Iron carbonyl complexes of Schiff bases and azo compounds

Schiff bases of aromatic aldehyes and ketones react with diiron enneacarbonyl at room temperature giving complexes with the molecular formula (base)Fe2(CO). Azines and hydrazones afford analogous complexes. Schiff bases give low yields of the same complexes when irradiated with iron penta-carbonyl, whereas azines do not react under these conditions. Azobenzene reacts with iron pentocarbonyl when irradiated to give a metal carbonyl complex corresponding to the formula (azobenzone)Fe2(CO)6, which in fact is derivative of ortho-semide; in addition to this type, substituted azobenzenes also give products of the type (azobenzene)2Fe(CO)2. Reaction of azotoluene with diiron enneacarbonyl at room temperature gives yet another type of complex in extremely low yield. The mass spectral and chemical degradation and probable structures of these complexes are discussed. Diphenyldiazomethane reacts with iron pentacarbonyl when irradiated giving two different types of complexes; its reaction with triiron dodecacarbonyl gives predominantly one of these 4.4'-Ditololyldiazomethane affords similar complexes, but phenyldiazomethane and phenylbenzoyldiazomethane give only unstable products in low yields. The most notable feature of this work is that diphenylketene, an irradiation product of phenylbenzoyldiazomethane reacts smoothly with iron penta-carbonyl when irradiated to give complex in fairly high yield. Based on analytical, mass spectral and chemical degradation work, possible structures are proposed for these complexes. Diphenyldiazomethane does not react to give any complexes when irradiated with nickel tetracarbonyl, methylcyclopentadienyl-manganese tricarbonyl and chromium hexacarbonyl. Tetramethyl-2-tetrazene reacts with iron pentacarbonyl when irradiated giving a complex in low yield; its reaction with dirron enneacarbonyl at room temperature gives an unstable liquid complex. Diazofluorine affords two complexes in very low yields, on treatment with diiron enneacarbonyl and different complex when irradiated with iron pentacarbonyl; the latter compound shows both bridging and terminal metal carbonyl absorption in the infrared spectrum. Diazocyclopentadiene gives an unstable liquid complex when irradiated with iron pentacarbonyl. No complexes are formed from ethyl azodicarboxylate and iron pentacarbonyl or diiron enneacarbonyl. In view of the instability and low yields of these complexes, it has not been possible to carry out any chemical work on them. Attempts to form complexes from fluorine, fluorenone or tetraphenylethylene and iron pentacarbonyl by irridation are not successful. Some reactions between the complex obtained from acetylene and the iron tetracarbonyl anion and the following reagents are carried out in order to study the chemistry of this rather interesting compound. Its reaction with dichlorophenylphosphine does not give any phosphole. When irradiated, it yields an unstable complex. In order to see whether it is possible to replace one or more carbonyl groups by diphenylcarbene it is irradiated with diphenyldiazomethane. No such reaction occurs; instead two nitrogen containing complexes are obtained. Its reaction with phenylacetylene gives a metal complex in very low yield. Although the study of these compounds is incomplete some data are presented on them

MR imaging of anterio cruciate ligament injuries

Background: Of all the ligaments of the knee joint the Anterior cruciate ligament (ACL) is the most commonly injured. It is an important pillar of the ligament stabilization of knee joint preventing anterior translation of Tibia over Fibula. Magnetic resonance imaging (MRI) is an excellent modality providing fine-resolution and multiplanar imaging without any radiation, for detection and evaluation of ACL injury with the associated injuries to other ligaments of the knee join. The purpose of the work was to study the role of MRI in classifying the ACL injuries.Methods: MRI Knee of 162 patients with ACL injuries was studied. All the MR imaging scans were performed on 1.5-T MR system (Siemens magnetom Essenza).Results: A total of 162 patients were studied in which majority of them i.e. 43 patients had interstitial sprain, 38 patients had complete tear, 33 patients had mucoid degeneration, 27 had partial tear and 14 had high grade partial tear, however 7 patients had normal ACL. There were associated injuries to the other ligaments of the knee joint along with ACL injury, medial meniscus tear being the most common and was seen in 39.50% followed by lateral meniscus tear in 9.87%, MCL tear in 6.79%, LCL tear in 1.85% and PCL tear in 2.46 %.Conclusions: MRI is a good modality for classifying ACL injury and evaluation of injuries to the associated ligaments

Laser assisted synthesis of carbon nanoparticles with controlled viscosities for printing applications

High-quality carbon nanoparticles with controlled viscosity and high aqueous stability were prepared by liquid-phase laser ablation of a graphite target in deionized water. The size distribution was found to vary from 5 nm to 50 nm with mean size of 18 nm, in the absence of any reducing chemical reagents. Efficient generation of short chain polyynes was recorded for high laser repetition rates. Homogeneous and stable nanoparticle suspensions with viscosities ranging from 0.89 to 12 mPa.s were obtained by suspending the nanoparticles in different solvent mixtures such as glycerol–water and isopropanol–water. Optical properties were investigated by absorption and photoluminescence spectroscopy. Raman spectroscopy confirmed graphitic-like structure of nanoparticles and the surface chemistry was revealed by Fourier-transform infrared spectroscopy demonstrating sufficient electrostatic stabilization to avoid particle coagulation or flocculation. This paper present an exciting alternative method to engineer carbon nanoparticles and their potential use as a ligand-free nano-ink for ink jet printing (jetting) applications

On the Computational Complexity of Vertex Integrity and Component Order Connectivity

The Weighted Vertex Integrity (wVI) problem takes as input an $n$-vertex graph $G$, a weight function $w:V(G)\to\mathbb{N}$, and an integer $p$. The task is to decide if there exists a set $X\subseteq V(G)$ such that the weight of $X$ plus the weight of a heaviest component of $G-X$ is at most $p$. Among other results, we prove that: (1) wVI is NP-complete on co-comparability graphs, even if each vertex has weight $1$; (2) wVI can be solved in $O(p^{p+1}n)$ time; (3) wVI admits a kernel with at most $p^3$ vertices. Result (1) refutes a conjecture by Ray and Deogun and answers an open question by Ray et al. It also complements a result by Kratsch et al., stating that the unweighted version of the problem can be solved in polynomial time on co-comparability graphs of bounded dimension, provided that an intersection model of the input graph is given as part of the input. An instance of the Weighted Component Order Connectivity (wCOC) problem consists of an $n$-vertex graph $G$, a weight function $w:V(G)\to \mathbb{N}$, and two integers $k$ and $l$, and the task is to decide if there exists a set $X\subseteq V(G)$ such that the weight of $X$ is at most $k$ and the weight of a heaviest component of $G-X$ is at most $l$. In some sense, the wCOC problem can be seen as a refined version of the wVI problem. We prove, among other results, that: (4) wCOC can be solved in $O(\min\{k,l\}\cdot n^3)$ time on interval graphs, while the unweighted version can be solved in $O(n^2)$ time on this graph class; (5) wCOC is W[1]-hard on split graphs when parameterized by $k$ or by $l$; (6) wCOC can be solved in $2^{O(k\log l)} n$ time; (7) wCOC admits a kernel with at most $kl(k+l)+k$ vertices. We also show that result (6) is essentially tight by proving that wCOC cannot be solved in $2^{o(k \log l)}n^{O(1)}$ time, unless the ETH fails.Comment: A preliminary version of this paper already appeared in the conference proceedings of ISAAC 201

Sugar alcohol provides imaging contrast in cancer detection

Clinical imaging is widely used to detect, characterize and stage cancers in addition to monitoring the therapeutic progress. Magnetic resonance imaging (MRI) aided by contrast agents utilizes the differential relaxivity property of water to distinguish between tumorous and normal tissue. Here, we describe an MRI contrast method for the detection of cancer using a sugar alcohol, maltitol, a common low caloric sugar substitute that exploits the chemical exchange saturation transfer (CEST) property of the labile hydroxyl group protons on maltitol (malCEST). In vitro studies pointed toward concentration and pH-dependent CEST effect peaking at 1?ppm downfield to the water resonance. Studies with control rats showed that intravenously injected maltitol does not cross the intact blood-brain barrier (BBB). In glioma carrying rats, administration of maltitol resulted in the elevation of CEST contrast in the tumor region only owing to permeable BBB. These preliminary results show that this method may lead to the development of maltitol and other sugar alcohol derivatives as MRI contrast agents for a variety of preclinical imaging applications

Laser synthesis of ligand-free bimetallic nanoparticles for plasmonic applications.

A picosecond laser ablation approach has been developed for the synthesis of ligand-free AuAg bimetallic NPs where the relative amount of Ag is controlled in situ through a laser shielding effect. Various measurements, such as optical spectroscopy, transmission electron microscopy combined with energy dispersive X-ray spectroscopy and inductively coupled plasma optical emission spectrometry, revealed the generation of homogenous 15 nm average size bimetallic NPs with different compositions and tunable localized surface plasmon resonance. Furthermore, ligand-free metallic nanoparticles with respect to chemically synthesized nanoparticles display outstanding properties, i.e. featureless Raman background spectrum, which is a basic requirement in many plasmonic applications such as Surface Enhanced Raman Spectroscopy. Various molecules were chemisorbed on the nanoparticle and SERS investigations were carried out, by varying the laser wavelength. The SERS enhancement factor for AuAg bimetallic NPs shows an enhancement factor of about 5.7 × 105 with respect to the flat AuAg surface

Antioxidant activity assay of stem and in vitro callusing of Tinospora cordifolia (Miers.)

The experiment was conducted to study the antioxidant potential among different hosts of Tinospora cordifolia. The results indicated that the among the different hosts of T. cordifolia, Ficus religiosa had highest phenol content (5.25 mg g-1), inhibition activity (52.05%) and reducing capability as compared to others. F. religiosa showed the highest antioxidant activity of 41.73 μM Fe (II) g-1. EC50 value for lipid peroxidation inhibitory activity was 0.1mg mL-1 for all the samples. EC50 value for DPPH radical scavenging activity was 0.6 mg mL-1 for F. religiosa. This results suggested that the active antioxidant compounds were higher in F. religiosa as compared to Roystonea regia. There was a direct correlation between the total polyphenols extracted and anti-oxidant activity. Among the various explants of F. religiosa, leaf explants were found to be superior for in vitro callus induction. &nbsp

Upregulated sirtuin 1 by miRNA-34a is required for smooth muscle cell differentiation from pluripotent stem cells

© 2015 Macmillan Publishers Limited. All rights reserved. microRNA-34a (miR-34a) and sirtuin 1 (SirT1) have been extensively studied in tumour biology and longevityaging, but little is known about their functional roles in smooth muscle cell (SMC) differentiation from pluripotent stem cells. Using well-established SMC differentiation models, we have demonstrated that miR-34a has an important role in SMC differentiation from murine and human embryonic stem cells. Surprisingly, deacetylase sirtuin 1 (SirT1), one of the top predicted targets, was positively regulated by miR-34a during SMC differentiation. Mechanistically, we demonstrated that miR-34a promoted differentiating stem cells' arrest at G0G1 phase and observed a significantly decreased incorporation of miR-34a and SirT1 RNA into Ago2-RISC complex upon SMC differentiation. Importantly, we have identified SirT1 as a transcriptional activator in the regulation of SMC gene programme. Finally, our data showed that SirT1 modulated the enrichment of H3K9 tri-methylation around the SMC gene-promoter regions. Taken together, our data reveal a specific regulatory pathway that miR-34a positively regulates its target gene SirT1 in a cellular context-dependent and sequence-specific manner and suggest a functional role for this pathway in SMC differentiation from stem cells in vitro and in vivo

Synthesis, Purification and Crystallization of Guanine-rich RNA Oligonucleotides

Guanine-rich RNA oligonucleotides display many novel structural motifs in recent crystal structures. Here we describe the procedures of the chemical synthesis and the purification of such RNA molecules that are suitable for X-ray crystallographic studies. Modifications of the previous purification methods allow us to obtain better yields in shorter time. We also provide 24 screening conditions that are very effective in crystallization of the guanine-rich RNA oligonucleotides. Optimal crystallization conditions are usually achieved by adjustment of the concentration of the metal ions and pH of the buffer. Crystals obtained by this method usually diffract to high resolution

A novel class of microRNA-recognition elements that function only within open reading frames.

MicroRNAs (miRNAs) are well known to target 3' untranslated regions (3' UTRs) in mRNAs, thereby silencing gene expression at the post-transcriptional level. Multiple reports have also indicated the ability of miRNAs to target protein-coding sequences (CDS); however, miRNAs have been generally believed to function through similar mechanisms regardless of the locations of their sites of action. Here, we report a class of miRNA-recognition elements (MREs) that function exclusively in CDS regions. Through functional and mechanistic characterization of these 'unusual' MREs, we demonstrate that CDS-targeted miRNAs require extensive base-pairing at the 3' side rather than the 5' seed; cause gene silencing in an Argonaute-dependent but GW182-independent manner; and repress translation by inducing transient ribosome stalling instead of mRNA destabilization. These findings reveal distinct mechanisms and functional consequences of miRNAs that target CDS versus the 3' UTR and suggest that CDS-targeted miRNAs may use a translational quality-control-related mechanism to regulate translation in mammalian cells