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1

Structure and function studies on enzymes with a catalytic carboxyl group(s): from ribonuclease T1 to carboxyl peptidases  

PubMed Central

A group of enzymes, mostly hydrolases or certain transferases, utilize one or a few side-chain carboxyl groups of Asp and/or Glu as part of the catalytic machinery at their active sites. This review follows mainly the trail of studies performed by the author and his colleagues on the structure and function of such enzymes, starting from ribonuclease T1, then extending to three major types of carboxyl peptidases including aspartic peptidases, glutamic peptidases and serine-carboxyl peptidases.

TAKAHASHI, Kenji

2013-01-01

2

Carboxylic acid functional group analysis using constant neutral loss scanning-mass spectrometry  

Microsoft Academic Search

The present study describes the development of a new analytical technique for the functional group determination of the carboxylic moiety using atmospheric pressure chemical ionization-mass spectrometry (APCI-MS\\/MS) operated in the constant neutral loss scanning (CNLS) mode. Carboxylic groups were first derivatized into their corresponding methyl esters by reacting with BF3\\/methanol mix and the reaction mixture was then directly injected into

Julien Dron; Gregory Eyglunent; Brice Temime-Roussel; Nicolas Marchand; Henri Wortham

2007-01-01

3

Gas-Phase Reactivity of Carboxylic Acid Functional Groups with Carbodiimides  

NASA Astrophysics Data System (ADS)

Gas-phase modification of carboxylic acid functionalities is performed via ion/ion reactions with carbodiimide reagents [ N-cyclohexyl- N'-(2-morpholinoethyl)carbodiimide (CMC) and [3-(3-Ethylcarbodiimide-1-yl)propyl]trimethylaminium (ECPT)]. Gas-phase ion/ion covalent chemistry requires the formation of a long-lived complex. In this instance, the complex is stabilized by an electrostatic interaction between the fixed charge quaternary ammonium group of the carbodiimide reagent cation and the analyte dianion. Subsequent activation results in characteristic loss of an isocyanate derivative from one side of the carbodiimide functionality, a signature for this covalent chemistry. The resulting amide bond is formed on the analyte at the site of the original carboxylic acid. Reactions involving analytes that do not contain available carboxylic acid groups (e.g., they have been converted to sodium salts) or reagents that do not have the carbodiimide functionality do not undergo a covalent reaction. This chemistry is demonstrated using PAMAM generation 0.5 dendrimer, ethylenediaminetetraacetic acid (EDTA), and the model peptide DGAILDGAILD. This work demonstrates the selective gas-phase covalent modification of carboxylic acid functionalities.

Prentice, Boone M.; Gilbert, Joshua D.; Stutzman, John R.; Forrest, William P.; McLuckey, Scott A.

2013-01-01

4

Ab initio study of Li adsorption in carbon nanotubes functionalized with amine and carboxyl groups  

NASA Astrophysics Data System (ADS)

The lithium adsorption energies and electronic structures of pristine ((8,0)) single-walled carbon nanotube (SWCNT) and functionalized carbon nanotubes with amine and carboxyl groups (NH2/((8,0)) and COOH/((8,0))) were studied using density functional theory. The results show that the adsorption energies of lithium inside and outside of ((8,0)) SWCNT differ very little from each other. When the lithium is doped in carbon nanotubes, charge transfer takes place from the lithium to the nanotubes. After functionalization of carbon nanotubes with amine (sbnd NH2) and carboxyl (sbnd COOH) groups, various positions for lithium adsorption around the functional groups can be served. The adsorption energy of lithium in these positions is greater than that of lithium in pure ((8,0)) SWCNT. When the lithium was doped in NH2/((8,0)) and COOH/((8,0)), an energy gap between valence and conduction bands is observed, and the conductivity is reduced relative to lithium-doped non-functionalized carbon nanotubes.

Jalili, Seifollah; Jamali, Maryam; Schofield, Jeremy

2013-06-01

5

Adsorption reactions of carboxylic acid functional groups on sodium aluminoborosilicate glass fiber surfaces.  

PubMed

Multicomponent silicate glasses are ubiquitous in modern society as evidenced by their inclusion in applications ranging from building materials and microelectronics to biomedical implants. Of particular interest in this study is the interface between multicomponent silicate glasses and adhesive polymers. These polymeric systems often possess a variety of different organic functional groups. In this study, we selected acetic acid as a probe molecule representative of the carboxylic acid functional group found in many adhesives. We have used Fourier transform infrared spectroscopy (FT-IR) and NMR to study the interaction of acetic acid with the surface of sodium aluminoborosilicate continuous glass fibers. Methods were developed that enable analyses to be carried out without damaging or altering the pristine as drawn fiber surface. While dosing the surface of fumed silica with acetic acid resulted in the formation of silyl ester groups, analogous dosing of sodium aluminoborosilicate glass fibers resulted in the formation of carboxylate species, principally coordinated to sodium, while silyl ester groups were not observed. PMID:21038910

Stapleton, Joshua J; Suchy, Daniel L; Banerjee, Joy; Mueller, Karl T; Pantano, Carlo G

2010-11-01

6

Selected Functionality Changes of ?-Lactoglobulin upon Esterification of Side-Chain Carboxyl Groups  

Microsoft Academic Search

Free carboxyl groups of bovine ~34actoglobulin were esterified with meth- anol, ethanol, and n-butanol. The modified proteins showed increased positive charge as the number of ionizable carboxyl groups was reduced. The methyl, ethyl, and butyl esters of ~-lactoglobulin showed enhanced surface activity, determined with surface and interfacial tension measurements at an air\\/water and oil\\/ water interface, respectively. The methyl ester

Margaret I. Halpin; T. Richardson

1985-01-01

7

Functional carboxyl groups in the red cell anion exchange protein. Modification with an impermeant carbodiimide  

PubMed Central

Anion exchange in human red blood cell membranes was inactivated using the impermeant carbodiimide 1-ethyl-3-(4-azonia-4,4-dimethylpentyl)- carbodiimide (EAC). The inactivation time course was biphasic: at 30 mM EAC, approximately 50% of the exchange capacity was inactivated within approximately 15 min; this was followed by a phase in which irreversible exchange inactivation was approximately 100-fold slower. The rate and extent of inactivation was enhanced in the presence of the nucleophile tyrosine ethyl ester (TEE), suggesting that the inactivation is the result of carboxyl group modification. Inactivation (to a maximum of 10% residual exchange activity) was also enhanced by the reversible inhibitor of anion exchange 4,4'-dinitrostilbene-2,2'- disulfonate (DNDS) at concentrations that were 10(3)-10(4) times higher than those necessary for inhibition of anion exchange. The extracellular binding site for stilbenedisulfonates is essentially intact after carbodiimide modification: the irreversible inhibitor of anion exchange 4,4'-diisothiocyanostilbene-2,2'-disulfonate (DIDS) eliminated (most of) the residual exchange activity: DNDS inhibited the residual (DIDS-sensitive) Cl- at concentrations similar to those that inhibit Cl- exchange of unmodified membranes: and Cl- efflux is activated by extracellular Cl-, with half-maximal activation at approximately 3 mM Cl-, which is similar to the value for unmodified membranes. But the residual anion exchange function after maximum inactivation is insensitive to changes of extra- and intracellular pH between pH 5 and 7. The titratable group with a pKa of approximately 5.4, which must be deprotonated for normal function of the native anion exchanger, thus appears to be lost after EAC modification.

1989-01-01

8

Carboxyl Group Reactivity in Actin.  

National Technical Information Service (NTIS)

While earlier work showed that the carboxyl groups of proteins could be quantitatively coupled to amino groups at pH 4.75 in the presence of EDC and a denaturing agent, the work presented here indicates that under milder conditions the modification of sid...

M. Elzinga

1986-01-01

9

Carboxyl group reactivity in actin  

SciTech Connect

While earlier work showed that the carboxyl groups of proteins could be quantitatively coupled to amino groups at pH 4.75 in the presence of EDC and a denaturing agent, the work presented here indicates that under milder conditions the modification of sidechain carboxyls is limited and somewhat specific. Most of the incorporated glycine ethyl ester (GEE) is apparently bound to five carboxyls. The total GEE incorporated was 3 to 4 moles/mole of protein as measured by an increase in Gly upon acid hydrolysis and amino acid analysis, as well as total radioactivity. 3.55 residues were found in peptides, 2.75 bound to residues 1 to 4, and 0.8 bound to Gly-100. 9 refs., 2 figs., 2 tabs.

Elzinga, M.

1986-01-01

10

Protein adsorption on colloidal alumina particles functionalized with amino, carboxyl, sulfonate and phosphate groups.  

PubMed

Colloidal oxide particles in biomedical or biotechnological applications immediately become coated with proteins of the biological medium, a process which is strongly influenced by the surface characteristics of the particles. Fundamental correlations between surface characteristics and the, so far mainly uncontrollable, protein adsorption are still not clear. In this study the surface of colloidal alumina particles (d(50)=179 ± 8 nm) was systematically adjusted with NH(2), COOH, SO(3)H and PO(3)H(2) functional groups to investigate the influence on the adsorption of the three model proteins, bovine serum albumin (BSA), lysozyme (LSZ) and trypsin (TRY). The surface functionalization is characterized and discussed in detail with regard to the morphology, isoelectric point, zeta potential, hydrophilic/hydrophobic properties, functional group density and stability. Protein-particle interaction was then assessed by evaluating the amount of protein adsorbed and the zeta potentials of protein-particle conjugates. Protein adsorption was found to be influenced by the type of functional group as well as the expected electrostatic forces under the given experimental conditions. The level of protein adsorption might, hence, be specifically controlled by the type of surface functionalization. Possible adsorption modes of BSA, LSZ and TRY on the particles are suggested by considering the spatial surface potential distribution of the proteins calculated from the protein database file. The particles presented provide an excellent prerequisite for further investigation of fundamental particle-protein interactions and the design of functionally graded materials for biomedical and biotechnological applications, e.g. as drug carriers or for protein purification. PMID:21963406

Meder, Fabian; Daberkow, Timo; Treccani, Laura; Wilhelm, Michaela; Schowalter, Marco; Rosenauer, Andreas; Mädler, Lutz; Rezwan, Kurosch

2011-09-18

11

In situ infrared study of SBA-15 functionalized with carboxylic groups incorporated by a co-condensation route.  

PubMed

Two samples of SBA-15 mesoporous silica with a different content of carboxylic groups (-COOH) were prepared by a co-condensation route, using 4-(triethoxysilil)butyronitrile as the organosilane agent, then treating the samples with sulfuric acid, which removes the template and simultaneously hydrolyses the -CN to -COOH groups, as shown by IR spectroscopy. Both incorporation of organosilane agents and subsequent acid treatment do not affect the ordered SBA-15 structure. The proton-donor ability of carboxylic groups, as well their accessibility to reactants, has been studied in the IR by dosing ammonia, which forms reversibly COO- groups and NH4+ ions. The related equilibrium constants have been determined by elaboration of IR data. Outgassing the samples at progressively increasing temperatures destabilizes to an increasing extent the ammonium/carboxylate ion pair, because of the decrease in surface polarity brought about by dehydration: this decreases the related equilibrium constants. The amount of carboxylic groups undergoing reaction appears instead to be constant with dehydration, and to coincide with the whole population of COOH groups. Titration with alkali solutions yielded surface concentrations for the two samples of ca. 1.0 and 0.45 COOH/nm2. Proportionality between the surface concentrations and the intensities of the C=O IR band is observed: this suggests that COOH groups are noninteracting with each other and allows the computation of the related extinction molar coefficient. PMID:16853129

Fiorilli, Sonia; Onida, Barbara; Bonelli, Barbara; Garrone, Edoardo

2005-09-01

12

Functionalization of cyclo-olefin polymer substrates by plasma oxidation: stable film containing carboxylic acid groups for capturing biorecognition elements.  

PubMed

Many current designs in biomedical diagnostics devices are based on the use of low cost, disposable, easy-to-fabricate chips made of plastic material, typically a cyclo-olefin polymer (COP). Low autofluorescence properties of such material, among others, make it ideal substrate for fluorescence-based applications. Functionalization of this plastic substrate for biomolecule attachment is therefore of great importance and the quality of films produced on such surface have often a significant influence on the performance of the device. In this communication we discuss the surface chemistry and some other characteristics of hydrophilic films, containing carboxylic acid functional groups, formed by plasma oxidation of COP and also films containing cross-linked, polymerized acryclic acid produced by sequential deposition of tetraorthosilicate and acrylic acid by plasma enhanced chemical vapor deposition (PECVD). Immobilization of labeled, single stranded DNA revealed high binding capacity for both coatings. To our best knowledge, this is the first example of direct immobilization of biomolecules on just plasma oxidized COP. Furthermore, more sophisticated treatment of the oxidized plastic substrate by PECVD with other organic precursors increased the binding capacity by some 40% than that of just plasma oxidized COP. The carboxy functionalized surfaces, due to the negative charge of the carboxy groups, showed very positive trends towards increasing the signal to noise ratio when charged biomolecules such as DNA, are used. PMID:20728322

Gubala, Vladimir; Le, Nam Cao Hoai; Gandhiraman, Ram Prasad; Coyle, Conor; Daniels, Stephen; Williams, David E

2010-08-03

13

New Chemistry with Old Functional Groups: On the Reaction of Isonitriles with Carboxylic Acids - A Route to Various Amide Types  

PubMed Central

Thermolysis of isonitriles with carboxylic acids provides, in one step, N-formyl imides (see, for example 8 + 19 ? 21). The resultant N-formyl group can be converted to N-H, NCH2OH or NCH3. This chemistry allows for a new route for synthesizing ?-N (asparagine) linked glycosyl amino acids.

Li, Xuechen; Danishefsky, Samuel J.

2008-01-01

14

Poly(3-hydroxyalkanoate)s Functionalized with Carboxylic Acid Groups in the Side Chain  

Microsoft Academic Search

Biodegradable polyesters represent an important class of materials, and one subset of these polymers are the bacterially produced poly(3-hydroxyalkanoate)s (PHA), a bacterially produced material. These polymers are very hydrophobic, and chemical methods to increase their hydrophilicity will ultimately lead to new applications. Many copolymers of PHA are known that contain simple, nonpolar functionality in the side chain, and we explored

Dannon J. Stigers; Gregory N. Tew

2003-01-01

15

Carboxyl group participation in sulfate and sulfamate group transfer reactions  

SciTech Connect

The pH dependence for the hydrolysis of N-(2-carboxyphenyl)sulfamic acid exhibits a plateau region corresponding to participation of the carboxyl function. A normal deuterium oxide solvent isotope effect indicates that proton transfer from the carboxylic acid is concerted with sulfamate group transfer to water. Hydrolysis of salicylic sulfate and N-(2-carboxyphenyl)sulfamate in /sup 18/O-enriched water yields salicylic acid and anthranilic acids with no enrichment, excluding catalysis by neighboring nucleophilic attack on sulfur by the carboxylate group. Intermolecular catalysis by carboxylic acids is demonstrated in the hydrolysis of N-(1-naphthyl)sulfamic acid; the mechanism is shown to involve preequilibrium protonation of the nitrogen followed by nucleophilic attack on sulfur by the carboxylate anion. Fast decomposition of the acyl sulfate completes the hydrolysis; this mechanism is considered to be the most efficient but is excluded in the intramolecular case which is constrained by the electronic requirements of displacement at the sulfur atom (6-ENDO-tet).

Hopkins, A.; Williams, A.

1982-04-23

16

Ozone-driven photochemical formation of carboxylic acid groups from alkane groups  

Microsoft Academic Search

Carboxylic acids are ubiquitous in atmospheric particles, and they play an important role in the physical and chemical properties of aerosol particles. During measurements in coastal California in the summer of 2009, carboxylic acid functional groups were highly associated with trajectories from an industrial region with high organic mass (OM), likely from fossil fuel combustion emissions. The concentration of carboxylic

S. Liu; D. A. Day; J. E. Shields; L. M. Russell

2011-01-01

17

Comparison of silatrane, phosphonic acid, and carboxylic acid functional groups for attachment of porphyrin sensitizers to TiO2 in photoelectrochemical cells.  

PubMed

A tetra-arylporphyrin dye was functionalized with three different anchoring groups used to attach molecules to metal oxide surfaces. The physical, photophysical and electrochemical properties of the derivatized porphyrins were studied, and the dyes were then linked to mesoporous TiO2. The anchoring groups were ?-vinyl groups bearing either a carboxylate, a phosphonate or a siloxy moiety. The siloxy linkages were made by treatment of the metal oxide with a silatrane derivative of the porphyrin. The surface binding and lability of the anchored molecules were studied, and dye performance was compared in a dye-sensitized solar cell (DSSC). Transient absorption spectroscopy was used to study charge recombination processes. At comparable surface concentration, the porphyrin showed comparable performance in the DSSC, regardless of the linker. However, the total surface coverage achievable with the carboxylate was about twice that obtainable with the other two linkers, and this led to higher current densities for the carboxylate DSSC. On the other hand, the carboxylate-linked dyes were readily leached from the metal oxide surface under alkaline conditions. The phosphonates were considerably less labile, and the siloxy-linked porphyrins were most resistant to leaching from the surface. The use of silatrane proved to be a practical and convenient way to introduce the siloxy linkages, which can confer greatly increased stability on dye-sensitized electrodes with photoelectrochemical performance comparable to that of the other linkers. PMID:23959453

Brennan, Bradley J; Llansola Portolés, Manuel J; Liddell, Paul A; Moore, Thomas A; Moore, Ana L; Gust, Devens

2013-08-20

18

Comparison of the holographic properties of DCG and polymer materials containing hydroxyl and/or carboxyl functional groups  

NASA Astrophysics Data System (ADS)

The optical properties of dichromated gelatin (DCG) as a material for volume holography are close to ideal. The material shows large refractive index modulation, high spatial resolution, negligible absorption, and low scattering. The inexpensive fabrication of large format HOEs is attained by automation of the entire process - film manufacturing, hologram copying, that the master hologram is extremely thin and consists of the holographic layer only. DCG layers, however, can not be easily lifted from the glass or plastic substratum. It is possible to achieve this objective by using other materials. As an alternative to gelatin we investigated the holographic properties of materials that contain hydroxyl, carboxyl or carbonyl groups. The investigated materials are: poly(vinyl alcohol) PVA, poly(acrylic acid) PAA and mixtures of these, such as PVA/PAA and chemically modified cPVA. The subject matter of this paper is the comprehensive presentation of the result of the experimental investigation of the holographic properties of the above introduced materials and their comparison to the properties of DCG holographic films. This comparison includes, but is not limited to the diffraction efficiency, grating strength and the transmission characteristics of the films.

Stojanoff, Christo G.; Froning, Philipp

1998-09-01

19

Ozone-driven daytime formation of secondary organic aerosol containing carboxylic acid groups and alkane groups  

Microsoft Academic Search

Carboxylic acids are present in substantial quantities in atmospheric particles, and they play an important role in the physical and chemical properties of aerosol particles. During measurements in coastal California in the summer of 2009, carboxylic acid functional groups were exclusively associated with a fossil fuel combustion factor derived from factor analysis of Fourier transform infrared spectroscopic measurements and closely

S. Liu; D. A. Day; J. E. Shields; L. M. Russell

2011-01-01

20

Alginate esters via chemoselective carboxyl group modification.  

PubMed

Alginates are (1?4) linked linear copolysaccharides composed of ?-d-mannuronic acid (M) and its C-5 epimer, ?-l-guluronic acid (G). Several strategies for synthesis of carboxyl modified alginate derivatives exist in the literature. Most of these however employ aqueous chemistries, such as carbodiimide coupling reactions. Based on our recently discovered method for homogeneous dissolution of tetrabutylammonium (TBA)-alginate, we now describe use of tetrabutylammonium fluoride (TBAF)-based two component solvent systems as media for synthesis of carboxyl-modified alginate esters. Partially and fully esterified benzyl, butyl, ethyl, and methyl alginates were synthesized via reaction with the corresponding alkyl halides. The newly synthesized derivatives were soluble in polar aprotic solvents without the addition of TBAF. Saponification was performed to demonstrate that alkylation was completely regioselective for carboxylate groups in preference to hydroxyl groups to form esters. We demonstrate the utility of these alginate esters to enhance aqueous solubility of the flavonoid naringenin by formation of solid dispersions. PMID:24053805

Pawar, Siddhesh N; Edgar, Kevin J

2013-08-13

21

Ozone-driven photochemical formation of carboxylic acid groups from alkane groups  

NASA Astrophysics Data System (ADS)

Carboxylic acids are ubiquitous in atmospheric particles, and they play an important role in the physical and chemical properties of aerosol particles. During measurements in coastal California in the summer of 2009, carboxylic acid functional groups were highly associated with trajectories from an industrial region with high organic mass (OM), likely from fossil fuel combustion emissions. The concentration of carboxylic acid groups peaked during daytime, suggesting a photochemical secondary formation mechanism. This daytime increase in concentration was tightly correlated with O3 mixing ratio, indicating O3 was the likely driver in acid formation. Based on the diurnal cycles of carboxylic acid and alkane groups, the covariation of carboxylic acid groups with O3, and the composition of the Combustion factor resulted from the factor analyses, gas-phase alkane oxidation by OH radicals to form dihyfrofuran followed by further oxidation of dihydrofuran by O3 is the likely acid formation mechanism. Using the multi-day average of the daytime increase of carboxylic acid group concentrations and m/z 44-based Aged Combustion factor, we estimated the lower-bound contributions of secondary organic aerosol (SOA) formed in 12-h daytime of processing in a single day to be 30% of the carboxylic acid groups and 25-45% of the Combustion factor concentration. These unique ambient observations of photochemically-driven acid formation suggest that gas-phase alkanes might be important sources of SOA formation in this coastal region.

Liu, S.; Day, D. A.; Shields, J. E.; Russell, L. M.

2011-03-01

22

Functionalization of cyclo-olefin polymer substrates by plasma oxidation: Stable film containing carboxylic acid groups for capturing biorecognition elements  

Microsoft Academic Search

Many current designs in biomedical diagnostics devices are based on the use of low cost, disposable, easy-to-fabricate chips made of plastic material, typically a cyclo-olefin polymer (COP). Low autofluorescence properties of such material, among others, make it ideal substrate for fluorescence-based applications. Functionalization of this plastic substrate for biomolecule attachment is therefore of great importance and the quality of films

Vladimir Gubala; Nam Cao Hoai Le; Ram Prasad Gandhiraman; Conor Coyle; Stephen Daniels; David E. Williams

2010-01-01

23

Differences in Cytocompatibility Between MWCNTs and Carboxylic Functionalized MWCNTs  

NASA Astrophysics Data System (ADS)

Influence of carboxylic functionalization on the cytocompatibility of multiwalled carbon nanotubes (MWCNTs) was investigated in this work. Water contact angle assay showed that the surface of MWCNTs-containing carboxyl (MWCNTs-COOH) became much more hydrophilic compared with pure MWCNTs. In cell-adhesion assays, two cell lines, mouse fibroblast cells (L929) and human umbilical vein endothelial cells (EAHY926) were used to assess the cytocompatibility of materials. The MWCNTs-COOH displayed the improved cell proliferation, viability and adhesion due to the enhanced wettability, indicating their superior cytocompatibility over MWCNTs. The existence of carboxyl groups should be benefit to the adhesion and growth of both cells, which implied that MWCNTs-COOH were helpful for seeding both cells and could be used as the functional surface for the adhesion and growth of cells.

Zhang, Yiteng; Li, Dejun; Zhao, Mengli; Guo, Meixian; Deng, Xiangyun; Gu, Hanqing; Wan, Rongxin

2013-02-01

24

Ozone-driven daytime formation of secondary organic aerosol containing carboxylic acid groups and alkane groups  

NASA Astrophysics Data System (ADS)

Carboxylic acids are present in substantial quantities in atmospheric particles, and they play an important role in the physical and chemical properties of aerosol particles. During measurements in coastal California in the summer of 2009, carboxylic acid functional groups were exclusively associated with a fossil fuel combustion factor derived from factor analysis of Fourier transform infrared spectroscopic measurements and closely correlated with oxygenated organic factors from aerosol mass spectrometry measurements. The high fraction of acid groups and the high ratio of oxygen to carbon in this factor suggest that this factor is composed of secondary organic aerosol (SOA) products of combustion emissions from the upwind industrial region (the ports of Los Angeles and Long Beach). Another indication of the photochemically-driven secondary formation of this combustion-emitted organic mass (OM) was the daytime increase in the concentrations of acid groups and the combustion factors. This daytime increase closely tracked the O3 mixing ratio with a correlation coefficient of 0.7, indicating O3 was closely associated with the SOA maximum and thus likely the oxidant that resulted in acid group formation. Using a pseudo-Lagrangian framework to interpret this daytime increase of carboxylic acid groups and the combustion factors, we estimate that the carboxylic acid groups formed in a 12-h daytime period of one day ("Today's SOA") accounted for 25-33 % of the measured carboxylic acid group mass, while the remaining 67-75 % (of the carboxylic acid group mass) was likely formed 1-3 days previously (the "Background SOA"). A similar estimate of the daytime increase in the combustion factors suggests that "Today's SOA" and the "Background SOA" respectively contributed 25-50 % and 50-75 % of the combustion factor (the "Total SOA"), for a "Total SOA" contribution to the OM of 60 % for the project average. Further, size-resolved spectrometric and spectroscopic characterization of the particle OM indicate that the majority of the OM formed by condensation of gas-phase oxidation products. This unique set of measurements and methods to quantify and characterize photochemically and ozone-linked carboxylic acid group formation provide independent and consistent assessments of the secondary fraction of OM, which could result from second generation products of the oxidation of gas-phase alkane (molecules).

Liu, S.; Day, D. A.; Shields, J. E.; Russell, L. M.

2011-08-01

25

Decarboxylation via addition of water to a carboxyl group: acid catalysis of pyrrole-2-carboxylic acid.  

PubMed

The decarboxylation of pyrrole-2-carboxylic acid is subject to acid catalysis in strongly acidic solutions. Protonation of the pyrrole ring at C2 produces a potentially low-energy carbanion leaving group. Carbon dioxide formation is suppressed by the requisite formation of its high-energy conjugate acid. As a result, decarboxylation must proceed via an associative mechanism through the addition of water to the carboxyl group of the protonated reactant, leading to the formation of pyrrole and protonated carbonic acid, which rapidly dissociates into H(3)O(+) and carbon dioxide. PMID:19645466

Mundle, Scott O C; Kluger, Ronald

2009-08-26

26

Soluble, High Molecular Weight Polysilsesquioxanes with Carboxylate Functionalities  

SciTech Connect

Trialkoxysilyl-containing monomers of the type (RO){sub 3}Si(CH{sub 2}){sub 3}C(O)OtBu (R = Me, Et) were prepared by hydrosilation of the corresponding vinylic tert-butyl esters CH{sub 3}CHCH{sub 2}C(O)OtBu. Acid- or base-catalyzed polymerization of the monomers leads to very high molecular weight polymers with relatively narrow polydispersities. The polymerization results in complete condensation of the alkoxy groups while the tert-butyl ester functionality remains fully intact. Partial or full deprotection of the tert-butyl group can easily be achieved to yield the corresponding carboxylic acid polymers. The ester and carboxylic acid functionalities of these new materials allow for their potential use in a variety of applications such as scavenging of heavy metals.

RAHIMIAN,KAMYAR; LOY,DOUGLAS A.; WHEELER,DAVID R.

2000-07-14

27

IDENTIFICATION AND QUANTIFICATION OF AEROSOL POLAR OXYGENATED COMPOUNDS BEARING CARBOXYLIC AND/OR HYDROXYL GROUPS. 1. METHOD DEVELOPMENT  

EPA Science Inventory

In this study, a new analytical technique was developed for the identification and quantification of multi-functional compounds containing simultaneously at least one hydroxyl or one carboxylic group, or both. This technique is based on derivatizing first the carboxylic group(s) ...

28

Carboxyl Methylation of Small GTPases and Endothelial Cell Function  

Microsoft Academic Search

Posttranslational modifications of small GTPases regulate enzyme activity and subcellular localization, resulting in altered\\u000a cellular functions. The role of small-GTPase carboxyl methylation in modulating endothelial functions is not well understood.\\u000a In our study, we have used cultured endothelial cells to assess the effects of inhibition of carboxyl methylation on endothelial\\u000a cell function. We have found that isoprenylcysteine carboxyl methyltransferase (ICMT)

Sharon Rounds; Elizabeth O. Harrington; Qing Lu

29

Functional group induced excited state intramolecular proton transfer process in 4-amino-2-methylsulfanyl-pyrimidine-5-carboxylic acid ethyl ester: a combined spectroscopic and density functional theory study.  

PubMed

The molecule methyl-2-aminonicotinate (2-MAN) does not exhibit excited state intramolecular proton transfer (ESIPT), but its derivative 4-amino-2-methylsulfanyl-pyrimidine-5-carboxylic acid ethyl ester (AMPCE), widely used in the preparation of pyrimidopyrimidines as a protein kinase inhibitor, does exhibit ESIPT. Increasing acidic and basic character at the proton donor and proton acceptor sites by adding functional groups is found to be responsible for the large Stokes shifted ESIPT emission (?? = 12?706 cm(-1)) in AMPCE. The photophysics of AMPCE have been explored on the basis of steady state and time resolved spectral measurements, quantum yield calculation with variation of polarity, as well as hydrogen bonding ability of solvents. Experimental findings have been correlated with the calculated structure and potential energy surfaces based on the intramolecular proton transfer model obtained by density functional theory (DFT). Properties based on the calculated excited state surfaces generated in vacuo and methanol solvent using time dependent density functional theory (TDDFT) and time dependent density functional theory polarized continuum model (TDDFT-PCM), respectively, show good agreement with the experimental findings. HOMO and LUMO diagrams also support the favorable ESIPT process in the first excited state potential energy surface. PMID:23719759

Jana, Sankar; Dalapati, Sasanka; Guchhait, Nikhil

2013-08-14

30

Influence of carboxyl group on the acid hydrolysis of cellulose  

Microsoft Academic Search

Cellulose isolated from wood is more susceptible than cotton cellulose to homogeneous hydrolysis in phosphoric acid. The influence\\u000a of carboxyl group introduction at the C6 position on the hydrolysis rate of cellulose in 82.5% phosphoric acid was studied\\u000a as a model of the oxidation of cellulose during pulping. The rate constant of hydrolysis for dissolving pulp was larger than\\u000a that

Shuichi Hirosawa; Kazuya Minato; Fumiaki Nakatsubo

2001-01-01

31

Improved antifouling properties of polyamide nanofiltration membranes by reducing the density of surface carboxyl groups.  

PubMed

Carboxyls are inherent functional groups of thin-film composite polyamide nanofiltration (NF) membranes, which may play a role in membrane performance and fouling. Their surface presence is attributed to incomplete reaction of acyl chloride monomers during the membrane active layer synthesis by interfacial polymerization. In order to unravel the effect of carboxyl group density on organic fouling, NF membranes were fabricated by reacting piperazine (PIP) with either isophthaloyl chloride (IPC) or the more commonly used trimesoyl chloride (TMC). Fouling experiments were conducted with alginate as a model hydrophilic organic foulant in a solution, simulating the composition of municipal secondary effluent. Improved antifouling properties were observed for the IPC membrane, which exhibited lower flux decline (40%) and significantly greater fouling reversibility or cleaning efficiency (74%) than the TMC membrane (51% flux decline and 40% cleaning efficiency). Surface characterization revealed that there was a substantial difference in the density of surface carboxyl groups between the IPC and TMC membranes, while other surface properties were comparable. The role of carboxyl groups was elucidated by measurements of foulant-surface intermolecular forces by atomic force microscopy, which showed lower adhesion forces and rupture distances for the IPC membrane compared to TMC membranes in the presence of calcium ions in solution. Our results demonstrated that a decrease in surface carboxyl group density of polyamide membranes fabricated with IPC monomers can prevent calcium bridging with alginate and, thus, improve membrane antifouling properties. PMID:23205860

Mo, Yinghui; Tiraferri, Alberto; Yip, Ngai Yin; Adout, Atar; Huang, Xia; Elimelech, Menachem

2012-12-03

32

Measurement of functionalised carbon nanotube carboxylic acid groups using a simple chemical process  

Microsoft Academic Search

Chemically functionalised single-walled carbon nanotubes were formed using sonication in a mixture of concentrated sulphuric and nitric acids for varying lengths of time which resulted in carboxylic acid group functionalisation, predominantly at the ends. The carboxylic acid groups were used to form an ionic bond with dodecylamine. The weight of this complex was used to monitor the number of carboxylic

Matthew W. Marshall; Simina Popa-Nita; Joseph G. Shapter

2006-01-01

33

Chondrocyte behaviors on poly- l-lactic acid (PLLA) membranes containing hydroxyl, amide or carboxyl groups  

Microsoft Academic Search

Hydrophilic groups, i.e. hydroxyl (–OH), carboxyl (–COOH) or amide (–CONH2) were introduced onto the poly-l-lactic acid (PLLA) membrane surfaces via the photo-induced grafting copolymerization of the corresponding monomers, i.e. hydroxyethyl methacrylate, methacrylic acid or acrylamide, respectively. Chondrocyte culture was used to study the correlation between the cell behaviors and the hydrophilic functional groups. The results showed that the cytocompatibility of

Zuwei Ma; Changyou Gao; Yihong Gong; Jiacong Shen

2003-01-01

34

The hydroxyl group of S685 in Walker A motif and the carboxyl group of D792 in Walker B motif of NBD1 play a crucial role for multidrug resistance protein folding and function  

PubMed Central

Structural analysis of MRP1-NBD1 revealed that the Walker A S685 forms hydrogen-bond with the Walker B D792 and interacts with magnesium and the ?-phosphate of the bound ATP. We have found that substitution of the D792 with leucine resulted in misfolding of the protein. In this report we tested whether substitution of the S685 with residues that prevent formation of this hydrogen-bond would also cause misfolding. Indeed, substitution of the S685 with residues potentially preventing formation of this hydrogen-bond resulted in misfolding of the protein. In addition, some substitutions that might form hydrogen-bond with D792 also yielded immature protein. All these mutants are temperature-sensitive variants. However, these complex-glycosylated mature mutants prepared from the cells grown at 27 °C still significantly affect ATP binding and ATP-dependent solute transport. In contrast, substitution of the S685 with threonine yielded complex-glycosylated mature protein that is more active than the wild-type MRP1, indicating that the interaction between the hydroxyl group of 685 residue and the carboxyl group of D792 plays a crucial role for the protein folding and the interactions of the hydroxyl group at 685 with magnesium and the ?-phosphate of the bound ATP play an important role for ATP-binding and ATP-dependent solute transport.

Yang, Runying; Scavetta, Robert; Chang, Xiu-bao

2010-01-01

35

Functionalized carboxyl nanoparticles enhance mucus dispersion and hydration  

NASA Astrophysics Data System (ADS)

Luminal accumulation of viscous, poorly hydrated, and less transportable mucus has been associated with altered mucus rheology and reduced mucociliary clearance. These symptoms are some of the cardinal clinical manifestations found throughout major respiratory diseases as well as gastrointestinal and digestive disorders. Applications of current mucolytics may yield short-term improvements but are continuously challenged by undesirable side-effects. While nanoparticles (NPs) can interact with mucin polymers, whether functionalized NPs can rectify mucus rheology is unknown. Herein, we report that carboxyl-functionalized NPs (24 nm and 120 nm) dramatically reduced mucin gel size and accelerated mucin matrix hydration rate (diffusivity). Our results suggest that carboxyl-functionalized NPs disperse mucin gels possibly by enhancing network hydration. This report highlights the prospective usages of carboxyl-functionalized NPs as a novel mucus dispersant or mucolytic agent in adjusting mucus rheological properties and improving mucociliary transport to relieve clinical symptoms of patients suffering from relevant diseases.

Chen, Eric Y.; Daley, David; Wang, Yung-Chen; Garnica, Maria; Chen, Chi-Shuo; Chin, Wei-Chun

2012-01-01

36

Bichromophoric fluorescent photolabile protecting group for alcohols and carboxylic acids.  

PubMed

Novel bichromophoric fluorescent photolabile protecting group, (5-dansyloxy-3-hydroxynaphthalen-2-yl)methyl (DNS-NQMP), allows for the independent photochemical release and fluorescent imaging of caged substrates. Irradiation of DNS-NQMP-caged alcohols and carboxylic acids with 300 or 350 nm light results in fast (k(release) ~ 10(5) s(-1)), efficient (? = 0.2), and quantitative release of the substrates. This uncaging chemistry is compatible with aqueous media and DNS-NQMP-protected hydroxy compounds are hydrolytically stable at neutral pH. Upon excitation with 400 nm light, caged compounds show intense green emission (?(max) = 559 nm) with 21% fluorescence quantum yield. Fluorescent readout conducted using 400 nm or longer wavelengths does not cause substrate release. The DNS-NQMP chromophore retains its fluorescent properties after photo-uncaging reaction. PMID:22186939

Arumugam, Selvanathan; Popik, Vladimir V

2011-12-21

37

Roles of carboxyl groups in the transmembrane insertion of peptides  

PubMed Central

We have used the pHLIP® peptide to study the roles of carboxyl groups in transmembrane peptide insertion. The pH (low) insertion peptide (pHLIP) binds to the surface of a lipid bilayer as a disordered peptide at neutral pH, and when the pH is lowered it inserts across the membrane to form a transmembrane helix. Peptide insertion is reversed when the pH is raised above the characteristic pKa (6.0). A key event facilitating the membrane insertion is the protonation of aspartic (Asp) and/or glutamic (Glu) acid residues, since at neutral pH their negatively charged side chains hinder membrane insertion. In order to gain mechanistic understanding, we studied the membrane insertion and exit of a series of pHLIP variants where the four Asp residues were sequentially mutated to nonacidic residues, including histidine (His). Our results show that the presence of His residues does not prevent the pH-dependent peptide membrane insertion at ~pH 4 driven by the protonation of carboxyl groups at the inserting end of the peptide. A further pH drop leads to the protonation of His residues in the TM part of peptide, which induces peptide exit from the bilayer. We also find that the number of ionizable residues that undergo a change in protonation during membrane insertion correlates with the pH-dependent insertion into and exit from the lipid bilayer, and that cooperativity increases with their number. We expect that our understanding will be used to improve the targeting of acidic diseased tissue by pHLIP peptides.

Barrera, Francisco N.; Weerakkody, Dhammika; Anderson, Michael; Andreev, Oleg A.; Reshetnyak, Yana K.; Engelman, Donald M.

2011-01-01

38

Roles of carboxyl groups in the transmembrane insertion of peptides.  

PubMed

We have used pHLIP® [pH (low) insertion peptide] to study the roles of carboxyl groups in transmembrane (TM) peptide insertion. pHLIP binds to the surface of a lipid bilayer as a disordered peptide at neutral pH; when the pH is lowered, it inserts across the membrane to form a TM helix. Peptide insertion is reversed when the pH is raised above the characteristic pK(a) (6.0). A key event that facilitates membrane insertion is the protonation of aspartic acid (Asp) and/or glutamic acid (Glu) residues, since their negatively charged side chains hinder membrane insertion at neutral pH. In order to gain mechanistic understanding, we studied the membrane insertion and exit of a series of pHLIP variants where the four Asp residues were sequentially mutated to nonacidic residues, including histidine (His). Our results show that the presence of His residues does not prevent the pH-dependent peptide membrane insertion at ~pH 4 driven by the protonation of carboxyl groups at the inserting end of the peptide. A further pH drop leads to the protonation of His residues in the TM part of the peptide, which induces peptide exit from the bilayer. We also find that the number of ionizable residues that undergo a change in protonation during membrane insertion correlates with the pH-dependent insertion into the lipid bilayer and exit from the lipid bilayer, and that cooperativity increases with their number. We expect that our understanding will be used to improve the targeting of acidic diseased tissue by pHLIP. PMID:21888917

Barrera, Francisco N; Weerakkody, Dhammika; Anderson, Michael; Andreev, Oleg A; Reshetnyak, Yana K; Engelman, Donald M

2011-08-23

39

SYNTHESIS OF NOVEL HYDROPHILIC POLY(ESTER-CARBONATES) CONTAINING PENDENT CARBOXYLIC ACID GROUPS  

Microsoft Academic Search

A functional cyclic carbonate, 5-methyl-5-benzyloxycarbonyl-1,3-dioxan-2-one (MBC), was utilized in the synthesis of novel poly(ester-carbonates) containing pendent carboxylic acid groups. Copolymers with ?-caprolactone (CL) and L-lactide (LLA) were synthesized by ring-opening polymerization (ROP) using either an Al-alkoxide (solution) or Sn(Oct)2-alcohol (bulk) initiating system. Analysis of the copolymers revealed a random distribution of the comonomer units along the polymer chain. The copolymers

Robson F. Storey; Brian D. Mullen; Kim M. Melchert

2001-01-01

40

New and extended parameterization of the thermodynamic model AIOMFAC: calculation of activity coefficients for organic-inorganic mixtures containing carboxyl, hydroxyl, carbonyl, ether, ester, alkenyl, alkyl, and aromatic functional groups  

NASA Astrophysics Data System (ADS)

We present a new and considerably extended parameterization of the thermodynamic activity coefficient model AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) at room temperature. AIOMFAC combines a Pitzer-like electrolyte solution model with a UNIFAC-based group-contribution approach and explicitly accounts for interactions between organic functional groups and inorganic ions. Such interactions constitute the salt-effect, may cause liquid-liquid phase separation, and affect the gas-particle partitioning of aerosols. The previous AIOMFAC version was parameterized for alkyl and hydroxyl functional groups of alcohols and polyols. With the goal to describe a wide variety of organic compounds found in atmospheric aerosols, we extend here the parameterization of AIOMFAC to include the functional groups carboxyl, hydroxyl, ketone, aldehyde, ether, ester, alkenyl, alkyl, aromatic carbon-alcohol, and aromatic hydrocarbon. Thermodynamic equilibrium data of organic-inorganic systems from the literature are critically assessed and complemented with new measurements to establish a comprehensive database. The database is used to determine simultaneously the AIOMFAC parameters describing interactions of organic functional groups with the ions H+, Li+, Na+, K+, NH4+, Mg2+, Ca2+, Cl-, Br-, NO3-, HSO4-, and SO42-. Detailed descriptions of different types of thermodynamic data, such as vapor-liquid, solid-liquid, and liquid-liquid equilibria, and their use for the model parameterization are provided. Issues regarding deficiencies of the database, types and uncertainties of experimental data, and limitations of the model, are discussed. The challenging parameter optimization problem is solved with a novel combination of powerful global minimization algorithms. A number of exemplary calculations for systems containing atmospherically relevant aerosol components are shown. Amongst others, we discuss aqueous mixtures of ammonium sulfate with dicarboxylic acids and with levoglucosan. Overall, the new parameterization of AIOMFAC agrees well with a large number of experimental datasets. However, due to various reasons, for certain mixtures important deviations can occur. The new parameterization makes AIOMFAC a versatile thermodynamic tool. It enables the calculation of activity coefficients of thousands of different organic compounds in organic-inorganic mixtures of numerous components. Models based on AIOMFAC can be used to compute deliquescence relative humidities, liquid-liquid phase separations, and gas-particle partitioning of multicomponent mixtures of relevance for atmospheric chemistry or in other scientific fields.

Zuend, A.; Marcolli, C.; Booth, A. M.; Lienhard, D. M.; Soonsin, V.; Krieger, U. K.; Topping, D. O.; McFiggans, G.; Peter, T.; Seinfeld, J. H.

2011-09-01

41

New and extended parameterization of the thermodynamic model AIOMFAC: calculation of activity coefficients for organic-inorganic mixtures containing carboxyl, hydroxyl, carbonyl, ether, ester, alkenyl, alkyl, and aromatic functional groups  

NASA Astrophysics Data System (ADS)

We present a new and considerably extended parameterization of the thermodynamic activity coefficient model AIOMFAC (Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients) at room temperature. AIOMFAC combines a Pitzer-like electrolyte solution model with a UNIFAC-based group-contribution approach and explicitly accounts for interactions between organic functional groups and inorganic ions. Such interactions constitute the salt-effect, may cause liquid-liquid phase separation, and affect the gas-particle partitioning of aerosols. The previous AIOMFAC version was parameterized for alkyl and hydroxyl functional groups of alcohols and polyols. With the goal to describe a wide variety of organic compounds found in atmospheric aerosols, we extend here the parameterization of AIOMFAC to include the functional groups carboxyl, hydroxyl, ketone, aldehyde, ether, ester, alkenyl, alkyl, aromatic carbon-alcohol, and aromatic hydrocarbon. Thermodynamic equilibrium data of organic-inorganic systems from the literature are critically assessed and complemented with new measurements to establish a comprehensive database. The database is used to determine simultaneously the AIOMFAC parameters describing interactions of organic functional groups with the ions H+, Li+, Na+, K+, NH4+, Mg2+, Ca2+, Cl-, Br-, NO3-, HSO4-, and SO42-. Detailed descriptions of different types of thermodynamic data, such as vapor-liquid, solid-liquid, and liquid-liquid equilibria, and their use for the model parameterization are provided. Issues regarding deficiencies of the database, types and uncertainties of experimental data, and limitations of the model, are discussed. The challenging parameter optimization problem is solved with a novel combination of powerful global minimization algorithms. A number of exemplary calculations for systems containing atmospherically relevant aerosol components are shown. Amongst others, we discuss aqueous mixtures of ammonium sulfate with dicarboxylic acids and with levoglucosan. Overall, the new parameterization of AIOMFAC agrees well with a large number of experimental datasets. However, due to various reasons, for certain mixtures important deviations can occur. The new parameterization makes AIOMFAC a versatile thermodynamic tool. It enables the calculation of activity coefficients of thousands of different organic compounds in organic-inorganic mixtures of numerous components. Models based on AIOMFAC can be used to compute deliquescence relative humidities, liquid-liquid phase separations, and gas-particle partitioning of multicomponent mixtures of relevance for atmospheric chemistry or in other scientific fields.

Zuend, A.; Marcolli, C.; Booth, A. M.; Lienhard, D. M.; Soonsin, V.; Krieger, U. K.; Topping, D. O.; McFiggans, G.; Peter, T.; Seinfeld, J. H.

2011-05-01

42

Synthesis, characterization and structures of copper(II) complexes containing carboxylate and sulfonate groups  

Microsoft Academic Search

Four copper(II) complexes containing Schiff base and reduced Schiff base ligands derived from pyridine-2-aldehyde and amino\\u000a acid containing carboxylate and sulfonate functional groups (N-(2-pyridylmethylene)-amino acid and N-(2-pyridylmethyl)-amino acid, (amino acids = ?-alanine and aminoethanesulfonic acid) namely, [Cu(Pbals)(H2O)2]ClO4·H2O 1, [Cu(Pbal)(ClO4)(H2O)] 2, [Cu2(Paes)2(ClO4)2]·2H2O 3, and [Cu(Pae)(H2O)]·ClO4·H2O 4 have been synthesized and characterized. The structural features of carboxylate and sulfonate donor groups have been elucidated.

Wei Lee Leong; Jagadese J. Vittal

43

Arginine of retinoic acid receptor ? which coordinates with the carboxyl group of retinoic acid functions independent of the amino acid residues responsible for retinoic acid receptor subtype ligand specificity  

Microsoft Academic Search

The biological actions of retinoic acid (RA) are mediated by retinoic acid receptors (RAR?, RAR?, and RAR?) and retinoid X receptors (RXR?, RXR?, and RXR?). Consistent with the X-ray crystal structures of RAR? and RAR?, site-directed mutagenesis studies have demonstrated the importance of a conserved Arg residue (?Arg276, ?Arg269, and ?Arg278) for coordination with the carboxyl group of RA. However,

Zeng-Ping Zhang; Juliet M Hutcheson; Helen C Poynton; Jerome L Gabriel; Kenneth J Soprano; Dianne Robert Soprano

2003-01-01

44

Membrane fusion activity of succinylated melittin is triggered by protonation of its carboxyl groups.  

PubMed

The membrane fusion activity of melittin and its succinylated derivative was studied as a function of pH by the transfer of spin-labeled phosphatidylcholine as well as by internal content mixing and electron microscopy. The protonation process of the carboxyl groups introduced into melittin was studied by 13C NMR spectroscopy using derivative prepared with [1,4(-13)C]succinic anhydride. Melittin causes fusion of sonicated phosphatidylcholine vesicles in a wide range of pH. In marked contrast, melittin with all four amino groups succinylated induces fusion only at acidic pH lower than 5.2, with the maximum at pH 5.1. The fusion reactions are very rapid, reaching a saturation level within 1 min. The fusion efficiency depends on the peptide-to-phospholipid ratio in the reaction mixture. Trypsinized succinylated melittin, which has lost the four positively charged C-terminal residues, causes aggregation of vesicles at acidic pH but cannot induce fusion. The 13C NMR peaks for the carboxyl and carbonyl groups of succinylated melittin shifted to higher field as the pH was lowered. The pKa value of the four carboxyl groups was obtained as 5.19 and 4.83 in the presence and absence of vesicles, respectively. The pKa value in the presence of vesicles agrees quite well with the half-maximal pH for fusion of 5.15, indicating that the fusion activity is triggered by protonation of the carboxyl groups in the hydrophobic segment of the peptide. The higher shift of pKa value in the presence of vesicles can be due to stabilization of the protonated form by entrance into lipid bilayer hydrocarbon layer.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2820482

Murata, M; Nagayama, K; Ohnishi, S

1987-06-30

45

Strong-acid, carboxyl-group structures in fulvic acid from the Suwannee River, Georgia. 1. Minor structures  

USGS Publications Warehouse

An investigation of the strong-acid characteristics (pKa 3.0 or less) of fulvic acid from the Suwannee River, Georgia, was conducted. Quantitative determinations were made for amino acid and sulfur-containing acid structures, oxalate half-ester structures, malonic acid structures, keto acid structures, and aromatic carboxyl-group structures. These determinations were made by using a variety of spectrometric (13C-nuclear magnetic resonance, infrared, and ultraviolet spectrometry) and titrimetric characterizations on fulvic acid or fulvic acid samples that were chemically derivatized to indicate certain functional groups. Only keto acid and aromatic carboxyl-group structures contributed significantly to the strong-acid characteristics of the fulvic acid; these structures accounted for 43% of the strong-acid acidity. The remaining 57% of the strong acids are aliphatic carboxyl groups in unusual and/or complex configurations for which limited model compound data are available.

Leenheer, J. A.; Wershaw, R. L.; Reddy, M. M.

1995-01-01

46

Structural environments of carboxyl groups in natural organic molecules from terrestrial systems. Part 2: 2D NMR spectroscopy  

NASA Astrophysics Data System (ADS)

Carboxyl groups are abundant in natural organic molecules (NOM) and play a major role in their reactivity. The structural environments of carboxyl groups in IHSS soil and river humic samples were investigated using 2D NMR (heteronuclear and homonuclear correlation) spectroscopy. Based on the 1H- 13C heteronuclear multiple-bond correlation (HMBC) spectroscopy results, the carboxyl environments in NOM were categorized as Type I (unsubstituted and alkyl-substituted aliphatic/alicyclic), Type II (functionalized carbon substituted), Type IIIa, b (heteroatom and olefin substituted), and Type IVa, b (5-membered heterocyclic aromatic and 6-membered aromatic). The most intense signal in the HMBC spectra comes from the Type I carboxyl groups, including the 2JCH and 3JCH couplings of unsubstituted aliphatic and alicyclic acids, though this spectral region also includes the 3JCH couplings of Type II and III structures. Type II and III carboxyls have small but detectable 2JCH correlations in all NOM samples except for the Suwannee River humic acid. Signals from carboxyls bonded to 5-membered aromatic heterocyclic fragments (Type IVa) are observed in the soil HA and Suwannee River FA, while correlations to 6-membered aromatics (Type IVb) are only observed in Suwannee River HA. In general, aromatic carboxylic acids may be present at concentrations lower than previously imagined in these samples. Vibrational spectroscopy results for these NOM samples, described in an accompanying paper [Hay M. B. and Myneni S. C. B. (2007) Structural environments of carboxyl groups in natural organic molecules from terrestrial systems. Part 1: Infrared spectroscopy. Geochim. Cosmochim. Acta (in press)], suggest that Type II and Type III carboxylic acids with ? substituents (e.g., -OH, -OR, or -CO 2H) constitute the majority of carboxyl structures in all humic substances examined. Furoic and salicylic acid structures (Type IV) are also feasible fragments, albeit as minor constituents. The vibrational spectroscopy results also suggest that much of the "Type I" signal observed in the HMBC spectrum is due to carboxylic acid esters and possibly ?-substituted alicyclic acids.

Deshmukh, Ashish P.; Pacheco, Carlos; Hay, Michael B.; Myneni, Satish C. B.

2007-07-01

47

Chitosan with phosphonic and carboxylic group: New multidentate ligands  

Microsoft Academic Search

Chemical modifications of polysaccharides are increasingly studied and they have potential providing new applications. N-methylene phosphonic N-methylene carboxylic chitosan was obtained in water soluble form using N-methylene phosphonic chitosan and glyoxylic acid (via aldimine formation) under reduction conditions with sodium borohydride. The modified chitosan was characterized by 1 H NMR, 13 C NMR and FTIR spectroscopy. A practical simple and

Viviana M. Ramos; María Susana Rodríguez; Enrique Agulló; Nora M. Rodríguez; Angeles Heras

2002-01-01

48

Synthesis and Characterization of New Functional Polyelectrolytes Based on Carboxyl Containing Methacrylates  

Microsoft Academic Search

Three new methacrylic monomers, 6-methacryloyloxyhexanoic acid, 6-(N-methacryloyl)aminohexanoic acid, and ethyl 6-(N-methacryloyl)-aminohexanoate, containing carboxyl groups spaced from the polymerizable double bond by a polymethylene chain, have been synthesized. Multifunctional polymeric materials were obtained by radical polymerization of these monomers with different vinyl monomers. The type and content of the functional groups was modulated on the basis of feed composition and the

Nicoletta Tamburro; Federica Chiellini; Roberto Solaro

2001-01-01

49

Role of the carboxylic group in the antispasmodic and vasorelaxant action displayed by kaurenoic acid.  

PubMed

The present work describes the investigation of the role of the carboxylic group in the structure-activity relationship of the diterpene ent-kaur-16-en-19-oic acid (kaurenoic acid, KA) in inhibiting rat aorta contraction. For this purpose the methylation of the C-19 carboxyl group of KA was carried out. The effects of the obtained ent-methyl-kaur-16-en-19-oate (KAMe) were compared with those induced by KA. Vascular reactivity experiments showed that KA (50 and 100 microM) concentration-dependently inhibited KCl-induced contraction in both endothelium-intact and denuded rat aortic rings. On the other hand, KAMe attenuated KCl-induced contraction at 100 microM, but not at 50 microM. KA also reduced CaCl(2)-induced contraction in Ca(2+)-free solution containing KCl (30 mM). Again, KAMe produced a less accentuated reduction in CaCl(2)-induced contraction than that induced by the acid KA. KAMe (1-450 microM) concentration-dependently relaxed KCl-pre-contracted rings (percentages of relaxation 82.57 +/- 1.65 and 70.55 +/- 4.71, respectively) with denuded endothelium. Similarly, the relaxation induced by KA on phenylephrine (Phe)-pre-contracted rings (73.06 +/- 3.68%) was more pronounced than that found for KAMe (53.68 +/- 4.75%). Pre-incubation of denuded rings for different periods with KA and KAMe showed that the equilibrium periods required by each compound to achieve its maximal inhibitory response on KCl-induced contraction are different. Collectively, our results provide functional evidence that methylation of the C-19 carboxyl group of KA reduces but does not abolish the antispasmodic activity displayed by KA. Additionally, we showed that the equilibrium period is a critical step for the inhibitory effect displayed by kaurane-type diterpenes. PMID:15525447

Ambrosio, Sergio R; Tirapelli, Carlos R; Coutinho, Silvia T; de Oliveira, Dionéia C R; de Oliveira, Ana M; Da Costa, Fernando B

2004-11-01

50

Biomimetic nucleation and growth of CaCO3 in hydrogels incorporating carboxylate groups.  

PubMed

Poly-acrylamide hydrogels were modified by copolymerization with acrylic acid and used as growth medium for CaCO3 in a double-diffusion arrangement. The carboxylate functionalities in the gel network facilitate the nucleation of a multitude of small crystallites of vaterite and calcite, which are temporarily stabilized even while supersaturation is increasing within the hydrogel. After an extended induction period the rapid spherulitic growth of calcite crystals along their c-axis is observed yielding spheres with diameters exceeding 300 microm. In the center of those aggregates disordered, porous regions can be identified as starting point of this rapid crystallization. The results are compared to previous studies on native poly-acrylamide hydrogels and networks modified with -SO(3)H functional groups. The mineralization mechanism is significantly altered by specific interactions between the -COOH functionalized network and the evolving mineral phase. PMID:14585715

Grassmann, Olaf; Löbmann, Peer

2004-01-01

51

Functionalized carbon nanotubes containing isocyanate groups  

Microsoft Academic Search

Functionalized carbon nanotubes containing isocyanate groups can extend the nanotube chemistry, and may promote their many potential applications such as in polymer composites and coatings. This paper describes a facile method to prepare functionalized carbon nanotubes containing highly reactive isocyanate groups on its surface via the reaction between toluene 2,4-diisocyanate and carboxylated carbon nanotubes. Fourier-transformed infrared spectroscopy (FTIR) and X-ray

Chungui Zhao; Lijun Ji; Huiju Liu; Guangjun Hu; Shimin Zhang; Mingshu Yang; Zhenzhong Yang

2004-01-01

52

Measuring the concentration of carboxylic acid groups in torrefied spruce wood.  

PubMed

Torrefaction is moderate thermal treatment (?200-300°C) to improve the energy density, handling and storage properties of biomass fuels. In biomass, carboxylic sites are partially responsible for its hygroscopic. These sites are degraded to varying extents during torrefaction. In this paper, we apply methylene blue sorption and potentiometric titration to measure the concentration of carboxylic acid groups in spruce wood torrefied for 30min at temperatures between 180 and 300°C. The results from both methods were applicable and the values agreed well. A decrease in the equilibrium moisture content at different humidity was also measured for the torrefied wood samples, which is in good agreement with the decrease in carboxylic acid sites. Thus both methods offer a means of directly measuring the decomposition of carboxylic groups in biomass during torrefaction as a valuable parameter in evaluating the extent of torrefaction which provides new information to the chemical changes occurring during torrefaction. PMID:22940339

Khazraie Shoulaifar, Tooran; Demartini, Nikolai; Ivaska, Ari; Fardim, Pedro; Hupa, Mikko

2012-07-27

53

Amino and carboxyl plasma functionalization of collagen films for tissue engineering applications.  

PubMed

Type I collagen films have been functionalized on their surfaces by plasma treatment with carboxyl and amino groups to improve their potential for grafting bioactive molecules. The physico-chemical properties of the plasma-treated films were evaluated and compared to the untreated materials by water contact angle, SEM and AFM. The presence of new functional groups on the film surfaces has been assessed by ATR-FTIR spectra after chemical derivatization. Moreover, the biocompatibility of the plasma-treated films was studied with MG-63 human osteoblast-like cells, evaluating cell proliferation, viability and morphology at 1, 3 and 7 days. PMID:23266023

Taraballi, F; Zanini, S; Lupo, C; Panseri, S; Cunha, C; Riccardi, C; Marcacci, M; Campione, M; Cipolla, L

2012-12-05

54

Film morphology, orientation and performance of dodecyl/carboxyl functional polysiloxane on cotton substrates  

NASA Astrophysics Data System (ADS)

A novel polysiloxane (RCAS) bearing dodecyl and carboxyl side groups was synthesized by reaction of a dodecyl/amino functionalized polysiloxane with maleic anhydride. Film morphology, molecular orientation and performance of the synthesized polysiloxane on cotton substrates were investigated by field emission scanning electron microscope (FESEM), atomic force microscope (AFM), X-ray photoelectron microscope (XPS) and so on. Affected by the dodecyl and polar carboxyl side groups, RCAS formed a semi hydrophilic, macroscopic smooth but actually uneven siloxane film with many pillar-likes or small humps on the treated substrate surfaces. On the natural cotton surface, RCAS may take such an orientation to form its film that the Si-CH 3, Si-C 12H 25 groups projected outward into air, while the carboxyl groups pointed inward to the substrate, interacting with the hydroxyls of the cotton substrates in ester and hydrogen bonds or twisted away from the negatively charged cotton fiber surface. As a result of such a film-formation, RCAS provided the treated fabric with not only a good wettability of about 22.96 s and a whiteness of 88.44°, but also an improved softness as well as thickening handle.

An, Qiufeng; Wang, Kefeng; Jia, Yun

2011-03-01

55

Strong-acid, carboxyl-group structures in fulvic acid from the Suwannee River, Georgia. 2. Major structures  

USGS Publications Warehouse

Polycarboxylic acid structures that account for the strong-acid characteristics (pKa1 near 2.0) were examined for fulvic acid from the Suwannee River. Studies of model compounds demonstrated that pKa values near 2.0 occur only if the ??-ether or ??-ester groups were in cyclic structures with two to three additional electronegative functional groups (carboxyl, ester, ketone, aromatic groups) at adjacent positions on the ring. Ester linkage removal by alkaline hydrolysis and destruction of ether linkages through cleavage and reduction with hydriodic acid confirmed that the strong carboxyl acidity in fulvic acid was associated with polycarboxylic ??-ether and ??-ester structures. Studies of hypothetical structural models of fulvic acid indicated possible relation of these polycarboxylic structures with the amphiphilic and metal-binding properties of fulvic acid.

Leenheer, J. A.; Wershaw, R. L.; Reddy, M. M.

1995-01-01

56

Functionalized carbon nanotubes containing isocyanate groups  

SciTech Connect

Functionalized carbon nanotubes containing isocyanate groups can extend the nanotube chemistry, and may promote their many potential applications such as in polymer composites and coatings. This paper describes a facile method to prepare functionalized carbon nanotubes containing highly reactive isocyanate groups on its surface via the reaction between toluene 2,4-diisocyanate and carboxylated carbon nanotubes. Fourier-transformed infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) confirmed that reactive isocyanate groups were covalently attached to carbon nanotubes. The content of isocyanate groups were determined by chemical titration and thermogravimetric analysis (TGA)

Zhao Chungui [Joint Laboratory of Polymer Science and Materials, Institute of Chemistry, Chinese Academy of Sciences, Number 2, Zhongguancun North 1 St., Beijing 100080 (China); Ji Lijun [Joint Laboratory of Polymer Science and Materials, Institute of Chemistry, Chinese Academy of Sciences, Number 2, Zhongguancun North 1 St., Beijing 100080 (China); Liu Huiju [Joint Laboratory of Polymer Science and Materials, Institute of Chemistry, Chinese Academy of Sciences, Number 2, Zhongguancun North 1 St., Beijing 100080 (China); Hu Guangjun [Joint Laboratory of Polymer Science and Materials, Institute of Chemistry, Chinese Academy of Sciences, Number 2, Zhongguancun North 1 St., Beijing 100080 (China); Zhang Shimin [Joint Laboratory of Polymer Science and Materials, Institute of Chemistry, Chinese Academy of Sciences, Number 2, Zhongguancun North 1 St., Beijing 100080 (China); Yang Mingshu [Joint Laboratory of Polymer Science and Materials, Institute of Chemistry, Chinese Academy of Sciences, Number 2, Zhongguancun North 1 St., Beijing 100080 (China)]. E-mail: yms@iccas.ac.cn; Yang Zhenzhong [Joint Laboratory of Polymer Science and Materials, Institute of Chemistry, Chinese Academy of Sciences, Number 2, Zhongguancun North 1 St., Beijing 100080 (China)]. E-mail: yangzz@iccas.ac.cn

2004-12-01

57

Acidity of carboxyl group of tyrosine and its analogues and derivatives studied by steady-state fluorescence spectroscopy  

Microsoft Academic Search

The acidity of the carboxyl group of tyrosine and its derivatives and analogues was studied by means of fluorimetric titration using a steady-state fluorescence method. The pKa value of carboxyl group of tyrosine, its analogues and derivatives with blocked amino or hydroxyl group or both determined from the fluorimetric titration curve indicates that the methylation of hydroxyl group of phenolic

Mariusz Szabelski; Katarzyna Guzow; Alicja Rzeska; Joanna Malicka; Monika Przyborowska; Wies?aw Wiczk

2002-01-01

58

Functional Group Analysis.  

ERIC Educational Resources Information Center

|Literature on analytical methods related to the functional groups of 17 chemical compounds is reviewed. These compounds include acids, acid azides, alcohols, aldehydes, ketones, amino acids, aromatic hydrocarbons, carbodiimides, carbohydrates, ethers, nitro compounds, nitrosamines, organometallic compounds, peroxides, phenols, silicon compounds,…

Smith, Walter T., Jr.; Patterson, John M.

1984-01-01

59

Carboxyl-functionalized task-specific ionic liquids for solubilizing metal oxides.  

PubMed

Imidazolium, pyridinium, pyrrolidinium, piperidinium, morpholinium, and quaternary ammonium bis(trifluoromethylsulfonyl)imide salts were functionalized with a carboxyl group. These ionic liquids are useful for the selective dissolution of metal oxides and hydroxides. Although these hydrophobic ionic liquids are immiscible with water at room temperature, several of them form a single phase with water at elevated temperatures. Phase separation occurs upon cooling. This thermomorphic behavior has been investigated by (1)H NMR, and it was found that it can be attributed to the temperature-dependent hydration and hydrogen-bond formation of the ionic liquid components. The crystal structures of four ionic liquids and five metal complexes have been determined. PMID:18841931

Nockemann, Peter; Thijs, Ben; Parac-Vogt, Tatjana N; Van Hecke, Kristof; Van Meervelt, Luc; Tinant, Bernard; Hartenbach, Ingo; Schleid, Thomas; Ngan, Vu Thi; Nguyen, Minh Tho; Binnemans, Koen

2008-10-08

60

Structural characterization and mass transfer properties of nonporous segmented polyurethane membrane: Influence of hydrophilic and carboxylic group  

Microsoft Academic Search

An attempt has been made to investigate the influence of hydrophilic and carboxylic groups on structure and mass transfer properties of polypropylene glycol (number average molecular weight of 1000gmol?1, PPG 1000) based segmented polyurethane (SPU). Polyethylene glycol (number average molecular weight of 3400gmol?1, PEG 3400) (hydrophilic segment) or dimethylol propionic acid (DMPA) (carboxylic group) or combination of PEG 3400 and

S. Mondal; J. L. Hu

2006-01-01

61

Renormalization group functional equations  

SciTech Connect

Functional conjugation methods are used to analyze the global structure of various renormalization group trajectories and to gain insight into the interplay between continuous and discrete rescaling. With minimal assumptions, the methods produce continuous flows from step-scaling {sigma} functions and lead to exact functional relations for the local flow {beta} functions, whose solutions may have novel, exotic features, including multiple branches. As a result, fixed points of {sigma} are sometimes not true fixed points under continuous changes in scale and zeroes of {beta} do not necessarily signal fixed points of the flow but instead may only indicate turning points of the trajectories.

Curtright, Thomas L. [CERN, CH-1211 Geneva 23 (Switzerland); Department of Physics, University of Miami, Coral Gables, Florida 33124-8046 (United States); Zachos, Cosmas K. [High Energy Physics Division, Argonne National Laboratory, Argonne, Illinois 60439-4815 (United States)

2011-03-15

62

Properties of poly( ? -benzyl l -glutamate) membrane modified by polyurethane containing carboxyl group  

Microsoft Academic Search

A series of poly(?-benzyl l-glutamate) (PBLG)\\/polyurethane (PU) containing carboxyl group blend membranes was prepared by casting the polymer blend solution\\u000a in dimethylformamide (DMF). The surface morphology of the PBLG\\/PU blend membranes was investigated by atomic force microscopy\\u000a (AFM) and scanning electron microscopy (SEM). Thermal, mechanical, and chemical properties of PBLG\\/PU blend membranes were\\u000a studied by differential scanning calorimetry (DSC), tensile

Guo-Quan Zhu; Fa-Gang Wang; Qiao-Chun Gao; Guo-Chang Li; Ping Wang

2011-01-01

63

Monodisperse hydrophilic polymer microspheres having carboxylic acid groups prepared by distillation precipitation polymerization  

Microsoft Academic Search

Monodisperse hydrophilic polymer microspheres having carboxyl acid group with spherical shape in the range of 160nm and 1.52?m were prepared by distillation copolymerizations of (meth)acrylic acid with either ethyleneglycol dimethacrylate (EGDMA) or divinylbenzene (DVB) as crosslinker. Polymerization was carried out with 2,2?-azobisisobutyronitrile (AIBN) as initiator in neat acetonitrile without stirring. The polymer microspheres were formed and precipitated out from the

Feng Bai; Xinlin Yang; Rui Li; Bo Huang; Wenqiang Huang

2006-01-01

64

Synthesis of cross-linked magnetic composite microspheres containing carboxyl groups  

Microsoft Academic Search

Fe3O4 magnetic nano-particles were prepared by a co-precipitation method and were modified using oleic acid. Then, the cross-linked\\u000a magnetic compsoite microspheres containing a carboxyl group were prepared by using an improved emulsion polymerization with\\u000a divinylbenzene (DVB) as the cross-linking agent. The composite microspheres comprised the Fe3O4 magnetic nano-particles as cores and the copolymer of styrene and acrylic acid as shells.

Jili Zhao; Zhaorang Han; Qiang Song; Ying Wang; Dan Sun

2008-01-01

65

Synthesis and properties of UV-curable hyperbranched polyurethane acrylate oligomers containing carboxyl groups  

Microsoft Academic Search

Using step by step polymerization process, the first- and second-generation hyperbranched polyesters were synthesized with\\u000a N,N-diethylol-3-amine methylpropionate as branched monomer and pentaerythrite as a core molecule. The second-generation hyperbranched\\u000a polyurethane acrylate oligomers containing carboxyl groups were obtained by further reacting with semiadduct urethane monoacrylate\\u000a and maleic anhydride. The structures of the oligomers were investigated with elemental analysis, FT–IR, and NMR.

Wensong Han; Baoping Lin; Hong Yang; Xueqin Zhang

66

Preparation and Characterization of Poly(methyl methacrylate)-functionalized Carboxyl Multi-walled Carbon Nanotubes  

Microsoft Academic Search

An in situ polymerization process was used to prepare poly (methyl methacrylate) (PMMA)-functionalized carboxyl multi-walled carbon nanotubes using carboxylate carbon nanotubes and methyl methacrylate as reactants and benzoyl peroxide as an initiator agent. The functionalized multi-walled carbon nanotubes were characterized using transmission electron microscope, scanning electron microscope, nuclear magnetic resonance, Fourier transform infrared spectroscopy, thermogravimetric analysis and Raman. The results

Qing-Jie Meng; Xing-Xiang Zhang; Shi-He Bai; Xue-Chen Wang

2007-01-01

67

[Modification of the carboxyl and amine groups of the cellulolytic enzymes of Aspergillus awamori].  

PubMed

The activity and stability of some enzymes of Asp. awamori cellulolytic complex were studied as affected by chemical modification of carboxylic groups with N,N'-dicyclohexyl carbodiimide (DCCD) and amine groups with glutaric aldehyde. The carboxylic groups are established to be necessary for manifestation of the activities of C1- and C2-cellulases, Cx-exo- and Cx-endoglucanases. Their role is negligible in the action of beta-glucosidase. The activity of individual cellulases was studied as affected by nucleophilic substitution of DCCD-activated COOH-groups by various reagents (glycine amide, leucine amide, tyrosine amide and N-benzoyl-l-arginine-methyl ether-hydrochloride). Tyrosine amide is the least inacting reagent for all the enzymes, glycine amide is somewhat more activating. Essential differences are shown in the chemical and catalytic properties of Cx-exoglucanase and beta-glucosidase. It is found (under the effect of glutaric aldehyde) that amino groups are significant for manifestation of the activities of C1- and C2-cellulases and Cx-endoglucanase and to a less extent for that of Cs-exoglucanase and beta-glucosidase. It is supposed that electrostatic interactions of the carbolytic and amine groups might be an essential factor for stability of C1- and C2-cellulases and Cx-endoglucanase. PMID:1021913

Tsyperovich, A S; Surgova, T M

68

Synthesis, characterization, guest inclusion, and photophysical studies of gold nanoparticles stabilized with carboxylic Acid groups of organic cavitands.  

PubMed

Water-soluble gold nanoparticles (AuNP) stabilized with cavitands having carboxylic acid groups have been synthesized and characterized by a variety of techniques. Apparently, the COOH groups similar to thiol are able to prevent aggregation of AuNP. These AuNP were stable either as solids or in aqueous solution. Most importantly, these cavitand functionalized AuNP were able to include organic guest molecules in their cavities in aqueous solution. Just like free cavitands (e.g., octa acid), cavitand functionalized AuNP includes guests such as 4,4'-dimethylbenzil and coumarin-1 through capsule formation. The exact structure of the capsular assembly is not known at this stage. Upon excitation there is communication between the excited guest present in the capsule and gold atoms and this results in quenching of phosphorescence from 4,4'-dimethylbenzil and fluorescence from coumarin-1. PMID:24059841

Mondal, Barnali; Kamatham, Nareshbabu; Samanta, Shampa R; Jagadesan, Pradeepkumar; He, Jibao; Ramamurthy, V

2013-10-04

69

Binding properties of solubilized gonadotropin-releasing hormone receptor: role of carboxylic groups  

SciTech Connect

The interaction of /sup 125/I-buserelin, a superactive agonist of gonadotropin-releasing hormone (GnRH), with solubilized GnRH receptor was studied. The highest specific binding of /sup 125/I-buserelin to solubilized GnRH receptor is evident at 4/sup 0/C, and equilibrium is reached after 2 h of incubation. The soluble receptor retained 100% of the original binding activity when kept at 4 or 22/sup 0/C for 60 min. Mono- and divalent cations inhibited, in a concentration-dependent manner, the binding of /sup 125/I-buserelin to solubilized GnRH receptor. Monovalent cations require higher concentrations than divalent cations to inhibit the binding. Since the order of potency with the divalent cations was identical with that of their association constants to dicarboxylic compounds, it is suggested that there are at least two carboxylic groups of the receptor that participate in the binding of the hormone. The carboxyl groups of sialic acid residues are not absolutely required for GnRH binding since the binding of /sup 125/I-buserelin to solubilized GnRH receptor was only slightly affected by pretreatment with neuraminidase and wheat germ agglutinin. The finding that polylysines stimulate luteinizing hormone (LH) release from pituitary cell cultures with the same efficacy as GnRH suggest that simple charge interactions can induce LH release. According to these results, the authors propose that the driving force for the formation of the hormone-receptor complex is an ionic interaction between the positively charged amino acid arginine in position 8 and the carboxyl groups in the binding site.

Hazum, E.

1987-11-03

70

Zn(OTf)2-promoted chemoselective esterification of hydroxyl group bearing carboxylic acids.  

PubMed

Selective esterification of aliphatic and aromatic carboxylic acids with various alcohols is studied using triphenylphosphine, I2, and a catalytic amount of Zn(OTf)2. Use of this catalyst allows the formation of esters at a faster rate with good to excellent yield by activating the in situ generated acyloxyphosphonium ion intermediate. During the esterification process, both their aromatic and aliphatic hydroxyl groups are fully preserved from transesterification. The results show that the bulkiness and the reactivity of this doubly activated intermediate III control the selectivity and the rate of the reaction, respectively. The method is also useful for direct amidation reactions. PMID:23350970

Mamidi, Narsimha; Manna, Debasis

2013-02-06

71

The comparison between carboxyl, amido and hydroxy group in influencing electrorheological performance  

Microsoft Academic Search

Three kinds of electrorheological (ER) materials with carboxyl, amido and hydroxyl group, respectively, were synthesized by\\u000a a simple adsorption method. The powder of silicon dioxide as a substrate of the materials, as well as terephthalic acid [p-C6H4(COOH)2, abbr.: phen-COOH], p-phenylenediamine [p-C6H4(NH2)2, abbr.: phen-NH2] and hydroquinone [p-C6H4(OH)2, abbr.: phen-OH] were chosen as starting materials. The ER properties of suspensions of the

Huo Li; Jun-Ran Li; Fu-Hui Liao

2011-01-01

72

Chemical derivatization of Peptide carboxyl groups for highly efficient electron transfer dissociation.  

PubMed

The carboxyl groups of tryptic peptides were derivatized with a tertiary or quaternary amine labeling reagent to generate more highly charged peptide ions that fragment efficiently by electron transfer dissociation (ETD). All peptide carboxyl groups-aspartic and glutamic acid side-chains as well as C-termini-were derivatized with an average reaction efficiency of 99 %. This nearly complete labeling avoids making complex peptide mixtures even more complex because of partially-labeled products, and it allows the use of static modifications during database searching. Alkyl tertiary amines were found to be the optimal labeling reagent among the four types tested. Charge states are substantially higher for derivatized peptides: a modified tryptic digest of bovine serum albumin (BSA) generates ~90% of its precursor ions with z? > ?2, compared with less than 40 % for the unmodified sample. The increased charge density of modified peptide ions yields highly efficient ETD fragmentation, leading to many additional peptide identifications and higher sequence coverage (e.g., 70 % for modified versus only 43 % for unmodified BSA). The utility of this labeling strategy was demonstrated on a tryptic digest of ribosomal proteins isolated from yeast cells. Peptide derivatization of this sample produced an increase in the number of identified proteins, a >50 % increase in the sequence coverage of these proteins, and a doubling of the number of peptide spectral matches. This carboxyl derivatization strategy greatly improves proteome coverage obtained from ETD-MS/MS of tryptic digests, and we anticipate that it will also enhance identification and localization of post-translational modifications. PMID:23918461

Frey, Brian L; Ladror, Daniel T; Sondalle, Samuel B; Krusemark, Casey J; Jue, April L; Coon, Joshua J; Smith, Lloyd M

2013-08-06

73

Chemical Derivatization of Peptide Carboxyl Groups for Highly Efficient Electron Transfer Dissociation  

NASA Astrophysics Data System (ADS)

The carboxyl groups of tryptic peptides were derivatized with a tertiary or quaternary amine labeling reagent to generate more highly charged peptide ions that fragment efficiently by electron transfer dissociation (ETD). All peptide carboxyl groups—aspartic and glutamic acid side-chains as well as C-termini—were derivatized with an average reaction efficiency of 99 %. This nearly complete labeling avoids making complex peptide mixtures even more complex because of partially-labeled products, and it allows the use of static modifications during database searching. Alkyl tertiary amines were found to be the optimal labeling reagent among the four types tested. Charge states are substantially higher for derivatized peptides: a modified tryptic digest of bovine serum albumin (BSA) generates ~90% of its precursor ions with z > 2, compared with less than 40 % for the unmodified sample. The increased charge density of modified peptide ions yields highly efficient ETD fragmentation, leading to many additional peptide identifications and higher sequence coverage (e.g., 70 % for modified versus only 43 % for unmodified BSA). The utility of this labeling strategy was demonstrated on a tryptic digest of ribosomal proteins isolated from yeast cells. Peptide derivatization of this sample produced an increase in the number of identified proteins, a >50 % increase in the sequence coverage of these proteins, and a doubling of the number of peptide spectral matches. This carboxyl derivatization strategy greatly improves proteome coverage obtained from ETD-MS/MS of tryptic digests, and we anticipate that it will also enhance identification and localization of post-translational modifications.

Frey, Brian L.; Ladror, Daniel T.; Sondalle, Samuel B.; Krusemark, Casey J.; Jue, April L.; Coon, Joshua J.; Smith, Lloyd M.

2013-11-01

74

Preparation of carboxyl group-modified palladium nanoparticles in an aqueous solution and their conjugation with DNA  

NASA Astrophysics Data System (ADS)

The use of nanomaterials in biomolecular labeling and their corresponding detection has been attracting much attention, recently. There are currently very few studies on palladium nanoparticles (Pd NPs) due to their lack of appropriate surface functionalities for conjugation with DNA. In this paper, we thus firstly present an approach to prepare carboxyl group-modified Pd NPs (with an average size of 6 nm) by the use of 11-mercaptoundecanoic acid (MUDA) as a stabilizer in the aqueous solution. The effect of the various reducing reaction conditions on the morphology of the Pd NPs was investigated. The particles were further characterized by TEM, UV-vis, FT-IR and XPS techniques. DNA was finally covalently conjugated to the surface of the Pd NPs through the activation of the carboxyl group, which was confirmed by agarose gel electrophoresis and fluorescence analysis. The resulting Pd NPs-DNA conjugates show high single base pair mismatch discrimination capabilities. This work therefore sets a good foundation for further applications of Pd NPs in bio-analytical research.

Wang, Zhifei; Li, Hongying; Zhen, Shuang; He, Nongyue

2012-05-01

75

Synthesis and characterization of a novel carboxyl group containing (co)polyimide with sulfur in the polymer backbone  

PubMed Central

Summary Soluble functional (co)polyimides are of great interest in the area of separation processes or optical applications, due to their excellent mechanical-, thermal- and optical properties, their superior processability and the ability to adapt their properties to a wide range of special applications. Therefore, two series of novel (co)polyimides containing fluorinated sulfur- and carboxylic acid groups consisting of 4,4?-(hexafluoroisopropylidene)di(phthalic anhydride) (6FDA), 3,5-diaminobenzoic acid (DABA), 4,4?-diaminodiphenylsulfide (4,4?-SDA) and 3,3?-diaminodiphenylsulfone (3,3?-DDS) were synthesized in a two-step polycondensation reaction. The synthesized copolymers were characterized by using NMR, FTIR, GPC, and DSC. Furthermore, with regard to processing and potential applications, the thermal stability, solubility in common organic solvents, moisture uptake, and transparency were investigated. Compared to commercially available transparent polymers, i.e., polymethylmethacrylate and cycloolefin polymers, the sulfur (co)polyimides containing carboxyl groups showed much higher glass-transition temperatures, comparably low moisture uptake and high transmission at the sodium D-line. Furthermore, good solubility in commonly used organic solvents makes them very attractive as high-performance coating materials.

Mrsevic, Miroslav; Dusselberg, David

2012-01-01

76

Hydrogen-bonding linkage of thymidine derivatives with carboxylic acid and pyridyl groups in a crystalline state.  

PubMed

Thymidine derivatives with carboxylic acid and pyridyl groups were synthesized for constructing one-dimensional network structure based on hydrogen bonding in crystalline state. The solid sate structures and hydrogen bonding networks of the thymidine derivatives were characterized by single X-ray diffraction analysis. The thymidine derivatives formed a zwitterion structure with a pyridinium proton and a carboxylate moiety in a crystalline state due to transfer of a proton from the carboxylic acid to the pyridyl moiety. Strong hydrogen bonds between the pyridinium proton and the carboxylate moiety connected the thymidine units, resulting in a one-dimensional polymeric structure with a uniform direction reminiscent of the structure of single-strand polythymidine. The chemical structure of the pyridyl group affects the hydrogen-bonding networks. The well-designed hydrogen-bonding interaction served as connecting parts for polythymidine mimics even in the presence of other hydrogen-bonding motifs such as nucleobases. PMID:23901479

Hoshino, Junichi; Kuwabara, Junpei; Kanbara, Takaki

2013-07-01

77

One-step hydrothermal synthesis of carboxyl-functionalized upconversion phosphors for bioapplications.  

PubMed

In this paper, we report a facile one-step hydrothermal method to synthesize phase-, size-, and shape-controlled carboxyl-functionalized rare-earth fluorescence upconversion phosphors by using a small-molecule binary acid, such as malonic acid, oxalic acid, succinic acid, or tartaric acid as capping agent. The crystals, from nano- to microstructures with diverse shapes that include nanospheres, microrods, hexagonal prisms, microtubes, microdisks, polygonal columns, and hexagonal tablets, can be obtained with different reaction times, reaction temperatures, molar ratios of capping agent to sodium hydroxide, and by varying the binary acids. Fourier transform infrared, thermogravimetric analysis, and upconversion luminescence spectra measurements indicate that the synthesized NaYF(4):Yb/Er products with hydrophilic carboxyl-functionalized surface offer efficient upconversion luminescent performance. Furthermore, the antibody/secondary antibody conjugation can be realized by the carboxyl-functionalized surfaces of the upconversion phosphors, thus indicating the potential bioapplications of these kinds of materials. PMID:22996059

Yang, Jianping; Shen, Dengke; Li, Xiaomin; Li, Wei; Fang, Yin; Wei, Yong; Yao, Chi; Tu, Bo; Zhang, Fan; Zhao, Dongyuan

2012-09-20

78

Surface grafting of carboxylic groups onto thermoplastic polyurethanes to reduce cell adhesion  

NASA Astrophysics Data System (ADS)

The interaction of polymers with other materials is an important issue, being their surface properties clearly crucial. For some important polymer applications, their surfaces have to be modified. Surface modification aims to tailor the surface characteristics of a material for a specific application without affecting its bulk properties. Materials can be surface modified by using biological, chemical or physical methods. The aim of this work was to improve the reactivity of the thermoplastic polyurethane (TPU) material (Elastollan®) surface and to make its surface cell repellent by grafting carboxylic groups onto its surface. Two TPU materials were studied: a polyether-based TPU and a polyester-based TPU. The grafting efficiency was evaluated by contact angle measurements and by analytical determination of the COOH groups. Scanning electron microscopy (SEM) of the membranes surface was performed as well as cell adhesion tests. It was proved that the surfaces of the TPUs membranes were successfully modified and that cell adhesion was remarkably reduced.

Alves, P.; Ferreira, P.; Kaiser, Jean-Pierre; Salk, Natalie; Bruinink, Arie; de Sousa, Hermínio C.; Gil, M. H.

2013-10-01

79

Effect of the carboxylic acid groups on water sorption, thermal stability and dielectric properties of polyimide films  

Microsoft Academic Search

Films from copolyimides containing side carboxylic acid groups were prepared in –COOH and COO?Na+ forms to study the effect of the side groups content on some physical properties such as water absorption, thermal stability and electrical parameters. The thermal stability was evaluated by TGA and the results showed that degradation temperatures depended not only on the side groups content but

Eva M. Maya; Juana Benavente; Javier de Abajo

80

Controlling mixed-protein adsorption layers on colloidal alumina particles by tailoring carboxyl and hydroxyl surface group densities.  

PubMed

We show that different ratios of bovine serum albumin (BSA) and lysozyme (LSZ) can be achieved in a mixed protein adsorption layer by tailoring the amounts of carboxyl (-COOH) and aluminum hydroxyl (AlOH) groups on colloidal alumina particles (d50 ? 180 nm). The particles are surface-functionalized with -COOH groups, and the resultant surface chemistry, including the remaining AlOH groups, is characterized and quantified using elemental analysis, ? potential measurements, acid-base titration, IR spectroscopy, electron microscopy, nitrogen adsorption, and dynamic light scattering. BSA and LSZ are subsequently added to the particle suspensions, and protein adsorption is monitored by in situ ? potential measurements while being quantified by UV spectroscopy and gel electrophoresis. A comparison of single-component and sequential protein adsorption reveals that BSA and LSZ have specific adsorption sites: BSA adsorbs primarily via AlOH groups, whereas LSZ adsorbs only via -COOH groups (1-2 -COOH groups on the particle surface is enough to bind one LSZ molecule). Tailoring such groups on the particle surface allows control of the composition of a mixed BSA and LSZ adsorption layer. The results provide further insight into how particle surface chemistry affects the composition of protein adsorption layers on colloidal particles and is valuable for the design of such particles for biotechnological and biomedical applications. PMID:23875793

Meder, Fabian; Kaur, Supreet; Treccani, Laura; Rezwan, Kurosch

2013-07-31

81

Catalytic properties of carboxylic acid functionalized-polymer microsphere-stabilized gold metallic colloids.  

PubMed

Polymer-microsphere-stabilized gold metallic colloids have been prepared by a novel strategy of simple and convenient reduction of the metallic salt through the stabilization of the active carboxylic acid group on the gel and surface layer of the microsphere. The nature of the interaction between the carboxylic acid and Au nanoparticles was studied in detail by XPS. Preliminary results indicate that polymer-microsphere-stabilized gold colloids are active catalysts for the reduction of 4-nitrophenol to 4-aminophenol with sodium borohydride as reductant. The catalytic properties of the stabilized catalyst for recycling were also investigated. PMID:17007867

Liu, Wei; Yang, Xinlin; Huang, Wenqiang

2006-09-27

82

[New low temperature initiator system for dental adhesive resins. Application of peroxyesters with carboxyl group].  

PubMed

Adhesion between dentin and MMA resin was investigated using chemically activated initiator system consisting of 1,3,5-trimethyl-2-thiobarbituric acid, cupric salt, chloride ion, and tert.-butyl peroxymaleic acid (MA) with carboxyl group which usually has affinity to tooth. The adhesive strength of the MMA/PMMA resin to bovine dentin increased significantly to 8-10 MPa by addition of MA, while the adhesive strength was 4 MPa without MA. When the bonding broke at higher than 7 MPa, the adhesive resin layer usually fractured cohesively and the interfacial fracture did not occur. The bond strength obtained in this experiment was comparable to that obtained with MMA resin using TBBO and ferric ion initiator system which is known as the best initiator system for dentin available. PMID:2135549

Ohta, T; Kadoma, Y; Imai, Y

1990-11-01

83

Functional Group Analysis.  

ERIC Educational Resources Information Center

|Discusses analytical methods selected from current research articles. Groups information by topics of general interest, including acids, aldehydes and ketones, nitro compounds, phenols, and thiols. Cites 97 references. (CS)|

Smith, Walter T., Jr.; Patterson, John M.

1980-01-01

84

Poly(3-hydroxyoctanoate) containing pendant carboxylic groups for the preparation of nanoparticles aimed at drug transport and release  

Microsoft Academic Search

Copolymers of poly(3-hydroxyoctanoate) (PHO) with carboxylic groups in lateral chains have been prepared by chemical modification of unsaturated bacterial polyesters. The oxidation of the pendant alkenes is complete and important loss in molecular weight of polymer was observed. The presence of repeating units containing pendant carboxy groups in the proportion of 25% has enhanced hydrophilicity of these new polymeric structures.

N Kurth; E Renard; F Brachet; D Robic; Ph Guerin; R Bourbouze

2002-01-01

85

Microwave-Induced Chemical Functionalization of Carboxylated Multi-Walled Nanotubes With 2,3-diaminopyridine  

Microsoft Academic Search

In this paper, the microwave-induced chemical functionalization of carboxylated multi-walled carbon nanotubes (MWNT-COOH) by 2,3-diaminopyridine, have been investigated. The major advantage of this high-energy procedure is reducing the reaction time to the order of minutes and the number of steps in the reaction procedure compared to that of conventional functionalization processes. These functionalizations involve amidation and cycloaddition reactions, respectively. The

Javad Azizian; Hasan Tahermansouri; Davood Chobfrosh Khoei; Khadijeh Yadollahzadeh; Akram Sadat Delbari

2012-01-01

86

Preparation of sulfate- and carboxyl-functionalized magnetite\\/polystyrene spheres for further deposition of gold nanoparticles  

Microsoft Academic Search

A synthetic method developed for preparation of sulfate- and carboxyl-functionalized magnetite\\/polystyrene (Fe3O4\\/PS) spheres that can be further decorated with gold (Au) nanoparticles is reported. By using emulsifier-free emulsion polymerization\\u000a based on potassium persulfate (KPS)\\/methyl acrylic acid (MAA)\\/water system in the presence of Fe3O4\\/PS spheres used as the seeds, PMAA-coated magnetic Fe3O4-PS spheres were readily obtained. The sulfate group is inherent

Szu-Ching Hsiao; Jinn-Luh Ou; Yuh Sung; Chang-Pin Chang; Ming-Der Ger

2010-01-01

87

Novel sulfonated poly(arylene ether ketone) copolymers bearing carboxylic or benzimidazole pendant groups for proton exchange membranes  

Microsoft Academic Search

A novel strategy in which the benzimidazole group and sulfonic group are simultaneously attached to an aromatic polymer has been reported in this paper. For this purpose, sulfonated poly(arylene ether ketone) copolymers containing carboxylic acid groups (SPAEK-x-COOH, x refers to the molar percentage of sulfonated repeating units) are prepared by the aromatic nucleophilic polycondensation of sodium 5,5?-carbonyl-bis(2-fluobenzene-sulfonate) (SDFBP), 4,4?-difluorobenzophenone (DFBP)

Haidan Lin; Chengji Zhao; Zhiming Cui; Wenjia Ma; Tiezhu Fu; Hui Na; Wei Xing

2009-01-01

88

[Solid phase synthesis and chromatographic characteristics of nucleophilic agents conjugated with oligonucleotides containing 5'-terminal carboxyl group].  

PubMed

Conjugates of amines or short peptides with oligonucleotides containing 5'-terminal carboxyl group were prepared by solid phase chemical synthesis. A correlation between the physicochemical parameters and retention times of the synthesized conjugates was established by ion-pair reversed-phase HPLC. PMID:12845806

Kachalova, A V; Tashlitski?, V N; Stetsenko, D A; Romanova, E A; Gait, M J; Oretskaia, T S

89

Photo-induced electron transfer between dendritic zinc(II) phthalocyanine bearing carboxylic terminal groups and methyl viologen  

NASA Astrophysics Data System (ADS)

The intermolecular electron transfer between carboxylic dendritic zinc(II) phthalocyanine bearing carboxylic terminal groups(G1-ZnPc(COOH)8) and methyl viologens (MV2+) was studied by steady-state fluorescence and UV/Vis spectroscopy. The effect of different concentrations of MV2+ on intermolecular electron transfer was investigated. The results show that the fluorescence emission of this dendritic phthalocyanine could be greatly quenched with an increasing amount of MV2+ upon excitation at 610 nm. Our study suggests that this novel dendritic phthalocyanine is an effective new electron donor and transmission complex and could be used as a potential biosensor conjugated with suitable fluorescence quencher.

Wang, Yuhua; Chen, Jiangxu; Huang, Lishan; Xie, Shusen; Yang, Hongqin; Peng, Yiru

2012-12-01

90

Fourier transform infrared spectroscopic studies of hydrogen bonding interactions in materials containing carboxylic acid groups  

NASA Astrophysics Data System (ADS)

The results of Fourier transform infrared (FTIR) spectroscopic studies of the hydrogen bonding interactions in materials and blends containing carboxylic acid groups are presented. The self-association of p-n-alkoxybenzoic acids (AOBAs) exhibits liquid crystalline characteristics. The length of the terminal alkyl chain determines the crystal structure observed. For longer chain lengths (n = 7--18), an isotypic form is observed, where the segregation of the alkyl chains and aromatic rings allows for the stacking of the self-associated acid groups. This leads to infrared band splitting and a broadened carbonyl stretching region. The breadth can also be caused by the polymorphic state of the material, as in the case of the molecules possessing the shorter alkyl chains (n < 7). By blending these materials with amorphous polyethers, a competition for hydrogen bonds is induced. By diluting the AOBAs with the polyethers, the highly ordered state is disrupted and access to inter-associating partners is increased. Copolymers of methacrylic acid with styrene and 2,3-dimethylbutadiene were synthesized. Temperature stability (decreased anhydride formation) of these materials was improved by decreasing the number of adjacent methacrylic acid groups (<10 mol%). The self-association equilibrium constants were also calculated for each copolymer and compared with that of a low molecular weight analogue. The value of the self-association equilibrium constant increased with increasing chain flexibility. Therefore, an infinitely flexible chain should possess the same value of the self-association equilibrium constant as the low molecular weight analogue. The styrene copolymer was then blended with poly(tetrahydrofuran) and an inter-association equilibrium constant was determined. Despite an order of magnitude difference between the self- and inter-association equilibrium constants, the blends are miscible.

Cleveland, Christopher Scott

91

Effect of functional groups of humic substances on uf performance.  

PubMed

The role of different functional groups present in humic substances on the membrane flux is unclear. This study is undertaken to (1) separate the carboxyl and phenolic groups from a humic solution, and (2) evaluate the effect of each fractionated humic substances on the ultrafiltration (UF) performance. A weak-base amine resin was used for the adsorption (pH 7) and the subsequent desorption (pH 13) of the phenolic groups from a commercial humic solution. These fractions were evaluated qualitatively (via Fourier transform infrared spectroscopy) and quantitatively (titration); they were further subjected to the analyses of the trihalomethane formation potential (THMFP) and ultrafiltration performance. Although, a complete separation of the phenolic and carboxyl groups is not possible, the results nevertheless provide useful information about their effects on UF performance. The fraction with a higher content of the phenolic OH group exhibits the highest THMFP (190 microg/mg C), whereas the fraction with a higher content of the carboxyl groups exhibits more flux decline. The UF system evaluated is unable to remove a significant portion of THM precursors, resulting in high THMs in permeate. The use of powdered activated carbon for the pretreatment of these fractions fails to improve membrane fouling. The pore size of UF membrane does not appear to affect the membrane flux, and the switch from the hydrophobic to hydrophilic membrane only slight improves the permeate flux. PMID:11394773

Lin, C F; Liu, S H; Hao, O J

2001-07-01

92

Membrane extraction of organic compounds. 3. A new receptor fragment for carboxylate groups based of the calix[4]arene platform  

Microsoft Academic Search

A new type of macrocyclic receptor able to bind organic substrates containing carboxy and carboxylate groups was designed on the basis of 1,3-disubstituted calix[4]arenes. A series of disubstitited calix[4]arenes were prepared in 60—80% yields by selective 1,3-alkylation of p-tert-butylcalix[4]arene. The compounds obtained were tested as carriers for dl-tartaric, glycolic, dl-amygdalic, and dl-glutamic acids through liquid membranes immobilized on a polymer

I. S. Antipin; I. I. Stoikov; A. A. Khrustalev; A. I. Konovalov

2001-01-01

93

Synthesis and characterizations of a novel zwitterionic hybrid copolymer containing both sulfonic and carboxylic groups via sulfonation and zwitterionic process  

Microsoft Academic Search

A novel zwitterionic hybrid copolymer containing both sulfonic and carboxylic groups was synthesized via sulfonation, zwitterionic process and sol–gel reaction. The properties of the step products were characterized by FT-IR spectra, thermal analyses, MALDI measurements and SEM morphologies. FT-IR spectra confirmed the related reactions. TGA and DrTGA analyses showed that their thermal stability enhanced with an increase in the zwitterionic

Junsheng Liu; Tongwen Xu; Xiaozhao Han; Yanxun Fu

2006-01-01

94

Catalysis of an isotopic exchange between CO 2 and the carboxyl group of acetate by Methanosarcina barkeri grown on acetate  

Microsoft Academic Search

Cell suspensions of Methanosarcina barkeri (strain Fusaro) grown on acetate were found to catalyze the formation of methane and CO2 from acetate (30–40 nmol\\/min·mg protein) and an isotopic exchange between the carboxyl group of acetate and 14CO2 (30–40 nmol\\/min·mg protein). An isotopic exchange between [14C]-formate and acetate was not observed. Cells grown on methanol mediated neither methane formation from acetate

Bernhard Eikmanns; Rudolf K. Thauer

1984-01-01

95

Functionalized polyoxometalates with covalently linked bisphosphonate, N-donor or carboxylate ligands: from electrocatalytic to optical properties.  

PubMed

The structures of two families of hybrid organic-inorganic polyoxometalates (POMs) functionalized by covalently grafted carboxylate or bisphosphonate ligands are overviewed. The first family concerns the so-called POMOF materials, built from the connection of mixed-valent ?-Keggin type polyoxomolybdates via N-donor or carboxylate organic molecules coordinated to transition metal ions (Zn(II), Co(II), Ni(II)) grafted at the surface of the POMs. The simulation of the hypothetical zeolitic-like POMOF structures is presented and compared to the experimental ones. The second family gathers the various molecular Mo(V), Mo(VI) and W(VI) POMs incorporating directly into their architecture bisphosphonate (BP) ligands. The potentiality of this family of hybrid POMs comes from the organic group grafted on the carbon atom which bears the two phosphonate groups. For both families, besides the structural description, synthetic trends and an overview of their properties are presented. Namely, the electrocatalytic properties (production of H(2) and reduction of BrO(3)(-)) of the ?-Keggin type polyoxomolybdates are described. The optical and biological activities of the POM-BP compounds as well as their ability to form nanosystems are also reported. PMID:22763503

Dolbecq, Anne; Mialane, Pierre; Sécheresse, Francis; Keita, Bineta; Nadjo, Louis

2012-07-05

96

Personality Structure, Group Composition, and Group Functioning.  

National Technical Information Service (NTIS)

Three-man groups, homogeneous in personality structure, participated in a stock market simulation over 10 sessions. It was hypothesized that more abstract individuals (i.e., individuals who perceive a more multi-faceted world and who think in terms of alt...

B. W. Tuckman

1964-01-01

97

Immobilization of DNA via oligonucleotides containing an aldehyde or carboxylic acid group at the 5' terminus.  

PubMed Central

A general method for the immobilization of DNA through its 5'-end has been developed. A synthetic oligonucleotide, modified at its 5'-end with an aldehyde or carboxylic acid, was attached to latex microspheres containing hydrazide residues. Using T4 polynucleotide ligase and an oligonucleotide splint, a single stranded 98mer was efficiently joined to the immobilized synthetic fragment. After impregnation of the latex microspheres with the fluorescent dye, Nile Red and attachment of an aldehyde 16mer, 5 X 10(5) bead-DNA conjugates could be detected with a conventional fluorimeter. Images

Kremsky, J N; Wooters, J L; Dougherty, J P; Meyers, R E; Collins, M; Brown, E L

1987-01-01

98

Oxidation of linoleyl alcohol by potato tuber lipoxygenase: possible mechanism and the role of carboxylic group in substrate binding.  

PubMed

We have studied the aerobic oxidation of linoleyl alcohol (LAL) by potato tuber lipoxygenase in the presence of 0.02% (w/v) non-ionic detergent Lubrol PX (and its analog C12E10) and 0.1 mM sodium dodecyl sulfate to investigate the role of carboxylic group in substrate binding. While the enzyme displayed a comparable affinity toward LA and LAL, the rate of LAL oxidation was approximately one-fourth of that of linoleic acid. The pH-profile of the reaction suggests that the rate of LAL oxidation is controlled by two ionizable groups with pKa values of 5.3 and 7.5, with optimal pH being 6.4+/-0.1. Since LAL is not ionizable at this pH, we conclude that the rate of the reaction is controlled by two ionogenic groups of the enzyme. The primary dioxygenation product(s) of LAL had a maximal absorbance at 233+/-1 nm. The products have been isolated, catalytically hydrogenated with H2 over Pd on carbon, and analyzed by GC-MS. Two major equimolar products were found to be 9- and 13-hydroxystearyl alcohols, indicating that 9- and 13-hydroperoxylinoleyl alcohols are the primary dioxygenation products. Based on these results we propose that the carboxyl group of polyunsaturated fatty acid may not be involved in substrate binding of potato tuber lipoxygenase. PMID:9712698

Butovich, I A; Lukyanova, S M; Reddy, C C

1998-08-19

99

Preparation of non-covalently functionalized graphene using 9-anthracene carboxylic acid.  

PubMed

A simple way of achieving stable aqueous dispersion of graphene by non-covalent functionalization using 9-anthracene carboxylic acid has been successfully accomplished. Unlike in chemically reduced graphene, the C-sp(2) network of the graphene remains undistorted and therefore of superior quality. The non-covalent functionalization facilitates the exfoliation of graphite layers in a polarity controlled combination of media. A detailed exfoliation mechanism is proposed based on the controlled experiment and is supported by the data from UV-vis spectroscopy, transmission electron microscopy, and x-ray diffraction studies. Formation of monolayer graphene has been confirmed from Raman spectroscopy. The graphene based ultracapacitor shows a high value of specific capacitance (148 F g(-1)). PMID:21911926

Bose, Saswata; Kuila, Tapas; Mishra, Ananta Kumar; Kim, Nam Hoon; Lee, Joong Hee

2011-09-12

100

Carboxyl-functionalized magnetic microparticle carrier for isolation and identification of DNA in dairy products  

NASA Astrophysics Data System (ADS)

Magnetite nanoparticles about 14 nm in diameter were obtained by chemical coprecipitation of Fe(II) and Fe(III) salts with aqueous ammonia in the presence of poly(ethylene glycol) (PEG). Magnetic poly(glycidyl methacrylate) (PGMA) microspheres about 1?m in diameter were prepared by dispersion polymerization of GMA in aqueous ethanol in the presence of PEG-coated magnetite nanoparticles. The microspheres were hydrolyzed and carboxyl groups introduced by oxidation with KMnO4. The particles reversibly bound bacterial DNA of Bifidobacterium and Lactobacillus genera in the presence of high concentrations of PEG 6000 and sodium chloride from crude cell lysates of various dairy products (butter milk, cheese, yoghurt, probiotic tablets) or from cell lyophilisates. The presence of Bifidobacterium and Lactobacillus DNA in samples was confirmed by PCR amplification.

Horák, Daniel; Rittich, Bohuslav; Španová, Alena

2007-04-01

101

Inclusion of carboxyl function inside of cucurbiturils and its use in molecular switches.  

PubMed

We have prepared organic guest molecules in which two pyridinium rings are connected through an aromatic/aliphatic bridge bearing a carboxyl group. The supramolecular interactions between these guests and macrocyclic hosts cucurbit[7]uril (CB7) and cucurbit[8]uril (CB8) has been studied. We have demonstrated that the binding modes of the complexes depend on the type of central bridge present in the guest molecules and the size of the macrocycle. We have also showed that the binding mode between cucurbiturils and guests with aromatic bridges is pH independent. On the other hand, a guest containing an aliphatic bridge and CB7 formed a pseudorotaxane, which behaved as a pH-driven molecular switch. PMID:20839273

Kolman, Viktor; Kulhanek, Petr; Sindelar, Vladimir

2010-11-01

102

Carboxylate and amino group coated silver nanoparticles as joining materials for copper-to-copper silver joints.  

PubMed

Organic silver complexes are introduced where silver is linked either with a carboxyl group or with an amino group. Upon heating, nanoparticles are generated if the respective ligands are long enough to act as stabilizing agents in the nanoparticulate regime. With decomposition and volatilization of the organic material, the sintering of silver occurs. The thermal characteristics of the carboxylates silver-n-octanoate, silver-n-decanoate, and AgOOC(CH2OCH2)2CH2OCH3 are compared with silver-n-alkylamines (n = 8, 9, and 12), and their thermal behavior is discussed based on thermogravimetry (TG) measurements. The consecutive stages of a metallization process are addressed based on the properties of AgOOC(CH2OCH2)2CH2OCH3, and the usable effects of the individual phases of this metal organic compound are analyzed by cross-sectional scanning electron microscope (SEM) images of silver joints. Selection criteria are addressed based on the thermal behavior. A mechanism for the joining process is proposed, considering formation and sintering of the nanoparticles. It was found that the bulk material can be used for low-temperature joining processes. Strong adherence to copper as a basic material can be achieved. PMID:23447961

Oestreicher, A; Röhrich, T; Lerch, M

2012-12-01

103

The mixing effect of amine and carboxyl groups on electrorheological properties and its analysis by in situ FT-IR under an electric field.  

PubMed

Herein, the mixing effect of amine and carboxyl groups on electrorheological (ER) properties has been presented with the chitosan and alginic acid dispersed suspensions. Chitosan (for the amine group) and alginic acid (for the carboxyl group) are used to investigate the mixing effect of the amine and carboxyl groups on ER properties with the control of their mixing ratio in the silicone oil. The surface-chemical structure of the mixture of the chitosan and alginic acid particles in the silicone oil is demonstrated by in situ Fourier transform infrared (FT-IR) spectroscopy at various electric fields for the first time. This study focuses on whether the mixture of chemical groups in the ER fluid can promote ER properties or not, and in situ FT-IR analysis of the interface between ER particles in the silicone oil at various DC electric fields. The ER fluids exhibited the increase of the yield stress values with the increase of the counter group addition up to the weight ratio of 50?:?50 (chitosan?:?alginic acid). A noteworthy result is that the mixing effect of the amine and carboxyl groups resulting in enhanced ER properties is clearly proved. In the in situ FT-IR study, the complex form of amine and carboxyl groups of particles in the ER fluid was confirmed under the electric field. PMID:23945542

Ko, Young Gun; Lee, Hyun Jeong; Park, Yong Sung; Woo, Je Wan; Choi, Ung Su

2013-08-15

104

Investigation of oxygen functional groups in low rank coal  

SciTech Connect

The distribution of the organic oxygen content of coals among the principal oxygen containing functional groups typically is determined by a combination of chemical and spectroscopic methods (1,2) and results in a classification scheme such as % carboxyl, % hydroxyl, % carbonyl, and % ether. A notable subdivision in this classification scheme is the differentiation of phenols in a coal on the basis of their ortho-substitution pattern (3). Apart from this distinction, the further classification of oxygen into functional group subsets is virtually nonexistent. This paper presents initial experiments that indicate a fuller characterization of oxygen distribution in low rank coal is possible. The experimental approach couples selective chemical perturbation and solid state NMR analysis of the material, specifically, the fluorination of Argonne Premium Coal {number_sign}8, North Dakota lignite, and spectroscopic examination by high resolution solid state {sup 19}F NMR (4). The fluorination reagent is diethylaminosulfur trifluoride (DAST), (Et){sub 2}NSF{sub 3}, which promotes a rich slate of oxygen functional group interconversions that introduce fluorine into the coal matrix (5). The virtual absence of this element in coals make {sup 19}F an attractive NMR nuclei for this application (6). The present experiments use direct detection of the {sup 19}F nucleus under conditions of proton ({sup 1}H) heteronuclear dipolar decoupling and magic angle spinning (MAS). The ca 300 ppm range of {sup 19}F chemical shifts in common carbon-fluorine bonding configurations and high {sup 19}F nuclear sensitivity permit the identification of unique and chemically dilute functional groups in the coal milieu. The unique detection of aromatic and aliphatic carboxylic acids and primary and secondary alcohols provide examples of the exquisite functional group detail that is revealed by this combination of techniques.

Hagaman, E.W.; Lee, S.K.

1993-07-01

105

Major oxygen-containing functional groups present in humic and fulvic acid fractions isolated from contrasting marine environments  

Microsoft Academic Search

The major oxygen-containing functional groups present on various fractions of humic and fulvic acids extracted from different marine clays are carboxyls, phenolic and alcoholic hydroxyls and carbonyls. The total acidity of the different fractions ranges from 2 to 7 m-equiv.\\/g of organic matter and appears to arise mainly from carboxyl groups rather than phenolic hydroxyls. The carbonyl content of marine

M. A. Rashid; L. H. King

1970-01-01

106

Distinguishing two groups of flavin reductases by analyzing the protonation state of an active site carboxylic acid.  

PubMed

Flavin-containing reductases are involved in a wide variety of physiological reactions such as photosynthesis, nitric oxide synthesis, and detoxification of foreign compounds, including therapeutic drugs. Ferredoxin-NADP(H)-reductase (FNR) is the prototypical enzyme of this family. The fold of this protein is highly conserved and occurs as one domain of several multidomain enzymes such as the members of the diflavin reductase family. The enzymes of this family have emerged as fusion of a FNR and a flavodoxin. Although the active sites of these enzymes are very similar, different enzymes function in opposite directions, that is, some reduce oxidized nicotinamide adenine dinucleotide phosphate (NADP(+)) and some oxidize reduced nicotinamide adenine dinucleotide phosphate (NADPH). In this work, we analyze the protonation behavior of titratable residues of these enzymes through electrostatic calculations. We find that a highly conserved carboxylic acid in the active site shows a different titration behavior in different flavin reductases. This residue is deprotonated in flavin reductases present in plastids, but protonated in bacterial counterparts and in diflavin reductases. The protonation state of the carboxylic acid may also influence substrate binding. The physiological substrate for plastidic enzymes is NADP(+), but it is NADPH for the other mentioned reductases. In this article, we discuss the relevance of the environment of this residue for its protonation and its importance in catalysis. Our results allow to reinterpret and explain experimental data. PMID:21538544

Dumit, Verónica I; Cortez, Néstor; Matthias Ullmann, G

2011-05-02

107

Heterogeneous expression and functional relevance of the ubiquitin carboxyl-terminal hydrolase L1 in melanoma.  

PubMed

The expression of ubiquitin carboxyl-terminal hydrolase 1 (UCHL1) is deregulated in human cancer cells with tumor inhibiting or promoting functions. Due to less knowledge on the role of UCHL1 in melanoma progression, the expression pattern and function of UCHL1 as well as the deregulated signaling pathways were characterized. A large number of melanoma cell lines, tissue microarrays of melanoma lesions and control tissues were analyzed for UCHL1 expression using PCR, Western blot and/or immunohistochemistry. The analysis revealed that melanocyte cultures, 24 of 331 melanoma lesions, two of 18 short-term cultures and two of 19 melanoma cell lines tested, respectively, heterogeneously expressed UCHL1. The low frequency of UCHL1 expression in melanoma cells was due to gene silencing by promoter DNA hypermethylation. Using different transfection models an enzyme activity-dependent growth promoting function of UCHL1 via the activation of the mitogen-activated protein kinase signaling pathway was found in melanoma cells. Under oxygen stress a dose-dependent effect of UCHL1 was detected, which was mediated by a dynamic modification of the PI3K-Akt signaling. Thus, the aberrant UCHL1 expression in melanoma cells is linked to dynamic changes in growth properties and signal transduction cascades suggesting that UCHL1 provides a novel marker and/or therapeutic target at least for a subset of melanoma patients. PMID:23686552

Wulfänger, Jens; Biehl, Katharina; Tetzner, Anja; Wild, Peter; Ikenberg, Kristian; Meyer, Stefanie; Seliger, Barbara

2013-06-14

108

Direct Electrosynthesis and Characterization of a New Soluble Polythiophene Derivative Containing Carboxyl Groups in Boron Trifluoride Diethyl Etherate  

NASA Astrophysics Data System (ADS)

High-quality poly(3-thiophenemalonic acid) (P3TMA), a water-soluble polythiophene derivative, was successfully electrosynthesized in boron trifluoride diethyl etherate + 50% (by volume) trifluoroacetic acid at lower potential (0.1 V versus Pt). The carboxyl groups make P3TMA highly soluble in water, facilitating its potential application as a blue-light-emitting material. P3TMA film with conductivity of 16 S cm-1 obtained from this medium showed better redox activity and thermal stability. The structure and morphology of the polymer were studied by ultraviolet-visible, Fourier-transform infrared, and nuclear magnetic resonance spectroscopy and scanning electron microscopy, respectively. To the best of our knowledge, this is the first report on electrosynthesis of P3TMA film.

He, Yu; Guo, Wenjuan; Pei, Meishan; Zhang, Guangyou; Jiang, Junzi

2012-09-01

109

The Dehydration Step in the Enzyme-Coenzyme-B 12 Catalyzed Diol Dehydrase Reaction of 1,2-Dihydroxyethane Utilizing a Hydrogen-Bonded Carboxylic Acid Group as an Additional Cofactor:  A Computational Study  

Microsoft Academic Search

using density functional theory (B3LYP) calculations. This mechanism involves a neutral radical rather than a protonated radical (radical cation). 1,2-Dihydroxyethane was chosen as the substrate, and formic acid was selected as a model for the carboxylic acid group. The 1,2-dihydroxyeth-l-yl radical (produced by H-atom transfer from the substrate to the 5'-deoxyadenosyl radical) forms a nine-membered ring structure with the formic

Philip George; Per E. M. Siegbahn; Jenny P. Glusker; Charles W. Bock

1999-01-01

110

Surface Functionalization of Poly(ethylene terephthalate) Film and Membrane by Controlled Wet Chemistry: Chemical Characterization of Carboxylated Surfaces  

Microsoft Academic Search

Surface functionalization of poly(ethylene terephthalate) (PET) film or track-etched membrane was performed using the methods of organic synthesis conducted at the solid-liquid interface. Basic hydrolysis in aqueous acetonitrile followed by permanganate oxidation in diluted sulfuric acid created new carboxylic chain-ends. These reactive functions were assayed as follows: (i) activation with water soluble carbodiimide; (ii) coupling to 3 H-labeled amino acids;

Jacqueline Marchand-Brynaert; Michéle Deldime; Isabelle Dupont; Jean-Luc Dewez; Yves-Jacques Schneider

1995-01-01

111

Solid phase extraction of petroleum carboxylic acids using a functionalized alumina as stationary phase.  

PubMed

Petroleum essentially consists of a mixture of organic compounds, mainly containing carbon and hydrogen, and, in minor quantities, compounds with nitrogen, sulphur, and oxygen. Some of these compounds, such as naphthenic acids, can cause corrosion in pipes and equipment used in processing plants. Considering that the methods of separation or clean up the target compounds in low concentrations and in complex matrix use large amounts of solvents or stationary phases, is necessary to study new methodologies that consume smaller amounts of solvent and stationary phases to identify the acid components present in complex matrix, such as crude oil samples. The proposed study aimed to recover acid compounds using the solid phase extraction method, employing different types of commercial stationary ion exchange phases (SAX and NH(2)) and new phase alumina functionalized with 1,4-bis(n-propyl)diazoniabicyclo[2.2.2]octane chloride silsesquioxane (Dab-Al(2)O(3)), synthesized in this work. Carboxylic acids were used as standard mixture in the solid phase extraction for further calculation of recovery yield. Then, the real sample (petroleum) was fractionated into saturates, aromatics, resins, and asphaltenes, and the resin fraction of petroleum (B1) was eluted through stationary ion exchange phases. The stationary phase synthesized in this work showed an efficiency of ion exchange comparable to that of the commercial stationary phases. PMID:22589166

de Conto, Juliana Faccin; Nascimento, Juciara dos Santos; de Souza, Driele Maiara Borges; da Costa, Luiz Pereira; Egues, Silvia Maria da Silva; Freitas, Lisiane Dos Santos; Benvenutti, Edilson Valmir

2012-04-01

112

Influence of carboxyl group density on neuron cell attachment and differentiation behavior: gradient-guided neurite outgrowth.  

PubMed

A UV pre-irradiation step followed by a UV grafting step was used to graft poly(acrylic acid) (PAA) on polymeric substrates. These substrates were then used to investigate the influence of carboxyl groups (-COOH) on cell behavior. Both the attachment and differentiation behaviors of C17.2 cells showed a -COOH group density-dependent response. In order to achieve an even distribution of cells on a -COOH gradient surface for neuron differentiation studies, an Ar plasma post-treatment was applied to the PAA-grafted surfaces. It greatly improved the cell adhesion properties with little damage to -COOH groups. This allows uniform distributions of seeded cells even on substrates with -COOH gradients. A linear or stepped -COOH gradient was found to be capable of serving as a repelling cue to guide the outgrowth of neurites from C17.2 cells. Up to 3.7 times more cells developed neurites growing down the -COOH gradient than growing up it. PMID:15769531

Li, Bin; Ma, Yuexia; Wang, Shu; Moran, Peter M

2005-08-01

113

Comparison of methodologies for determination of carboxylic and phenolic groups in humic acids  

Microsoft Academic Search

A nonlinear method for fitting acid–base potentiometric titration data was applied to commercial and vermicompost humic acids in order to determine the concentration and conditional pKa's of the ionizable sites. Data was also treated by a linear method based on modified Gran functions. In both cases the discrete site model was adopted, which means that the humic acid was treated

Jorge C. Masini; Gilberto Abate; Elizabete C. Lima; Lucas C. Hahn; Mary S. Nakamura; Jaim Lichtig; Hélio R. Nagatomy

1998-01-01

114

Novel poly(arylene ether ketone)s containing sulfonic\\/carboxylic groups: Synthesis and properties  

Microsoft Academic Search

Novel poly(arylene ether ketone)s containing phenyl- and 4-cyanophenyl substituents were synthesized and subsequently used as starting material to prepare polymer electrolyte membranes for fuel cells application. FTIR and 1H NMR spectra indicated that both a sulfonation reaction on the pendant phenyl and a hydrolysis reaction on the cyano groups occurred simultaneously. After sulfonation\\/hydrolysis, flexible and transparent membranes with sulfonic and

Meimei Guo; Baijun Liu; Shaowei Guan; Chang Liu; Hongyi Qin; Zhenhua Jiang

2010-01-01

115

Theoretical study of the ionization potential of thymine : effect of adding conjugated functional groups.  

SciTech Connect

The ionization potential of thymine functionalized at the C5 position with the truncated linker groups, -CH=CHCO{sub 2}CH{sub 3} and -CH=CHCONHCH{sub 3}, was examined using density functional theory. Results indicate that the addition of the carboxyl group to thymine lowers the adiabatic ionization potential by 0.4 eV. Further, modification of the carboxyl group by an amino group lowers the ionization potential by another 0.2 eV. The effect of solvation and base pairing with adenine on the modified thymine ionization energies was also investigated. The results provide evidence that linker groups can dampen the influence of adenine base pairing on thymine charge transfer.

Vega-Arroyo, M.; LeBreton, P. R.; Rajh, T.; Zapol, P.; Curtiss, L.; Univ. of Illinois at Chicago

2003-01-01

116

Luminescence efficiency of aromatic carboxylates of europium and terbium when methylene bridges and nitro groups are present in the ligands  

NASA Astrophysics Data System (ADS)

We discuss the possibility of optimizing the brightness of luminescence for phenylcarboxylates, naphthylcarboxylates, and indolylcarboxylates of europium and terbium and their adducts with 1,10-phenanthroline and 2,2?-bipyridine by modifying the ligands. We have studied the efficiency of luminescence and luminescence excitation. We consider the effect of blocking energy transfer from the ligands to the Eu3+ and Tb3+ ions by methylene (-CH2-) bridges dividing the ?-electron system of the ligands into two parts and by the electronacceptor nitro group (-NO2). We have analyzed the pathways for transfer and degradation of the excitation energy at 77 K and 300 K. From the phosphorescence spectra of gadolinium salts, we have determined the energies of the lowest excited triplet states of the ligands. We consider the effect of the relative positions of the triplet levels of the ligands and the excited levels of the Eu3+ and Tb3+ ions on the luminescence efficiency. We found channels for dissipation of the excitation energy via the ??* and n?* states of the aromatic system of the carboxylate and the NO2 group.

Tsaryuk, V. I.; Zhuravlev, K. P.; Zolin, V. F.; Kudryashova, V. A.; Legendziewicz, J.; Szostak, R.

2007-01-01

117

Molecular characterization and functional analysis of novel carboxyl\\/cholinesterases with GQSAG motif in the silkworm Bombyx mori  

Microsoft Academic Search

We have previously cloned and characterized BmJHE, a juvenile hormone (JH)-selective esterase (JHE) that is important for JH titer regulation in the silkworm Bombyx mori. Here, we sought to determine whether multiple genes might function as JH-specific esterase in this species. We searched for putative carboxyl\\/cholinesterase (CCE) genes having GQSAG, a highly conserved motif in JHE, by the use of

Takuya Tsubota; Masaru Shimomura; Takehiko Ogura; Atsushi Seino; Takayo Nakakura; Kazuei Mita; Tetsuro Shinoda; Takahiro Shiotsuki

2010-01-01

118

Absolute p K a determination for carboxylic acids using density functional theory and the polarizable continuum model  

Microsoft Academic Search

The absolute pKas of eight carboxylic acids have been computed using a Born–Haber cycle, the most recent experimental value for the proton solvation energy and completely ab initio structures, energies, and harmonic frequencies of acids and conjugated bases both in vacuo and in aqueous solution. The proton affinities computed by the PBE0 hybrid functional are in very good agreement with

Gloria A. A. Saracino; Roberto Improta; Vincenzo Barone

2003-01-01

119

Computation of large systems with an economic basis set: a density functional study on proton-bound carboxylic acid clusters  

Microsoft Academic Search

We show that first-principle calculations with an economic basis set can predict reliable geometric structures and accurate vibrational frequencies for small proton-bound carboxylic acid clusters. This leads to the potential of using limited computational resources to study large molecular systems. Further applications using density functional (DFT) theory on a series of proton-bound formic and acetic acid clusters have found reasonable

R. Q Zhang; N. B Wong; S. T Lee; R. S Zhu; K. L Han

2000-01-01

120

The carboxyl terminus of Rtt109 functions in chaperone control of histone acetylation.  

PubMed

Rtt109 is a fungal histone acetyltransferase (HAT) that catalyzes histone H3 acetylation functionally associated with chromatin assembly. Rtt109-mediated H3 acetylation involves two histone chaperones, Asf1 and Vps75. In vivo, Rtt109 requires both chaperones for histone H3 lysine 9 acetylation (H3K9ac) but only Asf1 for full H3K56ac. In vitro, Rtt109-Vps75 catalyzes both H3K9ac and H3K56ac, whereas Rtt109-Asf1 catalyzes only H3K56ac. In this study, we extend the in vitro chaperone-associated substrate specificity of Rtt109 by showing that it acetylates vertebrate linker histone in the presence of Vps75 but not Asf1. In addition, we demonstrate that in Saccharomyces cerevisiae a short basic sequence at the carboxyl terminus of Rtt109 (Rtt109C) is required for H3K9ac in vivo. Furthermore, through in vitro and in vivo studies, we demonstrate that Rtt109C is required for optimal H3K56ac by the HAT in the presence of full-length Asf1. When Rtt109C is absent, Vps75 becomes important for H3K56ac by Rtt109 in vivo. In addition, we show that lysine 290 (K290) in Rtt109 is required in vivo for Vps75 to enhance the activity of the HAT. This is the first in vivo evidence for a role for Vps75 in H3K56ac. Taken together, our results contribute to a better understanding of chaperone control of Rtt109-mediated H3 acetylation. PMID:23457193

Radovani, Ernest; Cadorin, Matthew; Shams, Tahireh; El-Rass, Suzan; Karsou, Abdel R; Kim, Hyun-Soo; Kurat, Christoph F; Keogh, Michael-Christopher; Greenblatt, Jack F; Fillingham, Jeffrey S

2013-03-01

121

Anticancer potency of platinum(II) complexes containing both chloride anion and chelated carboxylate as leaving groups.  

PubMed

Three platinum complexes with both a chloride anion and a chelated carboxylate as leaving groups were synthesized and spectrally characterized. In vitro cytotoxicity of complexes 1-3 was evaluated against human A549, HCT-116, MCF-7, and HepG-2 tumor cell lines. The results showed that all the compounds exhibited effective cytotoxicity against the tested cell lines, nearly comparable to those of cisplatin and oxaliplatin. Notably, the activity of complex 2 was about 2-fold better than that of oxaliplatin against the HCT-116 cell line. Flow cytometry analysis indicated that these complexes produced death of tumor cells through an apoptotic pathway. The DNA-binding properties of the platinum-based compounds were also studied by agarose gel electrophoresis. The kinetics study showed that the chloride anion departs from the Pt atom quickly, whereas the five and/or six-membered ring formed by coordination of N,O-donors and the metal ion is opened a little more slowly by the rupture of a Pt-O bond, which helps us to further understand the mechanism of action of the newly synthesized complexes with biomolecules. Furthermore, the reaction rate constants of complexes 1-3 were roughly the same. PMID:23808547

Zhao, Jian; Gou, Shaohua; Liu, Fei; Sun, Yanyan; Gao, Chuanzhu

2013-06-28

122

Floral Benzenoid Carboxyl Methyltransferases: From in Vitro to in Planta Function  

SciTech Connect

Benzenoid carboxyl methyltransferases synthesize methyl esters (e.g., methyl benzoate and methyl salicylate), which are constituents of aromas and scents of many plant species and play important roles in plant communication with the surrounding environment. Within the past five years, eleven such carboxyl methyltransferases were isolated and most of them were comprehensively investigated at the biochemical, molecular and structural level. Two types of enzymes can be distinguished according to their substrate preferences: the SAMT-type enzymes isolated from Clarkia breweri, Stephanotis floribunda, Antirrhinum majus, Hoya carnosa, and Petunia hybrida, which have a higher catalytic efficiency and preference for salicylic acid, while BAMT-type enzymes from A. majus, Arabidopsis thaliana, Arabidopsis lyrata, and Nicotiana suaveolens prefer benzoic acid. The elucidation of C. breweri SAMT's three-dimensional structure allowed a detailed modelling of the active sites of the carboxyl methyltransferases and revealed that the SAM binding pocket is highly conserved among these enzymes while the methyl acceptor binding site exhibits some variability, allowing a classification into SAMT-type and BAMT-type enzymes. The analysis of expression patterns coupled with biochemical characterization showed that these carboxyl methyltransferases are involved either in floral scent biosynthesis or in plant defense responses. While the latter can be induced by biotic or abiotic stress, the genes responsible for floral scent synthesis exhibit developmental and rhythmic expression pattern. The nature of the product and efficiency of its formation in plants depend on the availability of substrates, the catalytic efficiency of the enzyme toward benzoic acid and/or salicylic acid, and the transcriptional, translational, and post-translational regulation at the enzyme level. The biochemical properties of benzenoid carboxyl methyltransferases suggest that the genes involved in plant defenses might represent the ancestor for the presently existing floral genes which during evolution gained different expression profiles and encoded enzymes with the ability to accept structurally similar substrates.

Effmert,U.; Saschenbrecker, S.; Ross, J.; Negre, F.; Fraser, C.; Noel, J.; Dudareva, N.; Piechulla, B.

2005-01-01

123

Fluorescence properties of dansyl groups covalently bonded to the surface of oxidatively functionalized low-density polyethylene film  

NASA Astrophysics Data System (ADS)

Brief oxidation of low-density polyethylene film with chromic acid in aqueous sulfuric acid introduced carboxylic acid and ketone and/or aldehyde groups onto the surface of the film. The carboxylic acid moieties can be used to attach more complex functionality to the polymer surface. We are developing this surface-functionalized polyethylene (named polyethylene carboxylic acid, PE-CO2H, to emphasize the functional group that dominates its surface properties) as a substrate with which to study problems in organic surface chemistry--especially wetting, polymer surface reconstruction, and adhesion--using physical-organic techniques. This document describes the preparation, characterization, and fluorescence properties of derivatives of PE-CO2H in which the Dansyl (5-dimethylaminonaphthalene-1-sulfonyl) group has been covalently attached by amide links to the surface carbonyl moieties.

Holmes-Farley, S. R.; Whitesides, G. M.

1985-12-01

124

Functional Reconstitution of the Integral Membrane Enzyme, Isoprenylcysteine Carboxyl Methyltransferase, in Synthetic Bolalipid Membrane Vesicles†  

PubMed Central

Three bipolar archaeal-type diglycerophosphocholine tetraether lipids (a.k.a., bolalipids) have been prepared to determine 1) the influence of molecular structure on the physical properties of bolalipid membranes and 2) their impact on the functional reconstitution of Ste14p, a membrane-associated isoprenylcysteine carboxyl methyltransferase from Saccharomyces cerevisiae. The three bolalipids synthesized were: C20BAS, C32BAS, and C32phytBAS. These bolalipid structures differ in that the C20BAS derivative has a short sn-1 glyceryl diether C20H40 transmembrane alkyl chain and two ether-linked sn-2 n-decyl chains, whereas the C32BAS and C32phytBAS derivatives have a longer sn-1 diether C32H64 membrane-spanning chain and two ether-linked sn-2 n-hexadecyl or phytanyl chains, respectively. Differential scanning calorimetry and temperature-dependent 31P NMR was used to determine the gel-to-liquid crystalline phase transition temperatures of the bolalipids (C32BAS Tm > 85 °C; C32phytBAS Tm = 14 °C; C20BAS Tm = 17°C). The bolalipid lateral diffusion coefficients, determined by fluorescence recovery after photobleaching at 20 °C, were 1.5 × 10?8 and 1.8 × 10?9 cm2/s for C20BAS and C32phytBAS, respectively. The mobility of C32BAS could not be measured at this temperature. Ste14p activity was monitored by an in vitro methyltransferase assay in reconstituted vesicle dispersions composed of DMPC, C20BAS:E. coli polar lipid, C20BAS:POPC, C32phytBAS:E. coli polar lipid, and C32phytBAS:POPC. Ste14p activity was lost in vesicles composed of 75–100 mol% C20BAS and 0–100 mol% C32BAS, but retained in vesicles with 0–50 mol% C20BAS and 0–100 mol% C32phytBAS. Confocal immunofluorescence microscopy confirmed the presence of Ste14p in 100 mol% C20BAS and 100 mol% C32phytBAS vesicle dispersions, even though the lamellar liquid crystalline phase thickness of C20BAS is only 32 Å. Since Ste14p activity was not affected by either the gel to liquid-crystal phase transition temperature of the lipid or the temperature of the assay, the low activity observed in 75–100 mol% C20BAS membranes can be attributed to hydrophobic mismatch between this bolalipid and the hydrophobic surface of Ste14p.

Febo-Ayala, Wilma; Morera-Felix, Shakira L.

2008-01-01

125

Novel vitamin D receptor ligands having a carboxyl group as an anchor to arginine 274 in the ligand-binding domain.  

PubMed

Vitamin D3 is metabolized into the hormonally active form, 1alpha,25-dihydroxyvitamin D3 (1), via 25-hydroxyvitamin D3 (2) which is the most abundant circulating metabolite. Introduction of the 1alpha-hydroxyl group into 25-hydroxyvitamin D3 (2) to produce 1alpha,25-dihydroxyvitamin D3 (1) increases the VDR binding affinity by approximately 1000-fold. The X-ray crystal structure of human VDR in complex with 1alpha,25-dihydroxyvitamin D3 (1) shows that, together with Ser-237, the 1alpha-hydroxyl group of 1alpha,25-dihydroxyvitamin D3 (1) makes hydrogen bonds with Arg-274, single mutation of which results in impaired ligand recognition. In 2002, lithocholic acid, which possesses a carboxyl group at position C24, was demonstrated to be a weak VDR ligand. We speculated that the carboxylic acid of lithocholic acid could be recognized by Arg-274 in the ligand-binding domain of VDR. In view of the significance of Arg-274 to direct the 1alpha-hydroxyl group, as well as the results with lithocholic acid and its derivatives, we designed the C2 modified analogues of 25-hydroxylvitamin D3 (2) having a carboxyl group, instead of the 1-hydroxyl group, for better electrostatic interaction to the guanidinium side-chain of arginine. PMID:20435140

Fujishima, Toshie; Tsuji, Genichiro; Tanaka, Chika; Harayama, Hiroshi

2010-05-06

126

Localization of functions defined on cantor group  

NASA Astrophysics Data System (ADS)

We introduce a notion of localization for dyadic functions, i. e. functions defined on Cantor group. Both non-periodic and periodic cases are discussed. Localization is characterized by functionals UCd and UCdp similar to the Heisenberg (the Breitenberger) uncertainty constants used for real-line (periodic) functions. We are looking for dyadic analogs of uncertainty principles. To justify definition we use some test functions including dyadic scaling and wavelet functions.

Krivoshein, Aleksander V.; Lebedeva, Elena A.

2013-10-01

127

Capping methotrexate ?-carboxyl groups enhances systemic exposure and retains the cytotoxicity of drug conjugated PEGylated polylysine dendrimers.  

PubMed

A generation 5 PEGylated (PEG 1100) polylysine dendrimer, conjugated via a stable amide linker to OtBu protected methotrexate (MTX), was previously shown to have a circulatory half-life of 2 days and to target solid tumors in both rats and mice. Here, we show that deprotection of MTX and substitution of the stable linker with a matrix metalloproteinase (MMP) 2 and 9 cleavable linker (PVGLIG) dramatically increased plasma clearance and promoted deposition in the liver and spleen (50-80% of the dose recovered in the liver 3 days post dose). Similar rapid clearance was also seen using a scrambled peptide suggesting that clearance was not dependent on the cleavable nature of the linker. Surprisingly, dendrimers where OtBu capped MTX was linked to the dendrimer surface via the hexapeptide linker showed equivalent in vitro cytotoxicity against HT1080 cells when compared to the uncapped dendrimer and also retained the long circulating characteristics of the stable constructs. The OtBu capped MTX conjugated dendrimer was subsequently shown to significantly reduce tumor growth in HT1080 tumor bearing mice compared to control. In contrast the equivalent dendrimer comprising uncapped MTX conjugated to the dendrimer via the same hexapeptide linker did not reduce tumor growth, presumably reflecting very rapid clearance of the construct. The results are consistent with the suggestion that protection of the ?-carboxyl group of methotrexate may be used to improve the circulatory half-life and reduce the liver accumulation of similar MTX-conjugated dendrimers, while still retaining antitumor activity in vivo. PMID:21171585

Kaminskas, Lisa M; Kelly, Brian D; McLeod, Victoria M; Sberna, Gian; Boyd, Ben J; Owen, David J; Porter, Christopher J H

2011-01-21

128

Relating Functional Groups to the Periodic Table  

ERIC Educational Resources Information Center

|An introduction to organic chemistry functional groups and their ionic variants is presented. Functional groups are ordered by the position of their specific (hetero) atom in the periodic table. Lewis structures are compared with their corresponding condensed formulas. (Contains 5 tables.)|

Struyf, Jef

2009-01-01

129

Adsorption of Cu(II) to ferrihydrite and ferrihydrite-bacteria composites: Importance of the carboxyl group for Cu mobility in natural environments  

NASA Astrophysics Data System (ADS)

Bacterially associated iron (hydr)oxide composites are widespread in natural environments, and by analogy with isolated iron (hydr)oxides and bacteria, are important scavengers of dissolved trace-metals. We precipitated ferrihydrite via rapid Fe(III) hydrolysis in the absence and presence of the non-Fe metabolising, Gram-positive bacterium Bacillus subtilis, commonly found in natural waters, soils and sediments. We combined XRD, SEM, BET and Fe K-edge EXAFS to examine the mineralogy, morphology and crystallinity of the ferrihydrite composites. We find that the mineral fraction of the composites is unaltered in primary mineralogy, morphology and crystallinity compared to pure ferrihydrite. We then measured the adsorption of Cu to ferrihydrite and the ferrihydrite-B. subtilis composites as a function of pH and the ferrihydrite:bacteria mass ratio of the composites, and used EXAFS to determine the molecular mechanisms of Cu adsorption. We determine directly for the first time that Cu uptake by ferrihydrite-B. subtilis composites is the result of adsorption to both the ferrihydrite and B. subtilis fractions. Adsorption of Cu by the B. subtilis fraction results in significant Cu uptake in the low pH regime (pH ˜4, ˜20% of [Cu]total) and significantly enhanced Cu uptake in the mid pH regime. This composite sorption behaviour is in stark contrast to pure ferrihydrite, where Cu adsorption is negligible at low pH. Overall, for composites dominated by either ferrihydrite or B. subtilis, the bacterial fraction is exclusively responsible for Cu adsorption at low pH while the ferrihydrite fraction is predominantly responsible for adsorption at high pH. Furthermore, with an increased mass ratio of bacteria, the dominance of Cu adsorption to the bacterial fraction persists into the mid pH regime and extends significantly into the upper pH region. As such, the distribution of the total adsorbed Cu between the composite fractions is a function of both pH and the ferrihydrite:bacteria mass ratio of the composite. EXAFS shows that Cu adsorbs to ferrihydrite as an inner-sphere, (CuO4Hn)n - 6 bidentate edge-sharing complex; and to ferrihydrite composites as an inner-sphere, (CuO5Hn)n - 8 monodentate complex with carboxyl surface functional groups present on the bacterial fraction plus the bidentate edge-sharing complex on the ferrihydrite fraction. Our new results combined with previous work on Cu sorption to bacteria, humic substances and iron (hydr)oxides coated with humics, demonstrate the universal importance of the carboxyl moiety for Cu sorption and mobility in natural environments. Taken together these results show that Cu-carboxyl binding is the predominant mechanism by which Cu interacts with abiotic and biotic organic matter, and provides a ubiquitous control on Cu fate and mobility in natural waters, soils and sediments. Our results indicate that in environments where a significant proportion of iron (hydr)oxides are intimately intermixed with an organic fraction, we must consider Cu sequestration by these composites in addition to pure mineral phases.

Moon, Ellen M.; Peacock, Caroline L.

2012-09-01

130

An ultra sensitive saccharides detection assay using carboxyl functionalized chitosan containing Gd2O3: Eu3+ nanoparticles probe  

Microsoft Academic Search

A novel saccharides detection assay based on covalent immobilization of\\u000a amino phenyl boronic acid (APBA) in thin films of carboxyl\\u000a functionalized chitosan (HOOC-chitosan) containing 5 nm Gd2O3 : Eu3+\\u000a nanoparticles at a platinum disc electrode was developed. The resulting\\u000a HOOC-chitosan\\/Gd2O3 : Eu3+ nanocomposite film exhibited excellent\\u000a electrochemical response to changes in the pK(a) values of boronate\\u000a esters yielded from different

Ashutosh Tiwari; Dohiko Terada; Prashant K. Sharma; Vyom Parashar; Chiaki Yoshikawa; Avinash C. Pandey; Hisatoshi Kobayashi

2011-01-01

131

The central role of ketones in reversible and irreversible hydrothermal organic functional group transformations  

NASA Astrophysics Data System (ADS)

Studies of hydrothermal reactions involving organic compounds suggest complex, possibly reversible, reaction pathways that link functional groups from reduced alkanes all the way to oxidized carboxylic acids. Ketones represent a critical functional group because they occupy a central position in the reaction pathway, at the point where Csbnd C bond cleavage is required for the formation of the more oxidized carboxylic acids. The mechanisms for the critical bond cleavage reactions in ketones, and how they compete with other reactions are the focus of this experimental study. We studied a model ketone, dibenzylketone (DBK), in H2O at 300 °C and 70 MPa for up to 528 h. Product analysis was performed as a function of time at low DBK conversions to reveal the primary reaction pathways. Reversible interconversion between ketone, alcohol, alkene and alkane functional groups is observed in addition to formation of radical coupling products derived from irreversible Csbnd C and Csbnd H homolytic bond cleavage. The product distributions are time-dependent but the bond cleavage products dominate. The major products that accumulate at longer reaction times are toluene and larger, dehydrogenated structures that are initially formed by radical coupling. The hydrogen atoms generated by dehydrogenation of the coupling products are predominantly consumed in the formation of toluene. Even though bond cleavage products dominate, no carboxylic acids were observed on the timescale of the reactions under the chosen experimental conditions.

Yang, Ziming; Gould, Ian R.; Williams, Lynda B.; Hartnett, Hilairy E.; Shock, Everett L.

2012-12-01

132

Protonation States of Membrane-Embedded Carboxylic Acid Groups in Rhodopsin and Metarhodopsin II: A FourierTransform Infrared Spectroscopy Study of Site-Directed Mutants  

Microsoft Academic Search

A method was developed to measure Fourier-transform infrared (FTIR) difference spectra of detergent-solubilized rhodopsin expressed in COS cells. Experiments were performed on native bovine rhodopsin, rhodopsin expressed in COS cells, and three expressed rhodopsin mutants with amino acid replacements of membrane-embedded carboxylic acid groups: Asp-83 --> Asn (D83N), Glu-122 --> Gln (E122Q), and the double mutant D83N\\/E122Q. Each of the

Karim Fahmy; Frank Jager; Mareike Beck; Tatyana A. Zvyaga; Thomas P. Sakmar; Friedrich Siebert

1993-01-01

133

Synthesis, Aqueous Reactivity, and Biological Evaluation of Carboxylic Acid Ester-Functionalized Platinum-Acridine Hybrid Anticancer Agents  

PubMed Central

The synthesis of platinum–acridine hybrid agents containing carboxylic acid ester groups is described. The most active derivatives and the unmodified parent compounds showed up to 6-fold higher activity in ovarian cancer (OVCAR-3) and breast cancer (MCF-7, MDA-MB-23) cell lines than cisplatin. Inhibition of cell proliferation at nanomolar concentrations was observed in pancreatic (PANC-1) and non-small cell lung cancer cells (NSCLC, NCI-H460) of 80- and 150-fold, respectively. Introduction of the ester groups did not affect the cytotoxic properties of the hybrids, which form the same monofunctional–intercalative DNA adducts as the parent compounds, as demonstrated in a plasmid unwinding assay. In-line high-performance liquid chromatography and electrospray mass spectrometry (LC-ESMS) shows that the ester moieties undergo platinum-mediated hydrolysis in a chloride concentration-dependent manner to form carboxylate chelates. Potential applications of the chloride-sensitive ester hydrolysis as a self-immolative release mechanism for tumor-selective delivery of platinum–acridines are discussed.

Graham, Leigh A.; Suryadi, Jimmy; West, Tiffany K.; Kucera, Gregory L.; Bierbach, Ulrich

2012-01-01

134

Synthesis, aqueous reactivity, and biological evaluation of carboxylic acid ester-functionalized platinum-acridine hybrid anticancer agents.  

PubMed

The synthesis of platinum-acridine hybrid agents containing carboxylic acid ester groups is described. The most active derivatives and the unmodified parent compounds showed up to 6-fold higher activity in ovarian cancer (OVCAR-3) and breast cancer (MCF-7, MDA-MB-231) cell lines than cisplatin. Inhibition of cell proliferation at nanomolar concentrations was observed in pancreatic (PANC-1) and nonsmall cell lung cancer cells (NSCLC, NCI-H460) of 80- and 150-fold, respectively. Introduction of the ester groups did not affect the cytotoxic properties of the hybrids, which form the same monofunctional-intercalative DNA adducts as the parent compounds, as demonstrated in a plasmid unwinding assay. In-line high-performance liquid chromatography and electrospray mass spectrometry (LC-ESMS) shows that the ester moieties undergo platinum-mediated hydrolysis in a chloride concentration-dependent manner to form carboxylate chelates. Potential applications of the chloride-sensitive ester hydrolysis as a self-immolative release mechanism for tumor-selective delivery of platinum-acridines are discussed. PMID:22871158

Graham, Leigh A; Suryadi, Jimmy; West, Tiffany K; Kucera, Gregory L; Bierbach, Ulrich

2012-08-17

135

Analytical methodology for determination of organic aerosol functional group distributions.  

PubMed

Secondary organic aerosol (SOA) particles result from the condensation of oxidized volatile organic compounds (VOC) and consist of a complex mixture that is not conducive to complete compositional analysis. We present a simple methodology for determining the quantities of aldehydes and ketones, alcohols, and carboxylic acids in such samples via derivatization and high-performance liquid chromatography (HPLC) with ultraviolet-visible absorption detection and tandem mass spectrometry (MS/MS). Useful concentration ranges are presented with an examination of the specificity of these compounds in multiply substituted systems. Such data are valuable in modeling the formation of laboratory-generated aerosols and in identifying point sources of field-collected aerosol samples. Calibration curves on standard samples, MS/MS transitions, including collisionally induced dissociation (CID) products, and a quantitative examination of the specificity of the derivatization reagents toward multiple functional groups are presented for a series of aliphatic standard samples. These methods are then applied to filter extracts from SOA derived from 1-iodooctane photolysis at 254 nm to demonstrate the methodology on a complex system. Ultimately, this methodology enables the measurement of variations in the chemical nature of the oxygen within an SOA particle, providing a distribution of functional group concentrations. PMID:23461576

Kalafut-Pettibone, Alicia J; McGivern, W Sean

2013-03-22

136

Identifying organic aerosol sources by comparing functional group composition in chamber and atmospheric particles  

PubMed Central

Measurements of submicron particles by Fourier transform infrared spectroscopy in 14 campaigns in North America, Asia, South America, and Europe were used to identify characteristic organic functional group compositions of fuel combustion, terrestrial vegetation, and ocean bubble bursting sources, each of which often accounts for more than a third of organic mass (OM), and some of which is secondary organic aerosol (SOA) from gas-phase precursors. The majority of the OM consists of alkane, carboxylic acid, hydroxyl, and carbonyl groups. The organic functional groups formed from combustion and vegetation emissions are similar to the secondary products identified in chamber studies. The near absence of carbonyl groups in the observed SOA associated with combustion is consistent with alkane rather than aromatic precursors, and the absence of organonitrate groups can be explained by their hydrolysis in humid ambient conditions. The remote forest observations have ratios of carboxylic acid, organic hydroxyl, and nonacid carbonyl groups similar to those observed for isoprene and monoterpene chamber studies, but in biogenic aerosols transported downwind of urban areas the formation of esters replaces the acid and hydroxyl groups and leaves only nonacid carbonyl groups. The carbonyl groups in SOA associated with vegetation emissions provides striking evidence for the mechanism of esterification as the pathway for possible oligomerization reactions in the atmosphere. Forest fires include biogenic emissions that produce SOA with organic components similar to isoprene and monoterpene chamber studies, also resulting in nonacid carbonyl groups in SOA.

Russell, Lynn M.; Bahadur, Ranjit; Ziemann, Paul J.

2011-01-01

137

Synergistic effect of self-assembled carboxylic acid-functionalized carbon nanotubes and carbon fiber for improved electro-activated polymeric shape-memory nanocomposite  

NASA Astrophysics Data System (ADS)

The present work studies the synergistic effect of self-assembled carboxylic acid-functionalized carbon nanotube (CNT) and carbon fiber on the electrical property and electro-activated recovery behavior of shape memory polymer (SMP) nanocomposites. The combination of CNT and carbon fiber results in improved electrical conductivity in the SMP nanocomposites. Carboxylic acid-functionalized CNTs are grafted onto the carbon fibers and then self-assembled by deposition to significantly enhance the reliability of the bonding between carbon fiber and SMP via van der Waals and covalent crosslink. Furthermore, the self-assembled carboxylic acid-functionalized CNTs and carbon fibers enable the SMP nanocomposites for Joule heating triggered shape recovery.

Lu, Haibao; Min Huang, Wei

2013-06-01

138

Aqueous infrared carboxylate absorbances: Aliphatic di-acids  

USGS Publications Warehouse

Aqueous attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectra of 18 aliphatic di-carboxylic acids are reported as a function of pH. The spectra show isosbestic points and intensity changes which indicate that Beer's law is obeyed, and peak frequencies lie within previously reported ranges for aqueous carboxylates and pure carboxylic acids. Intensity sharing from the symmetric carboxylate stretch is evident in many cases, so that bands which are nominally due to alkyl groups show increased intensity at higher pH. The asymmetric stretch of the HA- species is linearly related to the microscopic acidity constant of the H2A species, with ??pK 2 intervening atoms). The results suggest that aqueous ATR-FTIR may be able to estimate 'intrinsic' pKa values of carboxylic acids, in addition to providing quantitative estimates of ionization. ?? 1998 Elsevier Science B.V. All rights reserved.

Cabaniss, S. E.; Leenheer, J. A.; McVey, I. F.

1998-01-01

139

Ising exponents from the functional renormalization group  

SciTech Connect

We study the 3d Ising universality class using the functional renormalization group. With the help of background fields and a derivative expansion up to fourth order we compute the leading index, the subleading symmetric and antisymmetric corrections to scaling, the anomalous dimension, the scaling solution, and the eigenperturbations at criticality. We also study the cross correlations of scaling exponents, their dependence on dimensionality, and the numerical convergence of the derivative expansion. Collecting all available data from functional renormalization group studies to date, we estimate that systematic errors are in good agreement with findings from Monte Carlo simulations, {epsilon}-expansion techniques, and resummed perturbation theory.

Litim, Daniel F. [Department of Physics and Astronomy, University of Sussex, BN1 9QH, Brighton (United Kingdom); Zappala, Dario [INFN, Sezione di Catania, 64 via S. Sofia, I-95123, Catania (Italy)

2011-04-15

140

Self-assembly of amphiphilic homopolymers bearing ferrocene and carboxyl functionalities: effect of polymer concentration, ?-cyclodextrin, and length of alkyl linker.  

PubMed

Three new acrylamide monomers containing ferrocene and tert-butyl ester groups were first synthesized via multistep nucleophilic substitution reaction under mild conditions followed by reversible addition-fragmentation chain transfer (RAFT) homopolymerization to give well-defined homopolymers with narrow molecular weight distributions (M(w)/M(n) ? 1.36). The target amphiphilic homopolymers were obtained by the acidic hydrolysis of tert-butyoxycarbonyls to carboxyls in every repeating unit using CF3COOH. The self-assembly behaviors of these amphiphilic homopolymers bearing both ferrocene and carboxyl moieties in each repeating unit in aqueous media were investigated by transmission emission microscopy (TEM), dynamic light scattering (DLS), and atomic force microscopy (AFM). Large compound micelles with different morphologies were formed by these amphiphilic homopolymers, which consist of the corona formed by hydrophilic carboxyls and the core containing numerous reverse micelles with hydrophilic islands of carboxyls in continuous hydrophobic phase of ferrocene-based segments. The morphologies of the formed micelles could be tuned by the concentration of amphiphilic homopolymers, pH value of the solution, the length of -CH2 linker between ferrocene group and carboxyl, and the amount of ?-cyclodextrin (?-CD). PMID:23977901

Feng, Chun; Lu, Guolin; Li, Yongjun; Huang, Xiaoyu

2013-08-12

141

Functions of Reported Speech in Group Discussions.  

ERIC Educational Resources Information Center

|Proposes a taxonomy of functions for direct reports of speech (and of writing and thought) in focus-group discussions. Reported speech both depicts the experience of the original utterance and detaches the reported utterance from the reporting speaker. (Author/VWL)|

Myers, Greg

1999-01-01

142

Chemistry and reactivity of carboxylic acid-containing surfaces  

Microsoft Academic Search

Polymer surface modification techniques, such as corona, plasma, and ultraviolet treatments, promote adhesion to polymer surfaces through introduction of specific functional groups that interact with subsequent coating layers. Carboxylic acid groups formed during corona and plasma treatments may play a significant role in adhesion promotion, so such groups have been chosen for model surface chemistry studies. Thin films (<30 nm)

C. A. Fleischer; W. P. McKenna; G. Apai

1996-01-01

143

Molecular characterization and functional analysis of novel carboxyl/cholinesterases with GQSAG motif in the silkworm Bombyx mori.  

PubMed

We have previously cloned and characterized BmJHE, a juvenile hormone (JH)-selective esterase (JHE) that is important for JH titer regulation in the silkworm Bombyx mori. Here, we sought to determine whether multiple genes might function as JH-specific esterase in this species. We searched for putative carboxyl/cholinesterase (CCE) genes having GQSAG, a highly conserved motif in JHE, by the use of silkworm genomic database. Five novel CCE genes (Bmcce-1-5) were identified and their cDNA sequences and intron-exon structures were determined. We investigated the developmental expression patterns of these CCE genes by real-time quantitative PCR analysis and found that their expression patterns varied among developmental stages and organs. Of the proteins produced by the five genes, only BmCCE-5 had the ability to degrade JH; however, this protein might not function as a JH-specific esterase in vivo as it had a high K(m) value for JH. On the other hand, BmCCE-5 degraded general esterase substrates efficiently. Since Bmcce-5 was strongly expressed in Malpighian tubules and the gut, it might function in digestion or xenobiotic metabolism. Our results suggest that of the CCEs containing a GQSAG motif only BmJHE can function as a JH-specific degradation enzyme in the silkworm. PMID:20060470

Tsubota, Takuya; Shimomura, Masaru; Ogura, Takehiko; Seino, Atsushi; Nakakura, Takayo; Mita, Kazuei; Shinoda, Tetsuro; Shiotsuki, Takahiro

2010-01-07

144

Introduction to the nonequilibrium functional renormalization group  

NASA Astrophysics Data System (ADS)

In these lectures we introduce the functional renormalization group out of equilibrium. While in thermal equilibrium typically a Euclidean formulation is adequate, nonequilibrium properties require real-time descriptions. For quantum systems specified by a given density matrix at initial time, a generating functional for real-time correlation functions can be written down using the Schwinger-Keldysh closed time path. This can be used to construct a nonequilibrium functional renormalization group along similar lines as for Euclidean field theories in thermal equilibrium. Important differences include the absence of a fluctuation-dissipation relation for general out-of-equilibrium situations. The nonequilibrium renormalization group takes on a particularly simple form at a fixed point, where the corresponding scale-invariant system becomes independent of the details of the initial density matrix. We discuss some basic examples, for which we derive a hierarchy of fixed point solutions with increasing complexity from vacuum and thermal equilibrium to nonequilibrium. The latter solutions are then associated to the phenomenon of turbulence in quantum field theory.

Berges, J.; Mesterházy, D.

2012-07-01

145

Formation of porphyrin donor-acceptor complexes via an amidinium-carboxylate salt bridge  

Microsoft Academic Search

Porphyrins have been modified with an amidine functional group and they have been shown to bind carboxylic acids to form a amidinium-carboxylate salt bridge. These systems offer a new model to probe the mechanism of proton-coupled electron transfer (PCET).

James P. Kirby; Niels A. van Dantzig; Chi K. Chang; Daniel G. Nocera

1995-01-01

146

Silver(I)-catalyzed carboxylation of arylboronic esters with CO2.  

PubMed

A variety of arylboronic esters were efficiently carboxylated with CO(2) using a simple AgOAc/PPh(3) catalyst, affording the corresponding carboxylic acids in good yield. This simple and efficient silver(i) catalytic system showed wide functional group compatibility. PMID:22595884

Zhang, Xiao; Zhang, Wen-Zhen; Shi, Ling-Long; Guo, Chun-Xiao; Zhang, Ling-Ling; Lu, Xiao-Bing

2012-05-18

147

Water Soluble Metallo-Phthalocyanines: The Role of the Functional Groups on the Spectral and Photophysical Properties  

Microsoft Academic Search

Strategies are reported that produce symmetrical metal-free and metallo-phthalocyanine dyes, Pc and MPc, respectively, containing\\u000a various numbers of water solubilizing carboxylic acid groups on their periphery that provide a dual role by also serving as\\u000a functional groups to covalently link primary amine-containing targets to these dyes. In order to induce water compatibility\\u000a and to minimize the degree of aggregation, the

Vera T. Verdree; Serhii Pakhomov; Guifa Su; Michael W. Allen; Amber C. Countryman; Robert P. Hammer; Steven A. Soper

2007-01-01

148

Ubiquitin carboxyl-terminal hydrolase L1 is required for maintaining the structure and function of the neuromuscular junction  

PubMed Central

The enzyme ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1) is one of the most abundant proteins in the mammalian nervous system. In humans, UCH-L1 is also found in the ubiquitinated inclusion bodies that characterize neurodegenerative diseases in the brain, suggesting its involvement in neurodegeneration. The physiologic role of UCH-L1 in neurons, however, remains to be further elucidated. For example, previous studies have provided evidence both for and against the role of UCH-L1 in synaptic function in the brain. Here, we have characterized a line of knockout mice deficient in the UCH-L1 gene. We found that, in the absence of UCH-L1, synaptic transmission at the neuromuscular junctions (NMJs) is markedly impaired. Both spontaneous and evoked synaptic activity are reduced; paired pulse-facilitation is impaired, and synaptic transmission fails to respond to high-frequency, repetitive stimulation at the NMJs of UCH-L1 knockout mice. Morphologic analyses of the NMJs further revealed profound structural defects—loss of synaptic vesicles and accumulation of tubulovesicular structures at the presynaptic nerve terminals, and denervation of the muscles in UCH-L1 knockout mice. These findings demonstrate that UCH-L1 is required for the maintenance of the structure and function of the NMJ and that the loss of normal UCH-L1 activity may result in neurodegeneration in the peripheral nervous system.

Chen, Fujun; Sugiura, Yoshie; Myers, Kalisa Galina; Liu, Yun; Lin, Weichun

2010-01-01

149

Facile regio- and stereoselective hydrometalation of alkynes with a combination of carboxylic acids and group 10 transition metal complexes: selective hydrogenation of alkynes with formic acid.  

PubMed

A facile, highly stereo- and regioselective hydrometalation of alkynes generating alkenylmetal complex is disclosed for the first time from a reaction of alkyne, carboxylic acid, and a zerovalent group 10 transition metal complex M(PEt(3))(4) (M = Ni, Pd, Pt). A mechanistic study showed that the hydrometalation does not proceed via the reaction of alkyne with a hydridometal generated by the protonation of a carboxylic acid with Pt(PEt(3))(4), but proceeds via a reaction of an alkyne coordinate metal complex with the acid. This finding clarifies the long proposed reaction mechanism that operates via the generation of an alkenylpalladium intermediate and subsequent transformation of this complex in a variety of reactions catalyzed by a combination of Br?nsted acid and Pd(0) complex. This finding also leads to the disclosure of an unprecedented reduction of alkynes with formic acid that can selectively produce cis-, trans-alkenes and alkanes by slightly tuning the conditions. PMID:21916436

Shen, Ruwei; Chen, Tieqiao; Zhao, Yalei; Qiu, Renhua; Zhou, Yongbo; Yin, Shuangfeng; Wang, Xiangbo; Goto, Midori; Han, Li-Biao

2011-09-29

150

A Functionally Diverse Enzyme Superfamily that Abstracts the alpha Protons of Carboxylic Acids  

Microsoft Academic Search

Mandelate racemase and muconate lactonizing enzyme are structurally homologous but catalyze different reactions, each initiated by proton abstraction from carbon. The structural similarity to mandelate racemase of a previously unidentified gene product was used to deduce its function as a galactonate dehydratase. In this enzyme superfamily that has evolved to catalyze proton abstraction from carbon, three variations of homologous active

Patricia Clement Babbitt; Gregory T. Mrachko; Miriam Sarah Hasson; Gjalt W. Huisman; Roberto Kolter; Dagmar Ringe; Gregory A. Petsko; George L. Kenyon; John A. Gerlt

1995-01-01

151

Simultaneous determination of interfacial molarities of amide bonds, carboxylate groups, and water by chemical trapping in micelles of amphiphiles containing peptide bond models.  

PubMed

Chemical trapping is a powerful approach for obtaining experimental estimates of interfacial molarities of weakly basic nucleophiles in the interfacial regions of amphiphile aggregates. Here, we demonstrate that the chemical probe 4-hexadecyl-2,6-dimethylbenzenediazonium ion (16-ArN(2)(+)) reacts competitively with interfacial water, with the amide carbonyl followed by cleavage of the headgroups from the tail at the amide oxygen, and with the terminal carboxylate groups in micelles of two N-acyl amino-acid amphiphiles, sodium N-lauroylsarcosinate (SLS) and sodium N-lauroylglycinate (SLG), simple peptide bond model amphiphiles. Interfacial molarities (in moles per liter of interfacial volume) of these three groups were obtained from product yields, assuming that selectivity toward a particular nucleophile compared to water is the same in an aqueous reference solution and in the interfacial region. Interfacial carboxylate group molarities are ~1.5 M in both SLS and SLG micelles, but the concentration of the amide carbonyl for SLS micelles is ~4.6-5 times less (ca. 0.7 M) than that of SLG micelles (~3 M). The proton on the secondary N of SLG helps solubilize the amide bond in the aqueous region, but the methyl on the tertiary N of SLS helps solubilize the amide bond in the micellar core, reducing its reaction with 16-ArN(2)(+). Application of chemical trapping to proteins in membrane mimetic interfaces should provide insight into the topology of the protein within the interface because trapping of the amide carbonyl and cleavage at the C-N bond occurs only within the interface, and fragment characterization marks those peptide bonds located within the interface. PMID:23237147

Zhang, Yongliang; Romsted, Laurence S; Zhuang, Lanzhen; de Jong, Sander

2012-12-31

152

Functional renormalization group with a compactly supported smooth regulator function  

NASA Astrophysics Data System (ADS)

The functional renormalization group equation with a compactly supported smooth (CSS) regulator function is considered. It is demonstrated that in an appropriate limit the CSS regulator recovers the optimized one and it has derivatives of all orders. The more generalized form of the CSS regulator is shown to reduce to all major type of regulator functions (exponential, power-law) in appropriate limits. The CSS regulator function is tested by studying the critical behavior of the bosonized two-dimensional quantum electrodynamics in the local potential approximation and the sine-ordon scalar theory for d < 2 dimensions beyond the local potential approximation. It is shown that a similar smoothing problem in nuclear physics has already been solved by introducing the so called Salamon-Vertse potential which can be related to the CSS regulator.

Nándori, I.

2013-04-01

153

Ultracold atoms and the Functional Renormalization Group  

NASA Astrophysics Data System (ADS)

We give a self-contained introduction to the physics of ultracold atoms using functional integral techniques. Based on a consideration of the relevant length scales, we derive the universal effective low energy Hamiltonian describing ultracold alkali atoms. We then introduce the concept of the effective action, which generalizes the classical action principle to full quantum status and provides an intuitive and versatile tool for practical calculations. This framework is applied to weakly interacting degenerate bosons and fermions in the spatial continuum. In particular, we discuss the related BEC and BCS quantum condensation mechanisms. We then turn to the BCS-BEC crossover, which interpolates between both phenomena, and which is realized experimentally in the vicinity of a Feshbach resonance. For its description, we introduce the Functional Renormalization Group approach. After a general discussion of the method in the cold atoms context, we present a detailed and pedagogical application to the crossover problem. This not only provides the physical mechanism underlying this phenomenon. More generally, it also reveals how the renormalization group can be used as a tool to capture physics at all scales, from few-body scattering on microscopic scales, through the finite temperature phase diagram governed by many-body length scales, up to critical phenomena dictating long distance physics at the phase transition.The presentation aims to equip students at the beginning PhD level with knowledge on key physical phenomena and flexible tools for their description, and should enable to embark upon practical calculations in this field.

Boettcher, Igor; Pawlowski, Jan M.; Diehl, Sebastian

2012-07-01

154

8-aminoquinoline: a powerful directing group in metal-catalyzed direct functionalization of c?h bonds.  

PubMed

Chelate me if you can: Over the last decade, strategies for the functionalization of both C?sp?2?H and C?sp?3?H bonds have witnessed an increasing use of a simple, yet powerful directing group, 8-aminoquinoline (in blue). This auxiliary is very efficient in a wide range of metal-mediated reactions, and can be readily removed to afford the desired carboxylic acids or corresponding derivatives. PMID:23939922

Corbet, Matthieu; De Campo, Floryan

2013-08-12

155

In vitro pollen functionality of attacin-transgenic “Royal Gala” apple plants and apples transformed with 1-aminocyclopropane-1-carboxylic acid synthase (ACS)-antisense vector  

Microsoft Academic Search

To assess pollen functionality of transgenic apple trees, in vitro pollen germination and tube growth were evaluated. Flowers of transgenic “Royal Gala” apple lines containing attacin E gene to confer resistance to fire blight (Erwinia amylovora), or antisense 1-aminocyclopropane-1-carboxylic acid synthase (ACS) construct to improve fruit storage life, were collected, and pollen was harvested. Amongst the 19 transgenic lines, pollen from

K. Ko; S. K. Brown; J. L. Norelli; G. Hrazdina; H. S. Aldwinckle

2010-01-01

156

Self-assembled thiol monolayers with carboxylic acid functionality: Measuring pH-dependent phase transitions with the quartz crystal microbalance  

SciTech Connect

The resonant frequency of the quartz crystal microbalance (QCM) coated with self-assembled thiol monolayers with carboxylic acid functionality is measured while the pH of the aqueous solvent is changed in this paper. Increased tensile stress with increasing pH activity partially contributed to the QCM response, but the major contribution was due to changes in the viscoelastic properties of the hydrodynamic layer in contact with the QCM. 28 refs., 3 figs.

Wang, J.; Frostman, L.M.; Ward, M.D. [Univ. of Minnesota, Minneapolis, MN (United States)]|[Center for Interfacial Engineering, Minneapolis, MN (United States)

1992-06-25

157

Glioma cell line proliferation controlled by different chemical functional groups in vitro  

NASA Astrophysics Data System (ADS)

Glioma cell line C6 cultured on silicon surfaces modified by different chemical functional groups, including mercapto (-SH), carboxyl (-COOH), amino (-NH2), hydroxyl (-OH) and methyl (-CH3) groups, was studied here to investigate the influence of surface chemistry on the cell proliferation, adhesion and apoptosis. AFM confirmed the similar characteristic of different functional groups occupation. The adhering C6 exhibited morphological changes in response to different chemical functional groups. The C6 adhered to -COOH, -NH2, -OH and -CH3 surfaces and flattened morphology, while those on -SH surface exhibited the smallest contact area with mostly rounded morphology, which led to the death of cancer cells. The results of MTT assay showed that the -COOH and -NH2 groups promoted cell proliferation, while the -SH significantly inhibited the proliferation. Compared with other chemical functional groups, the -SH group exhibited its unique effect on the fate of cancer cells, which might provide means for the design of biomaterials to prevent and treat glioma.

Xu, Su-Ju; Cui, Fu-Zhai; Yu, Xiao-Long; Kong, Xiang-Dong

2013-03-01

158

Linking of Sensor Molecules with Amino Groups to Amino-Functionalized AFM Tips  

PubMed Central

The measuring tip of an atomic force microscope (AFM) can be upgraded to a specific biosensor by attaching one or a few biomolecules to the apex of the tip. The biofunctionalized tip is then used to map cognate target molecules on a sample surface or to study biophysical parameters of interaction with the target molecules. The functionality of tip-bound sensor molecules is greatly enhanced if they are linked via a thin, flexible polymer chain. In a typical scheme of tip functionalization, reactive groups are first generated on the tip surface, a bifunctional cross-linker is then attached with one of its two reactive ends, and finally the probe molecule of interest is coupled to the free end of the cross-linker. Unfortunately, the most popular functional group generated on the tip surface is the amino group, while at the same time, the only useful coupling functions of many biomolecules (such as antibodies) are also NH2 groups. In the past, various tricks or detours were applied to minimize the undesired bivalent reaction of bifunctional linkers with adjacent NH2 groups on the tip surface. In the present study, an uncompromising solution to this problem was found with the help of a new cross-linker (“acetal-PEG-NHS”) which possesses one activated carboxyl group and one acetal-protected benzaldehyde function. The activated carboxyl ensures rapid unilateral attachment to the amino-functionalized tip, and only then is the terminal acetal group converted into the amino-reactive benzaldehyde function by mild treatment (1% citric acid, 1–10 min) which does not harm the AFM tip. As an exception, AFM tips with magnetic coating become demagnetized in 1% citric acid. This problem was solved by deprotecting the acetal group before coupling the PEG linker to the AFM tip. Bivalent binding of the corresponding linker (“aldehyde-PEG-NHS”) to adjacent NH2 groups on the tip was largely suppressed by high linker concentrations. In this way, magnetic AFM tips could be functionalized with an ethylene diamine derivative of ATP which showed specific interaction with mitochondrial uncoupling protein 1 (UCP1) that had been purified and reconstituted in a mica-supported planar lipid bilayer.

2011-01-01

159

17 O Quadrupole Coupling and Chemical Shielding Tensors in an H-bonded Carboxyl Group:  ?-Oxalic Acid  

Microsoft Academic Search

We have used single crystal 17 O NMR and density functional theory to investigate intermolecular interactions in a strongly H-bonded system. The chemical shielding (CS) and quadrupole coupling (QC) tensors are determined in oxalic acid dihydrate by single crystal methods. With cross polarization from abundant protons, high quality spectra are obtained in 1-2 min from 10 Ìmol samples. In the

Qianwen Zhang; Eduard Y. Chekmenev; Richard J. Wittebort

2003-01-01

160

Preconversion catalytic deoxygenation of phenolic functional groups  

SciTech Connect

The deoxygenation of phenols is a conceptually simple, but unusually difficult chemical transformation to achieve. Aryl carbon-oxygen bond cleavage is a chemical transformation of importance in coal liquefaction and the upgrading of coal liquids as well as in the synthesis of natural products. This proposed research offers the possibility of effecting the selective catalytic deoxygenation of phenolic functional groups using CO. A program of research for the catalytic deoxygenation of phenols, via a low energy mechanistic pathway that is based on the use of the CO/CO{sub 2} couple to remove phenolic oxygen atoms, is underway. We are focusing on systems which have significant promise as catalysts: Ir(triphos)OPh, (Pt(triphos)OPh){sup +} and Rh(triphos)OPh. Our studies of phenol deoxygenation focus on monitoring the reactions for the elementary processes upon which catalytic activity will depend: CO insertion into M-OPh bonds, CO{sub 2} elimination from aryloxy carbonyls {l brace}M-C(O)-O-Ph{r brace}, followed by formation of a coordinated benzyne intermediate.

Kubiak, C.P.

1991-01-01

161

A Functional Cryptosystem Using a Group Action  

Microsoft Academic Search

The main purpose of this paper is to examine applications of group theoretical concepts to cryptography. We construct a backward\\u000a deterministic system employing the action of the modular group on the upper half plane and the amalgamated free product structure\\u000a of the group. We invent a geometrical algorithm that finds the normal form of an element of the modular group

Akihiro Yamamura

1999-01-01

162

Carboxylation of thin graphitic sheets is faster than that of carbon nanohorns.  

PubMed

Globular aggregates of carbon nanohorns (CNHs) often contain graphite-like thin sheets (GLSs), and providing different functions to CNHs and GLSs would expand the possible applications of the CNH-GLS aggregates. We show that the GLS edges can be carboxylated selectively by immersing the aggregates in an aqueous solution of H2O2 at room temperature for 1 hour. The presence of carboxyl groups was confirmed by temperature-programmed desorption mass spectroscopy measurements, and their amounts were evaluated using thermogravimetric analysis. The preferential carboxylation of GLSs at their edges was evidenced, after the carboxyl groups were reacted with Pt-ammine complexes, by electron microscopic observation of the Pt atoms at the GLS edges. Since few holes in CNH walls were opened by the short-period H2O2 treatment, there was little carboxylation of CNHs. PMID:23982191

Nakamura, Maki; Irie, Michiko; Yuge, Ryota; Ichihashi, Toshinari; Iijima, Sumio; Yudasaka, Masako

2013-08-28

163

Reactions of carboxylated butadiene-styrene rubbers and their mixtures with ?-caprolactam induced by gamma-radiation  

Microsoft Academic Search

Carboxylated butadiene-styrene rubber containing various amounts of ; styrene and methacrylic acid were exposed to 0.1 to 50 Mr doses of gamma ; radiation form a Co⁶° source. This irradiation resulted in a decrease in ; the carboxyl group content, particularly at low doses. The radiochemical yield ; of crosslinked polymers at low doses is a linear function of the

I. Mladenov; B. A. Dogadkin

1962-01-01

164

Structural Group Analysis of Functional Activation Maps  

Microsoft Academic Search

We present here a new method for cerebral activation detection over a group of subjects. This method is performed using individual activation maps of any sort. It aims at processing a group analysis while preserving individual information and at overcoming as far as possible limitations of the spatial normalization used to compare different subjects. We designed it such that it

O. Coulon; J.-F. Mangin; J.-B. Poline; M. Zilbovicius; D. Roumenov; Y. Samson; V. Frouin; I. Bloch

2000-01-01

165

Insights into the effects of functional groups on carbon nanotubes for the electrooxidation of methanol.  

PubMed

Functionalized carbon nanotubes were used as a support for PtCo nanoparticles. Their performance as electrocatalysts for the electrooxidation of methanol was evaluated by cyclic voltammetry and in situ FTIR reflectance spectroscopy. The onset potentials for both the electrooxidation of methanol and the production of CO(2) shifted to less positive values for catalysts prepared with more oxygen groups on the support. Furthermore, the production of CO(2) was higher on catalysts prepared with functionalized carbon nanotubes. The functional groups play two different but complementary roles. On the one hand, they help to stabilize smaller PtCo particles of ca. 3 nm. On the other hand, they provide the -OH groups necessary for the total oxidation of methanol to CO(2) at potentials less positive than on nonfunctionalized supports. Remarkably, the consumption of carboxylic acid groups along with the production of water is observed in the infrared spectra of the functionalized supports recorded during the electrooxidation of methanol. This observation suggests that the -OH groups of the support can also react with methanol, forming water and an ester. PMID:21739936

Hernández-Fernández, Patricia; Baranton, Steve; Rojas, Sergio; Ocón, Pilar; Léger, Jean-Michel; Fierro, Jose Luis G

2011-07-08

166

Carboxylic acid (bio)isosteres in drug design.  

PubMed

The carboxylic acid functional group can be an important constituent of a pharmacophore, however, the presence of this moiety can also be responsible for significant drawbacks, including metabolic instability, toxicity, as well as limited passive diffusion across biological membranes. To avoid some of these shortcomings while retaining the desired attributes of the carboxylic acid moiety, medicinal chemists often investigate the use of carboxylic acid (bio)isosteres. The same type of strategy can also be effective for a variety other purposes, for example, to increase the selectivity of a biologically active compound or to create new intellectual property. Several carboxylic acid isosteres have been reported, however, the outcome of any isosteric replacement cannot be readily predicted as this strategy is generally found to be dependent upon the particular context (i.e., the characteristic properties of the drug and the drug-target). As a result, screening of a panel of isosteres is typically required. In this context, the discovery and development of novel carboxylic acid surrogates that could complement the existing palette of isosteres remains an important area of research. The goal of this Minireview is to provide an overview of the most commonly employed carboxylic acid (bio)isosteres and to present representative examples demonstrating the use and utility of each isostere in drug design. PMID:23361977

Ballatore, Carlo; Huryn, Donna M; Smith, Amos B

2013-01-29

167

Carboxylic acid functionalization prevents the translocation of multi-walled carbon nanotubes at predicted environmentally relevant concentrations into targeted organs of nematode Caenorhabditis elegans.  

PubMed

Carboxyl (-COOH) surface modified multi-walled carbon nanotubes (MWCNTs-COOH) can be used for targeted delivery of drugs and imaging. However, whether MWCNTs-COOH at environmentally relevant concentrations exert certain toxic effects on multicellular organisms and the underlying mechanisms are still largely unclear. In the present study, we applied the nematode Caenorhabditis elegans to evaluate the properties of MWCNTs-COOH at environmentally relevant concentrations by comparing the effects of MWCNTs and MWCNTs-COOH exposure on C. elegans from L1-larvae to adult at concentrations of 0.001-1000 ?g L(-1). Exposure to MWCNTs could potentially damage the intestine (primary targeted organ) at concentrations greater than 0.1 ?g L(-1) and functions of neurons and reproductive organ (secondary targeted organs) at concentrations greater than 0.001 ?g L(-1). Carboxyl modification prevented the toxicity of MWCNTs on the primary and the secondary targeted organs at concentrations less than 100 ?g L(-1), suggesting that carboxyl modification can effectively prevent the adverse effects of MWCNTs at environmentally relevant concentrations. After exposure, MWCNTs-COOH (1 mg L(-1)) were translocated into the spermatheca and embryos in the body through the primary targeted organs. However, MWCNTs-COOH (10 ?g L(-1)) were not observed in spermatheca and embryos in the body of nematodes. Moreover, relatively high concentrations of MWCNTs-COOH exposed nematodes might have a hyper-permeable intestinal barrier, whereas MWCNTs-COOH at environmentally relevant concentrations effectively sustained the normally permeable state for the intestinal barrier. Therefore, we elucidated the cellular basis of carboxyl modification to prevent toxicity of MWCNTs at environmentally relevant concentrations. Our data highlights the key role of biological barriers in the primary targeted organs to block toxicity formation from MWCNTs, which will be useful for the design of effective prevention strategies against MWCNTs toxicity. PMID:23722228

Nouara, Abdelli; Wu, Qiuli; Li, Yinxia; Tang, Meng; Wang, Haifang; Zhao, Yuliang; Wang, Dayong

2013-05-30

168

Subtle cytotoxicity and genotoxicity differences in superparamagnetic iron oxide nanoparticles coated with various functional groups  

PubMed Central

Superparamagnetic iron oxide nanoparticles (SPIONs) have been widely utilized for the diagnosis and therapy of specific diseases, as magnetic resonance imaging (MRI) contrast agents and drug-delivery carriers, due to their easy transportation to targeted areas by an external magnetic field. For such biomedical applications, SPIONs must have multifunctional characteristics, including optimized size and modified surface. However, the biofunctionality and biocompatibility of SPIONs with various surface functional groups of different sizes have yet to be elucidated clearly. Therefore, it is important to carefully monitor the cytotoxicity and genotoxicity of SPIONs that are surfaced-modified with various functional groups of different sizes. In this study, we evaluated SPIONs with diameters of approximately 10 nm and 100~150 nm, containing different surface functional groups. SPIONs were covered with ?O? groups, so-called bare SPIONs. Following this, they were modified with three different functional groups – hydroxyl (?OH), carboxylic (?COOH), and amine (?NH2) groups – by coating their surfaces with tetraethyl orthosilicate (TEOS), (3-aminopropyl)trimethoxysilane (APTMS), TEOS-APTMS, or citrate, which imparted different surface charges and sizes to the particles. The effects of SPIONs coated with these functional groups on mitochondrial activity, intracellular accumulation of reactive oxygen species, membrane integrity, and DNA stability in L-929 fibroblasts were determined by water-soluble tetrazolium, 2?,7?-dichlorodihydrofluorescein, lactate dehydrogenase, and comet assays, respectively. Our toxicological observations suggest that the functional groups and sizes of SPIONs are critical determinants of cellular responses, degrees of cytotoxicity and genotoxicity, and potential mechanisms of toxicity. Nanoparticles with various surface modifications and of different sizes induced slight, but possibly meaningful, changes in cell cytotoxicity and genotoxicity, which would be significantly valuable in further studies of bioconjugation and cell interaction for drug delivery, cell culture, and cancer-targeting applications.

Hong, Seong Cheol; Lee, Jong Ho; Lee, Jaewook; Kim, Hyeon Yong; Park, Jung Youn; Cho, Johann; Lee, Jaebeom; Han, Dong-Wook

2011-01-01

169

Detecting Functional Groups of Arabidopsis Mutants by Metabolic Profiling and Evaluation of Pleiotropic Responses  

PubMed Central

Metabolic profiles and fingerprints of Arabidopsis thaliana plants with various defects in plastidic sugar metabolism or photosynthesis were analyzed to elucidate if the genetic mutations can be traced by comparing their metabolic status. Using a platform of chromatographic and spectrometric tools data from untargeted full MS scans as well as from selected metabolites including major carbohydrates, phosphorylated intermediates, carboxylates, free amino acids, major antioxidants, and plastidic pigments were evaluated. Our key observations are that by multivariate statistical analysis each mutant can be separated by a unique metabolic signature. Closely related mutants come close. Thus metabolic profiles of sugar mutants are different but more similar than those of photosynthesis mutants. All mutants show pleiotropic responses mirrored in their metabolic status. These pleiotropic responses are typical and can be used for separating and grouping of the mutants. Our findings show that metabolite fingerprints can be taken to classify mutants and hence may be used to sort genes into functional groups.

Hofmann, Jorg; Bornke, Frederik; Schmiedl, Alfred; Kleine, Tatjana; Sonnewald, Uwe

2011-01-01

170

Parameterization of Leaf-Level Gas Exchange for Plant Functional Groups From Amazonian Seasonal Tropical Rain Forest  

NASA Astrophysics Data System (ADS)

Plant communities exert strong influence over the magnitude of carbon and water cycling through ecosystems by controlling photosynthetic gas exchange and respiratory processes. Leaf-level gas exchange fluxes result from a combination of physiological properties, such as carboxylation capacity, respiration rates and hydraulic conductivity, interacting with environmental drivers such as water and light availability, leaf-to-air vapor pressure deficit, and temperature. Carbon balance models concerned with ecosystem-scale responses have as a common feature the description of eco-physiological properties of vegetation. Here we focus on the parameterization of ecophysiological gas-exchange properties of plant functional groups from a pristine Amazonian seasonally dry tropical rain forest ecosystem (FLONA-Tapajós, Santarém, PA, Brazil). The parameters were specific leaf weight, leaf nitrogen content, leaf carbon isotope ratio, maximum photosynthetic assimilation rate, photosynthetic carboxylation capacity, dark respiration rates, and stomatal conductance to water vapor. Our plant functional groupings were lianas at the top of the canopy, trees at the top of the canopy, mid-canopy trees and undestory trees. Within the functional groups, we found no evidence that leaves acclimated to seasonal changes in precipitation. However, there were life-form dependent distinctions when a combination of parameters was included. Top-canopy lianas were statistically different from top-canopy trees for leaf carbon isotope ratio, maximum photosynthetic assimilation rate, and stomatal conductance to water vapor, suggesting that lianas are more conservative in the use of water, causing a stomatal limitation on photosynthetic assimilation. Top-canopy, mid canopy and understory groupings were distinct for specific leaf weight, leaf nitrogen content, leaf carbon isotope ratio, maximum photosynthetic assimilation rate, and photosynthetic carboxylation capacity. The recognition that plant functional groups have distinct impacts on ecosystem-scale gas exchange can increase the accuracy of process-based carbon balance models where structure is known and when logging activities are incorporated into production models.

Domingues, T. F.; Berry, J. A.; Ometto, J. P.; Martinelli, L. A.; Ehleringer, J. R.

2004-12-01

171

Functional group analysis in coal and on coal surfaces by NMR spectroscopy  

SciTech Connect

An accurate knowledge of the oxygen-bearing labile hydrogen functional groups (e.g., carboxylic acids, phenols and alcohols) in coal is required for today's increasingly sophisticated coal cleaning and beneficiation processes. Phospholanes (compounds having the general structure -POCH{sub 2}CH{sub 2}O (1)) are being investigated as reagents for the tagging of liable hydrogen functional groups in coal materials with the NMR-active {sup 31}P nucleus. Of twelve such reagents investigated so far, 2 (2-chloro-1,3-dioxaphospholane, ClPOCH{sub 2}CH{sub 2}O) and 8 (2-chloro-1,3-dithiaphospholane, ClPSCH{sub 2}CH{sub 2}S) have been found to be useful in identifying and quantitating, by {sup 31}P NMR spectroscopy, labile hydrogen functional groups in an Illinois No. 6 coal condensate. Reagent 2 has also been used to quantitate moisture in pyridine extracts of Argonne Premium Coal Samples. Preliminary {sup 119}Sn NMR spectroscopic results on model compounds with the new reagent CF{sub 3}C(O)NHSnMe{sub 3} (N-trimethylstannyltrifluoroacetamide, 14) suggest that labile hydrogen functional groups in coal materials may be more precisely identified with 14 than with phospholanes. 14 refs., 2 figs., 2 tabs.

Verkade, J.G.

1990-01-01

172

Remarkable electronic and steric effects in the nitrile biotransformations for the preparation of enantiopure functionalized carboxylic acids and amides: implication for an unsaturated carbon-carbon bond binding domain of the amidase.  

PubMed

Biotransformations of various functionalized racemic nitriles catalyzed by Rhodococcus erythropolis AJ270, a nitrile hydratase/amidase-containing microbial whole-cell catalyst, were studied. While the nitrile hydratase exhibits high catalytic efficiency but very low enantioselectivity against almost all nitrile substrates examined, the amidase is very sensitive toward the structure of the amides. The release of the steric crowdedness around the stereocenter of the substrates and the introduction of an unsaturated carbon-carbon bond into the substrates led to the significant acceleration of the reaction rate and the dramatic enhancement of the enantioselectivity. Nitrile biotransformations provide a unique and high-yielding synthetic route to highly enantiopure carboxylic acids and amides functionalized with an allyl, propargyl, allenyl, or vinyl group. The synthetic applications have been demonstrated by the synthesis of enantiopure heterocyclic compounds including iodoenol gamma-lactone, gamma-lactam, and 3-allyl-1-phenyl-3,4-dihydro-1H-quinolin-2-one derivatives. PMID:17604398

Gao, Ming; Wang, De-Xian; Zheng, Qi-Yu; Huang, Zhi-Tang; Wang, Mei-Xiang

2007-06-30

173

Ethnic Identity and Solidarity with Functional Groups  

Microsoft Academic Search

The world is globalizing, and the social groups in which we work, study, or recreate are becoming more pluralistic in nature. Consequently, societies have to cope with the integration of different cultures. It is an important question how immigrants can be motivated to act prosocially toward members of their new societies and to refrain from antisocial behaviors. Why would immigrants

Karen van der Zee

174

Density functional theory study of the mechanism of the acid-catalyzed decarboxylation of pyrrole-2-carboxylic acid and mesitoic acid  

Microsoft Academic Search

The mechanisms of the acid-catalyzed decarboxylation of pyrrole-2-carboxylic acid and mesitoic acid have been investigated\\u000a based on density functional theory calculations at the B3LYP\\/6-311G (d, p) level. A polarizable continuum model (PCM) has\\u000a been established in order to evaluate the effects of solvents on these reactions. The results of the calculations indicate\\u000a that the first step of the acid-catalyzed decarboxylation

XingHui Zhang; ZhiYuan Geng; YongCheng Wang

2011-01-01

175

Mild Conversion of ?-Diketones and ?-Ketoesters to Carboxylic Acids  

PubMed Central

A mild protocol for the conversion of ?-ketoesters and ?-diketones to carboxylic acids using CAN in CH3CN is described. The method is compatible with a number of functional groups, and can generate carboxylic acids under neutral conditions at room temperature. The reaction is fast and general, providing an alternative method to the commonly used malonic ester acid preparation. Initial mechanistic studies show that initial oxidation of the enol form of the ?-dicarbonyl initiates the reaction. The presence of nitrate as an oxidant ligand or as an additive is critical for success of the reaction.

Zhang, Yang; Jiao, Jingliang

2013-01-01

176

Decarboxylation of pyrrole-2-carboxylic acid: A DFT investigation  

NASA Astrophysics Data System (ADS)

Decarboxylation is normally a dissociative process, commonly catalyzed by proton or enzymes. The decarboxylation mechanism of pyrrole-2-carboxylic acid involves the addition of water to the carboxyl group, and the C-C bond cleavage leading to the protonated carbonic acid. The direct decarboxylation and decarboxylation aided with water were also investigated to consider the functions of proton and water. Our calculations with G AUSSIAN 03 package show that, with the assistance of H 3O +, the potential energy of the C-C rupture decreases significantly to 9.77 kcal/mol, and the total energy barrier decreases to 33.99 kcal/mol.

Cheng, Xueli; Wang, Jinhu; Tang, Ke; Liu, Yongjun; Liu, Chengbu

2010-08-01

177

Functional Renormalization Group Approach to the Sine-Gordon Model  

SciTech Connect

The renormalization group flow is presented for the two-dimensional sine-Gordon model within the framework of the functional renormalization group method by including the wave-function renormalization constant. The Kosterlitz-Thouless-Berezinski type phase structure is recovered as the interpolating scaling law between two competing IR attractive area of the global renormalization group flow.

Nagy, S.; Sailer, K. [Department of Theoretical Physics, University of Debrecen, Debrecen (Hungary); Nandori, I. [Institute of Nuclear Research, P.O. Box 51, H-4001 Debrecen (Hungary); Polonyi, J. [Strasbourg University, CNRS-IPHC, BP28 67037 Strasbourg Cedex 2 (France)

2009-06-19

178

Effects of functional groups and ionization on the structure of alkanethiol coated gold nanoparticles  

NASA Astrophysics Data System (ADS)

We report fully atomistic molecular dynamics simulations of alkanethiol coated gold nanoparticles solvated in water and decane. The structure of the coatings is analyzed as a function of various functional end groups, including amine and carboxyl groups in different neutralization states. We study the effects of charge in the end groups for two different chain lengths (10 and 18 carbons) and different counterions (mono- and divalent). For the longer alkanes we find significant local phase segregation of chains on the nanoparticle surface, which results in highly asymmetric coating structures. In general, the charged end groups attenuate this effect by enhancing the water solubility of the nanoparticles. Based on the coating structures and density profiles, we can qualitatively infer the overall solubility of the nanoparticles. The asymmetry in the alkanethiol coatings is also likely to have a significant effect on aggregation behavior. More importantly, our simulations suggest the ability to modulate end group charge states (e.g. by changing the pH of the solution) in order to control coating structure, and therefore control solubility and aggregation behavior.

Bolintineanu, Dan S.; Lane, J. Matthew D.; Grest, Gary S.

2013-03-01

179

ATR-FTIR characterization of organic functional groups and inorganic ions in ambient aerosols at a rural site  

NASA Astrophysics Data System (ADS)

An Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopic method was used to measure organic functional groups and inorganic ions at Tonto National Monument (TNM), an Interagency Monitoring of Protected Visual Environments (IMPROVE) sampling site in a rural area near Phoenix, Arizona. Functional groups and ions from common aerosol compound classes such as aliphatic and aromatic CH, methylene, methyl, aldehydes/ketones, carboxylic acids, ammonium sulfate and nitrate as well as functional groups from difficult to measure compound classes such as esters/lactones, acid anhydrides, carbohydrate hydroxyl and ethers, amino acids, and amines were quantified. On average, ˜33% of the PM 1.0 mass was composed of organic aerosol. The average (standard deviation) composition of the organic aerosol at TNM was 34% (6%) biogenic functional groups, 21% (5%) oxygenated functional groups, 28% (7%) aliphatic hydrocarbon functional groups (aliphatic CH, methylene and methyl) and 17% (1%) aromatic hydrocarbon functional groups. Compositional analysis, functional group correlations, and back trajectories were used to identify three types of events with source signatures: primary biogenic-influenced, urban-influenced, and regional background. The biogenic-influenced event had high concentrations of amino acids and carbohydrate hydroxyl and ether, as well as aliphatic CH and aromatic CH functional groups and qualitatively high levels of silicate. The urban-influenced events had back trajectories traveling directly from the Phoenix area and high concentrations of hydrocarbons, oxygenated functional groups, and inorganic ions. This aerosol characterization suggests that both primary emissions in Phoenix and secondary formation of aerosols from Phoenix emissions had a major impact on the aerosol composition and concentration at TNM. The regional background source had low concentrations of all functional groups, but had higher concentrations of biogenic functional groups than the urban source.

Coury, Charity; Dillner, Ann M.

180

Synthesis of carboxylate-functionalized graphene nanosheets for high dispersion of platinum nanoparticles based on the reduction of graphene oxide via 1-pyrenecarboxaldehyde  

NASA Astrophysics Data System (ADS)

A one-step reduction/functionalization strategy for the synthesis of carboxylate-functionalized graphene nanosheets is reported in this paper. 1-pyrenecarboxaldehyde (PCA) is introduced as a new reductant for the chemical reduction of graphene oxide (GO), serving three roles: reducing GO to graphene nanosheets (GNs), stabilizing the as-prepared GNs due to the electrostatic repulsion of the oxidation products of PCA (1-pyrenecarboxylate, PC?) on the surface of the GNs and anchoring Pt nanoparticles (Pt NPs) with high dispersion and small particle size. Transmission electron microscopy shows that Pt NPs with an average diameter of 1.3 ± 0.2 nm are uniformly dispersed on the surface of the PC?-functionalized GNs (PC?-GNs). The obtained Pt NPs/PC?-GNs nanohybrids have higher electrocatalytic activity and stability towards methanol oxidation in comparison with Pt NPs supported on GNs obtained by the chemical reduction of GO with the typical reductant, hydrazine.

Kuang, Yinjie; Chen, Jinhua; Zheng, Xingliang; Zhang, Xiaohua; Zhou, Qionghua; Lu, Cuihong

2013-10-01

181

Studies on pore structures and surface functional groups of pitch-based activated carbon fibers.  

PubMed

The present study concerns the physical activation and chemical oxidation of pitch-based activated carbon fibers (ACFs) as ways to improve the adsorption properties. The surface oxides of the ACFs studied were determined by Boehm's titration and the pore structures were studied by the BET method with N(2)/77 K adsorption. Also, the adsorption properties of the ACFs were investigated with chromium ion adsorption by different adsorption models. As a result, it was observed that carboxyl groups were largely created after nitric acid treatment on ACFs. The affinity for chromium ions increases with increasing specific surface area, micropore volume, and surface functionalities of ACFs as the activation time increases. PMID:12686173

Park, Soo-Jin; Jang, Yu-Sin; Shim, Jae-Woon; Ryu, Seung-Kon

2003-04-15

182

Preconversion catalytic deoxygenation of phenolic functional groups. Quarterly report, January 1--March 30, 1996  

SciTech Connect

Over the course of the studies on catalytic deoxygenation of phenolic residues in coal by carbon monoxide, the author performed preliminary investigations into the removal of other heteroatom groups. This report describes the attempted carbonylation of phenyl amido complexes. These studies resulted in the surprisingly facile formation of amidines. The amidine group is the nitrogen analog of carboxylic acids and esters. This functional group combines the properties of an azomethane-like C=N double bond with an amide-like C-N single bond. This group, like the related allyl (C-C-C), aza-allyl (C-N-C), and carboxylato (O-C-O) groups, form a number of transition metal derivatives, with both early and late transition metals. Various bonding modes of the amidino group have been reported. However, most isolated complexes have the amidino ligand as a chelating ligand or bridging two metals. This is due to the preference of amidines to bond via the nitrogen lone pairs, in contrast to the {eta}3 bonding observed in metal-allyl complexes. The experimental section of the paper describes the synthesis of platinum complexes, X-ray diffraction data for one Pt complex, and its reaction with carbon monoxide. Results are presented on the crystal and molecular structure of a platinum complex.

Kubiak, C.P.

1996-12-31

183

NEW CATION EXCHANGE RESINS BASED ON POLYVINYL ALCOHOL CONTAINING CARBOXYL GROUPS FOR THE REMOVAL OF SOME TEXTILE CONTAMINANTS FROM AQUEOUS SOLUTIONS  

Microsoft Academic Search

Two cation exchange resins having carboxyl contents, 628 and 424 meq\\/100 g sample were prepared by free radical polymerization of acrylic acid in presence of polyvinyl alcohol aqueous solution using methylenebisacrylamide as a crosslinker and ammonium persulfate as an initiator. The prepared resins were characterized by investigation of their potentiometric titration, durability, water solubility, and swellability. The removal of Cu ions (in

H. M. Fahmy; Z. El-Sayed

2002-01-01

184

Zeta Functions of Discrete Groups Acting on Trees  

Microsoft Academic Search

This paper generalizes Bass' work on zeta functions for uniform tree lattices. Using the theory of von Neumann algebras, machinery is developed to define the zeta function of a discrete group of automorphisms of a bounded degree tree. The main theorems relate the zeta function to determinants of operators defined on edges or vertices of the tree.A zeta function associated

Bryan Clair; Shahriar Mokhtari-Sharghi

2001-01-01

185

1H-Imidazol-3-ium-4-carboxyl-ate  

PubMed Central

In the title compound, C4H4N2O2, both imidazole N atoms are protonated and carboxyl­ate group is deprotonated, resulting in a zwitterion. The mol­ecule is essentially planar, with an r.m.s. deviation of 0.012?(1)?Å. In the crystal, N—H?O hydrogen bonds and ?–? stacking inter­actions [centroid–centroid distance = 3.674?(2)?Å] between the imidazole rings link the mol­ecules into a three-dimensional supra­molecular network.

Cao, Qiang; Duan, Bao-Rong; Zhu, Bin; Cao, Zhen

2012-01-01

186

Various fates of neuronal progenitor cells observed on several different chemical functional groups  

NASA Astrophysics Data System (ADS)

Neuronal progenitor cells cultured on gold-coated glass surfaces modified by different chemical functional groups, including hydroxyl (-OH), carboxyl (-COOH), amino (-NH2), bromo (-Br), mercapto (-SH), - Phenyl and methyl (-CH3), were studied here to investigate the influence of surface chemistry on the cells' adhesion, morphology, proliferation and functional gene expression. Focal adhesion staining indicated in the initial culture stage cells exhibited morphological changes in response to different chemical functional groups. Cells cultured on -NH2 grafted surface displayed focal adhesion plaque and flattened morphology and had the largest contact area. However, their counter parts on -CH3 grafted surface displayed no focal adhesion and rounded morphology and had the smallest contact area. After 6 days culture, the proliferation trend was as follows: -NH2 > -SH> -COOH> - Phenyl > - Br > -OH> -CH3. To determine the neural functional properties of the cells affected by surface chemistry, the expression of glutamate decarboxylase (GAD67), nerve growth factor (NGF) and brainderived neurotrophic factor (BDNF) were characterized. An increase of GAD67 expression was observed on -NH2, -COOH and -SH grafted surfaces, while no increase in NGF and BDNF expression was observed on any chemical surfaces. These results highlight the importance of surface chemistry in the fate determination of neuronal progenitor cells, and suggest that surface chemistry must be considered in the design of biomaterials for neural tissue engineering.

Liu, Xi; Wang, Ying; He, Jin; Wang, Xiu-Mei; Cui, Fu-Zhai; Xu, Quan-Yuan

2011-12-01

187

Facile Synthesis of Second-Generation Dendrons with an Orthogonal Functional Group at the Focal Point  

Microsoft Academic Search

Facile synthesis of second-generation dendrons with an aldehyde, epoxy, or t-Boc group at the focal point and nine carboxylic acid groups at the periphery is reported. The scheme includes a coupling of the first-generation dendrons and a two-step, one-pot reaction that proceeds through a Boc deprotection and in situ conjugation at the focal point.

Ravi Kumar Cheedarala; Vijaya Sunkara; Joon Won Park

2009-01-01

188

Carboxylate binding modes in zinc proteins: A theoretical study  

PubMed Central

The relative energies of different coordination modes (bidentate, monodentate, syn, and anti) of a carboxylate group bound to a zinc ion have been studied by the density functional method B3LYP with large basis sets on realistic models of the active site of several zinc proteins. In positively charged four-coordinate complexes, the mono- and bidentate coordination modes have almost the same energy (within 10 kJ/mol). However, if there are negatively charged ligands other than the carboxylate group, the monodentate binding mode is favored. In general, the energy difference between monodentate and bidentate coordination is small, 4-24 kJ/mol, and it is determined more by hydrogen-bond interactions with other ligands or second-sphere groups than by the zinc-carboxylate interaction. Similarly, the activation energy for the conversion between the two coordination modes is small, approximately 6 kJ/mol, indicating a very flat Zn-O potential surface. The energy difference between syn and anti binding modes of the monodentate carboxylate group is larger, 70-100 kJ/mol, but this figure again strongly depends on interactions with second-sphere molecules. Our results also indicate that the pK(a) of the zinc-bound water ligand in carboxypeptidase and thermolysin is 8-9.

Ryde, U

1999-01-01

189

Carboxyl Group of Glu113 Is Required for Stabilization of the Diferrous and Bis-Fe(IV) States of MauG.  

PubMed

The diheme enzyme MauG catalyzes a six-electron oxidation required for post-translational modification of a precursor of methylamine dehydrogenase (preMADH) to complete the biosynthesis of its protein-derived tryptophan tryptophylquinone (TTQ) cofactor. Crystallographic studies have implicated Glu113 in the formation of the bis-Fe(IV) state of MauG, in which one heme is Fe(IV)?O and the other is Fe(IV) with His-Tyr axial ligation. An E113Q mutation had no effect on the structure of MauG but significantly altered its redox properties. E113Q MauG could not be converted to the diferrous state by reduction with dithionite but was only reduced to a mixed valence Fe(II)/Fe(III) state, which is never observed in wild-type (WT) MauG. Addition of H2O2 to E113Q MauG generated a high valence state that formed more slowly and was less stable than the bis-Fe(IV) state of WT MauG. E113Q MauG exhibited no detectable TTQ biosynthesis activity in a steady-state assay with preMADH as the substrate. It did catalyze the steady-state oxidation of quinol MADH to the quinone, but 1000-fold less efficiently than WT MauG. Addition of H2O2 to a crystal of the E113Q MauG-preMADH complex resulted in partial synthesis of TTQ. Extended exposure of these crystals to H2O2 resulted in hydroxylation of Pro107 in the distal pocket of the high-spin heme. It is concluded that the loss of the carboxylic group of Glu113 disrupts the redox cooperativity between hemes that allows rapid formation of the diferrous state and alters the distribution of high-valence species that participate in charge-resonance stabilization of the bis-Fe(IV) redox state. PMID:23952537

Abu Tarboush, Nafez; Yukl, Erik T; Shin, Sooim; Feng, Manliang; Wilmot, Carrie M; Davidson, Victor L

2013-08-30

190

Synthesis of hollow polymer microspheres with movable polyelectrolyte core and functional groups on the shell-layer  

Microsoft Academic Search

Hollow polymer microspheres with movable quaternary pyridinium polyelectrolyte (PE) cores and various functional groups on the shell-layers, such as hydroxyl, amide, and carboxyl, were prepared by the selectively etching of mid-silica layer with hydrofluoric acid from the corresponding poly(ethyleneglycol dimethacrylate-co-methacrylic acid)@poly(ethyleneglycol dimethacrylate- co-4-vinylpyridinium benzylchloride)\\/silica\\/polymer (P(EGDMA-co-MAA) @P(EGDMA-co-VPyBzCl)\\/SiO2\\/polymer) tetra-layer microspheres. The tetra-layer hybrid microspheres were synthesized by a multi-stage reaction process, which included

Min Ji; Bin Liu; Xinlin Yang; Junyou Wang

2009-01-01

191

Group-complement code signal and its radar ambiguity function  

NASA Astrophysics Data System (ADS)

A group-complement code (GCC) is a type of artificial noise, generally a code group consisting of a multigroup equal length subcode with each of its elements being coded in accordance with frequency, phase, and amplitude. After the screened group-complement codes are received by using auto-correlation method, the sum of all subcode auto-correlation function is characterized by total complementarity. If used in radar, the group-complement code forms an artificial noise radar. If used in communication, it forms an artificial noise communication. This paper will mainly focus on explaining the domains, mathematical model, and radar ambiguity function of the group-complement code.

Zhong, Chi-Rui

192

Detection of Differential Item Functioning in Multiple Groups.  

ERIC Educational Resources Information Center

|Detection of differential item functioning (DIF) is most often done between two groups of examinees under item response theory. It is sometimes important, however, to determine whether DIF is present in more than two groups. A method is presented for the detection of DIF in multiple groups. The method, the Q(sub j) statistic, is closely related…

Kim, Seock-Ho; And Others

193

Functional Analytic Psychotherapy for Interpersonal Process Groups: A Behavioral Application  

ERIC Educational Resources Information Center

|This paper is an adaptation of Kohlenberg and Tsai's work, Functional Analytical Psychotherapy (1991), or FAP, to group psychotherapy. This author applied a behavioral rationale for interpersonal process groups by illustrating key points with a hypothetical client. Suggestions are also provided for starting groups, identifying goals, educating…

Hoekstra, Renee

2008-01-01

194

Toward Functional Carboxylate-Bridged Diiron Protein Mimics: Achieving Structural Stability and Conformational Flexibility Using a Macrocylic Ligand Framework  

PubMed Central

A dinucleating macrocycle, H2PIM, containing phenoxylimine metal-binding units has been prepared. Reaction of H2PIM with [Fe2(Mes)4] (Mes = 2,4,6-trimethylphenyl) and sterically hindered carboxylic acids, Ph3CCO2H or ArTolCO2H (2,6-bis(p-tolyl)benzoic acid), afforded complexes [Fe2(PIM)(Ph3CCO2)2] (1) and [Fe2(PIM)(ArTolCO2)2] (2), respectively. X-ray diffraction studies revealed that these diiron(II) complexes closely mimic the active site structures of the hydroxylase components of bacterial multi-component monooxygenases (BMMs), particularly the syn disposition of the nitrogen donor atoms and the bridging ?-?1?2 and ?-?1?1 modes of the carboxylate ligands at the diiron(II) centers. Cyclic voltammograms of 1 and 2 displayed quasi-reversible redox couples at +16 and +108 mV vs. ferrocene/ferrocenium, respectively. Treatment of 2 with silver perchlorate afforded a silver(I)/iron(III) heterodimetallic complex, [Fe2(?-OH)2(ClO4)2(PIM)(ArTolCO2)Ag] (3), which was structurally and spectroscopically characterized. Complexes 1 and 2 both react rapidly with dioxygen. Oxygenation of 1 afforded a (?-hydroxo)diiron(III) complex [Fe2(?-OH)(PIM)(Ph3CCO2)3] (4), a hexa(?-hydroxo)tetrairon(III) complex [Fe4(?-OH)6(PIM)2(Ph3CCO2)2] (5), and an unidentified iron(III) species. Oxygenation of 2 exclusively formed di(carboxylato)diiron(III) compounds, a testimony to the role of the macrocylic ligand in preserving the dinuclear iron center under oxidizing conditions. X-ray crystallographic and 57Fe Mössbauer spectroscopic investigations indicated that 2 reacts with dioxygen to give a mixture of (?-oxo)diiron(III) [Fe2(?-O)(PIM)(ArTolCO2)2] (6) and di(?-hydroxo)diiron(III) [Fe2(?-OH)2(PIM)(ArTolCO2)2] (7) units in the same crystal lattice. Compounds 6 and 7 spontaneously convert to a tetrairon(III) complex, [Fe4(?-OH)6(PIM)2(ArTolCO2)2] (8), when treated with excess H2O.

Do, Loi H.; Lippard, Stephen J.

2011-01-01

195

How functional is functional? Ecological groupings in terrestrial animal ecology: towards an animal functional type approach  

Microsoft Academic Search

Understanding mechanisms to predict changes in plant and animal communities is a key challenge in ecology. The need to transfer\\u000a knowledge gained from single species to a more generalized approach has led to the development of categorization systems where\\u000a species’ similarities in life strategies and traits are classified into ecological groups (EGs) like functional groups\\/types\\u000a or guilds. While approaches in

Niels Blaum; Eva Mosner; Monika Schwager; Florian Jeltsch

196

The impact of carboxylic acids on ice nucleation  

NASA Astrophysics Data System (ADS)

Ice nucleation is a process which is not fully understood yet. Especially the influence of carboxylic acids has to be investigated. As shown by Pratt et al.[1] carboxylic acids are present in the troposphere and their influence on cloud formation is still unknown. Recent studies showed that pure soot aerosol is unable to nucleate ice and citric acid suppresses the nucleation to a certain extent in laboratory models.[2], [3] Therefore it is consequent to further investigate organic acids with different molecular masses and functional groups. Starting with oxalic acid as the smallest carboxylic acid, several other carboxylic acids with different molecular masses and functional groups have been investigated. Every sample has been observed by ESEM, XRD and optical Microscopy. The same preparation procedure has been applied to all samples to gain comparable results and reveal trends on nucleation abilities. [1] Pratt et al. "In situ detection of biological particles in cloud ice-crystals" Nature Geoscience, 2, 398-401, 2009 [2] O.Möhler et al., Meteorol.Z.14, 477, 2005 [3] B.J. Murray "Inhibition of ice crystallization in highly viscous aqueous organic acid droplets." Atmos.Chem.Phys., 8, 5423-5433, 2008

Weiss, F.; Baloh, P.; Grothe, H.

2012-04-01

197

Functional group analysis by H NMR/chemical derivatization for the characterization of organic aerosol from the SMOCC field campaign  

NASA Astrophysics Data System (ADS)

Water soluble organic compounds (WSOC) in aerosol samples collected in the Amazon Basin in a period encompassing the middle/late dry season and the beginning of the wet season, were investigated by H NMR spectroscopy. HiVol filter samples (PM2.5 and PM>2.5) and size-segregated samples from multistage impactor were subjected to H NMR characterization. The H NMR methodology, recently developed for the analysis of organic aerosol samples, has been improved by exploiting chemical methylation of carboxylic groups with diazomethane, which allows the direct determination of the carboxylic acid content of WSOC. The content of carboxylic carbons for the different periods and sizes ranged from 12% to 20% of total measured carbon depending on the season and aerosol size, with higher contents for the fine particles in the transition and wet periods with respect to the dry period. A comprehensive picture is presented of WSOC functional groups in aerosol samples representative of the biomass burning period, as well as of transition and semi-clean atmospheric conditions. A difference in composition between fine (PM2.5) and coarse (PM>2.5) size fractions emerged from the NMR data, the former showing higher alkylic content, the latter being largely dominated by R-O-H (or R-O-R') functional groups. Very small particles (<0.14 ?m), however, present higher alkyl-chain content and less oxygenated carbons than larger fine particles (0.42-1.2 ?m). More limited variations were found between the average compositions in the different periods of the campaign.

Tagliavini, E.; Moretti, F.; Decesari, S.; Facchini, M. C.; Fuzzi, S.; Maenhaut, W.

2006-03-01

198

Functional group analysis by H NMR/ chemical derivatization for the characterization of organic aerosol from the SMOCC field campaign  

NASA Astrophysics Data System (ADS)

Water soluble organic compounds (WSOC) in aerosol samples collected in the Amazon Basin in a period encompassing the middle/late dry season and the beginning of the wet season, were investigated by H NMR spectroscopy. HiVol filter samples (PM2.5 and PM>2.5) and size-segregated samples from multistage impactor were subjected to H NMR characterization. The H NMR methodology, recently developed for the analysis of organic aerosol samples, has been improved exploiting chemical methylation of carboxylic groups with diazomethane, which allows the direct determination of the carboxylic acid content of WSOC. The content of carboxylic carbons for the different periods and sizes ranged from 12% to 20% of total measured carbon depending on the season and aerosol size, with higher contents for the fine particles in the transition and wet periods with respect to the dry period. A comprehensive picture is presented of WSOC functional groups in aerosol samples representative of the biomass burning period, as well as of transition and semi-clean atmospheric conditions. A difference in composition between fine (PM2.5) and coarse (PM>2.5) size fractions emerged from the NMR data, the former showing higher alkylic content, the latter being largely dominated by R-O-H (or R-O-R') functional groups, likely coming from polyols. Very small particles (<0.14 µm), however, present higher alkyl-chain content and less oxygenated carbons than larger fine particles (0.42-1.2 µm). More limited variations were found between the average compositions in the different periods of the campaign.

Tagliavini, E.; Moretti, F.; Decesari, S.; Facchini, M. C.; Fuzzi, S.; Maenhaut, W.

2005-09-01

199

Using Text Analysis to Identify Functionally Coherent Gene Groups  

PubMed Central

The analysis of large-scale genomic information (such as sequence data or expression patterns) frequently involves grouping genes on the basis of common experimental features. Often, as with gene expression clustering, there are too many groups to easily identify the functionally relevant ones. One valuable source of information about gene function is the published literature. We present a method, neighbor divergence, for assessing whether the genes within a group share a common biological function based on their associated scientific literature. The method uses statistical natural language processing techniques to interpret biological text. It requires only a corpus of documents relevant to the genes being studied (e.g., all genes in an organism) and an index connecting the documents to appropriate genes. Given a group of genes, neighbor divergence assigns a numerical score indicating how “functionally coherent” the gene group is from the perspective of the published literature. We evaluate our method by testing its ability to distinguish 19 known functional gene groups from 1900 randomly assembled groups. Neighbor divergence achieves 79% sensitivity at 100% specificity, comparing favorably to other tested methods. We also apply neighbor divergence to previously published gene expression clusters to assess its ability to recognize gene groups that had been manually identified as representative of a common function.

Raychaudhuri, Soumya; Schutze, Hinrich; Altman, Russ B.

2002-01-01

200

Carboxylated magnetic polymer nanolatexes: Preparation, characterization and biomedical applications  

NASA Astrophysics Data System (ADS)

Carboxylated magnetic polymer nanolatexes were prepared by miniemulsion polymerization using 4,4?-azobis(4-cyanopentanoic acid) (ACPA) as initiator, which provided carboxyl end groups on the latex surface directly. The colloidal stability and the magnetic properties showed that these resulting carboxylated magnetic polymer nanolatexes were applicable in biomedical separation, which was performed by covalent coupling of activated antibody.

Zheng, Weiming; Gao, Feng; Gu, Hongchen

2005-05-01

201

Radical carboxylations of iodoalkanes and saturated alcohols using carbon monoxide  

Microsoft Academic Search

This review covers two radical carboxylation methods using carbon monoxide, both of which were developed by our group. The first method, atom transfer carbonylation, converts alkyl iodides into carboxylic acid esters or amides and the second method, remote carboxylation, converts saturated alcohols into d-lactones. Both methods rely upon radical carbonylation chemistry to introduce carbon mon- oxide, but the key steps

Ilhyong Ryu

2001-01-01

202

Organic Mass Fragments and Organic Functional Groups in Aged Biomass Burning and Fossil Fuel Combustion Aerosol  

NASA Astrophysics Data System (ADS)

Organic functional group concentrations in submicron aerosol particles collected from 27 June to 17 September at the Scripps Pier in La Jolla, California as part of AeroSCOPE 2008 were quantified using Fourier Transform Infrared (FTIR) spectroscopy. Organic and inorganic non-refractory components in the same air masses were quantified using a Quadrupole Aerosol Mass Spectrometer (Q-AMS). Previous measurements at the Scripps pier indicate that a large fraction of submicron particle mass originates in Los Angeles and the port of Long Beach. Additional particle sources to the region include local urban emissions and periodic biomass burning during large wildfires. Three distinct types of organic aerosol components were identified from organic composition and elemental tracers, including biomass burning, fossil fuel combustion, and polluted marine components. Fossil fuel combustion organic aerosol was dominated by unsaturated alkane and was correlated with sulfur, vanadium, and nickel supporting ship and large trucks in and around the Los Angeles/Long Beach region as the dominant source. Biomass burning organic aerosol comprised a smaller unsaturated alkane fraction and larger fractions of non-acid carbonyl, amine, and carboxylic acid and was correlated with potassium and bromine. Polluted marine organic aerosol was dominated by organic hydroxyl and unsaturated alkane and was not correlated with any elemental tracers. Mass spectra of the organic aerosol support the aerosol sources determined by organic functional groups and elemental tracers and contain fragments commonly attributed to oxygenated organic aerosol (OOA), hydrocarbon-like organic aerosol (HOA), and biomass burning organic aerosol (BBOA). Comparisons of the PMF-derived Q-AMS source spectra with FTIR source spectra and functional group composition provide additional information on the relationship between commonly reported organic aerosol factors and organic functional groups in specific organic aerosol sources rather than mixtures of multiple sources.

Day, D. A.; Hawkins, L. N.; Russell, L. M.

2009-12-01

203

Carboxylation of scleroglucan for controlled crosslinking by heavy metal ions  

Microsoft Academic Search

Samples of carboxylated scleroglucan, sclerox, with a degree of carboxylation in the side-chains varying from 10 to 50% were made in order to investigate the potential of using carboxylation as a means to control subsequent gelation by heavy metal ions. The storage and loss moduli of aqueous solutions of sclerox samples as a function of time were determined at T

Bjørn T. Stokke; Arnljot Elgsaeter; Olav Smidsrød; Bjørn E. Christensen

1995-01-01

204

Functional Group and Substructure Searching as a Tool in Metabolomics  

PubMed Central

Background A direct link between the names and structures of compounds and the functional groups contained within them is important, not only because biochemists frequently rely on literature that uses a free-text format to describe functional groups, but also because metabolic models depend upon the connections between enzymes and substrates being known and appropriately stored in databases. Methodology We have developed a database named “Biochemical Substructure Search Catalogue” (BiSSCat), which contains 489 functional groups, >200,000 compounds and >1,000,000 different computationally constructed substructures, to allow identification of chemical compounds of biological interest. Conclusions This database and its associated web-based search program (http://bisscat.org/) can be used to find compounds containing selected combinations of substructures and functional groups. It can be used to determine possible additional substrates for known enzymes and for putative enzymes found in genome projects. Its applications to enzyme inhibitor design are also discussed.

Kotera, Masaaki; McDonald, Andrew G.; Boyce, Sinead; Tipton, Keith F.

2008-01-01

205

PLANT FUNCTIONAL GROUP DIVERSITY AS A MECHANISM FOR INVASION RESISTANCE  

Technology Transfer Automated Retrieval System (TEKTRAN)

A commonly cited mechanism for invasion resistance is that diverse plant assemblages use resources more completely through maximum niche occupation. Our research investigates the ability of plant functional groups in resisting invasion by a nonindigenous species, Centaurea maculosa (spotted knapwee...

206

Olfactory sensitivity and odor structure-activity relationships for aliphatic carboxylic acids in CD-1 mice.  

PubMed

Using a conditioning paradigm, the olfactory sensitivity of CD-1 mice for a homologous series of aliphatic n-carboxylic acids (ethanoic acid to n-octanoic acid) and several of their isomeric forms was investigated. With all 14 odorants, the animals significantly discriminated concentrations as low as 0.03 ppm (parts per million) from the solvent, and with four odorants the best-scoring animals even detected concentrations as low as 3 ppt (parts per trillion). Analysis of odor structure-activity relationships showed that the correlation between olfactory detection thresholds of the mice for the unbranched carboxylic acids and carbon chain length can best be described as a U-shaped function with the lowest threshold values at n-butanoic acid. A significant positive correlation between olfactory detection thresholds and carbon chain length of the carboxylic acids with their branching next to the functional carboxyl group was found. In contrast, no such correlation was found for carboxylic acids with their branching at the distal end of the carbon chain relative to the functional carboxyl group. Finally, a significant correlation was found between olfactory detection thresholds and the position of the branching of the carboxylic acids. Across-species comparisons suggest that mice are more sensitive for short-chained (C(2) to C(4)) aliphatic n-carboxylic acids than other mammalian species, but not for longer-chained ones (C(5) to C(8)). Further comparisons suggest that odor structure-activity relationships are both substance class- and species-specific. PMID:22479594

Can Güven, Selçuk; Laska, Matthias

2012-03-30

207

Screening biochars for heavy metal retention in soil: role of oxygen functional groups.  

PubMed

Oxygen-containing carboxyl, hydroxyl, and phenolic surface functional groups of soil organic and mineral components play central roles in binding metal ions, and biochar amendment can provide means of increasing these surface ligands in soil. In this study, positive matrix factorization (PMF) was first employed to fingerprint the principal components responsible for the stabilization of heavy metals (Cu, Ni, Cd, Pb) and the release of selected elements (Na, Ca, K, Mg, S, Al, P, Zn) and the pH change in biochar amended soils. The PMF analysis indicated that effective heavy metal stabilization occurred concurrently with the release of Na, Ca, S, K, and Mg originating from soil and biochar, resulting in as much as an order or magnitude greater equilibrium concentrations relative to the soil-only control. In weathered acidic soil, the heavy metal (especially Pb and Cu) stabilization ability of biochar directly correlated with the amount of oxygen functional groups revealed by the O/C ratio, pH(pzc), total acidity, and by the (1)H NMR analysis. Equilibrium speciation calculation showed minor influence of hydrolysis on the total soluble metal concentration, further suggesting the importance of binding by surface ligands of biochar that is likely to be promoted by biochar-induced pH increase. PMID:21489689

Uchimiya, Minori; Chang, SeChin; Klasson, K Thomas

2011-03-23

208

Polymer nanoparticle-protein interface. Evaluation of the contribution of positively charged functional groups to protein affinity.  

PubMed

Cationic-functionalized polymer nanoparticles (NPs) show strikingly distinct affinities to proteins depending on the nature of the cationic functional group. N-Isopropylacrylamide (NIPAm) polymer NPs incorporating three types of positively charged functional groups (guanidinium, primary amino, and quaternary ammonium groups) were prepared by precipitation polymerization. The affinities to fibrinogen, a protein with an isoelectric point (pI) of 5.5, were compared using UV-vis spectrometry and a quartz crystal microbalance (QCM). Guanidinium-containing NPs showed the highest affinity to fibrinogen. The observation is attributed to strong, specific interactions with carboxylate groups on the protein surface. The affinity of the positively charged NPs to proteins with a range of pIs revealed that protein-NP affinity is due to a combination of ionic, hydrogen bonding, and hydrophobic interactions. Protein affinity can be modulated by varying the composition of these functional monomers in the acrylamide NPs. Engineered NPs containing the guanidinium group with hydrophobic and hydrogen bonding functional groups were used in an affinity precipitation for the selective separation of fibrinogen from a plasma protein mixture. Circular dichroism (CD) revealed that the protein was not denatured in the process of binding or release. PMID:23259461

Yonamine, Yusuke; Yoshimatsu, Keiichi; Lee, Shih-Hui; Hoshino, Yu; Okahata, Yoshio; Shea, Kenneth J

2013-01-04

209

Synthesis of high-quality carbon nanodots from hydrophilic compounds: role of functional groups.  

PubMed

A simple one-pot hydrothermal approach has been demonstrated for the preparation of highly water soluble and photoluminescent carbon nanodots (C-dots) from low-cost organic compounds. We found that the compounds incorporating amino and carboxylic acid groups are suitable for the preparation of highly photoluminescent and water-soluble C-dots. PMID:22422194

Hsu, Pin-Che; Chang, Huan-Tsung

2012-03-15

210

Detection of Differential Item Functioning in Multiple Groups.  

ERIC Educational Resources Information Center

|A method is presented for detection of differential item functioning in multiple groups. This method is closely related to F. M. Lord's chi square for comparing vectors of item parameters estimated in two groups. An example is provided using data from 600 college students taking a mathematics test with and without calculators. (SLD)|

Kim, Seock-Ho; And Others

1995-01-01

211

Fourth-corner generation of plant functional response groups  

Microsoft Academic Search

Plant functional response groups (PFGs) are now widely established as a tool to investigate plant—environment relationships.\\u000a Different statistical methods to form PFGs are used in the literature. One way is to derive emergent groups by classifying\\u000a species based on correlation of biological attributes and subjecting these groups to tests of response to environmental variables.\\u000a Another way is to search for

Veiko Lehsten; Peter Harmand; Michael Kleyer

2009-01-01

212

Generalized functions asymptotically homogeneous along special transformation groups  

SciTech Connect

Distributions having (quasi)asymptotics in the asymptotic scale of regularly varying functions along special groups of transformation of independent variables are said to be asymptotically homogeneous along these transformation groups. In particular, all 'quasihomogeneous' distributions have this property. A complete description of asymptotically homogeneous distributions along a transformation group determined by a vector a element of R{sub +}{sup n} is obtained, including in the case of critical orders. Special distribution spaces are introduced and investigated to this end. The results obtained are used for the analysis of singularities of holomorphic functions in the tube domains over coordinate sectors. Bibliography: 10 titles.

Drozhzhinov, Yurii N; Zav'yalov, Boris I [Steklov Mathematical Institute, Russian Academy of Sciences, Moscow (Russian Federation)

2009-06-30

213

Eating problems and interpersonal functioning among several groups of women.  

PubMed

This paper examines the relationship between eating disorders and problems in interpersonal functioning. Questionnaires that measure eating problems, interpersonal adjustment, and general neuroticism were completed by several groups of women: anorexic patients, persons whose interests or occupations involved a concern about bodily shape or condition (dancers, models, and athletes), and members of the general public. A substantial and significant relationship was found between eating symptomatology and interpersonal functioning in all groups. However, this association survived only in the anorexic patient group when general neuroticism was partialled out. We take this to imply that psychosocial difficulties are unlikely to play a strong role in the initial development of eating problems. PMID:7560134

O'Mahony, J F; Hollwey, S

1995-05-01

214

Simple approach to carboxyl-rich materials through low-temperature heat treatment of hydrothermal carbon in air  

Microsoft Academic Search

It was found that a large number of oxygen-containing functional groups (OFGs) could be created on the surface of hydrothermal carbon (HTC) by simply heating at lower temperature in air during the course of our preliminary experiments which focused on oxidation pre-treatment of pristine HTC for the purpose of grafting functionalization. Especially carboxyl groups on HTC would increase significantly, from

Zhen Chen; Lijian Ma; Shuqiong Li; Junxia Geng; Qiang Song; Jun Liu; Chunli Wang; Hang Wang; Juan Li; Zhi Qin; Shoujian Li

2011-01-01

215

Mapping of functional groups in metal-organic frameworks.  

PubMed

We determined the heterogeneous mesoscale spatial apportionment of functional groups in a series of multivariate metal-organic frameworks (MTV-MOF-5) containing BDC (1,4-benzenedicarboxylate) linkers with different functional groups--B (BDC-NH2), E (BDC-NO2), F [(BDC-(CH3)2], H [BDC-(OC3H5)2], and I [BDC-(OC7H7)2]--using solid-state nuclear magnetic resonance measurements combined with molecular simulations. Our analysis reveals that these methods discern between random (EF), alternating (EI and EHI), and various cluster (BF) forms of functional group apportionments. This combined synthetic, characterization, and computational approach predicts the adsorptive properties of crystalline MTV-MOF systems. This methodology, developed in the context of ordered frameworks, is a first step in resolving the more general problem of spatial disorder in other ordered materials, including mesoporous materials, functionalized polymers, and defect distributions within crystalline solids. PMID:23887875

Kong, Xueqian; Deng, Hexiang; Yan, Fangyong; Kim, Jihan; Swisher, Joseph A; Smit, Berend; Yaghi, Omar M; Reimer, Jeffrey A

2013-07-25

216

Superhalogen Anions Utilizing Acidic Functional Groups As Ligands  

NASA Astrophysics Data System (ADS)

The vertical electron detachment energies (VDE) of several NaL2- and MgL3- anions (where L= -ClO4, -ClO3, -ClO2, -ClO, -NO3, -PO3, -H2PO4, -HSO4, -HCO3, -SH) were calculated at the outer valence Green function level with the 6-311++G(3df,3pd) basis sets. It was shown that various acidic functional groups may act as ligands in superhalogen anions whose electronic stabilities always exceed 4 eV. The largest values of the electron binding energies were found for the anions containing -ClO4 ligands (VDE=7.8-8.9 eV). The VDE dependencies on the origin of the ligand used (whether it is a functional group derived from strong or weak acid), chemical constitution of acidic functional groups and the electronegativity of the ligand's central atom were observed and discussed.

Anusiewicz, Iwona

2009-09-01

217

The effect of different functional groups on the ligand-promoted dissolution of NiO and other oxide minerals  

NASA Astrophysics Data System (ADS)

Sets of homologous ligands were used to probe the dissolution of oxide minerals through experiments on bunsenite (NiO). The ligand sets have primary amine, hydroxyl, and carboxyl functional groups and form five-membered, bidentate, ring complexes at the mineral surface. A set of ligands that has only two metal-coordinating functional groups (ox, en, gly) was compared with a set of larger, but similar, ligands (nta, tren) that link three sets of functional groups with a tertiary amine. Experiments were also conducted with hydroxyl ligands (tea), ammonia (NH3), and ligands containing ring nitrogen (pic). The dissolution rates of NiO(s) in the presence of these ligands established close consistency between metal detachment from a dissolving surface and the mechanisms of ligand exchange around dissolved Ni(II)-ligand complexes. The solution pH, however, is an important complicating factor. Metals compete with protons for ligand sites and this protonation changes the ligand structure and reactivity. Several types of protonation lead to different species at the mineral surface and this greatly complicates the rate laws for dissolution. The speciation will be particularly complicated for large-molecular-weight ligands with functional groups that protonate over a wide pH range. In terms of a rate law, protonation of ligand functional groups at the surface is distinct from protonation of structural oxygens at the mineral surface. These are different surface complexes (species) for the purpose of the rate law.

Ludwig, Christian; Devidal, Jean-Luc; Casey, William H.

1996-01-01

218

Intracellular localization of a group II chaperonin indicates a membrane-related function  

PubMed Central

Chaperonins are protein complexes that are believed to function as part of a protein folding system in the cytoplasm of the cell. We observed, however, that the group II chaperonins known as rosettasomes in the hyperthermophilic archaeon Sulfolobus shibatae, are not cytoplasmic but membrane associated. This association was observed in cultures grown at 60°C and 76°C or heat-shocked at 85°C by using immunofluorescence microscopy and in thick sections of rapidly frozen cells grown at 76°C by using immunogold electron microscopy. We observed that increased abundance of rosettasomes after heat shock correlated with decreased membrane permeability at lethal temperature (92°C). This change in permeability was not seen in cells heat-shocked in the presence of the amino acid analogue azetidine 2-carboxylic acid, indicating functional protein synthesis influences permeability. Azetidine experiments also indicated that observed heat-induced changes in lipid composition in S. shibatae could not account for changes in membrane permeability. Rosettasomes purified from cultures grown at 60°C and 76°C or heat-shocked at 85°C bind to liposomes made from either the bipolar tetraether lipids of Sulfolobus or a variety of artificial lipid mixtures. The presence of rosettasomes did not significantly change the transition temperature of liposomes, as indicated by differential scanning calorimetry, or the proton permeability of liposomes, as indicated by pyranine fluorescence. We propose that these group II chaperonins function as a structural element in the natural membrane based on their intracellular location, the correlation between their functional abundance and membrane permeability, and their potential distribution on the membrane surface.

Trent, Jonathan D.; Kagawa, Hiromi K.; Paavola, Chad D.; McMillan, R. Andrew; Howard, Jeanie; Jahnke, Linda; Lavin, Colleen; Embaye, Tsegereda; Henze, Christopher E.

2003-01-01

219

Surface etching of methacrylic microparticles via basic hydrolysis and introduction of functional groups for click chemistry.  

PubMed

Controlled basic hydrolysis of poly(methyl methacrylate-co-ethylene glycol dimethacrylate) P(MMA-co-EGDMA) microparticles with a diameter d50=6 ?m led to high densities of carboxylic groups at the particles' surface of up to 1.288 ?eq g(-1) (equivalent to 1.277 ?mol m(-2)). The microparticles' core has not been altered by this surface activation procedure as seen by fluorescent staining. The kinetics of the hydrolysis reaction was investigated via electrophoretic light scattering and particle charge detection employing polycation titration under shear condition. The activated microparticle's surface was subsequently exploited in carbodiimide-mediated coupling reactions using a variety of molecular reactants, that is, 11-azido-3,6,9-trioxaundecan-1-amine, cysteamine, propargylamine, and fluoresceinamine, thus enabling the introduction of chemically reactive moieties such as azides, thiols, and alkynes. Fluorescent staining of the particles' surface successfully demonstrated the versatile applications of surface functionalized microparticles via copper-catalyzed huisgen cycloaddition. Carrying on this two-step procedure in a controlled manner provides an excellent way for relatively simple but highly effective surface functionalization. PMID:23481515

Speyerer, Christian; Borchers, Kirsten; Hirth, Thomas; Tovar, Günter E M; Weber, Achim

2013-02-13

220

Solving renormalization group equations with the Lambert W function  

NASA Astrophysics Data System (ADS)

It has been known for some time that 2-loop renormalization group equations of a dimensionless parameter can be solved in a closed form in terms of the Lambert W function. We apply the method to a generic theory with a Gaussian fixed point to construct renormalization group invariant physical parameters such as a coupling constant and a physical squared mass. As a further application, we speculate a possible exact effective potential for the O(N) linear sigma model in four dimensions.

Sonoda, H.

2013-04-01

221

Immunocompatibility properties of lipid-polymer hybrid nanoparticles with heterogeneous surface functional groups  

PubMed Central

Here we report the immunological characterization of lipid-polymer hybrid nanoparticles (NPs) and propose a method to control the levels of complement activation induced by these NPs. This method consists of the highly specific modification of the NP surface with methoxyl, carboxyl, and amine groups. Hybrid NPs with methoxyl surface groups induced the lowest complement activation, whereas the NPs with amine surface groups induced the highest activation. All possible combinations among carboxyl, amine, and methoxyl groups also activated the complement system to a certain extent. All types of NPs activated the complement system primarily via the alternative pathway rather than the lectin pathway The classical pathway was activated to a very small extent by the NPs with carboxyl and amine surface groups. Human serum and plasma protein binding studies showed that these NPs had different protein binding patterns. Studies of both complement activation and coagulation activation suggested that NPs with methoxyl surface groups might be an ideal candidate for drug delivery applications, since they are not likely to cause any immunological adverse reaction in the human body.

Salvador-Morales, Carolina; Zhang, Liangfang; Langer, Robert; Farokhzad, Omid C

2009-01-01

222

Differential labeling of the catalytic subunit of cAMP-dependent protein kinase with a water-soluble carbodiimide: Identification of carboxyl groups protected by MgATP and inhibitor peptides  

SciTech Connect

The catalytic subunit of cAMP-dependent protein kinase typically phosphorylates protein substrates containing basic amino acids preceding the phosphorylation site. To identify amino acids in the catalytic subunit that might interact with these basic residues in the protein substrate, the enzyme was treated with a water-soluble carbodiimide, 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide (EDC), in the presence of ({sup 14}C)glycine ethyl ester. Several carboxyl groups in the free catalytic subunit were radiolabeled after the catalytic subunit was modified with EDC and ({sup 14}C)glycine ethyl ester. After purification and sequencing, these carboxyl groups were identified as Glu 107, Glu 170, Asp 241, Asp 328, Asp 329, Glu 331, Glu 332, and Glu 333. Three of these amino acids, Glu 331, Glu 107, and Asp 241, were labeled regardless of the presence of substrates, while Glue 333 and Asp 329 were modified to a slight extent only in the free catalytic subunit. Glu 170, Asp 328, and Glu 332 were all very reactive in the apoenzyme but fully protected from modification by EDC in the presence of MgATP and an inhibitor peptide. In any case, the results indicate a dramatic change in the accessibility of this region of the catalytic subunit in the presence and absence of substrates.

Buechler, J.A.; Taylor, S.S. (Univ. of California, San Diego, La Jolla (USA))

1990-02-20

223

Species, functional groups, and thresholds in ecological resilience.  

PubMed

The cross-scale resilience model states that ecological resilience is generated in part from the distribution of functions within and across scales in a system. Resilience is a measure of a system's ability to remain organized around a particular set of mutually reinforcing processes and structures, known as a regime. We define scale as the geographic extent over which a process operates and the frequency with which a process occurs. Species can be categorized into functional groups that are a link between ecosystem processes and structures and ecological resilience. We applied the cross-scale resilience model to avian species in a grassland ecosystem. A species' morphology is shaped in part by its interaction with ecological structure and pattern, so animal body mass reflects the spatial and temporal distribution of resources. We used the log-transformed rank-ordered body masses of breeding birds associated with grasslands to identify aggregations and discontinuities in the distribution of those body masses. We assessed cross-scale resilience on the basis of 3 metrics: overall number of functional groups, number of functional groups within an aggregation, and the redundancy of functional groups across aggregations. We assessed how the loss of threatened species would affect cross-scale resilience by removing threatened species from the data set and recalculating values of the 3 metrics. We also determined whether more function was retained than expected after the loss of threatened species by comparing observed loss with simulated random loss in a Monte Carlo process. The observed distribution of function compared with the random simulated loss of function indicated that more functionality in the observed data set was retained than expected. On the basis of our results, we believe an ecosystem with a full complement of species can sustain considerable species losses without affecting the distribution of functions within and across aggregations, although ecological resilience is reduced. We propose that the mechanisms responsible for shaping discontinuous distributions of body mass and the nonrandom distribution of functions may also shape species losses such that local extinctions will be nonrandom with respect to the retention and distribution of functions and that the distribution of function within and across aggregations will be conserved despite extinctions. PMID:22443132

Sundstrom, Shana M; Allen, Craig R; Barichievy, Chris

2012-04-01

224

Isoperimetric functions for subdirect products and Bestvina-Brady groups  

NASA Astrophysics Data System (ADS)

In this thesis we investigate the Dehn functions of two different classes of groups: subdirect products, in particular subdirect products of limit groups; and Bestvina-Brady groups. Let D = ?_1 times ... times ?_n be a direct product of n geq 3 finitely presented groups and let H be a subgroup of D. Suppose that each ?_i contains a finite index subgroup ?_i' leq ?_i such that the commutator subgroup [D', D'] of D' = ?_1' times ... times ?_n' is contained in H. Suppose furthermore that, for each i, the subgroup ?_i H has finite index in D. We prove that H is finitely presented and satisfies an isoperimetric inequality given in terms of area-radius pairs for the ?_i and the dimension of (D'/H) otimes Q. In the case that each ?_i admits a polynomial-polynomial area-radius pair, it will follow that H satisfies a polynomial isoperimetric inequality. As a corollary we obtain that if K is a subgroup of a direct product of n limit groups and if K is of type FP_m(Q), where m = max {2, n-1}, then K is finitely presented and satisfies a polynomial isoperimetric inequality. In particular, we obtain that all finitely presented subgroups of a direct product of at most 3 limit groups satisfy a polynomial isoperimetric inequality. We also prove that if B is a finitely presented Bestvina-Brady group, then B admits a quartic isoperimetric function.

Dison, Will

2008-10-01

225

Dissection of the Carboxyl-Terminal Domain of the Proteasomal Subunit Rpn11 in Maintenance of Mitochondrial Structure and Function  

Microsoft Academic Search

We have previously demonstrated that the C-terminal part of Rpn11, a deubiquitinating enzyme in the lid of the proteasome, is essential for maintaining a correct cell cycle and normal mitochondrial morphology and function. The two roles are apparently unlinked as the mitochondrial role is mapped to the Carboxy-terminus, whereas the catalytic deubiquitinating activity is found within the N-terminal region. The

Teresa Rinaldi; Line Hofmann; Alessia Gambadoro; Raynald Cossard; Nurit Livnat-Levanon; Michael H. Glickman; Laura Frontali; Agnes Delahodde

2007-01-01

226

Synthesis of mono functional carboxylic acid poly(methyl methacrylate) in aqueous medium using sur-iniferter. Application to the synthesis of graft copolymers polyethylene- g-poly(methyl methacrylate) and the compatibilization of LDPE\\/PVDF blends  

Microsoft Academic Search

Carboxylic acid mono functional poly(methyl methacrylate) was prepared by emulsion photopolymerization using 4-diethylthiocarbamoylsulfanylmethyl benzoic acid (DTBA) as sur-iniferter agent. DTBA is efficient to obtain mono functional polymers with a linear evolution of Mn vs. monomer conversion up to 60%. Beyond 60% monomer conversion, Mn decreases drastically and addition of a supplementary surfactant seems to disturb the effect of sur-iniferter. Secondly,

J. Kwak; P. Lacroix-Desmazes; J. J. Robin; B. Boutevin; N. Torres

2003-01-01

227

Analysis of synthetic fuels for functional group determination  

Microsoft Academic Search

A method for the structural characterisation of complex mixtures has been developed which uses elemental analysis, NMR and other analytical data to determine functional group concentrations. The method was tested with mixtures of known composition and was applied to a set of hydrodesulphurised coal liquids. The results are compared with mass spectrometric data and with the results of established methods

Leonidas. Petrakis; David T. Allen; George R. Gavalas; Bruce C. Gates

1983-01-01

228

Pelagic functional group modeling: Progress, challenges and prospects  

Microsoft Academic Search

In this paper, we review the state of the art and major challenges in current efforts to incorporate biogeochemical functional groups into models that can be applied on basin-wide and global scales, with an emphasis on models that might ultimately be used to predict how biogeochemical cycles in the ocean will respond to global warming. We define the term “biogeochemical

Raleigh R. Hood; Edward A. Laws; Robert A. Armstrong; Nicholas R. Bates; Christopher W. Brown; Craig A. Carlson; Fei Chai; Scott C. Doney; Paul G. Falkowski; Richard A. Feely; Marjorie A. M. Friedrichs; Michael R. Landry; J. Keith Moore; David M. Nelson; Tammi L. Richardson; Baris Salihoglu; Markus Schartau; Dierdre A. Toole; Jerry D. Wiggert

2006-01-01

229

Pelagic functional group modeling: Progress, challenges and prospects  

NASA Astrophysics Data System (ADS)

In this paper, we review the state of the art and major challenges in current efforts to incorporate biogeochemical functional groups into models that can be applied on basin-wide and global scales, with an emphasis on models that might ultimately be used to predict how biogeochemical cycles in the ocean will respond to global warming. We define the term "biogeochemical functional group" to refer to groups of organisms that mediate specific chemical reactions in the ocean. Thus, according to this definition, "functional groups" have no phylogenetic meaning—these are composed of many different species with common biogeochemical functions. Substantial progress has been made in the last decade toward quantifying the rates of these various functions and understanding the factors that control them. For some of these groups, we have developed fairly sophisticated models that incorporate this understanding, e.g. for diazotrophs (e.g. Trichodesmium), silica producers (diatoms) and calcifiers (e.g. coccolithophorids and specifically Emiliania huxleyi). However, current representations of nitrogen fixation and calcification are incomplete, i.e., based primarily upon models of Trichodesmium and E. huxleyi, respectively, and many important functional groups have not yet been considered in open-ocean biogeochemical models. Progress has been made over the last decade in efforts to simulate dimethylsulfide (DMS) production and cycling (i.e., by dinoflagellates and prymnesiophytes) and denitrification, but these efforts are still in their infancy, and many significant problems remain. One obvious gap is that virtually all functional group modeling efforts have focused on autotrophic microbes, while higher trophic levels have been completely ignored. It appears that in some cases (e.g., calcification), incorporating higher trophic levels may be essential not only for representing a particular biogeochemical reaction, but also for modeling export. Another serious problem is our tendency to model the organisms for which we have the most validation data (e.g., E. huxleyi and Trichodesmium) even when they may represent only a fraction of the biogeochemical functional group we are trying to represent. When we step back and look at the paleo-oceanographic record, it suggests that oxygen concentrations have played a central role in the evolution and emergence of many of the key functional groups that influence biogeochemical cycles in the present-day ocean. However, more subtle effects are likely to be important over the next century like changes in silicate supply or turbulence that can influence the relative success of diatoms versus dinoflagellates, coccolithophorids and diazotrophs. In general, inferences drawn from the paleo-oceanographic record and theoretical work suggest that global warming will tend to favor the latter because it will give rise to increased stratification. However, decreases in pH and Fe supply could adversely impact coccolithophorids and diazotrophs in the future. It may be necessary to include explicit dynamic representations of nitrogen fixation, denitrification, silicification and calcification in our models if our goal is predicting the oceanic carbon cycle in the future, because these processes appear to play a very significant role in the carbon cycle of the present-day ocean and they are sensitive to climate change. Observations and models suggest that it may also be necessary to include the DMS cycle to predict future climate, though the effects are still highly uncertain. We have learned a tremendous amount about the distributions and biogeochemical impact of bacteria in the ocean in recent years, yet this improved understanding has not yet been incorporated into many of our models. All of these considerations lead us toward the development of increasingly complex models. However, recent quantitative model intercomparison studies suggest that continuing to add complexity and more functional groups to our ecosystem models may lead to decreases in predictive ability if the models are not p

Hood, Raleigh R.; Laws, Edward A.; Armstrong, Robert A.; Bates, Nicholas R.; Brown, Christopher W.; Carlson, Craig A.; Chai, Fei; Doney, Scott C.; Falkowski, Paul G.; Feely, Richard A.; Friedrichs, Marjorie A. M.; Landry, Michael R.; Keith Moore, J.; Nelson, David M.; Richardson, Tammi L.; Salihoglu, Baris; Schartau, Markus; Toole, Dierdre A.; Wiggert, Jerry D.

2006-03-01

230

The Group Evolution Multiwavelength Study (GEMS): bimodal luminosity functions in galaxy groups  

NASA Astrophysics Data System (ADS)

We present B- and R-band luminosity functions (LFs) for a sample of 25 nearby groups of galaxies. We find that the LFs of the groups with low X-ray luminosity (LX < 1041.7 erg s-1) are significantly different from those of the X-ray brighter groups, showing a prominent dip around MB=-18. While both categories show lack of late-type galaxies in their central regions, X-ray dim groups also show a more marked concentration of optical luminosity towards the centre. A toy simulation shows that in the low velocity dispersion environment, as in the X-ray dim group, dynamical friction would facilitate more rapid merging, thus depleting intermediate-luminosity galaxies to form a few giant central galaxies, resulting in the prominent dip seen in our LFs. We suggest that X-ray dim (or low velocity dispersion) groups are the present sites of rapid dynamical evolution rather than their X-ray bright counterparts, and may be the modern precursors of fossil groups. We predict that these groups of low velocity dispersion would harbour younger stellar populations than groups or clusters with higher velocity dispersion.

Miles, Trevor A.; Raychaudhury, Somak; Forbes, Duncan A.; Goudfrooij, Paul; Ponman, Trevor J.; Kozhurina-Platais, Vera

2004-12-01

231

Functional equations and uniformity for local zeta functions of nilpotent groups  

Microsoft Academic Search

We investigate in this paper the zeta function ?,p(s) associated to a nilpotent group ? introduced in (GSS). This zeta function counts the subgroups H ? whose profinite completion ˆ H is isomorphic to the profinite completion ˆ ?. By representing ?,p (s) as an integral with respect to the Haar measure on the algebraic automorphism group G of the

Marcus Du Sautoy; Alexander Lubotzky

1996-01-01

232

Synthesis of Amide Functionalized Carbon Nanotubes.  

National Technical Information Service (NTIS)

A covalent, amide-bond interconnection between functionalized single- wall carbon nanotubes (SWNTs) is reported. SWNTs covalently connected via an amide bond were prepared by coupling the carboxylic acid group from one SWNT with the amine group on a diffe...

C. Whitaker I. C. Uber J. R. Heckert

2007-01-01

233

Epigenetic regulation of cardiac development and function by Polycomb Group and Trithorax Group Proteins  

PubMed Central

Heart disease is a leading cause of death and disability in developed countries. Heart disease includes a broad range of diseases that affect the development and/or function of the cardiovascular system. Some of these diseases, such as congenital heart defects, are present at birth. Others develop over time and may be influenced by both genetic and environmental factors. Many of the known heart diseases are associated with abnormal expression of genes. Understanding the factors and mechanisms that regulate gene expression in the heart is essential for the detection, treatment and prevention of heart diseases. Polycomb Group (PcG) and Trithorax Group (TrxG) proteins are special families of chromatin factors that regulate developmental gene expression in many tissues and organs. Accumulating evidence suggests that these proteins are important regulators of development and function of the heart as well. A better understanding of their roles and functional mechanisms will translate into new opportunities for combating heart disease.

Wang, Q. Tian

2012-01-01

234

Functional gene group analysis identifies synaptic gene groups as risk factor for schizophrenia  

PubMed Central

Schizophrenia is a highly heritable disorder with a polygenic pattern of inheritance and a population prevalence of ?1%. Previous studies have implicated synaptic dysfunction in schizophrenia. We tested the accumulated association of genetic variants in expert-curated synaptic gene groups with schizophrenia in 4673 cases and 4965 healthy controls, using functional gene group analysis. Identifying groups of genes with similar cellular function rather than genes in isolation may have clinical implications for finding additional drug targets. We found that a group of 1026 synaptic genes was significantly associated with the risk of schizophrenia (P=7.6 × 10?11) and more strongly associated than 100 randomly drawn, matched control groups of genetic variants (P<0.01). Subsequent analysis of synaptic subgroups suggested that the strongest association signals are derived from three synaptic gene groups: intracellular signal transduction (P=2.0 × 10?4), excitability (P=9.0 × 10?4) and cell adhesion and trans-synaptic signaling (P=2.4 × 10?3). These results are consistent with a role of synaptic dysfunction in schizophrenia and imply that impaired intracellular signal transduction in synapses, synaptic excitability and cell adhesion and trans-synaptic signaling play a role in the pathology of schizophrenia.

Lips, E S; Cornelisse, L N; Toonen, R F; Min, J L; Hultman, C M; Holmans, P A; O'Donovan, M C; Purcell, S M; Smit, A B; Verhage, M; Sullivan, P F; Visscher, P M; Posthuma, D

2012-01-01

235

Minimal representations of conformal groups and generalized Laguerre functions  

NASA Astrophysics Data System (ADS)

We give a unified construction of the minimal representation of a finite cover G of the conformal group of a (non necessarily euclidean) Jordan algebra V. This representation is realized on the L^2-space of the minimal orbit {O} of the structure group L of V. We construct its corresponding (mathfrak{g},mathfrak{k})-module and show that it can be integrated to a unitary irreducible representation of G on L^2({O}). In particular, we obtain a unified approach to the two most prominent minimal representations, namely the Segal-Shale-Weil representation of the metaplectic group textup{Mp}(n,{R}) and the minimal representation of textup{O}(p+1,q+1) which was recently studied by T. Kobayashi, G. Mano and B. Ørsted. In the second part we investigate special functions which give rise to mathfrak{k}-finite vectors in the representation. Various properties of these special functions such as differential equations, recurrence relations and integral formulas connect to the representation theory involved. Finally, we define the conformal inversion operator {F}_{{O}} by the action of the longest Weyl group element. {F}_{{O}} is a unitary operator on L^2({O}) of order 2. We show that the action of {F}_{{O}} on radial functions is given by a special case of Meijer's G-transform.

Möllers, Jan

2010-09-01

236

Submicron Organic Aerosol Function Groups during the International Chemistry Experiment in the Arctic LOwer Troposphere (ICEALOT)  

NASA Astrophysics Data System (ADS)

Aerosol organic mass (OM) components are expected to have significant direct and indirect impacts on Arctic climate, especially during springtime Arctic haze. The chemical and physical properties of OM in Arctic aerosol remain largely unconstrained. The R/V Knorr traveled between Iceland and the Barents Sea during the ice-free months of March and April of 2008 and collected submicron particles on teflon filters for Fourier Transform Infrared (FTIR) spectroscopy to identify and quantify organic functional groups. Time series and composition are presented along with air mass back trajectories to indicate source regions. Early findings identify alcohols, alkanes, and carboxylic acids, with smaller amounts of amines, aromatics, alkenes and carbonyls. These data show the important contributions of organic oxygen and nitrogen in the Arctic region. Single particle analysis by Near-edge X-ray Absorption Fine Structure (NEXAFS) Scanning Transmission X- ray Microscopy (STXM) provides additional information about the distribution and morphology of the types of organic particles. Comparison to collocated simultaneous measurements by other techniques showed good agreement for OM and oxygenated organic fractions.

Russell, L. M.; Shaw, P. M.; Quinn, P. K.; Bates, T. S.

2008-12-01

237

Absence of PTHrP Nuclear Localization and Carboxyl Terminus Sequences Leads to Abnormal Brain Development and Function  

PubMed Central

We assessed whether the nuclear localization sequences (NLS) and C terminus of parathyroid hormone-related protein (PTHrP) play critical roles in brain development and function. We used histology, immunohistochemistry, histomorphometry, Western blots and electrophysiological recordings to compare the proliferation and differentiation of neural stem cells, neuronal hippocampal synaptic transmission, and brain phenotypes including shape and structures, in Pthrp knock-in mice, which express PTHrP (1–84), a truncated form of the protein that is missing the NLS and the C-terminal region of the protein, and their wild-type littermates. Results showed that Pthrp knock-in mice display abnormal brain shape and structures; decreased neural cell proliferative capacity and increased apoptosis associated with up-regulation of cyclin dependent kinase inhibitors p16, p21, p27 and p53 and down-regulation of the Bmi-1 oncogene; delayed neural cell differentiation; and impaired hippocampal synaptic transmission and plasticity. These findings provide in vivo experimental evidence that the NLS and C-terminus of PTHrP are essential not only for the regulation of neural cell proliferation and differentiation, but also for the maintenance of normal neuronal synaptic transmission and plasticity.

Gu, Zhen; Liu, Yahong; Zhang, Yongjie; Jin, Shulei; Chen, Qi; Goltzman, David; Karaplis, Andrew; Miao, Dengshun

2012-01-01

238

Efficient fluorescent recognition of carboxylates in aqueous media using facilely electrosynthesized poly(9-aminofluorene).  

PubMed

A variety of carboxylates were recognized using poly(9-aminofluorene) (P9AF) in the HEPES buffer (pH 7.4), and a proposed possible mechanism was proposed as following. The intermolecular hydrogen bonding interactions resulted in electron transfer between P9AF and carboxylates. P9AF was facilely electrosynthesized in boron trifluoride diethyl etherate and could be used as an efficient fluorescent sensing material for the detection of AcO(-). On binding to AcO(-), fluorescence quenching of P9AF was demonstrated by a maximum 80 % reduction in the fluorescence intensity, while no obvious fluorescence change could be observed in the presence of some other common anions. Some different carboxylates could be recognized at different levels by P9AF. Substituent groups in carboxylates could affect the intermolecular interaction between carboxylates and P9AF. These could be explained by a possible mechanism that hydrogen bonding was the main way of intermolecular interactions between P9AF and carboxylates, which was further confirmed by absorption spectra monitoring and density functional calculations. The significant advantage of this strategy is that it does not require a prequenching procedure and the polymer can be used directly for analyte detection. PMID:23715936

Zhang, Ge; Wen, Yangping; Li, Yuzhen; Xu, Jingkun; Guo, Chaoqun; Lu, Baoyang; Zhu, Danhua

2013-05-29

239

XPS of nitrogen-containing functional groups on activated carbon  

Microsoft Academic Search

XPS is used to study the binding energy of the Cls, Nls and Ols photoelectrons of surface groups on several nitrogen-containing activated carbons. Specific binding energies are assigned to amide (399.9 eV). lactam and imidc (399.7 eV). pyridine (398.7 eV), pyrrole (400.7 eV), alkylamine. secondary amide and N-alkylimide (399.9 eV) and trialkylaminc (399.7 cV) functional groups on activated carbon. Supporting

R. J. J. Jansen; H. van Bekkum

1995-01-01

240

Functional group dependent dissociative electron attachment to simple organic molecules  

NASA Astrophysics Data System (ADS)

Dissociative electron attachment (DEA) cross sections for simple organic molecules, namely, acetic acid, propanoic acid, methanol, ethanol, and n-propyl amine are measured in a crossed beam experiment. We find that the H- ion formation is the dominant channel of DEA for these molecules and takes place at relatively higher energies (>4 eV) through the core excited resonances. Comparison of the cross sections of the H- channel from these molecules with those from NH3, H2O, and CH4 shows the presence of functional group dependence in the DEA process. We analyze this new phenomenon in the context of the results reported on other organic molecules. This discovery of functional group dependence has important implications such as control in electron induced chemistry and understanding radiation induced damage in biological systems.

Prabhudesai, Vaibhav S.; Nandi, Dhananjay; Kelkar, Aditya H.; Krishnakumar, E.

2008-04-01

241

Protist functional groups in a sublittoral estuarine epibenthic area  

Microsoft Academic Search

Protist communities were studied monthly at Santoña beach (Cantabrian Sea, Spain) throughout one year. Twelve abiotic parameters\\u000a were analyzed. The following functional groups (defined according to the preferential source of food) were considered: photoautotrophs\\u000a (P), saprotrophs (S), bacterivores (B), algivores (A), non-selectives (N), and predators or raptors (R). A total of 269 species\\u000a was found. The percentage of species in

Gregorio Fernandez-Leborans; Delia Fernandez-Fernandez

2002-01-01

242

Grazing effects on plant functional group diversity in Mediterranean shrublands  

Microsoft Academic Search

Grazing is one of the prevalent human activities that even today are taking place inside protected areas with direct or indirect\\u000a effects on ecosystems. In this study we analyzed the effects of grazing on plant species diversity, plant functional group\\u000a (PFG) diversity and community composition of shrublands. We analyzed plant diversity data from 582 sampling plots located\\u000a in 66 protected

Alexandra D. Papanikolaou; Nikolaos M. Fyllas; Antonios D. Mazaris; Panayiotis G. Dimitrakopoulos; Athanasios S. Kallimanis; John D. Pantis

243

Functional-group-tolerant catalytic migratory oxidative coupling of nitrones.  

PubMed

A copper-catalyzed migratory oxidative-coupling reaction between nitrones and various ethers/amines exhibited high functional-group tolerance. Even in aqueous media, the reaction proceeded efficiently. For practical use of this catalysis, a unique sequential Huisgen cycloaddition was demonstrated. Mechanistic investigations revealed that the reaction proceeded through oxidative catalytic activation of ethers/amines to afford iminium/oxonium intermediates by concurrent dual one-electron abstractions by copper(II) and oxyl radicals. PMID:22763980

Hashizume, Shogo; Oisaki, Kounosuke; Kanai, Motomu

2012-07-04

244

Functional endonasal sinus surgery (FESS) in the pediatric age group.  

PubMed

Functional endonasal sinus surgery has become a popular mode of surgical treatment for sinus disease in the United States. The literature has primarily addressed its use in the adult population. We present our series of 57 children who underwent functional endonasal sinus surgery. The children ranged in age from 3 to 15 years. Follow-up was from 3 to 13 months. Fifty-four of the patients were treated for chronic or recurrent sinus infections. Three patients were treated for complications of acute sinusitis. All patients tolerated the procedure well, and there were no major complications. We conclude that functional endonasal sinus surgery is a safe procedure in the pediatric age group. Although postoperative follow-up in the series was very short, early results appear encouraging. The technical approach is similar to that used in the adult procedure. The pediatric procedure, however, requires a follow-up nasal endoscopy under general anesthesia to achieve optimal results. PMID:2918799

Gross, C W; Gurucharri, M J; Lazar, R H; Long, T E

1989-03-01

245

Boron-containing amino carboxylic acid compounds and uses thereof  

DOEpatents

Novel compounds which are useful for boron neutron capture therapy (BNCT) are disclosed. The compounds comprise a stable boron-containing group and an aminocycloalkane carboxylic acid group or a boronated acyclic hydrocarbon-linked amino carboxylic acid. Methods for synthesis of the compounds and for use of the compounds in BNCT are disclosed.

Kabalka, George W. (Knoxville, TN); Srivastava, Rajiv R. (Knoxville, TN)

2000-03-14

246

Functionalized adamantane tectons used in the design of mixed-ligand copper(II) 1,2,4-triazolyl/carboxylate metal-organic frameworks.  

PubMed

Bistriazoles, 1,3-bis(1,2,4-triazol-4-yl)propane (tr(2)pr) and 1,3-bis(1,2,4-triazol-4-yl)adamantane (tr(2)ad), were examined in combination with the rigid tetratopic 1,3,5,7-adamantanetetracarboxylic acid (H(4)-adtc) platform for the construction of neutral heteroleptic copper(II) metal-organic frameworks. Two coordination polymers, [{Cu(4)(OH)(2)(H(2)O)(2)}{Cu(4)(OH)(2)}(tr(2)pr)(2)(H-adtc)(4)]·2H(2)O (1) and [Cu(4)(OH)(2)(tr(2)ad)(2)(H-adtc)(2)(H(2)O)(2)]·3H(2)O (2), were synthesized and structurally characterized. In complexes 1 and 2, the N(1),N(2)-1,2,4-triazolyl (tr) and ?(3)-OH(-) groups serve as complementary bridges between adjacent metal centers supporting the tetranuclear dihydroxo clusters. The structure of 1 represents a unique association of two different kinds of centrosymmetrical {Cu(4)(OH)(2)} units in a tight 3D framework, while in compound 2, another configuration type of acentric tetranuclear metal clusters is organized in a layered 3,6-hexagonal motif. In both cases, the {Cu(4)(OH)(2)} secondary building block and trideprotonated carboxylate H-adtc(3-) can be viewed as covalently bound six- and three-connected nodes that define the net topology. The tr ligands, showing ?(3)- or ?(4)-binding patterns, introduce additional integrating links between the neighboring {Cu(4)(OH)(2)} fragments. A variable-temperature magnetic susceptibility study of 2 demonstrates strong antiferromagnetic intracluster coupling (J(1) = -109 cm(-1) and J(2) = -21 cm(-1)), which combines for the bulk phase with a weak antiferromagnetic intercluster interaction (zj = -2.5 cm(-1)). PMID:23294097

Senchyk, Ganna A; Lysenko, Andrey B; Krautscheid, Harald; Rusanov, Eduard B; Chernega, Alexander N; Krämer, Karl W; Liu, Shi-Xia; Decurtins, Silvio; Domasevitch, Konstantin V

2013-01-07

247

Density functional theory calculation of cyclic carboxylic phosphorus mixed anhydrides as possible intermediates in biochemical reactions: implications for the Pro-Tide approach.  

PubMed

Cyclic acyl phosphoramidates (CAPAs) are important components in several fundamental biological reactions such as protein synthesis and phosphorylation. These structures are particularly interesting in the nucleotide pro-drug approach, Pro-Tide, since they are putative intermediates in one of the hydrolysis steps required for activation. The central role played by the amino acid carboxylate function suggests first the formation of a cyclic mixed phosphorus anhydride, rapidly followed by water attack. To investigate such speculations, we performed quantum mechanical calculations using the B3LYP/6-311+G** level of theory for the plausible mechanisms of action considered. In the five-membered ring case, transition state theory demonstrated how the overall, gas-phase, mechanism of action could be split into two in-line addition-elimination (A-E) steps separated by a penta-coordinate phosphorane intermediate. The difference between five-membered and six-membered ring first A-E was also explored, revealing a single step, unimolecular reaction for the six-membered ring A-E profile. Implicit solvent contribution further confirmed the importance of CAPAs as reactive intermediates in such kind of reactions. Lastly, the second A-E pathway was analyzed to understand the complete pathway of the reaction. This analysis is the first attempt to clarify the putative mechanism of action involved in the activation of Pro-Tides and casts light also on the possible mechanism of action involved in primordial protein syntheses, strengthening the hypothesis of a common cyclic mixed phosphorus anhydride species as a common intermediate. PMID:22318882

Ricci, Antonio; Brancale, Andrea

2012-02-08

248

Functional group diversity of bee pollinators increases crop yield  

PubMed Central

Niche complementarity is a commonly invoked mechanism underlying the positive relationship between biodiversity and ecosystem functioning, but little empirical evidence exists for complementarity among pollinator species. This study related differences in three functional traits of pollinating bees (flower height preference, daily time of flower visitation and within-flower behaviour) to the seed set of the obligate cross-pollinated pumpkin Cucurbita moschata Duch. ex Poir. across a land-use intensity gradient from tropical rainforest and agroforests to grassland in Indonesia. Bee richness and abundance changed with habitat variables and we used this natural variation to test whether complementary resource use by the diverse pollinator community enhanced final yield. We found that pollinator diversity, but not abundance, was positively related to seed set of pumpkins. Bees showed species-specific spatial and temporal variation in flower visitation traits and within-flower behaviour, allowing for classification into functional guilds. Diversity of functional groups explained even more of the variance in seed set (r2=45%) than did species richness (r2=32%) highlighting the role of functional complementarity. Even though we do not provide experimental, but rather correlative evidence, we can link spatial and temporal complementarity in highly diverse pollinator communities to pollination success in the field, leading to enhanced crop yield without any managed honeybees.

Hoehn, Patrick; Tscharntke, Teja; Tylianakis, Jason M; Steffan-Dewenter, Ingolf

2008-01-01

249

Characterization of Sea Lettuce Surface Functional Groups by Potentiometric Titrations  

NASA Astrophysics Data System (ADS)

In pursuit of our ultimate goal to better understand the prodigious capacity of the marine macroalga Ulva lactuca (sea lettuce) for adsorbing a broad range of dissolved trace metals from seawater, we performed an initial characterization of its surface functional groups. Specifically, the number of distinct functional groups as well as their individual bulk concentrations and acid dissociation constants (pKas) were determined by potentiometric titrations in NaCl solutions of various ionic strengths (I = 0.01-5.0 M), under inert nitrogen atmosphere at 25°C. Depending on the ionic strength, Ulva samples were manually titrated down to pH 2 or 3 with 1 N HCl and then up to pH 10 with 1 N NaOH in steps of 0.1-0.2 units, continuously monitoring pH with a glass combination electrode. Titrations of a dehydrated Ulva standard reference material (BCR-279) were compared with fresh Ulva tissue cultured in our laboratory. A titration in filtered natural seawater was also compared with one in an NaCl solution of equal ionic strength. Equilibrium constants for the ionization of water in NaCl solutions as a function of ionic strength were obtained from the literature. Fits to the titration data ([H]T vs. pH) were performed with the FITEQL4.0 computer code using non-electrostatic 3-, 4-, and 5-site models, either by fixing ionic strength at its experimental value or by allowing it to be extrapolated to zero, while considering all functional group pKas and bulk concentrations as adjustable parameters. Since pKas and bulk concentrations were found to be strongly correlated, the latter were also fixed in some cases to further constrain the pKas. Whereas these calculations are currently ongoing, preliminary results point to three, possibly four, functional groups with pKas of about 4.1, 6.3, and 9.5 at I = 0. Bulk concentrations of the three groups are very similar, about 5-6×10-4 mol/g based on dry weight, which suggests that all are homogeneously distributed over the surface and probably part of a single macromolecular scaffold. Fresh Ulva tissue appears to contain the same three functional groups but at lower concentrations, based on wet weight. The titration in natural seawater was largely dominated by the non-carbonate alkalinity of the solution and could not be robustly modeled. Results of fits with ionic strengths fixed at their experimental values indicate that the pKas of all three groups display prominent Debije-Hückel-type behavior, hence that these acid dissociation reactions involve a different mechanism than metal-proton exchange reactions on mineral surfaces, whose distribution coefficients (i.e., equilibrium constants) generally show a weak ionic strength dependence.

Ebling, A. M.; Schijf, J.

2008-12-01

250

Organized thiol functional groups in mesoporous core shell colloids  

SciTech Connect

The co-condensation in situ of tetraethoxysilane (TEOS) and mercaptopropyltrimethoxysilane (MPTMS) using cetyltrimethylammonium bromide (CTAB) as a template results in the synthesis of multilayered mesoporous structured SiO{sub 2} colloids with 'onion-like' chemical environments. Thiol groups were anchored to an inner selected SiO{sub 2} porous layer in a bilayered core shell particle producing different chemical regions inside the colloidal layered structure. X-Ray Photoelectron Spectroscopy (XPS) shows a preferential anchoring of the -SH groups in the double layer shell system, while porosimetry and simple chemical modifications confirm that pores are accessible. We can envision the synthesis of interesting colloidal objects with defined chemical environments with highly controlled properties. - Graphical abstract: Mesoporous core shell SiO{sub 2} colloids with organized thiol groups. Highlights: Black-Right-Pointing-Pointer Double shell mesoporous silica colloids templated with CTAB. Black-Right-Pointing-Pointer Sequential deposition of mesoporous SiO{sub 2} layers with different chemistries. Black-Right-Pointing-Pointer XPS shows the selective functionalization of mesoporous layers with thiol groups.

Marchena, Martin H. [Gerencia Quimica, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), Avda. Gral. Paz 1499, B1650KNA Buenos Aires (Argentina); Granada, Mara [Centro Atomico Bariloche-CNEA, 8400 San Carlos de Bariloche (Argentina); Instituto Balseiro-Centro Atomico Bariloche-CNEA, San Carlos de Bariloche 8400 (Argentina); Bordoni, Andrea V. [Gerencia Quimica, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), Avda. Gral. Paz 1499, B1650KNA Buenos Aires (Argentina); Joselevich, Maria [Asociacion Civil Expedicion Ciencia, Cabrera 4948, C1414BGP Buenos Aires (Argentina); Troiani, Horacio [Centro Atomico Bariloche-CNEA, 8400 San Carlos de Bariloche (Argentina); Instituto Balseiro-Centro Atomico Bariloche-CNEA, San Carlos de Bariloche 8400 (Argentina); Williams, Federico J. [DQIAQyF-INQUIMAE FCEN, Universidad de Buenos Aires, Ciudad Universitaria, Pabellon II, C1428EHA Buenos Aires (Argentina); Wolosiuk, Alejandro, E-mail: wolosiuk@cnea.gov.ar [Gerencia Quimica, Centro Atomico Constituyentes, Comision Nacional de Energia Atomica (CNEA), Avda. Gral. Paz 1499, B1650KNA Buenos Aires (Argentina)

2012-03-15

251

Biogenic oxidized organic functional groups in aerosol particles from a mountain forest site and their similarities to laboratory chamber products  

NASA Astrophysics Data System (ADS)

Submicron particles collected at Whistler, British Columbia, at 1020 m a.s.l. during May and June 2008 on Teflon filters were analyzed by Fourier transform infrared (FTIR) and X-ray fluorescence (XRF) techniques for organic functional groups (OFG) and elemental composition. Organic mass (OM) concentrations ranged from less than 0.5 to 3.1 ?g m-3, with a project mean and standard deviation of 1.3±1.0 ?g m-3 and 0.21±0.16 ?g m-3 for OM and sulfate, respectively. On average, organic hydroxyl, alkane, and carboxylic acid groups represented 34%, 33%, and 23% of OM, respectively. Ketone, amine and organosulfate groups constituted 6%, 5%, and <1% of the average organic aerosol composition, respectively. Measurements of volatile organic compounds (VOC), including isoprene and monoterpenes from biogenic VOC (BVOC) emissions and their oxidation products (methyl-vinylketone / methacrolein, MVK/MACR), were made using co-located proton transfer reaction mass spectrometry (PTR-MS). We present chemically-specific evidence of OFG associated with BVOC emissions. Positive matrix factorization (PMF) analysis attributed 65% of the campaign OM to biogenic sources, based on the correlations of one factor to monoterpenes and MVK/MACR. The remaining fraction was attributed to anthropogenic sources based on a correlation to sulfate. The functional group composition of the biogenic factor (consisting of 32% alkane, 25% carboxylic acid, 21% organic hydroxyl, 16% ketone, and 6% amine groups) was similar to that of secondary organic aerosol (SOA) reported from the oxidation of BVOCs in laboratory chamber studies, providing evidence that the magnitude and chemical composition of biogenic SOA simulated in the laboratory is similar to that found in actual atmospheric conditions. The biogenic factor OM is also correlated to dust elements, indicating that dust may act as a non-acidic SOA sink. This role is supported by the organic functional group composition and morphology of single particles, which were analyzed by scanning transmission X-ray microscopy near edge X-ray absorption fine structure (STXM-NEXAFS).

Schwartz, R. E.; Russell, L. M.; Sjostedt, S. J.; Vlasenko, A.; Slowik, J. G.; Abbatt, J. P. D.; MacDonald, A. M.; Li, S. M.; Liggio, J.; Toom-Sauntry, D.; Leaitch, W. R.

2010-06-01

252

Biogenic oxidized organic functional groups in aerosol particles from a mountain forest site and their similarities to laboratory chamber products  

NASA Astrophysics Data System (ADS)

Submicron particles collected at Whistler, British Columbia, at 1020 masl during May and June 2008 on Teflon filters were analyzed by Fourier transform infrared (FTIR) and X-ray fluorescence (XRF) techniques for organic functional groups (OFG) and elemental composition. Organic mass (OM) ranged from less than 0.5 to 3.1?g m-3, with a project mean and standard deviation of 1.3±1.0 ?g m-3 and 0.21±0.16 ?g m-3 for OM and sulfate, respectively. On average, organic hydroxyl, alkane, and carboxylic acid groups represented 34%, 33%, and 23% of OM, respectively. Ketone, amine and organosulfate groups constituted 6%, 5%, and <1% of the average organic aerosol composition, respectively. Measurements of volatile organic compounds (VOC), including isoprene and monoterpenes from biogenic VOC (BVOC) emissions and their oxidation products (methyl-vinylketone/methacrolein, MVK/MACR), were made using co-located proton transfer reaction mass spectrometry (PTR-MS). We present chemically-specific evidence of OFG associated with BVOC emissions. Positive matrix factorization (PMF) analysis attributed 65% of the campaign OM to biogenic sources, based on the correlations of one factor to monoterpenes and MVK/MACR. The remaining fraction was attributed to anthropogenic sources based on a correlation to sulfate. The functional group composition of the biogenic factor (consisting of 32% alkane, 25% carboxylic acid, 2% organic hydroxyl, 16% ketone, and 6% amine groups) was similar to that of secondary organic aerosol (SOA) reported from the oxidation of BVOCs in laboratory chamber studies, providing evidence that the magnitude and chemical composition of biogenic SOA simulated in the laboratory is similar to that found in actual atmospheric conditions. The biogenic factor OM is also correlated to dust elements, indicating that dust may act as a non-acidic SOA sink. This role is supported by the organic functional group composition and morphology of single particles, which were analyzed by scanning transmission X-ray microscopy near edge X-ray absorption fine structure (STXM-NEXAFS).

Schwartz, R. E.; Russell, L. M.; Sjosted, S. J.; Vlasenko, A.; Slowik, J. G.; Abbatt, J. P. D.; MacDonald, A. M.; Li, S. M.; Liggio, J.; Toom-Sauntry, D.; Leaitch, W. R.

2010-02-01

253

Functional renormalization group flow of the effective Hamiltonian action  

NASA Astrophysics Data System (ADS)

After a brief review of the definition and properties of the quantum effective Hamiltonian action, we describe its renormalization flow by a functional renormalization group equation. This equation can be used for a nonperturbative quantization and study of theories with bare Hamiltonians that are not quadratic in the momenta. As an example, the vacuum energy and gap of quantum mechanical models are computed. Extensions of this framework to quantum field theories are discussed. In particular, one possible Lorentz-covariant approach for simple scalar field theories is developed. Fermionic degrees of freedom, being naturally described by a first order formulation, can easily be accommodated in this approach.

Vacca, G. P.; Zambelli, L.

2012-10-01

254

Multicritical unbinding phenomena and nonlinear functional renormalization group  

NASA Astrophysics Data System (ADS)

Using a nonlinear functional renormalization-group approach, we study the problem of unbinding phenomena both for interfaces and membranes. Our numerical and analytical solutions of the differential recursion relation confirm the existence of the ``unusual bifurcation'' of the fixed-point potentials describing unbinding at the upper critical dimension d=d*. However, in addition to one critical and one purely repulsive potential, we find an infinite family of multicritical potentials bifurcating from the drifting fixed point. The values for the scaling indices, which are singular near d*, are calculated here exactly to leading orders in ?=d*-d and are shown to behave as ?2/3.

David, F.; Leibler, S.

1990-06-01

255

Prediction of compounds’ biological function (metabolic pathways) based on functional group composition  

Microsoft Academic Search

Efficient in silico screening approaches may provide valuable hints on biological functions of the compound-candidates, which\\u000a could help to screen functional compounds either in basic researches on metabolic pathways or drug discovery. Here, we introduce\\u000a a machine learning method (Nearest Neighbor Algorithm) based on functional group composition of compounds to the analysis\\u000a of metabolic pathways. This method can quickly map

Yu-Dong Cai; Ziliang Qian; Lin Lu; Kai-Yan Feng; Xin Meng; Bing Niu; Guo-Dong Zhao; Wen-Cong Lu

2008-01-01

256

Functional groups of ryanodine receptors in rat ventricular cells  

PubMed Central

Ryanodine receptors (RyR2s) are ion channels in the sarcoplasmic reticulum (SR) that are responsible for Ca2+ release in rat ventricular myocytes. Localization of RyR2s is therefore crucial for our understanding of contraction and other Ca2+-dependent intracellular processes. Recent results (e.g. circular waves and Ca2+ sparks in perinuclear area) raised questions about the classical views of RyR2 distribution and organization within ventricular cells. A Ca2+ spark is a fluorescent signal reflecting the activation of a small group of RyR2s. Frequency and spatio-temporal characteristics of Ca2+ sparks depend on the state of cytoplasmic and intraluminal macromolecular complexes regulating cardiac RyR2 function. We employed electron microscopy, confocal imaging of spontaneous Ca2+ sparks and immunofluorescence to visualize the distribution of RyR2s in ventricular myocytes and to evaluate the local involvement of the macromolecular complexes in regulation of functional activity of the RyR2 group. An electron microscopy study revealed that the axial tubules of the transverse–axial tubular system probably do not have junctions with the network SR (nSR). The nSR was found to be wrapped around intermyofibrillar mitochondria and contained structures similar to feet of the junctional cleft. Treatment of ventricular myocytes with antibodies against RyR2 showed that in addition to the junctional SR, a small number of RyR2s can be localized at the middle of the sarcomere and in the zone of perinuclear mitochondria. Recordings of spontaneous Ca2+ sparks showed the existence of functional groups of RyR2s in these intracellular compartments. We found that within the sarcomere about 20% of Ca2+ sparks were not colocalized with the zone of the junctional or corbular SR (Z-line zone). The spatio-temporal characteristics of sparks found in the Z-line and A-band zones were very similar, whereas sparks from the zone of the perinuclear mitochondria were about 25% longer. Analysis of the initiation sites of Ca2+ sparks within the same junctional SR cluster suggested that 18–25 RyR2s are in the functional group producing a spark. Because of the similarity of the spatio-temporal characteristics of sarcomeric sparks and ultrastructural characteristics of nSR, we suggest that the functional groups of RyR2s in the middle of the sarcomere are macromolecular complexes of ?20 RyR2s with regulatory proteins. Our data allowed us to conclude that a significant number of functional RyR2s is located in the middle of the sarcomere and in the zone of perinuclear mitochondria. These RyR2s could contribute to excitation–contraction coupling, mitochondrial and nuclear signalling, and Ca2+-dependent gene regulation, but their existence raises many additional questions.

Lukyanenko, V; Ziman, A; Lukyanenko, A; Salnikov, V; Lederer, W J

2007-01-01

257

High Lipophilicty of Perfluoroalkyl Carboxylate and Sulfonate  

PubMed Central

Here we report on remarkably high lipophilicity of perfluoroalkyl carboxylate and sulfonate. A lipophilic nature of this emerging class of organic pollutants has been hypothesized as an origin of their bioaccumulation and toxicity. Both carboxylate and sulfonate, however, are considered hydrophilic while perfluroalkyl groups are not only hydrophobic but also oleophobic. Partition coefficients of homologous series of perfluoroalkyl and alkyl carboxylates between water and n-octanol were determined as a measure of their lipophilicity by ion-transfer cyclic voltammetry. Very similar lipophilicity of perfluoroalkyl and alkyl chains with the same length is demonstrated experimentally for the first time by fragment analysis of the partition coefficients. This finding is important for pharmaceutical and biomedical applications of perfluoroalkyl compounds. Interestingly, ?2 orders of magnitude higher lipophilicity of a perfluoroalkyl carboxylate or sulfonate in comparison to its alkyl counterpart is ascribed nearly exclusively to their oxoanion groups. The higher lipophilicity originates from a strong electron-withdrawing effect of the perfluoroalkyl group on the adjacent oxoanion group, which is weakly hydrated to decrease its hydrophilicity. In fact, the inductive effect is dramatically reduced for a fluorotelomer with an ethylene spacer between perfluorohexyl and carboxylate groups, which is only as lipophilic as its alkyl counterpart, nonanoate, and is 400 times less lipophilic than perfluorononanoate. The high lipophilicity of perfluoroalkyl carboxylate and sulfonate implies that their permeation across such a thin lipophilic membrane as a bilayer lipid membrane is limited by their transfer at a membrane/water interface. The limiting permeability is lower and less dependent on their lipophilicity than the permeability controlled by their diffusion in the membrane interior as assumed in the classical solubility-diffusion model.

Jing, Ping; Rodgers, Patrick J.; Amemiya, Shigeru

2009-01-01

258

Characterization of Oxygen Containing Functional Groups on Carbon Materials with Oxygen K-edge X-ray Absorption Near Edge Structure Spectroscopy  

SciTech Connect

Surface functional groups on carbon materials are critical to their surface properties and related applications. Many characterization techniques have been used to identify and quantify the surface functional groups, but none is completely satisfactory especially for quantification. In this work, we used oxygen K-edge X-ray absorption near edge structure (XANES) spectroscopy to identify and quantify the oxygen containing surface functional groups on carbon materials. XANES spectra were collected in fluorescence yield mode to minimize charging effect due to poor sample conductivity which can potentially distort XANES spectra. The surface functional groups are grouped into three types, namely carboxyl-type, carbonyl-type, and hydroxyl-type. XANES spectra of the same type are very similar while spectra of different types are significantly different. Two activated carbon samples were analyzed by XANES. The total oxygen contents of the samples were estimated from the edge step of their XANES spectra, and the identity and abundance of different functional groups were determined by fitting of the sample XANES spectrum to a linear combination of spectra of the reference compounds. It is concluded that oxygen K-edge XANES spectroscopy is a reliable characterization technique for the identification and quantification of surface functional groups on carbon materials.

K Kim; P Zhu; L Na; X Ma; Y Chen

2011-12-31

259

Individual functional ROI optimization via maximization of group-wise consistency of structural and functional profiles.  

PubMed

Studying connectivities among functional brain regions and the functional dynamics on brain networks has drawn increasing interest. A fundamental issue that affects functional connectivity and dynamics studies is how to determine the best possible functional brain regions or ROIs (regions of interest) for a group of individuals, since the connectivity measurements are heavily dependent on ROI locations. Essentially, identification of accurate, reliable and consistent corresponding ROIs is challenging due to the unclear boundaries between brain regions, variability across individuals, and nonlinearity of the ROIs. In response to these challenges, this paper presents a novel methodology to computationally optimize ROIs locations derived from task-based fMRI data for individuals so that the optimized ROIs are more consistent, reproducible and predictable across brains. Our computational strategy is to formulate the individual ROI location optimization as a group variance minimization problem, in which group-wise consistencies in functional/structural connectivity patterns and anatomic profiles are defined as optimization constraints. Our experimental results from multimodal fMRI and DTI data show that the optimized ROIs have significantly improved consistency in structural and functional profiles across individuals. These improved functional ROIs with better consistency could contribute to further study of functional interaction and dynamics in the human brain. PMID:22281931

Li, Kaiming; Guo, Lei; Zhu, Dajiang; Hu, Xintao; Han, Junwei; Liu, Tianming

2012-07-01

260

Functional renormalization-group approach to decaying turbulence  

NASA Astrophysics Data System (ADS)

We reconsider the functional renormalization-group (FRG) approach to decaying Burgers turbulence, and extend it to decaying Navier-Stokes and surface quasi-geostrophic turbulence. The method is based on a renormalized small-time expansion, equivalent to a loop expansion, and naturally produces a dissipative anomaly and a cascade after a finite time. We explicitly calculate and analyze the one-loop FRG equations in the zero-viscosity limit as a function of the dimension. For Burgers turbulence they reproduce the FRG equation obtained in the context of random manifolds, extending previous results of one of us. Breakdown of energy conservation due to shocks and the appearance of a direct energy cascade corresponds to failure of dimensional reduction in the context of disordered systems. For Navier-Stokes turbulence in three dimensions, the velocity-velocity correlation function acquires a linear dependence on the distance, ?2 = 1, in the inertial range, instead of Kolmogorov’s ?2 = 2/3 however, the possibility remains for corrections at two- or higher-loop order. In two dimensions, we obtain a numerical solution which conserves energy and exhibits an inverse cascade, with explicit analytical results for both large and small distances, in agreement with the scaling proposed by Batchelor. In large dimensions, the one-loop FRG equation for Navier-Stokes turbulence converges to that of Burgers turbulence.

Fedorenko, Andrei A.; Le Doussal, Pierre; Jörg Wiese, Kay

2013-04-01

261

Thiazolidinone Amides, Thiazolidine Carboxylic Acid Amides, Methods of Making, and Uses Thereof.  

National Technical Information Service (NTIS)

Substituted thiazolidinone carboxylic acid amides and substituted thiazolidine carboxylic acid amides according to formulae (I) and (II) are disclosed where the various substituent groups are as defined in the specification. Methods of making these compou...

D. D. Miller E. Hurh J. T. Dalton V. Gududuru

2004-01-01

262

Plant Functional Group Composition Modifies the Effects of Precipitation Change on Grassland Ecosystem Function  

PubMed Central

Temperate grassland ecosystems face a future of precipitation change, which can alter community composition and ecosystem functions through reduced soil moisture and waterlogging. There is evidence that functionally diverse plant communities contain a wider range of water use and resource capture strategies, resulting in greater resistance of ecosystem function to precipitation change. To investigate this interaction between composition and precipitation change we performed a field experiment for three years in successional grassland in southern England. This consisted of two treatments. The first, precipitation change, simulated end of century predictions, and consisted of a summer drought phase alongside winter rainfall addition. The second, functional group identity, divided the plant community into three groups based on their functional traits- broadly described as perennials, caespitose grasses and annuals- and removed these groups in a factorial design. Ecosystem functions related to C, N and water cycling were measured regularly. Effects of functional groupidentity were apparent, with the dominant trend being that process rates were higher under control conditions where a range of perennial species were present. E.g. litter decomposition rates were significantly higher in plots containing several perennial species, the group with the highest average leaf N content. Process rates were also very strongly affected by the precipitation change treatmentwhen perennial plant species were dominant, but not where the community contained a high abundance of annual species and caespitose grasses. This contrasting response could be attributable to differing rooting patterns (shallower structures under annual plants, and deeper roots under perennials) and faster nutrient uptake in annuals compared to perennials. Our results indicate that precipitation change will have a smaller effect on key process rates in grasslandscontaining a range of perennial and annual species, and that maintaining the presence of key functional groups should be a crucial consideration in future grassland management.

Fry, Ellen L.; Manning, Pete; Allen, David G. P.; Hurst, Alex; Everwand, Georg; Rimmler, Martin; Power, Sally A.

2013-01-01

263

Plant functional group composition modifies the effects of precipitation change on grassland ecosystem function.  

PubMed

Temperate grassland ecosystems face a future of precipitation change, which can alter community composition and ecosystem functions through reduced soil moisture and waterlogging. There is evidence that functionally diverse plant communities contain a wider range of water use and resource capture strategies, resulting in greater resistance of ecosystem function to precipitation change. To investigate this interaction between composition and precipitation change we performed a field experiment for three years in successional grassland in southern England. This consisted of two treatments. The first, precipitation change, simulated end of century predictions, and consisted of a summer drought phase alongside winter rainfall addition. The second, functional group identity, divided the plant community into three groups based on their functional traits- broadly described as perennials, caespitose grasses and annuals- and removed these groups in a factorial design. Ecosystem functions related to C, N and water cycling were measured regularly. Effects of functional groupidentity were apparent, with the dominant trend being that process rates were higher under control conditions where a range of perennial species were present. E.g. litter decomposition rates were significantly higher in plots containing several perennial species, the group with the highest average leaf N content. Process rates were also very strongly affected by the precipitation change treatmentwhen perennial plant species were dominant, but not where the community contained a high abundance of annual species and caespitose grasses. This contrasting response could be attributable to differing rooting patterns (shallower structures under annual plants, and deeper roots under perennials) and faster nutrient uptake in annuals compared to perennials. Our results indicate that precipitation change will have a smaller effect on key process rates in grasslandscontaining a range of perennial and annual species, and that maintaining the presence of key functional groups should be a crucial consideration in future grassland management. PMID:23437300

Fry, Ellen L; Manning, Pete; Allen, David G P; Hurst, Alex; Everwand, Georg; Rimmler, Martin; Power, Sally A

2013-02-20

264

Heterogeneous Catalyst Design by Multiple Functional Group Positioning in Organic-Inorganic Materials: On the Route to Analogs of Multifunctional Enzymes  

NASA Astrophysics Data System (ADS)

Enzymes catalyze reactions with high rates and selectivities through the sophisticated use of cooperative interactions between neighboring functional groups within an active site. For example, the “catalytic triad” in proteases is capable of accelerating the cleavage of amides by 1011 through neighboring interactions between carboxylic acid, imidazole, and alcohol sites. Guided by these principles, heterogeneous catalysts having two different types of functional groups have been prepared, and the cooperative behavior have been demonstrated with catalytic reactions in the liquid phase. Cooperative interactions between thiols and sulfonic acids and between incompatible acid and base groups are achievable with rates and selectivities that are superior to homogeneous systems, especially for the latter case wherein there is no reactivity.

Margelefsky, Eric L.; Zeidan, Ryan K.; Davis, Mark E.

265

Water Mediated Ligand Functional Group Cooperativity: The Contribution of a Methyl Group to Binding Affinity is Enhanced by a COO? Group Through Changes in the Structure and Thermo dynamics of the Hydration Waters of Ligand-Thermolysin Complexes  

PubMed Central

Ligand functional groups can modulate the contributions of one another to the ligand-protein binding thermodynamics, producing either positive or negative cooperativity. Data presented for four thermolysin phosphonamidate inhibitors demonstrate that the differential binding free energy and enthalpy caused by replacement of a H with a Me group, which binds in the well-hydrated S2? pocket, are more favorable in presence of a ligand carboxylate. The differential entropy is however less favorable. Dissection of these differential thermodynamic parameters, X-ray crystallography, and density-functional theory calculations suggest that these cooperativities are caused by variations in the thermodynamics of the complex hydration shell changes accompanying the H?Me replacement. Specifically, the COO? reduces both the enthalpic penalty and the entropic advantage of displacing water molecules from the S2? pocket, and causes a subsequent acquisition of a more enthalpically, less entropically, favorable water network. This study contributes to understanding the important role water plays in ligand-protein binding.

Nasief, Nader N; Tan, Hongwei; Kong, Jing; Hangauer, David

2012-01-01

266

Selective homogeneous hydrogenation of biogenic carboxylic acids with [Ru(TriPhos)H]+: a mechanistic study.  

PubMed

Selective hydrogenation of biogenic carboxylic acids is an important transformation for biorefinery concepts based on platform chemicals. We herein report a mechanistic study on the homogeneously ruthenium/phosphine catalyzed transformations of levulinic acid (LA) and itaconic acid (IA) to the corresponding lactones, diols, and cyclic ethers. A density functional theory (DFT) study was performed and corroborated with experimental data from catalytic processes and NMR investigations. For [Ru(TriPhos)H](+) as the catalytically active unit, a common mechanistic pathway for the reduction of the C?O functionality in aldehydes, ketones, lactones, and even free carboxylic acids could be identified. Hydride transfer from the Ru-H group to the carbonyl or carboxyl carbon is followed by protonation of the resulting Ru-O unit via ?-bond metathesis from a coordinated dihydrogen molecule. The energetic spans for the reduction of the different functional groups increase in the order aldehyde < ketone < lactone ? carboxylic acid. This reactivity pattern as well as the absolute values are in full agreement with experimentally observed activities and selectivities, forming a rational basis for further catalyst development. PMID:21786816

Geilen, Frank M A; Engendahl, Barthel; Hölscher, Markus; Klankermayer, Jürgen; Leitner, Walter

2011-08-18

267

Synthesis of highly lipophilic crown ether carboxylic acids  

SciTech Connect

Synthetic routes to eight highly lipophilic crown ether carboxylic acids are described. Structural variations within this series of crown ether carboxylic acids include changes in the crown ether cavity size, the lipophilic group attachment site, and the basicity of the crown ether oxygens.

Bartsch, R.A.; Liu, Y.; Kang, S.I.; Son, B.; Heo, G.S.; Hipes, P.G.; Bills, L.J.

1983-01-01

268

Functional analysis of Kluyveromyces lactis carboxylic acids permeases: heterologous expression of KlJEN1 and KlJEN2 genes  

Microsoft Academic Search

The present work describes a detailed physiological and molecular characterization of the mechanisms of transport of carboxylic\\u000a acids in Kluyveromyces lactis. This yeast species presents two homologue genes to JEN1 of Saccharomyces cerevisiae: KlJEN1 encodes a monocarboxylate permease and KlJEN2 encodes a dicarboxylic acid permease. In the strain K.\\u000a lactis GG1888, expression of these genes does not require an inducer

Odília Queirós; Leonor Pereira; Sandra Paiva; Pedro Moradas-Ferreira; Margarida Casal

2007-01-01

269

A soybean gene encoding ? 1 -pyrroline-5-carboxylate reductase was isolated by functional complementation in Escherichia coli and is found to be osmoregulated  

Microsoft Academic Search

Summary We have isolated several cDNA clones encoding ?11-pyrroline-5-carboxylate reductase (P5CR, l-proline: NAD(P)+ 5-oxidoreductase, EC 1.5.1.2) which catalyzes the terminal step in proline biosynthesis, by direct complementation of a proC mutation in Escherichia coli with an expression library of soybean root nodule cDNA. The library was constructed in the ? ZapII vector, converted to a plasmid library by in vivo

Ashton J. Delauney; Desh Pal S. Verma

1990-01-01

270

Carboxylic acid sorption regeneration process  

DOEpatents

Carboxylic acids are sorbed from aqueous feedstocks into an organic liquid phase or onto a solid adsorbent. The acids are freed from the sorbent phase by treating it with aqueous alkylamine thus forming an alkylammonium carboxylate which is dewatered and decomposed to the desired carboxylic acid and the alkylamine.

King, C. Judson (Kensington, CA); Poole, Loree J. (Baton Rouge, LA)

1995-01-01

271

Observations of Adolescent Peer Group Interactions as a Function of Within- and Between-Group Centrality Status  

ERIC Educational Resources Information Center

|Observations of adolescent (n = 258; M age = 15.45) peer group triads (n = 86) were analyzed to identify conversation and interaction styles as a function of within-group and between-group centrality status. Group members' discussions about hypothetical dilemmas were coded for agreements, disagreements, commands, and opinions. Interactions during…

Ellis, Wendy E.; Dumas, Tara M.; Mahdy, Jasmine C.; Wolfe, David A.

2012-01-01

272

Stoichiometric methylation of calcineurin by protein carboxyl O-methyltransferase and its effects on calmodulin-stimulated phosphatase activity.  

PubMed Central

Calcineurin, a calmodulin-stimulated protein phosphatase, was a substrate for purified bovine brain protein carboxyl O-methyltransferase (protein O-methyltransferase; EC 2.1.1.24) and incorporated up to 2 mol of CH3 per mol of calcineurin. Carboxyl methylation was dependent on the concentrations of S-adenosyl-L-[methyl-3H]methionine and was prevented by addition of the carboxyl methylation inhibitor S-adenosylhomocysteine. The stoichiometry of methyl group incorporation was related to the ratio of methyltransferase/calcineurin. The rate of spontaneous hydrolysis of carboxyl methylester groups on calcineurin increased rapidly above pH 6.5 with those on native carboxyl-methylated calcineurin substantially more labile than for trichloracetic acid-precipitated calcineurin. Polyacrylamide gel electrophoresis in the presence of NaDodSO4 (pH 2.4) confirmed that the A subunit of calcineurin (Mr = 61,000) was the primary site of carboxyl methylation with little, if any, modification of the B subunit (Mr = 18,000). When carboxyl-methylated calcineurin (approximately 1-2 mol of CH3 per mol of protein) was assayed for p-nitrophenyl phosphatase activity at pH 6.5, a marked inhibition of calmodulin-stimulated activity was observed while there was little effect on Mn2+-stimulated phosphatase activity. Thus, calcineurin appears to be an excellent substrate for protein carboxyl O-methylation and this modification, which impairs calmodulin stimulation of phosphatase activity, may be of functional significance. Images

Billingsley, M L; Kincaid, R L; Lovenberg, W

1985-01-01

273

tert-Butyl 2-sulfanylidene-2,3-dihydro-1H-imidazole-1-carboxyl-ate  

PubMed Central

In the title mol­ecule, C8H12N2O2S, the imidazole ring forms a dihedral angle of 5.9?(2)° with the mean plane of the carboxyl­ate group. In the crystal, mol­ecules are linked by pairs of N—H?S hydrogen bonds, forming inversion dimers.

Lee, Pei-Chi; Guo, Yi-Cin; Huang, Bor-Hunn; Chen, Ming-Jen

2012-01-01

274

Polyanion-polycation complex formation as a function of the position of the functional groups  

Microsoft Academic Search

A method consisting of the combination of turbidimetry and conductometry was investigated to detect polyanion-polycation complex formation. We used ‘strong acid’ polyelectrolytes varying in charge density and ‘strong basic’ polyelectrolytes varying in the length of the spacer groups and in the accessibility of the quaternary ammonium function. Our systematic investigations have shown a predominantly 1:1 stoichiometry at the turbidimetric as

Peter Zarras; Otto Vogl

1996-01-01

275

Nitric Acid Dehydration Using Perfluoro Carboxylate and Mixed Sulfonate/Carboxylate Membranes  

SciTech Connect

Perfluoro ionomer membranes are tetrafluoro ethylene-based materials with microheterogeneous structures consisting of a hydrophobic polymer backbone and a hydrophilic side-chain cluster region. Due to the ionomer cluster morphology, these films exhibit unique transport properties. Recent investigations with perfluoro sulfonate and perfluoro sulfonate/carboxylate composite polymers have demonstrated their value in the dehydration of nitric acid and they show potential as an alternative to conventional, energy intensive unit operations in the concentration of acid feeds. As a result, investigations were conducted to determine the feasibility of using pure perfluoro carboxylate and mixed perfluoro sulfonate/carboxylate films for the dehydration of nitric acid because of the speculation of improved water selectivity of the carboxylate pendant chain. During the first phase of these investigations the effort was focused on generating a thin, solution cast perfluoro carboxylate ionomer film, to evaluate the general, chemical and physical characteristics of the polymer, and to assess the material's aqueous transport performance (flux and nitrate separation efficiencies) in pervaporation and high-pressure environments. Results demonstrated that generating robust solution-cast films was difficult yet a number of membranes survived high trans-membrane pressures up to 700 psig. General characterization of the solution cast product showed reduced ion exchange capacities when compared with thicker, ''as received'' perfluoro carboxylate and similar sulfonate films. Small angle x-ray scattering analysis results suggested that the solution cast carboxylate films contained a small fraction of sulfonate terminated side-chains. Aqueous transport experimentation showed that permeate fluxes for both pure water and nitric acid were approximately two orders of magnitude smaller for the carboxylate solution cast membranes when compared to their sulfonate counterparts of similar thickness (Nafion{trademark} 111). Additionally, nitric acid separation efficiencies ({alpha}) were approximately one order of magnitude higher for the carboxylate solution cast films when compared to Nafion{trademark} 111. The second phase of our work included the generation of thin carboxylate films made by the chemical synthesis perfluoro sulfonate and mixed sulfonate/carboxylate polymers from a perfluoro sulfonyl fluoride precursor, the characterization of the newly generated material, and a study of the transport characteristics of these membranes. Transport studies consisted of the dehydration of nitric acid feeds by pervaporation. In addition, the initial hypothesis was expanded to include demonstration that transmembrane flux and separation efficiencies are a function of the ratio between sulfonate and carboxylate terminated side chains of the perfluoro ionomer. Investigations demonstrated the ability to generate in- house films with varying sulfonate/carboxylate concentrations from commercially available perfluoro sulfonyl fluoride material, and showed that the converted films could be characterized using Fourier transform infrared (FTIR) and x-ray fluorescence (XRF) spectroscopy. Finally, the mixed films where subjected to nitric acid dehydration transport tests and a relationship was found to exist between sulfonate/carboxylate pendant chain ratio and both flux and water separation capability. In summary, experimental results confirmed that, when compared to Nafion 111{trademark}, the mixed film's bulk fluxes decrease by approximately three orders of magnitude and the water separation factor increases by as much as two orders of magnitude as the carboxylate side-chain content was increased from 0 (pure sulfonate film) to 53 mole%, supporting the hypothesis given for this effort. It was observed that the water selectivity improved for both the solution cast perfluoro carboxylate and mixed perfluoro sulfonate/carboxylate films when judged against similar perfluoro sulfonate materials. Of great benefit was that during the investigation a number of research tools w

R.L. Ames

2004-09-01

276

Metabolism of Cyclohexane Carboxylic Acid by Alcaligenes Strain W1  

PubMed Central

Thirty-three microorganisms capable of growth with cyclohexane carboxylate as the sole source of carbon were isolated from mud, water, and soil samples from the Aberystwyth area. Preliminary screening and whole-cell oxidation studies suggested that, with one exception, all of the strains metabolized the growth substrate by beta-oxidation of the coenzyme A ester. This single distinctive strain, able to oxidize rapidly trans-4-hydroxycyclohexane carboxylate, 4-ketocyclohexane carboxylate, p-hydroxybenzoate, and protocatechuate when grown with cyclohexane carboxylate, was classified as a strain of Alcaligenes and given the number W1. Enzymes capable of converting cyclohexane carboxylate to p-hydroxybenzoate were induced by growth with the alicyclic acid and included the first unambiguous specimen of a cyclohexane carboxylate hydroxylase. Because it is a very fragile protein, attempts to stabilize the cyclohexane carboxylate hydroxylase so that a purification procedure could be developed have consistently failed. In limited studies with crude cell extracts, we found that hydroxylation occurred at the 4 position, probably yielding the trans isomer of 4-hydroxycyclohexane carboxylate. Simultaneous measurement of oxygen consumption and reduced nicotinamide adenine dinucleotide oxidation, coupled with an assessment of reactant stoichiometry, showed the enzyme to be a mixed-function oxygenase. Mass spectral analysis enabled the conversion of cyclohexane carboxylate to p-hydroxybenzoate by cell extracts to be established unequivocally, and all of our data were consistent with the pathway: cyclohexane carboxylate ? trans-4-hydroxycyclohexane carboxylate ? 4-ketocyclohexane carboxylate ? p-hydroxybenzoate. The further metabolism of p-hydroxybenzoate proceeded by meta fission and by the oxidative branch of the 2-hydroxy-4-carboxymuconic semialde-hyde-cleaving pathway.

Taylor, David G.; Trudgill, Peter W.

1978-01-01

277

The size of hydroxyl groups in solution and the changes in size associated with the ionization of phenolic, carboxylic and amino groups in phenolic quaternary ammonium salts, nicotine and some amino acids: possible implications for drug-water and drug-receptor interactions.  

PubMed Central

Size in solution can be expressed either as the apparent molal volume at infinite dilution (phi 0v) amd the concentration parameter (j) or as the partial molal volume of the solute at infinite dilution (V0(2)) and the concentration parameter for the solute or solvent (qs or qw). Although calculated differently, these are derived from the same results and are equivalent. From measurement with phenolic quaternary ammonium salts, including compounds with high nicotine-like activity, the apparent size of the hydroxyl group in water is small and variable. Phenolic groups are slightly larger than alcoholic groups, which should be better hydrogen donors. By measuring the volume change associated with ionisation it is possible to measure the size of charged groups such as phenate and carboxylate; these are much smaller than phenolic and carboxyl. Ammonium groups, however, are only slightly smaller than the corresponding amines. The zwitterion forms of amino acids are associated with a minimum in volume but the volume changes increase with chain length from glycine to gamma-aminobutyric acid. Groups separated by less than this distance interact in their effects on water. Decreases in volume or unexpectedly small increments in apparent molal volume represent decreases in entropy which must be taken into account in drug-water-receptor interactions. Although they may be offset by enthalpy changes, they should favour binding because there is more scope for an increase in entropy. This might explain the association of the small apparent size in water of the hydroxyl group in many compounds with its effects of their affinity for receptors.

Barlow, R. B.

1980-01-01

278

Carboxylic ester hydrolase  

Microsoft Academic Search

Summary  When using clinical criteria, both falsely positive and falsely negative diagnoses of acute pancreatitis (AP) are often made.\\u000a Based on a clinical study, elevated serum levels of the pancreatic lipolytic enzyme carboxylic ester hydrolase (CEH) was recently\\u000a suggested to be a highly specific marker of acute pancreatitis.\\u000a \\u000a To determine the sensitivity of the test for AP, a study on patients

P. Jonas Blind; Marcus Biichler; Lars Bläckberg; Yvonne Andersson; Waldemar Uhi; Hans G. Beger; Olle Hernell

1991-01-01

279

Individual Performance as a Function of Group Contingencies and Group Size  

Microsoft Academic Search

The effects of small group incentive plans on the individual performance of a simple assembly task were studied in a simulated work environment. Subjects were 28 college students who worked under an individual monetaty incentive system, and then under a group incentive system in groups of two, four, five or nine. Following the group incentive condition, subjects again worked under

Karen G. Stoneman; Alyce M. Dickinson

1989-01-01

280

Experimental and theoretical studies on the functionalization reactions of 4-benzoyl-1,5-diphenyl-1 H -pyrazole-3-carboxylic acid and-acid chloride with various aminophenols  

Microsoft Academic Search

The 1H-pyrazole-3-carboxylic acid 1 was converted via reactions of its acid chloride 2 with various aminophenol derivatives 3a--d into the corresponding N-(hydroxyphenyl)-1H-pyrazole-3-carboxamides 4a--d, respectively, in good yields (34–53%). The reactions of 1 or 2 with 3 in benzene or toluene for 5–7 h with no catalytic amounts of base lead to the formation of the products 4. The structures of all

Ismail Y?ld?r?m; Fatma Kandemirli

2006-01-01

281

Plant Species and Functional Group Combinations Affect Green Roof Ecosystem Functions  

PubMed Central

Background Green roofs perform ecosystem services such as summer roof temperature reduction and stormwater capture that directly contribute to lower building energy use and potential economic savings. These services are in turn related to ecosystem functions performed by the vegetation layer such as radiation reflection and transpiration, but little work has examined the role of plant species composition and diversity in improving these functions. Methodology/Principal Findings We used a replicated modular extensive (shallow growing- medium) green roof system planted with monocultures or mixtures containing one, three or five life-forms, to quantify two ecosystem services: summer roof cooling and water capture. We also measured the related ecosystem properties/processes of albedo, evapotranspiration, and the mean and temporal variability of aboveground biomass over four months. Mixtures containing three or five life-form groups, simultaneously optimized several green roof ecosystem functions, outperforming monocultures and single life-form groups, but there was much variation in performance depending on which life-forms were present in the three life-form mixtures. Some mixtures outperformed the best monocultures for water capture, evapotranspiration, and an index combining both water capture and temperature reductions. Combinations of tall forbs, grasses and succulents simultaneously optimized a range of ecosystem performance measures, thus the main benefit of including all three groups was not to maximize any single process but to perform a variety of functions well. Conclusions/Significance Ecosystem services from green roofs can be improved by planting certain life-form groups in combination, directly contributing to climate change mitigation and adaptation strategies. The strong performance by certain mixtures of life-forms, especially tall forbs, grasses and succulents, warrants further investigation into niche complementarity or facilitation as mechanisms governing biodiversity-ecosystem functioning relationships in green roof ecosystems.

Lundholm, Jeremy; MacIvor, J. Scott; MacDougall, Zachary; Ranalli, Melissa

2010-01-01

282

Application of macrobenthos functional groups to estimate the ecosystem health in a semi-enclosed bay.  

PubMed

In this study, the functional group concept was first applied to evaluate the ecosystem health of Bohai Bay. Macrobenthos functional groups were defined according to feeding types and divided into five groups: a carnivorous group (CA), omnivorous group (OM), planktivorous group (PL), herbivorous group (HE), and detritivorous group (DE). Groups CA, DE, OM, and PL were identified, but the HE group was absent from Bohai Bay. Group DE was dominant during the study periods. The ecosystem health was assessed using a functional group evenness index. The functional group evenness values of most sampling stations were less than 0.40, indicating that the ecosystem health was deteriorated in Bohai Bay. Such deterioration could be attributed to land reclamation, industrial and sewage effluents, oil pollution, and hypersaline water discharge. This study demonstrates that the functional group concept can be applied to ecosystem health assessment in a semi-enclosed bay. PMID:23849956

Peng, Shitao; Zhou, Ran; Qin, Xuebo; Shi, Honghua; Ding, Dewen

2013-07-10

283

Separation of aromatic carboxylic acids using quaternary ammonium salts on reversed-phase HPLC. 1. Separation behavior of aromatic carboxylic acids  

SciTech Connect

In order to develop separation processes and analytical methods for aromatic carboxylic acids for the coal oxidation products, the separation behavior of aromatic carboxylic acids on a reversed-phase HPLC using eluent containing quaternary ammonium salt has been investigated. The retention mechanism of aromatic carboxylic acids was discussed on the basis of both ion-pair partition model and ion-exchange model. The retention behavior of aromatic carboxylic acids possessing one (or two) carboxylic acid group(s) followed the ion-pair partition model, where linear free energy relationship was observed between the capacity factor and the extraction equilibrium constants of benzoic acid and naphthalene carboxylic acid. Besides, the retention behavior followed ion-exchange model with increasing the number of carboxylic acids, where the capacity factor of benzene polycarboxylic acids is proportional to the association constants between aromatic acids and quaternary ammonium ions calculated on the basis of an electrostatic interaction model.

Kawamura, K.; Okuwaki, A.; Verheyen, T.; Perry, G.J. [Tohoku University, Miyagi (Japan). Graduate School of Environmental Studies

2006-02-15

284

Functional roles for the GerE-family carboxyl-terminal domains of nitrate response regulators NarL and NarP of Escherichia coli K-12  

PubMed Central

NarL and NarP are paralogous response regulators that control anaerobic gene expression in response to the favoured electron acceptors nitrate and nitrite. Their DNA-binding carboxyl termini are in the widespread GerE–LuxR–FixJ subfamily of tetrahelical helix–turn–helix domains. Previous biochemical and crystallographic studies with NarL suggest that dimerization and DNA binding by the carboxyl-terminal domain (CTD) is inhibited by the unphosphorylated amino-terminal receiver domain. We report here that NarL-CTD and NarP-CTD, liberated from their receiver domains, activated transcription in vivo from the class II napF and yeaR operon control regions, but failed to activate from the class I narG and fdnG operon control regions. Alanine substitutions were made to examine requirements for residues in the NarL DNA recognition helix. Substitutions for Val-189 and Arg-192 blocked DNA binding as assayed both in vivo and in vitro, whereas substitution for Arg-188 had a strong effect only in vivo. Similar results were obtained with the corresponding residues in NarP. Finally, Ala substitutions identified residues within the NarL CTD as important for transcription activation. Overall, results are congruent with those obtained for other GerE-family members, including GerE, TraR, LuxR and FixJ.

Lin, Alice V.; Stewart, Valley

2010-01-01

285

Prediction of functional sites in proteins using conserved functional group analysis.  

PubMed

A detailed knowledge of a protein's functional site is an absolute prerequisite for understanding its mode of action at the molecular level. However, the rapid pace at which sequence and structural information is being accumulated for proteins greatly exceeds our ability to determine their biochemical roles experimentally. As a result, computational methods are required which allow for the efficient processing of the evolutionary information contained in this wealth of data, in particular that related to the nature and location of functionally important sites and residues. The method presented here, referred to as conserved functional group (CFG) analysis, relies on a simplified representation of the chemical groups found in amino acid side-chains to identify functional sites from a single protein structure and a number of its sequence homologues. We show that CFG analysis can fully or partially predict the location of functional sites in approximately 96% of the 470 cases tested and that, unlike other methods available, it is able to tolerate wide variations in sequence identity. In addition, we discuss its potential in a structural genomics context, where automation, scalability and efficiency are critical, and an increasing number of protein structures are determined with no prior knowledge of function. This is exemplified by our analysis of the hypothetical protein Ydde_Ecoli, whose structure was recently solved by members of the North East Structural Genomics consortium. Although the proposed active site for this protein needs to be validated experimentally, this example illustrates the scope of CFG analysis as a general tool for the identification of residues likely to play an important role in a protein's biochemical function. Thus, our method offers a convenient solution to rapidly and automatically process the vast amounts of data that are beginning to emerge from structural genomics projects. PMID:15033369

Innis, C Axel; Anand, A Prem; Sowdhamini, R

2004-04-01

286

Dominant Functional Group Effects on the Invasion Resistance at Different Resource Levels  

PubMed Central

Background Functional group composition may affect invasion in two ways the effect of abundance, i.e. dominance of functional group; and the effect of traits, i.e. identity of functional groups. However, few studies have focused on the role of abundance of functional group on invasion resistance. Moreover, how resource availability influences the role of the dominant functional group in invasion resistance is even less understood. Methodology/Principal Findings In this experiment, we established experimental pots using four different functional groups (annual grass, perennial grass, deciduous shrub or arbor and evergreen shrub or arbor), and the dominant functional group was manipulated. These experimental pots were respectively constructed at different soil nitrogen levels (control and fertilized). After one year of growth, we added seeds of 20 different species (five species per functional group) to the experimental pots. Fertilization significantly increased the overall invasion success, while dominant functional group had little effect on overall invasion success. When invaders were grouped into functional groups, invaders generally had lower success in pots dominated by the same functional group in the control pots. However, individual invaders of the same functional group exhibited different invasion patterns. Fertilization generally increased success of invaders in pots dominated by the same than by another functional group. However, fertilization led to great differences for individual invaders. Conclusions/Significance The results showed that the dominant functional group, independent of functional group identity, had a significant effect on the composition of invaders. We suggest that the limiting similarity hypothesis may be applicable at the functional group level, and limiting similarity may have a limited role for individual invaders as shown by the inconsistent effects of dominant functional group and fertilization.

Wang, Jiang; Ge, Yuan; Zhang, Chong B.; Bai, Yi; Du, Zhao K.

2013-01-01

287

IRAG Working Group 3: Cell function-based assays  

Microsoft Academic Search

Cell function-based tests measure responses of cells at sublytic concentrations of test agents. The fluorescein leakage assay measures effects of substances on the barrier function of epithelial monolayers or multilayers (MDCK or NHEK cells) as in vitro models of corneal epithelial function. Two IRAG data submissions suggest that the fluorescein leakage assay shows promise as a screening test for surfactants

P. Botham; R. Osborne; K. Atkinson; G. Carr; M. Cottin; R. G. Van Buskirk

1997-01-01

288

A functional perspective on group memberships: DiVerential need fulWllment in a group typology  

Microsoft Academic Search

The social motivation functions of intimacy, task, and social category groups were investigated. In two studies, participants were asked to consider the extent to which their group memberships fulWlled several needs. A factor analysis conWrmed that the needs comprised three factors: aYliation, achievement, and identity. Intimacy groups were associated with aYliation needs, task groups were associated with achievement needs, and

Amy L. Johnson; Matthew T. Crawford; Steven J. Sherman; Abraham M. Rutchick; David L. Hamilton; Mario B. Ferreira; John V. Petrocelli

2006-01-01

289

Students' Perceptions of Classroom Group Work as a Function of Group Member Selection  

ERIC Educational Resources Information Center

|The purpose of this assessment was to examine whether differences exist between students who self-select their classroom work group members and students who are randomly assigned to their classroom work groups in terms of their use of organizational citizenship behaviors with their work group members; their commitment to, trust in, and relational…

Myers, Scott A.

2012-01-01

290

Students' Perceptions of Classroom Group Work as a Function of Group Member Selection  

ERIC Educational Resources Information Center

The purpose of this assessment was to examine whether differences exist between students who self-select their classroom work group members and students who are randomly assigned to their classroom work groups in terms of their use of organizational citizenship behaviors with their work group members; their commitment to, trust in, and relational…

Myers, Scott A.

2012-01-01

291

Attractiveness of group as function of self-esteem and acceptance by group  

Microsoft Academic Search

Persons made to feel well accepted in a group found the group more attractive than did those made to feel poorly accepted. But this difference was significantly greater among persons with low self-esteem  low self-esteem being taken as an indication of strong need for acceptance. Some support was given to the additional predictions that attractiveness of membership in a group

James E. Dittes

1959-01-01

292

The Bacteriorhodopsin Carboxyl-Terminus Contributes to Proton Recruitment and Protein Stability †  

Microsoft Academic Search

ABSTRACT: We examined functional and structural roles for the bacteriorhodopsin (bR) carboxyl-terminus. The extramembranous,and intracellular carboxyl-terminus was deleted by insertion of premature translation stop codons. Deletion of the carboxyl-terminus had no effect on purple membrane (PM) lattice dimensions, sheet size, or the electrogenic environment of the ground-state chromophore. Removal of the distal half of the carboxyl-terminus had no effect on

George J. Turner; Shirisha Chittiboyina; Lauren Pohren; Kirk G. Hines; John J. Correia; Drake C. Mitchell

2009-01-01

293

Zeta Functions, Renormalization Group Equations, and the Effective Action  

NASA Astrophysics Data System (ADS)

We demonstrate how to extract all the one-loop renormalization group equations for arbitrary quantum field theories from knowledge of an appropriate Seeley-DeWitt coefficient. By formally solving the renormalization group equations to one loop, we renormalization group improve the classical action and use this to derive the leading logarithms in the one-loop effective action for arbitrary quantum field theories.

Hochberg, David; Molina-París, Carmen; Pérez-Mercader, Juan; Visser, Matt

1998-11-01

294

The influence of oxygen-containing functional groups on the dispersion of single-walled carbon nanotubes in amide solvents  

NASA Astrophysics Data System (ADS)

Surface composition plays an important role in carbon nanotube dispersibility in different environments. Indeed, it determines the choice of dispersion medium. In this paper the effect of oxidation on the dispersion of HiPCO single-walled carbon nanotubes (SWNTs) in N-methyl-pyrrolidinone (NMP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMA), N-dodecyl-pyrrolidinone (N12P) and cyclohexyl-pyrrolidinone (CHP) was systematically studied. During the oxidation process, similar amounts of carboxylic acid and phenolic groups were introduced to mostly already existing defects. For each solvent the dispersion limits and the absorption coefficients were estimated by optical absorption analysis over a range of SWNT concentrations. The presence of acid oxygenated groups increased SWNT dispersibility in NMP, DMF and DMA, but decreased in N12P and CHP. The absorption coefficients, however, decreased for all solvents after oxidation, reflecting the weakening of the effective transition dipole of the ?-? transition with even limited extension functionalization and solvent interaction. The analysis of the results in terms of Hansen and Flory-Huggins solubility parameters evidenced the influence of dipolar interactions and hydrogen bonding on the dispersibility of oxidized SWNTs.

Brandão, S. D. F.; Andrada, D.; Mesquita, A. F.; Santos, A. P.; Gorgulho, H. F.; Paniago, R.; Pimenta, M. A.; Fantini, C.; Furtado, C. A.

2010-08-01

295

Biotinoyl domain of human acetylCoA carboxylase: Structural insights into the carboxyl transfer mechanism  

Microsoft Academic Search

Acetyl-CoA carboxylase (ACC) catalyzes the first step in fatty acid biosynthesis: the synthesis of malonyl-CoA from acetyl- CoA. As essential regulators of fatty acid biosynthesis and metabolism, ACCs are regarded as therapeutic targets for the treatment of metabolic diseases such as obesity. In ACC, the biotinoyl domain performs a critical function by transferring an activated carboxyl group from the biotin

Chung-Kyung Lee; Hae-Kap Cheong; Kyoung-Seok Ryu; Jae Il Lee; Weontae Lee; Young Ho Jeon; Chaejoon Cheong

2008-01-01

296

Hydrolysis of organonitrate functional groups in aerosol particles  

SciTech Connect

Organonitrate (ON) groups are important substituents in secondary organic aerosols. Model simulations and laboratory studies indicate a large fraction of ON groups in aerosol particles, but much lower quantities are observed in the atmosphere. Hydrolysis of ON groups in aerosol particles has been proposed recently. To test this hypothesis, we simulated formation of ON molecules in a reaction chamber under a wide range of relative humidity (0% to 90%). The mass fraction of ON groups (5% to 20% for high-NOx experiments) consistently decreased with increasing relative humidity, which was best explained by hydrolysis of ON groups at a rate of 4 day-1 (lifetime of 6 hours) for reactions under relative humidity greater than 20%. In addition, we found that secondary nitrogen-containing molecules absorb light, with greater absorption under dry and high-NOx conditions. This work provides the first evidence for particle-phase hydrolysis of ON groups, a process that could substantially reduce ON group concentration in the atmosphere.

Liu, Shang; Shilling, John E.; Song, Chen; Hiranuma, Naruki; Zaveri, Rahul A.; Russell, Lynn M.

2012-10-19

297

Special functions and group theory in theoretical physics  

SciTech Connect

The subject of special functions, even where restricted to the narrower subject of special functions in theoretical physics, is far too broad for one to attempt any meaningfully complete survey. We attempt to review the important main themes in the subject and then show how recent advances broadened and extended these themes.

Biedenharn, L.C.; Gustafson, R.A.; Lohe, M.A.; Louck, J.D.; Milne, S.C.

1983-01-01

298

Functional group diversity of bee pollinators increases crop yield  

Microsoft Academic Search

Niche complementarity is a commonly invoked mechanism underlying the positive relationship between biodiversity and ecosystem functioning, but little empirical evidence exists for complementarity among pollinator species. This study related differences in three functional traits of pollinating bees (flower height preference, daily time of flower visitation and within-flower behaviour) to the seed set of the obligate cross- pollinated pumpkin Cucurbita moschata

Patrick Hoehn; Teja Tscharntke; Jason M. Tylianakis; Ingolf Steffan-Dewenter

2008-01-01

299

Posttranslational modification of the Ha-ras oncogene protein: Evidence for a third class of protein carboxyl methyltransferases  

SciTech Connect

The ras oncogene products require membrane localization for their function, and this is thought to be accomplished by the addition of a palmitoyl group to a cysteine residue near the carboxyl terminus of the nascent chain. A lipidated carboxyl-terminal cysteine residue is also found in sequence-related yeast sex factors, and in at least two cases, the {alpha}-carboxyl group is also methyl esterified. To determine if ras proteins are themselves modified by a similar type of methylation reaction, the authors incubated rat embryo fibroblasts transformed with p53 and activated Ha-ras oncogenes with L-(methyl-{sup 3}H)methionine under conditions in which the isotope was converted to the methyl donor S-adenosyl-L-(methyl-{sup 3}H)methionine. By using an assay that detects methyl ester linkages, they found that immunoprecipitated ras proteins are in fact esterified and that the stability of these esters is consistent with a carboxyl-terminal localization. This methylation reaction may be important in regulating the interaction of ras proteins with plasma membrane components. The presence of analogous carboxyl-terminal tetrapeptide sequences in other proteins may provide a general recognition sequence for lipidation and methylation modification reactions.

Clarke, S.; Vogel, J.P.; Deschenes, R.J.; Stock, J. (Princeton Univ., NJ (USA))

1988-07-01

300

Ethyl anthracene-9-carboxyl-ate  

PubMed Central

In the title compound, C17H14O2, the COO group and the anthracene fragment form a dihedral angle of 76.00?(19)°. The torsion angle around the O—Csp 3 bond of the ester group is 108.52?(18)°. The crystal structure is stabilized by C—H?O inter­actions and edge-to-face arene inter­actions with C—H?(ring centroid) distances in the range 2.75–2.84?Å.

Weber, Edwin; Seichter, Wilhelm; Fischer, Conrad; Bendrath, L. M. S. Franziska; Ibragimov, Bakhtiyar T.

2008-01-01

301

Identification and Functional Characterization of Polycomb Group Complexes in Drosophila  

Microsoft Academic Search

Polycomb group (PcG) and trithorax group (trxG) proteins were first discovered\\u000ain Drosophila as repressors and activators of homeotic (HOX) genes, a set of\\u000atranscription factors that specify cell identity along the anteroposterior axis of segmented\\u000aanimals. Subsequent work has shown that PcG and trxG proteins form multimeric\\u000acomplexes that are not required to initiate the regulation of HOX genes,

A. Lagarou

2009-01-01

302

Nonequilibrium functional renormalization group for interacting quantum systems.  

PubMed

We propose a nonequilibrium version of functional renormalization within the Keldysh formalism by introducing a complex-valued flow parameter in the Fermi or Bose functions of each reservoir. Our cutoff scheme provides a unified approach to equilibrium and nonequilibrium situations. We apply it to nonequilibrium transport through an interacting quantum wire coupled to two reservoirs and show that the nonequilibrium occupation induces new power law exponents for the conductance. PMID:17995151

Jakobs, Severin G; Meden, Volker; Schoeller, Herbert

2007-10-11

303

Ethyl anthracene-9-carboxyl-ate.  

PubMed

In the title compound, C(17)H(14)O(2), the COO group and the anthracene fragment form a dihedral angle of 76.00?(19)°. The torsion angle around the O-Csp(3) bond of the ester group is 108.52?(18)°. The crystal structure is stabilized by C-H?O inter-actions and edge-to-face arene inter-actions with C-H?(ring centroid) distances in the range 2.75-2.84?Å. PMID:21202919

Weber, Edwin; Seichter, Wilhelm; Fischer, Conrad; Bendrath, L M S Franziska; Ibragimov, Bakhtiyar T

2008-06-19

304

The Nonenzymatic Reactivity of the Acyl-Linked Metabolites of Mefenamic Acid toward Amino and Thiol Functional Group Bionucleophiles.  

PubMed

Mefenamic acid (MFA), a carboxylic acid-containing nonsteroidal anti-inflammatory drug, is metabolized into the chemically-reactive MFA-1-O-acyl-glucuronide (MFA-1-O-G), MFA-acyl-adenylate (MFA-AMP), and the MFA-S-acyl-coenzyme A (MFA-CoA), all of which are electrophilic and capable of acylating nucleophilic sites on biomolecules. In this study, we investigate the nonenzymatic ability of each MFA acyl-linked metabolite to transacylate amino and thiol functional groups on the acceptor biomolecules Gly, Tau, l-glutathione (GSH), and N-acetylcysteine (NAC). In vitro incubations with each of the MFA acyl-linked metabolites (1 ?M) in buffer under physiologic conditions with Gly, Tau, GSH, or NAC (10 mM) revealed that MFA-CoA was 11.5- and 19.5-fold more reactive than MFA-AMP toward the acylation of cysteine-sulfhydryl groups of GSH and NAC, respectively. However, MFA-AMP was more reactive toward both Gly and Tau, 17.5-fold more reactive toward the N-acyl-amidation of taurine than its corresponding CoA thioester, while MFA-CoA displayed little reactivity toward glycine. Additionally, mefenamic acid-S-acyl-glutathione (MFA-GSH) was 5.6- and 108-fold more reactive toward NAC than MFA-CoA and MFA-AMP, respectively. In comparison with MFA-AMP and MFA-CoA, MFA-1-O-G was not significantly reactive toward all four bionucleophiles. MFA-AMP, MFA-CoA, MFA-1-O-G, MFA-GSH, and mefenamic acid-taurine were also detected in rat in vitro hepatocyte MFA (100 ?M) incubations, while mefenamic acid-glycine was not. These results demonstrate that MFA-AMP selectively reacts with the amino functional groups of glycine and lysine nonenzymatically, MFA-CoA selectively reacts nonenzymatically with the thiol functional groups of GSH and NAC, and MFA-GSH reacts with the thiol functional group of GSH nonenzymatically, all of which may potentially elicit an idiosyncratic toxicity in vivo. PMID:23975029

Horng, Howard; Benet, Leslie Z

2013-08-23

305

The relation between Escherichia coli surface functional groups' composition and their physicochemical properties  

PubMed Central

Escherichia coli surface characteristics including hydrophobicity, electrophoretic mobility and surface functional groups’ composition were investigated. These characteristics were determined respectively by water contact angle measurements, microelectrophoresis and x-ray photoelectron spectroscopy (XPS). The relation between the physicochemical properties and functional groups’ composition was also examined. The electrophoretic mobility at pH 7 appeared to be governed on the cell surface by the (O=C) functional groups. The cell surface’s hydrophilicity was associated with high levels of (C-(O.N)) and (OH- (C-O-C)) functional groups, whereas the cell surface’s hydrophobicity was associated with (C-(C,H)) functional groups.

Hamadi, Fatima; Latrache, Hassan; Zahir, Hafida; Elghmari, Abderrahmene; Timinouni, Mohamed; Ellouali, Mostapha

2008-01-01

306

Multicultural-Multilingual Group Sessions: Development of Functional Communication  

ERIC Educational Resources Information Center

Group therapy with multilingual, multicultural populations is a challenging and unexplored area that is beginning to be addressed because of the growing population of multilingual, multicultural children. In this article, the importance of working with children from different cultural backgrounds, and current research on bilingualism are reviewed.…

Larroude, Bettina

2004-01-01

307

Application of a multiple endpoint bacterial reporter assay to evaluate toxicological relevant endpoints of perfluorinated compounds with different functional groups and varying chain length.  

PubMed

Perfluorinated compounds are widely distributed in the environment; good knowledge about the toxic mode of action of these compounds can contribute to improved molecular design and risk assessment. The studied compounds were evaluated with a bacterial multiple endpoint reporter assay for responses in four different mode of action classes (oxidative damage, DNA damage, general cell lesions and membrane damage). The results of our study clearly demonstrate that inductions of stress responsive genes occur for the different compounds and confirm some of the known mechanisms of work for well studied compounds like PFOA and PFOS, and in addition provide new information for less studied compounds. Few inductions were observed after exposure to the low carbon number carboxylic acids, PFBtA (CF(3)(CF(2))(2)C(O)O(-)), PFPtA (CF(3)(CF(2))(3)C(O)O(-)), PFHxA (CF(3)(CF(2))(4)C(O)O(-)) and PFHpA (CF(3)(CF(2))(5)C(O)O(-)) at equimolar concentrations (0.0156-1 mM). The induction of membrane damage markers (MicF and OsmY) is prominently present after exposure to PFOS (CF(3)(CF(2))(7)SO(3)(-)) and even more after exposure to PFNA (CF(3)(CF(2))(7)C(O)O(-)). This is the first report describing the mode of action of carboxylic acids with 11 and 12 carbon atoms; they are equally potent inducers relative to PFOS and PFNA. Overall, the effects seen at the level of gene expression were higher for the sulfonic acids than for the carboxylic acids, but the effect of the chain length is more important than the effect of the functional group. PMID:20619337

Nobels, Ingrid; Dardenne, Freddy; De Coen, Wim; Blust, Ronny

2010-07-07

308

STUDY OF THE NEAR INFRARED-MEDIATED HEATING OF DISPERSIONS OF PROTEIN-COATED PRISTINE AND CARBOXYLATED SINGLE-WALLED CARBON NANOTUBES.  

PubMed

Previously, we demonstrated the selective NIR-mediated ablation of tumor cells in vitro using pristine single-walled carbon nanotubes (SWNTs) with adsorbed tumor-targeting ligands and carboxylated SWNTs with covalently-attached ligands. The covalent approach is advantageous in ensuring that protein ligands remain associated with the NIR-absorbing SWNTs in biological matrices and the noncovalent approach has the advantage of enabling SWNT functionalization without perturbation of the SWNT lattice and photothermal properties. Herein, we compare the ability of moderately-carboxylated (~4 at.% carboxylic acid groups) and pristine SWNT materials to absorb 808 nm radiation and convert it to heat. Under conditions of a constant 808 nm laser power density, the approach involved measuring the temperature of aqueous dispersions of protein-coated SWNTs as a function of the irradiation time. Nearly identical temperature profiles were observed for dispersions of moderately-carboxylated and pristine SWNTs possessing matched 808 nm optical densities and equivalent concentrations of carbonaceous species (i.e., SWNTs and amorphous carbon impurities). The results indicate that the amount of carbonaceous species in purified dispersions of protein-coated SWNTs is more important for converting absorbed 808 nm radiation into heat than whether or not the SWNTs were moderately carboxylated, and that moderately-carboxylated SWNTs could be the SWNT-material of choice for the targeted photothermal ablation of tumor cells. PMID:23645950

Sheardy, Alex T; Taylor, Jeremy J; Chilek, Jennifer L; Li, Synyoung; Wang, Ruhung; Draper, Rockford K; Pantano, Paul

2012-10-01

309

STUDY OF THE NEAR INFRARED-MEDIATED HEATING OF DISPERSIONS OF PROTEIN-COATED PRISTINE AND CARBOXYLATED SINGLE-WALLED CARBON NANOTUBES  

PubMed Central

Previously, we demonstrated the selective NIR-mediated ablation of tumor cells in vitro using pristine single-walled carbon nanotubes (SWNTs) with adsorbed tumor-targeting ligands and carboxylated SWNTs with covalently-attached ligands. The covalent approach is advantageous in ensuring that protein ligands remain associated with the NIR-absorbing SWNTs in biological matrices and the noncovalent approach has the advantage of enabling SWNT functionalization without perturbation of the SWNT lattice and photothermal properties. Herein, we compare the ability of moderately-carboxylated (~4 at.% carboxylic acid groups) and pristine SWNT materials to absorb 808 nm radiation and convert it to heat. Under conditions of a constant 808 nm laser power density, the approach involved measuring the temperature of aqueous dispersions of protein-coated SWNTs as a function of the irradiation time. Nearly identical temperature profiles were observed for dispersions of moderately-carboxylated and pristine SWNTs possessing matched 808 nm optical densities and equivalent concentrations of carbonaceous species (i.e., SWNTs and amorphous carbon impurities). The results indicate that the amount of carbonaceous species in purified dispersions of protein-coated SWNTs is more important for converting absorbed 808 nm radiation into heat than whether or not the SWNTs were moderately carboxylated, and that moderately-carboxylated SWNTs could be the SWNT-material of choice for the targeted photothermal ablation of tumor cells.

Sheardy, Alex T.; Taylor, Jeremy J.; Chilek, Jennifer L.; Li, Synyoung; Wang, Ruhung; Draper, Rockford K.; Pantano, Paul

2013-01-01

310

Post-Functionalized Polymer Brushes for Bio-Separation: Tuning GFP Adsorption via Functional Group Display  

NASA Astrophysics Data System (ADS)

An inexpensive and robust biosensor platform that can be tuned to separate and/or detect complex mixtures of biomolecules while minimizing reagents would be of great use for military, homeland security, and medical diagnostic applications. Gradient surfaces of poly(2-hydroxyethyl methacrylate) (PHEMA) brushes have been previously shown to spatially localize biomolecule binding, while minimizing non-specific adsorption of the same biomolecule on other regions of the gradient specimen. In order to further improve the specificity and to provide latent functionality for detection of the binding events, post-polymerization modification of PHEMA with various functional groups has been investigated. Using standard succinimide-based coupling, hydroxyl pendants of PHEMA brushes were conjugated to oligo-peptides, alkanes and oligo(ethylene glycol) (OEG) through an alpha-terminus primary amine. Ellipsometry, contact angle, XPS and ER-FTIR spectroscopy indicated that coupling occurred with efficiencies ranging from 10-40%. Post-functionalization of PHEMA with OEG and hexadecane allows manipulation of the hydrophilicity of the surface and thus tuning of Green Fluorescent Protein (GFP) binding.

Diamanti, Steve; Arifuzzaman, Shafi; Genzer, Jan; Naik, Rajesh; Vaia, Richard

2007-03-01

311

Organized thiol functional groups in mesoporous core shell colloids  

NASA Astrophysics Data System (ADS)

The co-condensation in situ of tetraethoxysilane (TEOS) and mercaptopropyltrimethoxysilane (MPTMS) using cetyltrimethylammonium bromide (CTAB) as a template results in the synthesis of multilayered mesoporous structured SiO2 colloids with “onion-like” chemical environments. Thiol groups were anchored to an inner selected SiO2 porous layer in a bilayered core shell particle producing different chemical regions inside the colloidal layered structure. X-Ray Photoelectron Spectroscopy (XPS) shows a preferential anchoring of the -SH groups in the double layer shell system, while porosimetry and simple chemical modifications confirm that pores are accessible. We can envision the synthesis of interesting colloidal objects with defined chemical environments with highly controlled properties.

Marchena, Martín H.; Granada, Mara; Bordoni, Andrea V.; Joselevich, María; Troiani, Horacio; Williams, Federico J.; Wolosiuk, Alejandro

2012-03-01

312

Functional renormalization group approach to the four-body problem  

NASA Astrophysics Data System (ADS)

We present a renormalization group analysis of the non-relativistic four-boson problem by means of a simple model with pointlike three- and four-body interactions. We investigate in particular the unitarity point where the scattering length is infinite and all energies are at the atom threshold. We find that the four-body problem behaves truly universally, independent of any four-body parameter confirming the findings of Platter et al. and von Stecher et al. [1-3].

Schmidt, R.; Moroz, S.

2010-04-01

313

Functional groups based on leaf physiology: are they spatially and temporally robust?  

Microsoft Academic Search

The functional grouping concept, which suggests that complexity in ecosystem function can be simplified by grouping species\\u000a with similar responses, was tested in the Florida scrub habitat. Functional groups were identified based on how species regulate\\u000a exchange of carbon and water with the atmosphere as indicated by both instantaneous gas exchange measurements and integrated\\u000a measures of function (%N, ?13C, ?15N,

Tammy E. Foster; J. Renée Brooks

2005-01-01

314

Development and function of group 2 innate lymphoid cells  

PubMed Central

The innate lymphoid cell (ILC) family has recently expanded with the discovery of type-2 innate lymphoid cells (ILC2). These cells arise from lymphoid progenitors in the bone marrow and, under the control of the transcriptional regulators ROR? and Gata3, they mature to give rise to IL-5, IL-9 and IL-13 producing ILC2. These cells are critical components of the innate immune response to parasitic worm infections and have also been implicated in the pathogenesis of asthma and allergy. Recent advances in our understanding of the molecular regulation of ILC2 development and function now present the opportunity to develop new genetic models to assess ILC2 immune function and to investigate possible therapeutic interventions.

Walker, Jennifer A; McKenzie, Andrew NJ

2013-01-01

315

Ethylene thiourea: thyroid function in two groups of exposed workers.  

PubMed Central

Ethylene thiourea is manufactured at one factory in the United Kingdom and is mixed into masterbatch rubber at another. Clinical examinations and thyroid function tests were carried out over a period of three years on eight process workers and five mixers and on matched controls. The results show that the exposed mixers, but not exposed process workers, have significantly lower levels of total thyroxine (T4) than the controls. One mixer had an appreciably raised level of thyroid stimulation hormone (TSH).

Smith, D M

1984-01-01

316

Polymerization of 1,3Dienes with Functional Groups. 4  

Microsoft Academic Search

Anionic polymerization of N,N-diethyl-2-methylene-3-butenamide (DEA), which is a 1,3-butadiene derivative containing a diethylamide function, was carried out in tetrahydrofurane (THF) under various conditions. When DEA was polymerized in THF at -78°C using potassium naphthalenide (K-Naph) or diphenylmethylpotassium (DPMK) as an initiator, a polymer of predictable molecular weight with a narrow molecular weight distribution was obtained. However, the rate of polymerization

Katsuhiko Takenaka; Natsuyo Shibata; Shinsuke Tsuchida; Hiroki Takeshita; Masamitsu Miya; Tomoo Shiomi

2008-01-01

317

Carboxylation of alkynylsilanes with carbon dioxide mediated by cesium fluoride in DMSO.  

PubMed

The facile syntheses of a variety functionalized propiolic acids were achieved by carboxylation of alkynylsilanes with carbon dioxide mediated by cesium fluoride under ambient conditions. PMID:23674078

Yonemoto-Kobayashi, Misato; Inamoto, Kiyofumi; Tanaka, Yoshiyuki; Kondo, Yoshinori

2013-06-21

318

Replacement of the Y450 (c234) phenyl ring in the carboxyl-terminal region of coagulation factor IX causes pleiotropic effects on secretion and enzyme activity.  

PubMed

The interplay between impaired protein biosynthesis and/or function caused by missense mutations, particularly in relation to specific protein regions, has been poorly investigated. As model we chose the severe p.Y450C mutation in the carboxyl-terminal region of coagulation factor IX (FIX) and, by expression of a panel of recombinant variants, demonstrated the key role of the tyrosine phenyl group for both FIX secretion and coagulant activity. Comparison among highly homologous coagulation serine proteases indicate that additive or compensatory pleiotropic effects on secretion and function by carboxyl-terminal mutations produce life-threatening or mild phenotypes in the presence of similarly reduced protein amounts. PMID:23994528

Branchini, Alessio; Campioni, Matteo; Mazzucconi, Maria Gabriella; Biondo, Francesca; Mari, Rosella; Bicocchi, Maria Patrizia; Bernardi, Francesco; Pinotti, Mirko

2013-08-27

319

Replacement of the Y450 (c234) phenyl ring in the carboxyl-terminal region of coagulation factor IX causes pleiotropic effects on secretion and enzyme activity  

PubMed Central

The interplay between impaired protein biosynthesis and/or function caused by missense mutations, particularly in relation to specific protein regions, has been poorly investigated. As model we chose the severe p.Y450C mutation in the carboxyl-terminal region of coagulation factor IX (FIX) and, by expression of a panel of recombinant variants, demonstrated the key role of the tyrosine phenyl group for both FIX secretion and coagulant activity. Comparison among highly homologous coagulation serine proteases indicate that additive or compensatory pleiotropic effects on secretion and function by carboxyl-terminal mutations produce life-threatening or mild phenotypes in the presence of similarly reduced protein amounts.

Branchini, Alessio; Campioni, Matteo; Mazzucconi, Maria Gabriella; Biondo, Francesca; Mari, Rosella; Bicocchi, Maria Patrizia; Bernardi, Francesco; Pinotti, Mirko

2013-01-01

320

A Generalized Logistic Regression Procedure to Detect Differential Item Functioning among Multiple Groups  

ERIC Educational Resources Information Center

|We present an extension of the logistic regression procedure to identify dichotomous differential item functioning (DIF) in the presence of more than two groups of respondents. Starting from the usual framework of a single focal group, we propose a general approach to estimate the item response functions in each group and to test for the presence…

Magis, David; Raiche, Gilles; Beland, Sebastien; Gerard, Paul

2011-01-01

321

A Generalized Logistic Regression Procedure to Detect Differential Item Functioning Among Multiple Groups  

Microsoft Academic Search

We present an extension of the logistic regression procedure to identify dichotomous differential item functioning (DIF) in the presence of more than two groups of respondents. Starting from the usual framework of a single focal group, we propose a general approach to estimate the item response functions in each group and to test for the presence of uniform DIF, nonuniform

David Magis; Gilles Raîche; Sébastien Béland; Paul Gérard

2011-01-01

322

A social capital explanation of the relationship between functional diversity and group performance  

Microsoft Academic Search

Purpose – Functional diversity research has resulted in equivocal findings for group performance suggesting the need for theoretical clarification. A review of previous functional diversity research indicates that high quality productive relationships are a key determinant in the performance of cognitively diverse groups. A theoretical framework is provided that demonstrates that assets embedded in the social structure of group member

W. Randy Evans; Charles M. Carson

2005-01-01

323

An experimental test of the effect of plant functional group diversity on arthropod diversity  

Microsoft Academic Search

Characteristics used to categorize plant species into functional groups for their effects on ecosystem functioning may also be relevant to higher trophic levels. In addition, plant and consumer diversity should be positively related because more diverse plant communities offer a greater variety of resources for the consumers. Thus, the functional group composition and richness of a plant community may affect

Amy J. Symstad; Evan Siemann; John Haarstad

2000-01-01

324

Detecting and quantifying oxygen functional groups on graphite nanofibers by fluorescence labeling of surface species  

Microsoft Academic Search

The ability to quantify functional groups on graphitic carbon nanofiber (GCNF) surfaces and to covalently attach ligands chemoselectively will aid in the development of functionalized GCNFs and potentially other carbon nanomaterials for applications in nanotechnology. Herein, we report the identification and quantification of functional groups on the surface of GCNFs using fluorescence labeling of surface species (FLOSS). Using reactions that

Timothy Pellenbarg; Nikolay Dementev; Riffard Jean-Gilles; Carol Bessel; Eric Borguet; Norman Dollahon; Robert Giuliano

2010-01-01

325

Cloning and Functional Characterization of Novel Variants and Tissue-Specific Expression of Alternative Amino and Carboxyl Termini of Products of Slc4a10  

PubMed Central

Previous studies have shown that the electroneutral Na+/HCO3? cotransporter NBCn2 (SLC4A10) is predominantly expressed in the central nervous system (CNS). The physiological and pathological significances of NBCn2 have been well recognized. However, little is known about the tissue specificity of expression of different NBCn2 variants. Moreover, little is known about the expression of NBCn2 proteins in systems other than CNS. Here, we identified a set of novel Slc4a10 variants differing from the originally described ones by containing a distinct 5? untranslated region encoding a new extreme amino-terminus (Nt). Electrophysiology measurements showed that both NBCn2 variants with alternative Nt contain typical electroneutral Na+-coupled HCO3? transport activity in Xenopus oocytes. Luciferase reporter assay showed that Slc4a10 contains two alternative promoters responsible for expression of the two types of NBCn2 with distinct extreme Nt. Western blotting showed that NBCn2 proteins with the original Nt are primarily expressed in CNS, whereas those with the novel Nt are predominantly expressed in the kidney and to a lesser extent in the small intestine. Due to alternative splicing, the known NBCn2 variants contain two types of carboxyl-termini (CT) differing in the optional inclusion of a PDZ-binding motif. cDNA cloning showed that virtually all NBCn2 variants expressed in epithelial tissues contain, but the vast majority of those from the neural tissues lack the PDZ-binding motif. We conclude that alternative transcription and splicing of Slc4a10 products are regulated in a tissue-specific manner. Our findings provide critical insights that will greatly influence the study of the physiology of NBCn2.

Qin, Xue; Xie, Zhang-Dong; Wang, Qing K.; Liu, Mugen; Chen, Li-Ming

2013-01-01

326

Tandem decarboxylative hydroformylation-hydrogenation reaction of ?,?-unsaturated carboxylic acids toward aliphatic alcohols under mild conditions employing a supramolecular catalyst system.  

PubMed

A new atom economic catalytic method for a highly chemoselective reduction of ?,?-unsaturated carboxylic acids to the corresponding saturated alcohols under mild reaction conditions, compatible with a wide range reactive functional groups, is reported. The new methodology consists of a novel tandem decarboxylative hydroformylation/aldehyde reduction sequence employing a unique supramolecular catalyst system. PMID:24022335

Diab, Lisa; Gellrich, Urs; Breit, Bernhard

2013-09-26

327

Polymerization of 1,3-Dienes with Functional Groups. 4.  

NASA Astrophysics Data System (ADS)

Anionic polymerization of N,N-diethyl-2-methylene-3-butenamide (DEA), which is a 1,3-butadiene derivative containing a diethylamide function, was carried out in tetrahydrofurane (THF) under various conditions. When DEA was polymerized in THF at -78°C using potassium naphthalenide (K-Naph) or diphenylmethylpotassium (DPMK) as an initiator, a polymer of predictable molecular weight with a narrow molecular weight distribution was obtained. However, the rate of polymerization was extremely slow to reach 80% conversion after 720 h. When the polymerization temperature was raised to 20°C, a low molecular weight oligomer with a broad molecular weight distribution was obtained because of a chain transfer reaction. On the other hand, no such side reaction occurred even at 20°C, when polymerization was carried out in the presence of LiCl. Also, the chain transfer reaction did not occur in lithium naphthalenide (Li-Naph) initiated polymerization. The microstructure of the polymer prepared using a potassium counter cation was a 1 : 1 mixture of 1,4-E and 1,2- structures. In the case of Li-Naph or DPMK/LiCl systems, the microstructure was a complicated mixture of 1,4-E, 1,4-Z, and 1,2-structures.

Takenaka, Katsuhiko; Shibata, Natsuyo; Tsuchida, Shinsuke; Takeshita, Hiroki; Miya, Masamitsu; Shiomi, Tomoo

328

Oleic acid-based gemini surfactants with carboxylic acid headgroups.  

PubMed

Anionic gemini surfactants with carboxylic acid headgroups have been synthesized from oleic acid. The hydrocarbon chain is covalently bound to the terminal carbonyl group of oleic acid via an ester bond, and the carboxylic acid headgroups are introduced to the cis double bond of oleic acid via disuccinyl units. The surfactants exhibit pH-dependent protonation-deprotonation behavior in aqueous solutions. In alkaline solutions (pH 9 in the presence of 10 mmol dm(-3) NaCl as the background electrolyte), the surfactants can lower the surface tension as well as form molecular assemblies, even in the region of low surfactant concentrations. Under acidic (pH 3) or neutral (pH 6-7) conditions, the surfactants are intrinsically insoluble in aqueous media and form a monolayer at the air/water interface. In this study, we have investigated physicochemical properties such as the function of the hydrocarbon chain length by means of static surface tension, pyrene fluorescence, dynamic light scattering, surface pressure-area isotherms, and infrared external reflection measurements. PMID:21768742

Sakai, Kenichi; Umemoto, Naoki; Matsuda, Wataru; Takamatsu, Yuichiro; Matsumoto, Mutsuyoshi; Sakai, Hideki; Abe, Masahiko

2011-01-01

329

Financial Regulatory Coordination: The Role and Functioning of the President's Working Group.  

National Technical Information Service (NTIS)

As you requested, this report discusses the role and functioning of the President's Working Group on Financial Markets (Working Group). Following the highly publicized losses experienced by a large leveraged hedge fund in 1998 and the potential implicatio...

2000-01-01

330

Group structure and weighting function effects on neutron penetration through thick sodium-iron shields  

SciTech Connect

The effects of group structures and weighting functions on neutron penetration through a thick Na-Fe geometry are studied. The recommended broad-group (61-neutron/23-gamma-ray) and few-group (22-neutron/10-gamma-ray) structures are tailored to the sodium and iron resonances, windows, and capture gamma-ray spectra. The best weighting functions are shown to be fine-group fluxes selected from a few key locations in the geometry. These group structures and weighting functions, relative to existing group structures and conventional weighting functions, improve the accuracy of the computed 61-neutron-group Bonner ball responses by up to one hundred percent and of the computed 22-neutron-group results by up to six hundred percent.

Fu, C.Y.; Ingersoll, D.T.

1987-01-01

331

A CRM Domain Protein Functions Dually in Group I and Group II Intron Splicing in Land Plant Chloroplasts  

Microsoft Academic Search

The CRM domain is a recently recognized RNA binding domain found in three group II intron splicing factors in chloroplasts, in a bacterial protein that associates with ribosome precursors, and in a family of uncharacterized proteins in plants. To elucidate the functional repertoire of proteins with CRM domains, we studied CFM2 (for CRM Family Member 2), which harbors four CRM

Yukari Asakura; Alice Barkan

2007-01-01

332

Preconversion catalytic deoxygenation of phenolic functional groups. Quarterly technical progress report, January 1--March 30, 1996 and April 1--June 30, 1996  

SciTech Connect

Over the course of his studies on catalytic deoxygenation of phenolic residues in coal by carbon monoxide, the author performed preliminary investigations into the removal of other heteroatom groups. This report describes his attempted carbonylation of phenyl amido complexes. These studies resulted in the surprisingly facile formation of amidines. The amidine group is the nitrogen analog of carboxylic acids and esters. This functional group combines the properties of an azomethane-like C=N double bond with an amide-like C-N single bond. This group, like the related allyl (C-C-C), aza-allyl (C-N-C), and carboxylato (O-C-O) groups, form a number of transition metal derivatives, with both early and late transition metals. Various bonding modes of the amidino group have been reported. However, most isolated complexes have the amidino ligand as a chelating ligand or bridging two metals. This is due to the preference of amidines to bond via the nitrogen lone pairs, in contrast to the {eta}{sup 3} {pi} bonding observed in metal-allyl complexes.

Kubiak, C.P.

1997-05-01

333

Correlation of infrared spectra of zinc(II) carboxylates with their structures.  

PubMed

The correlation of the infrared spectra of zinc(II) carboxylates with their structures was investigated in the paper. The complexes with different modes of the carboxylate binding, from chelating, through bridging (syn-syn, syn-anti, monatomic), ionic to monodentate were used for the study, namely [Zn(C6H5CHCHCOO)2(H2O)2] (I) with chelating carboxylate group (C6H5CHCHCOO=cinnamate), [Zn2(C6H5COO)4(pap)2] (II) with syn-syn bridging carboxylate (C6H5COO=benzoate; pap=papaverine), [Zn(C6H5CHCHCOO)2(mpcm)]n (III) with syn-anti carboxylate bridge (mpcm=methyl-3-pyridylcarbamate), [Zn(C5H4NCOO)2(H2O)4] (IV) with ionic carboxylate group (C5H4NCOO=nicotinate), [Zn(C6H5COO)2(pcb)2]n (V) with monodentate carboxylate coordination (pcb=3-pyridylcarbinol) and [Zn3(C6H5COO)6(nia)2] (VI) with syn-syn and monatomic carboxylate bridges (nia=nicotinamide). First, the mode of the carboxylate binding was assigned from the infrared spectra using the magnitude of the separation between the carboxylate stretches, Deltaexp=nuas(COO-)-nus(COO-). Then the values Deltaexp were compared with those calculated from structural data of the carboxylate anion (Deltacalc). The conclusions about the carboxylate binding which resulted from the Delta values, were confronted with the crystal structure of the complexes. The limitations and recommendations were formulated to assign the mode of the carboxylate binding from the infrared spectra. The dependence of the Deltaexp values on the magnitudes of Zn-O-C angles in bidentate carboxylate coordination was observed. PMID:16829167

Zelenák, V; Vargová, Z; Györyová, K

2006-02-28

334

Relationship between surface coverage and end group functionality of molecularly thin perfluoropolyether films  

NASA Astrophysics Data System (ADS)

The relationship between surface coverage and film thickness for perfluoropolyether (PFPE) films with different functional end groups was investigated by measuring the dispersive surface energy. It was found that the strength of end group functionality played an important role in the surface coverage; i.e., PFPE with the stronger end group functionality has the smaller surface coverage. Molecular dynamics simulations with a bead-spring model were employed to investigate the conformation of PFPE films, where the anisotropic radii of gyration were analyzed as a function of the strength of end group functionality. It was found that PFPE became flatter if the strength of end group functionality decreased, which, in turn, increased the surface coverage.

Chen, Haigang; Jhon, Myung S.

2008-04-01

335

Prediction of phase equilibrium and hydration free energy of carboxylic acids by Monte Carlo simulations.  

PubMed

In this work, a new transferable united-atom force field has been developed to predict phase equilibrium and hydration free energy of carboxylic acids. To take advantage of the transferability of the AUA4 force field, all Lennard-Jones parameters of groups involved in the carboxylic acid chemical function are reused from previous parametrizations of this force field. Only a unique set of partial electrostatic charges is proposed to reproduce the experimental gas phase dipole moment, saturated liquid densities and vapor pressures. Phase equilibrium properties of various pure carboxylic acids (acetic acid, propanoic acid, butanoic acid, pentanoic acid, hexanoic acid) and one diacid (1,5-pentanedioic) are studied through Monte Carlo simulations in the Gibbs ensemble. A good accuracy is obtained for pure compound saturated liquid densities and vapor pressures (average deviation of 2% and 6%, respectively), as well as for critical points. The vaporization enthalpy is, however, poorly predicted for short acids, probably due to a limitation of the force field to correctly describe the significant dimerization in the vapor phase. Pressure-composition diagrams for two binary mixtures (acetic acid + n-butane and propanoic acid + pentanoic acid) are also computed with a good accuracy, showing the transferability of the proposed force field to mixtures. Hydration free energies are calculated for three carboxylic acids using thermodynamic integration. A systematic overestimation of around 10 kJ/mol is observed compared to experimental data. This new force field parametrized only on saturated equilibrium properties appears insufficient to reach an acceptable precision for this property, and only relative hydration free energies between two carboxylic acids can be correctly predicted. This highlights the limitation of the transferability feature of force fields to properties not included in the parametrization database. PMID:23697338

Ferrando, Nicolas; Gedik, Ibrahim; Lachet, Véronique; Pigeon, Laurent; Lugo, Rafael

2013-06-03

336

Modification of cardiac sodium channels by carboxyl reagents. Trimethyloxonium and water-soluble carbodiimide  

Microsoft Academic Search

In TFX-sensitive nerve and skeletal muscle Na + channels, selective modification of external carboxyl groups with trimethyloxonium (TMO) or water- soluble carbodiimide (WSC) prevents voltage-dependent Ca z+ block, reduces uni- tary conductance, and decreases guanidinium toxin affinity. In the case of TMO, it has been suggested that all three effects result from modification of a single carboxyl group, which causes

SAMUEL C. DUDLEY; CLIVE M. BAUMGARTEN

1993-01-01

337

Functional Group Density as an index for assessing habitat quality in tallgrass prairie  

Microsoft Academic Search

We propose that patterns of plant functional group occurrences could be a reliable indicator of prairie vegetation quality. A method for assessing tallgrass prairie quality based on density and composition of plant functional groups was developed and tested by comparison with qualitative indices calculated from species data at 17 prairies in Illinois. Species sample data were recorded from quadrats while

Valerie A. Sivicek; John B. Taft

2011-01-01

338

Development of acid functional groups during the thermal degradation of wood and wood components  

Technology Transfer Automated Retrieval System (TEKTRAN)

This study provides data on acid functional groups in charcoals and how the acid functional group content varies with the formation conditions. Chars were created from purified cellulose, purified lignin, pine wood, and pine bark. The charring temperatures and charring duration were controlled in a ...

339

Calcium carbonate crystallization controlled by functional groups: A mini-review  

NASA Astrophysics Data System (ADS)

Various functional groups have been suggested to play essential roles on biomineralization of calcium carbonate (CaCO3) in natural system. 2D and 3D models of regularly arranged functional groups have been established to investigate their effect on CaCO3 crystallization. This mini-review summarizes the recent progress and the future development is prospected.

Deng, Hua; Shen, Xing-Can; Wang, Xiu-Mei; Du, Chang

2013-03-01

340

Psychosocial functioning in patients with treatment-resistant depression after group cognitive behavioral therapy  

Microsoft Academic Search

BACKGROUND: Although patients with Treatment Resistant Depression (TRD) often have impaired social functioning, few studies have investigated the effectiveness of psychosocial treatment for these patients. We examined whether adding group cognitive behavioral therapy (group-CBT) to medication would improve both the depressive symptoms and the social functioning of patient with mild TRD, and whether any improvements would be maintained over one

Miki Matsunaga; Yasumasa Okamoto; Shin-ichi Suzuki; Akiko Kinoshita; Shinpei Yoshimura; Atsuo Yoshino; Yoshihiko Kunisato; Shigeto Yamawaki

2010-01-01

341

The Selberg Zeta Function for Convex Co-Compact Schottky Groups  

Microsoft Academic Search

We give a new upper bound on the Selberg zeta function for a convex co-compact Schottky group acting on the hyperbolic space H n +1: in strips parallel to the imaginary axis the zeta function is bounded by exp ( C| s| d) where d is the dimension of the limit set of the group. This bound is more precise

Laurent Guillopé; Kevin K. Lin; Maciej Zworski

2004-01-01

342

CO: A chemical ontology for identification of functional groups and semantic comparison of small molecules  

Microsoft Academic Search

A novel chemical ontology based on chemical functional groups automatically, objectively assigned by a computer program, was developed to categorize small molecules. It has been applied to PubChem and the small molecule interaction database to demonstrate its utility as a basic pharmacophore search system. Molecules can be compared using a semantic similarity score based on functional group assignments rather than

Howard J. Feldman; Michel Dumontier; Susan Ling; Norbert Haider; Christopher W. V. Hogue

2005-01-01

343

Unitary reflection groups associated with singularities of functions with cyclic symmetry  

NASA Astrophysics Data System (ADS)

Finite groups generated by Euclidean reflections have been commonplace in various problems of singularity theory since their relationship with the classification of critical points of functions was discovered by Arnol'd [1], [2]. We show that a number of finite groups generated by unitary reflections are also naturally related to singularities of functions, namely, those invariant under a unitary reflection of finite order. To this end, we consider germs of functions on a manifold with boundary and lift them to a cyclic covering of the manifold, ramified over the boundary. This construction provides a new notion of roots for the groups under consideration and provides skew-Hermitian analogues of these groups.

Goryunov, V. V.

1999-10-01

344

Continuum limit in matrix models for quantum gravity from the functional renormalization group  

NASA Astrophysics Data System (ADS)

We consider the double-scaling limit in matrix models for two-dimensional quantum gravity, and establish the nonperturbative functional renormalization group as a novel technique to compute the corresponding interacting fixed point of the renormalization group flow. We explicitly evaluate critical exponents and compare them to the exact results. The functional renormalization group method allows a generalization to tensor models for higher-dimensional quantum gravity and to group field theories. As a simple example of how this method works for such models, we compute the leading-order beta function for a colored matrix model that is inspired by recent developments in tensor models.

Eichhorn, Astrid; Koslowski, Tim

2013-10-01

345

Perceptions of popularity among a group of high-functioning adults with autism.  

PubMed

The purpose of this study was to determine how a group of adults with autism perceived one another's interpersonal attributes and popularity. Five female and 11 male high-functioning autistic adults, 18-45 years old, participated in a social skills group together for several years. A sociogram and a questionnaire designed to determine perceptions of best looking, most athletic, and most humorous group members were administered to group members and nonhandicapped group leaders. Independent assessments of intelligence and empathy also were taken. Results indicated that perceived attractiveness and sense of humor were correlated with popularity, but group members' assessments of these attributes differed from those of the nonhandicapped group leaders. Differences between group members and group leaders responses and the implications of the results of the study for social skills training with high-functioning autistic adolescents and adults are discussed. PMID:2324054

Mesibov, G B; Stephens, J

1990-03-01

346

Biogeographical Boundaries, Functional Group Structure and Diversity of Rocky Shore Communities along the Argentinean Coast  

PubMed Central

We investigate the extent to which functional structure and spatial variability of intertidal communities coincide with major biogeographical boundaries, areas where extensive compositional changes in the biota are observed over a limited geographic extension. We then investigate whether spatial variation in the biomass of functional groups, over geographic (10?s km) and local (10?s m) scales, could be associated to species diversity within and among these groups. Functional community structure expressed as abundance (density, cover and biomass) and composition of major functional groups was quantified through field surveys at 20 rocky intertidal shores spanning six degrees of latitude along the southwest Atlantic coast of Argentina and extending across the boundaries between the Argentinean and Magellanic Provinces. Patterns of abundance of individual functional groups were not uniformly matched with biogeographical regions. Only ephemeral algae showed an abrupt geographical discontinuity coincident with changes in biogeographic boundaries, and this was limited to the mid intertidal zone. We identified 3–4 main ‘groups’ of sites in terms of the total and relative abundance of the major functional groups, but these did not coincide with biogeographical boundaries, nor did they follow latitudinal arrangement. Thus, processes that determine the functional structure of these intertidal communities are insensitive to biogeographical boundaries. Over both geographical and local spatial scales, and for most functional groups and tidal levels, increases in species richness within the functional group was significantly associated to increased total biomass and reduced spatial variability of the group. These results suggest that species belonging to the same functional group are sufficiently uncorrelated over space (i.e. metres and site-to-site ) to stabilize patterns of biomass variability and, in this manner, provide a buffer, or “insurance”, against spatial variability in environmental conditions.

Wieters, Evie A.; McQuaid, Christopher; Palomo, Gabriela; Pappalardo, Paula; Navarrete, Sergio A.

2012-01-01

347

Ethyl 3-amino-5-bromo-1-benzo-furan-2-carboxyl-ate.  

PubMed

The title compound, C11H10BrNO3, is close to planar with the benzo-furan unit and the ester group subtending a dihedral angle of 5.25?(2)°. The mol-ecular structure features an intra-molecular N-H?O inter-action. In the crystal, N-H?O hydrogen bonds involving carboxyl O-atom acceptors generate a chain extending along [201]. PMID:23723919

Yamuna, A J; Karunakar, P; Girija, C R; Vaidya, V P; Krishnamurthy, V

2013-04-20

348

Ethyl 3-amino-5-bromo-1-benzo-furan-2-carboxyl-ate  

PubMed Central

The title compound, C11H10BrNO3, is close to planar with the benzo­furan unit and the ester group subtending a dihedral angle of 5.25?(2)°. The mol­ecular structure features an intra­molecular N—H?O inter­action. In the crystal, N—H?O hydrogen bonds involving carboxyl O-atom acceptors generate a chain extending along [201].

Yamuna, A. J.; Karunakar, P.; Girija, C. R.; Vaidya, V. P.; Krishnamurthy, V.

2013-01-01

349

Functionalized alkenylzinc reagents bearing carbonyl groups: preparation by direct metal insertion and reaction with electrophiles.  

PubMed

Highly functionalized cyclic and acyclic alkenylzinc reagents bearing functional groups such as aldehyde, keto, and ester groups were readily prepared by either direct zinc insertion in the presence of LiCl or by magnesium insertion in the presence of LiCl and ZnCl2 . Subsequent functionalization reactions, such as Negishi cross-couplings, acylations, and allylations, furnished polyfunctional compounds in excellent yields. PMID:23666638

Sämann, Christoph; Schade, Matthias A; Yamada, Shigeyuki; Knochel, Paul

2013-05-10

350

Selective carboxyl methylation of structurally altered calmodulins in Xenopus oocytes  

SciTech Connect

The eucaryotic protein carboxyl methyltransferase specifically modifies atypical D-aspartyl and L-isoaspartyl residues which are generated spontaneously as proteins age. The selectivity of the enzyme for altered proteins in intact cells was explored by co-injecting Xenopus laevis oocytes with S-adenosyl-L-(methyl-3H)methionine and structurally altered calmodulins generated during a 14-day preincubation in vitro. Control experiments indicated that the oocyte protein carboxyl methyltransferase was not saturated with endogenous substrates, since protein carboxyl methylation rates could be stimulated up to 8-fold by increasing concentrations of injected calmodulin. The oocyte protein carboxyl methyltransferase showed strong selectivities for bovine brain and bacterially synthesized calmodulins which had been preincubated in the presence of 1 mM EDTA relative to calmodulins which had been preincubated with 1 mM CaCl2. Radioactive methyl groups were incorporated into base-stable linkages with recombinant calmodulin as well as into carboxyl methyl esters following its microinjection into oocytes. This base-stable radioactivity most likely represents the trimethylation of lysine 115, a highly conserved post-translational modification which is present in bovine and Xenopus but not in bacterially synthesized calmodulin. Endogenous oocyte calmodulin incorporates radioactivity into both carboxyl methyl esters and into base-stable linkages following microinjection of oocytes with S-adenosyl-(methyl-3H)methionine alone. The rate of oocyte calmodulin carboxyl methylation in injected oocytes is calculated to be similar to that of lysine 115 trimethylation, suggesting that the rate of calmodulin carboxyl methylation is similar to that of calmodulin synthesis. At steady state, oocyte calmodulin contains approximately 0.0002 esters/mol of protein, which turn over rapidly.

Desrosiers, R.R.; Romanik, E.A.; O'Connor, C.M. (Worcester Foundation for Experimental Biology, Shrewsbury, MA (USA))

1990-12-05

351

Investigation of the ionic strength dependence of Ulva lactuca acid functional group pK(a)s by manual alkalimetric titrations.  

PubMed

We performed a series of manual alkalimetric titrations in NaCl solutions (0.01-5.0 M) at T = 25 degrees C on both fresh and dehydrated samples of the marine chlorophyte Ulva lactuca (sea lettuce), a strong metal accumulator holding considerable promise in biosorbent and biomonitor applications. Functional groups were characterized in terms of their number, site densities, and acid dissociation constants (pK(a)s). FITEQL4.0 modeling shows that, at any ionic strength, titration curves for dehydrated biomass in the pH range 2-10 are adequately described by three functional groups with remarkably uniform site densities of about 5 x 10(-4) mol/g. Lower site densities for fresh U. lactuca are consistent with approximately 87% water content. The pK(a)s display pronounced ionic strength dependent behavior obeying an extended Debye-Huckel relation. Extrapolation to I = 0 yields values of 4.26 +/- 0.04, 6.44 +/- 0.02, and 9.56 +/- 0.04. This information by itself is insufficient to unambiguously identify the groups. Similar site densities suggest that all three are linked to major molecular building blocks of the cell material, pointing to carboxylic acids, phosphate esters, and amines as likely candidates. Highly acidic sulfate esters, not detected in our titrations, may also play a role in trace metal adsorption on U. lactuca. PMID:20121199

Schijf, Johan; Ebling, Alina M

2010-03-01

352

Social disinterest attitudes and group cognitive-behavioral social skills training for functional disability in schizophrenia.  

PubMed

The majority of clinical trials of cognitive-behavioral therapy (CBT) for schizophrenia have used individual therapy to target positive symptoms. Promising results have been found, however, for group CBT interventions and other treatment targets like psychosocial functioning. CBT for functioning in schizophrenia is based on a cognitive model of functional outcome in schizophrenia that incorporates dysfunctional attitudes (eg, social disinterest, defeatist performance beliefs) as mediators between neurocognitive impairment and functional outcome. In this report, 18 clinical trials of CBT for schizophrenia that included measures of psychosocial functioning were reviewed, and two-thirds showed improvements in functioning in CBT. The cognitive model of functional outcome was also tested by examining the relationship between social disinterest attitudes and functional outcome in 79 people with schizophrenia randomized to either group cognitive-behavioral social skills training or a goal-focused supportive contact intervention. Consistent with the cognitive model, lower social disinterest attitudes at baseline and greater reduction in social disinterest during group therapy predicted better functional outcome at end of treatment for both groups. However, the groups did not differ significantly with regard to overall change in social disinterest attitudes during treatment, suggesting that nonspecific social interactions during group therapy can lead to changes in social disinterest, regardless of whether these attitudes are directly targeted by cognitive therapy interventions. PMID:19628761

Granholm, Eric; Ben-Zeev, Dror; Link, Peter C

2009-07-23

353

[Influence of carboxylic carbon nanotube supported platinum catalyst on cathode oxygen reduction performance of MFC].  

PubMed

The cathodic catalyst plays an important role in the electricity generation of the microbial fuel cell (MFC). In order to evaluate the efficiency of oxygen reduction on the carbon nanotube (CNT) functionalized with different carboxylic groups supported Pt, carboxylic CNTs under the conditions of 80 degrees C and 95 degrees C were prepared, respectively. Pt/CNT catalysts (Pt/CNT-80 and Pt/CNT-95) was prepared by the dipping-precipitation method and their oxygen reduction efficiency was tested in the MFC (MFC-80, MFC-95 and MFC-C) with the air cathode. The results showed that the maximum power output densities of the MFC-95 and MFC-80 were 568.8 mWx m(-2) and 412.8 mWx m(-2), internal resistances were 204.7 omega and 207.7 omega, and open circuit potentials were 0.719 V and 0.651 V, respectively. However, the maximum power output density of the control MFC-C was only 5.4 mW x m(-2), and its internal resistance was 826.2 omega. XPS and XRD analysis results demonstrate that the efficiency of Pt/CNT-95 catalyst is better than Pt/CNT-80 may result from the surface of carboxylic CNT in the 95 degrees C introduced rich oxygen containing groups. PMID:23798151

Tu, Li-Xing; Zhu, Neng-Wu; Wu, Ping-Xiao; Li, Ping; Wu, Jin-Hua

2013-04-01

354

Executive functions in school?aged children: Potential efficacy of tasks in discriminating clinical groups  

Microsoft Academic Search

The performance of three groups of children on a battery of executive function tasks was investigated. A double dissociation paradigm was used, including six executive function tasks (Wisconsin Card Sorting Test, Matching Familiar Figures Test, visual search, verbal fluency, Tower of Hanoi, and mazes) and two vocabulary tasks (Peabody Picture Vocabulary Test?Revised and the Boston Naming Test). Executive function was

Lisa L. Weyandt; W. Grant Willis

1994-01-01

355

Succession of phytoplankton functional groups regulated by monsoonal hydrology in a large canyon-shaped reservoir.  

PubMed

Liuxihe reservoir is a deep, monomictic, oligo-mesotrophic canyon-reservoir in the subtropical monsoon climate region of southern China. Phytoplankton functional groups in the reservoir were investigated and a comparison made between the succession observed in 2008, an exceptionally wet year, and 2009, an average year. The reservoir shows strong annual fluctuations in water level caused by monsoon rains and artificial drawdown. Altogether 28 functional groups of phytoplankton were identified, including 79 genera. Twelve of the groups were analyzed in detail using redundancy analysis. Because of the oligo-mesotrophic and P-limited condition of the reservoir, the dominant functional groups were those tolerant of nutrient (phosphorus) deficiency. The predominant functional groups in the succession process were Groups A (Cyclotella with greatest axial linear dimension<10 ?m), B (Cyclotella with greatest axial linear dimension>10 ?m), LO (Peridinium), LM (Ceratium and Microcystis), E (Dinobryon and Mallomonas), F (Botryococcus), X1 (Ankistrodesmus, Ankyra, Chlorella and Monoraphidium) and X2 (Chlamydomonas and Chroomonas). The development of groups A, B and LO was remarkably seasonal. Group A was dominant during stratification, when characteristic small size and high surface/volume ratio morphology conferred an advantage. Group LO was dominant during dry stratification, when motility was advantageous. Group B plankton exhibited a high relative biomass during periods of reduced euphotic depth and isothermy. Groups LM, E, F, X1 and X2 occasionally exhibited high relative biomasses attributable to specific environmental events (e.g. drawdown, changes in zooplankton community). A greater diversity of phytoplankton functional groups was apparent during isothermy. This study underscores the usefulness of functional algal groups in studying succession in subtropical impoundments, in which phytoplankton succession can be significantly affected by external factors such as monsoonal hydrology and artificial drawdown, which alter variables such as retention time, mixing regime and thermal structure and influence light and nutrient availability. PMID:21831406

Xiao, Li-Juan; Wang, Tian; Hu, Ren; Han, Bo-Ping; Wang, Sheng; Qian, Xin; Padisák, Judit

2011-07-23

356

Carboxylic Acid Esters as Substrates of Cholinesterases  

NASA Astrophysics Data System (ADS)

Data on the kinetics of the hydrolysis of various carboxylic acid esters by two main types of cholinesterases — acetylcholinesterase from human erythrocytes and butyrylcholinesterase from horse blood serum — are surveyed. It is shown that the rate of enzyme hydrolysis depends significantly on the structure of the acyl part of the ester molecule, the nature of the ester heteroatom, the structure of the alcohol component, and particularly the structure of the onium group. Esters based on natural products are of special interest as specific substrates of these enzymes. The role of the productive and non-productive sorption of the substrates in enzyme catalysis is demonstrated. The bibliography includes 81 references.

Brestkin, A. P.; Rozengart, E. V.; Abduvakhabov, A. A.; Sadykov, A. A.

1983-10-01

357

Galloylglucoses of low molecular weight as mordant in electron microscopy. II. The moiety and functional groups possibly involved in the mordanting effect  

PubMed Central

Synthetic pentamonogalloylglucose applied to fixed tissues acts as a mordant, inducing high and diversified contrast similar to that obtained with natural gallotannins of low molecular weight (LMGG). By the separate use of each of the two moieties of the galloylglucose molecule, it was found that gallic acid is the mordanting agent. Glucose may contribute, however, to the effect by increasing the solubility and cross-linking potential of the compound, since the mordanting induced by gallic acid alone is weaker than that produced by its hexose esters. As suggested by results obtained with various phenolics and benzoic acid derivatives, the functional groups required for the mordanting effect of such agents are the carboxyl group, and at least one hydroxyl group concomitantly present on the benzene ring. In the case of galloylglucoses, it is assumed that the effect is due to hydrolysis products (gallic, digallic, or trigallic acids) or to the multiple hydroxyl groups of the intact molecule. Esters of gallic acid (propyl- and methylgallate), as well as pyrogallol, produce a "reversed staining" of all membranes, except for those of communicating (gap) junctions.

1976-01-01

358

Structural and biochemical study on the inhibitory activity of derivatives of 5-nitro-furan-2-carboxylic acid for RNase H function of HIV1 reverse transcriptase  

Microsoft Academic Search

Rapid emergence of drug-resistant variants is one of the most serious problems in chemotherapy for HIV-1 infectious diseases. Inhibitors acting on a target not addressed by approved drugs are of great importance to suppress drug-resistant viruses. HIV-1 reverse transcriptase has two enzymatic functions, DNA polymerase and RNase H activities. The RNase H activity is an attractive target for a new

Hiroshi Yanagita; Emiko Urano; Kishow Matsumoto; Reiko Ichikawa; Yoshihisa Takaesu; Masakazu Ogata; Tsutomu Murakami; Hongui Wu; Joe Chiba; Jun Komano; Tyuji Hoshino

2011-01-01

359

Compression in encapsulated carboxylic acid homodimers  

NASA Astrophysics Data System (ADS)

A density functional theory study has been carried out on five carboxylic acid homodimers, free and encapsulated, in order to study the effect of encapsulation or compression. Attractive interactions between the guests and the walls of the capsules stabilize encapsulation even in cases of severe confinement where formation of dimers is unfavorable. Larger hydrogen bonds are calculated for the encapsulated than the isolated dimers except for the case of the bulkiest dimer considered, where encapsulation leads to shortening of the hydrogen bond. Shorter hydrogen-bond lengths with increasing size of the encapsulated dimers are calculated, in agreement with experimental work.

Tzeli, Demeter; Petsalakis, Ioannis D.; Theodorakopoulos, Giannoula

2013-06-01

360

Unique determination of the effective potential in terms of renormalization group functions  

SciTech Connect

The perturbative effective potential V in the massless {lambda}{phi}{sup 4} model with a global O(N) symmetry is uniquely determined to all orders by the renormalization group functions alone when the Coleman-Weinberg renormalization condition (d{sup 4}V/d{phi}{sup 4})|{sub {phi}}{sub ={mu}}={lambda} is used, where {mu} represents the renormalization scale. Systematic methods are developed to express the n-loop effective potential in the Coleman-Weinberg scheme in terms of the known n-loop minimal-subtraction (MS) renormalization group functions. Moreover, it also proves possible to sum the leading- and subsequent-to-leading-logarithm contributions to V. An essential element of this analysis is a conversion of the renormalization group functions in the Coleman-Weinberg scheme to the renormalization group functions in the MS scheme. As an example, the explicit five-loop effective potential is obtained from the known five-loop MS renormalization group functions and we explicitly sum the leading-logarithm, next-to-leading-logarithm, and further subleading-logarithm contributions to V. Extensions of these results to massless scalar QED are also presented. Because massless scalar QED has two couplings, conversion of the renormalization group functions from the MS scheme to the Coleman-Weinberg scheme requires the use of multiscale renormalization group methods.

Chishtie, F. A.; Hanif, T.; McKeon, D. G. C. [Department of Applied Mathematics, University of Western Ontario, London, ON N6A 5B7 (Canada); Steele, T. G. [Department of Physics and Engineering Physics, University of Saskatchewan, Saskatoon, SK, S7N 5E2 (Canada)

2008-03-15

361

Tetra-methyl anthracene-2,3,6,7-tetra-carboxyl-ate-tetra-methyl 9,10-dihydro-9,10-dioxoanthracene-2,3,6,7-tetra-carboxyl-ate (1/1)1  

PubMed Central

In the title co-crystal, C22H16O10·C22H18O8, the independent tetra­methyl 9,10-dihydro-9,10-dioxoanthracene-2,3,6,7-tetra­carboxyl­ate, (I), and tetra­methyl anthracene-2,3,6,7-tetra­carboxyl­ate, (II), components occupy separate crystallographic inversion centers. In (II), the dihedral angles between the mean aromatic plane and the two independent carboxyl­ate planes are 41.32?(10) and ?38.35?(10)°. The methyl­carboxyl­ate groups of (I) are disordered, with each resolvable into two groups. In the least disordered carboxyl­ate, the apparent angles between the mean aromatic plane and the two partial carboxyl­ate planes [site occupations = 0.510?(3) and 0.490?(3)] are 16.8?(3) and 23.3?(3)°. In the highly disordered group, the apparent angles between the mean aromatic plane and the two partial carboxyl­ate planes [site occupations = 0.510?(3) and 0.490?(3)] are 78.3?(3) and ?74.1?(3)°. In addition, this extreme disorder leads to an artificially elongated C(aromatic)—C(carbox­yl) bond.

Drake, Brenton L.; Morris, J. Larry; McLaughlin, Mark L.; Fronczek, Frank R.; Watkins, Steven F.

2012-01-01

362

Butane-1,4-diyl bis-(pyridine-3-carboxyl-ate)  

PubMed Central

Mol­ecules of the title compound (alternative name: butane-1,4-diyl dinicotinate), C16H16N2O4, lie on a inversion centre, located at the mid-point of the central C—C bond of the aliphatic chain, giving one half-mol­ecule per asymmetric unit. The butane chain adopts an all-trans conformation. The dihedral angle between the mean plane of the butane-3-carboxyl­ate group [for the non-H atoms, maximum deviation = 0.0871?(15)?Å] and the pyridine ring is 10.83?(7)°. In the crystal, mol­ecules lie in planes parallel to (122). The structure features weak ?–? inter­actions with a centroid–centroid distance of 3.9281?(11)?Å.

Vallejos, Javier; Brito, Ivan; Cardenas, Alejandro; Bolte, Michael

2012-01-01

363

2-Amino-5-methyl-pyridinium 3-hy-droxy-pyridine-2-carboxyl-ate  

PubMed Central

In the 3-hy­droxy­picolinate anion of the title salt, C6H9N2 +·C6H4NO3 ?, an intra­molecular O—H?O hydrogen bond with an S(6) graph-set motif is formed, so that the anion is essentially planar, with a dihedral angle of 9.55?(9)° between the pyridine ring and the carboxyl­ate group. In the crystal, the cations and anions are linked via N—H?O hydrogen bonds, forming a centrosymmetric 2 + 2 aggregate with R 2 2(8) and R 4 2(8) ring motifs. The crystal structure also features N—H?N and weak C—H?? inter­actions.

Farhadikoutenaei, Abbas; Thanigaimani, Kaliyaperumal; Arshad, Suhana; Razak, Ibrahim Abdul

2013-01-01

364

Group-ICA Model Order Highlights Patterns of Functional Brain Connectivity  

PubMed Central

Resting-state networks (RSNs) can be reliably and reproducibly detected using independent component analysis (ICA) at both individual subject and group levels. Altering ICA dimensionality (model order) estimation can have a significant impact on the spatial characteristics of the RSNs as well as their parcellation into sub-networks. Recent evidence from several neuroimaging studies suggests that the human brain has a modular hierarchical organization which resembles the hierarchy depicted by different ICA model orders. We hypothesized that functional connectivity between-group differences measured with ICA might be affected by model order selection. We investigated differences in functional connectivity using so-called dual regression as a function of ICA model order in a group of unmedicated seasonal affective disorder (SAD) patients compared to normal healthy controls. The results showed that the detected disease-related differences in functional connectivity alter as a function of ICA model order. The volume of between-group differences altered significantly as a function of ICA model order reaching maximum at model order 70 (which seems to be an optimal point that conveys the largest between-group difference) then stabilized afterwards. Our results show that fine-grained RSNs enable better detection of detailed disease-related functional connectivity changes. However, high model orders show an increased risk of false positives that needs to be overcome. Our findings suggest that multilevel ICA exploration of functional connectivity enables optimization of sensitivity to brain disorders.

Abou Elseoud, Ahmed; Littow, Harri; Remes, Jukka; Starck, Tuomo; Nikkinen, Juha; Nissila, Juuso; Timonen, Markku; Tervonen, Osmo; Kiviniemi, Vesa

2011-01-01

365

Carboxylate modified porous graphitic carbon: a new class of hydrophilic interaction liquid chromatography phases.  

PubMed

Stationary phases for hydrophilic interaction liquid chromatography (HILIC) are predominantly based on silica and polymer supports. We present porous graphitic carbon particles with covalently attached carboxylic acid groups (carboxylate-PGC) as a new HILIC stationary phase. PGC particles were modified by adsorbing the diazonium salt of 4-aminobenzoic acid onto the PGC, followed by reduction of the adsorbed salt with sodium borohydride. The newly developed carboxylate-PGC phase exhibits different selectivity than that of 35 HPLC columns, including bare silica, zwitterionic, amine, reversed, and unmodified PGC phases. Carboxylate-PGC is stable from pH 2.0 to 12.6, yielding reproducible retention even at pH 12.6. Characterization of the new phase is presented by X-ray photoelectron spectroscopy, thermogravimetry, zeta potentials, and elemental analysis. The chromatographic performance of carboxylate-PGC as a HILIC phase is illustrated by separations of carboxylic acids, nucleotides, phenols, and amino acids. PMID:23701017

Wahab, M Farooq; Ibrahim, Mohammed E A; Lucy, Charles A

2013-06-07

366

Poly[diaqua-(?-oxalato)(?-2-oxidopyridinium-3-carboxyl-ato)lanthanum(III)  

PubMed Central

In the title complex, [La(C6H4NO3)(C2O4)(H2O)2]n, the LaIII ion is coordinated by eight O atoms from two 2-oxido­pyridinium-3-carboxyl­ate ligands, two oxalate ligands and two water mol­ecules in a distorted bicapped square-anti­prismatic geometry. The carboxyl­ate groups link adjacent LaIII ions, forming two-dimensional layers that are further linked by N—H?O and O—H?O hydrogen bonds.

Hu, Zhen; Zhu, Zhi-Bo

2009-01-01

367

Caspar carboxylates: the structural basis of tobamovirus disassembly.  

PubMed Central

Carboxylate groups have been known for many years to drive the disassembly of simple viruses, including tobacco mosaic virus (TMV). The identities of the carboxylate groups involved and the mechanism by which they initiate disassembly have not, however, been clear. Structures have been determined at resolutions between 2.9 and 3.5 A for five tobamoviruses by fiber diffraction methods. Site-directed mutagenesis has also been used to change numerous carboxylate side chains in TMV to the corresponding amides. Comparison of the stabilities of the various mutant viruses shows that disassembly is driven by a much more complex set of carboxylate interactions than had previously been postulated. Despite the importance of the carboxylate interactions, they are not conserved during viral evolution. Instead, it appears that during evolution, patches of electrostatic interaction drift across viral subunit interfaces. The flexibility of these interactions confers a considerable advantage on the virus, enabling it to change its surface structure rapidly and thus evade host defenses.

Wang, H; Planchart, A; Stubbs, G

1998-01-01

368

Controlling surface functionality through generation of thiol groups in a self-assembled monolayer.  

PubMed

A lithographic method to generate reactive thiol groups on functionalized synthetic diamond for biosensor and molecular electronic applications is developed. We demonstrate that ultrananocrystalline diamond (UNCD) thin films covalently functionalized with surface-generated thiol groups allow controlled thiol-disulfide exchange surface hybridization processes. The generation of the thiol functional head groups was obtained by irradiating phenylsulfonic acid (PSA) monolayers on UNCD surfaces. The conversion of the functional headgroup of the self-assembled monolayer was verified by using X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS), and fluorescence microscopy. Our findings indicate the selective generation of reactive thiol surface groups. Furthermore, we demonstrate the grafting of yeast cytochrome c to the thiol-modified diamond surface and the electron transfer between protein and electrode. PMID:20845943

Lud, Simon Q; Neppl, Stefan; Richter, Gerhard; Bruno, Paola; Gruen, Dieter M; Jordan, Rainer; Feulner, Peter; Stutzmann, Martin; Garrido, Jose A

2010-10-19

369

Controlling surface functionality through generation of thiol groups in a self-assembled monolayer.  

SciTech Connect

A lithographic method to generate reactive thiol groups on functionalized synthetic diamond for biosensor and molecular electronic applications is developed. We demonstrate that ultrananocrystalline diamond (UNCD) thin films covalently functionalized with surface-generated thiol groups allow controlled thiol-disulfide exchange surface hybridization processes. The generation of the thiol functional head groups was obtained by irradiating phenylsulfonic acid (PSA) monolayers on UNCD surfaces. The conversion of the functional headgroup of the self-assembled monolayer was verified by using X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS), and fluorescence microscopy. Our findings indicate the selective generation of reactive thiol surface groups. Furthermore, we demonstrate the grafting of yeast cytochrome c to the thiol-modified diamond surface and the electron transfer between protein and electrode.

Lud, S. Q.; Neppl, S.; Richter, G.; Bruno, P.; Gruen, D. M.; Jordan, R.; Feulner, P.; Stutzmann, M.; Garrido, J. A.; Materials Science Division; Technische Univ. Munchen

2010-01-01

370

GROUP  

Microsoft Academic Search

In this paper we continue the study ofalg 1 (S) for minimal surfaces of general type S satisfying K2 S < 3?(S). We show that, if K 2 S = 3?(S) 1 and |?alg 1 (S)| = 8, then S is a Campedelli surface. In view of the results of (MP1) and (MP2), this implies that the fundamental group of

CIRO CILIBERTO; MARGARIDA MENDES LOPES; RITA PARDINI

371

Comparability of composition of carbon functional groups in humic acids between inverse-gated decoupling and cross polarization/magic angle spinning 13C nuclear magnetic resonance techniques.  

PubMed

To find a certain relation between the composition of carbon functional groups of humic acids derived from liquid state (13)C nuclear magnetic resonance (NMR) spectra acquired with inverse-gated decoupling (IGD), known as a quantitative pulse sequence, and that by solid-state (13)C NMR with cross polarization/magic angle spinning (CPMAS) techniques, fifteen soil humic acid samples with a wide range of aromaticity were analyzed. Relationships between the proportions of humic acid carbon as alkyl, O-alkyl, and aromatic carbon assessed by the two methods could be regressed to y=ax (r=0.932-0.956; P<0.005), respectively. The contents of alkyl, O-alkyl, and aromatic carbon assessed by CPMAS method were larger than those found by IGD method. However, the differences between the two methods were small and exclusive regression to y=x was also significant (r=0.775-0.941; P<0.005). Aromaticity calculated from (13)C CPMAS NMR data also did not differ significantly from those computed from (13)C NMR spectra with IGD. These observations indicated the comparability of the relative content of carbon functional groups in humic acids except for carboxyl and carbonyl carbon. PMID:18501252

Watanabe, Akira; Fujitake, Nobuhide

2008-04-26

372

Characterization of acidic property of sulfo-group functionalized microporous and mesoporous silica by adsorption microcalorimetry  

Microsoft Academic Search

Sulfo-group functionalized microporous and mesoporous silica based-on a MCM-41 framework which showed solid acid property were synthesized and characterized by adsorption microcalorimetry. Both the sulfo-functionalized microporous and mesoporous silica (Micro-SO3H and Meso-SO3H) were prepared by the oxidation of thiol group (–SH) included mesoporous silica which was obtained through the hydrolysis and co-condensation of tetramethoxysilane (TMOS) and mercaptopropyl trimethoxysilane (MPTMS). The

Fei-Yee Yeoh; Akihiko Matsumoto; Yoshiyuki Iwase; Toshihide Baba

2008-01-01

373

Characterization of polysiloxanes with different functional groups by time-of-flight secondary ion mass spectrometry  

Microsoft Academic Search

Polydimethylsiloxane (PDMS), polyhydromethylsiloxane (PHMS), and polymethylphenylsiloxane (PMPhS) have been studied by TOF-SIMS\\u000a to investigate effects of functional group changes on polymer fragmentation mechanisms. Cyclic fragments are observed in the\\u000a low mass range spectra of PDMS and PHMS, but not in the spectrum of PMPhS. Effects of functional group substitution on the\\u000a fragmentation mechanisms of polysiloxanes are evident in the high

Xia Dong; Arkady Gusev; David M. Hercules

1998-01-01

374

Detection of low concentration oxygen containing functional groups on activated carbon fiber surfaces through fluorescent labeling  

Microsoft Academic Search

Covalent fluorescent labeling of surface species (FLOSS) was used to detect relatively low concentrations of surface functional groups (OH, COOH and CHO) on activated carbon fiber surfaces. The chromophores were attached to the surface through a reaction specific to each type of surface functional group. FLOSS indicated the presence of 8.7×1011COOHgroups\\/cm2 and 1.3×1012CHOgroups\\/cm2 on the ACF 25 fiber surface. Neither

Xue Feng; Nikolay Dementev; Wenguo Feng; Radisav Vidic; Eric Borguet

2006-01-01

375

Quantification of surface functional groups on polymer microspheres by supramolecular host-guest interactions.  

PubMed

We introduce a method to determine the number of accessible functional groups on a polymer microsphere surface based on the interaction between the macrocyclic host cucurbit[7]uril (CB7) and a guest reacted to the microsphere surface. After centrifugation, CB7 in the supernatant is quantified by addition of a fluorescent dye. The difference between added and detected CB7 affords the number of accessible surface functional groups. PMID:21647510

Hennig, Andreas; Hoffmann, Angelika; Borcherding, Heike; Thiele, Thomas; Schedler, Uwe; Resch-Genger, Ute

2011-06-07

376

Identifying functional groups of phytoplankton using data from three lakes of different trophic state  

Microsoft Academic Search

.  There is tremendous diversity in species of phytoplankton. Yet one may expect some degree of commonality in the response of\\u000a similar species to similar conditions. Functional groups are those sets of species that respond similarly to environmental\\u000a conditions because they have similar properties. The identification of such functional groups can assist model-based prediction\\u000a of the abundance of phytoplankton as a

Johanna Mieleitner; Mark Borsuk; Hans-Rudolf Bürgi; Peter Reichert

2008-01-01

377

Colonization, tolerance, competition and seed-size variation within functional groups  

Microsoft Academic Search

Ecologists interested in seed size have generally contrasted functional groups of plants but, recently, some have focussed on explaining the large range of seed size found within a functional group. A potentially important theoretical advance was the idea that seed number–seedling survival tradeoffs could explain the coexistence of species, in particular colonization–competition tradeoffs where smaller-seeded species are superior colonizers and

David A. Coomes; Peter J. Grubb

2003-01-01

378

Heat capacity, saturation vapor pressure, and thermodynamic functions of ethyl esters of C3-C5 and C18 carboxylic acids  

NASA Astrophysics Data System (ADS)

The heat capacities of ethyl propanoate (EPr), ethyl n-pentanoate (EPen), and ethyl n-octadecanoate (ethyl stearate, ESt) were measured by vacuum adiabatic calorimetry in the temperature range of 6 to 373 K. Triple point temperatures, fusion enthalpies and entropies, and purity of the samples of the sub-stances under study were determined. The saturation vapor pressures for EPr and EPen were determined by comparative ebulliometry in an atmospheric pressure range of 4.0 to 101.7 kPa. The normal boiling points and vaporization enthalpies vs. temperature were obtained. The standard thermodynamic functions ( S, H, and G) were calculated for the condensed and ideal gas states on the basis of the experimental data. The vapor pressures of the atmospheric range were extrapolated to entire ranges of the liquid phases of EPr and EPen using the principle of corresponding states and the combined processing of pT parameters and low-temperature differences in the heat capacities of an ideal gas and liquid.

Agafonova, L. E.; Varushchenko, R. M.; Druzhinina, A. I.; Polyakova, O. V.; Kolesov, Yu. S.

2011-09-01

379

Density-functional-theory investigation of conformations, C13 shielding, and magnetic field interactions in a V-shaped phenylene bis carboxylate homologous series  

NASA Astrophysics Data System (ADS)

Density functional theory (DFT) has been employed in a conformational study of a bent-core PBBC homologous series. IR spectra, GIAO-DFT chemical shielding tensors (CSTs), and molecular susceptibility tensors (MSTs) are theoretically calculated for various optimized conformations established by searching the potential energy surface of each PBBC V-shaped molecule. The IR results could aid the understanding of vibration normal modes, while the MST results can illuminate the alignment properties of the V-shaped molecules in an external magnetic field. CSTs of the aromatic carbons, and those previously measured by the 2D-NMR SUPER technique (with some C13 NMR peaks reassigned for correctness based on new DFT calculations), were found to be in good agreement. These verified experimental CSTs are then used to revisit the C13 NMR data to yield structural and local orientational order parameters for two members of the PBBC series. The PBBC series studied using the combined DFT-C13 NMR approach strongly supports the notion that lesser populated conformational states found by DFT could be reached in the studied mesogens 10DClPBBC and 11ClPBBC upon decreasing temperature, as revealed by the change in the bend angle determined by NMR and identified with those of the DFT molecular structures optimized for various conformers.

Marini, Alberto; Dong, Ronald Y.

2011-04-01

380

Computations for Group Sequential Boundaries Using the Lan-DeMets Spending Function Method  

Microsoft Academic Search

We describe an interactive Fortran program which performs computations related to the design and analysis of group sequential clinical trials using Lan-DeMets spending functions. Many clinical trials include interim analyses of accumulating data and rely on group sequential methods to avoid consequent inflation of the type I error rate. The computations are appropriate for interim test statistics whose distribution or

David M. Reboussin; David L. DeMets; KyungMann Kim; K. K. Gordon Lan

2000-01-01

381

Characteristics of Interactional Management Functions in Group Oral by Japanese Learners of English  

ERIC Educational Resources Information Center

This study attempted to investigate the characteristics of interaction dynamics in a group oral interaction carried out by Japanese learners of English. The relationship between the participants' language development and interactional management functions (IMFs) was also explored. Oral performance tests in a paired or a small group have recently…

Negishi, Junko

2010-01-01

382

Aggressive and Prosocial Peer Group Functioning: Effects on Children's Social, School, and Psychological Adjustment  

ERIC Educational Resources Information Center

|This study examined the effects of aggressive and prosocial contexts of peer groups on children's socioemotional and school adjustment. Data on informal peer groups, social functioning, and different aspects of adjustment were collected from multiple sources in a sample of elementary school children (149 boys, 181 girls; M age = 10 years).…

Chung-Hall, Janet; Chen, Xinyin

2010-01-01

383

Identification of Differential Item Functioning in Multiple-Group Settings: A Multivariate Outlier Detection Approach  

ERIC Educational Resources Information Center

|We focus on the identification of differential item functioning (DIF) when more than two groups of examinees are considered. We propose to consider items as elements of a multivariate space, where DIF items are outlying elements. Following this approach, the situation of multiple groups is a quite natural case. A robust statistics technique is…

Magis, David; De Boeck, Paul

2011-01-01

384

Spatial distribution of main forest soil groups in Croatia as a function of basic pedogenetic factors  

Microsoft Academic Search

The model of spatial distribution of main forest soil groups in Croatia was developed as a function of basic pedogenetic factors: lithological substratum, macroclimate and relief. Used data about soil group, lithological substratum, terrain slope and aspect were collected on 1881 soil profiles. Macroclimatic data were estimated for each soil profile by spatial interpolation between meteorological stations. Feedforward neural networks

Oleg Antoni; Nikola Pernar; Sven D. Jelaska

2003-01-01

385

Functions Preserving Matrix Groups and Iterations for the Matrix Square Root  

Microsoft Academic Search

For which functions f does A ? G ? f (A) ? G when G is the matrix automorphism group associated with a bilinear or sesquilinear form? For example, if A is symplectic when is f (A) symplectic? We show that group structure is preserved precisely when f (A?1 )= f (A)?1 for bilinear forms and when f (A?? )=

Nicholas J. Higham; D. Steven Mackey; Niloufer Mackey; Franc?oise Tisseur

2005-01-01

386

Perceptions of popularity among a group of high-functioning adults with autism  

Microsoft Academic Search

The purpose of this study was to determine how a group of adults with autism perceived one another's interpersonal attributes and popularity. Five female and 11 male high-functioning autistic adults, 18–45 years old, participated in a social skills group together for several years. A sociogram and a questionnaire designed to determine perceptions of best looking, most athletic, and most humorous

Gary B. Mesibov; Janet Stephens

1990-01-01

387

Identification of Differential Item Functioning in Multiple-Group Settings: A Multivariate Outlier Detection Approach  

Microsoft Academic Search

We focus on the identification of differential item functioning (DIF) when more than two groups of examinees are considered. We propose to consider items as elements of a multivariate space, where DIF items are outlying elements. Following this approach, the situation of multiple groups is a quite natural case. A robust statistics technique is proposed to identify DIF items as

David Magis; Paul De Boeck

2011-01-01

388

The Use of Language Functions in Mathematical Group Games. Teacher Insights.  

ERIC Educational Resources Information Center

|Six group games were introduced into a second-grade bilingual classroom. Children's talk during each game was classified using a modification of Dyson's five language functions (representational, directive, heuristic, personal, and interactional). Group games provided many communication opportunities. Some children tried new communication styles.…

Black, Carolyn; Huerta, Maria G.

1994-01-01

389

Polymerization process for carboxyl containing polymers utilizing oil soluble ionic surface active agents  

Microsoft Academic Search

This patent describes a method for polymerizing olefinically unsaturated carboxylic acid monomers containing at least one activated carbon to carbon olefinic double bond and at least one carboxyl group. The monomers are polymerized in an organic media consisting essentially of organic liquids, in the presence of free radical forming catalysts and at least one oil soluble ionic surface active agent

C. E. Uebele; L. E. Ball; R. J. II Jorkasky; E. Jr. Wardlow

1987-01-01

390

Diimide reduction of carboxylated styrene–butadiene rubber in latex stage  

Microsoft Academic Search

Carboxylated styrene–butadiene rubber (XSBR) is selectively hydrogenated by diimide reduction technique in latex stage using hydrazine hydrate, hydrogen peroxide and Cu+2 as catalyst. The products are characterised by IR and NMR spectroscopy. Dynamic Mechanical Properties and Transmission Electron Micrographs of the hydrogenated products confirm the existence of ionic aggregates involving carboxyl (–COOH) groups of the substrate and externally added Cu+2

M. De Sarkar; P. P. De; A. K. Bhowmick

2000-01-01

391

Prediction of Functional Sites in Proteins Using Conserved Functional Group Analysis  

Microsoft Academic Search

A detailed knowledge of a protein's functional site is an absolute prerequisite for understanding its mode of action at the molecular level. However, the rapid pace at which sequence and structural information is being accumulated for proteins greatly exceeds our ability to determine their biochemical roles experimentally. As a result, computational methods are required which allow for the efficient processing

C. Axel Innis; A. Prem Anand; R. Sowdhamini

2004-01-01

392

Functional group biodiversity in Eastern Boundary Upwelling Ecosystems questions the wasp-waist trophic structure  

Microsoft Academic Search

The species diversity of the four major Eastern Boundary Upwelling Ecosystems (EBUEs) is studied and compared with the aim of better understanding their functioning. Functional groups (FGs) of organisms were defined according to their taxonomy, body size and trophic level (TL), and span from plankton to top predators. Four large sub-divisions are defined in each system: two latitudinal sub-divisions (north

Pierre Fréon; Javier Arístegui; Arnaud Bertrand; Robert J. M. Crawford; John C. Field; Mark J. Gibbons; Jorge Tam; Larry Hutchings; Hicham Masski; Christian Mullon; Mohamed Ramdani; Bernard Seret; Monique Simier

2009-01-01

393

Key Neurological Impairments Influence Function-Related Group Outcomes After Stroke  

Microsoft Academic Search

Background and Purpose—The function-related group (FRG) classification is based on functional assessment and has been assumed to encompass the effects of different patterns and severity of neurological impairments. This assumption may not be correct. It has been proposed as a means of comparing rehabilitation outcome across institutions. If neurological impairments significantly affect FRG outcome, then higher FRG outcome scores may

Lu Han; Diane Law-Gibson; Michael Reding

394

Functional Assignments for the Carboxyl-Terminal Domains of the Ferrochelatase from Synechocystis PCC 6803: The CAB Domain Plays a Regulatory Role, and Region II Is Essential for Catalysis1[W  

PubMed Central

Ferrochelatase (FeCH) catalyzes the insertion of Fe2+ into protoporphyrin, forming protoheme. In photosynthetic organisms, FeCH and magnesium chelatase lie at a biosynthetic branch point where partitioning down the heme and chlorophyll (Chl) pathways occurs. Unlike their mammalian, yeast, and other bacterial counterparts, cyanobacterial and algal FeCHs as well as FeCH2 isoform from plants possess a carboxyl-terminal Chl a/b-binding (CAB) domain with a conserved Chl-binding motif. The CAB domain is connected to the FeCH catalytic core by a proline-rich linker sequence (region II). In order to dissect the regulatory, catalytic, and structural roles of the region II and CAB domains, we analyzed a FeCH ?H347 mutant that retains region II but lacks the CAB domain and compared it with the ?H324-FeCH mutant that lacks both these domains. We found that the CAB domain is not required for catalytic activity but is essential for dimerization of FeCH; its absence causes aberrant accumulation of Chl-protein complexes under high light accompanied by high levels of the Chl precursor chlorophyllide. Thus, the CAB domain appears to serve mainly a regulatory function, possibly in balancing Chl biosynthesis with the synthesis of cognate apoproteins. Region II is essential for the catalytic function of the plastid-type FeCH enzyme, although the low residual activity of the ?H324-FeCH is more than sufficient to furnish the cellular demand for heme. We propose that the apparent surplus of FeCH activity in the wild type is critical for cell viability under high light due to a regulatory role of FeCH in the distribution of Chl into apoproteins.

Sobotka, Roman; Tichy, Martin; Wilde, Annegret; Hunter, C. Neil

2011-01-01

395

Functional assignments for the carboxyl-terminal domains of the ferrochelatase from Synechocystis PCC 6803: the CAB domain plays a regulatory role, and region II is essential for catalysis.  

PubMed

Ferrochelatase (FeCH) catalyzes the insertion of Fe(2+) into protoporphyrin, forming protoheme. In photosynthetic organisms, FeCH and magnesium chelatase lie at a biosynthetic branch point where partitioning down the heme and chlorophyll (Chl) pathways occurs. Unlike their mammalian, yeast, and other bacterial counterparts, cyanobacterial and algal FeCHs as well as FeCH2 isoform from plants possess a carboxyl-terminal Chl a/b-binding (CAB) domain with a conserved Chl-binding motif. The CAB domain is connected to the FeCH catalytic core by a proline-rich linker sequence (region II). In order to dissect the regulatory, catalytic, and structural roles of the region II and CAB domains, we analyzed a FeCH ?H347 mutant that retains region II but lacks the CAB domain and compared it with the ?H324-FeCH mutant that lacks both these domains. We found that the CAB domain is not required for catalytic activity but is essential for dimerization of FeCH; its absence causes aberrant accumulation of Chl-protein complexes under high light accompanied by high levels of the Chl precursor chlorophyllide. Thus, the CAB domain appears to serve mainly a regulatory function, possibly in balancing Chl biosynthesis with the synthesis of cognate apoproteins. Region II is essential for the catalytic function of the plastid-type FeCH enzyme, although the low residual activity of the ?H324-FeCH is more than sufficient to furnish the cellular demand for heme. We propose that the apparent surplus of FeCH activity in the wild type is critical for cell viability under high light due to a regulatory role of FeCH in the distribution of Chl into apoproteins. PMID:21081693

Sobotka, Roman; Tichy, Martin; Wilde, Annegret; Hunter, C Neil

2010-11-16

396

Selective Cleavage of Functional Groups in the Functionalized Organic Monolayers by Synchrotron Soft X-Rays  

Microsoft Academic Search

Aminosilylated surface was treated with halide-substituted aromatic aldehydes, and the resulting molecular layers were examined with synchrotron X-ray photoelectron spectroscopy at the 2B1 SGM and 4B1 microscopy beamline in the Pohang Accelerator Laboratory. It was observed that the halide group of the film diminished upon the irradiation, but the other bands were constant in terms of the intensity and the

Tai-Hee Kang; Ki-Jeong Kim; Chan-Cuk Hwang; Kyu-Wook Ihm; Hyun-Joon Shin; Min-Kyu Lee; Bongsoo Kim; Chong-Yun Park; Young-Hye La; Joong Ho Moon; Hyun Ju Kim; Joon Won Park

2002-01-01

397

Functional specialization and generalization for grouping of stimuli based on colour and motion  

PubMed Central

This study was undertaken to learn whether the principle of functional specialization that is evident at the level of the prestriate visual cortex extends to areas that are involved in grouping visual stimuli according to attribute, and specifically according to colour and motion. Subjects viewed, in an fMRI scanner, visual stimuli composed of moving dots, which could be either coloured or achromatic; in some stimuli the moving coloured dots were randomly distributed or moved in random directions; in others, some of the moving dots were grouped together according to colour or to direction of motion, with the number of groupings varying from 1 to 3. Increased activation was observed in area V4 in response to colour grouping and in V5 in response to motion grouping while both groupings led to activity in separate though contiguous compartments within the intraparietal cortex. The activity in all the above areas was parametrically related to the number of groupings, as was the prominent activity in Crus I of the cerebellum where the activity resulting from the two types of grouping overlapped. This suggests (a) that, the specialized visual areas of the prestriate cortex have functions beyond the processing of visual signals according to attribute, namely that of grouping signals according to colour (V4) or motion (V5); (b) that the functional separation evident in visual cortical areas devoted to motion and colour, respectively, is maintained at the level of parietal cortex, at least as far as grouping according to attribute is concerned; and (c) that, by contrast, this grouping-related functional segregation is not maintained at the level of the cerebellum.

Zeki, Semir; Stutters, Jonathan

2013-01-01

398

Functional specialization and generalization for grouping of stimuli based on colour and motion.  

PubMed

This study was undertaken to learn whether the principle of functional specialization that is evident at the level of the prestriate visual cortex extends to areas that are involved in grouping visual stimuli according to attribute, and specifically according to colour and motion. Subjects viewed, in an fMRI scanner, visual stimuli composed of moving dots, which could be either coloured or achromatic; in some stimuli the moving coloured dots were randomly distributed or moved in random directions; in others, some of the moving dots were grouped together according to colour or to direction of motion, with the number of groupings varying from 1 to 3. Increased activation was observed in area V4 in response to colour grouping and in V5 in response to motion grouping while both groupings led to activity in separate though contiguous compartments within the intraparietal cortex. The activity in all the above areas was parametrically related to the number of groupings, as was the prominent activity in Crus I of the cerebellum where the activity resulting from the two types of grouping overlapped. This suggests (a) that, the specialized visual areas of the prestriate cortex have functions beyond the processing of visual signals according to attribute, namely that of grouping signals according to colour (V4) or motion (V5); (b) that the functional separation evident in visual cortical areas devoted to motion and colour, respectively, is maintained at the level of parietal cortex, at least as far as grouping according to attribute is concerned; and (c) that, by contrast, this grouping-related functional segregation is not maintained at the level of the cerebellum. PMID:23415950

Zeki, Semir; Stutters, Jonathan

2013-02-13

399

Classifying proteins into functional groups based on all-versus-all BLAST of 10 million proteins.  

PubMed

To address the monumental challenge of assigning function to millions of sequenced proteins, we completed the first of a kind all-versus-all sequence alignments using BLAST for 9.9 million proteins in the UniRef100 database. Microsoft Windows Azure produced over 3 billion filtered records in 6 days using 475 eight-core virtual machines. Protein classification into functional groups was then performed using Hive and custom jars implemented on top of Apache Hadoop utilizing the MapReduce paradigm. First, using the Clusters of Orthologous Genes (COG) database, a length normalized bit score (LNBS) was determined to be the best similarity measure for classification of proteins. LNBS achieved sensitivity and specificity of 98% each. Second, out of 5.1 million bacterial proteins, about two-thirds were assigned to significantly extended COG groups, encompassing 30 times more assigned proteins. Third, the remaining proteins were classified into protein functional groups using an innovative implementation of a single-linkage algorithm on an in-house Hadoop compute cluster. This implementation significantly reduces the run time for nonindexed queries and optimizes efficient clustering on a large scale. The performance was also verified on Amazon Elastic MapReduce. This clustering assigned nearly 2 million proteins to approximately half a million different functional groups. A similar approach was applied to classify 2.8 million eukaryotic sequences resulting in over 1 million proteins being assign to existing KOG groups and the remainder clustered into 100,000 functional groups. PMID:21809957

Kolker, Natali; Higdon, Roger; Broomall, William; Stanberry, Larissa; Welch, Dean; Lu, Wei; Haynes, Winston; Barga, Roger; Kolker, Eugene

400

Tensor renormalization group: Local magnetizations, correlation functions, and phase diagrams of systems with quenched randomness  

NASA Astrophysics Data System (ADS)

The tensor renormalization-group method, developed by Levin and Nave, brings systematic improvability to the position-space renormalization-group method and yields essentially exact results for phase diagrams and entire thermodynamic functions. The method, previously used on systems with no quenched randomness, is extended in this study to systems with quenched randomness. Local magnetizations and correlation functions as a function of spin separation are calculated as tensor products subject to renormalization-group transformation. Phase diagrams are extracted from the long-distance behavior of the correlation functions. The approach is illustrated with the quenched bond-diluted Ising model on the triangular lattice. An accurate phase diagram is obtained in temperature and bond-dilution probability for the entire temperature range down to the percolation threshold at zero temperature.

Güven, Can; Hinczewski, Michael; Berker, A. Nihat

2010-11-01

401

Synthesis and characterization of homo- and heterovalent tetra- hexa- hepta- and decanuclear manganese clusters using pyridyl functionalized beta-diketone, carboxylate and triethanolamine ligands.  

PubMed

The syntheses and characterizations are reported for six new homo- and heterovalent manganese clusters, utilizing pyridyl functionalized beta-diketones ligands. The reaction of the trinuclear complex [Mn3O(O2CPh)6(H2O)(Py)2] with 1,3-di(pyridine-2-yl)propane-1,3-dione (dppdH) in CH2Cl2 resulted in a mixed-valence Mn3(II)Mn6(III)Mn(IV) decanuclear cluster of formula [Mn10O7(dppd)3(O2CPh)11] x 4 CH2Cl2 (1). The structure of the core of 1 is based upon a centred tricapped trigonal prism. Reacting Mn(BF4)2 x xH2O with dppdH and triethylamine (NEt3) in CH2Cl2-MeOH gave a rare, homoleptic hexanuclear cluster of formula [Mn(II)6(dppd)8][BF4]4 (2) which has a triangular based core. Reaction of Mn(Y)2 x xH2O, Y = NO3(-) or BF4(-), with dppdH or 1-phenyl-3-(2-pyridyl)propane-1,3-dione (pppdH) in the presence of triethanolamine (teaH3) and NEt3 gave a heptanuclear 'disc' like manganese core of general formula [Mn(II)7(X)6(tea)(OH)3][Y]2 x solv (3) X = pppd- or dppd- and Y = NO3(-) or BF4(-). The addition of N-(2-pyridinyl)acetoacetamide (paaH) to Mn(Y)2 x 4 H2O Y = NO3(-) or ClO4(-) in MeOH gave a second divalent heptanuclear cluster with a 'disc'-like core of general formula [Mn7(paa)6(OMe)6][X]2 x solv (4) (X = NO3(-) or ClO4(-)), whilst the addition of paaH to a mixture of Mn(NO3)2 x 4 H2O, teaH3 and NEt3 in CH2Cl2-MeOH resulted in the formation of a mixed-valence Mn2(II)Mn2(III) tetranuclear 'butterfly' complex of formula [Mn4(paa)4(teaH)2][NO3]2 x 2 MeOH x 2 CH2Cl2 (5). Compound 5 displays the rare Mn(II/III) oxidation state distribution of the body positions being Mn(II) while the wing tips are Mn(III). The in situ formation of the tetranuclear [Mn4(teaH)2(teaH2)2(O2C(CH3)3)2][O2C(CH3)3]2 'butterfly' complex followed by the addition of Mn(O2CMe)2 x 4 H2O resulted in a mixed-valence Mn4(II)Mn(III)Mn(IV) hexanuclear species of formula [Mn6O2(teaH2)4(O2CMe)4][NO3]2[O2CMe] x CH2Cl2 x MeOH x 2 H2O (6). The core of 6 displays a face sharing dicubane topology. Compounds 1 and 6 both display novel trapped-valence metal cores containing three different oxidation states on the manganese ion. Compounds 1, 2 and 3 are the first manganese based dppd clusters, while 4 and 5 are the first with the pyridylamino-substituted beta-diketone ligand (paaH). The magnetic data for 1, 2, 3, 4, and 6 are dominated by antiferromagnetic interactions within the clusters, leading to small ground spin values of S = 1 for 1, S = 3 for 2, S = 5/2 for 3, S = 5/2 for 4 and S = 1/2 for 6. Compound 5, however, displays overall ferromagnetic interactions with the data indicating an S = 6 ground state. 5 also exhibits probable single molecule magnet behaviour as indicated by frequency dependent out-of-phase chiM'' peaks in the AC susceptibility measurements. PMID:20617238

Langley, Stuart K; Chilton, Nicholas F; Massi, Massimiliano; Moubaraki, Boujemaa; Berry, Kevin J; Murray, Keith S

2010-07-08

402

Separation of certain carboxylic acids utilizing cation exchange membranes  

DOEpatents

A method of substantially separating monofunctional lower carboxylic acids from a liquid mixture containing the acids wherein the pH of the mixture is adjusted to a value in the range of from about 1 to about 5 to form protonated acids. The mixture is heated to an elevated temperature not greater than about 100/sup 0/C and brought in contact with one side of a perfluorinated cation exchange membrane having sulfonate or carboxylate groups or mixtures thereof with the mixture containing the protonated acids. A pressure gradient can be established across the membrane with the mixture being under higher pressure, so that protonated monofunctional lower carboxylic acids pass through the membrane at a substantially faster rate than the remainder of the mixture thereby substantially separating the acids from the mixture.

Chum, H.L.; Sopher, D.W.

1983-05-09

403

Separation of certain carboxylic acids utilizing cation exchange membranes  

DOEpatents

A method of substantially separating monofunctional lower carboxylic acids from a liquid mixture containing the acids wherein the pH of the mixture is adjusted to a value in the range of from about 1 to about 5 to form protonated acids. The mixture is heated to an elevated temperature not greater than about 100.degree. C. and brought in contact with one side of a perfluorinated cation exchange membrane having sulfonate or carboxylate groups or mixtures thereof with the mixture containing the protonated acids. A pressure gradient can be established across the membrane with the mixture being under higher pressure, so that protonated monofunctional lower carboxylic acids pass through the membrane at a substantially faster rate than the remainder of the mixture thereby substantially separating the acids from the mixture.

Chum, Helena L. (Arvada, CO); Sopher, David W. (Maarssenbroek, NL)

1984-01-01

404

Carboxyl pK(a) values and acid denaturation of BBL.  

PubMed

The protein BBL undergoes structural transitions and acid denaturation between pH 1.2 and 8.0. Using NMR spectroscopy, we measured the pK(a) values of all the carboxylic residues in this pH range. We employed (13)C direct-detection two-dimensional IPAP (in-phase antiphase) CACO NMR spectroscopy to monitor the ionization state of different carboxylic groups and demonstrated its advantages over other NMR techniques in measuring pK(a) values of carboxylic residues. The two residues Glu161 and Asp162 had significantly lowered pK(a) values, showing that these residues are involved in a network of stabilizing electrostatic interactions, as is His166. The other carboxylates had unperturbed values. The pH dependence of the free energy of denaturation was described quantitatively by the ionizations of those three residues of perturbed pK(a), and, using thermodynamic cycles, we could calculate their pK(a)s in the native and denatured states as well as the equilibrium constants for denaturation of the different protonation states. We also measured (13)C(?) chemical shifts of individual residues as a function of pH. These shifts sense structural transitions rather than ionizations, and they titrated with pH consistent with the change in equilibrium constant for denaturation. Kinetic measurements of the folding of BBL E161Q indicated that, at pH 7, the stabilizing interactions with Glu161 are formed mainly in the transition state. We also found that local interactions still exist in the acid-denatured state of BBL, which attenuate somewhat the flexibility of the acid-denatured state. PMID:20816989

Arbely, Eyal; Rutherford, Trevor J; Neuweiler, Hannes; Sharpe, Timothy D; Ferguson, Neil; Fersht, Alan R

2010-09-15

405

Population dynamics: seasonal variation of phytoplankton functional groups in brazilian reservoirs (Billings and Guarapiranga, São Paulo).  

PubMed

Phytoplankton may function as a 'sensor' of changes in aquatic environment and responds rapidly to such changes. In freshwaters, coexistence of species that have similar ecological requirements and show the same environmental requirements frequently occurs; such species groups are named functional groups. The use of phytoplankton functional groups to evaluate these changes has proven to be very useful and effective. Thus, the aim of this study was to evaluate the occurrence of functional groups of phytoplankton in two reservoirs (Billings and Guarapiranga) that supply water to millions of people in São Paulo city Metropolitan Area, southeastern Brazil. Surface water samples were collected monthly and physical, chemical and biological (quantitative and qualitative analyses of the phytoplankton) were performed. The highest biovolume (mm(3).L-1) of the descriptor species and functional groups were represented respectively by Anabaena circinalis Rabenh. (H1), Microcystis aeruginosa (Kützing) Kützing (L M/M) and Mougeotia sp. (T) in the Guarapiranga reservoir and Cylindrospermopsis raciborskii (Wolosz.) Seen. and Subba Raju (S N), Microcystis aeruginosa and M. panniformis Komárek et al. (L M/M), Planktothrix agardhii (Gom.) Anagn. and Komárek and P. cf. clathrata (Skuja) Anagn. and Komárek (S1) in the Billings reservoir. The environmental factors that most influenced the phytoplankton dynamics were water temperature, euphotic zone, turbidity, conductivity, pH, dissolved oxygen, nitrate and total phosphorous. PMID:19967171

Gemelgo, M C P; Mucci, J L N; Navas-Pereira, D

2009-11-01

406

Synthesis of monodisperse functional polymeric microspheres for immunoassay  

Microsoft Academic Search

Methods for the synthesis of functional polymeric suspensions with narrow particle size distribution are analysed. Attention is concentrated on the conditions of the preparation of polymeric microspheres with aldehyde, carboxyl, epoxy, or amino groups on the surface, which possess a set of properties enabling their use for biochemical studies. Methods of modification of functional groups of the polymeric suspensions that

Nikolai I Prokopov; Inessa A Gritskova; Vladimir R Cherkasov; Anatolii E Chalykh

1996-01-01

407

Ethyl 6-chloro-2-oxo-4-phenyl-1,2-dihydro-quinoline-3-carboxyl-ate.  

PubMed

In the title compound, C(18)H(14)ClNO(3), the dihydro-quinolin-2-one ring system is almost planar (r.m.s. deviation = 0.033?Å). The carboxyl-ate plane and the phenyl group are twisted away from the dihydro-quinolin-2-one ring system by 50.3?(1) and 64.9?(1)°, respectively. In the crystal structure, inversion-related mol-ecules form R(2) (2)(8) dimers via pairs of N-H?O hydrogen bonds. PMID:21578727

Khan, F Nawaz; Mittal, Suganya; Anjum, Soheil; Hathwar, Venkatesha R; Ng, Seik Weng

2009-11-04

408

Electrochemical sensor based on molecularly imprinted polymer film via sol-gel technology and multi-walled carbon nanotubes-chitosan functional layer for sensitive determination of quinoxaline-2-carboxylic acid.  

PubMed

Quinoxaline-2-carboxylic acid (QCA) is difficult to measure since only trace levels are present in commercial meat products. In this study, a rapid, sensitive and selective molecularly imprinted electrochemical sensor for QCA determination was successfully constructed by combination of a novel modified glassy carbon electrode (GCE) and differential pulse voltammetry (DPV). The GCE was fabricated via stepwise modification of multi-walled carbon nanotubes (MWNTs)-chitosan (CS) functional composite and a sol-gel molecularly imprinted polymer (MIP) film on the surface. MWNTs-CS composite was used to enhance the electron transfer rate and expand electrode surface area, and consequently amplify QCA reduction electrochemical response. The imprinted mechanism and experimental parameters affecting the performance of MIP film were discussed in detail. The resulting MIP/sol-gel/MWNTs-CS/GCE was characterized using various electrochemical methods involving cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and DPV. The sensor using MIP/sol-gel/MWNTs-CS/GCE as working electrode showed a linear current response to the target QCA concentration in the wide range from 2.0×10(-6) to 1.0×10(-3)molL(-1) with a low detection limit of 4.4×10(-7)molL(-1) (S/N=3). The established sensor with excellent reproductivity and stability was applied to evaluate commercial pork products. At five concentration levels, the recoveries and standard deviations were calculated as 93.5-98.6% and 1.7-3.3%, respectively, suggesting the proposed sensor is promising for the accurate quantification of QCA at trace levels in meat samples. PMID:23624016

Yang, Yukun; Fang, Guozhen; Liu, Guiyang; Pan, Mingfei; Wang, Xiaomin; Kong, Lingjie; He, Xinlei; Wang, Shuo

2013-04-02

409

Synthesis and adsorption of functionalized polystyrenes  

Microsoft Academic Search

The effect of specifically interacting functional groups located at the chain ends of polystyrene on the absorption rate, adsorbance, graft density and surface excess are discussed from cyclohexane, a theta solvent and toluene. Polystyrenes with hydroxyl and carboxylic acid-end-groups in narrow molecular weight distribution are synthesized by anionic polymerization of styrene followed by suitable termination reactions. Thin layer chromatography (TLC)

Iyengar

1992-01-01

410

Analysis of the Functional Significance of Linkage Group Conservation in Drosophila  

PubMed Central

Linkage groups, as defined by chromosome arms in Drosophila melanogaster, appear to have remained largely intact within the genus Drosophila and, possibly, within the higher Diptera per se. We hypothesized that linkage group conservation might have a functional basis (possibly related to interphase chromosome arrangement). To test this hypothesis, a series of autosomal 2–3 translocations were synthesized, creating many new linkage groups. A total of 167 2–3 translocations were recovered, cytologically analyzed to determine their polytene chromosome breakpoints, and tested for homozygous viability and fertility. The breakpoints associated with homozygous viable translocations were randomly distributed throughout the genome, indicating that the linear continuity of the linkage groups could be disrupted quite extensively. Inter se complementation crosses between homozygous lethal translocations having similar breakpoints further confirmed this result, documenting that, at least with respect to homozygous viability, the linear integrity of the autosomal linkage groups was not of major functional significance. Fertility analysis of the homozygous translocations also indicated that sterility could not be a single major factor. Having concluded that linkage group conservation is not based on important functional interactions between specific linked chromosomal segments, or due principally to the sterility of new linkages, the problem of linkage group conservation remains unsolved. Several possible selective factors are discussed, principally segregational load and inbreeding depression, which may contribute to the elimination of new linkage rearrangements.

Hilliker, Arthur J.; Trusis-Coulter, Silvija N.

1987-01-01

411

Functional groups of marine ciliated protozoa and their relationships to water quality.  

PubMed

Ciliated protozoa (ciliates) play important ecological roles in coastal waters, especially regarding their interaction with environmental parameters. In order to increase our knowledge and understanding on the functional structure of ciliate communities and their relationships to environmental conditions in marine ecosystems, a 12-month study was carried out in a semi-enclosed bay in northern China. Samples were collected biweekly at five sampling stations with differing levels of pollution/eutrophication, giving a total of 120 samples. Thirteen functional groups of ciliates (A-M) were defined based on their specific spatio-temporal distribution and relationships to physico-chemical parameters. Six of these groups (H-M) were the primary contributors to the ciliate communities in the polluted/eutrophic areas, whereas the other seven groups (A-G) dominated the communities in less polluted areas. Six groups (A, D, G, H, I and K) dominated during the warm seasons (summer and autumn), with the other seven (B, C, E, F, J, L and M) dominating in the cold seasons (spring and winter). Of these, groups B (mainly aloricate ciliates), I (aloricate ciliates) and L (mainly loricate tintinnids) were the primary contributors to the communities. It was also shown that aloricate ciliates and tintinnids represented different roles in structuring and functioning of the communities. The results suggest that the ciliate communities may be constructed by several functional groups in response to the environmental conditions. Thus, we conclude that these functional groups might be potentially useful bioindicators for bioassessment and conservation in marine habitats. PMID:23381800

Jiang, Yong; Xu, Henglong; Hu, Xiaozhong; Warren, Alan; Song, Weibo

2013-02-05

412

Group 3 late embryogenesis abundant protein in Arabidopsis : structure, regulation, and function  

Microsoft Academic Search

Group 3 late embryogenesis abundant proteins accumulate in maturing seeds, in which their expression correlates with desiccation\\u000a tolerance. Group 3 proteins are also strongly associated with tolerance for abiotic stresses, such as high salinity, drought,\\u000a cold, and osmotic stress in vegetative tissues. However, the precise function of these proteins remained obscure for more\\u000a than 20 years. In this study, the structure

PengShan ZhaoFei; Fei Liu; GuoChang Zheng; Heng Liu

2011-01-01

413

Role of Sulfhydryl Groups in Functioning of Adenylyl Cyclase Signaling System  

Microsoft Academic Search

This review considers the literature data and author's own results on the role of SH-groups in functioning of the hormone-sensitive adenylyl cyclase system (ACS). It has been shown that the state of SH-groups affects crucially all main stages of the hormonal signal transudation: the ligand-binding properties of receptor and its coupling to G-proteins, interaction of G-proteins with adenylyl cyclase (AC)

A. O. Shpakov

2002-01-01

414

Functional group substitutions as probes of hydrogen bonding between GA mismatches in RNA internal loops  

Microsoft Academic Search

The contribution of hydrogen bonding to the stability of GA mismatches in RNA is investigated by making functional group substitutions. Such substitutions are made possible by the chemical synthesis of RNA; chemical incorporation of purine riboside and 2-aminopurine riboside into oligoribonucleotides is reported. In particular, replacing the 6-amino groups of internal loop adenosines with hydrogen atoms in (rGC-GCG)*, ( rGGCGAGCC)2,

John SantaLucia; Ryszard Kierzek; Douglas H. Turner

1991-01-01

415

Tailoring the surface potential of gold nanoparticles with self-assembled monolayers with mixed functional groups  

Microsoft Academic Search

Self-assembled monolayer (SAM)-modified gold nanoparticles can be used to immobilize and transport molecules including DNA and proteins. However, these molecules are usually covalently bound to the surface and chemical reactions are required to cleave and release them. Therefore, immobilizing molecules using electrostatic interactions might be beneficial. In this work, Au nanoparticles modified by SAMs with mixed carboxylic acid and amine

Yu-Chin Lin; Bang-Ying Yu; Wei-Chun Lin; Szu-Hsian Lee; Che-Hung Kuo; Jing-Jong Shyue

2009-01-01

416

Habitat diversity and benthic functional trophic groups at Serra do Cipó, Southeast Brazil.  

PubMed

The assessment of the diversity of habitats and the characterisation of the functional trophic groups of benthic macroinvertebrate communities of some rivers of Serra do Cipó (MG) were the main objectives of this study. The available trophic resources and the types of substrata were characterised along with the structure and composition of their using functional trophic groups. Serra do Cipó is a watershed divisor of the São Francisco and Doce River basins, including a series of streams and rivers, of good water quality and well preserved ecological characteristics. Samples were collected in Cipó, Peixe and Preto do Itambé rivers, besides the Indaiá and Capão da Mata streams at 26 sampling stations, during the rainy (February) and dry (October) seasons of 1998, using "Kicking nets" of 0.125 mm mesh size. The group of collectors (Baetidae, Leptophlebiidae and Leptohyphidae) was the most abundant, followed by collector-predators (Hydrophilidae, Ceratopogonidae, Chironomidae-Tanypodinae), and detritivorous-herbivores (Oligochaeta). The riparian vegetation, together with the aquatic macrophytes, are the substrata containing the highest richness of functional trophic groups and the higher habitat diversity. The results suggest that the use of functional trophic groups, together with habitat evaluation, are efficient tools in the evaluation of the diversity of benthic macroinvertebrates, particularly in altitudinal lotic ecosystems. PMID:11514893

Callisto, M; Moreno, P; Barbosa, F A

2001-05-01

417

Large-cell Monte Carlo renormalization group: A new weight function for percolation  

SciTech Connect

The large-cell Monte Carlo renormalization group introduced by Reynolds, Stanley, and Klein (Phys. Rev. B 20, 1223 (1980)) is applied with a new weight function to random percolation in two and three dimensions. Our renormalization-group results show different behavior with lattice size than that observed previously. Specifically, we find that Y/sub p/ = 0.73 +- 0.01 (the correlation length exponent ..nu.. = 1.37) in two dimensions and Y/sub p/ = 1.124 +- 0.004 (..nu.. = 0.89) in three dimensions. This weight function allows for easy analysis of percolation in higher dimensions.

Jan, N.; Hunter, D.L.; Lookman, T.

1984-06-01

418

Effects of surface functional groups on the formation of nanoparticle-protein corona  

NASA Astrophysics Data System (ADS)

Herein, we examined the dependence of protein adsorption on the nanoparticle surface in the presence of functional groups. Our UV-visible spectrophotometry, transmission electron microscopy, infrared spectroscopy, and dynamic light scattering measurements evidently suggested that the functional groups play an important role in the formation of nanoparticle-protein corona. We found that uncoated and surfactant-free silver nanoparticles derived from a laser ablation process promoted a maximum protein (