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Hydrophobic Character (hydrophobic + character)
Selected AbstractsApplication of the MTD-PLS method to heterocyclic dye,cellulose interactionsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 11 2007Ludovic Kurunczi Abstract The minimal topologic difference method in a projection in latent structures variant procedure was applied to a series of heterocyclic monoazo dyes of the type: RC6H4N = NY (R = benzothiazole, benzimidazole, N-containing aromatic pentacycles; Y = , acid, H acid, chromotropic acid, R acid). A statistically excellent model was obtained: RX2 = 0.625, RY2 = 0.940, Q2 = 0.822. The analysis of this model reveals the nature of dye,fiber interactions, which determine the dye affinity. Hydrophobic character in the R group and H-bond donor groups in a specific Y substitution position augment the dye affinity for cellulose. An increase of the polar nature of atoms in R depletes the affinity. Also some lateral substituents belonging to the Y coupling components suffer steric hindrance, and their presence is detrimental for the affinity. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Characterization of basic drug,human serum protein interactions by capillary electrophoresisELECTROPHORESIS, Issue 17 2006María A. Martínez-Gómez Abstract Drug,protein interactions are determining factors in the therapeutic, pharmacodynamic and toxicological drug properties. The affinity of drugs towards plasmatic proteins is apparently well established in bibliography. Albumin (HSA) especially binds neutral and negatively charged compounds; ,1 -acid glycoprotein,(AGP) binds many cationic drugs, lipoproteins bind to nonionic and lipophilic drugs and some anionic drugs while globulins interact inappreciably with the majority of drugs. In this paper, the characterization of the interaction between cationic drugs, ,-blockers and phenotiazines towards HSA, AGP, and both HSA + AGP mixtures of proteins under physiological conditions by CE-frontal analysis is presented. Furthermore, the binding of these drugs to all plasmatic proteins is evaluated by using ultrafiltration and CE. The results indicate that the hydrophobic character of compounds seems to be the key factor on the interaction between cationic drugs towards proteins. In fact, hydrophobic basic drugs bind in great extension to HSA, while hydrophilic basic drugs present low interactions with proteins and bind especially to AGP. [source] Capillary electrochromatography with monolithic silica column:,I.ELECTROPHORESIS, Issue 3 2003Preparation of silica monoliths having surface-bound octadecyl moieties, applications to the separation of neutral, charged species, their chromatographic characterization Abstract Monolithic silica columns with surface-bound octadecyl (C18) moieties have been prepared by a sol-gel process in 100 ,m ID fused-silica capillaries for reversed-phase capillary electrochromatography of neutral and charged species. The reaction conditions for the preparation of the C18-silica monoliths were optimized for maximum surface coverage with octadecyl moieties in order to maximize retention and selectivity toward neutral and charged solutes with a sufficiently strong electroosmotic flow (>,2 mm/s) to yield rapid analysis time. Furthermore, the effect of the pore-tailoring process on the silica monoliths was performed over a wide range of treatment time with 0.010 M ammonium hydroxide solution in order to determine the optimum time and conditions that yield mesopores of narrow pore size distribution that result in high separation efficiency. Under optimum column fabrication conditions and optimum mobile phase composition and flow velocity, the average separation efficiency reached 160,000 plates/m, a value comparable to that obtained on columns packed with 3 ,m C18-silica particles with the advantages of high permeability and virtually no bubble formation. The optimized monolithic C18-silica columns were evaluated for their retention properties toward neutral and charged analytes over a wide range of mobile phase compositions. A series of dimensionless retention parameters were evaluated and correlated to solute polarity and electromigration property. A dimensionless mobility modulus was introduced to describe charged solute migration and interaction behavior with the monolithic C18-silica in a counterflow regime during capillary electrochromatography (CEC )separations. The mobility moduli correlated well with the solute hydrophobic character and its charge-to-mass ratio. [source] Coordination chemistry of iron(III),porphyrin,antibody complexesFEBS JOURNAL, Issue 2 2002Influence on the peroxidase activity of the axial coordination of an imidazole on the iron atom An artificial peroxidase-like hemoprotein has been obtained by associating a monoclonal antibody, 13G10, and its iron(III),,,,,,,,- meso -tetrakis(ortho -carboxyphenyl)porphyrin [Fe(ToCPP)] hapten. In this antibody, about two-thirds of the porphyrin moiety is inserted in the binding site, its ortho -COOH substituents being recognized by amino-acids of the protein, and a carboxylic acid side chain of the protein acts as a general acid base catalyst in the heterolytic cleavage of the O,O bond of H2O2, but no amino-acid residue is acting as an axial ligand of the iron. We here show that the iron of 13G10,Fe(ToCPP) is able to bind, like that of free Fe(ToCPP), two small ligands such as CN,, but only one imidazole ligand, in contrast to to the iron(III) of,Fe(ToCPP) that binds two. This phenomenon is general for a series of monosubstituted imidazoles, the 2- and 4-alkyl-substituted imidazoles being the best ligands, in agreement with the hydrophobic character of the antibody binding site. Complexes of antibody 13G10 with less hindered iron(III),tetraarylporphyrins bearing only one [Fe(MoCPP)] or two meso-[ortho -carboxyphenyl] substituents [Fe(DoCPP)] also bind only one imidazole. Finally, peroxidase activity studies show that imidazole inhibits the peroxidase activity of 13G10,Fe(ToCPP) whereas it increases that of 13G10,Fe(DoCPP). This could be interpreted by the binding of the imidazole ligand on the iron atom which probably occurs in the case of 13G10,Fe(ToCPP) on the less hindered face of the porphyrin, close to the catalytic COOH residue, whereas in the case of 13G10,Fe(DoCPP) it can occur on the other face of the porphyrin. The 13G10,Fe(DoCPP),imidazole complex thus constitutes a nice artificial peroxidase-like hemoprotein, with the axial imidazole ligand of the iron mimicking the proximal histidine of peroxidases and a COOH side chain of the antibody acting as a general acid-base catalyst like the distal histidine of peroxidases does. [source] RUNOFF PRODUCTION AND EROSION PROCESSES ON A DEHESA IN WESTERN SPAIN,GEOGRAPHICAL REVIEW, Issue 3 2002ANTONIO CEBALLOS ABSTRACT. Runoff generation and soil erosion were investigated at the Guadalperalón experimental watershed (western Spain), within the land-use system known as dehesa, or open, managed evergreen forests. Season and type of surface were found to control runoff and soil-loss rates. Five soil units were selected as representative of surface types found in the study area: hillslope grass, bottom grass, tree cover, sheep trails, and shrub cover. Measurements were made in various conditions with simulated rainfall to gain an idea of the annual variation in runoff and soil loss. Important seasonal differences were noted due to surface cover and moisture content of soil, but erosion rates were determined primarily by runoff. Surfaces covered with grass and shrubs always showed less erosion; surfaces covered with holm oaks showed higher runoff rates, due to the hydrophobic character of the soils. Concentrations of runoff sediment during the simulations confirmed that erosion rates at the study site depended directly on the sediment available on the soil surface. [source] Computational study of the solvation of protoporphyrin IX and its Fe2+ complexINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 13 2008Teobaldo Cuya Guizado Abstract Molecular dynamics (MD) simulations of a well known hydrophobic structure, the heme (ferroprotoporphyrin IX) and its precursor in the heme synthesis, protoporphyrin IX (PPIX) are presented. The objective of the present study is to determine the stability of both structures in an aqueous medium, as well as the structure-solvent relation, hydration shells, and discuss their implications for biological processes. The density functional theory (DFT) is used for the electronic and structural characterization of both PPIX and its Fe2+ complex. A classical approach based on the Gromacs package is used for the MD. The radial distribution function g(r) is used to examine the allocation of water molecules around different regions of the porphyrins. The calculations demonstrate the heterogeneous character of the porphyrins with respect to the affinity with water molecules, the general hydrophobic character of the porphyrin ring bonded or not to the ion Fe, the hydrophilic character of the carboxylic oxygen that is unchanged upon iron binding, and the low hydrophilicity of Fe2+ in the heme. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Plasticizing Effects of Beeswax and Carnauba Wax on Tensile and Water Vapor Permeability Properties of Whey Protein FilmsJOURNAL OF FOOD SCIENCE, Issue 3 2005Pau Talens ABSTRACT: The possible plasticizing effect of beeswax (viscoelastic wax) and carnauba wax (elastic wax) on tensile and water vapor permeability properties of whey protein isolate (WPI) films was studied. For the experiments, 3 groups of films with different WPI:glycerol ratios (1:1; 1.5:1; 2:1, 2.5:1, and 3:1) were prepared. The 1st group was made without the addition of wax, and the latter 2 groups were made with the addition of beeswax and carnauba wax, respectively, mixing 1 part of wax to 1 part of WPI. Lipid particle size, water vapor permeability, tensile properties, and thickness of films were analyzed and measured. The results show that the incorporation of beeswax produced a plasticizing effect in WPI:glycerol films, whereas carnauba wax produced an anti-plasticizing effect. The moisture barrier properties of WPI:glycerol films benefit from the addition of beeswax, by both increase of the hydrophobic character and decrease of the amount of hydrophilic plasticizer required in the film. [source] Self-assembling properties of ionic-complementary peptides,JOURNAL OF PEPTIDE SCIENCE, Issue 3 2009Gabriella D'Auria Abstract Self-complementary synthetic peptides, composed by 8 and 16 residues, were analyzed by CD, NMR and small angle neutron scattering (SANS) techniques in order to investigate the relevance of charge and hydrophobic interactions in determining their self-assembling properties. All the sequences are potentially able to form fibrils and membranes as they share, with the prototype EAK16, a strictly alternating arrangement of polar and nonpolar residues. We find that 16-mer peptides show higher self-assembling propensities than the 8-mer analogs and that the aggregation processes are favored by salts and neutral pH. Peptide hydrophobic character appears as the most relevant factor in determining self-assembling. Solution conformational analysis, diffusion and SANS measurements all together show that the sequences with a higher self-assemble propensity are distributed, in mild conditions, between light and heavy forms. For some of the systems, the light form is mostly constituted by monomers in a random conformation, while the heavy one is constituted by ,-aggregates. In our study we also verified that sequences designed to adopt extended conformation, when dissolved in alcohol-water mixtures, can easily fold in helix structures. In that media, the prototype of the series appears distributed between helical monomers and ,-aggregates. It is worth noticing that the structural conversion from helical monomer to ,-aggregates, mimics ,-amyloid peptide aggregation mechanisms. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd. [source] Mutations on N -terminal region of Taiwan cobra phospholipase A2 result in structurally distorted effectsJOURNAL OF PEPTIDE SCIENCE, Issue 8 2008Yi-Ling Chiou Abstract In the present study, three Taiwan cobra PLA2 variants were prepared by adding an extra N -terminal Met, substituting Asn-1 by Met or deleting the N -terminal heptapeptide. Recombinant PLA2 mutants were expressed in Escherichia coli (E. coli), and purified to homogeneity by reverse phase HPLC. Fluorescence measurement showed that the hydrophobic character of the catalytic site, the microenvironment of Trp residues and energy transfer from excited Trp to 8-anilinonaphthalene sulfonate (ANS) were affected by N -terminal mutations. An alteration in the structural flexibility of the active site was noted with the mutants lacking the N -terminal heptapeptide or with an extra N -terminal Met added as evidenced by the inability of the two variants to bind with Ba2+. Moreover, modification of Lys residues and energy transfer within the protein-ANS complex revealed that the Ca2+ -induced change in the global structure of PLA2 was different from that in N -terminal variants. Together with the fact that an ,activation network' connects the N -terminus with the active site, our data suggest that mutagenesis on the N -terminal region affects directly the fine structure of the catalytic site, which subsequently transmits its influence in altering the structure outside the active site of PLA2. Copyright © 2008 European Peptide Society and John Wiley & Sons, Ltd. [source] Electrochemical synthesis of PEDOT derivatives bearing imidazolium-ionic liquid moietiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2009Markus Döbbelin Abstract Novel poly(3,4-ethylenedioxythiophene) (PEDOT) polymers bearing imidazolium-ionic liquid moieties were synthesized by electrochemical polymerizations. For this purpose, new functional monomers were synthesized having an 3,4-ethylenedioxythiophene (EDOT) unit and an imidazolium-ionic liquid with different anions such as tetrafluoroborate (BF), bis(trifluoromethane)sulfonimide ((CF3SO2)2N,), and hexafluorophosphate (PF). Next, polymer films were obtained by electrochemical synthesis in dicholoromethane solutions. Obtained polymers were characterized, revealing the characteristics of PEDOT in terms of electrochemical and spectroelectrochemical properties, FTIR, 1H NMR, and AFM microscopy. Interestingly, the hydrophobic character of electropolymerized films could be modified depending on the anion type. The hydrophobicity followed the trend PF > (CF3SO2)2N, > BF > pure PEDOT as determined by water contact angle measurements. Furthermore, the polymers could be dissolved in a range of polar organic solvents such as dimethylformamide, propylene carbonate, and dimethyl sulfoxide making these polymers interesting candidates for wet processing methods. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3010,3021, 2009 [source] Quantitative Structure,Activity Relationship Studies for the Binding Affinities of Imidazobenzodiazepines for the ,6 Benzodiazepine Receptor Isoform Utilizing Optimized Blockwise Variable Combination by Particle Swarm Optimization for Partial Least Squares ModelingMOLECULAR INFORMATICS, Issue 1 2007Leqian Hu Abstract Binding affinities of a series of substituted imidazobenzodiazepines for the ,6 Benzodiazepine Receptor (BzR) isoform are investigated by the Optimized Blockwise Variable Combination (OBVC) by Particle Swarm Optimization (PSO) based on Partial Least Squares (PLS) modeling. The QSAR analysis result showed that MolRef, AlogP, MRCM**-3, Rotatable bonds (Rotlbonds), Hydrogen Bond Acceptors (Hbond acceptor), five Jurs descriptors, two Shadow indices descriptors and principal moment of inertia are the most important descriptors among all the investigated descriptors. One can change the molar refractivity, the polar interactions between molecules, the shape of the molecules, the principal moments of inertia about the principal axes of a molecule, the hydrophobic character of the molecule, the number of Rotlbonds and Hbond acceptors of the compounds to adjust the binding affinities of imidazobenzodiazepine for the ,6 BzR isoform. The Quantitative Structure,Activity Relationship (QSAR) analysis result was also compared with MLR, PLS, and hierarchical PLS algorithms. It has been demonstrated that OBVC by PSO for PLS modeling shows satisfactory performance in the QSAR analysis. [source] Organic,inorganic hybrid materials derived from epoxy resin and polysiloxanes: Synthesis and characterizationPOLYMER ENGINEERING & SCIENCE, Issue 1 2008C.F. Canto In this study, hybrid materials based on epoxy resin were prepared as transparent self-supported films by a sol,gel process. 4,4,-Diaminodiphenylmethane or oligomeric epoxy resin were used as precursors, which were conveniently functionalized with trialkoxysilanes as end-groups. The effect of the introduction of poly (dimethylsiloxane) was also investigated. The hybrid films showed good thermal stability, a nondefined glass transition temperature, and a dense morphology without phase segregation. The tendency to a flat surface could be observed by atomic force microscopy. The hybrid films also showed good performance as coatings for glass plates, with an improved hydrophobic character in comparison to neat epoxy resin. POLYM. ENG. SCI., 48:141,148, 2008. © 2007 Society of Plastics Engineers [source] Association between plasticized starch and polyesters: Processing and performances of injected biodegradable systemsPOLYMER ENGINEERING & SCIENCE, Issue 5 2001Luc Avérous Different formulations of wheat thermoplastic starch (TPS) have been processed with various plasticizer/starch ratios and moisture contents. The biodegradable polyesters tested are polycaprolactone (PCL), polyester amide (PEA), polybutylene succinate adipate (PBSA) and polybutylene adipate co terephtalate (PBAT). TPS and polyesters are melt blended in different proportions by extrusion and then injected to obtain dumbbell specimens. Various properties are evaluated such as the mechanical properties (tensile and impact tests), and the hydrophilic character with contact angle measurements. Additionally, uniaxial shrinkage is evaluated. Results show that the addition of polyester to TPS increases the dimensional post-injection stability. Blend modulus values are close to the results of the classical rule of mixture. Elongation at break, resilience values and SEM observations seem to give some indications about the compatibility between both polymeric systems. PBAT and PEA present better results than PCL and PBSA. Contact angle measurement show that we have a drastic increase of the hydrophobic character from 10% of polyester in the blend. The different combinations of TPS and polyesters give a wide range of mechanical behavior for compostable materials, to be developed in specific applications. [source] Interactive functional poly(vinylidene fluoride) membranes with modulated lysozyme affinity: a promising class of new interfaces for contactor crystallizersPOLYMER INTERNATIONAL, Issue 12 2009Annarosa Gugliuzza Abstract BACKGROUND: One of the challenges of current researches in biotechnological fields is the achievement of regular and increasingly smaller protein crystals for genomics and biocatalyst applications. The membrane contactor-based methodology appears to be a time-effective and economically competitive technology for accomplishing this target. RESULTS: A new class of interactive polymeric interfaces enabling the nucleation of very small protein crystals in a short time through controlling attractive interactions is discussed. Specifically, the role of attractive interfacial forces between a model lysozyme solution and modified poly(vinylidene fluoride) membranes is examined. The insertion of amphiphilic motifs in the fluorinated membranes allows quicker agglomeration of protein crystals at the membrane surface reducing significantly the induction time for protein nucleation. The chemical nature of the modifier permits the modulation of the membrane affinity to the lysozyme, involving polar and non-polar attractive interactions and preserving intrinsic structural features, transport properties and the hydrophobic character of the interfaces, according to the basics of membrane crystallization technology. The formation of critical nuclei is observed after 3 h and micro-sized crystals are formed in less than 24 h. CONCLUSION: The experimental evidence suggests these membranes as a promising class of interactive interfaces that may rapidly bring advances in genomics research. Copyright © 2009 Society of Chemical Industry [source] Micellar solutions of amphipathic copolymers based on carboxymethyl cellulosePOLYMER INTERNATIONAL, Issue 6 2003Ya Cao Abstract A novel family of amphipathic copolymers based on carboxymethyl cellulose (CM-cellulose) has been synthesized through ultrasonic irradiation. Their micellar conformation in aqueous solution was studied by dynamic laser scattering, environmental scanning electron microscopy and gel permeation chromatography. The results show that conformation of copolymer molecules is totally different from that of CM-cellulose because of the introduction of the surface active macromonomers. Due to the influence of hydrophobic character and molecular weight, different amphipathic copolymers have different micellar conformations, such as cylindrical, spheroidal or ellipsoidal micelles. In the range of concentration tested, the normalized first-order autocorrelation function g(1)(,) of a copolymer of CM-cellulose and poly(ethylene oxide) dodecyl ether acrylate does not fit a single-exponential decay, indicating a polydisperse system and the existence of species of different shapes and size. At different concentrations, the hydrodynamic radii of micelles (R) almost distribute into two regions of smaller and larger size. With increasing copolymer concentration, the region of smaller R remains in the range 30,100,nm and is considered to represent monomolecular micelles, while the larger R region increases gradually with concentration, which means that polymolecular micelles increase in size. © 2003 Society of Chemical Industry [source] Surface modification of quarry stone by hexamethyldisiloxane plasma treatmentAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 10 2007Jose A. López-Barrera Abstract The surface of quarry stone was modified by continuous plasma polymerization of hexamethyldisiloxane. The hydrophilic surface of the quarry stone was made hydrophobic and impermeable to water. Three different reaction times were analyzed. All of them resulted in the formation of a homogenous layer on the quarry stone surface. Contact angle and FT-IR analyses show that the hydrophobic character of the surface is due to methyl groups on the surface. The change in the contact angle with temperature and the wetting temperature (Tw) are also discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Mixed aryl,alkyl organotin compounds, ArnMeSnCl3,n (Ar = RC6H4, R = H, ethyl, i-propyl, t-butyl; n -hexyl, n -octyl) and the effect of R upon antibiotic activity,APPLIED ORGANOMETALLIC CHEMISTRY, Issue 4 2005Ramesh N. Kapoor Abstract The synthesis of a new series of arylmethyltin chlorides is reported, ArnMeSnCl3,n (Ar = RC6H4, R = H, ethyl, i-propyl, t-butyl; hexyl, octyl). The synthesis involves initial formation of triarylmethyltin compounds, Ar3MeSn, via Grignard techniques followed by HCl,Et2O aryl group cleavage, preferably in a stepwise manner. Preliminary biological activity against Staphylococcus aureus illustrates the importance of the para-alkyl substituents and reinforces that an optimal hydrophobic character is needed for maximum efficacy. Copyright © 2005 John Wiley & Sons, Ltd. [source] Prediction of the 3D Structure of FMRF-amide Neuropeptides Bound to the Mouse MrgC11 GPCR and Experimental ValidationCHEMBIOCHEM, Issue 13 2007Jiyoung Heo Dr. Abstract We report the 3D structure predicted for the mouse MrgC11 (mMrgC11) receptor by using the MembStruk computational protocol, and the predicted binding site for the F-M-R-F-NH2 neuropeptide together with four singly chirally modified ligands. We predicted that the R-F-NH2 part of the tetrapeptide sticks down into the protein between the transmembrane (TM) domains 3, 4, 5, and 6. The Phe (F-NH2) interacted favorably with Tyr110 (TM3), while the Arg makes salt bridges to Asp161 (TM4) and Asp179 (TM5). We predicted that the Met extends from the binding site, but the terminal Phe residue sticks back into an aromatic/hydrophobic site flanked by Tyr237, Leu238, Leu240, and Tyr256 (TM6), and Trp162 (TM4). We carried out subsequent mutagenesis experiments followed by intracellular calcium-release assays that demonstrated the dramatic decrease in activity for the Tyr110Ala, Asp161Ala, and Asp179Ala substitutions, which was predicted by our model. These experiments provide strong evidence that our predicted G protein-coupled receptor (GPCR) structure is sufficiently accurate to identify binding sites for selective ligands. Similar studies were made with the mMrgA1 receptor, which did not bind the R-F-NH2 dipeptide; we explain this to be due to the increased hydrophobic character of the binding pocket in mMrgA1. [source] Novel Soluble Polyimide Containing 4- tert- Butyltoluene Moiety: Synthesis and CharacterizationCHINESE JOURNAL OF CHEMISTRY, Issue 11 2009Chenyi Wang Abstract Based on the synthesis of a rigid aromatic diamine, ,,, -bis(4-aminophenyl)-4-(t- butyl)toluene (1), a novel polyimide (PI) 3 was prepared from this diamine monomer and 4,4,-oxydiphthalic dianhydride via a one-step high-temperature polycondensation. FT-IR, 1H NMR and elemental analysis were used to investigate the chemical structures of 1 and 3. The results confirmed that they agreed with the proposed structures for both 1 and 3 completely. The obtained PI 3 showed excellent solubility in most common solvents such as N -methyl-2-pyrrolidinone, N,N -dimethylacetamide, N,N -dimethylformamide, chloroform, dichloromethane and tetrahydrofuran. The resulting strong and flexible film exhibited high thermal stability with the glass transition temperature at 317°C and the temperature at 10% weight loss beyond 519°C in both air and nitrogen atmospheres. Moreover, the film also showed high optical transparency, low dielectric constant (3.13 at 1 MHz), low water absorption (0.40%) and hydrophobic character. [source] Study on the Gas Phase Stability of Heme-binding Pocket in Cytochrome Tb5 and Its Mutants by Electrospray Mass SpectrometryCHINESE JOURNAL OF CHEMISTRY, Issue 12 2002Chong-Tian Yu Abstract To elucidate the effect of various amino add residues on the heme-binding pocket in cytochrome Tb5, several residues were chosen for replacement by means of site-directed mutagenesis. Comparison of the mass spectrum between the F35Y mutant and the wild type shows that the relative abundance of holoprotein ion of F35Y is lower than that of the wild type in gas phase. It is concluded that mutation from Phe35 residue to tyrosine decreases the hydrophobic character of cytochrome Tb5 heme pocket, which decreases the stability of heme-binding pocket. ESI-MS spectra of the mutants V61E, V61K, V61H and V61Y show various contribution of amino acid to the stability of heme-binding pocket. The small and non-polar residue Val61 was replaced with large or polar residues, resulting in enhancing the trend of heme leaving from the pocket. In addition, comparison of the mass relative abundance of holo-proteins among all the Vakil-mutants, shows mat their stability in gas phase appropriately submit the following order: wild type > V61H > V61E > V61K , V61Y. The extra great stability of quadruple sites mutant E44/48/56A/D60A shows that reduction of electrostatic or hydrogen bond interactions among the residues locating in the outside region of the heme edge remarkably affect the stability of heme. The results of analyzing the oxidation states of heme iron in Tb5 and its mutants by insource-CAD experiment suggest that the charge states of heme iron Maintain inflexible in mutation process. [source] QSAR for Inhibition of Pseudomonas Species Lipase by 1-Acyloxy-3- N-n -octylcarbamyl-benzenesMOLECULAR INFORMATICS, Issue 3 2009Shyh-Ying Chiou Abstract 1-Acyloxy-3- N-n -octylcarbamyl-benzenes (1,9) are synthesized to characterize the Quantitative Structure,Activity Relationship (QSAR) for the Third Acyl Group Binding Site (TACS) of Pseudomonas species lipase. Inhibitors 1,9 are characterized as pseudo or alternate substrate inhibitors of the enzyme. The inhibition constant (Ki) and carbamylation constant (k2) for the enzyme inhibitions by inhibitors 1,9 are determined. The carbamate carbons of the n -octylcarbamyl moieties of inhibitors 1,9 are nucleophilically attacked by the active site serine of the enzyme and the n -octylcarbamyl groups of inhibitors 1,9 are bound to the Acyl Group Binding Site (ACS) of the enzyme. Both pKi and log,k2 values are linearly corrected with the Hansch hydrophobicity , values of the substituents of the acyl moieties of inhibitors 1,7. The slopes for these corrections are 0.13 and 0.02, respectively. This result suggests that the enzyme inhibitions by inhibitors 1,7 have a common mechanism. Thus, all acyl moieties of inhibitors 1,7 should bind to the TACS of the enzyme since the acyl and carbamyl moieties of inhibitors 1,7 are meta to each other. This result also indicates that the major interaction between the acyl moiety of inhibitors 1,7 and the TACS of the enzyme is primarily the hydrophobic interaction. The more hydrophobic characters of inhibitors 1,7 are, the more tightly these inhibitors bind to the enzyme. In contrast, 1-triphenylacetoxy-3- N-n -octylcarbamyl-benzene (8) and 1-trimethylacetoxy-3- N-n -octylcarbamyl-benzene (9) do not bind to the TACS of the enzyme due to the fact that the inhibitions by both inhibitors are not linearly correlated with ,. It is possible that these two inhibitors are too bulky to fit into the TACS of the enzyme. [source] | |||||||||||||