In eukaryotic translation initiation, AUG recognition of the mRNA requires accommodation of Met-tRNAi in a ‘PIN’ state, which is antagonized by the factor eIF1. eIF5 is a GTPase activating protein (GAP) of eIF2 that additionally promotes stringent AUG selection, but the molecular basis of its dual function was unknown. We present a cryo-electron microscopy (cryo-EM) reconstruction of a yeast 48S pre-initiation complex (PIC), at an overall resolution of 3.0 Å, featuring the N-terminal domain (NTD) of eIF5 bound to the 40S subunit at the location vacated by eIF1. eIF5 interacts with and allows a more accommodated orientation of Met-tRNAi. Substitutions of eIF5 residues involved in the eIF5-NTD/tRNAi interaction influenced initiation at near-cognate UUG codonsin vivo, and the closed/open PIC conformation in vitro, consistent with direct stabilization of the codon:anticodon duplex by the wild-type eIF5-NTD. The present structure reveals the basis for a key role of eIF5 in start-codon selection.

In eukaryotic translation initiation AUG recognition of the mRNA requires accommodation of Met-tRNA i in a "P IN " state, which is antagonized by the factor eIF1. eIF5 is a GTPase activating protein (GAP) of eIF2 that additionally promotes stringent AUG selection, but the molecular basis of its dual function was unknown. We present a cryo-electron microscopy (cryo-EM) reconstruction of a 48S pre-initiation complex (PIC), at an overall resolution of 3.0 Å, featuring the N-terminal domain (NTD) of eIF5 bound to the 40S subunit at the location vacated by eIF1. eIF5 interacts with and allows a more accommodated orientation of Met-tRNA i . Substitutions of eIF5 residues involved in the eIF5-NTD/tRNA i interaction influenced initiation at near-cognate UUG codons in vivo, and the closed/open PIC conformation in vitro, consistent with direct stabilization of the codon:anticodon duplex by the wild-type eIF5-NTD. The present structure reveals the basis for a key role of eIF5 in start-codon selection. IntroductionEukaryotic translation initiation is a multistep process that involves assembly of a preinitiation complex (PIC) comprised of the small (40S) ribosomal subunit, methionyl initiator tRNA (Met-tRNA i ) and numerous eukaryotic initiation factors (eIFs). The binding of this 43S PIC to the capped 5ʹ end of mRNA is followed by scanning the mRNA leader for the correct AUG start codon. The binding of eIF1 and eIF1A to the 40S subunit promotes a scanningconducive, open conformation favourable for rapid binding of Met-tRNA i as a ternary complex (TC) with eIF2-GTP, in a conformation (P OUT ) suitable for scanning successive triplets in the 40S P site for complementarity to the anticodon of Met-tRNA i . The multisubunit eIF3 complex also binds directly to the 40S subunit and stimulates 43S assembly, attachment to mRNA, and subsequent scanning. During the scanning process, 3 hydrolysis of GTP in TC is stimulated by the GTPase activating protein (GAP) eIF5, but release of phosphate (P i ) from eIF2-GDP-P i is prevented by the gatekeeper molecule eIF1 at non-AUG codons. Recognition of an AUG start codon induces a major conformational change in the PIC to a scanning-arrested closed (P IN ) complex made possible by the dissociation of eIF1, which eliminates a clash it would have with Met-tRNA i in its fully accommodated P IN conformation. The change is accompanied by the movement of the Cterminal tail (CTT) of eIF1A from eIF1 towards the GAP domain of eIF5, an event that eIF1 binds in the open/P IN state. The tRNA i is more fully accommodated in the P site than observed in previous structures containing eIF1, and is also tilted toward the 40S body, apparently setting the stage for its interaction with eIF5B and subsequent joining of the 60S subunit. Extensive interaction with the eIF5-NTD appears to stabilize this tRNA i conformation, using two β-hairpins structurally analogous to those in eIF1 that oppose tRNA i accommodation in the scanning complex. Mutations expected to weaken the observed eIF5-NTD/tRNA i interactions diminish ...

A series of poly(N‐isopropylacrylamide)‐coated mesoporous silica nanoparticle materials (PNiPAm‐MSNs) has been synthesized by a surface‐initiated living radical polymerization with a reversible addition–fragmentation chain transfer (RAFT) reaction. The structure and the degree of polymerization of the PNiPAm‐MSNs has been characterized by a variety of techniques, including nitrogen sorption analysis, 29Si and 13C solid‐state NMR spectroscopy, transmission electron microscopy (TEM), and powder X‐ray diffraction (XRD). The thermally induced changes of the surface properties of these polymer‐coated core–shell nanoparticles have been determined by examining their partition activities in a biphasic solution (water/toluene) at different temperatures.

The surfaces of organically functionalized, MCM-41-type mesoporous silica nanoparticle materials, prepared by a co-condensation method, were studied by solid-state nuclear magnetic resonance (NMR) spectroscopy following a series of heat treatments between 100 and 400 °C. The surfaces were functionalized with 2,2‘-bipyridine, 4-(dimethylamino)pyridine, and pentafluorobenzene. The 13C and 29Si NMR spectra of these materials showed that the structures and concentrations of these functional groups remained unaffected by the heat treatment. Furthermore, it has been demonstrated that the surfactant template, cetyltrimethylammonium bromide (CTAB), could be effectively removed from these materials by heat treatment without disrupting the covalent bonds between the functional groups and the silica surface. The chemical accessibility and reactivity of the organic functionalities were also preserved after heating.

No abstract

Oxidative stress has been a major predicament of present day living. It has been the product of imbalance between the processes involved in free radical generation and their neutralization by enzymatic and non-enzymatic defence mechanisms. The oxidative stress has been contributed by numerous factors including heavy metals, organic compound-rich industrial effluents, air pollutants and changing lifestyle pattern focussing mainly on alcohol consumption, dietary habits, sun exposure, nuclear emissions, etc. The most common outcome of oxidative stress is the increased damage of lipid, DNA and proteins that resulted in the development of different pathologies. Among these pathologies, cancer is the most devastating and linked to multiple mutations arising due to oxidative DNA and protein damage that ultimately affect the integrity of the genome. The chemopreventive agents particularly nutraceuticals are found to be effective in reducing cancer incidences as these components have immense antioxidative, antimutagenic and antiproliferative potentials and are an important part of our dietary components. These secondary metabolites, due to their unique chemical structure, facilitate cell-to-cell communication, repair DNA damage by the downregulation of transcription factors and inhibit the activity of protein kinases and cytochrome P450-dependent mixed function oxidases. These phytochemicals, therefore, are most appropriate in combating oxidative stress-related disorders due to their tendency to exert better protective effect without having any distinct side effect.

BackgroundLiver is the primary metabolizing site of body and is prone to damage by exogenous as well as endogenous intoxicants. Polycyclic aromatic hydrocarbons such as 7, 12- dimethylbenz(α)anthracene (DMBA) is an exogenous hepatotoxin, which is well known for modulating phase I, II and anti-oxidative enzymes of liver. Plants contain plethora of polyphenolic compounds which can reverse the damaging effect of various xenobiotics. The present study investigated protective role of the ethyl acetate fraction of Acacia catechu Willd. (EAF) against DMBA induced alteration in hepatic metabolizing and anti-oxidative enzymes in rats.Methodology and Principal FindingsThe rats were subjected to hepatic damage by treating with DMBA for 7 weeks on alternative days and treatment schedule was terminated at the end of 14 weeks. The rats were euthanized at the end of protocol and livers were homogenized. The liver homogenates were used to analyse phase I (NADPH-cytochrome P450 reducatse, NADH-cytochrome b5 reductase, cytochrome P420, cytochrome b5), phase II (glutathione-S-transferase, DT diaphorase and γ-Glutamyl transpeptidase) and antioxidative enzymes (catalase, superoxide dismutase, ascorbate peroxidase, glutathione reductase, guiacol peroxidase and lactate dehydrogenase). Furthermore, other oxidative stress parameters (thiobarbituric acid reactive substances, lipid hydroperoxides and conjugated dienes and reduced glutathione) and liver marker enzymes (serum glutamic oxaloacetic transaminase, serum glutamic pyruvic transaminase and alkaline phosphatase) were also studied. The DMBA induced significant changes in activity of hepatic enzymes that was reversed by treatment with three dose levels of EAF.ConclusionIt is concluded that EAF affords hepato-protection against DMBA in rats through modulation of phase I, II and anti-oxidative enzymes.

Glucosinolate hydrolytic products are important volatile metabolites that are difficult to extract. The different conditions, such as extraction method, solvent, and dryingmethods, are responsible for successful extractions. An improved extraction method will help in a better isolation of these valuable compounds, which may then be used for different biological activities such as anticancer, antimutagenic, bioherbicidal, antimicrobial, antigenotoxic, and antitumor activities.