondrial membranes. Experiments with active isolated mitochondria revealed that physiologically active concentrations of DCA change MOM order in a concentration- and time-dependent manner, and that these changes preceded the mitochondrial permeability transition. Importantly, these effects are not observed on liposomes mimicking MOM lipid composition, suggesting that DCA apoptotic activity depends on features of mitochondrial membranes that are absent in protein-free mimetic liposomes, such as the double-membrane structure, lipid asymmetry, or mitochondrial protein environment. In contrast, the mechanism of action of cytoprotective bile acids is likely not associated with changes in cellular membrane structure.

Exploring homo-FRET to quantify the oligomer stoichiometry of membrane-bound proteins involved in a cooperative partition equilibrium

The establishment of protein-protein interactions between membrane-bound proteins is associated with several biological functions and dysfunctions. Here, an analytical framework that uses energy homo transfer to directly probe quantitatively the oligomerization state of membrane-bound proteins engaged in a three-state cooperative partition is presented. Briefly, this model assumes that monomeric protein molecules partition into the bilayer surface and reversibly assemble into oligomers with k subunits. A general equation relating the overall steady-state fluorescence anisotropy of the sample to its fractional labeling was derived by considering explicitly that the anisotropy of mixed oligomers containing i-labeled monomers is inversely proportional to the number of labeled subunits per oligomer (Runnels and Scarlata limit). This method was very robust in describing the electrostatic interaction of Alexa Fluor 488 fluorescently labeled lysozyme (Lz-A488) with phosphatidylserine-containing membranes. The pronounced decrease detected in the fluorescence anisotropy of Lz-A488 always correlated with the system reaching a high membrane surface density of the protein (at a low lipid-to-protein (L/P) molar ratio). The occurrence of energy homo transfer-induced fluorescence depolarization was further confirmed by measuring the anisotropy decays of Lz-A488 under these conditions. A global analysis of the steady-state anisotropy data obtained under a wide range of experimental conditions (variable anionic lipid content of the liposomes, L/P molar ratios and protein fractional labeling) confirmed that membrane-bound Lz-A488 assembled into oligomeric complexes, possibly with a stoichiometry of k = 6 ± 1. This study illustrates that even in the presence of a coupled partition-oligomerization equilibrium, steady-state anisotropy measurements provide a simple and reliable tool to monitor the self-assembly of membrane-bound proteins.

Electrostatically driven lipid-protein interaction: Answers from FRET

Electrostatics govern the association of a large number of proteins with cellular membranes. In some cases, these proteins present specialized lipid-binding modules or membrane targeting domains while in other cases association is achieved through nonspecific interaction of unstructured clusters of basic residues with negatively charged lipids. Given its spatial resolution in the nanometer range, Förster resonance energy transfer (FRET) is a powerful tool to give insight into protein-lipid interactions and provide molecular level information which is difficult to retrieve with other spectroscopic techniques. In this review we present and discuss the basic formalisms of both hetero- and homo-FRET pertinent to the most commonly encountered problems in lipid-protein interaction studies and highlight some examples of implementations of different FRET methodologies to characterize lipid/protein systems in which electrostatic interactions play a crucial role. This article is part of a Special Issue entitled: Lipid-protein interactions.

Quantifying lipid-protein interaction by fluorescence correlation spectroscopy (FCS)

Fluorescence correlation spectroscopy (FCS) is a powerful method to investigate molecular interactions based on the variation of diffusion properties at the single-molecule level. This technique allows studying quantitatively the interaction of fluorescently labeled proteins/peptides with lipid vesicles. Here, we describe how to acquire and analyze FCS partition data in order to accurately determine the protein/peptide partition coefficients between the aqueous and lipid phases. It is shown that the recovery of unbiased partition coefficients from FCS partition curves (fractional amplitude of the bound species versus lipid concentration) requires considering explicitly the Poissonian loading of the lipid vesicles with the fluorescently labeled protein in order to account for the variable liposome brightness in each sample. Additionally, the impact of a trace amount of a fluorescent non-binding component on the partition curves determined by FCS is also discussed.