Synthesis of imatinib: a convergent approach revisited

Abstract  

A classical convergent approach for the synthesis of the anticancer drug imatinib has been substantially improved. Imatinib was assembled by coupling the amine and carboxylic acid precursors by using N,N′-carbonyldiimidazole (CDI) as a condensing agent. Both intermediates have been synthesized by novel efficient methods.     

Improvement of Drosophila acetylcholinesterase stability by elimination of a free cysteine

Background

Acetylcholinesterase is irreversibly inhibited by organophosphate and carbamate insecticides allowing its use for residue detection with biosensors. Drosophila acetylcholinesterase is the most sensitive enzyme known and has been improved by in vitro mutagenesis. However, it is not sufficiently stable for extensive utilization. It is a homodimer in which both subunits contain 8 cysteine residues. Six are involved in conserved intramolecular disulfide bridges and one is involved in an interchain disulfide bridge. The 8^th cysteine is not conserved and is present at position 290 as a free thiol pointing toward the center of the protein.

Results

The free cysteine has been mutated to valine and the resulting protein has been assayed for stability using various denaturing agents: temperature, urea, acetonitrile, freezing, proteases and spontaneous-denaturation at room temperature. It was found that the C290V mutation rendered the protein 1.1 to 2.7 fold more stable depending on the denaturing agent.

Conclusion

It seems that stabilization resulting from the cysteine to valine mutation originates from a decrease of thiol-disulfide interchanges and from an increase in the hydrophobicity of the buried side chain.     

Physicochemical characterization of the endotoxins from Coxiella burnetii strain Priscilla in relation to their bioactivities

Background  

Coxiella burnetiiis the etiological agent of Q fever found worldwide. The microorganism has like other Gram-negative bacteria a lipopolysaccharide (LPS, endotoxin) in its outer membrane, which is important for the pathogenicity of the bacteria. In order to understand the biological activity of LPS, a detailed physico-chemical analysis of LPS is of utmost importace.     

Study of polyaniline conducting/electroactive polymer as sensor for some agricultural phosphorus pesticides

Abstract  

Due to their wide applications as insecticides, pesticides, chemical warfare agents, etc., detection of organophosphorus compounds is of great importance. This paper deals with application of polyaniline conducting polymer (PANi) as a sensor material for detection of some agricultural organophosphorus compounds that are commonly used as insecticides and pesticides. The compounds employed in this investigation are dichlorvos, trichlorophon, and chlorpyrifos. The effects of some important parameters such as concentration, thickness of the polymer film, etc., on electrical conductivity and conductivity stability for these compounds have also been investigated. In situ electrical conductivity measurements were performed using a standard direct-current (DC) four-point probe technique. It was found that adsorption and desorption of these compounds on PANi film cause measurable change in the resistance of conducting polymers.     

The <Emphasis Type="Italic">FTO</Emphasis> (fat mass and obesity associated) gene codes for a novel member of the non-heme dioxygenase superfamily

Background  

Genetic variants in the FTO (fat mass and obesity associated) gene have been associated with an increased risk of obesity. However, the function of its protein product has not been experimentally studied and previously reported sequence similarity analyses suggested the absence of homologs in existing protein databases. Here, we present the first detailed computational analysis of the sequence and predicted structure of the protein encoded by FTO.     

Substrate specificity analysis of protein kinase complex Dbf2-Mob1 by peptide library and proteome array screening

Background  

The mitotic exit network (MEN) is a group of proteins that form a signaling cascade that is essential for cells to exit mitosis in Saccharomyces cerevisiae. The MEN has also been implicated in playing a role in cytokinesis. Two components of this signaling pathway are the protein kinase Dbf2 and its binding partner essential for its kinase activity, Mob1. The components of MEN that act upstream of Dbf2-Mob1 have been characterized, but physiological substrates for Dbf2-Mob1 have yet to be identified.     

La(OTf)3-catalyzed one-pot synthesis of meso-substituted porphyrinic thiazolidinones

Abstract  

An improved synthetic procedure is developed for the regioselective nitration of a phenyl group of meso-tetraphenylporphyrin by using NaNO₂ in a mixture of trichloroacetic acid and AcOH. The meso-(4-nitrophenyl)porphyrins are successfully reduced to corresponding meso-(4-aminophenyl)porphyrins by SnCl₂ under acidic conditions. In addition, an efficient one-pot methodology for synthesizing a series of novel meso-substituted porphyrinic thiazolidinone conjugates is developed by reacting meso-(4-aminophenyl)porphyrins with various aromatic aldehydes and mercaptoacetic acid in refluxing toluene using La(OTf)₃ as a catalyst. The products obtained are characterized on the basis of their spectral data. Preliminary photophysical properties of the newly synthesized compounds are reported.     

Characterization of rubber particles and rubber chain elongation in <Emphasis Type="Italic">Taraxacum koksaghyz</Emphasis>

Background  

Natural rubber is a biopolymer with exceptional qualities that cannot be completely replaced using synthetic alternatives. Although several key enzymes in the rubber biosynthetic pathway have been isolated, mainly from plants such as Hevea brasiliensis, Ficus spec. and the desert shrub Parthenium argentatum, there have been no in planta functional studies, e.g. by RNA interference, due to the absence of efficient and reproducible protocols for genetic engineering. In contrast, the Russian dandelion Taraxacum koksaghyz, which has long been considered as a potential alternative source of low-cost natural rubber, has a rapid life cycle and can be genetically transformed using a simple and reliable procedure. However, there is very little molecular data available for either the rubber polymer itself or its biosynthesis in T. koksaghyz.     

Synthesis of pyrrolo[1,2-f]phenanthridine-annulated polycyclic heterocycles from palladium-catalyzed intramolecular direct arylation reaction

Abstract  

A concise synthesis of pyrrolo[1,2-f]phenanthridine-annulated polycyclic heterocycles has been achieved in good yields by palladium-catalyzed intramolecular direct arylation reaction.     

Exploring laccase-like multicopper oxidase genes from the ascomycete <Emphasis Type="Italic">Trichoderma reesei</Emphasis>: a functional,phylogenetic and evolutionary study

Background  

The diversity and function of ligninolytic genes in soil-inhabiting ascomycetes has not yet been elucidated, despite their possible role in plant litter decay processes. Among ascomycetes, Trichoderma reesei is a model organism of cellulose and hemicellulose degradation, used for its unique secretion ability especially for cellulase production. T. reesei has only been reported as a cellulolytic and hemicellulolytic organism although genome annotation revealed 6 laccase-like multicopper oxidase (LMCO) genes. The purpose of this work was i) to validate the function of a candidate LMCO gene from T. reesei, and ii) to reconstruct LMCO phylogeny and perform evolutionary analysis testing for positive selection.     

Occurrence and sequence of Sphaeroides Heme Protein and Diheme Cytochrome C in purple photosynthetic bacteria in the family <Emphasis Type="Italic">Rhodobacteraceae</Emphasis>

Background  

Sphaeroides Heme Protein (SHP) was discovered in the purple photosynthetic bacterium, Rhodobacter sphaeroides, and is the only known c-type heme protein that binds oxygen. Although initially not believed to be widespread among the photosynthetic bacteria, the gene has now been found in more than 40 species of proteobacteria and generally appears to be regulated. Rb. sphaeroides is exceptional in not having regulatory genes associated with the operon. We have thus analyzed additional purple bacteria for the SHP gene and examined the genetic context to obtain new insights into the operon, its distribution, and possible function.     

Increasing stability of water-soluble PQQ glucose dehydrogenase by increasing hydrophobic interaction at dimeric interface

Background  

Water-soluble quinoprotein glucose dehydrogenase (PQQGDH-B) from Acinetobacter calcoaceticus has a great potential for application as a glucose sensor constituent. Because this enzyme shows no activity in its monomeric form, correct quaternary structure is essential for the formation of active enzyme. We have previously reported on the increasing of the stability of PQQGDH-B by preventing the subunit dissociation. Previous studies were based on decreasing the entropy of quaternary structure dissociation but not on increasing the interaction between the two subunits. We therefore attempted to introduce a hydrophobic interaction in the dimeric interface to increase the stability of PQQGDH-B.     

Molecular characterization of <Emphasis Type="Italic">tlyA</Emphasis> gene product,Rv1694 of <Emphasis Type="Italic">Mycobacterium tuberculosis</Emphasis>: A non-conventional hemolysin and a ribosomal RNA methyl transferase

Background  

Mycobacterium tuberculosis is a virulent bacillus causing tuberculosis, a disease responsible for million deaths each year worldwide. In order to understand its mechanism of pathogenesis in humans and to help control tuberculosis, functions of numerous Mycobacterium tuberculosis genes are being characterized. In this study we report the dual functionality of tlyA gene product of Mycobacterium tuberculosis annotated as Rv1694, a 268 amino acid long basic protein.     

Characterization of a protease produced by a Trichoderma harzianum isolate which controls cocoa plant witches' broom disease

Background  

Several Trichoderma strains have been reported to be effective in controlling plant diseases, and the action of fungal hydrolytic enzymes has been considered as the main mechanism involved in the antagonistic process. However, although Trichoderma strains were found to impair development of Crinipellis perniciosa, the causal agent of cocoa plant witches' broom disease, no fungal strain is available for effective control of this disease. We have then undertaken a program of construction of hydrolytic enzyme-overproducing Trichoderma strains aiming improvement of the fungal antagonistic capacity. The protease of an indian Trichoderma isolate showing antagonistic activity against C. perniciosa was purified to homogeneity and characterized for its kinetic properties and action on the phytopathogen cell wall.     

An in vitro based investigation of the cytotoxic effect of water extracts of the Chinese herbal remedy LD on cancer cells

Background  

Long Dan Xie Gan Wan (LD), a Chinese herbal remedy formulation, is traditionally used to treat a range of conditions, including gall bladder diseases, hepatitis, hyperthyroidism, migraines but it is not used for the management or treatment of cancer. However some of its herbal constituents, specifically Radix bupleuri, Radix scutellariae and Rhizoma alismatis have been shown to inhibit the growth of cancer cells. Thus, the aim of the study was to investigate the impact of LD on cancer cells in vitro.     

Identification of archaeal proteins that affect the exosome function in vitro

Background  

The archaeal exosome is formed by a hexameric RNase PH ring and three RNA binding subunits and has been shown to bind and degrade RNA in vitro. Despite extensive studies on the eukaryotic exosome and on the proteins interacting with this complex, little information is yet available on the identification and function of archaeal exosome regulatory factors.     

10 α -Hydroxy- β -isomorphine, a by-product of the synthesis of 10 α -hydroxymorphine

Abstract  

A new compound was isolated from the reaction mixture after O-demethylation of 6-O-acetyl-10α-acetoxycodeine with boron tribromide. The structure of this compound, 10α-hydroxy-β-isomorphine, was elucidated by spectral data, and its spatial arrangement was deduced from an NOE experiment. Capillary zone electrophoresis was used for separation of morphine and its 10-hydroxy analogues.     

Na<Superscript>+</Superscript>-stimulated ATPase of alkaliphilic halotolerant cyanobacterium <Emphasis Type="Italic">Aphanothece halophytica</Emphasis> translocates Na<Superscript>+</Superscript> into proteoliposomes via Na<Superscript>+</Superscript> uniport mechanism

Background  

When cells are exposed to high salinity conditions, they develop a mechanism to extrude excess Na⁺ from cells to maintain the cytoplasmic Na⁺ concentration. Until now, the ATPase involved in Na⁺ transport in cyanobacteria has not been characterized. Here, the characterization of ATPase and its role in Na⁺ transport of alkaliphilic halotolerant Aphanothece halophytica were investigated to understand the survival mechanism of A. halophytica under high salinity conditions.     

Absorption tuning of the green fluorescent protein chromophore: synthesis and studies of model compounds

Abstract  

The green fluorescent protein (GFP) chromophore is a heterocyclic compound containing a p-hydroxybenzylidine attached to an imidazol-5(4H)-one ring. This review covers the synthesis of a variety of model systems for elucidating the intrinsic optical properties of the chromophore in the gas phase and its response in particular to hydrogen bond interactions. The overall goal is to understand how the protein binding pocket influences the absorption behavior, and the current status of our ongoing efforts is presented.