Opto-thermal transport engineering in hybrid organic-inorganic lead halide perovskites metasurfaces

Halide perovskites have recently gained widespread attention for their exceptional optoelectronic properties which have been illuminated by extensive spectroscopic investigations. In this article, nanophotonic surface-engineering using soft-lithography has been used to reproduce nanostructures with enhanced functionalities. A non-invasive optical technique based on Raman and photolumines-cence (PL) spectroscopy is employed to investigate the interactive effect of the thermal and optical behaviour in surface-patterned hybrid organic-inorganic halide perovskite thin films. The thermophys-ical properties of the engineered perovskite films are extracted from the softening of the representa-tive peak positions in the Raman and PL spectra of the samples which act as temperature markers. The investigation suggests a comparatively higher rise in the local temperature for the patterned thin films resulting from their enhanced absorption. Therefore, a cross-talk between the opto-thermal transport phenomena in imprinted perovskite thin films pertaining to both enhancing device properties along with maintaining device stability is established

Interactions of the M2δ Segment of the Acetylcholine Receptor with Lipid Bilayers: A Continuum-Solvent Model Study

M2δ, one of the transmembrane segments of the nicotinic acetylcholine receptor, is a 23-amino-acid peptide, frequently used as a model for peptide-membrane interactions. In this and the companion article we describe studies of M2δ-membrane interactions, using two different computational approaches. In the present work, we used continuum-solvent model calculations to investigate key thermodynamic aspects of its interactions with lipid bilayers. M2δ was represented in atomic detail and the bilayer was represented as a hydrophobic slab embedded in a structureless aqueous phase. Our calculations show that the transmembrane orientation is the most favorable orientation of the peptide in the bilayer, in good agreement with both experimental and computational data. Moreover, our calculations produced the free energy of association of M2δ with the lipid bilayer, which, to our knowledge, has not been reported to date. The calculations included 10 structures of M2δ, determined by nuclear magnetic resonance in dodecylphosphocholine micelles. All the structures were found to be stable inside the lipid bilayer, although their water-to-membrane transfer free energies differed by as much as 12 kT. Although most of the structures were roughly linear, a single structure had a kink in its central region. Interestingly, this structure was found to be the most stable inside the lipid bilayer, in agreement with molecular dynamics simulations of the peptide and with the recently determined structure of the intact receptor. Our analysis showed that the kink reduced the polarity of the peptide in its central region by allowing the electrostatic masking of the Gln13 side chain in that area. Our calculations also showed a tendency for the membrane to deform in response to peptide insertion, as has been previously found for the membrane-active peptides alamethicin and gramicidin. The results are compared to Monte Carlo simulations of the peptide-membrane system, as presented in the accompanying article

Interactions of Hydrophobic Peptides with Lipid Bilayers: Monte Carlo Simulations with M2δ

We introduce here a novel Monte Carlo simulation method for studying the interactions of hydrophobic peptides with lipid membranes. Each of the peptide's amino acids is represented as two interaction sites: one corresponding to the backbone α-carbon and the other to the side chain, with the membrane represented as a hydrophobic profile. Peptide conformations and locations in the membrane and changes in the membrane width are sampled using the Metropolis criterion, taking into account the underlying energetics. Using this method we investigate the interactions between the hydrophobic peptide M2δ and a model membrane. The simulations show that starting from an extended conformation in the aqueous phase, the peptide first adsorbs onto the membrane surface, while acquiring an ordered helical structure. This is followed by formation of a helical-hairpin and insertion into the membrane. The observed path is in agreement with contemporary understanding of peptide insertion into biological membranes. Two stable orientations of membrane-associated M2δ were obtained: transmembrane (TM) and surface, and the value of the water-to-membrane transfer free energy of each of them is in agreement with calculations and measurements on similar cases. M2δ is most stable in the TM orientation, where it assumes a helical conformation with a tilt of 14° between the helix principal axis and the membrane normal. The peptide conformation agrees well with the experimental data; average root-mean-square deviations of 2.1 Å compared to nuclear magnetic resonance structures obtained in detergent micelles and supported lipid bilayers. The average orientation of the peptide in the membrane in the most stable configurations reported here, and in particular the value of the tilt angle, are in excellent agreement with the ones calculated using the continuum-solvent model and the ones observed in the nuclear magnetic resonance studies. This suggests that the method may be used to predict the three-dimensional structure of TM peptides

<i>CLN8</i> Gene Compound Heterozygous Variants: A New Case and Protein Bioinformatics Analyses

The CLN8 disease type refers to one of the neuronal ceroid lipofuscinoses (NCLs) which are the most common group of neurodegenerative diseases in childhood. The clinical phenotypes of this disease are progressive neurological deterioration that could lead to seizures, dementia, ataxia, visual failure, and various forms of abnormal movement. In the current study, we describe two patients who presented with atypical phenotypic manifestation and protracted clinical course of CLN8 carrying a novel compound heterozygous variant at the CLN8 gene. Our patients developed a mild phenotype of CLN8 disease: as they presented mild epilepsy, cognitive decline, mild learning disability, attention-deficit/hyperactivity disorder (ADHD), they developed a markedly protracted course of motor decline. Bioinformatic analyses of the compound heterozygous CLN8 gene variants were carried out. Most of the variants seem likely to act by compromising the structural integrity of regions within the protein. This in turn is expected to reduce the overall stability of the protein and render the protein less active to various degrees. The cases in our study confirmed and expanded the effect of compound heterozygous variants in CLN8 disease

Differences in intestinal mucin dynamics between germ-free and conventionally reared chickens after mannan-oligosaccharide supplementation

A germ-free (GF) chicken model was used to test 2 hypotheses: 1. microbial colonization of the gastrointestinal tract (GIT) influences mucin gene expression and mucin types; and 2. mannan oligosaccharide (MOS) supplementation affects GIT cells directly, without bacteria mediation, compared with bacterial-mediated effect (i.e., indirectly). Gnotobiotic isolators were used: 1) GF, 2) with a single bacteria population, and 3) conventionalized by exposure to cecal bacterial contents. Each was divided to 2 diet groups: with or without MOS (2 kg/t) for 1 wk. Results show that the absence of bacteria in the GIT caused a reduction in neutral and acidic goblet cell (GC) number and density, an increase in sulfated mucin, absence of sialylated GC, and reduced mucin 2 mRNA expression in the small intestine of GF compared with conventional birds. These results indicate a reduced development of mucin production and secretion in the absence of GIT bacteria implying a less mature small intestine mucosa, supporting our first hypothesis. Results from the single bacteria population group were not conclusive and did not support any of the hypotheses. Supplementation of MOS, regardless of microbial presence, caused a reduction in neutral GC number and density but increased neutral GC area. The MOS caused different effects on acidic mucins in conventional and GF birds, causing a reduction in sialylated GC number (conventional) and a reduction in sulfated GC density (GF), all supporting a direct effect of MOS in GF animals, in addition to an indirect effect via gut microflora.S. L. Cheled-Shoval, N. S. Withana Gamage, E. Amit-Romach, R. Forder, J. Marshal, A. Van Kessel, and Z. Un