bluuebunny/crossref_metadata_2025_split huggingface dataset:
Defining resonance Raman spectral responses to substrate binding by cytochrome P450 from Pseudomonas putida
Authors: Mak Piotr J. , Kaluka Daniel , Manyumwa Munyaradzi Edith , Zhang Haiqing , Deng Tianjing , Kincaid James R. 
Published: July 2008

AbstractResonance Raman spectra are reported for substrate‐free and camphor‐bound cytochrome P450cam and its isotopically labeled analogues that have been reconstituted with protoheme derivatives that bear ‐CD3 groups at the 1, 3, 5, and 8‐positions (d12‐protoheme) or deuterated methine carbons (d4‐protoheme). In agreement with previous studies of this and similar enzymes, substrate binding induces changes in the high frequency and low frequency spectral regions, with the most dramatic effect in the low frequency region being activation of a new mode near 367 cm−1. This substrate‐activated mode had been previously assigned as a second “propionate bending” mode (Chen et al., Biochemistry, 2004, 43, 1798–1808), arising in addition to the single propionate bending mode observed for the substrate‐free form at 380 cm−1. In this work, this newly activated mode is observed to shift by 8 cm−1 to lower frequency in the d12‐protoheme reconstituted enzyme (i.e., the same shift as that observed for the higher frequency “propionate bending” mode) and is therefore consistent with the suggested assignment. However, the newly acquired data for the d4‐protoheme substituted analogue also support an earlier alternate suggestion (Deng et al., Biochemistry, 1999, 38, 13699–13706) that substrate binding activates several heme out‐of‐plane modes, one of which (γ6) is accidentally degenerate with the 367 cm−1 propionate bending mode. Finally, the study of the enzyme reconstituted with the protoheme‐d4, which shifts the macrocycle ν10 mode, has now allowed a definitive identification of the vinyl CC stretching modes. © 2008 Wiley Periodicals, Inc. Biopolymers 89: 1045–1053, 2008.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Relating Chemical and Biological Diversity Space: A Tunable System for Efficient Gene Transfection
Authors: Van Vliet Liisa D. , Chapman Michael R. , Avenier Frédéric , Kitson Chris Z. , Hollfelder Florian 
Published: July 2008

AbstractPolyethyleneimine (PEI), a well‐established nonviral transfection reagent, was combinatorially modified with varying proportions of methyl, benzyl, and n‐dodecyl groups to create a library of 435 derivatized polymers. Screening of this library for transfection, DNA binding, and toxicity allows systematic correlation of the biological properties of our polymers to their derivatizations. Combinations of derivatizations bring about a 100‐fold variation in transfection efficiency between library members. The best PEI derivatives exhibit increases in transfection efficiency of more than 80‐fold over unmodified PEI (up to 28±7 % of cells transfected) and rival commercial reagents such as Lipofectamine 2000 (21±10 %) and JetPEI (32±5.0 %). In addition, we can identify compounds that are specifically tuned for efficient transfection in CHO‐K1 over Ishikawa cells and vice versa, demonstrating that the approach can lead to cell‐type selectivity of at least one order of magnitude. This work demonstrates that multivalent derivatization of a polymeric framework can create functional diversity substantially greater than the structural diversity of the derivatization building blocks and suggests an approach to a better understanding of the molecular underpinnings of transfection as well as their exploitation.
Synthesis of Novel DC‐SIGN Ligands with an α‐Fucosylamide Anchor
Authors: Timpano Gabriele , Tabarani Georges , Anderluh Marko , Invernizzi Donatella , Vasile Francesca , Potenza Donatella , Nieto Pedro M. , Rojo Javier , Fieschi Franck , Bernardi Anna 
Published: July 2008

AbstractThe dendritic cell‐specific intercellular adhesion molecule (ICAM) 3‐grabbing nonintegrin (DC‐SIGN) is a C‐type lectin that appears to perform several different functions. Besides mediating adhesion between dendritic cells and T lymphocytes, DC‐SIGN recognizes several pathogens some of which, including HIV, appear to exploit it to invade host organisms. The intriguing diversity of the roles attributed to DC‐SIGN and their therapeutic implications have stimulated the search for new ligands that could be used as biological probes and possibly as lead compounds for drug development. The natural ligands of DC‐SIGN consist of mannose oligosaccharides or fucose‐containing Lewis‐type determinants. Using the known 3D structure of the Lewis‐x trisaccharide, we have identified some monovalent α‐fucosylamides that bind to DC‐SIGN with inhibitory constants 0.4–0.5 mM, as determined by SPR, and have characterized their interaction with the protein by STD NMR spectroscopy. This work establishes for the first time α‐fucosylamides as functional mimics of chemically and enzymatically unstable α‐fucosides and describes interesting candidates for the preparation of multivalent systems able to block the receptor DC‐SIGN with high affinity and with potential biomedical applications.
Chemistry in Confining Reaction Fields with Special Emphasis on Nanoporous Materials
Authors: Polarz Sebastian , Kuschel Andreas 
Published: July 2008

AbstractThe everyday routine of most chemists is dictated by large numbers. The chemical rules for ensembles of molar size (N≈NA=6.022×1023) are well known and can be understood in most cases by using Boltzmann distribution. It is an interesting question how a small ensemble of a chemical system behaves and if it differs from the respective large‐ensemble counterpart. The experimental approach presented in the current paper involves the division of a macroscopic volume into compartments that contain only a small number of reactants. The compartments represent the pores of tailor‐made nanoporous materials.
Increasing chiral recognition in acetal formation
Authors: Noe Christian R. , Knollmüller Max , Jangg Edith , Gmeiner Günter P. , Urban Ernst , Eppacher Simon 
Published: July 2008

AbstractThe design of substituted lactols is described, which in their reaction with racemic alkyl aryl carbinols react preferentially with one of the enantiomers exhibiting selectivities up to 14:1. Chirality, 2009. © 2008 Wiley‐Liss, Inc.
The posssible role of enantiodiscrimination in bilirubin toxicity
Authors: Bernardini Carlotta , D'Arrigo Paola , Elemento Gioia , Mancini Giovanna , Servi Stefano , Sorrenti Alessandro 
Published: July 2008

AbstractThe possibility that enantiodiscrimination of bilirubin might be involved in neuronal membrane destabilization, and therefore in bilirubin toxicity, was investigated, by circular dichroism, on model membranes composed of phospholipids. The equilibrium between bilirubin enantiomers is displaced at some extent by the interaction with certain phospholipids. The extent of equilibrium displacement depends on the molecular structure of phospholipids and on the state of charge of bilirubin. The results obtained validate the hypothesis of a possible involvement of chirality in bilirubin toxicity and support a previously suggested model for the molecular mechanism of the interaction of bilirubin with the synaptic membrane. Chirality, 2009. © 2008 Wiley‐Liss, Inc.
Interactions of Λ and Δ enantiomers of ruthenium(II) cationic complexes with achiral anionic porphyrins
Authors: Randazzo Rosalba , Lauceri Rosaria , Mammana Angela , D'Urso Alessandro , Purrello Roberto 
Published: July 2008

AbstractThe interactions between Λ and Δ enantiomers of ruthenium(II)‐phenanthroline cationic complex ([Ru(phen)3]2+) and three anionic porphyrins have been characterized by absorption, circular dichroism (CD), fluorescence, and resonance light scattering (RLS). The three porphyrins used in this study have been chosen for the different number (two or four) and reciprocal (symmetrical, cis or trans) disposition of the anionic (4‐sulphonatophenyl) peripheral groups in the meso positions. All the techniques evidence the formation of inorganic–organic hybrids. In particular, CD and fluorescence measurements show that the inorganic moiety is able to transfer to porphyrins not only chirality (as shown from the appearance of an induced CD signal (ICD) in the absorption region of porphyrins) but, most likely, also energy. Chirality, 2009. © 2008 Wiley‐Liss, Inc.
Dynamic HPLC of stereolabile iron(II) complexes on chiral stationary phases
Authors: Villani Claudio , Gasparrini Francesco , Pierini Marco , Mortera Stefano Levi , D'Acquarica Ilaria , Ciogli Alessia , Zappia Giovanni 
Published: July 2008

AbstractA series of chiral tris‐(1,10)‐phenanthroline iron(II) complexes have been resolved by HPLC on chiral stationary phases based on either cellulose tris‐(3,5‐dimethylphenylcarbamate) or teicoplanin. At sub ambient temperatures, baseline separation of the enantiomers was observed for five different iron(II) complexes featuring substituted phenanthroline ligands. Dynamic HPLC profiles were observed near or above room temperature, indicating on‐column Δ/Λ enantiomerization. Rate constants for the Δ/Λ interconversion in free solution and during chromatography were obtained by thermal racemization experiments and by computer simulation of the HPLC dynamic plots, respectively. Chirality, 2009. © 2008 Wiley‐Liss, Inc.
Supramolecular enantiodifferentiating photoisomerization of (Z)‐cyclooctene in lyotropic and thermotropic liquid crystals
Authors: Xiao Debao , Wada Takehiko , Inoue Yoshihisa 
Published: July 2008

AbstractIn order to understand the roles of moderately organized media and the factors controlling the chirality transfer in supramolecular photochirogenesis, enantiodifferentiating photoisomerization of (Z)‐cyclooctene to the chiral (E)‐isomer (1E) has been performed for the first time in liquid crystal (LC) systems such as lyotropic LCs of poly(γ‐benzyl‐L‐glutamate) (PBLG), difluorobenzene derivatives mixture, and thermotropic cholesteryl oleyl carbonate LCs. Basically, the as‐employed LCs provided small enantiomer excess (<5%). It is interesting that lyotropic PBLG LCs give contrasting results in cholesteric and nematic mesophases, revealing the importance of the relevant mesophase structure of LC. Selective excitation in achiral difluorobenzene LC doped with a chiral sensitizer facilitates us to conclude that the LC's chiral spatial arrangement is not sufficient or suitable to induce appreciable enantiomeric excess (ee) in the product, but the existence of molecular chirality (of a chiral sensitizer) is essential to afford an optically active (nonracemic) product at least in the present photosensitization system. The photosensitizations in thermotropic LCs further reveal that the product's ee can be manipulated by the LC mesophase not directly but through the sensitizer's conformational changes induced by the supramolecular interactions with the surrounding LC structure. Chirality, 2009. © 2008 Wiley‐Liss, Inc.
Alteration of kynurenic acid concentration in rat plasma following optically pure kynurenine administration: A comparative study between enantiomers
Authors: Fukushima Takeshi , Sone Yukiko , Mitsuhashi Shogo , Tomiya Masayuki , Toyo'oka Toshimasa 
Published: July 2008

AbstractL‐Kynurenine (KYN), a tryptophan metabolite, is metabolized to kynurenic acid (KYNA), which is an antagonist of N‐methyl‐D‐aspartate and α7 nicotinic acetylcholine receptors, by kynurenine aminotransferase (KAT) I and KAT II. In this study, optically pure KYN, namely L‐KYN or D‐KYN, was administered intraperitoneally to male Sprague‐Dawley rats (16.3 μmol kg−1), and the change in plasma KYNA was investigated by using column‐switching high‐performance liquid chromatography (HPLC) with fluorescence detection. Unexpectedly, no remarkable alteration in the plasma KYNA was observed when a natural isomer, L‐KYN, was administered, whereas plasma KYNA concentration was unequivocally increased when an unnatural isomer, D‐KYN, was administered. Serum protein bindings of L‐KYN and D‐KYN were also studied, and the protein binding of L‐KYN (∼65%) in rat serum was larger than that of D‐KYN (∼12%), suggesting that D‐KYN may be easily incorporated and metabolized in tissues during blood circulation to generate KYNA in mammals. In addition, the increase in plasma KYNA by the administration of D‐KYN was suppressed in rats pretreated with a selective inhibitor of D‐amino acid oxidase (DAAO), 5‐methylpyrazole‐3‐carboxylic acid (80 mg/kg). These results suggest that DAAO might be responsible for the production of KYNA from D‐KYN in vivo. Chirality, 2009. © 2008 Wiley‐Liss, Inc.
Configuration of the vitamin E analogue garcinoic acid extracted from garcinia kola seeds
Authors: Mazzini Francesco , Betti Michele , Netscher Thomas , Galli Francesco , Salvadori Piero 
Published: July 2008

AbstractVitamin E derivatives bearing a carboxylic group have recently gained great attention because of their antitumoral properties. Garcinoic acid (trans‐13′‐carboxy‐δ‐tocotrienol) is a vitamin E analog extracted from Garcinia Kola seeds in which the carboxylic group is at the end of the aliphatic side chain and reported to be a racemate based on the optical rotation measurements. However, CD determination of a sample of the acid analyzed by us gave a positive peak at 208 nm, indicating that it is not a racemate. To assess the enantiomeric composition of garcinoic acid, it was thus transformed to α‐tocopherol and analyzed by chiral HPLC on column OD‐H. On the basis of the elution order of α‐tocopherol stereoisomers, the garcinoic acid sample resulted to be enantiopure with R configuration at carbon 2 of the chroman ring. Moreover, in a preliminary test, the acid and some of its derivatives showed a marked antiproliferative effect on glioma C6 cancer cells. Chirality, 2009. © 2008 Wiley‐Liss, Inc.
Stereoselective analysis of tiopronin enantiomers in rat plasma using high‐performance liquid chromatography‐electrospray ionization mass spectrometry after chiral derivatization
Authors: Wang Huan , Ma Chen , Zhou Jia , Liu Xiao Quan 
Published: July 2008

AbstractA specific and relatively sensitive high‐performance liquid chromatography‐electrospray ionization mass spectrometry (HPLC‐ESI‐MS) was developed for the quantitative analysis of tiopronin enantiomers in rat plasma. The method is based on the derivatization of (+)‐tiopronin and (−)‐tiopronin with 2,3,4,6‐tetra‐O‐acetyl‐β‐glucopyranosyl isothiocyanate (GITC) in acetonitrile. The separation of resulting diastereomic derivatives was performed on C18 column (150 mm × 2.0 mm ID, packed with 5.0 μm C18 silica RP particle), using a mobile phase of methanol/water (containing 5.3 mM formic acid) with gradient elution. LC–MS was performed in the selected ion monitoring and positive ion mode using target ions at m/z: 575 for the diastereomic derivatives of tiopronin and m/z: 603 for the derivative of N‐isobutyryl‐D‐cysteine (internal standard). The method was validated in terms of specificity, linearity, sensitivity, precision, accuracy, matrix effect, and stability. The calibration curves were linear over the concentration range of 0.025–5 μg/ml for both enantiomers of tiopronin. For both enantiomers of tiopronin, the interbatch and intrabatch variability values were less than 15%, and the accuracy was within ±17% in terms of relative error. The method was successfully applied to a pharmacokinetic study of rac‐tiopronin in rat. Chirality, 2009. © 2008 Wiley‐Liss, Inc.
Stereoselective synthesis of 2,3,7‐trimethylcyclooctanone and related compounds and determination of their relative and absolute configurations by the MαNP acid method
Authors: Naito Junpei , Kuwahara Shunsuke , Watanabe Masataka , Decatur John , Bos Pieter H. , Van Summeren Ruben P. , Horst Bjorn Ter , Feringa Ben L. , Minnaard Adriaan J. , Harada Nobuyuki 
Published: July 2008

AbstractThe copper/chiral phosphoramidite (L1)‐catalyzed conjugate addition of dimethylzinc to cycloocta‐2,7‐dienone 4, followed by the methylation of the intermediate enolate, yielded a single isomer of 7,8‐dimethylcyclooct‐2‐enone (+)‐5. Compound (+)‐5 was subjected to the second conjugate addition with ent‐L1 giving only one stereoisomer of 2,3,7‐trimethylcyclooctanone (+)‐6, which was converted to 2,3,7‐trimethylcyclooctanol 7. To determine the relative and absolute configurations of these compounds, the 1H NMR anisotropy method using (S)‐(+)‐2‐methoxy‐2‐(1‐naphthyl)propionic acid {(S)‐(+)‐MαNP acid} 1 was applied. Racemic alcohol (±)‐7 was esterified with (S)‐(+)‐MαNP acid 1 yielding diastereomeric esters, which were efficiently separated by HPLC on silica gel affording the first‐eluted MαNP ester (–)‐10a and the second‐eluted one (–)‐10b. The relative and absolute configurations of ester (–)‐10a were determined to be (S;1R,2S,3R,7S) by analyzing the 1H and 13C NMR spectra of (–)‐10a and (–)‐10b, especially their HSQC‐TOCSY and NOESY spectra, and by applying the MαNP anisotropy method. The alcohol 7 formed from (+)‐6 was similarly esterified with (S)‐(+)‐MαNP acid 1 yielding an MαNP ester, which was identical with (–)‐10a, and the relative and absolute configurations of 2,3,7‐trimethylcyclooctanone (+)‐6 were determined to be (2S,3R,7S). Chirality, 2008. © 2008 Wiley‐Liss, Inc.
Synthesis and Biological Evaluation of N‐Acylhydrazones as Inhibitors of MurC and MurD Ligases
Authors: Šink Roman , Kovač Andreja , Tomašić Tihomir , Rupnik Veronika , Boniface Audrey , Bostock Julieanne , Chopra Ian , Blanot Didier , Mašič Lucija Peterlin , Gobec Stanislav , Zega Anamarija 
Published: July 2008

AbstractThe Mur ligases have an essential role in the intracellular biosynthesis of bacterial peptidoglycan, and they represent attractive targets for the design of novel antibacterials. A series of compounds with an N‐acylhydrazone scaffold were synthesized and screened for inhibition of the MurC and MurD enzymes from Escherichia coli. Compounds with micromolar inhibitory activities against both MurC and MurD were identified, and some of them also showed antibacterial activity.
Integrating Structure‐ and Ligand‐Based Virtual Screening: Comparison of Individual, Parallel, and Fused Molecular Docking and Similarity Search Calculations on Multiple Targets
Authors: Tan Lu , Geppert Hanna , Sisay Mihiret T. , Gütschow Michael , Bajorath Jürgen 
Published: July 2008

AbstractSimilarity searching is often used to preselect compounds for docking, thereby decreasing the size of screening databases. However, integrated structure‐ and ligand‐based screening schemes are rare at present. Docking and similarity search calculations using 2D fingerprints were carried out in a comparative manner on nine target enzymes, for which significant numbers of diverse inhibitors could be obtained. In the absence of knowledge‐based docking constraints and target‐directed parameter optimisation, fingerprint searching displayed a clear preference over docking calculations. Alternative combinations of docking and similarity search results were investigated and found to further increase compound recall of individual methods in a number of instances. When the results of similarity searching and docking were combined, parallel selection of candidate compounds from individual rankings was generally superior to rank fusion. We suggest that complementary results from docking and similarity searching can be captured by integrated compound selection schemes.
A 0.6 V, 2.11 MHz, 62 dB SFDR active‐RC filter in 0.13µm CMOS process
Authors: Seok Ji‐Hwan , Jo Jun‐Gi , Yoo Changsik 
Published: July 2008

AbstractActive‐RC biquad is proposed, which allows the DC level of the input of operational amplifier (op‐amp) to be different from that of the op‐amp output, enabling the low‐voltage operation. The proposed biquad realizes a second‐order transfer function with only one op‐amp, rendering even lower power consumption. By cascading two biquads, a 0.6 V fourth‐order filter is realized in a 0.13µm CMOS technology. While dissipating only 0.42 mW, the filter shows 2.11 MHz cut‐off frequency and 62 dB spurious‐free dynamic range. Copyright © 2008 John Wiley & Sons, Ltd.
Homocysteine enhances cardiac neural crest cell attachment in vitro by increasing intracellular calcium levels
Authors: Heidenreich David J. , Reedy Mark V. , Brauer Philip R. 
Published: July 2008

AbstractElevated homocysteine (Hcys) increases the risk of neurocristopathies. Previous studies show Hcys inhibits neural crest (NC) cell migration in vivo. However, the mechanisms responsible for this effect are unknown. Here, we evaluated the effect of Hcys on NC cell attachment in vitro and determined if any of the effects were due to altered Ca2+ signaling. We found Hcys enhanced NC cell attachment in a dose and substrate‐dependent manner. Ionomycin mimicked the effect of Hcys while BAPTA‐AM and 2‐APB blocked the effect of Hcys on NC attachment. In contrast, inhibitors of plasma membrane Ca2+ channels had no effect on NC attachment. Hcys also increased the emission of the intracellular Ca2+‐sensitive probe, Fluo‐4. These results show Hcys alters NC attachment by triggering an increase in intracellular Ca2+ possibly by generating inositol triphosphate. Hence, the teratogenic effect ascribed to Hcys may be due to perturbation of intracellular Ca2+ signaling. Developmental Dynamics 237:2117–2128, 2008. © 2008 Wiley‐Liss, Inc.
1,25‐dihydroxyvitamin D3 promotes IL‐10 production in human B cells
Authors: Heine Guido , Niesner Uwe , Chang Hyun‐Dong , Steinmeyer Andreas , Zügel Ulrich , Zuberbier Torsten , Radbruch Andreas , Worm Margitta 
Published: July 2008

Abstract1,25‐dihydroxyvitamin D3 (calcitriol) regulates immune responses, e.g., inhibits expression of IgE by B cells and enhances expression of IL‐10 by dendritic cells and T cells. We report here that activation of human B cells by B cell receptor, CD40 and IL‐4 signals induces expression of the gene for 25‐hydroxyvitamin‐D3–1α‐hydroxylase (CYP1α). Accordingly, these B cells generate and secrete significant amounts of calcitriol. In activated B cells calcitriol induces expression of the genes Cyp24, encoding a vitamin D hydroxylase, and Trpv6, encoding a calcium selective channel protein. Calcitriol enhances IL‐10 expression of activated B cells more than threefold, both by recruiting the vitamin D receptor to the promoter of Il‐10, and to lesser extent by modulation of calcium‐dependent signaling. The molecular link in activated B cells between vitamin D signaling, expression of IgE and IL‐10, and their ability to produce calcitriol from its precursor, suggest that pro‐vitamin D (25‐hydroxyvitamin D3) can be used as a modulator of allergic immune responses.Supporting Information for this article is available at http://www.wiley‐vch.de/contents/jc_2040/2008/38216_s.pdf