Conformational studies of hexapeptides containing two dehydroamino acid residues in positions 2 and 5 in peptide chain

Conformational preferences of a group of hexapeptides containing two dehydroamino acid residues in Positions 2 and 5 in peptide chain were investigated by means of spectroscopic methods (NMR and CD) and theoretical calculations. In the case of dimethylsulfoxide (DMSO) solution, only peptide with free N-termini adopted rigid 3(10)-helical conformation, for the rest of examined peptides extended and "zig-zag" conformers were predominant. CD measurements showed that only in chloroform solution the conformational freedom of investigated peptides was restricted.     

mAtNOS1 regulates mitochondrial functions and apoptosis of human neuroblastoma cells

mAtNOS1 is a novel gene recently reported in mammalian cells with functions that are not fully understood. The present study generated human neuroblastoma SHSY cells over- and underexpressing mAtNOS1 and shows that mAtNOS1 is involved in regulating mitochondrial nitric oxide, mitochondrial transmembrane potential, protein tyrosine nitration, cytochrome c release, and apoptosis of those cells.     

Peptides as Active Ingredients: A Challenge for Cosmeceutical Industry

Cosmeceutical field, which merges cosmetics and pharmaceuticals, is nowadays a highly investigated research area, because a scientific demonstration of the claimed bioactivity of new cosmeceutical ingredients is increasingly requested. In fact, an aspect differentiating traditional cosmetics from cosmeceuticals is the identification and characterization of the active ingredients and demonstrating its efficacy in the claimed activity. An interesting group of bioactive cosmeceutical ingredients are peptides, which due to their particular properties, meets most of the requirements presented by the cosmeceutical industry when composing new formulas. In this context, beside bioactivity, two additional aspects have been recently considered, when dealing with peptides as cosmeceutical ingredients: bioavailability and stability. We describe herein novel methods applied in order to enhance peptides skin-penetration and stability, reviewing both scientific articles and patents, issued in the cosmeceutical arena.     

Multimarker response to salinity stress in two estuarine bivalves of different genetic diversity: Mya arenaria and Limecola balthica from the Gulf of Gdańsk (southern Baltic Sea)

The estuarine bivalves Limecola balthica and Mya arenaria are common inhabitants of marine soft bottom habitats in the Northern Hemisphere. Both species are able to live under a wide range of environmental conditions including variable salinity. However, in L. balthica there is high genetic variability, and populations are often genetically adapted to local conditions. By contrast, genetic diversity in M. arenaria is low across the species’ geographic range, which attests to acclimatization to different conditions. We hypothesized that individuals of M. arenaria should perform better under osmotic stress. We tested this hypothesis by performing a 5‐week experiment that exposed individuals of both clam species to hypo‐ and hyperosmotic conditions. A multiple biomarker approach that included physiological, biochemical, and histological markers was used to assess bivalve performance. Exposure to the different salinities induced biological responses that particularly affected respiratory activity in both species tested, but these responses were much more pronounced in individuals of L. balthica. The results confirmed the hypothesis that the phenotypic plasticity of M. arenaria was more pronounced and reflected a different strategy of adapting to heterogeneous habitats.     

Response of <Emphasis Type="Italic">Dionaea muscipula</Emphasis> J. Ellis to light stress in in vitro: physiological study

Hyperhydricity can cause significant economic loss for the micro-propagation industry that produces blueberry. In order to predict and control the occurrence of hyperhydricity, better understanding of the anatomical and physiological features of hyperhydric plantlets is required. In this study, we investigated the ultrastructural and physiological changes associated with hyperhydric blueberry plantlets. Compared to normal plantlets, hyperhydric plantlets exhibited reduced cell wall thickness, damaged membrane and guard cell structure, decreased number of mitochondria and starch granule, higher cell vacuolation, more intercellular spaces, and collapse of vascular tissues. In addition, excessive accumulation of reactive oxygen species (ROS) and ethylene, decreased stomatal aperture and water loss, as well as abnormity of stomatal movement were also evident in the hyperhydric plantlets. The results suggested that excessive ethylene and ROS produced in response to the stress arising from in vitro culture could lead to abnormal stomatal closure, causing the accumulation of water in the tissues. This would lead to subsequent induction of oxidative stress (due to hypoxia) and cell damage, especially guard cell structure, eventually giving rise to the symptoms of hyperhydricity. Reducing the content of ethylene and ROS, and protecting the structure and function of the stomata could be considered as potential strategies for inhibiting hyperhydricity or restoring the hyperhydric plants to their normal state.     

TRENDS IN THE EVOLUTION OF THE EUGLENID PELLICLE

Abstract Trends in the evolution of the euglenid pellicle were described using phylogenetic methods on 18S rDNA, morphological, and combined data from 25 mostly phototrophic taxa. The tree topology from a total‐evidence analysis formed a template for a synthetic tree that took into account conflicting results derived from the partitioned datasets. Pellicle character states that can only be observed with the assistance of transmission and scanning electron microscopy were phylogenetically mapped onto the synthetic tree to test a set of previously established homology statements (inferences made independently from a cladogram). The results permitted us to more confidently infer the ancestral‐derived polarities of character state transformations and provided a framework for understanding the key cytoskeletal innovations associated with the evolution of phototrophic euglenids. We specifically addressed the character evolution of (1) the maximum number of pellicle strips around the cell periphery; (2) the patterns of terminating strips near the cell posterior end; (3) the substructural morphology of pellicle strips; (4) the morphology of the cell posterior tip; and (5) patterns of pellicle pores on the cell surface.     

Intra-seasonal variation in zooplankton availability,chick diet and breeding performance of a high Arctic planktivorous seabird

Different phenological responses to climate changes by species representing preys and predators may lead to mismatch between functionally dependent components of an ecosystem, with important effects on its structure and functioning. Here, we investigate within-season variation in zooplankton availability, chick diet composition and breeding performance of a small planktivorous seabird, the little auk (Alle alle) in two large colonies in Hornsund and Magdalenefjorden, Spitsbergen, differing in synchrony of breeding (11-day vs. 22-day hatching period, respectively). Assuming similar zooplankton phenology and existing differences in duration of the little auk breeding period, we expected lower availability of the preferred food in the less synchronized colony in Magdalenefjorden and in consequence a negative effect on nestling body mass and survival. We found that in both colonies Calanus glacialis (copepodite stage CV) was the most important prey item in the chick diet making up 68–87 % of the biomass and energy of all prey items. The only exception was the end of the chick-rearing period in Magdalenefjorden, when contribution of this prey item was significantly lower (24–26 %). Thus, late breeders in Magdalenefjorden were apparently mismatched regarding C. glacialis CV availability. However, the hatching date did not affect birds fitness (reproductive output and chick pre-fledging mass) significantly. Results of our study indicate that little auks breeding on Spitsbergen can respond to a wide range of environmental conditions and prey availabilities through the plasticity of their foraging behaviour, which may help them to maintain their optimum fitness level in changing and unpredictable environments.     

Septins recognize micron-scale membrane curvature

How cells recognize membrane curvature is not fully understood. In this issue, Bridges et al. (2016. J. Cell Biol. http://dx.doi.org/10.1083/jcb.201512029) discover that septins, a component of the cytoskeleton, recognize membrane curvature at the micron scale, a common morphological hallmark of eukaryotic cellular processes.Eukaryotic cells have dedicated proteins that sense membranes, depending on their curvature (Antonny, 2011). Sensors of membrane curvature are important because they organize a wide variety of cellular functions, including vesicle trafficking and organelle shaping (McMahon and Gallop, 2005). Curvature-sensing proteins, for example, the Bin-Amphiphysin-Rvs (BAR) domain–containing proteins, have been mostly described to work at the nanometer scale (Zimmerberg and Kozlov, 2006). In contrast, a clear mechanism of sensing membrane curvature at the micron scale in eukaryotic cells has not been described. In this issue, Bridges et al. discover that septins, a poorly understood component of the cytoskeleton, recognize plasma membrane curvature at the micron scale and serve as landmarks for eukaryotic cells to know their local shape.Septins are an evolutionarily conserved family of GTP-binding proteins that assemble into nonpolar filaments and rings (John et al., 2007; Sirajuddin et al., 2007; Bertin et al., 2008). Septins have been implicated in diverse membrane organization events where micron-scale curvature takes place (Saarikangas and Barral, 2011; Mostowy and Cossart, 2012), including the cytokinetic furrow, the annulus of spermatozoa, the base of cellular protrusions (e.g., cilium and dendritic spines), and the phagocytic cup surrounding invasive bacterial pathogens (Fig. 1). However, the precise role of septin–membrane interactions remains elusive. It was first suggested in 1999 that the interaction of human septins with phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2) is important for septin localization (Zhang et al., 1999). More recently, work using recombinant septins from budding yeast Saccharomyces cerevisiae assembled on PI(4,5)P2 lipid monolayers showed that septins interact with membrane to facilitate filament assembly (Bridges et al., 2014). Membrane-facilitated septin assembly has also been observed using phospholipid liposomes, and in this case septins were also shown to induce membrane tubulation (Tanaka-Takiguchi et al., 2009). Given that (a) septins can interact with membrane, (b) septin assembly is membrane facilitated, and (c) septin assemblies are associated with a variety of membrane organization events from yeast to mammals, Bridges et al. (2016) hypothesized that septins serve as a mechanism to recognize membrane curvature.Open in a separate windowFigure 1.Morphological hallmarks of eukaryotic cells characterized by micron-scale membrane curvature and septin assembly. Septins have been implicated in membrane organization events where micron-scale curvature takes place. (A) A septin ring acts as a scaffold for cytokinesis proteins and forms a diffusion barrier at the cytokinetic furrow of a dividing cell. (B) A septin ring forms a diffusion barrier at the annulus of a mammalian spermatozoon, which separates the anterior and posterior tail. (C) A septin ring forms a diffusion barrier at the base of a cilium to separate the ciliary membrane from the plasma membrane. (D) In neurons, a septin-dependent diffusion barrier can localize at the base of dendritic spine necks. (E) During phagocytosis, a cup is formed at the plama membrane; septin rings assemble at the base of the phagocytic cup to regulate entry.In their new work, Bridges et al. (2016) provide several lines of evidence to support the hypothesis that septins recognize micron-scale curvature. First, using the filamentous fungus Ashbya gossypii, they performed in vivo localization studies and showed that the fungal septin Cdc11a concentrates in regions of positive micron-scale curvature and that the degree of concentration is proportional to the degree of curvature. Moreover, septins localize to curved membranes that also recruit septin-interacting proteins (e.g., the signaling protein Hsl7). These findings indicate that, by acting as curvature-sensing proteins, septins can localize signaling platforms in the cell. To test if septins can differentiate among micron-scale curvatures, Bridges et al. (2016) developed an elegant model system for septin assembly in vitro. They decorated silica beads with anionic phospholipid bilayers and measured the interaction affinity between purified fungal septin complexes and beads of different curvatures. Interestingly, septins were maximally recruited to “intermediate” sized beads (1.0–3.0 µm in diameter), with little to no recruitment to either very large (5.0–6.5 µm in diameter) or very small (0.3 µm in diameter) beads. These results indicate that septin filaments preferentially localize to a curvature (κ) of 0.7–2.0 µm⁻¹ in the absence of other cellular factors. To provide additional information on the mechanism of sensing, the authors purified mutant septin complexes that fail to polymerize into filaments and showed that the affinity of septins for micron-scale membrane curvature does not require filament formation per se. However, septins must polymerize into filaments for stable membrane association. Collectively, in vivo experiments using A. gossypii and in vitro experiments using silica beads highlight that septins have the intrinsic ability to recognize membrane curvature at the micron scale.Finally, to study the recognition of micron-scale membrane curvature beyond fungi, Bridges et al. (2016) turn their attention to human septins. Using tissue culture cells, they observe that the abundance of septins is associated with the degree of membrane curvature. To confirm these observations in vitro, they purified human septins and analyzed their binding affinity to silica beads with phospholipid bilayers. As seen with A. gossypii septins, human septins also showed a preference for beads ∼1.0 µm in diameter, strongly suggesting an evolutionarily conserved property of septins for sensing membrane curvature at the micron scale.Based on their findings, Bridges et al. (2016) propose that septins provide eukaryotic cells with a mechanism to recognize curvature at the micron scale. This feature differentiates septins from other sensor proteins that strictly detect curvature at the nanometer scale (e.g., BAR domain–containing proteins). However, it is likely that septins do more than recognize membrane, and the precise role of septins in membrane recognition remains unknown. The highly conserved structural and biochemical properties of septins suggest they organize, stabilize, and functionalize membrane domains (Caudron and Barral, 2009; Kusumi et al., 2012; Bridges and Gladfelter, 2015). Although we are far from knowing the full repertoire of septin function, this new work by Bridges et al. (2016) reminds us that understanding how membranes can specify septin assembly is essential to understand the role of septins in eukaryotic cells.