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With faithful sample preservation and direct imaging of fully hydrated biological material, cryo-electron tomography provides an accurate representation of molecular architecture of cells. However, detection and precise localization of macromolecular complexes within cellular environments is aggravated by the presence of many molecular species and molecular crowding. We developed a template-free image processing procedure for accurate tracing of complex networks of densities in cryo-electron tomograms, a comprehensive and automated detection of heterogeneous membrane-bound complexes and an unsupervised classification (PySeg). Applications to intact cells and isolated endoplasmic reticulum (ER) allowed us to detect and classify small protein complexes. This classification provided sufficiently homogeneous particle sets and initial references to allow subsequent de novo subtomogram averaging. Spatial distribution analysis showed that ER complexes have different localization patterns forming nanodomains. Therefore, this procedure allows a comprehensive detection and structural analysis of complexes in situ. A template-free image processing approach automatically detects and classifies membrane-bound protein complexes in cryo-electron tomograms of isolated endoplasmic reticulum and in intact cells.

Bimetallic Au–Ag hollow nanoprisms (HNPrs) with variable effective surface areas, dynamic atomic compositions (Au:Ag), and distinct stepped surfaces between the central porous region and crystallin...

Polyvinylpyrrolidone (PVP)-based silver nanoprisms (AgNPrs) show an initial stacking geometry because of their low zeta potential and electrostatic interaction between face-to-face energetically stable {111} surface-bound pyrrolidone groups through the Na+-ion-induced cation−π interaction. Congested interplanar space between AgNPrs allows As(III) to react differentially with silver atoms from facial {111} and peripheral {110} facets to result in smaller stackings and finally nanoseeds. Above this critical concentration of As(III), PVP leached out from nanoparticles to form nanoseed-engulfed emulsions and induced controlled aggregation. This entire morphological transition has been decoded by recording their surface plasmon and surface-enhanced Raman scattering tuning and confirmed by the transmission electron microscopy study. Strong affinity and selectivity of As(III) toward the Ag atom (verified and estimated by the HF/3-21g* level of density functional theory calculation) coupled with low-cost colorime...

Solar light driven photocatalytic technology has attracted much attention because it is a vital step in using solar energy to eliminate undesired chemical substances for environmental conservation and to split water for green hydrogen production. At present the developed quantum efficiency and insufficient stability of the catalytic materials are limiting the process to see the light of commercial success. At this juncture researchers felt that development of new two-dimensional (2D) materials may accelerate the advancement in the fields of solar light utilization. The field of 2D materials has been dominated by graphene due to its many exotic properties. Since 2012, interesting properties of exfoliated MXene and metal chalcogenides are fueling the rapid growth of interest in 2D materials beyond graphene. MXenes are an important family of 2D transition metal carbides, nitrides, and carbonitrides. Recently researchers have been looking into the different modifications of MXene and its use as photocatalyst. For hydrogen evolution reaction MXenes are found to be superior to other 2D catalysts such as MoS2 and g-C3N4. This prospective review will systematically deal with the structural variety, chemical, and physical properties of MXene family in relation to photocatalytic activity. Recent development on material modification and mechanism of enhanced activity toward H2 generation through both photocatalytic and photoelectrocatalytic water splitting involving MXene materials will be analyzed. In addition carbon dioxide reduction to fuel and environmental remediation will be deliberated with respect to both theoretical and experimental results. In conclusion new challenges and possible future directions with MXene-based materials for future technology will be emphasized.

The attraction of Drosophila melanogaster towards byproducts of alcoholic fermentation, especially ethanol, has been extensively studied 1–4. However, the adaptive value of this behavior has not been elucidated. Previous studies have suggested anthropomorphic interpretations of D. melanogaster behavior towards alcohols 5,6. Here, we instead assert that there exists a simple yet vital biological rationale for alcohol contact and consumption by these insects. We show that exposure to alcohols, especially methanol, results in an immediate amplification of fatty acid ester pheromone levels, which in turn elevates the probability that a male will successfully compete for a female during courtship. We proceed to identify three types of olfactory sensory neurons that detect ethanol and methanol. Moreover, we trace the ensuing neural circuits and reveal their role in controlling both attraction and aversion, where valence is balanced around mating status. Based on our results, we deduce that male flies associate with sources of alcohol as a biological imperative related to reproduction, and we provide an assessment of how and why D. melanogaster is associated with alcohol using a sound ecological and natural history approach to this previously enigmatic biological phenomenon.One sentence summaryFlies gain pheromone and courtship advantages with alcohol, but methanol is toxic, thus flies must balance risk versus reward.

The role of the single-domain ferrimagnetic nanostructure and the associated surface for many fold magnetic-field-induced surface enhanced transient spin-trajectory modulation is a new venture in m...

Triplet-triplet (T-T) absorption spectroscopy has been used successfully as a molecular ruler to understand the actual release process of sanguinarine as a drug molecule from a gold nanoparticle surface in the presence of cell components, that is, DNA and chromatin. The obtained results have been verified by fluorescence and surface-enhanced Raman spectroscopy (SERS), and a plausible explanation has been put forward to describe the underestimation and overestimation of the percentage (%) of the release of drug molecules measured by fluorescence- and SERS-based techniques, respectively, over the highlighted T-T absorption spectroscopy. Because of the intrinsic nature of absorption, the reported T-T absorption spectroscopic assay overpowers fluorescence- and SERS-based assays, which are limited by the long-range interaction and nonlinear dependence of the concentration of analytes, respectively.

Human cathepsin K (CTSK) is a collagenolytic lysosomal cysteine protease that plays an important role in bone turnover. Mutation in CTSK gene is associated with loss of collagenolytic activity of CTSK leading to an autosomal recessive bone disorder called pycnodysostosis. Although a number of pycnodysostotic missense mutations have been reported, underlying mechanism of the disease is not clear. In this study, we investigated in vitro six recombinant pycnodysostosis-related mutants of human CTSK (G79E, I249T, G243E, G303E, G319C and Q187P). While all the mutants, like wild-type, show similar high levels of expression in Escherichia coli, four of them (G79E, G303E, G319C and Q187P) are inactive, unstable and spontaneously degrade during purification process. In contrast, proteolytic/collagenolytic activity, zymogen activation kinetics and stability of G243E and I249T mutants are nominally affected. Crystal structure of I249T at 1.92 A resolution shows that the mutation in R-domain causes conformational changes of a surface loop in the L-domain although the catalytic cleft remains unaltered. Molecular simulation, normal mode analysis and fluorescence lifetime measurement eliminated the possibility that the change in L-domain surface loop orientation is a crystallization artefact. CD-based thermal melting profile indicates that stability of I249T is significantly higher than wild-type. Our studies first time reports that pycnodysostosis-related mutations do not always lead to complete loss of general proteolytic activity or specific collagenolytic activity of CTSK. The first crystal structure of a pycnodysostotic mutant (I249T) provides critical information that may pave new avenues towards understanding the disease at molecular level. DATABASE: The atomic co-ordinates and structure factors for I249T mutant of human CTSK (codes 5Z5O) have been deposited in the Protein Data Bank (http://wwpdb.org/).

Decoupling of different plasmon resonance modes (in-plane, and out-of-plane dipole and quadrupole resonances) by tuning nanoparticle’s size and shape offers a new field of plasmonics as colorimetric assay-based optical-ruler for ultra-trace sensing. Driven by its low cost, easy to perform and efficient way to measure trace level (up to 30 ppt in presence of common mining elements in natural gold ore) abundance, this study develops a highly selective and ultrasensitive turn-on colorimetric sensor to detect gold-ion from environmental samples. Different level of gold-ion tracer makes size variable spherical- and disc-shaped silver nanoparticles when added to a ‘growth solution’ which results decoupling of in-plane dipole resonance from in-plane quadrupole and out-of-plane dipole resonances with a wide range of in-plane dipole plasmon tunability to generate different colors. This color-coded sensing of gold-ion shows high selectivity and ultrasensitivity over other metal ions in the ppt level with an impurity aberration limit of 1 ppm. A plausible explanation explains the possible role of catalytic gold-ion to initiate unfavorable silver ion (Ag+) reduction by ascorbic acid to generate silver nanoparticles. Proposed technology has been applied in real mining sample (Bugunda Gold Deposit, Tajikistan) to detect gold concentration from ores to find potential application in mining technology.

Kinetic Monte Carlo simulations for growth on substrates of three-fold symmetry predict the growth of islands of various shapes depending on the growth temperature [Phys. Rev. Lett. 71 (1993) 2967]. On Br–Si(1 1 1) substrates growth of epitaxial gold silicide islands of equilateral triangular and trapezoidal shapes have earlier been observed by annealing at the Au–Si eutectic temperature,363 � C [Phys. Rev. B 51 (1995) 14330]. We carried out annealing with temperature variation within a small window––(363 ± 30) � C. This has led to island growth of additional shapes like regular hexagon,elongated hexagon,walled hexagon and dendrite. Some of the observed island shapes have not been predicted.