Showing papers in "International Journal of Molecular Sciences in 2007"

Dietary Polyphenols and Their Biological Significance

Abstract: Dietary polyphenols represent a wide variety of compounds that occur in fruits, vegetables, wine, tea, extra virgin olive oil, chocolate and other cocoa products. They are mostly derivatives and/or isomers of flavones, isoflavones, flavonols, catechins and phenolic acids, and possess diverse biological properties such as antioxidant, antiapoptosis, anti-aging, anticarcinogen, anti-inflammation, anti-atherosclerosis, cardiovascular protection, improvement of the endothelial function, as well as inhibition of angiogenesis and cell proliferation activity. Most of these biological actions have been attributed to their intrinsic reducing capabilities. They may also offer indirect protection by activating endogenous defense systems and by modulating cellular signaling processes such as nuclear factor-kappa B (NF-κB) activation, activator protein-1(AP-1) DNA binding, glutathione biosynthesis, phosphoinositide 3 (PI3)-kinase/protein kinase B (Akt) pathway, mitogen-activated protein kinase (MAPK) proteins [extracellular signal-regulated protein kinase (ERK), c-jun N-terminal kinase (JNK) and P38 ] activation, and the translocation into the nucleus of nuclear factor erythroid 2 related factor 2 (Nrf2). This paper covers the most recent literature on the subject, and describes the biological mechanisms of action and protective effects of dietary polyphenols.

On the Extraction of Aromatic Compounds from Hydrocarbons by Imidazolium Ionic Liquids

Abstract: 1 Laboratory of Molecular Catalysis, Institute of Chemistry, UFRGS, Av. Bento Goncalves, 9500 Porto Alegre 91501-970 RS Brazil; E-mail: dupont@iq.ufrgs.br 2 PETROBRAS Research Center - CENPES-PETROBRAS, Hydrorefining and Special Processes, Av. Prof. Horacio Macedo, 950 Ilha do Fundao, Rio de Janeiro, 21941-598 RJ, Brazil * Author to whom correspondence should be addressed; E-mail: dupont@iq.ufrgs.br Received: 12 June 2007; in Revised Form: 22 June 2007 / Accepted: 22 June 2007 / Published: 2 July 2007 Abstract: The liquid-liquid equilibrium for the ternary system formed by n-octane and aromatic (alkylbenzenes) and heteroaromatic compounds (nitrogen and sulfur containing heterocyles) and 1-alkyl-3-methylimidazolium ionic liquids (ILs) associated with various anions has been investigated. The selectivity on the extraction of a specific aromatic compound is influenced by anion volume, hydrogen bond strength between the anion and the imidazolium cation and the length of the 1-methyl-3-alkylimidazolium alkyl side chain. The interaction of alkylbenzenes and sulfur heterocyles with the IL is preferentially through CH-π hydrogen bonds and the quantity of these aromatics in the IL phase decreases with the increase of the steric hindrance imposed by the substituents on the aromatic nucleus. In the case of nitrogen heterocycles the interaction occurs preferentially through N(heteroaromatic)-H(imidazolium) hydrogen bonds and the extraction process is largely controlled by the nitrogen heterocycle pKa. Competitive extraction experiments suggest that benzene, pyridine and dibenzothiophene do not compete for the same hydrogen bond sites of the IL. Keywords: ionic liquid, extraction, fuel, aromatics, hydrogen bonds.

Measurement of Antioxidant Activity of Wine Catechins, Procyanidins, Anthocyanins and Pyranoanthocyanins

Abstract: Nowadays, there is considerable interest in finding out about antioxidants thatare consumed in the habitual diet. It is known that polyphenols are involved in reducing therisk of diseases associated with oxidative stress. The in vitro antioxidant activity of theprincipal wine polyphenolic compounds (catechins, procyanidins, anthocyanins andpyranoanthocyanins) was studied in this work. Four distinct methods were used to assessthe antioxidant capacity of the tested compounds: inhibition of peroxynitrite mediatedtyrosine nitration, TEAC (Trolox equivalent antioxidant capacity assay), FRAP (Ferricreducing/antioxidant power assay) and TBARS (thiobarbituric acid reactive substances)methods. In general, it could be concluded that procyanidins were, among the in vitrotested groups, the ones which showed more antioxidant capacity using the four differentmethods, followed by anthocyanins and pyranoanthocyanins. On the basis of the simpleregression testing, there was a statistically significant relationship between these differentmethods used in aqueous phase (r > 0.92). However, no correlation was found between theresults obtained in lipid media with the TBARS method and those obtained in the aqueousmedia (peroxynitrite scavenging activity, TEAC and FRAP methods).

Prediction of Standard Enthalpy of Formation by a QSPR Model

Abstract: The standard enthalpy of formation of 1115 compounds from all chemicalgroups, were predicted using genetic algorithm-based multivariate linear regression (GA-MLR). The obtained multivariate linear five descriptors model by GA-MLR has correlationcoefficient ( R 2 = 0.9830 ). All molecular descriptors which have entered in this model arecalculated from chemical structure of any molecule. As a result, application of this modelfor any compound is easy and accurate.

Irradiation Effects on Phenolic Content, Lipid and Protein Oxidation and Scavenger Ability of Soybean Seeds

Abstract: The effect of medium doses of γ-irradiation (1–10 kGy) on total phenolic and tannin contents, lipid peroxidation, protein oxidation intensity and soluble protein content of soybean seeds, (genotype Ana), was investigated. Screening for antioxidant ability was performed using FRAP and DPPH methods. Total phenolic and tannin contents and DPPH scavenger activity were increased, while protein oxidation intensity was decreased by applied doses of γ-irradiation. Gamma irradiation provoked insignificant changes in lipid peroxidation and soluble protein content, while protein oxidation intensity was significantly decreased when dose of 10 kGy was applied. Presented results implicated that increased antioxidant capacity and protein stability of soybean seeds were increased after application of γ-irradiation.

Antioxidant Potential, Lipid Peroxidation Inhibition and Antimicrobial Activities of Satureja montana L. subsp. kitaibelii Extracts

Abstract: The antioxidant activity of different Satureja montana L. subsp. kitaibelii extracts was tested by measuring their ability to scavenge reactive hydroxyl radical during the Fenton reaction, using ESR spectroscopy. Also, the influence of these extracts on lipid peroxyl radicals obtained during lipid peroxidation of: (I) sunflower oil (37 oC, 3h) induced by 4,4′-azobis(4-cyanovaleric acid) (ACVA) and (II) liposomes induced by 2,2′-azobis(2- amidino-propane)dihydrochloride (AAPH) was studied. n-Butanol extract had the best antioxidant activity (100% at 0.5 mg/mL in Fenton reaction system; 89.21% at 5 mg/mL in system I; 83.38% at 5 mg/mL in system II). The antioxidant activities of the extracts significantly correlated with total phenolic content. The antimicrobial activity of Satureja montana L. subsp. kitaibelii extracts was investigated. Petroleum ether, chloroform and ethyl acetate extracts expressed a wide range of inhibiting activity against both grampositive and gram-negative bacteria.

Salting-out in Aqueous Solutions of Ionic Liquids and K3PO4: Aqueous Biphasic Systems and Salt Precipitation

Abstract: 1 Instituto de Tecnologia Quimica e Biologica, UNL, Av. da Republica, Apartado 127, 2780-901 Oeiras, Portugal 2 REQUIMTE, Departamento de Quimica, FCT, Universidade Nova de Lisboa, Quinta da Torre, 2829-516 Caparica, Portugal 3 Centro de Quimica Estrutural, IST-UTL, 1049-001 Lisboa, Portugal * Authors to whom correspondence should be addressed; E-mails: luis.rebelo@itqb.unl.pt; jnlopes@ist.utl.pt; Tel.: +351 21 4469 441 Received: 18 June 2007; in revised form: 25 July 2007 / Accepted:27 July 2007 / Published: 31 July 2007 Abstract: The salting-out effect produced by the addition of potassium phosphate, K

Protective Effect of Encapsulation in Fermentation of Limonene-contained Media and Orange Peel Hydrolyzate

Abstract: This work deals with the application of encapsulati on technology to eliminate inhibition by D-limonene in fermentation of orange wastes to ethanol. Orange peel was enzymatically hydrolyzed with cellulase and pectina se. However, fermentation of the released sugars in this hydrolyzate by freely suspe nded S. cerevisiae failed due to inhibition by limonene. On the other hand, encapsulation of S. cerevisiae in alginate membranes was a powerful tool to overcome the negative effects of limonene. The encapsulated cells were able to ferment the orange peel hydrolyzate in 7 h, and produce ethanol with a yield of 0.44 g/g fermentable sugars. Cultivation of the encapsul ated yeast in defined medium was successful, even in the presence of 1.5% (v/v) limo nene. The capsules' membranes were selectively permeable to the sugars and the other n utrients, but not limonene. While 1% (v/v) limonene was present in the culture, its c oncentration inside the capsules was not more than 0.054% (v/v).

A Possible Industrial Solution to Ferment Lignocellulosic Hydrolyzate to Ethanol: Continuous Cultivation with Flocculating Yeast.

Abstract: The cultivation of toxic lignocellulosic hydrolyzat es has become a challenging research topic in recent decades. Although several cultivation methods have been proposed, numerous questions have arisen regarding their indu strial applications. The current work deals with a solution to this problem which has a g ood potential application on an industrial scale. A toxic dilute-acid hydrolyzate w as continuously cultivated using a high- cell-density flocculating yeast in a single and ser ial bioreactor which was equipped with a settler to recycle the cells back to the bioreactor s. No prior detoxification was necessary to cultivate the hydrolyzates, as the flocks were able to detoxify it in situ . The experiments were successfully carried out at dilution rates up to 0.52 h -1 . The cell concentration inside the bioreactors was between 23 and 35 g-DW/L, while the concentration in the effluent of the settlers was 0.32 ± 0.05 g-DW/L. An ethanol yield of 0.42-0.46 g/g-consumed sugar was achieved, and the residual sugar concentration was less than 6% of the initial fermentable sugar (glucose, galactose and mannose) of 35.2 g/L.

Relationships between Xanthohumol and Polyphenol Content in Hop Leaves and Hop Cones with Regard to Water Supply and Cultivar

Abstract: Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, SI-1111 Ljubljana, Slovenia, E-mails: milica.kac@bf.uni-lj.si; veronika.abram@bf.uni-lj.si * Author to whom correspondence should be addressed; E-mail: barbara.ceh-breznik@guest.arnes.si Received: 30 May 2007; in revised form: 20 August 2007 / Accepted: 9 September 2007 / Published: 12 September 2007 Abstract: The effect of water supply – especially of drought stress – on the content of some secondary metabolites in hops ( Humulus lupulus L.) was studied. The experiment took place in 2006. Some relevant data from 2005 were included for comparison. Leaves and cones of nine hop cultivars grown under field conditions as well as in a pot experiment under three water regimes were analyzed. The cultivars ranged from those most grown in Slovenia to promising crossbreed being tested. Leaves were sampled from July 18, 2006 to August 18, 2006, while cones were picked in the time of technological maturity. Standard analytical methods were applied to determine the contents of xanthohumol, polyphenols and α-acids in hop leaves and hop cones. The contents of the secondary metabolites in question depended more on the cultivar under investigation than on the water supply, at least as far the growing conditions for a relatively normal development of the plant were met. Keywords: Xanthohunol, polyphenols, hops, Humulus lupulus , water supply

Synthesis and Ab Initio/DFT Studies on 2-(4-methoxyphenyl)benzo[d]thiazole

Abstract: 2-aminothiophenol and 4-methoxybenzaldehyde were cyclized under microwave irridation and solvent free conditions to synthesize 2-(4-methoxyphenyl)benzo[d]thiazole. The molecular structure and vibrational frequencies of the title compound in the ground state have been investigated with ab initio (HF) and density functional theory methods (BLYP, B3LYP, B3PW91 and mPW1PW91) implementing the standard 6–311G(d,p) basis set. Comparison of the observed fundamental vibrational frequencies of title compound and calculated results by HF and DFT methods indicate that B3LYP is superior to the scaled HF approach for molecular problems.

A Spectral-SAR Model for the Anionic-Cationic Interaction in Ionic Liquids: Application to Vibrio fischeri Ecotoxicity

Abstract: Within the recently launched the spectral-structure activity relationship (S-SAR) analysis, the vectorial anionic-cationic model of a generic ionic liquid is proposed, along with the associated algebraic correlation factor in terms of the measured and predicted activity norms. The reliability of the present scheme is tested by assessing the Hansch factors, i.e. lipophylicity, polarizability and total energy, to predict the ecotoxicity endpoints of wide types of ionic liquids with ammonium, pyridinium, phosphonium, choline and imidazolium cations on the aquatic bacteria Vibrio fischeri. The results, while confirming the cationic dominant influence when only lipophylicity is considered, demonstrate that the anionic effect dominates all other more specific interactions. It was also proved that the S-SAR vectorial model predicts considerably higher activity for the ionic liquids than for its anionic and cationic subsystems separately, in all considered cases. Moreover, through applying the least norm-correlation path principle, the complete toxicological hierarchies are presented, unfolding the ecological rules of combined cationic and anionic influences in ionic liquid toxicity.

Structural Characteristics and Reactivity Relationships of Nitroaromatic and Nitramine Explosives - A Review of Our Computational Chemistry and Spectroscopic Research

Abstract: Although much has been discovered, discussed and written as to problems of contamination by various military unique compounds, particularly by the nitrogen based energetics (NOCs), remaining problems dictate further evaluation of actual and potential risk to the environment by these energetics and their derivatives and metabolites through determination of their environmental impact—transport, fate and toxicity. This work comprises an effort to understand structural relationships and degradation mechanisms of current and emerging explosives, including nitroaromatic; cyclic and cage cyclic nitramine; and a nitrocubane. This review of our computational chemistry and spectroscopic research describes and compares competitive degradation mechanisms by free radical oxidative, reductive and alkali hydrolysis, relating them, when possible, to environmental risk.

Analysis of Phenacylester Derivatives of Fatty Acids from Human Skin Surface Sebum by Reversed-Phase HPLC: Chromatographic Mobility as a Function of Physico-Chemical Properties

Abstract: A set of 13 fatty acids was transformed into their phenacyl esters by reaction with phenacyl bromide in acetonitrile using 18-crown-6 as phase-transfer catalyst. Conditions for the RP-18 HPL chromatographic separation of most of the esters has been worked out. Using this standard the fatty acid spectra from skin surface sebum lipids of 17 test persons was taken after microwave-assisted hydrolysis, neutralization and extraction with n-hexane. Quantitative evaluation of the chromatograms exhibits that oleic acid predominates in the sebum of all test persons. In the second part of the work the chromatographic mobility (RE values) of fatty acid phenacyl esters is correlated with calculated physico-chemical parameters of the corresponding acids. The best linear correlation was found between the RE and the logP values. This is helpful for the structural elucidation of un-identified fatty acids in a chromatogram.

Modification of Low Molecular Weight Polysaccharides from Tremella Fuciformis and Their Antioxidant Activity in Vitro

Abstract: In this study, sulfated low molecular-weight Tremella fuciformis polysaccharides (SLTP) with different sulfate contents were synthesized and their antioxidant activities, including superoxide anion radical, 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical and hydroxyl radical scavenging activities were investigated. The results indicated that, compared to natural Tremella fuciformis polysaccharide (TP) and low molecular weight Tremella fuciformis polysaccharide (LTP), sulfated LTP (SLTP) exhibited stronger scavenging activity towards superoxide anion, DPPH and hydroxyl radicals. In all the cases the effect was found to be dose dependent. The scavenging activity of SLTP was found to be in parallel with the degree of sulfation of SLTP.

Introducing Spectral Structure Activity Relationship (S-SAR) Analysis. Application to Ecotoxicology

Abstract: A novel quantitative structure-activity (property) relationship model, namely Spectral-SAR, is presented in an exclusive algebrai c way replacing the old-fashioned multi-regression one. The actual S-SAR method interprets structural descriptors as vectors in a generic data space that is further mapped into a full orthogonal space by means of the Gram-Schmidt algorithm. Then, by coordinated transformation between the data and orthogonal spaces, the S-SAR equation is given under simple determinant form for any chemical-biological interactions under study. While proving to give the same analytical equation and correlation results with standard mult ivariate statistics, the actual S-SAR frame allows the introduction of the spectral norm as a valid substitute for the correlation factor, while also having the advantage to design t he various related SAR models through the introduced "minimal spectral path" rule. An app lication is given performing a complete S-SAR analysis upon the Tetrahymena pyriformis ciliate species employing its reported eco-toxicity activities among relevant classes of x enobiotics. By representing the spectral norm of the endpoint models against the concerned s tructural coordinates, the obtained S-SAR endpoints hierarchy scheme opens the perspective to further design the eco- toxicological test batteries with organisms from di fferent species.

Rheological Behaviors of Polyacrylonitrile/1-Butyl-3- Methylimidazolium Chloride Concentrated Solutions

Abstract: One of the room temperature ionic liquids (RTILs), 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) was chosen to prepare the concentrated solutions of Polyacrylonitrile (PAN). The rheological behaviors of the solutions were measured with rotational rheometry under different conditions, including temperatures, concentration, and molecular weight of PAN. The solutions exhibited shear-thinning behaviors, similar to that of PAN/DMF solutions. The viscosities decreased with the increasing of shear rates. However, the viscosity decreased sharply at high shear rates when the concentration was up to 16wt%. The dependence of the viscosity on temperature was analyzed through the determination of the apparent activation energy. Unusually, the viscosity of solutions of higher concentration is lower than that of lower concentration. Similarly, the viscosity of low molecular weight PAN was higher than high molecular weight PAN at high shear rates. The dynamic rheological measurement indicates the loss modulus is much higher than storage modulus. The trend of complex viscosity is similar with the result of static rheological measurement. The interaction between PAN and ionic liquid [BMIM]Cl was discussed.

Polyphenolic Profile and Antioxidant Activities of Oolong Tea Infusion under Various Steeping Conditions

Abstract: The phenolic profile and antioxidant activities of oolong tea extract were investigated after tea was steeped in 90 or 100 o C water for 3 or 10 min. The extraction yield increased with increasing temperature and ext ended steeping time. However, higher temperature and longer time (100 o C water for 10 min) led to loss of phenolics. The aqueous extract of oolong tea (AEOT) at 100 o C for 3 min exhibited the strongest antioxidant activity. The major polyphenolic components of the AEOT were identified as (-)-epigallocatechin (EGC), (-)-epigallocatechin ga llate (EGCG) and (-)-epicatechin-3- gallate (ECG). The two major catechins (EGC and EGCG) in the tea infusion contributed significantly to the investigated antioxidant activ ities (i.e., the 2,2-diphenyl-2- picrylhydrazyl hydrate (DPPH) radical scavenging and superoxide radical scavenging activities) with high correlation values in r = 0.9486 and 0.9327 for the EGC and r = 0.9592 and 0.8718 for the EGCG, respectively.

A Centrifugation-based Method for Preparation of Gold Nanoparticles and its Application in Biodetection

Abstract: Gold nanoparticles (AuNPs) have found widespread applications in life sciences. While synthesis of monodispersed AuNPs has been fairly convenient by using chemical reduction of chloroauric acid by sodium citrate, we found that AuNPs of high quality and high concentrations were not readily obtained via this method. As an example, we showed that monodispersed 13-nm AuNPs were readily synthesized at relatively low concentrations ( e. g. 3.5 nM); in contrast, 13-nm AuNPs of 17 nM obtained by the direct reduction method were irregularly shaped and not well dispersed. In this work, we demonstrated that AuNPs of high concentration could be prepared by a two-step approach, i.e. chemical reduction at low concentrations and subsequent centrifugation. Compared to the direct reduction method, this new two-step method led to AuNPs with high salt resistance and high stability, which are essential for the preparation of DNA-AuNPs conjugates for DNA biodetection.

Hydroformylation of Cyclohexene with Carbon Dioxide and Hydrogen Using Ruthenium Carbonyl Catalyst: Influence of Pressures of Gaseous Components

Abstract: Hydroformylation of cyclohexene was studied with a catalyst system of Ru3(CO)12 and LiCl using H2 and CO2 instead of CO in NMP. The influence of H2 and CO2 pressures on the total conversion and the product distribution was examined. It was shown that increasing total pressure of H2 and CO2 promoted the reverse water gas shift reaction and increased the yield of cyclohexanecarboxaldehyde. Its hydrogenation to cyclohexanemethanol was promoted with increasing H2 pressure but suppressed with increasing CO2 pressure. Cyclohexane was also formed along with those products and this direct hydrogenation was suppressed with increasing CO2 pressure. The roles of CO2 as a promoter as well as a reactant were further examined by phase behavior observations and high pressure FTIR measurements.

Correlations of the Specific Rates of Solvolysis of Aromatic Carbamoyl Chlorides, Chloroformates, Chlorothionoformates, and Chlorodithioformates Revisited

Abstract: Additional specific rates of solvolysis are determined for phenyl chloroformate. These values are combined with literature values to give a total of 49 data points, which are used within simple and extended Grunwald-Winstein treatments. Literature values are also brought together to allow treatments in more solvents than previously for three N-aryl-N-methylcarbamoyl chlorides, phenyl chlorothionoformate, phenyl chlorodithioformate, and N,N-diphenylcarbamoyl chloride. For the last two listed, moderately strong evidence for a meaningful inclusion of a term governed by the aromatic ring parameter (I) was indicated. No evidence was found requiring inclusion of this parameter for ionization reactions with only one aromatic ring on the nitrogen of carbamoyl chlorides or for the solvolyses of the chloroformate or chlorothionoformate proceeding by an addition-elimination (association-dissociation) mechanism.

Developments in Molecular Recognition and Sensing at Interfaces

Abstract: Katsuhiko Ariga*, Jonathan P. Hill and Hiroshi Endo Supermolecules Group, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba 305-0044, Japan * Author to whom correspondence should be addressed; E-mail: ARIGA.Katsuhiko@nims.go.jp Received: 6 August 2007 / Accepted: 20 August 2007 / Published: 22 August 2007 Abstract: In biological systems, molecular recognition events occur mostly within interfacial environments such as at membrane surfaces, enzyme reaction sites, or at the interior of the DNA double helix. Investigation of molecular recognition at model interfaces provides great insights into biological phenomena. Molecular recognition at interfaces not only has relevance to biological systems but is also important for modern applications such as high sensitivity sensors. Selective binding of guest molecules in solution to host molecules located at solid surfaces is crucial for electronic or photonic detection of analyte substances. In response to these demands, molecular recognition at interfaces has been investigated extensively during the past two decades using Langmuir monolayers, self-assembled monolayers, and lipid assemblies as recognition media. In this review, advances of molecular recognition at interfaces are briefly summarized. Keywords: molecular recognition, interface, air-water interface, Langmuir-Blodgett film, self-assembled monolayer, molecular assembly. 1. Introduction Molecular recognition is one of the most important chemical events in biological systems and has been mimicked in supramolecular chemistry as, for example, artificial enzymes [1-3]. Most of the supramolecular systems for molecular recognition are composed of molecularly dispersed states in homogeneous solutions. However, this is quite apart from the situation seen in biological systems. Molecular recognition in living systems occurs mostly at interfacial environments such as membrane surfaces, enzyme reaction sites, or at the interior of the DNA double helix.

Electrochemical Studies of Camptothecin and Its Interaction with Human Serum Albumin

Abstract: Camptothecin, an anticancer component from Camptotheca acuminate, mayinteract with human serum albumin (HSA) at the subdomain IIA (site I), and then convert toits inactive form(carboxylate form). In this paper, the detailed electrochemical behaviors ofcamptothecin at a pyrolytic graphite electrode is presented. The interaction betweencamptothecin and HSA is also studied by electrochemical technique. By comparing withbovine serum albumin (BSA), which is highly homologous to HSA, we prove thatcamptothecin can specifically bind to HSA. Meanwhile, the inhibitory influence of sodiumsalicylate to this binding is also discussed.

Self-assembly and Fractal Feature of Chitosan and Its Conjugate with Metal Ions: Cu (II) / Ag (I)

Abstract: In this paper, we investigated the self-assembly and fractal feature of chitosan and Ag (I), Cu (II)-chitosan due to the theoretical and practical importance of chitosan in biomedical engineering, biomaterials and environmental sciences etc. The self-assembly and fractal structures of chitosan and Ag (I), Cu (II)-chitosan were observed using atomic force microscope (AFM), and the fractal dimensions of chitosan and Ag (I)-chitosan were calculated. The results indicate that their fractal dimension is approximate 2 and relates with the accumulation degree: the fractal dimension decreases with the accumulation degree increases. In addition, a new self-assembly strategy was presented to study the lyotropic liquid crystals (LLC) of chitosan and the formation mechanism of LLC was primarily analyzed and discussed. All of these results are valuable for the structure/function relationship study of chitosan and useful for application in biomedical materials.

Electronegativity Equalization Method: Parameterization and Validation for Large Sets of Organic, Organohalogene and Organometal Molecule

Abstract: The Electronegativity Equalization Method (EEM) is a fast approach for charge calculation. A challenging part of the EEM is the parameterization, which is performed using ab initio charges obtained for a set of molecules. The goal of our work was to perform the EEM parameterization for selected sets of organic, organohalogen and organometal molecules. We have performed the most robust parameterization published so far. The EEM parameterization was based on 12 training sets selected from a database of predicted 3D structures (NCI DIS) and from a database of crystallographic structures (CSD). Each set contained from 2000 to 6000 molecules. We have shown that the number of molecules in the training set is very important for quality of the parameters. We have improved EEM parameters (STO-3G MPA charges) for elements that were already parameterized, specifically: C, O, N, H, S, F and Cl. The new parameters provide more accurate charges than those published previously. We have also developed new parameters for elements that were not parameterized yet, specifically for Br, I, Fe and Zn. We have also performed crossover validation of all obtained parameters using all training sets that included relevant elements and confirmed that calculated parameters provide accurate charges.

Results from the Use of Molecular Descriptors Family on Structure Property/Activity Relationships

Abstract: 1 Technical University, Cluj-Napoca, 15 Constantin Daicoviciu, 400020 Cluj-Napoca, Romania E-mail: lori@academicdirect.org 2 “Iuliu Ha Ńieganu” University of Medicine and Pharmacy, 13 Emil Isac, 40023 Cluj-Napoca, Romania E-mail: sorana@sorana.academicdirect.ro * Author to whom correspondence should be addressed. E-mail: sorana@sorana.academicdirect.ro Received: 14 January 2007 / Accepted: 2 March 2007 / Published: 9 March 2007 Abstract: The aim of the paper is to present the results obtained by utilization of an original approach called Molecular Descriptors Family on Structure-Property (MDF-SPR) and Structure-Activity Relationships (MDF-SAR) applied on classes of chemical compounds and its usefulness as precursors of models elaboration of new compounds with better properties and/or activities and low production costs. The MDF-SPR/MDF-SAR methodology integrates the complex information obtained from compound’s structure in unitary efficient models in order to explain properties/activities. The methodology has been applied on a number of thirty sets of chemical compounds. The best subsets of molecular descriptors family members able to estimate and predict property/activity of interest were identified and were statistically and visually analyzed. The MDF-SPR/MDF-SAR models were validated through internal and/or external validation methods. The estimation and prediction abilities of the MDF-SPR/MDF-SAR models were compared with previous reported models by applying of correlated correlation analysis, which revealed that the MDF-SPR/MDF-SAR methodology is reliable. The MDF-SPR/MDF-SAR methodology opens a new pathway in understanding the relationships between compound’s structure and property/activity, in property/activity prediction, and in discovery, investigation and characterization of new chemical compounds, more competitive as costs and property/activity, being a method less expensive comparative with experimental methods. Keywords: Molecular Descriptors Family (MDF), Structure Property Relationships (SPR), Structure Activity Relationships (SAR), Activity/Property Modeling; Chemical Compounds, Open System

How Good Can the Characteristic Polynomial Be for Correlations

Abstract: The aim of this study was to investigate the characteristic polynomials resulting from the molecular graphs used as molecular descriptors in the characterization of the properties of chemical compounds. A formal calculus method is proposed in order to identify the value of the characteristic polynomial parameters for which the extremum values of the squared correlation coefficient are obtained in univariate regression models. The developed calculation algorithm was applied to a sample of nonane isomers. The obtained results revealed that the proposed method produced an accurate and unique solution for the best relationship between the characteristic polynomial as molecular descriptor and the property of interest.

Solubilization of Single-walled Carbon Nanotubes with Single-stranded DNA Generated from Asymmetric PCR.

Abstract: Carbon nanotubes (CNTs) can be effectively dispersed and functionalized by wrapping with long single-stranded DNA (ssDNA) synthesized by asymmetric PCR. The ssDNA-CNTs attached on surface of glass carbon electrode made it possible for electrochemical analysis and sensing, which was demonstrated by reduction of H2O2 on hemoglobin/ssDNA-CNTs modified electrodes. This research showed the potential application of DNA-functionalised CNTs in construction of future electrochemical biosensors.

Microwave-Assisted Synthesis of Phenothiazine and Quinoline Derivatives

Abstract: 1 “Babe s-Bolyai” University, Faculty of Chemistry and Chemical Engineering, Organic Chemistry Department, Cluj-Napoca-Ro E-mail: gluiza@chem.ubbcluj.ro, E-mail: castelia@chem.ubbcluj.ro , E-mail: pdan@chem.ubbcluj.ro 2 INCDTIM-Cluj-Napoca-Ro E-mail: esurducan@gmail.com 3 Institute of Organic Chemistry, National NMR Laboratory, Bucharest-Ro. E-mail: calind@rdslink.ro 4 Universitee de la Mediteranee, Faculte de Pharmacie, Marseille CEDEX 5, E-mail: barbe@pharmacie.univ-mrs.fr E-mail: mahamoud@pharmacie.univ-mrs.fr * Author to whom correspondence should be addressed. Received: 27 October 2006 / Accepted: 12 February 2007 / Published: 13 February 2007 Abstract: Application of a dynamic microwave power system in the chemical synthesis of some phenothiazine and quinoline derivatives is described. Heterocyclic ring formation, aromatic nucleophilic substitution and heterocyclic aldehydes/ketones condensation reactions were performed on solid support, or under solvent free reaction conditions. The microwave-assisted Duff formylation of phenothiazine was achieved. Comparison of microwave-assisted synthesis with the conventional synthetic methods demonstrates advantages related to shorter reaction times and in some cases better reaction yields. Keywords: MAOS, Quinoline, Pyrido[3,2-g]quinoline, Phenothiazine, formylation. 1. Introduction Microwave assisted organic synthesis became an increasingly popular technique in academic and industrial research laboratories, due to certain advantages, particularly shorter reaction times and rapid optimization of chemical reactions. The experimental technique applied for the organic syntheses described below, is based on microwave power processing of materials using a dynamic control of the microwave power magnetron

Antiplatelet Effect and Selective Binding to Cyclooxygenase (COX) by Molecular Docking Analysis of Flavonoids and Lignans

Abstract: The known flavonoids ginkgetin (1), taiwanhomoflavone A (2), taiwanhomoflavone B (3), and taiwanhomoflavone C (4) and eight known lignans: justicidin B (9), justicidin C (10), justicidin D (11), chinensinaphthol methyl ether (12), procumphthalide A (13), procumbenoside A (15), and ciliatosides A (16) and B (17) were isolated from Cephalotaxus wilsoniana and Justicia species, respectively. The antiplatelet effects of the above constituents on human platelet-rich plasma (PRP) were evaluated. Of the compounds tested on human PRP, compounds 1, 4, 9, and 11 showed inhibition of secondary aggregation induced by adrenaline. Compound 1 had an inhibitory effect on cyclooxygenase-1 (COX-1). Molecular docking studies revealed that 1 and the related compounds apigenin (5), cycloheterophyllin (6), broussoflavone F (7), and quercetin (8) were docked near the gate of active site of COX-1. It indicated that the antiplatelet effect of 1, 4, 9, and 11 is partially owed to suppression of COX-1 activity and reduced thromboxane formation. Flavonoids, 1, 5, 6, 7, and 8 may block the gate of the active site of COX-1 and interfere the conversion of arachidonic acid to prostaglandin (PG) H2 in the COX-1 active site.