bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stabilization of conformationally dynamic helices by covalently attached acyl chains
Authors: Poschner Bernhard C. , Langosch Dieter 
Published: May 2009

AbstractAcylation of proteins is known to mediate membrane attachment and to influence subcellular sorting. Here, we report that acylation can stabilize secondary structure. Circular dichroism spectroscopy showed that N‐terminal attachment of acyl chains decreases the ability of an intrinsically flexible hydrophobic model peptide to refold from an α‐helical state to β‐sheet in response to changing solvent conditions. Acylation also stabilized the membrane‐embedded α‐helix. This increase of global helix stability did not result from decreased local conformational dynamics of the helix backbone as assessed by deuterium/hydrogen‐exchange experiments. We concluded that acylation can stabilize the structure of intrinsically dynamic helices and may thus prevent misfolding.
A quantitative strategy to detect changes in accessibility of protein regions to chemical modification on heterodimerization
Authors: Dreger Mathias , Leung Bo Wah , Brownlee George G. , Deng Tao 
Published: May 2009

AbstractWe describe a method for studying quantitative changes in accessibility of surface lysine residues of the PB1 subunit of the influenza RNA polymerase as a result of association with the PA subunit to form a PB1‐PA heterodimer. Our method combines two established methods: (i) the chemical modification of surface lysine residues of native proteins by N‐hydroxysuccinimidobiotin (NHS‐biotin) and (ii) the stable isotope labeling of amino acids in cell culture (SILAC) followed by tryptic digestion and mass spectrometry. By linking the chemical modification with the SILAC methodology for the first time, we obtain quantitative data on chemical modification allowing subtle changes in accessibility to be described. Five regions in the PB1 monomer showed altered reactivity to NHS‐biotin when compared with the [PB1‐PA] heterodimer. Mutational analysis of residues in two such regions—at K265 and K481 of PB1, which were about three‐ and twofold, respectively, less accessible to biotinylation in the PB1‐PA heterodimer compared with the PB1 monomer, demonstrated that both K265 and K481 were crucial for polymerase function. This novel assay of quantitative profiling of biotinylation patterns (Q‐POP assay) highlights likely conformational changes at important functional sites, as observed here for PB1, and may provide information on protein–protein interaction interfaces. The Q‐POP assay should be a generally applicable approach and may detect novel functional sites suitable for targeting by drugs.
Water polygons in high‐resolution protein crystal structures
Authors: Lee Jonas , Kim Sung‐Hou 
Published: May 2009

AbstractWe have analyzed the interstitial water (ISW) structures in 1500 protein crystal structures deposited in the Protein Data Bank that have greater than 1.5 Å resolution with less than 90% sequence similarity with each other. We observed varieties of polygonal water structures composed of three to eight water molecules. These polygons may represent the time‐ and space‐averaged structures of “stable” water oligomers present in liquid water, and their presence as well as relative population may be relevant in understanding physical properties of liquid water at a given temperature. On an average, 13% of ISWs are localized enough to be visible by X‐ray diffraction. Of those, averages of 78% are water molecules in the first water layer on the protein surface. Of the localized ISWs beyond the first layer, almost half of them form water polygons such as trigons, tetragons, as well as expected pentagons, hexagons, higher polygons, partial dodecahedrons, and disordered networks. Most of the octagons and nanogons are formed by fusion of smaller polygons. The trigons are most commonly observed. We suggest that our observation provides an experimental basis for including these water polygon structures in correlating and predicting various water properties in liquid state.
Adsorption, desorption and dissipation of metolachlor in surface and subsurface soils
Authors: Si Youbin , Takagi Kazuhiro , Iwasaki Akio , Zhou Dongmei 
Published: May 2009

AbstractBACKGROUND: Variations in soil properties with depth influence retention and degradation of pesticides. Understanding how soil properties within a profile affect pesticide retention and degradation will result in more accurate prediction by simulation models of pesticide fate and potential groundwater contamination. Metolachlor is more persistent than other acetanilide herbicides in the soil environment and has the potential to leach into groundwater. Reasonably, information is needed about the dissipation and eventual fate of metolachlor in subsoils. The objectives were to evaluate the adsorption and desorption characteristics and to determine the dissipation rates of metolachlor in both surface and subsurface soil samples.RESULTS: Adsorption of metolachlor was greater in the high‐organic‐matter surface soil than in subsoils. Lower adsorption distribution coefficient (Kads) values with increasing depth indicated less adsorption at lower depths and greater leaching potential of metolachlor after passage through the surface horizon. Desorption of metolachlor showed hysteresis, indicated by the higher adsorption slope (1/nads) compared with the desorption slope (1/ndes). Soils that adsorbed more metolachlor also desorbed less metolachlor. Metolachlor dissipation rates generally decreased with increasing soil depth. The first‐order dissipation rate was highest at the 0–50 cm depth (0.140 week−1) and lowest at the 350–425 cm depth (0.005 week−1). Degradation of the herbicide was significantly correlated with microbial activity in soils.CONCLUSION: Metolachlor that has escaped degradation or binding to organic matter at the soil surface might leach into the subsurface soil where it will dissipate slowly and be subject to transport to groundwater. Copyright © 2009 Society of Chemical Industry
Inhibition of enteropathogenic Escherichia coli adhesion on host epithelial cells by Holarrhena antidysenterica (L.) WALL.
Authors: Kavitha D. , Niranjali S. 
Published: May 2009

AbstractBacterial adhesion is the first step in the sequence of events leading to infection. Previous data are available on the effect of Holarrhena antidysenterica on antidiarrhoeal and antibacterial action, but there is little information on the mechanism of action of the various aspects of EPEC‐induced diarrhoea, namely adherence and translocation of the effector molecule to intestinal epithelial cells. The aim of the present study was to investigate the effects of alkaloids of Holarrhena antidysenterica (AHA) on interference in the mechanism of enteropathogenic Escherichia coli (EPEC) adhesion on host epithelial cells (INT 407 and HEp2). To determine the impact of AHA on epithelial cells, cytotoxicity (LDH), adherence, apoptotic and ultrastructural studies were performed. To analyse the effect of AHA on EPEC secreted proteins, especially EspD, INT 407 monolayers were infected with EPEC and AHA‐treated EPEC, followed by immunoblotting, probed with anti EspD antisera. The maximum percentage of LDH leakage was reduced in AHA‐treated EPEC (400 µg/mL) in both cell lines. Reduced bacterial adherence was observed under light microscopy and altered apoptotic changes were visualized using propidium iodide staining in conjunction with fluorescence microscopy, in both cell lines infected with AHA‐treated EPEC and these results were confirmed with transmission electron microscope images. The suppression of type III secretory proteins (TTSPs), EspD (∼40 kDa), was detected in INT 407 cells infected with AHA‐treated EPEC. In conclusion, AHA reduces initial bacterial adhesion to intact epithelial cells and it may exert an antiadherence effect against the pathogenesis of EPEC in host epithelial cells. Thus, the investigations provide a rational basis for the treatment of EPEC‐mediated diarrhoea with AHA. Copyright © 2009 John Wiley & Sons, Ltd.
Atractylodes japonica root extract protects osteoblastic MC3T3‐E1 cells against hydrogen peroxide‐induced inhibition of osteoblastic differentiation
Authors: Choi Eun Mi , Kim Gun‐Hee , Lee Yong Soo 
Published: May 2009

AbstractThe rhizome of Atractylodes japonica Koidz. has been used traditionally for the treatment of water retention in the body and is known to have estrogen‐like activity. In the present study, the protective effects of A. japonica root extract on the response of osteoblasts to oxidative stress were evaluated. Osteoblastic MC3T3‐E1 cells were incubated with hydrogen peroxide and/or A. japonica root extract, and markers of osteoblast function and oxidative damage were examined. A. japonica root extract significantly (p < 0.05) increased cell survival, alkaline phosphatase activity, collagen and calcium deposition and decreased the production of receptor activator of nuclear factor‐kB ligand (RANKL), protein carbonyl and malondialdehyde of osteoblastic MC3T3‐E1 cells in the presence of hydrogen peroxide. These results demonstrate that A. japonica root can protect the cells from oxidative stress‐induced toxicity and may have positive effects on skeletal structure. Copyright © 2009 John Wiley & Sons, Ltd.
Bioactive acylphloroglucinols from Hypericum densiflorum
Authors: Henry Geneive E. , Campbell Matthew S. , Zelinsky Ashlee A. , Liu Yunbao , Bowen‐Forbes Camile S. , Li Liya , Nair Muraleedharan G. , Rowley David C. , Seeram Navindra P. 
Published: May 2009

AbstractThree acylphloroglucinol derivatives have been isolated from the hexane and acetone extracts of the aerial parts of Hypericum densiflorum Pursch. The compounds were characterized by NMR spectroscopy and mass spectrometry and identified as 4‐geranyloxy‐2,6‐dihydroxybenzophenone (1), 4‐geranyloxy‐1‐(2‐methylpropanoyl)‐ phloroglucinol (2) and 4‐geranyloxy‐1‐(2‐methylbutanoyl)‐phloroglucinol (3). Compounds 1–3 were evaluated for in vitro cell proliferation inhibitory activity against human breast (MCF‐7), lung (NCI H460), CNS (SF‐268), stomach (AGS) and colon (HCT‐116) tumor cell lines; antibacterial activity against methicillin‐resistant Staphylococcus aureus (MRSA); inhibition of cyclooxygenase (COX‐1 and ‐2) enzymes; and antioxidant activity in the lipid peroxidation (LPO) assay. All three compounds showed moderate to strong antitumor, antibacterial, antioxidant and inhibition of COX‐2 activities. Also, this is the first reported occurrence of compound 3 in the Hypericum genus. Copyright © 2009 John Wiley & Sons, Ltd.
Interactions of Valeriana officinalis L. and Passiflora incarnata L. in a patient treated with lorazepam
Authors: Carrasco María Consuelo , Vallejo José Ramón , Pardo‐de‐Santayana Manuel , Peral Diego , Martín Miguel Ángel , Altimiras Jacinto 
Published: May 2009

AbstractThere is an increasing interest in the health risks related to the use of herbal remedies. Although most consumers think that phytomedicines are safe and without side effects, interactions between complementary alternative and conventional medicines are being described. The aim of this clinical case report is to highlight the importance of the safe use of herbal remedies by providing a clinical interaction study between pharmaceutical medicines and herbal medicinal products. The case of a patient self‐medicated with Valeriana officinalis L. and Passiflora incarnata L. while he was on lorazepam treatment is described. Handshaking, dizziness, throbbing and muscular fatigue were reported within the 32 h before clinical diagnosis. The analysis of family medical history ruled out essential tremor, Parkinson's disease, Wilson's disease and other symptom‐related pathologies. His medical history revealed a generalized anxiety disorder and medicinal plant consumption but no neurological disorder. Appropriate physical examination was carried out. An additive or synergistic effect is suspected to have produced these symptoms. The active principles of Valerian and passionflower might increase the inhibitory activity of benzodiazepines binding to the GABA receptors, causing severe secondary effects. Due to the increase in herbal product self‐medication, the use of herbal remedies should be registered while taking the personal clinical history. Multidisciplinary teams should be created to raise studies on medicinal plants with impact on medical praxis. Copyright © 2009 John Wiley & Sons, Ltd.
Drug interaction potential of the seed extract ofUrtica urensL. (dwarf Nettle)
Authors: Agus Hizlan H. , Tekin Pelin , Bayav Merve , Semiz Asli , Sen Alaattin 
Published: May 2009

AbstractDwarf nettle (Urtica urens) seed extract was examinedin vivoin the rat for its potential to modulate drug metabolizing enzymes including aminopyrineN‐demethylase (APND; CYP2C6), aniline 4‐hydroxylase (A4H; CYP2E1), nitrosodimethylamineN‐demethylase (NDMA‐ND; CYP2E1) erythromycinN‐demethylase (ERND; CYP3A1) CYP2D1/2 and glutathioneS‐transferase (GST). RT‐PCR data and western blotting studies clearly demonstrated that CYP2C6 and CYP2E1 mRNA levels were substantially increased after Urtica treatment, while the level of CYP3A1 mRNA decreased and that of CYP2D1/2 remained unchanged. Urtica treatment significantly induced GST activity in the liver, lung and kidney (66‐, 46‐ and 31‐fold, respectively) while decreasing that of APND (35‐, 61‐ and 94‐fold) and NDMA‐ND (23, 28 and 54‐fold). ERND activity in liver was reduced 45‐fold, but increased in the lung and kidney (78‐ and 144‐fold) after Urtica treatment. These results indicate that Urtica seed extract may have the potential to inhibit and/or induce the metabolism of certain co‐administered drugs. Copyright © 2009 John Wiley & Sons, Ltd.
Protective effect of resveratrol on markers of oxidative stress in human erythrocytes subjected to in vitro oxidative insult
Authors: Pandey Kanti Bhooshan , Rizvi Syed Ibrahim 
Published: May 2009

AbstractResveratrol is a natural polyphenolic compound found largely in the skin of red grapes. Growing evidence suggests that resveratrol may play an important role in the prevention of many human diseases. Many of the biological actions of this polyphenol have been attributed to its antioxidant properties. The present study was undertaken to evaluate the effect of resveratrol on intracellular reduced glutathione (GSH) and membrane sulphydryl groups in erythrocytes subjected to oxidative stress in vitro by incubating with t‐BHP (10 µm). The study was aimed to test the efficacy of the antioxidant effect of resveratrol on human erythrocytes. Subjecting erythrocytes to oxidative stress (in vitro) by incubating them with t‐BHP (10 µm) caused a significant decrease in the intracellular GSH level and membrane –SH content compared with basal values. Incubation of erythrocytes/membranes with resveratrol (1–100 µm final conc) resulted in significant protection against the t‐BHP‐induced oxidative stress as evidenced by the increase in GSH level and membrane –SH content. It was observed that the effect of resveratrol is dose/concentration and time‐dependent. Since resveratrol is naturally present in many fruits and vegetables, a diet rich in resveratrol may provide protection against degenerative diseases. Copyright © 2009 John Wiley & Sons, Ltd.
Toxicity studies on dermal application of plant extract of Dodonaea viscosa used in Ethiopian traditional medicine
Authors: Teshome Kefale , Gebre‐Mariam Tsige , Asres Kaleab , Engidawork Ephrem 
Published: May 2009

AbstractDespite advances in the understanding of the medicinal properties of many herbs, the consumer today is confronted with the lack of or misinformation concerning the safety of these herbs that rivals the heyday of the patent medicine era. In the present study, Dodonaea viscosa (Sapindaceae), a medicinal plant commonly used for skin diseases in Ethiopia was subjected to a systematic dermatotoxicity study. To this effect, the dermatotoxicity of an 80% methanol extract of the leaf was investigated in animals following standard procedures for irritation, sensitization, acute toxicity and repeated toxicity tests.The skin irritation test in rabbits showed the extract to be a slight or negligibly slight irritant, with a primary irritation index of 0.45. A sensitization test in mice by the mouse ear swelling test method revealed the extract to be a non‐sensitizer in the dose range 12–30 mg/mL. The percent responder was zero. The acute and repeated dermal toxicity tests on rats did not show any overt sign of toxicity. The findings of this study collectively indicate that dermal application of D. viscosa is not associated with any toxicologically relevant effects and the data could provide satisfactory preclinical evidence of safety to launch a clinical trial on a standardized formulation of the plant extracts. Copyright © 2009 John Wiley & Sons, Ltd.
Tyrosinase inhibitory constituents from the stems of Maackia fauriei
Authors: Kim Jeong Mi , Ko Ryeo Kyeong , Jung Duk Sang , Kim Sang Suk , Lee Nam Ho 
Published: May 2009

AbstractBioassay‐guided investigation of the stems of Maackia fauriei led to the isolation of seven flavonoid constituents, formononetin (1), genistein (2), daidzein (3), texasin (4), tectorigenin (5), odoratin (6) and mirkoin (7). Their structures were elucidated on the basis of spectral studies as well as by comparison with literature data. Tyrosinase inhibition activities were carried out on the isolated compounds. Among these, mirkoin (7) was identified as a potent tyrosinase inhibitor. It inhibited mushroom tyrosinase with an IC50 value of 0.005 mm, which is ten times more active than kojic acid (IC50 = 0.045 mm). The inhibition kinetics, analysed by Lineweaver‐Burk plots, indicated mirkoin (7) to be a competitive inhibitor of tyrosinase when l‐tyrosinase was used as a substrate. The results suggest that hydroxyl groups at C‐4′ in the B ring of flavonoids play an important role in the tyrosinase inhibition activities. Interestingly, compounds 4–7 were isolated for the first time from this plant. Copyright © 2009 John Wiley & Sons, Ltd.
Hyphenation of centrifugal partition chromatography with electrospray ionization mass spectrometry using an active flow‐splitter device for characterization of flavonol glycosides
Authors: Toribio Alix , Destandau Emilie , Elfakir Claire , Lafosse Michel 
Published: May 2009

AbstractOnline coupling of centrifugal partition chromatography to electrospray ionization mass spectrometry (CPC/ESI‐MS) was investigated for the separation and characterization of flavonol glycosides. Structural identification and purification monitoring of analytes on milligram scale were demonstrated to be possible by using an active flow‐splitter device which transfers automatically and successively, at discrete frequencies, small aliquots of the chromatographic effluent to an independent auxiliary stream directed to an ESI quadrupole mass spectrometer. The CPC protocol used a biphasic solvent system composed of ethyl acetate/ethanol/water (4.5:1:4.5, v/v/v) in isocratic mode. During the separation process, continuous acquisition of mass spectral data of the isolated flavonols from the effluent was performed in the negative ion mode with an auxiliary stream composed of 50 mM ammonium acetate/ethanol (2:8, v/v) delivered by a secondary pump. To demonstrate the potential of this hyphenated technique, flavonol glycosides from an apple peel extract were identified, purified and quantitatively analyzed. Calibration curves and limits of detection are also detailed. Copyright © 2009 John Wiley & Sons, Ltd.
A method for 13C‐labeling of metabolic carbohydrates within French bean leaves (Phaseolus vulgaris L.) for decomposition studies in soils
Authors: Girardin Cyril , Rasse Daniel P. , Biron Philippe , Ghashghaie Jaleh , Chenu Claire 
Published: May 2009

AbstractThe molecular composition of plant residues is suspected to largely govern the fate of their constitutive carbon (C) in soils. Labile compounds, such as metabolic carbohydrates, are affected differently from recalcitrant and structural compounds by soil‐C stabilisation mechanisms. Producing 13C‐enriched plant residues with specifically labeled fractions would help us to investigate the fate in soils of the constitutive C of these compounds. The objective of the present research was to test 13C pulse chase labeling as a method for specifically enriching the metabolic carbohydrate components of plant residues, i.e. soluble sugars and starch. Bean plants were exposed to a 13CO2‐enriched atmosphere for 0.5, 1, 2, 3 and 21 h. The major soluble sugars were then determined on water‐soluble extracts, and starch on HCl‐hydrolysable extracts. The results show a quick differential labeling between water‐soluble and water‐insoluble compounds. For both groups, 13C‐labeling increased linearly with time. The difference in δ13C signature between water‐soluble and insoluble fractions was 7‰ after 0.5 h and 70‰ after 21 h. However, this clear isotopic contrast masked a substantial labeling variability within each fraction. By contrast, metabolic carbohydrates on the one hand (i.e. soluble sugars + starch) and other fractions (essentially cell wall components) on the other hand displayed quite homogeneous signatures within fractions, and a significant difference in labeling between fractions: δ13C = 414 ± 3.7‰ and 56 ± 5.5‰, respectively. Thus, the technique generates labeled plant residues displaying contrasting 13C‐isotopic signatures between metabolic carbohydrates and other compounds, with homogenous signatures within each group. Metabolic carbohydrates being labile compounds, our findings suggest that the technique is particularly appropriate for investigating the effect of compound lability on the long‐term storage of their constitutive C in soils. Copyright © 2009 John Wiley & Sons, Ltd.
Determination of sub‐ppb epichlorohydrin levels in water by on‐line solid‐phase extraction liquid chromatography/tandem mass spectrometry
Authors: Ripollés Cristina , Marín José M. , López Francisco J. , Sancho Juan V. , Hernández Félix 
Published: May 2009

AbstractA new sensitive and selective method based on on‐line solid‐phase extraction (SPE) coupled to liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI‐MS/MS) using a triple quadrupole mass spectrometer has been developed for the determination of epichlorohydrin (ECH) in different types of water samples. ECH is not easily determined directly by ESI‐MS as it is not readily ionized, and it has a low molecular mass and high polarity. Thus, prior derivatization of ECH was necessary, employing 3,5‐difluorobenzylamine as a derivatizing agent with Fe(III) as a catalyst. In order to achieve accurate quantification, correcting for matrix effects, losses in the derivatization process and instrumental deviations, isotope labelled ECH (ECH‐d5) was added as an internal standard (IS) to the water samples. The method was validated based on European SANCO guidelines using drinking and other types of treated water spiked at two concentration levels (0.1 and 1.0 µg/L), the lower level having been established as the limit of quantification (LOQ) of the method. Satisfactory accuracy (recoveries between 70 and 103%), precision (RSD <20%) and linearity (from 0.05 to 50 µg/L, r >0.99) were obtained. The limit of detection (LOD) was set up at 0.03 µg/L. The method was applied to different water samples (drinking water and water samples collected from a municipal treatment water plant). In order to enhance confidence, five selected reaction monitoring (SRM) transitions were acquired, thus obtaining a simultaneous reliable quantification and identification of ECH in water, even at sub‐ppb levels. Copyright © 2009 John Wiley & Sons, Ltd.