Western Honeybee Drones and Workers (Apis mellifera ligustica) Have Different Olfactory Mechanisms than Eastern Honeybees (Apis cerana cerana)

The honeybees Apis mellifera ligustica (Aml) and Apis cerana cerana (Acc) are two different western and eastern bee species that evolved in distinct ecologies and developed specific antennal olfactory systems for their survival. Knowledge of how their antennal olfactory systems function in regards to the success of each respective bee species is scarce. We compared the antennal morphology and proteome between respective sexually mature drones and foraging workers of both species using a scanning electron microscope, two-dimensional electrophoresis, mass spectrometry, bioinformatics, and quantitative real-time polymerase chain reaction. Despite the general similarities in antennal morphology of the drone and worker bees between the two species, a total of 106 and 100 proteins altered their expression in the drones' and the workers' antennae, respectively. This suggests that the differences in the olfactory function of each respective bee are supported by the change of their proteome. Of the 106 proteins that altered their expression in the drones, 72 (68%) and 34 (32%) were overexpressed in the drones of Aml and Acc, respectively. The antennae of the Aml drones were built up by the highly expressed proteins that were involved in carbohydrate metabolism and energy production, molecular transporters, antioxidation, and fatty acid metabolism in contrast to the Acc drones. This is believed to enhance the antennal olfactory functions of the Aml drones as compared to the Acc drones during their mating flight. Likewise, of the 100 proteins with expression changes between the worker bees of the two species, 67% were expressed in higher levels in the antennae of Aml worker contrasting to 33% in the Acc worker. The overall higher expressions of proteins related to carbohydrate metabolism and energy production, molecular transporters, and antioxidation in the Aml workers compared with the Acc workers indicate the Aml workers require more antennal proteins for their olfactory mechanisms to perform efficient foraging activities than do the Acc worker bees. These data decipher the mechanisms of the western and eastern drone and worker bees acting in response to their different olfactory system in their distinct ecosystem.     

Peptide insertion, positioning, and stabilization in a membrane: insight from an all-atom molecular dynamics simulation

Peptide insertion, positioning, and stabilization in a model membrane are probed via an all-atom molecular dynamics (MD) simulation. One peptide (WL5) is simulated in each leaflet of a solvated dimyristoylglycero-3-phosphate (DMPC) membrane. Within the first 5 ns, the peptides spontaneously insert into the membrane and then stabilize during the remaining 70 ns of simulation time. In both leaflets, the peptides localize to the membrane interface, and this localization is attributed to the formation of peptide-lipid hydrogen bonds. We show that the single tryptophan residue in each peptide contributes significantly to these hydrogen bonds; specifically, the nitrogen heteroatom of the indole ring plays a critical role. The tilt angles of the indole rings relative to the membrane normal in the upper and lower leaflets are approximately 26 degrees and 54 degrees , respectively. The tilt angles of the entire peptide chain are 62 degrees and 74 degrees . The membrane induces conformations of the peptide that are characteristic of beta-sheets, and the peptide enhances the lipid ordering in the membrane. Finally, the diffusion rate of the peptides in the membrane plane is calculated (based on experimental peptide concentrations) to be approximately 6 A(2)/ns, thus suggesting a 500 ns time scale for intermolecular interactions.     

Primary stress response induced by different elements is mediated through auxin signalling in barley root tip

Short-term exposure (15 min) of barley roots to different chemical elements revealed that Cd, Cu, Hg and Pb were the most toxic ones causing a marked root growth inhibition even at µM concentrations. Gd, La, Al, Cr, As, Zn, Ni and Se inhibited root growth to a similar extent only at mM concentrations. Despite the high 20 mM concentration, Co caused only a slight, while Mn, Mg or Ca did not evoke any root growth inhibition. Elements at concentrations inhibiting root growth caused a considerable accumulation of indole-3-acetic acid in the root apex. While Cr, As and Zn inhibited, Cd, Cu, Hg, Pb, Gd, La and Al markedly stimulated the generation of reactive oxygen species in the beginning of differentiation zone. Auxin signalling inhibitor alleviated or prevented root growth inhibition, reactive oxygen species generation and the stimulation of lipoxygenase and glutathione peroxidase activity by various elements, indicating a key role of auxin signalling in the stress response of barley root tip. On the other hand, it did not affect or even had an additive effect on dehydroascorbate reductase and ascorbic acid oxidase activity in combination with different elements. Our results indicate that the primary response of barley roots to the presence of various chemical elements during the short-term treatment is not a specific but rather a general adaptive stress response enabling the plant to survive adverse conditions.     

Determinants and Causes of Neonatal Mortality in Jimma Zone,Southwest Ethiopia: A Multilevel Analysis of Prospective Follow Up Study

Background

Ethiopia is among the countries with the highest neonatal mortality with the rate of 37 deaths per 1000 live births. In spite of many efforts by the government and other partners, non-significant decline has been achieved in the last 15 years. Thus, identifying the determinants and causes are very crucial for policy and program improvement. However, studies are scarce in the country in general and in Jimma zone in particular.

Objective

To identify the determinants and causes of neonatal mortality in Jimma Zone, Southwest Ethiopia.

Methods

A prospective follow-up study was conducted among 3463 neonates from September 2012 to December 2013. The data were collected by interviewer-administered structured questionnaire and analyzed by SPSS V.20.0 and STATA 13. Verbal autopsies were conducted to identify causes of neonatal death. Mixed-effects multilevel logistic regression model was used to identify determinants of neonatal mortality.

Results

The status of neonatal mortality rate was 35.5 (95%CI: 28.3, 42.6) per 1000 live births. Though significant variation existed between clusters in relation to neonatal mortality, cluster-level variables were found to have non-significant effect on neonatal mortality. Individual-level variables such as birth order, frequency of antenatal care use, delivery place, gestation age at birth, premature rupture of membrane, complication during labor, twin births, size of neonate at birth and neonatal care practice were identified as determinants of neonatal mortality. Birth asphyxia (47.5%), neonatal infections (34.3%) and prematurity (11.1%) were the three leading causes of neonatal mortality accounting for 93%.

Conclusions

This study revealed high status of neonatal mortality in the study area. Higher-level variables had less importance in determining neonatal mortality. Individual level variables related to care during pregnancy, intra-partum complications and care, neonatal conditions and the immediate neonatal care practices were identified as determinant factors. Improving antenatal care, intra-partum care and immediate neonatal care are recommended.     

The role of conserved waters in conformational transitions of Q61H K-ras

To investigate the stability and functional role of long-residence water molecules in the Q61H variant of the signaling protein K-ras, we analyzed all available Ras crystal structures and conformers derived from a series of independent explicit solvent molecular dynamics (MD) simulations totaling 1.76 μs. We show that the protein samples a different region of phase space in the presence and absence of several crystallographically conserved and buried water molecules. The dynamics of these waters is coupled with the local as well as the global motions of the protein, in contrast to less buried waters whose exchange with bulk is only loosely coupled with the motion of loops in their vicinity. Aided by two novel reaction coordinates involving the distance (d) between the C(α) atoms of G60 at switch 2 and G10 at the P-loop and the N-C(α)-C-O dihedral (ξ) of G60, we further show that three water molecules located in lobe1, at the interface between the lobes and at lobe2, are involved in the relative motion of residues at the two lobes of Q61H K-ras. Moreover, a d/ξ plot classifies the available Ras x-ray structures and MD-derived K-ras conformers into active GTP-, intermediate GTP-, inactive GDP-bound, and nucleotide-free conformational states. The population of these states and the transition between them is modulated by water-mediated correlated motions involving the functionally critical switch 2, P-loop and helix 3. These results suggest that water molecules act as allosteric ligands to induce a population shift among distinct switch 2 conformations that differ in effector recognition.     

Coherent Control of Gap Plasmons of a Complex Nanosystem by Shaping Driving Femtosecond Pulses

Geometry-based control of local field of coupled plasmonic nanostructures is efficient for optimization of the field intensity. However, it provides weak control over spatial and temporal dynamics of the field and thus unsuitable for experimental studies and practical applications where fixed geometries are needed. In this study, we report on pulsed excitation of strongly coupled plasmonic nanosystem comprised of nanorod and split-ring antenna. The near-field intensities are manipulated by controlling time delay, relative phase, and polarization of the ultrafast excitation pulses. We show that the spectral and spatial intensities of the local fields at the gap regions of the coupled nanosystem can be pronounced by using two identical pulses with least time delay and phase difference. The corresponding temporal intensities of electric near-fields for both parallel and orthogonal polarization of the illumination fields are also briefly discussed. These findings might have implications for controlled excitation of complexly coupled plasmonic nanosystems.     

Segregation of negatively charged phospholipids by the polycationic and farnesylated membrane anchor of Kras

The Kras protein, a member of the Ras family of bio-switches that are frequently mutated in cancer and developmental disorders, becomes functional when anchored to the inner surface of the plasma membrane. It is well known that membrane attachment involves the farnesylated and poylcationic C-terminus of the protein. However, little is known about the structure of the complex and the specific protein-lipid interactions that are responsible for the binding. On the basis of data from extensive (>0.55 μs) molecular dynamics simulations of multiple Kras anchors in bilayers of POPC/POPG lipids (4:1 ratio), we show that, as expected, Kras is tethered to the bilayer surface by specific lysine-POPG salt bridges and by nonspecific farnesyl-phospholipid van der Waals interactions. Unexpectedly, however, only the C-terminal five of the eight Kras Lys side chains were found to directly interact with the bilayer, with the N-terminal ones staying in water. Furthermore, the positively charged Kras anchors pull the negatively charged POPG lipids together, leading to the clustering of the POPG lipids around the proteins. This selective Kras-POPG interaction is directly related to the specific geometry of the backbone, which exists in two major conformational states: 1), a stable native-like ensemble of structures characterized by an extended geometry with a pseudohelical turn; and 2), less stable nonnative ensembles of conformers characterized by severely bent geometries. Finally, although the interface-bound anchor has little effect on the overall structure of the bilayer, it induces local thinning within a persistence length of ∼12 Å. Our results thus go beyond documenting how Kras attaches to a mixed bilayer of charged and neutral lipids; they highlight a fascinating process of protein-induced lipid sorting coupled with the (re)shaping of a surface-bound protein by the host lipids.     

Ras nanoclusters: molecular structure and assembly

H-, N- and K-ras4B are lipid-anchored, peripheral membrane guanine nucleotide binding proteins. Recent work has shown that Ras proteins are laterally segregated into non-overlapping, dynamic domains of the plasma membrane called nanoclusters. This lateral segregation is important to specify Ras interactions with membrane-associated proteins, effectors and scaffolding proteins and is critical for Ras signal transduction. Here we review biological, in vitro and structural data that provide insight into the molecular basis of how palmitoylated Ras proteins are anchored to the plasma membrane. We explore possible mechanisms for how the interactions of H-ras with a lipid bilayer may drive nanocluster formation.     

Synthesis and structure-activity relationship of N-alkyl Gly-boro-Pro inhibitors of DPP4, FAP, and DPP7

The structure-activity relationship of various N-alkyl Gly-boro-Pro derivatives against three dipeptidyl peptidases (DPPs) was studied. In a series of N-cycloalkyl analogs, DPP4 and fibroblast activation protein-alpha (FAP) optimally preferred N-cycloheptyl whereas DPP7 tolerated even larger cycloalkyl rings. Gly alpha-carbon derivatization of N-cyclohexyl or N-(2-adamantyl) Gly-boro-Pro resulted in a significant decrease in potency against all the three DPPs.