Note: This page contains sample records for the topic carboxyl functional groups from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Gas-Phase Reactivity of Carboxylic Acid Functional Groups with Carbodiimides  

PubMed Central

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.

2012-01-01

2

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

3

Chemical Functionalization of Graphene Nanoribbons by Carboxyl Groups on Stone-Wales Defects  

Microsoft Academic Search

Using the density functional theory, we have demonstrated the chemical functionalization of semiconducting graphene nanoribbons (GNRs) with Stone-Wales (SW) defects by carboxyl (COOH) groups. It is found that the geometrical structures and electronic properties of the GNRs changed significantly, and the electrical conductivity of the system could be considerably enhanced by mono-adsorption and double-adsorption of COOH, which sensitively depends upon

Fangping OuYang; Bing Huang; Zuanyi Li; Hui Xu

2007-01-01

4

Effect of Functionalized Carbon Nanotubes with Carboxylic Functional Group on the Mechanical and Thermal Properties of Styrene Butadiene Rubber  

Microsoft Academic Search

Multi-walled carbon nanotubes (MWCNTs) were functionalized with a carboxylic functional group to enhance the dispersion of CNT in styrene butadiene rubber (SBR) nanocomposites. The functionalization of the surface of the MWCNTs were carried out by using nitric acid at 120°C for 48 hours. The FTIR technique was used to characterize the surface of the modified carbon nanotubes to ascertain the

Muataz Ali Atieh

2011-01-01

5

Retention of heavy metals by carboxyl functional groups of biochars in small arms range soil.  

PubMed

Long-term effectiveness of biochar for heavy metal stabilization depends upon biochar's sorptive property and recalcitrance in soil. To understand the role of carboxyl functional groups on heavy metal stabilization, cottonseed hull biochar and flax shive steam-activated biochar having a low O/C ratio (0.04-0.06) and high fixed carbon content (~80% dry weight basis) were oxidized using concentrated H(2)SO(4)/HNO(3) and 30% HNO(3). Oxidized and unoxidized biochars were characterized for O/C ratio, total acidity, pH, moisture, ash, volatile matter, and fixed carbon contents, Brunauer-Emmett-Teller surface area, and attenuated total reflectance Fourier transform infrared spectral features. Characterized biochars were amended (2%, 5%, 10%, and 20% in grams of biochar per gram of soil) on a sandy, slightly acidic (pH 6.27) heavy metal contaminated small arms range soil fraction (<250 ?m) having low total organic carbon (0.518%) and low cation exchange capacity (0.95 cmol(c) kg(-1)). Oxidized biochars rich in carboxyl functional groups exhibited significantly greater Pb, Cu, and Zn stabilization ability compared to unoxidized biochars, especially in pH 4.9 acetate buffer (standard solution for the toxicity characteristic leaching procedure). Oppositely, only oxidized biochars caused desorption of Sb, indicating a counteracting impact of carboxyl functional groups on the solubility of anions and cations. The results suggested that appropriate selection of biochar oxidant will produce recalcitrant biochars rich in carboxyl functional groups for a long-term heavy metal stabilization strategy in contaminated soils. PMID:22280497

Uchimiya, Minori; Bannon, Desmond I; Wartelle, Lynda H

2012-02-22

6

Chemical Functionalization of Graphene Nanoribbons by Carboxyl Groups on Stone-Wales Defects  

Microsoft Academic Search

Using the density functional theory, we have demonstrated the chemical\\u000afunctionalization of semiconducting graphene nanoribbons (GNRs) with\\u000aStone-Wales (SW) defects by carboxyl (COOH) groups. It is found that the\\u000ageometrical structures and electronic properties of the GNRs changed\\u000asignificantly, and the electrical conductivity of the system could be\\u000aconsiderably enhanced by mono-adsorption and double-adsorption of COOH, which\\u000asensitively depends upon

Fangping OuYang; Bing Huang; Zuanyi Li; Hui Xu; Huanyou Wang

2008-01-01

7

Comprehensive study of mesoporous carbon functionalized with carboxylate groups and magnetic nanoparticles as a promising adsorbent.  

PubMed

Highly ordered mesoporous carbon functionalized with carboxylate groups and magnetic nanoparticles has been successfully synthesized. By oxidative treatment using (NH(4))(2)S(2)O(8) and H(2)SO(4) mixed solution, numerous hydrophilic groups were created in the mesopores without destroying the ordered mesostructure of CMK-3. Through the in situ reduction in Fe(3+), magnetic nanoparticles were successfully introduced into the mesopores, resulting in the multifunctional mesoporous carbon Fe-CMK-3. The obtained hybrid carbon material possesses ordered mesostructure, high Brunauer-Emmett-Teller (BET) surface area up to 1013 m(2)/g, large pore volume of about 1.16 cm(3)/g, carboxylic surface, and excellent magnetic property. When used as an adsorbent, Fe-CMK-3 exhibits excellent performances for removing toxic organic compounds from waster-water, with a high adsorption capacity, an extremely rapid adsorption rate, and an easy magnetically separable process. In the case of requiring emergency removal of large amount of organic pollutants in aqueous, the hybrid carbon adsorbent would be an ideal choice. PMID:22236608

Chi, Yue; Geng, Wangchang; Zhao, Liang; Yan, Xiao; Yuan, Qing; Li, Nan; Li, Xiaotian

2012-03-01

8

A rapid method for the assessment of the surface group density of carboxylic acid-functionalized polystyrene microparticles.  

PubMed

Particle-based assays are becoming versatile analytical tools due to their cost-effectiveness, speed, straightforward and diverse functionalization chemistries, especially when polystyrene particles are used. The introduction of functional groups (-COOH, -NH2, etc.) to the surface of such polystyrene particles promotes their application in bioanalytics. However, the traditional method to determine the amount of surface carboxylate groups is conductivity titration, which is usually time- and resources-consuming and discontinuous. Here, we synthesized polystyrene microparticles with different contents of carboxylate groups, and then investigated a simpler and potentially continuous approach to determine the amount of surface carboxylate groups by Zeta potential measurements. The results were compared to the traditional titration method and to actual coupling efficiencies of the functionalized particles with a model oligonucleotide probe as determined by flow cytometry. All quantification methods revealed good agreement. PMID:23531901

Zhu, Shengchao; Panne, Ulrich; Rurack, Knut

2013-05-21

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

Effect of Carboxylic Functional Group Functionalized on Carbon Nanotubes Surface on the Removal of Lead from Water  

PubMed Central

The adsorption mechanism of the removal of lead from water by using carboxylic functional group (COOH) functionalized on the surface of carbon nanotubes was investigated. Four independent variables including pH, CNTs dosage, contact time, and agitation speed were carried out to determine the influence of these parameters on the adsorption capacity of the lead from water. The morphology of the synthesized multiwall carbon nanotubes (MWCNTs) was characterized by using field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) in order to measure the diameter and the length of the CNTs. The diameters of the carbon nanotubes were varied from 20 to 40?nm with average diameter at 24?nm and 10 micrometer in length. Results of the study showed that 100% of lead was removed by using COOH-MCNTs at pH 7, 150?rpm, and 2 hours. These high removal efficiencies were likely attributed to the strong affinity of lead to the physical and chemical properties of the CNTs. The adsorption isotherms plots were well fitted with experimental data.

Atieh, Muataz Ali; Bakather, Omer Yehya; Al-Tawbini, Bassam; Bukhari, Alaadin A.; Abuilaiwi, Faraj Ahmad; Fettouhi, Mohamed B.

2010-01-01

11

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

2012-03-01

12

Cyclopentane-1,3-dione: a novel isostere for the carboxylic acid functional group. Application to the design of potent thromboxane (A2) receptor antagonists.  

PubMed

Cyclopentane-1,3-diones are known to exhibit pK(a) values typically in the range of carboxylic acids. To explore the potential of the cyclopentane-1,3-dione unit as a carboxylic acid isostere, the physical-chemical properties of representative congeners were examined and compared with similar derivatives bearing carboxylic acid or tetrazole residues. These studies suggest that cyclopentane-1,3-diones may effectively substitute for the carboxylic acid functional group. To demonstrate the use of the cyclopentane-1,3-dione isostere in drug design, derivatives of a known thromboxane A(2) prostanoid (TP) receptor antagonist, 3-(3-(2-(4-chlorophenylsulfonamido)ethyl)phenyl)propanoic acid (12), were synthesized and evaluated in both functional and radioligand-binding assays. A series of mono- and disubstituted cyclopentane-1,3-dione derivatives (41-45) were identified that exhibit nanomolar IC(50) and K(d) values similar to 12. Collectively, these studies demonstrate that the cyclopentane-1,3-dione moiety comprises a novel isostere of the carboxylic acid functional group. Given the combination of the relatively strong acidity, tunable lipophilicity, and versatility of the structure, the cyclopentane-1,3-dione moiety may constitute a valuable addition to the palette of carboxylic acid isosteres. PMID:21863799

Ballatore, Carlo; Soper, James H; Piscitelli, Francesco; James, Michael; Huang, Longchuan; Atasoylu, Onur; Huryn, Donna M; Trojanowski, John Q; Lee, Virginia M-Y; Brunden, Kurt R; Smith, Amos B

2011-10-13

13

Cyclopentane-1,3-dione: A Novel Isostere for the Carboxylic Acid Functional Group. Application to the Design of Potent Thromboxane (A2)-Receptor Antagonists  

PubMed Central

Cyclopentane-1,3-diones are known to exhibit pKa values typically in the range of carboxylic acids. To explore the potential of the cyclopentane-1,3-dione unit as a carboxylic acid isostere, the physical-chemical properties of representative congeners were examined and compared with similar derivatives bearing carboxylic acid or tetrazole residues. These studies suggested that cyclopentane-1,3-diones may effectively substitute for the carboxylic acid functional group. To demonstrate the use of the cyclopentane-1,3-dione isostere in drug-design, derivatives of a known thromboxane-A2 prostanoid (TP) receptor antagonist, 3-(3-(2-(4-chlorophenylsulfonamido)ethyl)-phenyl)propanoic acid (12), were synthesized and evaluated in both functional and radioligand-binding assays. A series of mono- and di-substituted cyclopentane-1,3-dione derivatives (41–45) were identified that exhibit nM IC50 and Kd values similar to 12. Collectively, these studies demonstrate that the cyclopentane-1,3-dione moiety comprises a novel isostere of the carboxylic acid functional group. Given the combination of the relatively strong acidity, tunable lipophilicity, and versatility of the structure, the cyclopentane-1,3-dione moiety may constitute a valuable addition to the palette of carboxylic acid isosteres.

Ballatore, Carlo; Soper, James; Piscitelli, Francesco; James, Michael; Huang, Longchuan; Atasoylu, Onur; Huryn, Donna M.; Trojanowski, John Q.; Lee, Virginia M.-Y.; Brunden, Kurt R.; Smith, Amos B.

2011-01-01

14

Electronic and optical response of Ru(II) complexes functionalized by methyl, carboxylate groups: joint theoretical and experimental study  

Microsoft Academic Search

New photovoltaic and photocatalysis applications have been recently proposed based on the hybrid Ru(II)-bipyridine-complex\\/semiconductor quantum dot systems. In order to attach the complex to the surface of a semiconductor, a linking bridge - a carboxyl group - is added to one or two of the 2,2-bipyridine ligands. Such changes in the ligand structure, indeed, affect electronic and optical properties and

Tretiak; Sergei

2008-01-01

15

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

2013-10-21

16

"Supersilyl" Group as Novel Carboxylic Acid Protecting Group: Application to Highly Stereoselective Aldol and Mannich Reactions  

PubMed Central

“Super Power”: The application of the "supersilyl” group as carboxylic acid protecting group has been investigated. The unique properties of the “supersilyl” group enabled it to outperform typical carboxyl protecting groups, conferring extraordinary protection upon the carboxyl functionality. “Supersilyl” esters were also utilized for the first time as stable carboxylic acid synthetic equivalents in highly stereoselective aldol and Mannich reactions. The value of this methodology has been further described by the easy photo-deprotection protocol and its applications in rapid synthesis of polyketide subunits.

Tan, Jiajing; Akakura, Matsujiro

2013-01-01

17

The role of carboxyl groups in the function of endo-beta-1,4-glucanase from Schizophyllum commune.  

PubMed

The endo-beta-1,4-glucanase from Schizophyllum commune was purified to homogeneity by a modified procedure that employed concanavalin A-Sepharose. The catalytic site of the enzyme has previously been proposed to consist of Glu-33 and Asp-50 that act in a manner analogous to lysozyme [Yaguchi, M., Roy, C., Rollin, C.F., Paice, M.G. & Jurasek, L. (1983) Biochem. Biophys. Res. Commun. 116, 408-411]. The role of carboxyl groups in the mechanism of action was delineated through kinetic and chemical modification studies. The rate of endoglucanase-catalysed hydrolysis of CM-cellulose was determined viscometrically at 30 degrees C, 0.06 M ionic strength and pH 2.5-9.0. The pH profile for maximum velocity gave the kinetic apparent pK values 3.8 and 6.6 and for initial velocity the pK values 3.7 and 6.1. Treatment of the endoglucanase with diethylpyrocarbonate resulted in the modification of all the four histidyl residues present in the enzyme with the retention of 95% of the original enzymatic activity. A water-soluble carbodiimide completely inactivated the cellulase and kinetic analysis indicated that at least one molecule of carbodiimide binds to the enzyme for inactivation. The pH dependence of the inactivation is consistent with the modification of carboxyl groups. The binding of an inhibitor, cellobiose, prior to carbodiimide modification protected the enzyme from rapid inactivation. Titration of the enzyme with dithiobis(2-nitrobenzoic acid) indicated the absence of free thiol groups. Reaction of the endoglucanase with tetranitromethane resulted in the modification of six of the fourteen tyrosyl residues of the enzyme with approximately 35% diminution in activity. PMID:4039663

Clarke, A J; Yaguchi, M

1985-06-01

18

Siloxyl ether functionalized resins for chemoselective enrichment of carboxylic acids.  

PubMed

Although the carboxylic acid moiety is prevalent in many biologically produced molecules, including natural products and proteins, methods to chemoselectively target this functional group have remained elusive. Generally, strategies that utilize carboxylate nucleophilicity also promote reactions with other nucleophiles such as amines and hydroxyls. A reagent was sought to facilitate the selective isolation of carboxylic acid containing compounds from complex mixtures. Here, the development of siloxyl ether functionalized solid supports is described. PMID:21957886

Trader, Darci J; Carlson, Erin E

2011-10-21

19

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

20

Ethane-bridged periodic mesoporous organosilicas functionalized with high loadings of carboxylic acid groups: synthesis, bifunctionalization, and fabrication of metal nanoparticles.  

PubMed

Well-ordered periodic mesoporous organosilicas (PMOs) functionalized with high contents of carboxylic acid (?COOH) groups, up to 85?mol?% based on silica, were synthesized by co-condensation of 1,2-bis(triethoxysilyl)ethane (BTEE) and carboxyethylsilanetriol sodium salt (CES) under acidic conditions by using alkyl poly(oxyethylene) surfactant Brij?76 as a structure-directing agent. A variety of techniques including powder X-ray diffraction (XRD), nitrogen adsorption/desorption, Fourier-transformed infrared (FTIR), transmission electron microscopy (TEM), (13) C- and (29) Si solid-state nuclear magnetic resonance (NMR) were used to characterize the products. The materials thus obtained were used as an effective support to synthesize metal nanoparticles (Ag and Pt) within the channel of 2D hexagonal mesostructure of PMOs. The size and distribution of the nanoparticles were observed to be highly dependent on the interaction between the carboxylic acid functionalized group and the metal precursors. The size of Pt nanoparticles reduced from 3.6 to 2.5?nm and that of Ag nanoparticles reduced from 5.3 to 3.4?nm with the increase in the ?COOH loading from 10 to 50?%. PMID:24338957

Deka, Juti Rani; Kao, Hsien-Ming; Huang, Shu-Ying; Chang, Wei-Chieh; Ting, Chun-Chiang; Rath, Purna Chandra; Chen, Ching-Shiun

2014-01-13

21

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

2013-11-01

22

Isotherm, thermodynamic, kinetics, and adsorption mechanism studies of Ethidium bromide by single-walled carbon nanotube and carboxylate group functionalized single-walled carbon nanotube.  

PubMed

The studies of kinetics and thermodynamics of adsorption of Ethidium bromide in aqueous solutions on single-walled carbon nanotube (SWCNT) and carboxylate group functionalized single-walled carbon nanotube (SWCNT-COOH) surfaces were by UV-Vis spectroscopy. The adsorption kinetics for SWCNT-COOH and SWCNTs were well described by a intra-particle diffusion model, while Langmuir, Freundlich, Harkins-Jura, and Halsey isotherms described the adsorption isotherms, and the adsorption thermodynamic parameters of equilibrium constant (K0), standard free energy (?G0), standard enthalpy (?H0), and standard entropy changes (?S0) were measured. The maximum surface coverage for SWCNTs is 36.10% and for SWCNT-COOH is 38.42%. The values of ?H0 and ?G0 suggested that the adsorption of EtBr on SWCNT-COOH and SWCNTs was endothermic and spontaneous. The adsorption of EtBr on SWCNT-COOH is more than SWCNTs surfaces. PMID:23261335

Moradi, Omid; Fakhri, Ali; Adami, Saeideh; Adami, Sepideh

2013-04-01

23

Effect of chemical modification of carboxyl groups in apple residues on metal ion binding  

Microsoft Academic Search

AR (apple residue) was used as an alternative and cheap material for binding metal ions due to the presence of carboxyl and\\u000a phenolic functional groups. The binding capacity of copper, lead, and cadmium by AR was pH dependent. Carboxyl groups of AR\\u000a were esterified by acidic methanol to determine the contribution of carboxyl groups to metal ions binding. The extent

Sung Ho Lee; Jong Sik Shon; Hongsuk Chung; Moo-Yeal Lee; Ji-Won Yang

1999-01-01

24

Hybrid nanoparticles for drug delivery and bioimaging: mesoporous silica nanoparticles functionalized with carboxyl groups and a near-infrared fluorescent dye.  

PubMed

The development of a drug delivery system with fluorescent biolabels is important in anti-cancer drug delivery application due to the potential for simultaneous diagnosis and treatment of diseases. Here, we reported the synthesis and multiple functionalization of mesoporous silica nanoparticle (MSN) for bioimaging and controlled drug release. After the functionalization with carboxyl group, the nanoparticles exhibited much better dispersity and stability in aqueous solution than MSN. Furthermore, a substantial doxorubicin (DOX) loading level was achieved and DOX-loaded nanoparticles exhibited noticeable pH-sensitive behavior with accelerated release of DOX in acidic environment. Compared with native DOX-MSN, DOX-MSN/COOH-Cy5 exhibited enhanced intracellular uptake efficacy and stronger effect on killing tumor cells. Meanwhile, it was observed that the MSN/COOH-Cy5 was able to locate in the cytoplasm of MCF-7 cells and could accumulate in tumor tissues for a long period of time. Overall, the functional nanoparticle could potentially be used for simultaneous controlled drug release and near-infrared fluorescent bioimaging. PMID:23394807

Xie, Meng; Shi, Hui; Ma, Kun; Shen, Haijun; Li, Bo; Shen, Song; Wang, Xinshi; Jin, Yi

2013-04-01

25

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

26

Electrochemical recognition and trace-level detection of bactericide carbendazim using carboxylic group functionalized poly(3,4-ethylenedioxythiophene) mimic electrode.  

PubMed

The electrochemical recognition and trace-level detection of bactericide carbendazim (MBC) in paddy water and commercial juice were realized using carboxylic group functionalized poly(3,4-ethylenedioxythiophene) (PC4-EDOT-COOH) film electrode. PC4-EDOT-COOH film was prepared by one step, low-cost, and green electrosynthesis in aqueous microemulsion system and characterized by FT-IR, cyclic voltammetry, UV-vis and SEM. In comparison with poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(hydroxymethylated-3,4-ethylenedioxylthiophene) (PEDTM), PC4-EDOT-COOH exhibited the best electrochemical recognition towards MBC and the recognition mechanism was proved by quantitative calculation. Sensing parameters such as pH values, accumulation potential, accumulation time, supporting electrolyte, and scan rate on the current response of MBC were discussed. In addition, the sensor can be applied to quantification of MBC in the concentration range of 0.012-0.35?M with a low detection limit of 3.5nM (S/N=3). Moreover, PC4-EDOT-COOH film electrode showed good stability, high selectivity, and satisfactory anti-interference ability. Satisfactory results indicated that PC4-EDOT-COOH film is a promising sensing platform for the trace-level analysis of bactericide residue carbendazim in agricultural crops and environment. PMID:24861970

Yao, Yuanyuan; Wen, Yangping; Zhang, Long; Wang, Zifei; Zhang, Hui; Xu, Jingkun

2014-06-11

27

A spin-crossover complex based on a 2,6-bis(pyrazol-1-yl)pyridine (1-bpp) ligand functionalized with a carboxylate group.  

PubMed

Combining Fe(ii) with the carboxylate-functionalized 2,6-bis(pyrazol-1-yl)pyridine (bppCOOH) ligand results in the spin-crossover compound [Fe(bppCOOH)2](ClO4)2 which shows an abrupt spin transition with a T1/2 of ca. 380 K and a TLIESST of 60 K due to the presence of a hydrogen-bonded linear network of complexes. PMID:24804875

Abhervé, Alexandre; Clemente-León, Miguel; Coronado, Eugenio; Gómez-García, Carlos J; López-Jordà, Maurici

2014-06-01

28

Carboxyl groups and the proton pump of bacteriorhodopsin  

SciTech Connect

Chemical modification and spin-labeled studies of purple membranes isolated from Halobacterium halobium have provided the first evidence for buried carboxyl residues within the hydrophobic, membrane-protein domains. Spin label data showed that modification of buried carboxyl residues resulted in loss of protein activity. A pH-sensitive, chromophoric reporter group demostrated that a carboxyl residue in a hydrophobic membrane environment interacts with the retinal chromophore of bacteriorhodopsin. These results appear consistent with the idea that carboxyl residues in hydrophobic environments may be a general feature required for activity of membrane proton pumps.

Herz, J.M.; Packer, L.

1983-08-01

29

Multi-walled carbon nanotubes functionalized by carboxylic groups: Activation of TiO 2 (anatase) and phosphate olivines (LiMnPO 4; LiFePO 4) for electrochemical Li-storage  

Microsoft Academic Search

Multi-walled carbon nanotubes functionalized by carboxylic groups, exhibit better affinity towards TiO2 (P90, Degussa) as compared to that of pristine nanotubes. Also the electrochemical performance of TiO2 is improved by nanotube networking, but the Li-storage capacity of TiO2 is unchanged. Whereas the composite of TiO2 with non-functionalized nanotubes demonstrates simple superposition of the behavior of pure components, the composite with

Ladislav Kavan; Revathi Bacsa; Meltem Tunckol; Philippe Serp; Shaik M. Zakeeruddin; Florian Le Formal; Marketa Zukalova; Michael Graetzel

2010-01-01

30

Characterization and diagenesis of strong-acid carboxyl groups in humic substances  

USGS Publications Warehouse

A small fraction of carboxylic acid functional groups in humic substances are exceptionally acidic with pKa values as low as 0.5. A review of acid-group theory eliminated most models and explanations for these exceptionally acidic carboxyl groups. These acidic carboxyl groups in Suwannee River fulvic acid were enriched by a 2-stage fractionation process and the fractions were characterized by elemental, molecular-weight, and titrimetric analyses, and by infrared and 13C- and 1H-nuclear magnetic resonance spectrometry. An average structural model of the most acidic fraction derived from the characterization data indicated a high density of carboxyl groups clustered on oxygen-heterocycle alicyclic rings. Intramolecular H-bonding between adjacent carboxyl groups in these ring structures enhanced stabilization of the carboxylate anion which results in low pKa1 values. The standard, tetrahydrofuran tetracarboxylic acid, was shown to have similar acidity characteristics to the highly acidic fulvic acid fraction. The end products of 3 known diagenetic pathways for the formation of humic substances were shown to result in carboxyl groups clustered on oxygen-heterocycle alicyclic rings.

Leenheer, J. A.; Wershaw, R. L.; Brown, G. K.; Reddy, M. M.

2003-01-01

31

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

32

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

2013-09-01

33

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

2012-12-18

34

Conjugation of enzyme on superparamagnetic nanogels covered with carboxyl groups  

Microsoft Academic Search

?-Chymotrypsin (CT) as model enzyme was conjugated onto the novel carboxyl-functionalized superparamagnetic nanogels, prepared via facile photochemical in situ polymerization, by using 1-ethyl-3-(3-dimethylaminepropyl) carbodiimide (EDC) as coupling reagent. The obtained magnetic immobilized enzyme was characterized by use of photo correlation spectroscopy (PCS), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) measurement, thermogravimetric (TG) analysis and vibrating sample magnetometer (VSM) measurement.

Jun Hong; Dongmei Xu; Peijun Gong; Hongjuan Ma; Li Dong; Side Yao

2007-01-01

35

Synthesis of Functionalized Dialkyl Ketones From Carboxylic Acid Derivatives and Alkyl Halides  

PubMed Central

Unsymmetrical dialkyl ketones can be directly prepared by the nickel-catalyzed reductive coupling of carboxylic acid chlorides or (2-pyridyl)thioesters with alkyl iodides or benzylic chlorides. A wide variety of functional groups are tolerated by this process, including common nitrogen protecting groups and C-B bonds. Even hindered ketones flanked by tertiary and secondary centers can be formed. The mechanism is proposed to involve the reaction of a (L)Ni(alkyl)2 intermediate with the carboxylic acid derivative.

Wotal, Alexander C.; Weix, Daniel J.

2012-01-01

36

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

37

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

38

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

39

Functionalized carboxyl nanoparticles enhance mucus dispersion and hydration  

PubMed Central

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

40

Deprotonation energies of a model fulvic acid. I. Carboxylic acid groups  

NASA Astrophysics Data System (ADS)

A model Suwannee fulvic acid (SFA [Leenheer, J.A., 1994. In: Baker, L.A. (Ed.), Chemistry of Dissolved Organic Matter in Rivers, Lakes and Reservoirs. Advances in Chemistry Series, vol. 237. American Chemical Society]) was energy minimized in various deprotonation states using semi-empirical methods. The structures were minimized in the isolated SFA phase and SFA with 60 water molecules to mimic the first solvation sphere. The relative energies of deprotonation were calculated at four carboxylic acid sites with Hartree-Fock (HF/6-31G(d)) and density functional theory (B3LYP/6-31G(d)) methods. Comparisons were made between the theoretical methods and states of solvation. Isolated and solvated models resulted in different relative deprotonation orders. The energy changes calculated for removing a H + from a given carboxylic acid group as a function of overall model molecule charge are large enough to explain the large variations of carboxyl group p Kas in dissolved natural organic matter. Analysis of the SFA structure as a function of molecular charge is also discussed.

Trout, Chad C.; Kubicki, James D.

2006-01-01

41

Carboxylate-functionalized phosphomolybdates: ligand-directed conformations.  

PubMed

The [HPMo6O21](2-) units and carboxylate linkers can be combined to build novel polyanions by a carefully designed complementary system in self-assembly processes depending only on the number of carboxyl groups and the nature of carboxylic acids. Complexes (NH4)5[HPMo6O21(O2CC6H4OH)3]·4H2O (1), (NH4)8H2[(HPMo6O21)2(C2O4)3]·13H2O (2), (NH4)20[(HPMo6O21)4(O2CCH2CO2)6]·17H2O (3), and Cs2(NH4)10[(HPMo6O21)2(HPO3){C6H3(CO2)3}2]·5H2O (4) have been synthesized by a simple one-pot reaction of (NH4)6Mo7O24·4H2O, H3PO3, and carboxylic acid ligands in aqueous solution. Formation of these compounds is critically dependent on the identifying carboxylic acids, which play the important templated role in assembly processes. The stability of these clusters was explored using electrospray ionization mass spectrometry (ESI-MS) and (31)P NMR spectroscopy, and electron paramagnetic resonance (EPR) experiments further demonstrated the result of the interesting photochromic property. PMID:23844943

Yang, Donghui; Li, Suzhi; Ma, Pengtao; Wang, Jingping; Niu, Jingyang

2013-08-01

42

Synthesis of functionalized dialkyl ketones from carboxylic acid derivatives and alkyl halides.  

PubMed

Unsymmetrical dialkyl ketones can be directly prepared by the nickel-catalyzed reductive coupling of carboxylic acid chlorides or (2-pyridyl)thioesters with alkyl iodides or benzylic chlorides. A wide variety of functional groups are tolerated by this process, including common nitrogen protecting groups and C-B bonds. Even hindered ketones flanked by tertiary and secondary centers can be formed. The mechanism is proposed to involve the reaction of a (L)Ni(alkyl)(2) intermediate with the carboxylic acid derivative. PMID:22360350

Wotal, Alexander C; Weix, Daniel J

2012-03-16

43

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

44

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

45

Pancreatic Function in Carboxyl-Ester Lipase Knockout Mice  

Microsoft Academic Search

Background\\/Aims:CEL-MODY is a monogenic form of diabetes and exocrine pancreatic insufficiency due to mutations in the carboxyl-ester lipase (CEL) gene. We aimed to investigate endocrine and exocrine pancreatic function in CEL knockout mice (CELKO). Methods: A knockout mouse model with global targeted deletion of CEL was investigated physiologically and histopathologically, and compared to littermate control CEL+\\/+ mice at 7 and

Mette Vesterhus; Helge Ræder; Amarnath J. Kurpad; Dan Kawamori; Anders Molven; Rohit N. Kulkarni; C. Ronald Kahn; Pål Rasmus Njølstad

2010-01-01

46

Preparation and characterization of TEMPO-oxidized cellulose nanofibril films with free carboxyl groups  

Microsoft Academic Search

A 2,2,6,6-tetramehylpiperidine-1-oxy radical (TEMPO)-oxidized wood cellulose with sodium carboxylate groups was completely converted to individual TEMPO-oxidized cellulose nanofibrils with free carboxyl groups (TOCN-COOH) dispersed in water at pH 4.6. Self-standing films prepared by casting and drying of the TOCN-COOH\\/water dispersion were flexible and highly transparent. Fourier transform infrared (FT-IR) spectra and sodium content determination confirmed that the sodium carboxylate groups

Shuji Fujisawa; Yusuke Okita; Hayaka Fukuzumi; Tsuguyuki Saito; Akira Isogai

2011-01-01

47

Assignment of function to histidines 260 and 298 by engineering the E1 component of the Escherichia coli 2-oxoglutarate dehydrogenase complex; substitutions that lead to acceptance of substrates lacking the 5-carboxyl group.  

PubMed

The first component (E1o) of the Escherichia coli 2-oxoglutarate dehydrogenase complex (OGDHc) was engineered to accept substrates lacking the 5-carboxylate group by subjecting H260 and H298 to saturation mutagenesis. Apparently, H260 is required for substrate recognition, but H298 could be replaced with hydrophobic residues of similar molecular volume. To interrogate whether the second component would allow synthesis of acyl-coenzyme A derivatives, hybrid complexes consisting of recombinant components of OGDHc (o) and pyruvate dehydrogenase (p) enzymes were constructed, suggesting that a different component is the "gatekeeper" for specificity for these two multienzyme complexes in bacteria, E1p for pyruvate but E2o for 2-oxoglutarate. PMID:21809826

Shim, Da Jeong; Nemeria, Natalia S; Balakrishnan, Anand; Patel, Hetalben; Song, Jaeyoung; Wang, Junjie; Jordan, Frank; Farinas, Edgardo T

2011-09-01

48

In vitro thrombogenicity investigation of new water-dispersible polyurethane anionomers bearing carboxylate groups.  

PubMed

New segmented polyurethane (PU) anionomers based on hydroxytelechelic polybutadiene were synthesized via an aqueous dispersion process. Incorporation of carboxylic groups was achieved using thioacids of different length. Surface properties were investigated by mean of water absorption analysis and static contact-angle measurements using water, diiodomethane, formamide and ethylene glycol. Blood compatibility of the PUs was evaluated by in vitro adhesion assays using 111In-radiolabeled platelet-rich plasma and [125I]fibrinogen. Morphology of the adhered platelets was examined by scanning electron microscopy (SEM). Results were compared to two biomedical-grade PUs, namely Pellethane and Tecoflex. Insertion of carboxylic groups increased surface hydrophilicity and limited water uptake ( < 8% for an ion content of 5% by weight). Surface energy of all synthesized PUs was between 40 and 45 mJ/m2. Platelet adhesion and fibrinogen adsorption on the PU anionomer surfaces were affected as a function to the increase of graft length; thiopropionic was the most haemocompatible, followed by thiosuccinic and then thioglycolic acid. SEM analyses of all ionic PU samples exhibited low platelet adhesion to surfaces with no morphological modification. In conclusion, increased hydrophily, dynamic mobility and charge repulsion are synergistic key factors for enhanced haemocompatibility. PMID:15850288

Poussard, L; Burel, F; Couvercelle, J-P; Lesouhaitier, O; Merhi, Y; Tabrizian, M; Bunel, C

2005-01-01

49

Hypermodified nucleoside carboxyl group as a target site for specific tRNA modification.  

PubMed

The free carboxyl group of hypermodified nucleosides N6-methyl-N6-(threoninocarbonyl)adenosine (mt6A37) and 3-(3-amino-3-carboxypropyl)uridine (acp3U20:1) in tRNAmMet (yellow lupine), and N6-(threoninocarbonyl)adenosine (t6A37) in tRNAiMet (yellow lupine) can be converted quantitatively and under very mild conditions into the respective anilides in a reaction with aniline and a water-soluble carbodiimide. The tRNA reactions proceed with rates very similar to that reported previously for t6A nucleoside. Detailed analysis of the products of tRNA modification with [3H]aniline on tRNA (chromatography on BD-DEAE-cellulose), oligonucleotide (polyacrylamide gel electrophoresis) and nucleoside (HPLC on Aminex A6) levels clearly indicates that only the hypermodified nucleoside residues undergo the reaction. The site of modification is confirmed for mono-modified (at mt6A37) and bis-modified (at mt6A37 and acp3U20:1) tRNAmMet, and for mono-modified (at t6A37) tRNAiMet by sequence analysis using 5'end 32P-labeled tRNAs. The modification procedure seems to be universally applicable for all hypermodified nucleosides bearing a free carboxyl group and for different amine reagents designed for the studies on tRNA function. PMID:3956493

Górnicki, P; Judek, M; Wola?ski, A; Krzyzosiak, W J

1986-03-01

50

Polyacetal Carboxylic Acids: a New Group of Antiviral Polyanions  

PubMed Central

Chlorite-oxidized oxypolysaccharides are polyacetal carboxylic acids. They inhibited the cytopathic effect of vesicular stomatitis virus in mouse embryo cell cultures challenged at low input multiplicity. After intraperitoneal injection of these compounds in mice, interferon appeared in the circulation. The compounds also protected mice against lethal mengovirus infection and against the development of experimental pox lesions on the tail. Chlorite-oxidized oxyamylose was antiviral only when at least 64% of the glucopyranose units were oxidized, an observation which suggested a correlation between charge density and antiviral effect. The antiviral activity was also influenced by the molecular weight, as demonstrated by the fact that chlorite-oxidized dextrans which had a high intrinsic viscosity were more active than those with low intrinsic viscosity.

Claes, P.; Billiau, A.; De Clercq, E.; Desmyter, J.; Schonne, E.; Vanderhaeghe, H.; De Somer, P.

1970-01-01

51

Controlled electrochemical carboxylation of graphene to create a versatile chemical platform for further functionalization.  

PubMed

An electrochemical approach is introduced for the versatile carboxylation of multi-layered graphene in 0.1 M Bu4NBF4/MeCN. First, the graphene substrate (i.e., graphene chemically vapor-deposited on Ni) is negatively charged at -1.9 V versus Ag/AgI in a degassed solution to allow for intercalation of Bu4N(+) and, thereby, separation of the individual graphene sheets. In the next step, the strongly activated and nucleophilic graphene is allowed to react with added carbon dioxide in an addition reaction, introducing carboxylate groups stabilized by Bu4N(+) already present. This procedure may be carried out repetitively to further enhance the carboxylation degree under controlled conditions. Encouragingly, the same degree of control is even attainable, if the intercalation and carboxylation is carried out simultaneously in a one-step procedure, consisting of simply electrolyzing in a CO2-saturated solution at the graphene electrode for a given time. The same functionalization degree is obtained for all multi-layered regions, independent of the number of graphene sheets, which is due to the fact that the entire graphene structure is opened in response to the intercalation of Bu4N(+). Hence, this electrochemical method offers a versatile procedure to make all graphene sheets in a multi-layered but expanded structure accessible for functionalization. On a more general level, this approach will provide a versatile way of forming new hybrid materials based on intimate bond coupling to graphene via carboxylate groups. PMID:24852930

Bjerglund, Emil; Kongsfelt, Mikkel; Shimizu, Kyoko; Jensen, Bjarke Bror Egede; Koefoed, Line; Ceccato, Marcel; Skrydstrup, Troels; Pedersen, Steen U; Daasbjerg, Kim

2014-06-10

52

Zinc(II) Complexes with Dangling Functional Organic Groups  

PubMed Central

Abstract Zinc(II) complexes with dangling functional organic groups were synthesized by reaction of zinc acetate with a series of bifunctional p-substituted benzene derivatives (a combination of carboxylate, oximate, amino, ?-ketoimine, and salicylaldime groups). Selective coordination to carboxylate groups was observed when the second functional group was an oxime or ?-ketoimine group. When the second group was an amine or salicylaldimine moiety, these groups were additionally coordinated. From the reaction with p-aminobenzoic acid, the compound [Zn2(OOCCH3)(OOC–C6H4–NH2)3]? was crystallized. It is a three-dimensional coordination polymer with bridging aminobenzoate ligands.

Yang, Jingxia; Puchberger, Michael; Qian, Renzhe; Maurer, Christian; Schubert, Ulrich

2012-01-01

53

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

54

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

55

Pancreatic Function in Carboxyl-Ester Lipase Knockout Mice  

PubMed Central

Background/Aims CEL-MODY is a monogenic form of diabetes and exocrine pancreatic insufficiency due to mutations in the carboxyl-ester lipase (CEL) gene. We aimed to investigate endocrine and exocrine pancreatic function in CEL knockout mice (CELKO). Methods A knockout mouse model with global targeted deletion of CEL was investigated physiologically and histopathologically, and compared to littermate control CEL+/+ mice at 7 and 12 months on normal chow and high-fat diets (HFD), i.e. 42 and 60% fat by calories. Results CELKO+/+ and –/– mice showed normal growth and development and normal glucose metabolism on a chow diet. Female CEL–/– mice on 60% HFD, on the other hand, had increased random blood glucose compared to littermate controls (p = 0.02), and this was accompanied by a reduction in glucose tolerance that did not reach statistical significance. In these mice there was also islet hyperplasia, however, ?- and ?-islet cells appeared morphologically normal and pancreatic exocrine function was also normal. Conclusion Although we observed mild glucose intolerance in female mice with whole-body knockout of CEL, the full phenotype of human CEL-MODY was not reproduced, suggesting that the pathogenic mechanisms involved are more complex than a simple loss of CEL function.

Vesterhus, Mette; Raeder, Helge; Kurpad, Amarnath J.; Kawamori, Dan; Molven, Anders; Kulkarni, Rohit N.; Kahn, C. Ronald; Nj?lstad, Pal Rasmus

2010-01-01

56

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

57

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, T. L.; Zachos, C. K. (High Energy Physics); (Univ. of Miami)

2011-03-16

58

Surface functional groups on acid-activated nutshell carbons  

Microsoft Academic Search

Nutshells from agriculturally important nut crops (almond, black walnut, English walnut, macadamia nut and pecan) were converted to granular activated carbon using phosphoric acid activation in nitrogen or air. Surface functional groups (carbonyl, phenols, lactones, carboxyl) were quantified by titration with bases of different ionization potential. The degree of copper uptake was correlated with the presence of various functional groups

Christopher A. Toles; Wayne E. Marshall; Mitchell M. Johns

1999-01-01

59

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

60

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

2008-11-01

61

Silylesterification of oxidized multi-wall carbon nanotubes by catalyzed dehydrogenative cross-coupling between carboxylic and hydrosilane functions  

NASA Astrophysics Data System (ADS)

Surface modification of oxidized carbon nanotubes (O-CNTs) with silicon based anchoring groups (R-SiR3) is a relatively uncommon approach of the CNTs functionalization. Hydrosilane derivatives constitute an attractive subclass of compounds for silanization reactions on the CNTs surface. In this work, we report on the ZnCl2 catalytically controlled reaction (hydrosilane dehydrogenative cross-coupling, DHCC) of fluorinated hydrosilane probes with the carboxylic functions present on the surface of oxidized multi-wall carbon nanotubes. Carbon nanotubes functionalized with essentially alcohol groups are also used to compare the selectivity of zinc chloride toward carboxylic groups. To assess the efficiency of functionalization, X-ray Photoelectron Spectroscopy is used to determine the qualitative and quantitative composition of the different samples. Solubility tests on the oxidized and silanized MWNTs are also carried out in the framework of the Hansen Solubility Parameters (HSP) theory to apprehend at another scale the effect of DHCC.

Seffer, J.-F.; Detriche, S.; Nagy, J. B.; Delhalle, J.; Mekhalif, Z.

2014-06-01

62

Esterification of the carboxyl groups in fibrinogen by the application of a highly specific methylating agent.  

PubMed

The trimethyl oxonium ion specifically modified the free carboxyl groups of fibrinogen. This esterification process resulted in the polymerization of the modified fibrinogen molecule with the production of a polymeric material that resembled the physiologically formed fibrin clot. The extent of methylation of fibrinogen was evaluated by methoxyl determination at each step of the polymerization process. The modified fibrinogen polymerized in approximately ten min with a minimum number of methyl groups being incorporated into the fibrinogen molecule. In this manner, it was shown that modification of carboxyl groups in the fibrinogen by a group-specific methylating agent results in polymerization of fibrinogen. The sites of methylation were ascertained by chromatographic analysis which resulted in the identification of beta-methyl aspartic acid and gamma-methyl glutamic acid derivatives of the fibrinogen. The analytical methods applied were not able to detect the methylation of any additional amino acid residues in the polymerized-methylated fibrinogen. Based on this experimental data, it was formulated that the methylation of fibrinogen involved the esterification of the carboxyl groups of aspartic and glutamic acid with the resultant reduction of negative repulsion between the fibrinogen molecules and thereby culminated in the polymerization of the modified fibrinogen. PMID:6129716

Osbahr, A J

1982-10-29

63

Nonlinear-optical properties of ?-diiminedithiolatonickel(II) complexes enhanced by electron-withdrawing carboxyl groups.  

PubMed

We report the synthesis, characterization, nonlinear-optical (NLO) properties, and density functional theory (DFT) calculations for three nickel diiminedithiolate complexes [Ni(4,4'-R2carboxy-bpy)(L)] [R = methyl, L = 1,2-benzenedithiolate (bdt), 1; R = ethyl, L = 5,6-dihydro-1,4-dithine-2,3-dithiolate (dddt), 2; R = ethyl, L = 1-(N-methylindol-5-yl)ethene-1,2-dithiolate (mi-5edt), 3]. The crystal structure of 1 shows a square-planar coordination for the nickel ion and bond distances consistent with a diiminedithiolate description for the complex. For all complexes, the cyclic voltammetry measurements show two reversible reduction processes (-1.353/-1.380 V and -0798/-0.830 V, respectively) and an anodic wave (+0.372/+0.601 V). The UV-vis spectra present a band around 600-700 nm (? = 4880-6000 dm(3) mol(-1) cm(-1)) mainly attributed to a charge-transfer highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) transition, which shows a large negative solvatochromic shift, characteristic of push-pull complexes, and is responsible for the NLO properties of these molecules. The charge-transfer character of this electronic transition is confirmed by DFT calculations, with the HOMO mainly centered on the dithiolate moiety and the LUMO on the bpy ligand, with important contribution given by the carboxyl groups (?13%). Small contributions from the nickel(II) ion are present in both of the frontier orbitals. The carboxyl groups enhance the optical properties of this class of complexes, confirmed by comparison with the corresponding unsubstituted compounds. The second-order NLO properties have been measured by an electric-field-induced second-harmonic-generation technique using a 10(-3) M solution in N,N-dimethylformamide and working with a 1.907 ?m incident wavelength, giving for ??1.907 (??0) values of -1095 (-581), -2760 (-954), and -1650 (-618) × 10(-48) esu for 1-3, respectively. These values are among the highest in the class of square-planar push-pull complexes, similar to those found for dithionedithiolate compounds. Moreover, spectroelectrochemical experiments demonstrate the possibility of using these complexes as redox-switchable NLO chromophores. PMID:24762131

Pilia, Luca; Pizzotti, Maddalena; Tessore, Francesca; Robertson, Neil

2014-05-01

64

Synthesis and chemosensory application of water-soluble polyfluorenes containing carboxylated groups.  

PubMed

Detection of metal ions in aqueous solutions is a major issue for environmental protection. Conjugated polyelectrolytes showing high sensitivity and selectivity towards the detection of metal ions are highly desirable. We report a water-soluble polyfluorene containing carboxylated groups (P1), poly[9,9'-bis(3''-propanoate)fluoren-2,7-yl] sodium salt, which shows high recognition capability toward Cu(+) and Cu(2+). P1 was prepared via the hydrolysis of poly[9,9'-bis(tert-butyl-3''-propanoate)fluoren-2,7-yl] (P0) which was synthesized by Suzuki coupling polymerization. The photoluminescence (PL) spectra of P1 in aqueous solution are significantly quenched in the presence of Cu(+) and Cu(2+). P1 shows high selectivity and sensitivity toward Cu(+) and Cu(2+), with the Stern-Volmer constants (Ksv) being 3.5 × 10(6) and 5.78 × 10(6) M(-1), respectively. Moreover, the stoichiometric ratio of the P1 repeat unit to Cu(+) or Cu(2+) is 2?:?1 obtained from Job's plot. P1 maintains high selectivity towards Cu(+) or Cu(2+) in the presence of various metal cations. Our results demonstrate that P1 shows very high sensitivity and selectivity in recognizing Cu(+) and Cu(2+), indicating that it is a promising functional material for chemical sensors. PMID:24965116

Wu, Chia-Shing; Su, Hsiao-Chu; Chen, Yun

2014-08-14

65

Preparation and self-assembly of carboxylic acid-functionalized silica  

Microsoft Academic Search

A simple method for the fabrication of silica nanoparticle film based on the covalent-bonding interaction between carboxylic acid-functionalized silica nanoparticles (SiO2–COOH) and amino-terminated silicon wafer was developed. Prior to assembly, silica nanoparticles with an average diameter 80 nm were prepared using the Stöber method, amino-functionalized silica nanoparticles (SiO2–NH2) were prepared by a silanization with 3-aminopropyltriethoxysilane (APTES), while carboxylic acid-functionalized silica

Yanqing An; Miao Chen; Qunji Xue; Weimin Liu

2007-01-01

66

One-step preparation and pH-tunable self-aggregation of amphoteric aliphatic polycarbonates bearing plenty of amine and carboxyl groups.  

PubMed

This paper reports a novel amphoteric aliphatic polycarbonate bearing both amine and carboxyl groups. In the absence of protection-deprotection chemistry, the multi-functionalized copolymer is synthesized by one-step enzymatic copolymerization. The influences of the reaction conditions including monomer feed ratio and polymerization time are explored. The simultaneous incorporation of amine and carboxyl functionalities provides the copolymer with a pH-tunable self-aggregation feature, leading to various aggregation states including precipitated agglomerate, well-dispersed positively or negatively charged nanoparticles in a controlled manner. The copolymer displays minimal cytotoxicity to 293T and HeLa cells. PMID:23076737

Wang, Hua-Fen; Jia, Hui-Zhen; Zhu, Jing-Yi; Chu, Yan-Feng; Feng, Jun; Zhang, Xian-Zheng; Zhuo, Ren-Xi

2012-12-01

67

Preferential Interaction of Na+ over K+ to Carboxylate-functionalized Silver Nanoparticles  

EPA Science Inventory

Elucidating mechanistic interactions between specific ions (Na+/ K+) and nanoparticle surfaces to alter particle stability in polar media has received little attention. We investigated relative preferential binding of Na+ and K+ to carboxylate-functionalized silver nanoparticles ...

68

Hybrid materials prepared by interlayer functionalization of kaolinite with pyridine-carboxylic acids.  

PubMed

This paper presents the results of the functionalization of Brazilian São Simão kaolinite with pyridine-2-carboxylic and pyridine-2,6-dicarboxylic acids. The functionalization involved refluxing of the pyridine-carboxylic acid in the presence of kaolinite previously intercalated with dimethyl sulfoxide; both acids effectively displaced dimethyl sulfoxide from the clay interlayer. The resulting materials were characterized by X-ray diffraction, thermal analysis, infrared absorption spectroscopy, and C and N elemental analysis. The X-ray diffractograms revealed the incorporation of the acid molecules into the interlayer space of kaolinite. The thermogravimetric curves of the kaolinite samples functionalized with the pyridine-carboxylic acids indicated that the materials were thermally stable up to 300 degrees C. The displacements of the bands due to interlayer hydroxyls in the infrared absorption spectra also confirmed the functionalization of the kaolinite with the pyridine-carboxylic acids. PMID:19433329

de Faria, Emerson H; Lima, Omar J; Ciuffi, Katia J; Nassar, Eduardo J; Vicente, Miguel A; Trujillano, Raquel; Calefi, Paulo S

2009-07-15

69

Enantiomer analysis of chiral carboxylic acids by AIE molecules bearing optically pure aminol groups.  

PubMed

Pure enantiomers of carboxylic acids are a class of important biomolecules, chiral drugs, chiral reagents, etc. Analysis of the enantiomers usually needs expensive instrument or complex chiral receptors. However, to develop simple and reliable methods for the enantiomer analysis of acids is difficult. In this paper, chiral recognition of 2,3-dibenzoyltartaric acid and mandelic acid was first carried out by aggregation-induced emission molecules bearing optically pure aminol group, which was easily synthesized. The chiral recognition is not only seen by naked eyes but also measured by fluorophotometer. The difference of fluorescence intensity between the two enantiomers of the acids aroused by the aggregation-induced emission molecules was up to 598. The chiral recognition could be applied to quantitative analysis of enantiomer content of chiral acids. More chiral AIE amines need to be developed for enantiomer analysis of more carboxylic acids. PMID:20006116

Zheng, Yan-Song; Hu, Yu-Jian; Li, Dong-Mi; Chen, Yi-Chang

2010-01-15

70

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

2013-10-15

71

Ion-exchange behavior of carboxylate groups in fibrous cellulose oxidized by the TEMPO-mediated system  

Microsoft Academic Search

When native cellulose is treated by catalytic oxidation with 2,2,6,6-tetramethylpiperidine-1-oxy radical (TEMPO)\\/NaBr\\/NaClO under aqueous conditions, significant amounts of carboxylate and aldehyde groups can be introduced on surfaces of cellulose I crystallites and into disordered regions without any changes in crystallinity of cellulose I or in the original fibrous morphology. In this study, behavior of ion exchange of carboxylate groups in

T. Saito; A. Isogai

2005-01-01

72

Distribution of carboxylate groups introduced into cotton linters by the TEMPO-mediated oxidation  

Microsoft Academic Search

The 2,2,6,6-tetramethylpiperidine-1-oxy radial (TEMPO)-mediated oxidation was applied to aqueous slurries of cotton linters. The water-insoluble fibrous fractions thus obtained in the yields of more than 78% were characterized by solid-state 13C-NMR, X-ray diffraction and scanning electron microscopic analyses for evaluation of distribution of carboxylate groups formed in the TEMPO-oxidized celluloses. The patterns of solid-state 13C-NMR spectra revealed that the oxidation

T. Saito; I. Shibata; A. Isogai; N. Suguri; N. Sumikawa

2005-01-01

73

Aerobic visible light-oxidation of aromatic methyl groups to carboxylic acids.  

PubMed

A catalytic amount of magnesium bromide diethyl etherate (MgBr2.Et2O) enables us to carry out the aerobic photo-oxidation of a methyl group at the aromatic nucleus to the corresponding carboxylic acid in high yield under irradiation of VIS from a general-purpose fluorescent lamp. The bromine radical is thought to be generated in situ by continuous aerobic photo-oxidation of the bromine anion from MgBr2.Et2O, and to effect this oxidation reaction. PMID:17487303

Hirashima, Shin-ichi; Itoh, Akichika

2007-05-01

74

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

PubMed

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. PMID:23015826

Mrsevic, Miroslav; Düsselberg, David; Staudt, Claudia

2012-01-01

75

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

76

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

2013-11-01

77

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

78

Functional and anionic cellulose-interacting polymers by selective chemo-enzymatic carboxylation of galactose-containing polysaccharides.  

PubMed

Carboxylated, anionic polysaccharides were selectively prepared using a combination of enzymatic and chemical reactions. The galactose-containing polysaccharides studied were spruce galactoglucomannan, guar galactomannan, and tamarind galactoxyloglucan. The galactosyl units of the polysaccharides were first oxidized with galactose oxidase (EC 1.1.3.9) and then selectively carboxylated, resulting in the galacturonic acid derivatives with good conversion and yield. The degrees of oxidation (DO) of the products were determined by gas chromatography-mass spectrometry (GC-MS). A novel feasible electrospray ionization-mass spectrometry (ESI-MS) method was also developed for the determination of DO. The solution properties and charge densities of the products were investigated. The interaction of the products with cellulose was studied by two methods, bulk sorption onto bleached birch kraft pulp and adsorption onto nanocellulose ultrathin films by quartz crystal microbalance with dissipation (QCM-D). To study the effect of the location of the carboxylic acid groups on the physicochemical properties, polysaccharides were also oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-mediated reaction producing polyuronic acids. The chemo-enzymatically oxidized galacturonic polysaccharides with an unmodified backbone had a better ability to interact with cellulose than the TEMPO-oxidized products. The selectively carboxylated polysaccharides can be further exploited, as such, or in the targeted functionalization of cellulose surfaces. PMID:22724576

Parikka, Kirsti; Leppänen, Ann-Sofie; Xu, Chunlin; Pitkänen, Leena; Eronen, Paula; Osterberg, Monika; Brumer, Harry; Willför, Stefan; Tenkanen, Maija

2012-08-13

79

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

80

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

2012-10-22

81

Functional group-selective adsorption using scanning tunneling microscopy.  

PubMed

In this study, we selectively enhanced two types of adsorption of 3-mercaptoisobutyric acid on a Ge(100) surface by using the tunneling electrons from an STM and the catalytic effect of an STM tip. 3-Mercaptoisobutyric acid has two functional groups: a carboxylic acid group at one end of the molecule and a thiol group at the other end. It was found that the adsorption occurring through the carboxylic acid group was selectively enhanced by the application of electrons tunneling between an STM tip and the surface. Using this enhancement, it was possible to make thiol group-terminated surfaces at any desired location. In addition, via the use of a tungsten STM tip coated with a tungsten oxide (WO(3)) layer, we selectively catalyzed the adsorption through the thiol group. Using this catalysis, it was possible to generate carboxylic acid group-terminated surfaces at any desired location. This functional group-selective adsorption using STM could be applied in positive lithographic methods to produce semiconductor substrates terminated by desired functional groups. PMID:22458813

Min, Young Hwan; Park, Eun Hee; Kim, Do Hwan; Kim, Sehun

2012-04-24

82

Second-sphere tethering of rare-earth ions to cucurbit[6]uril by iminodiacetic acid involving carboxylic group encapsulation.  

PubMed

The reaction of rare-earth nitrates with iminodiacetic acid (H(2)IDA) in the presence of cucurbit[6]uril (CB6) in water at room temperature yields a family of isomorphous complexes, [M(H(2)IDA)(NO(3))(H(2)O)(6)](NO(3))(2)·CB6·14H(2)O with M = Y (1), Ce (2), Nd (3), Eu (4), Dy (5), Er (6), Tm (7), and Yb (8). In these compounds, the trivalent metal ion is bound to one nitrate ion, six water molecules, and one zwitterionic H(2)IDA molecule. The latter is further partly included in the CB6 cavity, with the ammonium group forming two hydrogen bonds with oxygen atoms of one portal. The uncoordinated carboxylic group is thus encapsulated in CB6 and hydrogen-bonded to the other portal via a water molecule. CB6 is a second-sphere ligand in these complexes, but direct bonding of the metal ion to CB6 can be enforced by using a ligand more deeply imbedded in the cavity, such as 2-pyridylacetate (PA) in [Eu(PA)(CB6)(NO(3))(H(2)O)(5)](NO(3))·10H(2)O (11). When the reaction with H(2)IDA is performed with Lu(III) or Cu(II), no metal complex is isolated, but the inclusion compounds [(H(3)IDA)(2)(CB6)](NO(3))(2)·xH(2)O with x = 6 (9) or 8 (10) are obtained instead, in which the two H(3)IDA(+) cations are attached to the CB6 portals by ammonium-carbonyl hydrogen bonds and are linked to one another inside the cavity by hydrogen bonding between the carboxylic groups. These complexes are compared to that comprising a dicarboxylic acid devoid of an ammonium functionality, [(H(2)AZ)(CB6)]·6H(2)O (12), where H(2)AZ is azelaic acid. The metal ion complexes 1-8 and the organic complexes 9 and 10 display the unprecedented feature of inclusion of carboxylic groups inside the CB6 cavity, with the CB6/acid stoichiometry and the finer details of the host-guest interactions being dependent on the presence of the metal ion. PMID:20815367

Thuéry, Pierre

2010-10-01

83

One-pot synthesis of mesoporous silica nanocarriers with tunable particle sizes and pendent carboxylic groups for cisplatin delivery.  

PubMed

Mesoporous silica nanocarriers with tunable particle sizes and different loadings of pendent carboxylic groups were successfully prepared by a straightforward and reproducible strategy, in which carboxyethylsilanetriol sodium salt was co-condensed with tetraethoxyorthosilicate to introduce the carboxylic groups. The key in this strategy was to separate the synthesis process into two steps of the nuclei formation and particle growth. The uniform particle size and ordered structure of the synthesized nanocarriers were manifested by several techniques such as XRD, TEM, SEM, and BET. DLS measurement illustrated that nanocarriers could be well suspended in aqueous solution. The integration and content tunability of the carboxylic groups within mesoporous silica nanoparticles (MSNs) were verified by FT-IR and (29)Si NMR. The inherent carboxylic units on the obtained carboxylic group modified MSNs (MSNs-C) effectively enhanced the capture and tailored the release properties of the anticancer drug of cisplatin. The accumulation of drug in the HeLa cells was greatly enhanced due to the highly efficient platinum uptake efficiency transported by the synthesized nanocarriers. The drug encapsulated in the MSNs-C exhibited a higher antitumor activity than free cisplatin against both MCF-7 and HeLa cells. PMID:23214476

Gu, Jinlou; Liu, Jiapeng; Li, Yongsheng; Zhao, Wenru; Shi, Jianlin

2013-01-01

84

Identification of the reactive sulfhydryl group of 1-aminocyclopropane-1-carboxylate deaminase.  

PubMed

1-Aminocyclopropane-1-carboxylate (ACC) deaminase, a pyridoxal phosphate enzyme that catalyzes cyclopropane ring-opening and deamination of ACC, formed a quinoid intermediate with D-alanine, as shown by the appearance of a 510-nm absorption band. The presence of D-alanine also stimulated the inactivation of ACC deaminase with iodoacetamide. The increase of absorbance at 510 nm and the stimulation of the enzyme inactivation were temperature-dependent with a critical point at around 20 degrees C, indicating a conformational change of the enzyme. To identify a reactive thiol group, this stimulated inactivation and an iodoacetamide derivative, N-(iodoacetamidoethyl)-1-aminonaphthalene-5- sulfonic acid were used. The residue that was modified by the specific reagent was monitored by absorbance at 350 nm through the digestion by lysylendopeptidase and the fractionation of peptides, and it was located at Cys-162 near the midpoint of the whole peptide chain of the ACC deaminase. PMID:7764364

Honma, M; Kawai, J; Yamada, M

1993-12-01

85

Highly carboxylic-acid-functionalized ethane-bridged periodic mesoporous organosilicas: synthesis, characterization, and adsorption properties.  

PubMed

Functionalization of periodic mesoporous organosilicas (PMOs) with high loadings of pendant organic groups to form bifunctional PMOs with ordered mesostructures remains a challenging objective. Herein, we report that well-ordered ethane-bridged PMOs functionalized with exceptionally high loadings of pendant carboxylic acid groups (up to 80 mol % based on silica) were synthesized by the co-condensation of 1,4-bis(trimethoxysilyl)ethane (BTME) and carboxyethylsilanetriol sodium salt (CES) with Pluronic P123 as the template and KCl as an additive under acidic conditions. The bifunctional materials were characterized by using a variety of techniques, including powder X-ray diffraction, nitrogen-adsorption/desorption, TEM, and solid-state (13)C and (29)Si NMR spectroscopy. Zeta-potential measurements showed that the surface negative charges increased with increasing the CES content. This property makes them potential candidates for applications in drug adsorption. The excellent adsorption capacity of these bifunctional PMOs towards an anticancer drug (doxorubicin) was also demonstrated. PMID:22689541

Kao, Hsien-Ming; Chung, Chih-Hsuan; Saikia, Diganta; Liao, Shih-Hsiang; Chao, Pei-Ying; Chen, Yu-Han; Wu, Kevin C-W

2012-09-01

86

Detection of a CO and NH3 gas mixture using carboxylic acid-functionalized single-walled carbon nanotubes.  

PubMed

Carbon nanotubes (CNT) are extremely sensitive to environmental gases. However, detection of mixture gas is still a challenge. Here, we report that 10 ppm of carbon monoxide (CO) and ammonia (NH3) can be electrically detected using a carboxylic acid-functionalized single-walled carbon nanotubes (C-SWCNT). CO and NH3 gases were mixed carefully with the same concentrations of 10 ppm. Our sensor showed faster response to the CO gas than the NH3 gas. The sensing properties and effect of carboxylic acid group were demonstrated, and C-SWCNT sensors with good repeatability and fast responses over a range of concentrations may be used as a simple and effective detection method of CO and NH3 mixture gas. PMID:23286690

Dong, Ki-Young; Choi, Jinnil; Lee, Yang Doo; Kang, Byung Hyun; Yu, Youn-Yeol; Choi, Hyang Hee; Ju, Byeong-Kwon

2013-01-01

87

Preferential interaction of Na(+) over K(+) with carboxylate-functionalized silver nanoparticles.  

PubMed

Elucidating mechanistic interactions between monovalent cations (Na(+)/K(+)) and engineered nanoparticle surfaces to alter particle stability in polar media have received little attention. We investigated relative preferential interaction of Na(+) and K(+) with carboxylate-functionalized silver nanoparticles (carboxylate-AgNPs) to determine if interaction preference followed the Hofmeister series (Na(+)>K(+)). We hypothesized that Na(+) will show greater affinity than K(+) to pair with carboxylates on AgNP surfaces, thereby destabilizing the colloidal system. Destabilization upon Na(+) or K(+) interacting with carboxylate-AgNPs was evaluated probing changes in multiple physicochemical characteristics: surface plasmon resonance/optical absorbance, electrical conductivity, pH, hydrodynamic diameter, electrophoretic mobility, surface charge, amount of Na(+)/K(+) directly associated with AgNPs, and Ag(+) dissociation kinetics. We show that Na(+) and K(+) react differently, indicating local Na(+) pairing with carboxylates on AgNP surfaces is kinetically faster and remarkably favored over K(+), thus supporting Hofmeister ordering. Our results suggest that AgNPs may transform into micron-size aggregates upon release into aqueous environments and that the fate of such aggregates may need consideration when assessing environmental risk. PMID:24840275

Pokhrel, Lok R; Andersen, Christian P; Rygiewicz, Paul T; Johnson, Mark G

2014-08-15

88

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

89

Changes in the state of ionization of carboxyl groups in elastin in response to the binding of sodium dodecyl sulfate.  

PubMed

The interaction of sodium dodecyl sulfate with elastin has been studied by complexometric titration. Approximately 1.2 mumoles of protons with a pKapp of 5.45 are taken up by 10 milligrams of insoluble elastin upon the binding of detergent, apparently due to the protonation of normally ionized carboxylate functions in this protein. Since ionized carboxylate functions of elastin are essential for its interaction with elastase and, possibly, metallic cations, these results may have physiological significance in view of the affinity of elastin for lipid-like ligands. PMID:34500

Kagan, H M

1978-01-01

90

Ergodic Properties of Function Groups  

Microsoft Academic Search

Let G ?PSL(2,C) be a torsion free function group. We discuss some aspects of the asymptotic relation between the geometry of the hyperbolic manifold H3\\/G and the geometry of the boundary of its convex core. This leads to a characterization of Fuchsian function groups by dynamical invariants.

Ursula Hamenstädt

2002-01-01

91

Characterization of Negative Tone Photoresist Based on Acid Catalyzed Dehydration Crosslinking of Novolac Resins Having Pendant Carboxyl Groups  

Microsoft Academic Search

Esterification of 4-hydroxyphenylacetic acid with various alcohols of (+)-borneol, (±)-borneol and ethylene glycol monobutyl ether were carried out. The ester compounds were then copolymerized with various comonomers of bisphenol-A, phenol and formaldehyde. Physical properties and molecular structures of such synthesized phenolic resins were investigated by using IR, NMR, DSC, and TGA. To introduce carboxyl groups onto the side chain of

Hui-Hsiang Liu; Wei-Tin Chen; Fuh-Tsang Wu

2002-01-01

92

A direct anchoring of Anderson-type polyoxometalates in aqueous media with tripodal ligands especially containing the carboxyl group.  

PubMed

Polyoxometalate-based organic-inorganic hybrids were synthesized by direct modification of the parent Anderson cluster with both the traditional tripodal ligand, CH3C(CH2OH)3, and a novel one containing a carboxyl group, CH3C(CH2OH)2(COOH), which was inaccessible from the traditional self-assembly protocol. PMID:24356499

Zhang, Jiangwei; Huang, Yichao; Zhang, Jin; She, Shan; Hao, Jian; Wei, Yongge

2014-02-21

93

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

94

Carboxylic Acid-Functionalized Conductive Polypyrrole as a Bioactive Platform for Cell Adhesion  

PubMed Central

Electroactive polymers such as polypyrrole (PPy) are highly attractive for a number of biomedical applications, including their use as coatings for electrodes or neural probes and as scaffolds to induce tissue regeneration. Surface modification of these materials with biological moieties is desired to enhance the biomaterial-tissue interface and to promote desired tissue responses. Here, we present the synthesis and physicochemical characterization of poly(1-(2-carboxyethyl)pyrrole) (PPyCOOH), a PPy derivative that contains a chemical group that can be easily modified with biological moieties at the N-position of polymer backbone. FTIR, XPS, and fluorescence microscopy were used to demonstrate the successful incorporation of carboxylic acid (-COOH) functionality into PPy materials, and a four-point probe analysis was used to demonstrate electrical conductivity in the semiconductor range. Human umbilical vascular endothelial cells (HUVECs) cultured on PPyCOOH films surface modified with the cell-adhesive Arg-Gly-Asp (RGD) motif demonstrated improved attachment and spreading. Thus, PPyCOOH could be useful in developing PPy composites that contain a variety of biological molecules as bioactive conducting platforms for specific biomedical purposes.

Lee, Joo-Woon; Serna, Francisco; Nickels, Jonathan; Schmidt, Christine E.

2008-01-01

95

Facile one-step coating approach to magnetic submicron particles with poly(ethylene glycol) coats and abundant accessible carboxyl groups  

PubMed Central

Purpose Magnetic submicron particles (MSPs) are pivotal biomaterials for magnetic separations in bioanalyses, but their preparation remains a technical challenge. In this report, a facile one-step coating approach to MSPs suitable for magnetic separations was investigated. Methods Polyethylene glycol) (PEG) was derived into PEG-bis-(maleic monoester) and maleic monoester-PEG-succinic monoester as the monomers. Magnetofluids were prepared via chemical co-precipitation and dispersion with the monomers. MSPs were prepared via one-step coating of magnetofluids in a water-in-oil microemulsion system of aerosol-OT and heptane by radical co-polymerization of such monomers. Results The resulting MSPs contained abundant carboxyl groups, exhibited negligible nonspecific adsorption of common substances and excellent suspension stability, appeared as irregular particles by electronic microscopy, and had submicron sizes of broad distribution by laser scattering. Saturation magnetizations and average particle sizes were affected mainly by the quantities of monomers used for coating magnetofluids, and steric hindrance around carboxyl groups was alleviated by the use of longer monomers of one polymerizable bond for coating. After optimizations, MSPs bearing saturation magnetizations over 46 emu/g, average sizes of 0.32 ?m, and titrated carboxyl groups of about 0.21 mmol/g were obtained. After the activation of carboxyl groups on MSPs into N-hydroxysuccinimide ester, biotin was immobilized on MSPs and the resulting biotin-functionalized MSPs isolated the conjugate of streptavidin and alkaline phosphatase at about 2.1 mg/g MSPs; streptavidin was immobilized at about 10 mg/g MSPs and retained 81% ± 18% (n = 5) of the specific activity of the free form. Conclusion The facile approach effectively prepares MSPs for magnetic separations.

Long, Gaobo; Yang, Xiao-lan; Zhang, Yi; Pu, Jun; Liu, Lin; Liu, Hong-bo; Li, Yuan-li; Liao, Fei

2013-01-01

96

Preparation and characterization of TEMPO-oxidized cellulose nanofibrils with ammonium carboxylate groups.  

PubMed

Fibrous TEMPO-oxidized celluloses with 100% ammonium carboxylate groups (TOC-COONH4) were prepared by adding aqueous ammonia to fibrous TOC-COOH/water slurries. Using a gentle mechanical disintegration treatment in water, the obtained never-dried TOC-COONH4/water slurries could be converted to highly viscous and transparent gels consisting of mostly individualized TEMPO-oxidized cellulose nanofibrils. The self-standing TOCN-COONH4 film prepared from the aqueous TOCN-COONH4 dispersion via casting and drying had high optical transparency. When the self-standing TOCN-COONH4 film was heated at 105°C for 1 day, clear yellowing was observed on the film. FT-IR analysis of the heated TOCN-COONH4 films indicated the partial formation of TOCN-COOH type structures from the TOCN-COONH4 due to evaporation of NH3 gas from the films during heating. The heated TOCN-COONH4 films had lower moisture contents, higher film densities, and higher Young's moduli than the unheated TOCN-COONH4 films. PMID:23597708

Shimizu, Michiko; Fukuzumi, Hayaka; Saito, Tsuguyuki; Isogai, Akira

2013-08-01

97

A facile method to synthesize carboxyl-functionalized magnetic polystyrene nanospheres  

Microsoft Academic Search

Magnetic polystyrene nanospheres with high magnetite content and abundant surface carboxyl groups were prepared by emulsifier-free emulsion polymerization in the presence of aqueous magnetic fluid coated with oleic acid and 10-undecenoic acid as primary and secondary surfactants respectively. The effects of initiator concentration, initiator type (water-soluble or oil-soluble), monomer concentration and ferrofluid content on the particle characteristics such as the

Ningning Guan; Chao Liu; Dejun Sun; Jian Xu

2009-01-01

98

Porphyrin-sensitized solar cells: effect of carboxyl anchor group orientation on the cell performance.  

PubMed

The effect of the orientation of the porphyrin sensitizer onto the TiO2 surface on the performance of dye-sensitized solar cells (DSSCs) is reported. Free-base and zinc porphyrins bearing a carboxyl anchoring group at the para, meta, or ortho positions of one of the meso-phenyl rings were synthesized for application in Grätzel-type photoelectrochemical cells. The remainder of the meso-phenyl rings was substituted with alkyl chains of different length to visualize any aggregation effects. Absorption and fluorescence studies were performed to characterize and observe spectral coverage of the thirteen newly synthesized porphyrin derivatives. Photoelectrochemical studies were performed after immobilization of porphyrins onto nanocrystalline TiO2 and compared with DSSC constructed using N719 dye as reference. The performance of DSSCs with the porphyrin anchoring at the para or meta position were found to greatly exceed those with the anchoring group in the ortho position. Additionally, cells constructed using zinc porphyrin derivatives outperformed the free-base porphyrin analogs. Better dye regeneration efficiency for the zinc porphyrin derivatives compared to their free-base porphyrin analogs, and for the meta and para derivatives over the ortho derivatives was evaluated from electrochemical impedance spectroscopy studies. Femtosecond transient absorption spectroscopy studies were performed to probe the kinetics of charge injection and charge recombination with respect to the orientation of porphyrin macrocycle on TiO2 surface. The ortho porphyrin derivative with an almost flat orientation to the TiO2 surface revealed fast charge recombination and suggested occurrence of through-space charge transfer. The overall structure-performance trends observed for the present porphyrin DSSCs have been rationalized based on spectral, electrochemical, electrochemical impedance spectroscopy, and transient spectroscopy results. PMID:23647324

Hart, Aaron S; Chandra, B K C; Gobeze, Habtom B; Sequeira, Lindsey R; D'Souza, Francis

2013-06-12

99

Effects of reagents modifying carboxyl groups on the gating current of the myelinated nerve fiber.  

PubMed

The effect of the carboxyl group activating reagent N-ethoxy-carbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ) on the gating current of the frog node of Ranvier was investigated. A 10-min treatment with 2 mM EEDQ (in the presence or absence of 10 mM ethylenediamine) irreversibly reduced the slope of the on charge-voltage relation Qon(E), shifted its midpoint potential Emid in the positive direction and reduced the maximum charge Qon max measured with strong depolarizing pulses. In six experiments, 2 mM EEDQ + 10 mM ethylenediamine increased the factor k (a reciprocal measure of the slope of the Qon(E) curve) from 16 to 22 mV. In five experiments, 2 mM EEDQ alone increased k from 16 to 23 mV. In a single experiment, 5 mM EEDQ + 10 mM ethylene diamine increased k from 17 to 31 mV. The reduction in slope suggests that EEDQ decreases the valence of the gating particles or reduces the fraction of the membrane field that they traverse. In addition, EEDQ (which inhibits inactivation of the sodium current, see M. Rack and K.H. Woll, J. Membrane Biol. 82:41-48, 1984) caused a small increase of the off charge Qoff, and a marked increase of the Qoff/Qon ratio, i.e. inhibited charge immobilization. Since the effects of EEDQ occurred regardless of the presence or absence of ethylenediamine, they are probably due to crosslinking reactions. The effects of EEDQ were compared with those of the water-soluble carbodiimide EDC. Treatment with 10 or 50 mM EDC (plus 10 or 50 mM ethylenediamine) caused a smaller increase of k than treatment with 2 mM EEDQ but reduced Qon max by the same amount. PMID:2448468

Meves, H; Rubly, N

1987-01-01

100

U.v.-irradiation of thin films of polystyrene derivatives: formation of carboxylic group and crosslinking from 4-trimethylsilylmethyl substituent  

Microsoft Academic Search

Photoirradiation of thin films of poly(4-trimethylsilylmethylstyrene) (PTMSMS), poly(4-methylstyrene) (P4MS), and polystyrene (PS) at 254 nm with a low-pressure Hg lamp in air made the surfaces hydrophilic through oxygenation. The hydrophilicity estimated from the contact angle with water was in the order of PTMSMS ? P4MS > PS. Formation of carboxylic acid group on the surface and crosslinking in the bulk

Hiroo Inoue; Kazuhiko Mizuno; N ICHINOSE; S KAWANISHI

1996-01-01

101

Nickel-catalysed carboxylation of organoboronates.  

PubMed

A nickel/N-heterocyclic carbene (NHC) catalysed carboxylation of aryl-, heteroaryl- and alkenylboronates, affording the corresponding carboxylic acids, has been developed. This transformation proceeds under one atmosphere of CO2 with a broad range of substrates and exhibits good functional group compatibility. PMID:24915842

Makida, Yusuke; Marelli, Enrico; Slawin, Alexandra M Z; Nolan, Steven P

2014-06-26

102

New Ru(II) phenanthroline complex photosensitizers having different number of carboxyl groups for dye-sensitized solar cells  

Microsoft Academic Search

We have prepared and characterized four carboxylated Ru(II) phenanthroline complexes with different number of carboxyl groups, cis-dithiocyanato bis(4,7-dicarboxy-1,10-phenanthroline) ruthenium(II) [Ru(dcphen)2(NCS)2, DCP2], cis-dithiocyanato bis(4-monocarboxy-1,10-phenanthroline) ruthenium(II) [Ru(mcphen)2(NCS)2, MCP2], cis-dithiocyanato (4,7-dicarboxy-1,10-phenanthroline) (1,10-phenanthroline) ruthenium(II) [Ru(dcphen)(phen)(NCS)2, DCPP], and cis-dithiocyanato (4-monocarboxy-1,10-phenanthroline)(1,10-phenanthroline) ruthenium(II) [Ru(mcphen)(phen)(NCS)2, MCPP], as photosensitizers for nanocrystalline dye-sensitized solar cells. All complexes exhibit a broad MLCT absorption band around 500nm in ethanol and an emission

Kohjiro Hara; Hideki Sugihara; Lok Prapap Singh; Ashlaful Islam; Ryuzi Katoh; Masatoshi Yanagida; Kazuhiro Sayama; Shigeo Murata; Hironori Arakawa

2001-01-01

103

Kinetic and equilibrium characterization of uranium(VI) adsorption onto carboxylate-functionalized poly(hydroxyethylmethacrylate)-grafted lignocellulosics.  

PubMed

This study investigated the feasibility of using a new adsorbent prepared from coconut coir pith, CP (a coir industry-based lignocellulosic residue), for the removal of uranium [U(VI)] from aqueous solutions. The adsorbent (PGCP-COOH) having a carboxylate functional group at the chain end was synthesized by grafting poly(hydroxyethylmethacrylate) onto CP using potassium peroxydisulphate-sodium thiosulphite as a redox initiator and in the presence of N,N'-methylenebisacrylamide as a crosslinking agent. IR spectroscopy results confirm the graft copolymer formation and carboxylate functionalization. XRD studies confirm the decrease of crystallinity in PGCP-COOH compared to CP, and it favors the protrusion of the functional group into the aqueous medium. The thermal stability of the samples was studied using thermogravimetry (TG). Surface charge density of the samples as a function of pH was determined using potentiometric titration. The ability of PGCP-COOH to remove U(VI) from aqueous solutions was assessed using a batch adsorption technique. The maximum adsorption capacity was observed at the pH range 4.0-6.0. Maximum removal of 99.2% was observed for an initial concentration of 25mg/L at pH 6.0 and an adsorbent dose of 2g/L. Equilibrium was achieved in approximately 3h. The experimental kinetic data were analyzed using a first-order kinetic model. The temperature dependence indicates an endothermic process. U(VI) adsorption was found to decrease with an increase in ionic strength due to the formation of outer-sphere surface complexes on PGCP-COOH. Equilibrium data were best modeled by the Langmuir isotherm. The thermodynamic parameters such as DeltaG(0), DeltaH(0) and DeltaS(0) were derived to predict the nature of adsorption. Adsorption experiments were also conducted using a commercial cation exchanger, Ceralite IRC-50, with carboxylate functionality for comparison. Utility of the adsorbent was tested by removing U(VI) from simulated nuclear industry wastewater. Adsorbed U(VI) ions were desorbed effectively (about 96.2+/-3.3%) by 0.1M HCl. The adsorbent was suitable for repeated use (more than four cycles) without any noticeable loss of capacity. PMID:18222595

Anirudhan, T S; Divya, L; Suchithra, P S

2009-01-01

104

Variation in Optoelectronic Properties of Azo Dye-Sensitized TiO2 Semiconductor Interfaces with Different Adsorption Anchors: Carboxylate, Sulfonate, Hydroxyl and Pyridyl Groups.  

PubMed

The optoelectronic properties of four azo dye-sensitized TiO2 interfaces are systematically studied as a function of a changing dye anchoring group: carboxylate, sulfonate, hydroxyl, and pyridyl. The variation in optoelectronic properties of the free dyes and those in dye/TiO2 nanocomposites are studied both experimentally and computationally, in the context of prospective dye-sensitized solar cell (DSSC) applications. Experimental UV/vis absorption spectroscopy, cyclic voltammetry, and DSSC device performance testing reveal a strong dependence on the nature of the anchor of the optoelectronic properties of these dyes, both in solution and as dye/TiO2 nanocomposites. First-principles calculations on both an isolated dye/TiO2 cluster model (using localized basis sets) and each dye modeled onto the surface of a 2D periodic TiO2 nanostructure (using plane wave basis sets) are presented. Detailed examination of these experimental and computational results, in terms of light harvesting, electron conversion and photovoltaic device performance characteristics, indicates that carboxylate is the best anchoring group, and hydroxyl is the worst, whereas sulfonate and pyridyl groups exhibit competing potential. Different sensitization solvents are found to affect critically the extent of dye adsorption achieved in the dye-sensitization of the TiO2 semiconductor, especially where the anchor is a pyridyl group. PMID:24786472

Zhang, Lei; Cole, Jacqueline M; Dai, Chencheng

2014-05-28

105

Photophysical Properties of Lanthanide Hybrids Covalently Bonded To Functionalized MCM-41 by Modified Aromatic Carboxylic Acids  

Microsoft Academic Search

MCM-41 mesoporous silica has been functionalized with aromatic carboxylic acids salicylic acid (Sal) and 2-hydroxyl-3-methylbenzoic\\u000a acid (HMBA) through co-condensation approach of tetraethoxysilane (TEOS) in the presence of the cetyltrimethylammonium bromide\\u000a (CTAB) surfactant as a template. Organic ligands salicylic acid or 2-hydroxyl-3-methylbenzoic acid grafted to the coupling\\u000a agent 3-(triethoxysilyl)-propyl isocyanate (TEPIC) was used as the precursor for the preparation of an

Ying Li; Bing Yan

2009-01-01

106

Enantiomer analysis of chiral carboxylic acids by AIE molecules bearing optically pure aminol groups  

Microsoft Academic Search

Pure enantiomers of carboxylic acids are a class of important biomolecules, chiral drugs, chiral reagents, etc. Analysis of the enantiomers usually needs expensive instrument or complex chiral receptors. However, to develop simple and reliable methods for the enantiomer analysis of acids is difficult. In this paper, chiral recognition of 2,3-dibenzoyltartaric acid and mandelic acid was first carried out by aggregation-induced

Yan-Song Zheng; Yu-Jian Hu; Dong-Mi Li; Yi-Chang Chen

2010-01-01

107

Hydrogenation of unsaturated carboxylic acids on functional gel-type resin supported Pd catalysts: The effect of reactant structure  

Microsoft Academic Search

Functional gel-type resin-based palladium catalysts (0.5–2wt.% Pd) of well dispersed Pd nanoparticles were prepared and characterized by SEM, TEM techniques and swelling measurements. The role of specific properties of gel-type matrix was studied in the hydrogenation of unsaturated CC bonds in series of carboxylic acids, derivatives of acrylic acid. They differ in the type of substituents (methyl, phenyl and carboxyl

A. Knapik; A. Drelinkiewicz; M. Szaleniec; W. Makowski; A. Waksmundzka-Góra; A. Bukowska; W. Bukowski; J. Noworól

2008-01-01

108

ATR-FTIR spectroscopic evidence for biomolecular phosphorus and carboxyl groups facilitating bacterial adhesion to iron oxides.  

PubMed

Attenuated total reflectance (ATR) Fourier transform infrared (FTIR) spectroscopy has been used to probe the binding of bacteria to hematite (?-Fe2O3) and goethite (?-FeOOH). In situ ATR-FTIR experiments with bacteria (Pseudomonas putida, Pseudomonas aeruginosa, Escherichia coli), mixed amino acids, polypeptide extracts, deoxyribonucleic acid (DNA), and a suite of model compounds were conducted. These compounds represent carboxyl, catecholate, amide, and phosphate groups present in siderophores, amino acids, polysaccharides, phospholipids, and DNA. Due in part to the ubiquitous presence of carboxyl groups in biomolecules, numerous IR peaks corresponding to outer-sphere or unbound (1400cm(-1)) and inner-sphere (1310-1320cm(-1)) coordinated carboxyl groups are noted following reaction of bacteria and biomolecules with ?-Fe2O3 and ?-FeOOH. However, the data also reveal that the presence of low-level amounts (i.e., 0.45-0.79%) of biomolecular phosphorous groups result in strong IR bands at ?1043cm(-1), corresponding to inner-sphere FeOP bonds, underscoring the importance of bacteria associated P-containing groups in biomolecule and cell adhesion. Spectral comparisons also reveal slightly greater POFe contributions for bacteria (Pseudomonad, E. coli) deposited on ?-FeOOH, as compared to ?-Fe2O3. This data demonstrates that slight differences in bacterial adhesion to Fe oxides can be attributed to bacterial species and Fe-oxide minerals. However, more importantly, the strong binding affinity of phosphate in all bacteria samples to both Fe-oxides results in the formation of inner-sphere FeOP bonds, signifying the critical role of biomolecular P in the initiation of bacterial adhesion. PMID:24859052

Parikh, Sanjai J; Mukome, Fungai N D; Zhang, Xiaoming

2014-07-01

109

Isotope labelling - paired homologous double neutral loss scan-mass spectrometry for profiling of metabolites with a carboxyl group.  

PubMed

We developed a novel method for non-targeted screening of metabolites by high performance liquid chromatography-mass spectrometry with paired homologous double neutral loss scan mode after in vitro isotope labelling (IL-HPLC-PHDNL-MS). As a proof of concept, we investigated the carboxylic acid metabolite profiling in plant samples by the IL-HPLC-PHDNL-MS method. To this end, N,N-dimethylaminobutylamine (DMBA) and d(4)-N,N-dimethylaminobutylamine (d(4)-DMBA) were synthesized and utilized to label carboxylic acids. Our results show the MS response of carboxylic acids was enhanced by 20- to 40-fold after labelling. As for the IL-HPLC-PHDNL-MS analysis, DMBA and d(4)-DMBA labelled samples were mixed equally before MS analysis. Because the isotope labelled moieties (dimethylamino moiety, Me2N) of DMBA and d(4)-DMBA are easily ruptured and lost as neutral fragments (NL 45 and NL 49) under collision induced dissociation (CID), two neutral loss scans can be carried out simultaneously to record the signals of DMBA and d(4)-DMBA labelled samples, respectively. In this respect, the metabolites from two samples labelled with different isotope reagents are ionized at the same time but recorded separately by mass spectrometry, which can eliminate the MS response fluctuation and mutual interference. Using this method, six potential biomarkers involved in wounded tomato leaves were identified, and their structures were further elucidated by product ion scan and high resolution mass spectrometry analysis. Taken together, the IL-HPLC-PHDNL-MS method demonstrated good performance on the identification as well as relative quantification of metabolites with a carboxyl group in biological samples. PMID:24839964

Huang, Yun-Qing; Wang, Qiu-Yi; Liu, Jia-Qi; Hao, Yan-Hong; Yuan, Bi-Feng; Feng, Yu-Qi

2014-06-01

110

Learning the Functional Groups: Keys to Success.  

ERIC Educational Resources Information Center

Points out the difficulties students have when they are expected to learn functional groups, which are frameworks for chemical and physical properties of molecules. Presents a classification key for functional groups categorized by 10 common functional groups. (YDS)

Byrd, Shannon; Hildreth, David P.

2001-01-01

111

Mapping functional groups on oxidised multi-walled carbon nanotubes at the nanometre scale.  

PubMed

Despite voluminous research on the acid oxidation of carbon nanotubes (CNTs), there is a distinct lack of experimental results showing distributions of functional groups at the nanometre length scale. Here, functional peaks have been mapped across individual multi-walled CNTs with low-dose, monochromated electron energy-loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM). Density functional theory simulations show that the EELS features are consistent with oxygenated functional groups, most likely carboxyl moieties. PMID:24827593

Goode, A E; Hine, N D M; Chen, S; Bergin, S D; Shaffer, M S P; Ryan, M P; Haynes, P D; Porter, A E; McComb, D W

2014-05-29

112

Photoactivation of amino-substituted 1,4-benzoquinones for release of carboxylate and phenolate leaving groups using visible light.  

PubMed

Upon exposure to visible light, 2-pyrrolidino-substituted 3,6-dimethyl-1,4-benzoquinones photocyclize to give benzoxazolines with quantum yields of 0.07-0.10 in CH2Cl2, 0.02-0.04 in CH3CN, and <0.01 in 30% aq CH3CN. With carboxylate or phenolate leaving groups incorporated via coupling to a 5-hydroxymethyl group of the quinones, the photocyclizations give benzoxazolines that eliminate the leaving groups in a dark reaction. Lifetimes for elimination of 4-YC6H4OH in 30% phosphate buffer in CD3CN (pD 7) at 17 degrees C are 13.1, 0.54, and 0.13 h for Y = H, CF3, and CN, respectively, and the linear equation log k (h(-1)) = 0.998(-pKa) + 8.80 gives a best fit to the data. Carboxylate leaving groups are rapidly eliminated upon photolysis of the quinones in aq CH3CN to produce an o-quinone methide intermediate that is trapped by 4 + 2 cycloaddition with unreacted starting material or with added 3-(dimethylamino)-5,5-dimethyl-2-cyclohexen-1-one. The ortho-quinone methide is observed at 339 and 455 nm by conventional absorption spectroscopy and gives a pseudo-first-order fit of the decay kinetics with tau1/2 = 34.9 min in 30% phosphate buffer in CH3CN at 20 degrees C. PMID:16872188

Chen, Yugang; Steinmetz, Mark G

2006-08-01

113

Functionalization of carboxylated multiwall nanotubes with imidazole derivatives and their toxicity investigations  

PubMed Central

Imidazoles and their derivatives are compounds with chemotherapeutic applications. In this study, we investigated the chemical functionalization of carboxylated multiwalled carbon nanotubes (MWNT–COOH) by 1,2-phenylendiamine. Multiwalled nanotube (MWNT)–benzimidazole was obtained by an MWNT–amide reaction with POCl3 after 72 hours, which was confirmed by Fourier transform infrared, scanning electron microscopy, thermal gravimetric analysis, and elemental analysis. These functionalizations were chosen due to -NH2 and NHCO active sites in MWNT–amide for future application. Toxicity assays with fibroblast cells and MTT test for measurement of viable cell numbers were also performed. Cellular results did not show any toxicity change in modified samples from that of the reference samples.

Azizian, Javad; Tahermansouri, Hasan; Biazar, Esmaeil; Heidari, Saeed; Khoei, Davood Chobfrosh

2010-01-01

114

Functionalization of carboxylated multiwall nanotubes with imidazole derivatives and their toxicity investigations.  

PubMed

Imidazoles and their derivatives are compounds with chemotherapeutic applications. In this study, we investigated the chemical functionalization of carboxylated multiwalled carbon nanotubes (MWNT-COOH) by 1,2-phenylendiamine. Multiwalled nanotube (MWNT)-benzimidazole was obtained by an MWNT-amide reaction with POCl(3) after 72 hours, which was confirmed by Fourier transform infrared, scanning electron microscopy, thermal gravimetric analysis, and elemental analysis. These functionalizations were chosen due to -NH(2) and NHCO active sites in MWNT-amide for future application. Toxicity assays with fibroblast cells and MTT test for measurement of viable cell numbers were also performed. Cellular results did not show any toxicity change in modified samples from that of the reference samples. PMID:21116331

Azizian, Javad; Tahermansouri, Hasan; Biazar, Esmaeil; Heidari, Saeed; Khoei, Davood Chobfrosh

2010-01-01

115

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

116

pH, ionic strength, and temperature dependences of ionization equilibria for the carboxyl groups in turkey ovomucoid third domain.  

PubMed

Two-dimensional NMR spectroscopy has been used to monitor the pH dependences of proton chemical shifts for turkey ovomucoid third domain (OMTKY3). Sample pH was varied from 7.0 to 1.4 in order to determine the apparent pKa values of all six carboxyl groups in OMTKY3. At 35 degrees C and in the presence of 10 mM KCl, the pKa values for Asp 7, Glu 19, and Asp 27 (< 2.6, 3.2, and < 2.3, respectively) are more than 1 pH unit below those for model compounds. The pKa values for Glu 10 (4.1) and Glu 43 (4.7) show more modest deviations from model compound data. The low pKa for the alpha-carboxyl group of Cys 56 (< 2.5) is attributable, at least in part, to acidification by the disulfide group. Fitting the data to a modified Hill equation [Markley, J. L. (1975) Acc. Chem. Res. 8, 70-80] reveals little evidence for interactions between the acidic groups; most Hill coefficients fall between 0.8 and 1.2, with outlying values usually obtained with data that describe incomplete transitions. Most of the very low pKa values show increases in the presence of 1.0 M KCl but, with the exception of that for glutamate 19, remain well below model compound values. pH-dependent changes in amide proton chemical shifts permitted identification of hydrogen bonds involving the side chains of Asp 7, Glu 19, and Asp 27, which may partially explain the low pKa values for these groups. These hydrogen bonds, two of which involve side chains that are well exposed to solvent, were previously identified in high-resolution X-ray studies of turkey ovomucoid third domain [Fujinaga, M., Sielecki, A. R., Read, R. J., Ardelt, W., Laskowski, M., Jr., & James, M. N. G. (1987) J. Mol. Biol. 195, 397-418]. Results of additional experiments performed at 15, 25, and 40 degrees C suggest that apparent ionization enthalpies for all carboxyl groups in OMTKY3 are about 0 +/- 2 kcal/mol. In the accompanying paper [Swint, L., & Robertson, A. D. (1995) Biochemistry 34, 4724-4732], the pH dependence of OMTKY3 stability is described and compared to expectations based on the pKa values described herein. PMID:7718577

Schaller, W; Robertson, A D

1995-04-11

117

Functional group composition of ambient and source organic aerosols determined by tandem mass spectrometry  

NASA Astrophysics Data System (ADS)

The functional group composition of various organic aerosols (OA) is being investigated using a recently developed analytical approach based on atmospheric pressure chemical ionisation-tandem mass spectrometry (APCI-MS/MS). The determinations of the three functional groups' contents are performed quantitatively by neutral loss (carboxylic and carbonyl groups) and precursor ion (nitro groups) scanning modes of a tandem mass spectrometer. Major organic aerosol sources are studied: vehicular emission and wood combustion for primary aerosol sources; and a secondary organic aerosol (SOA) produced through photo-oxidation of o-xylene. The results reveal significant differences in the functional group contents of these source aerosols. The laboratory generated SOA is dominated by carbonyls while carboxylics are preponderate in the wood combustion particles. On the other hand, vehicular emissions are characterised by a strong nitro content. The total amount of the three functional groups accounted for 1.7% (vehicular) to 13.5% (o-xylene photo-oxidation) of the organic carbon. The diagnostic functional group ratios are then used to tentatively differentiate sources of particles collected in an urban background environment located in an Alpine valley (Chamonix, France) during a strong winter pollution event. The three functional groups under study account for a total functionalisation rate of 2.2 to 3.8% of the organic carbon in this ambient aerosol, which is also dominated by carboxylic moieties. In this particular case study of a deep alpine valley during winter, we show that the nitro- and carbonyl-to-carboxylic diagnostic ratios can be a useful tool to distinguish the sources. In these conditions, the total OA concentrations are highly dominated by wood combustion OA. This result is confirmed by an organic markers source apportionment approach which assesses a wood burning organic carbon contribution of about 60%. Finally, examples of functional group mass spectra of all aerosols under study are presented, and additional perspectives offered by the mass spectra in terms of the OA characterisation are discussed.

Dron, J.; El Haddad, I.; Temime-Roussel, B.; Jaffrezo, J.-L.; Wortham, H.; Marchand, N.

2010-04-01

118

Functional group composition of ambient and source organic aerosols determined by tandem mass spectrometry  

NASA Astrophysics Data System (ADS)

The functional group composition of various organic aerosols (OA) is investigated using a recently developed analytical approach based on atmospheric pressure chemical ionisation-tandem mass spectrometry (APCI-MS/MS). The determinations of three functional groups contents are performed quantitatively by neutral loss (carboxylic and carbonyl groups, R-COOH and R-CO-? respectively) and precursor ion (nitro groups, R-NO2) scanning modes of a tandem mass spectrometer. Major organic aerosol sources are studied: vehicular emission and wood combustion for primary aerosol sources; and a secondary organic aerosol (SOA) produced through photooxidation of o-xylene. The results reveal significant differences in the functional group contents of these source aerosols. The laboratory generated SOA is dominated by carbonyls while carboxylics are preponderate in the wood combustion particles. On the other hand, vehicular emissions are characterised by a strong nitro content. The total amount of the three functional groups accounts for 1.7% (vehicular) to 13.5% (o-xylene photooxidation) of the organic carbon. Diagnostic functional group ratios are then used to tentatively discriminate sources of particles collected in an urban background environment located in an Alpine valley (Chamonix, France) during a strong winter pollution event. The three functional groups under study account for a total functionalisation rate of 2.2 to 3.8% of the organic carbon in this ambient aerosol, which is also dominated by carboxylic moieties. In this particular case study of a deep alpine valley during winter, we show that the nitro- and carbonyl-to-carboxylic diagnostic ratios can be a useful tool to discriminate sources. In these conditions, the total OA concentrations are highly dominated by wood combustion OA. This result is confirmed by an organic markers source apportionment approach which assess a wood burning organic carbon contribution of about 60%. Finally, examples of functional group mass spectra of all aerosols under study are presented, and additional perspectives offered by the mass spectra in terms of OA characterisation are discussed.

Dron, J.; El Haddad, I.; Temime-Roussel, B.; Jaffrezo, J.-L.; Wortham, H.; Marchand, N.

2010-08-01

119

Modification of chitosan with carboxyl-functionalized ionic liquid for anion adsorption.  

PubMed

We report a novel chitosan derivative, chitosan-ionic liquid (CS-IL) conjugation for anion adsorption. Specifically, CS-IL conjugation was synthesized through the reaction of amino groups of chitosan with carboxylic groups of 1-carboxybutyl-3-methylimidazolium chloride. Due to the amphiphilic structure, CS-IL conjugation could self-assemble into nanoparticles in distilled water. This novel chitosan derivative revealed good anion adsorption performance, and the adsorption capacity of Cr2O7(2-) and PF6(-) was 0.422 mmol/g and 0.840 mmol/g, respectively. The adsorption of Cr2O7(2-) and PF6(-) could be improved at low pH, which was ascribed to the adsorption of protonated NH2 on chitosan. Importantly, the chitosan derivative would aggregate in the water after the adsorption and could be easily separated. The properties enable CS-IL conjugation to be used as a novel anion adsorbent for wastewater treatment. PMID:24076195

Wei, Yanqi; Huang, Wei; Zhou, Yuan; Zhang, Shuang; Hua, Daoben; Zhu, Xiulin

2013-11-01

120

Chemical modification of N6-(N-threonylcarbonyl) adenosine. Part II. Condensation of the carboxyl group with amines.  

PubMed

Carboxyl group of N6-/N-threonylcarbonyl/adenosine was quantitatively modified with amines/aniline, glycine ethyl ester and ethylenediamine/in the presence of a water-soluble carbodiimide, yielding the respective amides. The reaction was carried out in a water solution of pH about 4 at 20 degrees C and was finished within minutes. The structure of the products was confirmed by UV and PMR spectra, and by chemical reactivity. Under conditions applied for modification of T6A, four common nucleosides and internucleotide linkage of UpA were unreactive, while 5'-AMP was transformed to the respective phosphoramides. At pH 4, the rate of 5'-AMP modification was over 100 times lower than the rate of t6A reaction. PMID:503865

Krzyzosiak, W J; Biernat, J; Ciesio?ka, J; Górnicki, P; Wiewiórowski, M

1979-11-24

121

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

122

Functional Oligomerization of the Saccharomyces cerevisiae Isoprenylcysteine Carboxyl Methyltransferase, Ste14p  

PubMed Central

The isoprenylcysteine carboxyl methyltransferase (Icmt) from Saccharomyces cerevisiae, also designated Ste14p, is a 26-kDa integral membrane protein that contains six transmembrane spanning segments. This protein is localized to the endoplasmic reticulum membrane where it performs the methylation step of the CAAX post-translational processing pathway. Sequence analysis reveals a putative GXXXG dimerization motif located in transmembrane 1 of Ste14p, but it is not known whether Ste14p forms or functions as a dimer or higher order oligomer. We determined that Ste14p predominantly formed a homodimer in the presence of the cross-linking agent, bis-sulfosuccinimidyl suberate. Wild-type untagged Ste14p also co-immunoprecipitated and co-purified with N-terminal-tagged His10-myc3-Ste14p (His-Ste14p). Furthermore, enzymatically inactive His-Ste14p variants L81F and E213Q both exerted a dominant-negative effect on methyltransferase activity when co-expressed and co-purified with untagged wild-type Ste14p. Together, these data, although indirect, suggest that Ste14p forms and functions as a homodimer or perhaps a higher oligomeric species.

Griggs, Amy M.; Hahne, Kalub; Hrycyna, Christine A.

2010-01-01

123

Spherical functions on affine Lie groups  

Microsoft Academic Search

We describe vector valued conjugacy equivariant functions on a group K in two\\u000acases -- K is a compact simple Lie group, and K is an affine Lie group.\\u000a We construct such functions as weighted traces of certain intertwining\\u000aoperators between representations of K. For a compact group $K$, Peter-Weyl\\u000atheorem implies that all equivariant functions can be written as

Pavel I. Etingof; Igor B. Frenkel; Kirillov Jr. Alexander A

1995-01-01

124

Contributions of functional groups and extracellular polymeric substances on the biosorption of dyes by aerobic granules.  

PubMed

The contributions of loosely bound extracellular polymeric substances (LB-EPS), tightly bound EPS (TB-EPS), residual sludge (the sludge left after EPS extraction) and functional groups such as amine, carboxyl, phosphate and lipid on aerobic granules on biosorption of four different dyes (Reactive Brilliant Blue KN-R (KN-R), Congo Red (CR), Reactive Brilliant Red K-2G (RBR) and Malachite Green (MG)) were investigated. EPS may be responsible for biosorption of cationic dyes. However, residual sludge always made greater contribution than that of EPS. The biosorption mechanisms were dependent on the functional groups on aerobic granules and dyes' chemical structures. The lipid and phosphate groups might be the main binding sites for KN-R biosorption. Amine, carboxyl, phosphate and lipid were all responsible for the binding of CR. The lipid fractions played an important role for RBR biosorption. For MG, the phosphate groups gave the largest contribution. PMID:20869236

Gao, Jing-Feng; Zhang, Qian; Wang, Jin-Hui; Wu, Xue-Lei; Wang, Shu-Ying; Peng, Yong-Zhen

2011-01-01

125

Photophysical properties of lanthanide hybrids covalently bonded to functionalized MCM-41 by modified aromatic carboxylic acids.  

PubMed

MCM-41 mesoporous silica has been functionalized with aromatic carboxylic acids salicylic acid (Sal) and 2-hydroxyl-3-methylbenzoic acid (HMBA) through co-condensation approach of tetraethoxysilane (TEOS) in the presence of the cetyltrimethylammonium bromide (CTAB) surfactant as a template. Organic ligands salicylic acid or 2-hydroxyl-3-methylbenzoic acid grafted to the coupling agent 3-(triethoxysilyl)-propyl isocyanate (TEPIC) was used as the precursor for the preparation of an organic-inorganic hybrid materials. Novel organic-inorganic mesoporous luminescent hybrid containing Ln(3+) (Tb(3+), Eu(3+)) complexes covalently attached to the functionalized ordered mesoporous MCM-41, which were designated as Ln-Sal-MCM-41 and Ln-HMBA-MCM-41, respectively, were obtained by sol-gel process. The luminescence properties of these resulting materials were characterized in detail, and the results reveal that luminescent mesoporous materials have high surface area, uniformity in the mesopore structure and good crystallinity. Moreover, the mesoporous material covalently bonded Tb(3+) complex (Tb-Sal-MCM-41 and Tb-HMBA-MCM-41) exhibit the stronger characteristic emission of Tb(3+) and longer lifetime than the corresponding Eu-containing materials Eu-Sal-MCM-41 and Eu-HMBA-MCM-41 due to the triplet state energy of modified organic ligands Sal-TEPIC and HMBA-TEPIC match with the emissive energy level of Tb(3+) very well. In addition, the luminescence lifetime and emission quantum efficiency of (5)D(0) Eu(3+) excited state also indicates the efficient intramolecular energy transfer process in Tb-SAL-MCM-41 and Tb-HMBA-MCM-41. PMID:18649125

Li, Ying; Yan, Bing

2009-03-01

126

Polymethyl methacrylate-co-methacrylic acid coatings with controllable concentration of surface carboxyl groups: A novel approach in fabrication of polymeric platforms for potential bio-diagnostic devices  

NASA Astrophysics Data System (ADS)

The generally accepted strategy in development of bio-diagnostic devices is to immobilize proteins on polymeric surfaces as a part of detection process for diseases and viruses through antibody/antigen coupling. In that perspective, polymer surface properties such as concentration of functional groups must be closely controlled in order to preserve the protein activity. In order to improve the surface characteristics of transparent polymethacrylate plastics that are used for diagnostic devices, we have developed an effective fabrication procedure of polymethylmetacrylate-co-metacrylic acid (PMMA-co-MAA) coatings with controlled number of surface carboxyl groups. The polymers were processed effectively with the spin-coating technique and the detailed control over surface properties is here by demonstrated through the variation of a single synthesis reaction parameter. The chemical structure of synthesized and processed co-polymers has been investigated with nuclear magnetic resonance spectroscopy (NMR) and matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-ToF-MS). The surface morphology of polymer coatings have been analyzed with atomic force microscopy (AFM) and scanning electron microscopy (SEM). We demonstrate that the surface morphology and the concentration of surface -COOH groups (determined with UV-vis surface titration) on the processed PMMA-co-MAA coatings can be precisely controlled by variation of initial molar ratio of reactants in the free-radical polymerization reaction. The wettability of developed polymer surfaces also varies with macromolecular structure.

Hosseini, Samira; Ibrahim, Fatimah; Djordjevic, Ivan; Koole, Leo H.

2014-05-01

127

A simple colorimetric chemosensor bearing a carboxylic acid group with high selectivity for CN(-).  

PubMed

A new simple 'naked eye' chemosensor 1 (sodium (E)-2-((2-(3-hydroxy-2-naphthoyl)hydrazono)methyl)benzoate) has been synthesized for detection of CN(-) in a mixture of DMF/H2O (9:1). The sensor 1 comprises of a naphthoic hydrazide as efficient hydrogen bonding donor group and a benzoic acid as the moiety with the water solubility. The receptor 1 showed high selectivity toward cyanide ions in a 1:1 stoichiometric manner, which induces a fast color change from colorless to yellow for CN(-) over other anions. Therefore, receptor 1 could be useful for cyanide detection in aqueous environment, displaying a high distinguishable selectivity from hydrogen bonded anions and being clearly visible to the naked eye. PMID:24971717

Park, Gyeong Jin; Choi, Ye Won; Lee, Dongkuk; Kim, Cheal

2014-11-11

128

Surface functional groups of carbon nanotubes to manipulate capacitive behaviors  

NASA Astrophysics Data System (ADS)

The covalent functionalization of carbon nanotubes (CNTs) is a basic but important chemistry that can modify their physicochemical properties, resolve their poor dispersion capability, and improve their capacitance to enable their use as high-energy supercapacitors. However, the relationship between functional groups on the CNT surface and their capacitive characteristics has not yet been explored. Here, we demonstrate the influence of carboxylic, sulfonic, and amine groups tethered to CNTs (Cf-CNTs, Sf-CNTs, and Nf-CNTs, respectively) on capacitor performance in an organic electrolyte. The Cf-CNTs show the highest specific capacitance of 129.4 F g-1, four-fold greater than 31.2 F g-1 of pristine CNTs, but they reveal the lowest rate capability of 57%. In contrast, the Sf- and Nf-CNTs exhibit specific capacitances of 70.9 F g-1 and 83.6 F g-1, two-fold greater than that of pristine CNTs, along with a good rate capability greater than 80%. Despite their pseudocapacitive nature, all functionalized CNTs show a cyclic stability of more than 80% after 500 cycles due to the electrochemical stability of the functional groups. As demonstrated by spectroscopic analysis, the supercapacitive behaviors of the functionalized CNTs originate from specific interactions between functional groups and lithium ions and the alteration of the electronic structure arising from covalent functionalization.The covalent functionalization of carbon nanotubes (CNTs) is a basic but important chemistry that can modify their physicochemical properties, resolve their poor dispersion capability, and improve their capacitance to enable their use as high-energy supercapacitors. However, the relationship between functional groups on the CNT surface and their capacitive characteristics has not yet been explored. Here, we demonstrate the influence of carboxylic, sulfonic, and amine groups tethered to CNTs (Cf-CNTs, Sf-CNTs, and Nf-CNTs, respectively) on capacitor performance in an organic electrolyte. The Cf-CNTs show the highest specific capacitance of 129.4 F g-1, four-fold greater than 31.2 F g-1 of pristine CNTs, but they reveal the lowest rate capability of 57%. In contrast, the Sf- and Nf-CNTs exhibit specific capacitances of 70.9 F g-1 and 83.6 F g-1, two-fold greater than that of pristine CNTs, along with a good rate capability greater than 80%. Despite their pseudocapacitive nature, all functionalized CNTs show a cyclic stability of more than 80% after 500 cycles due to the electrochemical stability of the functional groups. As demonstrated by spectroscopic analysis, the supercapacitive behaviors of the functionalized CNTs originate from specific interactions between functional groups and lithium ions and the alteration of the electronic structure arising from covalent functionalization. Electronic supplementary information (ESI) available: Optical images, XPS spectra, N2 adsorption/desorption isotherms, CV curves, and impedance spectra. See DOI: 10.1039/c3nr04858f

Park, Sul Ki; Mahmood, Qasim; Park, Ho Seok

2013-11-01

129

Scanning thermal lithography of tailored tert-butyl ester protected carboxylic acid functionalized (meth)acrylate polymer platforms.  

PubMed

In this paper, we report on the development of tailored polymer films for high-resolution atomic force microscopy based scanning thermal lithography (SThL). In particular, full control of surface chemical and topographical structuring was sought. Thin cross-linked films comprising poly(tert-butyl methacrylate) (MA(20)) or poly(tert-butyl acrylate) (A(20)) were prepared via UV initiated free radical polymerization. Thermogravimetric analysis (TGA) and FTIR spectroscopy showed that the heat-induced thermal decomposition of MA(20) by oxidative depolymerization is initially the primary reaction followed by tert-butyl ester thermolysis. By contrast, no significant depolymerization was observed for A(20). For A(20) and MA(20) (at higher temperatures and/or longer reaction times) the thermolysis of the tert-butyl ester liberates isobutylene and yields carboxylic acid groups, which react further intramolecularly to cyclic anhydrides. The values of the apparent activation energies (E(a)) for the thermolysis were calculated to be 125 ± 13 kJ mol(-1) and 116 ± 7 kJ mol(-1) for MA(20) and A(20), respectively. Both MA(20) and A(20) films showed improved thermomechanical stability during SThL compared to non cross-linked films. Carboxylic acid functionalized lines written by SThL in A(20) films had a typically ~10 times smaller width compared to those written in MA(20) films regardless of the tip radius of the heated probe and did not show any evidence for thermochemically or thermomechanically induced modification of film topography. These observations and the E(a) of 45 ± 3 kJ mol(-1) for groove formation in MA(20) estimated from the observed volume loss are attributed to oxidative thermal depolymerization during SThL of MA(20) films, which is considered to be the dominant reaction mechanism for MA(20). The smallest line width values obtained for MA(20) and A(20) films with SThL were 83 ± 7 nm and 21 ± 2 nm, whereas the depth of the lines was below 1 nm, respectively. PMID:21919505

Duvigneau, Joost; Schönherr, Holger; Vancso, G Julius

2011-10-01

130

Synthesis and Functionalization of Cyclic Sulfonimidamides: A Novel Chiral Heterocyclic Carboxylic Acid Bioisostere  

PubMed Central

An efficient synthesis of aryl substituted cyclic sulfonimidamides designed as chiral nonplanar heterocyclic carboxylic acid bioisosteres is described. The cyclic sulfonimidamide ring system could be prepared in two steps from a trifluoroacetyl protected sulfinamide and methyl ester protected amino acids. By varying the amino acid, a range of different C-3 substituted sulfonimidamides could be prepared. The compounds could be further derivatized in the aryl ring using standard cross-coupling reactions to yield highly substituted cyclic sulfonimidamides in excellent yields. The physicochemical properties of the final compounds were examined and compared to those of the corresponding carboxylic acid and tetrazole derivatives. The unique nonplanar shape in combination with the relatively strong acidity (pKa 5–6) and the ease of modifying the chemical structure to fine-tune the physicochemical properties suggest that this heterocycle can be a valuable addition to the range of available carboxylic acid isosteres.

2012-01-01

131

Importance of Having Low-Density Functional Groups for Generating High-Performance Semiconducting Polymer Dots  

PubMed Central

Semiconducting polymers with low-density side-chain carboxylic acid groups were synthesized to form stable, functionalized, and highly fluorescent polymer dots (Pdots). The influence of the molar fraction of hydrophilic side-chains on Pdot properties and performance was systematically investigated. Our results show that the density of side-chain carboxylic acid groups significantly affects Pdot stability, internal structure, fluorescence brightness, and nonspecific binding in cellular labeling. Fluorescence spectroscopy, single-particle imaging, and a dye-doping method were employed to investigate the fluorescence brightness and the internal structure of the Pdots. The results of these experiments indicate that semiconducting polymers with low density of side-chain functional groups can form stable, compact, and highly bright Pdots as compared to those with high density of hydrophilic side-chains. The functionalized polymer dots were conjugated to streptavidin (SA) by carbodiimide-catalyzed coupling and the Pdot-SA probes effectively and specifically labeled the cancer cell-surface marker Her2 in human breast cancer cells. The carboxylate-functionalized polymer could also be covalently modified with small functional molecules to generate Pdot probes for click chemistry-based bioorthogonal labeling. This study presents a promising approach for further developing functional Pdot probes for biological applications.

Zhang, Xuanjun; Yu, Jiangbo; Wu, Changfeng; Jin, Yuhui; Rong, Yu; Ye, Fangmao

2012-01-01

132

A complex of cyclohexane-1,2-diaminoplatinum with an amphiphilic biodegradable polymer with pendant carboxyl groups.  

PubMed

A biodegradable and amphiphilic copolymer, MPEG-b-P(LA-co-MCC), which contains pendant carboxyl groups, was chosen as a drug carrier for the active anticancer part (DACH-Pt) of oxaliplatin to form an MPEG-b-P(LA-co-MCC/Pt) complex. It was able to self-assemble into micelles with a mean diameter of 30-40 nm, and a surface potential near -10 mV. The typical platinum content was 10 wt.%. The micelles showed acid-responsive drug release kinetics, which is beneficial for drug release in the intracellular environment. The Pt(II) species were released mainly in the form of DACH-Pt-Cl(2) in 150 mM NaCl solution and DACH-Pt(2+)-(H(2)O)(2) in pure water according to the results obtained by high-performance liquid chromatography coupled with inductively coupled plasma mass spectrometry and X-ray photoelectron spectroscopy. In vitro evaluation showed that the micelles displayed the same or higher cytotoxicities against SKOV-3, HeLa, and EC-109 cancer cells compared with oxaliplatin. The enhanced cytotoxicity against SKOV-3 cells is attributed to effective internalization of the micelles by the cells via endocytosis and the sensitivity of SKOV-3 cells to platinum drugs. This novel biodegradable and amphiphilic copolymer-based platinum drug will have great potential application in clinical use. PMID:22281944

Xiao, Haihua; Zhou, Dongfang; Liu, Shi; Zheng, Yonghui; Huang, Yubin; Jing, Xiabin

2012-05-01

133

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

134

Floral benzenoid carboxyl methyltransferases: From in vitro to in planta function  

PubMed Central

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 planta 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, Uta; Saschenbrecker, Sandra; Ross, Jeannine; Negre, Florence; Fraser, Chris M.; Noel, Joseph P.; Dudareva, Natalia; Piechulla, Birgit

2010-01-01

135

Synthesis, structure, and reactivity of transition-metal\\/main-group-metal bridging carboxylate complexes of the formula (eta⁵-CâHâ)Re(NO)(PPhâ)(COâML\\/sub n\\/)(M = Li, K, Ge, Sn, Pb)  

Microsoft Academic Search

The synthesis of the rhenium\\/main-group-metal bridging COâ or carboxylate complexes of the formula (eta⁵-CâHâ)Re(NO)(PPhâ)(COâML\\/sub n\\/) where M = Li, K, Ge, Sn, or Pb from the rhenium carboxylic acid (eta⁵-CâHâ)Re(NO)(PPhâ)(COOH) is reported. The molecular structure of the complexes was investigated, and both monodentate and bidentate carboxylate binding modes were observed with the symmetrical bidentate binding in the tin complex being

D. R. Senn; J. A. Gladysz; K. E. Emerson; R. D. Larsen

1987-01-01

136

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

137

In-depth structural characterization of N-linked glycopeptides using complete derivatization for carboxyl groups followed by positive- and negative-ion tandem mass spectrometry.  

PubMed

Tandem mass spectrometry (MS/MS or MS(n)) is a powerful tool for characterizing N-linked glycopeptide structures. However, it is still difficult to obtain detailed structural information on the glycan moiety directly from glycopeptide ions. Here, we propose a new method for in-depth analysis of the glycopeptide structure using MS/MS. This method involves complete derivatization of carboxyl groups in glycopeptides. Methylamidation using PyAOP as a condensing reagent has been optimized for derivatizing all carboxyl groups in glycopeptides. By derivatizing carboxyl groups on the peptide moiety (i.e., Asp, Glu, and C-terminus), the glycopeptides efficiently produce informative glycan fragment ions, including the nonreducing end of the glycan moiety under negative-ion collision-induced dissociation (CID) conditions. These glycan fragment ions can define detailed structural features on the glycan moiety (e.g., the specific composition of the two antennae, the location of fucose residues, and the presence/absence of bisecting GlcNAc residues). For sialylated glycopeptides, carboxyl groups on sialic acid residues are simultaneously derivatized using methylamidation, suppressing preferential loss of residues during MS analysis. As a result, both sialylated and nonsialylated glycopeptides can be analyzed in the same manner. Positive-ion CID of methylamine-derivatized glycopeptides mainly provides information on peptide sequence and glycan composition, whereas negative-ion CID provides in-depth structural information on the glycan moiety. The derivatization step can be readily incorporated into conventional pretreatment for glycopeptide MS analysis without loss of sensitivity, making derivatization suitable for practical use. PMID:24773001

Nishikaze, Takashi; Kawabata, Shin-ichirou; Tanaka, Koichi

2014-06-01

138

A rapid and sensitive method for the simultaneous analysis of aliphatic and polar molecules containing free carboxyl groups in plant extracts by LC-MS/MS  

PubMed Central

Background Aliphatic molecules containing free carboxyl groups are important intermediates in many metabolic and signalling reactions, however, they accumulate to low levels in tissues and are not efficiently ionized by electrospray ionization (ESI) compared to more polar substances. Quantification of aliphatic molecules becomes therefore difficult when small amounts of tissue are available for analysis. Traditional methods for analysis of these molecules require purification or enrichment steps, which are onerous when multiple samples need to be analyzed. In contrast to aliphatic molecules, more polar substances containing free carboxyl groups such as some phytohormones are efficiently ionized by ESI and suitable for analysis by LC-MS/MS. Thus, the development of a method with which aliphatic and polar molecules -which their unmodified forms differ dramatically in their efficiencies of ionization by ESI- can be simultaneously detected with similar sensitivities would substantially simplify the analysis of complex biological matrices. Results A simple, rapid, specific and sensitive method for the simultaneous detection and quantification of free aliphatic molecules (e.g., free fatty acids (FFA)) and small polar molecules (e.g., jasmonic acid (JA), salicylic acid (SA)) containing free carboxyl groups by direct derivatization of leaf extracts with Picolinyl reagent followed by LC-MS/MS analysis is presented. The presence of the N atom in the esterified pyridine moiety allowed the efficient ionization of 25 compounds tested irrespective of their chemical structure. The method was validated by comparing the results obtained after analysis of Nicotiana attenuata leaf material with previously described analytical methods. Conclusion The method presented was used to detect 16 compounds in leaf extracts of N. attenuata plants. Importantly, the method can be adapted based on the specific analytes of interest with the only consideration that the molecules must contain at least one free carboxyl group.

2009-01-01

139

Reaction of carboxylic groups containing organic layers with the surface of a ZnSe internal reflection element during high-energy processes  

Microsoft Academic Search

The aim of this FTIR study was to get information about the reactivity of plasma-deposited organic layers on a ZnSe-ATR probe by means of modification experiments using organic layers with carboxyl groups as model compounds. The model layers prepared on ZnSe internal reflection elements were exposed both to a low pressure plasma in a reactor (generation of ultraviolet radiation: ?=100–400

K Sahre; K.-J Eichhorn

1997-01-01

140

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

PubMed

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. PMID:21317360

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

2011-03-01

141

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

142

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

143

A luminescent ionogel based on an europium(iii)-coordinated carboxyl-functionalized ionic liquid and gelatin.  

PubMed

In this work, we report the preparation and luminescent properties of a novel luminescent ionogel consisting of a carboxyl-functionalized ionic liquid, Eu(3+) ions and gelatin. The obtained ionogel was investigated by FT-IR, SEM and photoluminescence spectroscopy. FT-IR spectra show that both the ionic liquid and the gelatin are coordinated to Eu(3+) ions through oxygen atoms. Luminescence data confirm that Eu(3+) ions are well-protected by the ionic liquid and gelatin from deleterious quenching interactions with water molecules. PMID:24770347

Li, Man; Wang, Yige; Chen, Yuhuan; Zhang, Shuming

2014-07-18

144

Group entropies, correlation laws, and zeta functions.  

PubMed

The notion of group entropy is proposed. It enables the unification and generaliztion of many different definitions of entropy known in the literature, such as those of Boltzmann-Gibbs, Tsallis, Abe, and Kaniadakis. Other entropic functionals are introduced, related to nontrivial correlation laws characterizing universality classes of systems out of equilibrium when the dynamics is weakly chaotic. The associated thermostatistics are discussed. The mathematical structure underlying our construction is that of formal group theory, which provides the general structure of the correlations among particles and dictates the associated entropic functionals. As an example of application, the role of group entropies in information theory is illustrated and generalizations of the Kullback-Leibler divergence are proposed. A new connection between statistical mechanics and zeta functions is established. In particular, Tsallis entropy is related to the classical Riemann zeta function. PMID:21928963

Tempesta, Piergiulio

2011-08-01

145

Group entropies, correlation laws, and zeta functions  

NASA Astrophysics Data System (ADS)

The notion of group entropy is proposed. It enables the unification and generaliztion of many different definitions of entropy known in the literature, such as those of Boltzmann-Gibbs, Tsallis, Abe, and Kaniadakis. Other entropic functionals are introduced, related to nontrivial correlation laws characterizing universality classes of systems out of equilibrium when the dynamics is weakly chaotic. The associated thermostatistics are discussed. The mathematical structure underlying our construction is that of formal group theory, which provides the general structure of the correlations among particles and dictates the associated entropic functionals. As an example of application, the role of group entropies in information theory is illustrated and generalizations of the Kullback-Leibler divergence are proposed. A new connection between statistical mechanics and zeta functions is established. In particular, Tsallis entropy is related to the classical Riemann zeta function.

Tempesta, Piergiulio

2011-08-01

146

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

2012-09-13

147

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

148

Extremely fast gas/liquid reactions in flow microreactors: carboxylation of short-lived organolithiums.  

PubMed

Carboxylation of short-lived organolithiums bearing electrophilic functional groups such as nitro, cyano, and alkoxycarbonyl groups with CO2 to give carboxylic acids and active esters was accomplished in a flow microreactor system. The successful reactions indicate that gas/liquid mass transfer and the subsequent chemical reaction with CO2 are extremely fast. PMID:24863501

Nagaki, Aiichiro; Takahashi, Yusuke; Yoshida, Jun-Ichi

2014-06-23

149

Towards modelling the vibrational signatures of functionalized surfaces: carboxylic acids on H-Si(111) surfaces  

NASA Astrophysics Data System (ADS)

In this work, we investigate the adsorption process of two carboxylic acids (stearic and undecylenic) on a H-Si(111) surface via the calculation of structural and energy changes as well as the simulation of their IR and Raman spectra. The two molecules adsorb differently at the surface since the stearic acid simply physisorbs while the undecylenic acid undergoes a chemical reaction with the hydrogen atoms of the surface. This difference is observed in the change of geometry during the adsorption. Indeed, the chemisorption of the undecylenic acid has a bigger impact on the structure than the physisorption of the stearic acid. Consistently, the former is also characterized by a larger value of adsorption energy and a smaller value of the tilting angle with respect to the normal plane. For both the IR and Raman signatures, the spectra of both molecules adsorbed at the surface are in a first approximation the superposition of the spectra of the Si cluster and of the carboxylic acid considered individually. The main deviation from this simple observation is the peak of the stretching Si-H (?(Si-H)) mode, which is split into two peaks upon adsorption. As expected, the splitting is bigger for the chemisorption than the physisorption. The modes corresponding to atomic displacements close to the adsorption site display a frequency upshift by a dozen wavenumbers. One can also see the disappearance of the peaks associated with the C=C double bond when the undecylenic acid chemisorbs at the surface. The Raman and IR spectra are complementary and one can observe here that the most active Raman modes are generally IR inactive. Two exceptions to this are the two ?(Si-H) modes which are active in both spectroscopies. Finally, we compare our simulated spectra with some experimental measurements and we find an overall good agreement.

Giresse Tetsassi Feugmo, Conrard; Champagne, Benoît; Caudano, Yves; Cecchet, Francesca; Chabal, Yves J.; Liégeois, Vincent

2012-03-01

150

Electromigration of bivalent functional groups on graphene  

NASA Astrophysics Data System (ADS)

Chemical functionalization of graphene holds promise for various applications ranging from nanoelectronics to catalysis, drug delivery, and nanoassembly. In many of these applications, it is critical to assess the rates of electromigration-directed motion of adsorbates along the surface of current-carrying graphene due to the electron wind force. In this paper, we develop an accurate analytical theory of electromigration of bivalent functional groups (epoxide, amine) on graphene. Specifically, we carefully analyze various factors contributing to the electron wind force, such as lattice effects and strong scattering beyond Born approximation, and derive a simple analytical expression for this force. Further, we perform accurate electronic-structure-theory calculations to parametrize the obtained analytical expression. The obtained results can be generalized to different functional groups and adsorbates, e.g., alkali atoms on graphene.

Velizhanin, Kirill A.; Dandu, Naveen; Solenov, Dmitry

2014-04-01

151

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

152

Intramolecular hydrogen bond between 4-oxo and 3-carboxylic groups in quinolones and their analogs. Crystal structures of 7-methyl- and 6-fluoro-1,4-dihydro-4-oxocinnoline-3-carboxylic acids  

NASA Astrophysics Data System (ADS)

Crystal structures of two cinnoline analogs of quinolones and statistics on quinolones molecular forms observed in the crystal state have been determined. It has been shown that common quinolones may be divided into two main types, depending on presence of proton acceptor, usually aliphatic amine group, capable of protonation under mild conditions. Quinolones lacking amine group or having one(s) bound to an aromatic system exist at physiological pH mainly in a free acid form, in which acidic hydrogen atom is locked into an intramolecular hydrogen bond. The phenomenon enhances permeability of quinolones through lipophilic cell membranes but decreases the concentration of carboxylate form capable of specific binding with bacterial DNA. Molecular (neutral) form was observed exclusively in the crystalline state for these quinolones. The dominant forms seem different for quinolones having amine substituents with unconjugated lone pair electrons at N atom. Even in the crystalline state, they may exist also in a zwitterionic form, which was found to dominate in secondary amines crystallised at neutral pH. Our limited data suggest that position and order of amine group may play important role in controlling quinolones absorption, transport and concentration and thus their biological profile.

G?ówka, Marek L.; Martynowski, Dariusz; Olczak, Andrzej; Bojarska, Joanna; Szczesio, Ma?gorzata; Koz?owska, Krystyna

2003-09-01

153

Preparation and surface characterization of functional group-grafted and heparin-immobilized polyurethanes by plasma glow discharge  

Microsoft Academic Search

Functional group-grafted polyurethanes were prepared by oxygen plasma discharge treatment, followed by graft polymerization of 1-acryloylbenzotriazole (AB) and a subsequent substitution reaction of AB with sodium hydroxide and ethylene diamine. The primary amine or carboxylic acid groups grafted on the surfaces were coupled with heparin using water-soluble carbodiimide. The modified surfaces were characterized by measuring the water contact angle, electron

Inn-Kyu Kang; Oh Hyeong Kwon; Young Moo Lee; Yong Kiel Sung

1996-01-01

154

Copper-catalyzed aerobic oxidative synthesis of aromatic carboxylic acids.  

PubMed

A simple, practical and efficient copper-catalyzed method for synthesis of aromatic carboxylic acids has been developed. The protocol uses inexpensive CuI/L-proline as the catalyst/ligand, and readily available aryl halides and malononitrile as the starting materials, and the corresponding aromatic carboxylic acids were obtained in moderate to good yields. The method is of tolerance towards functional groups in the substrates. PMID:21152586

Yang, Daoshan; Yang, Haijun; Fu, Hua

2011-02-28

155

Capillary electrophoretic study of amine/carboxylic acid-functionalized carbon nanodots.  

PubMed

Capillary zone electrophoresis (CZE) coupled with UV absorption and laser-induced fluorescence detections has been applied to study the complexity of carbon nanodots (C-dots) products synthesized with microwave-assisted pyrolysis of citric acid (CA) and 1,2-ethylenediamine (EDA). The effects of pH and concentration of run buffer on the CZE separation of C-dots are studied in detail. The optimal acetate run buffer (30mM, pH 3.6) is subsequently employed to investigate the effect of reaction time and mole ratio of amine (NH2) to carboxylic acid (COOH) moieties of the precursors on the C-dots species present in C-dots products. Our results confirm that the synthesis of C-dots could be improved by lengthening the microwave irradiation time and optimizing the initial mole ratio of NH2/COOH in the precursors. Negatively charged C-dots are obtained only when the amount of CA exceeds that of EDA, i.e., the mole ratio of NH2/COOH is 0.25-0.80. By contrast, when the quantity (mole) of NH2 in EDA is equal to or larger than that of COOH in CA, only positively charged and neutral C-dots species are formed, inferring that the C-dots species are predominantly covered by the surface-attached ammonium and amido moieties. This work highlights the merit of CZE to identify the composition of an as-prepared C-dots product which is pretty much dependent on the mole ratio of NH2/COOH. It is anticipated that our CZE methodology will open a new avenue in optimizing the synthetic conditions for producing specific C-dots of desired composition. PMID:23885674

Hu, Qin; Paau, Man Chin; Zhang, Yan; Chan, Wan; Gong, Xiaojuan; Zhang, Lei; Choi, Martin M F

2013-08-23

156

Aspects of the functional renormalisation group  

SciTech Connect

We discuss structural aspects of the functional renormalisation group. Flows for a general class of correlation functions are derived, and it is shown how symmetry relations of the underlying theory are lifted to the regularised theory. A simple equation for the flow of these relations is provided. The setting includes general flows in the presence of composite operators and their relation to standard flows, an important example being NPI quantities. We discuss optimisation and derive a functional optimisation criterion. Applications deal with the interrelation between functional flows and the quantum equations of motion, general Dyson-Schwinger equations. We discuss the combined use of these functional equations as well as outlining the construction of practical renormalisation schemes, also valid in the presence of composite operators. Furthermore, the formalism is used to derive various representations of modified symmetry relations in gauge theories, as well as to discuss gauge-invariant flows. We close with the construction and analysis of truncation schemes in view of practical optimisation.

Pawlowski, Jan M. [Institut fuer Theoretische Physik, Universitaet Heidelberg, Philosophenweg 16, D-69120 Heidelberg (Germany)], E-mail: j.pawlowski@thphys.uni-heidelberg.de

2007-12-15

157

New photoremovable protecting groups for carboxylic acids with high photolytic efficiencies at near-UV irradiation. Application to the photocontrolled release of L-glutamate.  

PubMed

We report here the syntheses and the photolytic properties of 3-(4,5-dimethoxy-2-nitrophenyl)-2-butyl (DMNPB) esters as new photoremovable groups for carboxylic acids, and their use for the caging of L-glutamate. A high-yielding synthesis of the DMNPB esters led to a 4:1 threo/erythro diastereomeric mixture, which could be separated by HPLC. While these esters were stable in neutral buffer, photolysis at 364 nm induced a > or =95 % release of the carboxylic acid, with a 0.26 quantum yield for L-glutamate formation. L-Glutamate release was also possible by two-photon photolysis with an action cross section of 0.17 GM at 720 nm. Laser photolysis at 350 nm generated a transient species at around 410 nm, attributed to a quinonoid aci-nitro intermediate that decayed in the submillisecond time range (t(1/2)=0.53 ms) for the faster gamma-L-glutamyl threo-esters. Given the absorbance of these esters (lambda(max)=350 nm; epsilon=4500), the threo DMNPB esters represent new caging groups that can be efficiently photolyzed at near-UV wavelengths. An efficient and rapid photolytic release of L-glutamate has been demonstrated on hippocampal neurons in primary culture. PMID:16991166

Specht, Alexandre; Thomann, Jean-Sébastien; Alarcon, Karine; Wittayanan, Weerawut; Ogden, David; Furuta, Toshiaki; Kurakawa, Yuji; Goeldner, Maurice

2006-11-01

158

POLYCOMB GROUP COMPLEXES - MANY COMBINATIONS, MANY FUNCTIONS  

PubMed Central

Polycomb Group (PcG) proteins are transcription regulatory proteins that control the expression of a variety of genes from early embryogenesis through birth to adulthood. PcG proteins form several complexes that are thought to collaborate to repress gene transcription. Individual PcG proteins have unique characteristics and mutations in genes encoding different PcG proteins cause distinct phenotypes. Histone modifications have important roles in some PcG protein functions, but they are not universally required. The mechanisms of gene-specific recruitment, transcription repression, and selective derepression of genes by vertebrate PcG proteins are incompletely understood. Future studies of this enigmatic group of developmental regulators are certain to produce unanticipated discoveries.

Kerppola, Tom K

2010-01-01

159

The galaxy luminosity function around groups  

NASA Astrophysics Data System (ADS)

We present a study on the variations of the luminosity function of galaxies around clusters in a numerical simulation with semi-analytic galaxies, attempting to detect these variations in the 2dF Galaxy Redshift Survey. We subdivide the simulation box into equal-density regions around clusters, which we assume can be achieved by selecting objects at a given normalized distance (r/rrms, where rrms is an estimate of the halo radius) from the group centre. The semi-analytic model predicts important variations in the luminosity function out to r/rrms~= 5. In brief, variations in the mass function of haloes around clusters (large dark matter haloes with M > 1012h-1Msolar) lead to cluster central regions that present a high abundance of bright galaxies (high M* values) as well as low-luminosity galaxies (high ?) at r/rrms~= 3 there is a lack of bright galaxies, which shows the depletion of galaxies in the regions surrounding clusters (minimum in M* and ?), and a tendency to constant luminosity function parameters at larger cluster-centric distances. We take into account the observational biases present in the real data by reproducing the peculiar velocity effect on the redshifts of galaxies in the simulation box, and also by producing mock catalogues. We find that excluding from the analysis galaxies which in projection are close to the centres of the groups provides results that are qualitatively consistent with the full simulation box results. When we apply this method to mock catalogues of the 2dF Galaxy Redshift Survey (2dFGRS) and the 2PIGG catalogue of groups, we find that the variations in the luminosity function are almost completely erased by the Finger of God effect; only a lack of bright galaxies at r/rrms~= 3 can be marginally detected in the mock catalogues. The results from the real 2dFGRS data show a clearer detection of a dip in M* and ? for r/rrms= 3, consistent with the semi-analytic predictions.

González, R. E.; Padilla, N. D.; Galaz, G.; Infante, L.

2005-11-01

160

Prediction of impact sensitivity of nitroaliphatic, nitroaliphatic containing other functional groups and nitrate explosives.  

PubMed

This paper describes a new method for prediction of impact sensitivity of nitroaliphatic, nitroaliphatic containing other functional groups and nitrate explosives. The new procedure is based on some structural parameters of C(a)H(b)N(c)O(d) explosives. Three essential parameters would be needed in this scheme which contain a+b/2-d and the number of nitrogens as well as the number of RC(NO(2))(2)CH(2) structural parameters attached to oxygen of carboxylate functional groups where R is alkyl groups. The results are compared with experimental data and some empirical correlations. Predicted impact sensitivities for 58 explosives have a root mean square (rms) of deviation from experiment of 27 cm, which show good agreement with respect to measured values as compared to previous empirical models. PMID:17434263

Keshavarz, Mohammad Hossein

2007-09-30

161

Modeling the hydrolysis of perfluorinated compounds containing carboxylic and phosphoric acid ester functions and sulfonamide groups  

Microsoft Academic Search

Temperature-dependent rate constants were estimated for the acid- and base-catalyzed and neutral hydrolysis reactions of perfluorinated telomer acrylates (FTAcrs) and phosphate esters (FTPEs), and the SN1 and SN2 hydrolysis reactions of fluorotelomer iodides (FTIs). Under some environmental conditions, hydrolysis of monomeric FTAcrs could be rapid (half-lives of several years in marine systems and as low as several days in some

Sierra Rayne; Kaya Forest

2010-01-01

162

Activation of the neutrophil NADPH-oxidase by free fatty acids requires the ionized carboxyl group and partitioning into membrane lipid.  

PubMed

To investigate NADPH-oxidase activation, we studied the effects of free fatty acid (FFA), their uncharged derivatives, and calcium on membrane lipid structure and superoxide anion (O2-) release from intact neutrophils and in cell-free O2(-)-generating systems. This study determined that in calcium-free phosphate-buffered saline (PBS), cis-unsaturated FFA (cis FFA), trans-unsaturated FFA (trans FFA), and to a limited extent saturated FFA decreased the polarization of the membrane lipid structure probe 1,6-diphenyl-1,3,5-hexatriene (DPH), and these decreases correlated with partitioning of the FFA into the plasmalemma and the release of O2- from intact neutrophils and in cell-free preparations. Although a decrease in DPH polarization was always observed under conditions that resulted in the release of O2-, there was not a direct correlation between the amount of decrease in DPH polarization and the release of O2-. Trans FFA did not induce a dose-dependent decrease or as dramatic a decrease in DPH polarization compared with cis FFA, yet the trans FFA stimulated a greater release of O2- at 2.5, 5, and 10 microM concentrations. In addition, responses of the neutrophil to trans FFA, but not cis FFA, were differentially affected by the presence of calcium. When 0.1 mM calcium was added to the PBS decreases in DPH polarization in response to trans FFA were reduced by greater than 60%, whereas O2- was reduced by only 25-36%. The addition of 0.1 mM calcium 3 min after the trans FFA had partitioned into the membrane also reversed by 50-65% decreases in DPH polarization but did not affect the release of O2-. In the presence of 0.9 mM calcium, only the cis FFA decreased DPH polarization or stimulated the release of O2-. Calcium is known to interact more readily with the ionized carboxyl group of trans FFA, neutralizing the anionic charge through an electrostatic interaction. In support of the requirement for the ionized carboxyl group, structurally similar uncharged cis, trans, and saturated fatty alcohols; methyl esters; and aldehydes decreased DPH polarization in the absence and presence of 0.9 mM calcium; however, none of these compounds stimulated the release of O2-. These results indicate that, in addition to the partitioning of FFA into the plasmalemma, which results in calcium-modulatable decreases in DPH polarization, activation or assembly of the NADPH-oxidase requires the ionized carboxyl group. PMID:1848271

Steinbeck, M J; Robinson, J M; Karnovsky, M J

1991-04-01

163

Tetraphenylsilane-containing polyarylates with well-defined functional groups via postpolymerization modification  

Microsoft Academic Search

New tetraphenylsilane-containing polyarylate with two pendant benzyl ester groups was synthesized successfully by direct polycondensation from a new silicon-containing aromatic diacid monomer bis[p-(benzyloxycarbonyl)phenyl]-bis(p-carboxyphenyl)silane (BBCS) with p-dihydroxybenzene in pyridine, using dimethylformamide as the activator and p-tosyl chloride as the condensing agent. Then, the benzyl ester groups were smoothly converted to carboxyl groups by catalytic hydrogenation, obtaining the polyarylate with two carboxyl

Bufeng Zhang; Zhonggang Wang; Zhanbin Wang; Jianfeng Li; Shiwei Leng; Changjiang Shen; Yiwen Jiang

2009-01-01

164

Role of functional groups in fiber in the binding of zinc  

SciTech Connect

The binding of zinc by purified cellulose, xylan, methylated xylan, pectin and methylated pectin was measured in vitro. Methylated xylan and methylated pectin were prepared chemically from xylan and pectin, respectively, to block hydroxyl and carboxyl groups. Comparison of zinc binding capacities was made between xylan and methylated xylan, and between pectin and methylated pectin to assess the role of the two functional groups in binding minerals. The binding of zinc was conducted at pH 2.6, 4.0, 5.4 and 6.8 in various concentrations of ZnSO/sub 4/ solution containing /sup 65/Zn using a dialysis system for water-soluble pectin and an incubation-centrifugation model for the other four water-insoluble fibers. The results showed that zinc binding by each fiber was pH dependent and it increased from pH 2.6 to 6.8 (p < 0.001). At pH 6.8, % Zn bound to fiber decreased as concentration of ZnSO/sub 4/ increased from 1 ..mu..M to 96 ..mu..M (p less than or equal to 0.01). mean zinc binding ratio of pectin to methylated xylan was 5.1, whereas the ratio of pectin t methylated pectin was only 1.7. This suggests that the hydroxyl group in xylan plays a more important role than the carboxyl group in pectin in the binding of zinc.

Jiang, K.

1986-03-01

165

Effects of Trehalose Polycation End-group Functionalization on Plasmid DNA Uptake and Transfection  

PubMed Central

In this study, we have synthesized six analogs of a trehalose-pentaethylenehexamine glycopolymer (Tr4) that contain (1A) adamantane, (1B) carboxy, (1C) alkynyl-oligoethyleneamine, (1D) azido trehalose, (1E) octyl, or (1F) oligoethyleneamine end groups and evaluated the effects of polymer end group chemistry on the ability of these systems to bind, compact, and deliver pDNA in cultured HeLa cells. The polymers were synthesized in one-pot azide-alkyne cycloaddition reactions with an adaptation of the Carothers equation for step-growth polymerization to produce a series of polymers with similar degrees of polymerization. An excess of end-capping monomer was added at the end of the polymerizations to maximize functionalization efficiency, which was evaluated with GPC, NMR and MALDI-TOF. The polymers were all found to bind and compact pDNA at similarly low N/P ratios and form polyplexes with plasmid DNA. The effects of the different end group structures were most evident in the polyplex internalization and transfection assays completed in the presence of serum, as determined by flow cytometry and luciferase gene expression respectively. The Tr4 polymers end-capped with carboxyl groups (1B) (N/P = 7), octyne (1E) (N/P = 7), and oligoethyleneamine (1F) (N/P = 7), were taken into cells as polyplex and exhibited the highest levels of fluorescence, resulting from labeled reporter plasmid. Similarly, the polymers end-functionalized with the carboxyl groups (1E at N/P = 7), octyl groups (1E at N/P = 15) and, in particular, the oligoethyleneamine groups (F at N/P = 15) yielded dramatically higher reporter gene expression in the presence of serum. This study yields insight into how very subtle structural changes in the polymer chemistry such as end groups can yield very significant differences in the biological delivery efficiency and transgene expression of polymers used for pDNA delivery.

Anderson, Kevin; Sizovs, Antons; Cortez, Mallory; Waldron, Chris; Haddleton, D.M.; Reineke, Theresa M.

2012-01-01

166

Carboxyl group footprinting mass spectrometry and molecular dynamics identify key interactions in the HER2-HER3 receptor tyrosine kinase interface.  

PubMed

The HER2 receptor tyrosine kinase is a driver oncogene in many human cancers, including breast and gastric cancer. Under physiologic levels of expression, HER2 heterodimerizes with other members of the EGF receptor/HER/ErbB family, and the HER2-HER3 dimer forms one of the most potent oncogenic receptor pairs. Previous structural biology studies have individually crystallized the kinase domains of HER2 and HER3, but the HER2-HER3 kinase domain heterodimer structure has yet to be solved. Using a reconstituted membrane system to form HER2-HER3 kinase domain heterodimers and carboxyl group footprinting mass spectrometry, we observed that HER2 and HER3 kinase domains preferentially form asymmetric heterodimers with HER3 and HER2 monomers occupying the donor and acceptor kinase positions, respectively. Conformational changes in the HER2 activation loop, as measured by changes in carboxyl group labeling, required both dimerization and nucleotide binding but did not require activation loop phosphorylation at Tyr-877. Molecular dynamics simulations on HER2-HER3 kinase dimers identify specific inter- and intramolecular interactions and were in good agreement with MS measurements. Specifically, several intermolecular ionic interactions between HER2 Lys-716-HER3 Glu-909, HER2 Glu-717-HER3 Lys-907, and HER2 Asp-871-HER3 Arg-948 were identified by molecular dynamics. We also evaluated the effect of the cancer-associated mutations HER2 D769H/D769Y, HER3 E909G, and HER3 R948K (also numbered HER3 E928G and R967K) on kinase activity in the context of this new structural model. This study provides valuable insights into the EGF receptor/HER/ErbB kinase structure and interactions, which can guide the design of future therapies. PMID:23843458

Collier, Timothy S; Diraviyam, Karthikeyan; Monsey, John; Shen, Wei; Sept, David; Bose, Ron

2013-08-30

167

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

168

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

169

Functional renormalization group for quantized anharmonic oscillator  

SciTech Connect

Highlights: > RG analysis with field dependent wavefunction renormalization. > The Taylor expansion does not work for the wavefunction renormalization. > The gap energy is RG scheme-dependent. > The O (N) symmetric anharmonic oscillator exhibits only a single phase. > The evolution equation for the 2PI effective action for the oscillator is solved. - Abstract: Functional renormalization group methods formulated in the real-time formalism are applied to the O(N) symmetric quantum anharmonic oscillator, considered as a 0 + 1 dimensional quantum field-theoric model, in the next-to-leading order of the gradient expansion of the one- and two-particle irreducible effective action. The infrared scaling laws and the sensitivity-matrix analysis show the existence of only a single, symmetric phase. The Taylor expansion for the local potential converges fast while it is found not to work for the field-dependent wavefunction renormalization, in particular for the double-well bare potential. Results for the gap energy for the bare anharmonic oscillator potential hint on improving scheme-independence in the next-to-leading order of the gradient expansion, although the truncated perturbation expansion in the bare quartic coupling provides strongly scheme-dependent results for the infrared limits of the running couplings.

Nagy, S., E-mail: nagys@dtp.atomki.hu [Department of Theoretical Physics, University of Debrecen, P.O. Box 5, H-4010 Debrecen (Hungary); Sailer, K. [Department of Theoretical Physics, University of Debrecen, P.O. Box 5, H-4010 Debrecen (Hungary)

2011-08-15

170

Preparation of carboxylate-functionalized cellulose via solvent-free mechanochemistry and its characterization as a biosorbent for removal of Pb2+ from aqueous solution.  

PubMed

Carboxylate-functionalized cellulose can be used as a low cost but effective biosorbent for heavy metals remediation. In this study, it was simply fabricated from wood cellulose and succinic anhydride via solvent-free mechanochemistry in the absence of catalyst at ambient temperature through pan-milling. Fourier transform infrared spectra (FT-IR) confirmed the realization of mechanochemical esterification of cellulose. Reaction kinetics study showed that this solid-state mechanochemical reaction was governed by "slow followed by fast" kinetics model. The reaction sites were mainly at the new surface of cellulose powder where hydrogen bondings in cellulose were broken up and hydroxyl groups were activated due to the fairly strong forces imposed by the pan-mill. X-ray photoelectron spectroscopy (XPS) indicated that the mechanochemical succinylation of cellulose occurred even in a short milling time. The exponential increment of surface area of cellulose during pan-milling was correlated to the increasing substitution degree. Preliminary adsorption studies showed that the modified cellulose possessed excellent adsorption capacity towards Pb(2+), with lead ion uptake value of 422 mg/g and 84.4% metal removal from a 500 mg/g Pb(2+) solution, significantly higher than those values for unmodified cellulose. PMID:20605320

Zhang, Wei; Li, Cuiying; Liang, Mei; Geng, Yamin; Lu, Canhui

2010-09-15

171

Functional Role of the Carboxyl Terminal Domain of Human Connexin 50 in Gap Junctional Channels  

PubMed Central

Gap junction channels formed by connexin 50 (Cx50) are critical for maintenance of lens transparency. Because the C-terminus of Cx50 can be cleaved post-translationally, we hypothesized that channels formed by the truncated Cx50 exhibit altered properties or regulation. We used the dual whole-cell patch-clamp technique to investigate the macroscopic and single-channel properties of gap junctional channels formed by wild-type human Cx50 and a truncation mutant (Cx50A294stop) after transfection of N2A cells. Our results show that wild-type Cx50 formed functional gap junctional channels. The macroscopic Gjss-Vj relationship was well described by a Boltzmann equation with A of 0.10, V0 of 43.8 mV and Gjmin of 0.23. The single-channel conductance was 212 ± 5 pS. Multiple long-lasting substates were observed with conductances ranging between 31 and 80 pS. Wild-type Cx50 gap junctional channels were reversibly blocked when pHi was reduced to 6.3. Truncating the C-terminus at amino acid 294 caused a loss of pHi sensitivity, but there were no significant changes in single-channel current amplitude or Gjss-Vj relationship. These results suggest that the C-terminus of human Cx50 is involved in pHi sensitivity, but has little influence over single-channel conductance, voltage dependence, or gating kinetics.

Xu, X.; Berthoud, V.M.; Beyer, E.C.; Ebihara, L.

2009-01-01

172

Visible light photorelease of carboxylate anions by mediated photoinduced electron transfer to pyridinium-based protecting groups  

Microsoft Academic Search

The use of sensitized photoinduced electron transfer (PET) to trigger release of redox-active photoremovable protecting groups (PRPGs) allows a broad range of chromophores to be selected that absorb in difference wavelength ranges. Mediated electron transfer (MET) is particularly advantageous as sub-stoichiometric amounts of the often costly sensitizer (relative to the amount of protected substrate) can be combined with an excess

John Brian Borak

2009-01-01

173

Nonlinear optical properties of mono-functional 1,2-dihydro-1,2-methanofullerene[60]-61-carboxylic acid\\/polymer composites  

Microsoft Academic Search

By using nanosecond laser pulses at 532-nm wavelength, we have studied the nonlinear optical properties of composites which consist of mono-functional 1,2-dihydro-1,2-methanofullerene[60]-61-carboxylic acid (FCA) and poly(styrene-co-4-vinylpyridine). The optical limiting performance of FCA itself is poorer than that of its parent C60, while FCA incorporated with polystyrene shows better optical limiting responses, with the limiting threshold reduced by about 35%. In

H. Izaac Elim

2003-01-01

174

rac-Ammonium cis-2-carb-oxy-cyclo-hexane-1-carboxyl-ate  

PubMed Central

In the structure of the title compound, NH4 +·C8H11O4 ?, the carboxyl and carboxyl­ate groups of the cation adopt C—C—C—O torsion angles of 174.9?(2) and ?145.4?(2)°, respectively, with the alicyclic ring. The ammonium H atoms of the cations give a total of five hydrogen-bonding associations with carboxyl­ate O-atom acceptors of the anion which, together with a carboxyl O—H?Ocarboxyl­ate inter­action give sheet structures which lie in the (101) planes.

Smith, Graham; Wermuth, Urs D.

2011-01-01

175

Hierarchical Grouping to Optimize an Objective Function  

Microsoft Academic Search

A procedure for forming hierarchical groups of mutually exclusive subsets, each of which has members that are maximally similar with respect to specified characteristics, is suggested for use in large-scale (n > 100) studies when a precise optimal solution for a specified number of groups is not practical. Given n sets, this procedure permits their reduction to n ? 1

Joe H. Ward Jr

1963-01-01

176

Amide functional group contribution to the stability of gadolinium(III) complexes: DTPA derivatives  

SciTech Connect

The Gd{sup 3+} complexes of diethylenetriaminepentaacetic acid (DTPA) and several closely related ligands are in use, or being developed, as contrast agents for magnetic resonance imaging (MRI). The bis(amide) derivatives of DTPA are, like the parent DTPA ligand, octadenate complexing agents of gadolinium, replacing two carboxylate coordinating groups with coordinating amide oxygens. Remarkably, this maintains a significant portion of the stability of the gadolinium complex and an increase in the relative selectivity for Gd{sup 3+} vs Ca{sup 2+}. The magnitude of the contribution of the amide functional groups to this stability is investigated. A diethylenetriaminetricarboxylic acid bis(amide) derivative in which the two terminal amide groups are replaced by methyl groups (bis(methyl)-diethylenetriaminetriacetic acid, DTTA-BM) is found to have a metal ion affinity at pH 7.4 that is 6.75 log units smaller than the effective stability of the bis-amide DTPA derivatives, corresponding to an average contribution of 3.38 log units to the stability of the complex from each amide functional group. The effective stability of the DTTA-BM Ca{sup 2+} complex relative to the bis(amide) ligands does not change as much. Hence, the amide functional groups contribute significant stability for gadolinium complexation but little or no enhancement of calcium complexation, explaining the relative selectivity of bis(amide) ligands as gadolinium(III) complexing agents.

Paul-Roth, C.; Raymond, K.N. [Univ. of California, Berkeley, CA (United States)

1995-03-15

177

High-throughput aided synthesis of the porous metal-organic framework-type aluminum pyromellitate, MIL-121, with extra carboxylic acid functionalization.  

PubMed

A new porous metal-organic framework (MOF)-type aluminum pyromellitate (MIL-121 or Al(OH)[H(2)btec]·(guest), (guest = H(2)O, H(4)btec = pyromellitic acid) has been isolated by using a high-throughput synthesis method under hydrothermal conditions. Its structure was determined from powder X-ray diffraction analysis using synchrotron radiation (Soleil, France) and exhibits a network closely related to that of the MIL-53 series. It is a three-dimensional (3D) framework containing one-dimensional (1D) channels delimited by infinite trans-connected aluminum-centered octahedra AlO(4)(OH)(2) linked through the pyromellitate ligand. Here the organic ligand acts as tetradendate linker via two of the carboxylate groups. The two others remain non-bonded in their protonated form, and this constitutes a rare case of the occurrence of both bonding and non-bonding organic functionalities of the MOF family. The non-coordinated -COOH groups points toward the channels to get them an open form configuration. Within the tunnels are located unreacted pyromellitic acid and water species, which are evacuated upon heating, and a porous MIL-121 phase is obtained with a Brunauer-Emmett-Teller (BET) surface area of 162 m(2) g(-1). MIL-121 has been characterized by IR, thermogravimetry (TG) analyses, and solid state NMR spectroscopy employing a couple of two-dimensional (2D) techniques such as (1)H-(1)H SQ-DQ BABA, (1)H-(1)H SQ-SQ RFDR, (27)Al{(1)H} CPHETCOR and (27)Al MQMAS. PMID:20923169

Volkringer, Christophe; Loiseau, Thierry; Guillou, Nathalie; Férey, Gérard; Haouas, Mohamed; Taulelle, Francis; Elkaim, Erik; Stock, Norbert

2010-11-01

178

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

179

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

180

Functional group composition of organic aerosol from combustion emissions and secondary processes at two contrasted urban environments  

NASA Astrophysics Data System (ADS)

The quantification of major functional groups in atmospheric organic aerosol (OA) provides a constraint on the types of compounds emitted and formed in atmospheric conditions. This paper presents functional group composition of organic aerosol from two contrasted urban environments: Marseille during summer and Grenoble during winter. Functional groups were determined using a tandem mass spectrometry approach, enabling the quantification of carboxylic (RCOOH), carbonyl (RCOR'), and nitro (RNO2) functional groups. Using a multiple regression analysis, absolute concentrations of functional groups were combined with those of organic carbon derived from different sources in order to infer the functional group contents of different organic aerosol fractions. These fractions include fossil fuel combustion emissions, biomass burning emissions and secondary organic aerosol (SOA). Results clearly highlight the differences between functional group fingerprints of primary and secondary OA fractions. OA emitted from primary sources is found to be moderately functionalized, as about 20 carbons per 1000 bear one of the functional groups determined here, whereas SOA is much more functionalized, as in average 94 carbons per 1000 bear a functional group under study. Aging processes appear to increase both RCOOH and RCOR' functional group contents by nearly one order of magnitude. Conversely, RNO2 content is found to decrease with photochemical processes. Finally, our results also suggest that other functional groups significantly contribute to biomass smoke and SOA. In particular, for SOA, the overall oxygen content, assessed using aerosol mass spectrometer measurements by an O:C ratio of 0.63, is significantly higher than the apparent O:C* ratio of 0.17 estimated based on functional groups measured here. A thorough examination of our data suggests that this remaining unexplained oxygen content can be most probably assigned to alcohol (ROH), organic peroxides (ROOH), organonitrates (RONO2) and/or organosulfates (ROSO3H).

El Haddad, Imad; Marchand, Nicolas; D'Anna, Barbara; Jaffrezo, Jean Luc; Wortham, Henri

2013-08-01

181

Effects of alkyl chain length and solvents on thermodynamic dissociation constants of the ionic liquids with one carboxyl group in the alkyl chain of imidazolium cations.  

PubMed

Thermodynamic dissociation constants of the Brønsted acidic ionic liquids (ILs) are important for their catalytic and separation applications. In this work, a series of imidazolium bromides with one carboxylic acid substitute group in their alkyl chain ([{(CH2)nCOOH}mim]Br, n = 1,3,5,7) have been synthesized, and their dissociation constants (pKa) at different ionic strengths have been determined in aqueous and aqueous organic solvents at 0.1 mole fraction (x) of ethanol, glycol, iso-propanol, and dimethyl sulfoxide by potentiometric titrations at 298.2 K. The standard thermodynamic dissociation constants (pKa(T)) of the ILs in these solvents were calculated from the extended Debye-Hückel equation. It was found that the pKa values increased with the increase of ionic strength of the media and of the addition of organic solvent in water. The pKa(T) values also increased with the increase of the alkyl chain length of cations of the ILs. In addition, the effect of solvent nature on pKa(T) values is interpreted from solvation of the dissociation components and their Gibbs energy of transfer from water to aqueous organic solutions. PMID:24720707

Chen, Yuehua; Wang, Huiyong; Wang, Jianji

2014-05-01

182

Contribution of cytochrome P450 and UDT-glucuronosyltransferase to the metabolism of drugs containing carboxylic acid groups: risk assessment of acylglucuronides using human hepatocytes.  

PubMed

Abstract 1.?In order to evaluate the inhibition activity of 1-aminobenzotriazole (ABT) and (-)-borneol (borneol) against cytochrome P450 (CYP) and UDP-glucuronosyltransferase (UGT), the substrates of these metabolic enzymes were incubated with ABT and borneol in human hepatocytes. We found that 3?mM ABT and 300??M borneol were the most suitable experimental levels to specifically inhibit CYP and UGT. 2.?Montelukast, mefenamic acid, flufenamic acid, diclofenac, tienilic acid, gemfibrozil, ibufenac and repaglinide were markedly metabolized in human hepatocytes, and the metabolism of gemfibrozil, mefenamic acid and flufenamic acid was inhibited by borneol. With regard to repaglinide, montelukast, diclofenac and tienilic acid, metabolism was inhibited by ABT. Ibufenac was partly inhibited by both inhibitors. Zomepirac, tolmetin, ibuprofen, indomethacin and levofloxacin were moderately metabolized by human hepatocytes, and the metabolism of zomepirac, ibuprofen and indomethacin was equally inhibited by both ABT and borneol. The metabolism of tolmetin was strongly inhibited by ABT, and was also inhibited weakly by borneol. Residual drugs, telmisartan, valsartan, furosemide, naproxen and probenecid were scarcely metabolized. 3.?Although we attempted to predict the toxicological risks of drugs containing carboxylic groups from the combination chemical stability and CLint via UGT, the results indicated that this combination was not sufficient and that clinical daily dose is important. PMID:24575896

Jinno, Norimasa; Tagashira, Mizuka; Tsurui, Kazuyuki; Yamada, Shizuo

2014-08-01

183

Carboxylic Acid (Bio)Isosteres in Drug Design  

PubMed Central

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.

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

2013-01-01

184

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

2013-07-01

185

Photochemical and antimicrobial properties of silver nanoparticle-encapsulated chitosan functionalized with photoactive groups.  

PubMed

Chitosan was functionalized with 4-((E)-2-(3-hydroxynaphthalen-2-yl)diazen-1-yl)benzoic acid by the coupling of the hydroxyl functional groups of chitosan with carboxylic acid group of the dye by DCC coupling method. The silver nanoparticles were prepared by sol-gel method of nanoparticle synthesis. Silver nanoparticle-encapsulated functionalized chitosan was prepared by the phase transfer method. The products were characterized by FTIR, UV-Vis, fluorescence and NMR spectroscopic methods and by SEM and TEM analysis. The photochemical properties of silver nanoparticle-encapsulated chitosan functionalized with 4-((E)-2-(3-hydroxynaphthalen-2-yl)diazen-1-yl)benzoic acid was studied in detail. The light-fastening properties of the chromophoric system was enhanced when attached to chitosan, and it can be further improved by the encapsulation of silver nanoparticles. The antibacterial analysis of silver nanoparticle-encapsulated functionalized chitosan was carried out against Staphylococcus aureus and Escherichia coli and against fungal species such as Aspergillus flavus and Aspergillus terreus. This study showed that silver nanoparticles-encapsulated functionalized chitosan can be used for antibacterial and antifungal applications. PMID:23910360

Mathew, Thomas V; Kuriakose, Sunny

2013-10-01

186

Sampling of Functions and Sections for Compact Groups  

Microsoft Academic Search

In this paper we investigate quadrature rules for functions on compact Lie groups and sections of homogeneous vector bundles associated with these groups. First a general notion of band-limitedness is introduced which generalizes the usual notion on the torus or translation groups. We develop a sampling theorem that allows exact computation of the Fourier expansion of a band-limited function or

DAVID KEITH MASLEN

1999-01-01

187

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

188

Preparation of 1-Aminocyclopropane Carboxylic Acids.  

National Technical Information Service (NTIS)

Amino acid is a compound having an amino group as well as a carboxylic acid group in a molecule simultaneously. The report deals with the synthesis of amino acids having a cyclopropane ring in them, i.e., the synthesis of 1-amino+cyclopropane carboxylic a...

M. I. Mughal

1981-01-01

189

A Mononuclear Carboxylate-Rich Oxoiron(IV) Complex: a Structural and Functional Mimic of TauD Intermediate 'J'  

PubMed Central

The pentadentate ligand nBu-P2DA (2(b), nBu-P2DA = N-(1?,1?-bis(2-pyridyl)pentyl)iminodiacetate) was designed to bind an iron center in a carboxylate-rich environment similar to that found in the active sites of TauD and other ?-ketoglutarate-dependent mononuclear non-heme iron enzymes. The iron(II) complex nBu4N[FeII(Cl)(nBu-P2DA)] (3(b)-Cl) was synthesized and crystallographically characterized to have a 2-pyridine-2-carboxylate donor set in the plane perpendicular to the Fe-Cl bond. Reaction of 3(b)-Cl with N-heterocyclic amines such as pyridine or imidazole yielded the N-heterocyclic amine adducts [FeII(N)(nBu-P2DA)]. These adducts in turn reacted with oxo-transfer reagents at ?95 °C to afford a short-lived oxoiron(IV) complex [FeIV(O)(nBu-P2DA)] (5(b)) in yields as high as 90% depending on the heterocycle used. Complex 5(b) exhibits near-IR absorption features (?max = 770 nm) and Mossbauer parameters (? = 0.04 mm/s; ?EQ = 1.13 mm/s; D = 27±2 cm?1) characteristic of an S = 1 oxoiron(IV) species. Direct evidence for an Fe=O bond of 1.66 Å was found from EXAFS analysis. DFT calculations on 5(b) in its S =1 spin state afforded a geometry-optimized structure consistent with the EXAFS data. They further demonstrated that the replacement of two pyridine donors in [FeIV(O)(N4Py)]2+ (N4Py = N,N-(bis(2-pyridyl)methyl)N-bis(2-pyridylmethyl)amine) with carboxylate donors in 5(b) decreased the energy gap between the ground S = 1 and the excited S = 2 states, reflecting the weaker equatorial ligand field of 5(b) and accounting for its larger D value. Complex 5(b) reacted readily with dihydrotoluene, methyldiphenylphosphine and ferrocene at ?60 °C, and in all cases was approximately a 5-fold more reactive oxidant than [FeIV(O)(N4Py)]2+. The reactivity differences between these two complexes may arise from a combination of electronic and steric factors. Carboxylate-rich 5(b) represents the closest structural mimic reported thus far of the oxoiron(IV) intermediate (‘J’) found in TauD and provides us with vital insights into the role carboxylate ligands play in modulating the spectroscopic and reactivity properties of the non-heme oxoiron(IV) moiety.

McDonald, Aidan R.; Guo, Yisong; Vu, Van V.; Bominaar, Emile L.; Munck, Eckard; Que, Lawrence

2012-01-01

190

Oxidation of carboxylic acids by horseradish peroxidase results in prosthetic heme modification and inactivation.  

PubMed

Hemoproteins are powerful oxidative catalysts. However, despite the diversity of functions known to be susceptible to oxidation by these catalysts, it is not known whether they can oxidize carboxylic acids to carboxylic radicals. We report here that incubation of horseradish peroxidase (HRP) at acidic pH with H(2)O(2) in acetate buffer results in rapid modification of the heme group and loss of catalytic activity. Mass spectrometry and NMR indicate that an acetoxy group is covalently bound to the delta-meso-carbon in the modified heme. A heme with a hydroxyl group on the 8-methyl is also formed as a minor product. These reactions do not occur if protein-free heme and H(2)O(2) are co-incubated in acetate buffer, if the HRP reaction is carried out at pH 7, in the absence of H(2)O(2), or if citrate rather than acetate buffer is used. A similar heme modification is observed in incubations with n-caproic and phenylacetic acids. A mechanism involving oxidation of the carboxyl group to a carboxylic radical followed by addition to the delta-meso-position is proposed. This demonstration of the oxidation of a carboxylic acid solidifies the proposal that a carboxylic radical mediates the normal covalent attachment of the heme to the protein in the mammalian peroxidases and CYP4 family of P450 enzymes. The hemoprotein-mediated oxidation of carboxylic acids, ubiquitous natural constituents, may play other roles in biology. PMID:15469283

Huang, Liusheng; Colas, Christophe; Ortiz de Montellano, Paul R

2004-10-13

191

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

192

Nonlinear optical properties of mono-functional 1,2-dihydro-1,2-methanofullerene[60]-61-carboxylic acid/polymer composites  

NASA Astrophysics Data System (ADS)

By using nanosecond laser pulses at 532-nm wavelength, we have studied the nonlinear optical properties of composites which consist of mono-functional 1,2-dihydro-1,2-methanofullerene[60]-61-carboxylic acid (FCA) and poly(styrene-co-4-vinylpyridine). The optical limiting performance of FCA itself is poorer than that of its parent C 60, while FCA incorporated with polystyrene shows better optical limiting responses, with the limiting threshold reduced by about 35%. In addition, the FCA gives slightly stronger photoluminescence emission than that of both C 60 and FCA/polymer composites. The possible sources for the improvement in the optical limiting are discussed.

Izaac Elim, Hendry; Ouyang, Jianying; He, Jun; Hong Goh, Suat; Hai Tang, Sing; Ji, Wei

2003-02-01

193

Mappings of homogeneous groups and imbeddings of functional spaces  

Microsoft Academic Search

Varying the functional space ~, we obtain each time a new problem (see [2-7], where one has considered several characteristic cases of isotropic spaces of differentiab!e functions). In this paper we investigate a similar problem for functional spaces, defined on an arbitrary homogeneous group. Model examples are the fundamental anisotropic spaces of differentiable functions. The corresponding mappings have qualitative new

S. K. Vodop'yanov

1989-01-01

194

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

195

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

196

Novel Condensed Ring Carboxylic Hydroxamic Acid Studied in the Flotation Behavior of Diaspore and Aluminosilicates  

Microsoft Academic Search

Flotation reagents are the critical technique in the flotation separation process for desilication. Aimed at the highly selective reagent for direct flotation of diasporic bauxite, a novel compound, dibenzo-1-(7-carboxyl-4-hydroxyl bicycle [2.2.2] octan-7,8-diyl) carboxamic acid (DBCA) with two functional groups carboxyl and hydroxamate in the same molecule, was synthesized through Diels-Alder reaction followed by oximation reaction. Subsequently, the floatability of diaspore,

Yu-Ren Jiang; Li-Yi Zhou; Xiao-Hong Zhou; Bin-Nan Zhao

2010-01-01

197

Carboxylated Derivatives of Oleyl Alcohol and Method for Their Production.  

National Technical Information Service (NTIS)

The process is for introducing a carboxyl group into oleyl alcohol. Direct carboxylation of long chain olefinic compounds with carbon monoxide is achieved at atmospheric pressure by employing a narrow range of operating conditions in which the concentrati...

E. T. Roe D. Swern

1965-01-01

198

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

199

Derivatization of hydroxyl functional groups for liquid chromatography and capillary electroseparation.  

PubMed

The derivatization reactions commonly used to enhance the analytical signal in the HPLC and CE determination of compounds with hydroxyl functional groups are revised. Focus is placed on the determination of compounds having aliphatic alcohols and phenols while lacking other reactive functional groups. The derivatization with acyl chlorides, organic anhydrides, isocyanates and a variety of other approaches, including oxidation of primary and secondary alcohols, sulfonation, esterification with carboxylic acids, and the use of azides, sulfonyl chlorides and other reagents having miscellaneous leaving groups, is covered. Reactions mainly addressed to introduce a chromophore or a fluorophore in the analyte molecule, or to introduce a charge to enhance sensitivity in MS detection, or to enable CE separation are included. Applications related to the industrial quality control of raw materials and manufactured products, and to the evaluation of their environmental impact are emphasized. The problem of the different response factors of the derivatives when complex mixtures of oligomers are derivatized, as occurs with non-ionic surfactants (mainly fatty alcohol ethoxylates) and soluble synthetic polymers, is discussed. Other applications related to the biochemical, biomedical, pharmaceutical, nutritional and toxicological fields are also reviewed. The reactions, the criteria to be applied to select the reagent, and the characteristics of the derivatives in relation to separation and detection, are discussed. PMID:23643100

Escrig-Doménech, A; Simó-Alfonso, E F; Herrero-Martínez, J M; Ramis-Ramos, G

2013-06-28

200

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

201

Staffing and Training: Neglected Supervisory Functions Related to Group Performance  

ERIC Educational Resources Information Center

This research reports the relationship between supervisory performance of eight leadership functions and group performance in 43 library work units. These eight functions can be used as a guide to future research designed to identify additional leadership functions. (Author/RK)

Bare, Alan C.

1978-01-01

202

Mass spectrometry-based carboxyl footprinting of proteins: method evaluation.  

PubMed

Protein structure determines function in biology, and a variety of approaches have been employed to obtain structural information about proteins. Mass spectrometry-based protein footprinting is one fast-growing approach. One labeling-based footprinting approach is the use of a water-soluble carbodiimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and glycine ethyl ester (GEE) to modify solvent-accessible carboxyl groups on glutamate (E) and aspartate (D). This paper describes method development of carboxyl-group modification in protein footprinting. The modification protocol was evaluated by using the protein calmodulin as a model. Because carboxyl-group modification is a slow reaction relative to protein folding and unfolding, there is an issue that modifications at certain sites may induce protein unfolding and lead to additional modification at sites that are not solvent-accessible in the wild-type protein. We investigated this possibility by using hydrogen deuterium amide exchange (H/DX). The study demonstrated that application of carboxyl group modification in probing conformational changes in calmodulin induced by Ca(2+) binding provides useful information that is not compromised by modification-induced protein unfolding. PMID:22408386

Zhang, Hao; Wen, Jianzhong; Huang, Richard Y-C; Blankenship, Robert E; Gross, Michael L

2012-02-15

203

Mass spectrometry-based carboxyl footprinting of proteins: method evaluation  

PubMed Central

Protein structure determines function in biology, and a variety of approaches have been employed to obtain structural information about proteins. Mass spectrometry-based protein footprinting is one fast-growing approach. One labeling-based footprinting approach is the use of a water-soluble carbodiimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and glycine ethyl ester (GEE) to modify solvent-accessible carboxyl groups on glutamate (E) and aspartate (D). This paper describes method development of carboxyl-group modification in protein footprinting. The modification protocol was evaluated by using the protein calmodulin as a model. Because carboxyl-group modification is a slow reaction relative to protein folding and unfolding, there is an issue that modifications at certain sites may induce protein unfolding and lead to additional modification at sites that are not solvent-accessible in the wild-type protein. We investigated this possibility by using hydrogen deuterium amide exchange (H/DX). The study demonstrated that application of carboxyl group modification in probing conformational changes in calmodulin induced by Ca2+ binding provides useful information that is not compromised by modification-induced protein unfolding.

Zhang, Hao; Wen, Jianzhong; Huang, Richard Y-C; Blankenship, Robert E.; Gross, Michael L.

2011-01-01

204

Antilipidemic activity of 4-oxo-functionalized ethyl 6-chlorochroman-2-carboxylate analogs and a related tricyclic lactone in three rat models  

Microsoft Academic Search

The synthesis of ethylcis-6-chloro-4-hydroxychroman-2-carboxylate (IV) and 6-chloro-4-hydroxychroman-2-carboxylic acid lactone (V) are reported. The\\u000a antilipidemic properties of these compounds in 3 rat models were compared to the activity obtained for the previously synthesized\\u000a related analogs ethyl 6-chlorochroman-2-carboxylate (II), ethyl 6-chlorochromanone-2-carboxylate (III) and clofibrate (I).\\u000a The biologically most interesting analog, ethyl 6-chlorochroman-2-carboxylate (II) like clofibrate (I), was an effective antitriglyceridemic\\u000a and anticholesterolemic

R. C. Cavestri; J. A. Minatelli; J. R. Baldwin; W. Loh; D. R. Feller; H. A. I. Newman; C. L. Sober; D. T. Witiak

1981-01-01

205

Interaction of phenylated carboxylic acids with a conjugated imine in a study of a model of rhodopsin  

NASA Astrophysics Data System (ADS)

Seven carboxylic acids containing a phenyl or a phenolic group and three acrylic acid derivatives were mixed in equimolar concentrations with a dienylidene Schiff base in chloroform. UV and 1H NMR (400 MHz) spectra indicated that the phenyl and the phenolic groups could not red-shift the Schiff base absorption band but could interact with the imine by their carboxylic function through a hydrogen bridge. Of all the acids studied, only phenylpropiolic acid could protonate the Schiff base.

Le Thanh, Hoa; Vocelle, Daniel

1984-11-01

206

Adsorption of Fe(II) and U(VI) to carboxyl-functionalized microspheres : the influence of speciation on uranyl reduction studied by titration and XAFS.  

SciTech Connect

The chemical reduction of U(VI) by Fe(II) is a potentially important pathway for immobilization of uranium in subsurface environments. Although the presence of surfaces has been shown to catalyze the reaction between Fe(II) and U(VI) aqueous species, the mechanism(s) responsible for the enhanced reactivity remain ambiguous. To gain further insight into the U--Fe redox process at a complexing, non-conducting surface that is relevant to common organic phases in the environment, we studied suspensions containing combinations of 0.1 mM U(VI), 1.0 mM Fe(II), and 4.2 g/L carboxyl-functionalized polystyrene microspheres. Acid-base titrations were used to monitor protolytic reactions, and Fe K-edge and U L-edge X-ray absorption fine structure spectroscopy was used to determine the valence and atomic environment of the adsorbed Fe and U species. In the Fe + surface carboxyl system, a transition from monomeric to oligomeric Fe(II) surface species was observed between pH 7.5 and pH 8.4. In the U + surface carboxyl system, the U(VI) cation was adsorbed as a mononuclear uranyl-carboxyl complex at both pH 7.5 and 8.4. In the ternary U + Fe + surface carboxyl system, U(VI) was not reduced by the solvated or adsorbed Fe(II) at pH 7.5 over a 4-month period, whereas complete and rapid reduction to U(IV) nanoparticles occurred at pH 8.4. The U(IV) product reoxidized rapidly upon exposure to air, but it was stable over a 4-month period under anoxic conditions. Fe atoms were found in the local environment of the reduced U(IV) atoms at a distance of 3.56 Angstroms. The U(IV)-Fe coordination is consistent with an inner-sphere electron transfer mechanism between the redox centers and involvement of Fe(II) atoms in both steps of the reduction from U(VI) to U(IV). The inability of Fe(II) to reduce U(VI) in solution and at pH 7.5 in the U + Fe + carboxyl system is explained by the formation of a transient, 'dead-end' U(V)-Fe(III) complex that blocks the U(V) disproportionation pathway after the first electron transfer. The increased reactivity at pH 8.4 relative to pH 7.5 is explained by the reaction of U(VI) with an Fe(II) oligomer, whereby the bonds between Fe atoms facilitate the transfer of a second electron to the hypothetical U(V)--Fe(III) intermediate. We discuss how this mechanism may explain the commonly observed higher efficiency of uranyl reduction by adsorbed or structural Fe(II) relative to aqueous Fe(II).

Boyanov, M. I.; O'Loughlin, E. J.; Roden, E. E.; Fein, J. B.; Kemner, K. M.; Biosciences Division; Univ. of Notre Dame; Univ. of Wisconsin

2007-04-15

207

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

2013-09-17

208

Discovering herbal functional groups of traditional Chinese medicine.  

PubMed

For the traditional Chinese medicine (TCM), a prescription for a patient often contains several herbs. Some herbs are often used together in prescriptions, and these herbs can be considered as a functional group. In this paper, we propose an approach for discovering herbal functional groups from a large set of prescriptions recorded in TCM books. These functional groups are allowed to overlap with each other. Our approach is validated with a simulation study and applied to a data set containing thousands of TCM prescriptions. PMID:21413055

He, Ping; Deng, Ke; Liu, Zhihai; Liu, Delin; Liu, Jun S; Geng, Zhi

2012-03-30

209

Electrical transport and field-effect transistors using inkjet-printed SWCNT films having different functional side groups.  

PubMed

The electrical properties of random networks of single-wall carbon nanotubes (SWNTs) obtained by inkjet printing are studied. Water-based stable inks of functionalized SWNTs (carboxylic acid, amide, poly(ethylene glycol), and polyaminobenzene sulfonic acid) were prepared and applied to inkjet deposit microscopic patterns of nanotube films on lithographically defined silicon chips with a back-side gate arrangement. Source-drain transfer characteristics and gate-effect measurements confirm the important role of the chemical functional groups in the electrical behavior of carbon nanotube networks. Considerable nonlinear transport in conjunction with a high channel current on/off ratio of approximately 70 was observed with poly(ethylene glycol)-functionalized nanotubes. The positive temperature coefficient of channel resistance shows the nonmetallic behavior of the inkjet-printed films. Other inkjet-printed field-effect transistors using carboxyl-functionalized nanotubes as source, drain, and gate electrodes, poly(ethylene glycol)-functionalized nanotubes as the channel, and poly(ethylene glycol) as the gate dielectric were also tested and characterized. PMID:20481513

Gracia-Espino, Eduardo; Sala, Giovanni; Pino, Flavio; Halonen, Niina; Luomahaara, Juho; Mäklin, Jani; Tóth, Géza; Kordás, Krisztián; Jantunen, Heli; Terrones, Mauricio; Helistö, Panu; Seppä, Heikki; Ajayan, Pulickel M; Vajtai, Robert

2010-06-22

210

1-Azaniumylcyclobutane-1-carboxylate monohydrate  

NASA Technical Reports Server (NTRS)

In the title compound, C5H9NO2H2O, the amino acid is in the usual zwitterionic form involving the carboxylate group. The cyclobutane backbone of the amino acid is disordered over two conformations, with occupancies of 0.882 (7) and0.118 (7). In the crystal, NH O and OH O hydrogen bonds link the zwitterions [with the water molecule involved as both acceptor (with the NH3+) and donor (through a single carboxylate O from two different aminocyclobutane carboxylatemoities)], resulting in a two-dimensional layered structure lying parallel to (100).

Butcher, Ray J.; Brewer, Greg; Burton, Aaron S.; Dworkin, Jason

2014-01-01

211

Effect of functional groups on the crystallization of ferric oxides/oxyhydroxides in suspension environment  

NASA Astrophysics Data System (ADS)

This paper investigated the effects of five kinds of Au surfaces terminated with and without functional groups on the crystallization of ferric oxides/oxyhydroxides in the suspension condition. Self-assembled monolayers (SAMs) were used to create hydroxyl (-OH), carboxyl (-COOH), amine (-NH2) and methyl (-CH3) functionalized surfaces, which proved to be of the same surface density. The immersion time of substrates in the Fe(OH)3 suspension was divided into two time portions. During the first period of 2 h, few ferric oxide/oxyhydroxide was deposited except that ?-Fe2O3 was detected on -NH2 surface. Crystallization for 10 h evidenced more kinds of iron compounds on the functional surfaces. Goethite and maghemite were noticed on four functional surfaces, and maghemite also grew on Au surface. Deposition of ?-Fe2O3 was found on -OH surface, while the growth of orthorhombic and hexagon FeOOH were indicated on -NH2 surface. Considering the wide existence of iron compounds in nature, our investigation is a precedent work to the study of iron biomineralization in the suspension area.

Zhou, Qiong; Albert, Olga; Deng, Hua; Yu, Xiao-Long; Cao, Yang; Li, Jian-Bao; Huang, Xin

2012-12-01

212

The luminosity function of galaxies in compact groups  

NASA Technical Reports Server (NTRS)

We use counts of faint galaxies in the regions of compact groups to extend the study of the luminosity function of galaxies in compact groups to absolute magnitudes as faint as M(sub B) = -14.5 + 5 log h. We find a slope of the faint end of the luminosity function of approximately alpha = -0.8, with a formal uncertainty of 0.15. This slope is not significantly different from that found for galaxies in other environments. Our results do not support previous suggestions of a dramatic underabundance of intrinsically faint galaxies in compact groups, which were based on extrapolations from fits at brighter magnitudes. The normal faint-end slope of the luminosity function in compact groups is in agreement with previous evidence that most galaxies in compact groups have not been dramatically affected by recent merging.

Ribeiro, A. L. B.; De Carvalho, R. R.; Zepf, S. E.

1994-01-01

213

Analysis of Functional Groups by Solubility and Infrared Analysis.  

ERIC Educational Resources Information Center

An experiment which introduces students to infrared spectroscopy and the solubility behavior of various organic compounds is described. The experiment also serves to integrate some of the basic chemical reactions of functional groups with their spectral properties. (JN)

Turek, William N.

1984-01-01

214

Functional Group and Substructure Searching as a Tool in Metabolomics  

Microsoft Academic Search

BackgroundA 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.MethodologyWe have developed a database

Masaaki Kotera; Andrew G. McDonald; Sinéad Boyce; Keith F. Tipton; Ji Zhu

2008-01-01

215

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

2013-01-23

216

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

2011-06-15

217

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

2012-04-25

218

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

219

The human immunodeficiency virus Tat proteins specifically associate with TAK in vivo and require the carboxyl-terminal domain of RNA polymerase II for function.  

PubMed

Human immunodeficiency virus types 1 and 2 encode closely related proteins, Tat-1 and Tat-2, that stimulate viral transcription. Previously, we showed that the activation domains of these proteins specifically interact in vitro with a cellular protein kinase named TAK. In vitro, TAK phosphorylates the Tat-2 but not the Tat-1 protein, a 42-kDa polypeptide of unknown identity, and the carboxyl-terminal domain (CTD) of RNA polymerase II (RNAP II). We now show that the 42-kDa substrate of TAK cochromatographs with TAK activity, suggesting that this 42-kDa polypeptide is a subunit of TAK. We also show that the Tat proteins specifically associate with TAK in vivo, since wild-type Tat-1 and Tat-2 proteins expressed in mammalian cells, but not mutant Tat proteins containing a nonfunctional activation domain, can be coimmunoprecipitated with TAK. We also mapped the in vivo phosphorylation sites of Tat-2 to the carboxyl terminus of the protein, but analysis of proteins with mutations at these sites suggests that phosphorylation is not essential for Tat-2 transactivation function. We further investigated whether the CTD of RNAP II is required for Tat function in vivo. Using plasmid constructs that express an alpha-amanitin-resistant RNAP II subunit with a truncated or full-length CTD, we found that an intact CTD is required for Tat function. These observations strengthen the proposal that the mechanism of action of Tat involves the recruitment or activation of TAK, resulting in activated transcription through phosphorylation of the CTD. PMID:8676484

Yang, X; Herrmann, C H; Rice, A P

1996-07-01

220

Metallicity retained by covalent functionalization of graphene with phenyl groups.  

PubMed

To resolve the controversy over the functionalization effect on conductivity, we systematically investigate the structural and electronic properties of graphene covalently functionalized with phenyl groups. Using first-principles calculations combined with the model Hamiltonian analysis, we find that the structural stability, electronic and transport properties of the functionalized graphene are strongly dependent on the adsorption site of the phenyl groups. In detail, double-side functionalized graphene is energetically more favorable than single-side functionalized graphene, and more importantly, they exhibit an exotic non-magnetic metallic state and a magnetic semiconducting state, respectively. For covalently double-side functionalized graphene, two bands contributed by ? electrons of graphene cross at the Fermi level with the preserved electron-hole symmetry, and the Fermi velocity of carriers could be flexibly tuned by changing the coverage of the phenyl groups. These results provide an insight into the experimental observation [ACS Nano 2011, 5, 7945], interpreting the origin of the increase in the conductivity of graphene covalently functionalized with phenyl groups. Our work reveals the great potential of these materials in future nanoelectronics or sensors by controlling the attachment of phenyl groups. PMID:23836075

Tang, Peizhe; Chen, Pengcheng; Wu, Jian; Kang, Feiyu; Li, Jia; Rubio, Angel; Duan, Wenhui

2013-08-21

221

Extensions of positive definite functions on free groups  

Microsoft Academic Search

An analogue of Krein's extension theorem is proved for operator-valued positive definite functions on free groups. The proof gives also the parametrization of all extensions by means of a generalized type of Szegö parameters. One singles out a distinguished completion, called central, which is related to quasi-multiplicative positive definite functions. An application is given to factorization of noncommutative polynomials.

M. Bakonyi; D. Timotin

2007-01-01

222

Assessing the roles of essential functional groups in the mechanism of homoserine succinyltransferase.  

PubMed

Homoserine acyltransferases catalyze the commitment step to methionine and other important biological precursors which make this class of enzymes essential for the survival of bacteria, plants and fungi. This class of enzymes is not found in humans, making them an attractive new target for antimicrobial design. Homoserine O-succinyltransferase (HST) is a representative from this class, with little known about the key amino acids involved in substrate specificity and catalysis. HST from Escherichia coli has been cloned, purified and kinetically characterized. Through site-directed mutagenesis and steady-state kinetic studies the residues that comprise a catalytic triad for HST, the catalytic cysteine nucleophile, an active site acid-base histidine, and the base orienting glutamate, have been identified and characterized. Several residues which confer substrate specificity for both homoserine and succinyl-CoA have also been identified and kinetically evaluated. Mutations of an active site glutamate to either aspartate or alanine drastically increase the K(m) for homoserine, assigning this glutamate to a binding role for the alpha-amino group of homoserine. An active site arginine orients the carboxyl moiety of homoserine, while the carboxyl moiety of succinyl-CoA is positioned for catalysis by a lysine residue. Removing functionality at either of these positions alters the enzyme's ability to effectively utilize homoserine or succinyl-CoA, respectively, reflected in an increased K(m) and decreased catalytic efficiency. The data presented here provides new details of the catalytic mechanism of succinyltransferases, resolves a controversy between alternative mechanistic hypotheses, and provides a starting point for the development of selective inhibitors of HST. PMID:17442255

Coe, David M; Viola, Ronald E

2007-05-15

223

Carboxylated magnetic polymer nanolatexes: Preparation, characterization and biomedical applications  

Microsoft Academic Search

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.

Weiming Zheng; Feng Gao; Hongchen Gu

2005-01-01

224

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

225

The synthesis of 13alpha-androsta-5,16-diene derivatives with carboxylic acid, ester and carboxamido functionalities at position-17 via palladium-catalyzed carbonylation.  

PubMed

17-Alkoxycarbonyl- and 17-carboxamido-3beta-hydroxy-13alpha-androsta-5,16-diene derivatives were synthetized in high yields in the palladium-catalyzed carbonylation reactions of the corresponding 3beta-hydroxy-17-iodo-13alpha-androsta-5,16-diene. This substrate with a 17-iodo-16-ene functionality was obtained from the 17-keto derivative via its 17-hydrazone, which was treated with iodine in the presence of a base (1,1,3,3-tetramethylguanidine). 17-Carboxamides were obtained by chemoselective aminocarbonylation through the use of amines, including amino acid esters, as N-nucleophiles. The 17-methoxycarbonyl-16-ene derivative was synthetized by using methanol as O-nucleophile. The parent compound of this series, the 17-carboxylic acid derivative, was formed in the presence of water via hydroxycarbonylation. PMID:19152802

Acs, Péter; Takács, Attila; Szilágyi, Antal; Wölfling, János; Schneider, Gyula; Kollár, László

2009-01-01

226

Molecular cloning of cDNA encoding a drosophila ryanodine receptor and functional studies of the carboxyl-terminal calcium release channel.  

PubMed

Ryanodine is a plant alkaloid that was originally used as an insecticide. To study the function and regulation of the ryanodine receptor (RyR) from insect cells, we have cloned the entire cDNA sequence of RyR from the fruit fly Drosophila melanogaster. The primary sequence of the Drosophila RyR contains 5134 amino acids, which shares approximately 45% identity with RyRs from mammalian cells, with a large cytoplasmic domain at the amino-terminal end and a small transmembrane domain at the carboxyl-terminal end. To characterize the Ca(2+) release channel activity of the cloned Drosophila RyR, we expressed both full-length and a deletion mutant of Drosophila RyR lacking amino acids 277-3650 (Drosophila RyR-C) in Chinese hamster ovary cells. For subcellular localization of the expressed Drosophila RyR and Drosophila RyR-C proteins, green fluorescent protein (GFP)-Drosophila RyR and GFP-Drosophila RyR-C fusion constructs were generated. Confocal microscopic imaging identified GFP-Drosophila RyR and GFP-Drosophila RyR-C on the endoplasmic reticulum membranes of transfected cells. Upon reconstitution into the lipid bilayer membrane, Drosophila RyR-C formed a large conductance cation-selective channel, which was sensitive to modulation by ryanodine. Opening of the Drosophila RyR-C channel required the presence of microM concentration of Ca(2+) in the cytosolic solution, but the channel was insensitive to inhibition by Ca(2+) at concentrations as high as 20 mM. Our data are consistent with our previous observation with the mammalian RyR that the conduction pore of the calcium release channel resides within the carboxyl-terminal end of the protein and further demonstrate that structural and functional features are essentially shared by mammalian and insect RyRs. PMID:10692315

Xu, X; Bhat, M B; Nishi, M; Takeshima, H; Ma, J

2000-03-01

227

Molecular cloning of cDNA encoding a drosophila ryanodine receptor and functional studies of the carboxyl-terminal calcium release channel.  

PubMed Central

Ryanodine is a plant alkaloid that was originally used as an insecticide. To study the function and regulation of the ryanodine receptor (RyR) from insect cells, we have cloned the entire cDNA sequence of RyR from the fruit fly Drosophila melanogaster. The primary sequence of the Drosophila RyR contains 5134 amino acids, which shares approximately 45% identity with RyRs from mammalian cells, with a large cytoplasmic domain at the amino-terminal end and a small transmembrane domain at the carboxyl-terminal end. To characterize the Ca(2+) release channel activity of the cloned Drosophila RyR, we expressed both full-length and a deletion mutant of Drosophila RyR lacking amino acids 277-3650 (Drosophila RyR-C) in Chinese hamster ovary cells. For subcellular localization of the expressed Drosophila RyR and Drosophila RyR-C proteins, green fluorescent protein (GFP)-Drosophila RyR and GFP-Drosophila RyR-C fusion constructs were generated. Confocal microscopic imaging identified GFP-Drosophila RyR and GFP-Drosophila RyR-C on the endoplasmic reticulum membranes of transfected cells. Upon reconstitution into the lipid bilayer membrane, Drosophila RyR-C formed a large conductance cation-selective channel, which was sensitive to modulation by ryanodine. Opening of the Drosophila RyR-C channel required the presence of microM concentration of Ca(2+) in the cytosolic solution, but the channel was insensitive to inhibition by Ca(2+) at concentrations as high as 20 mM. Our data are consistent with our previous observation with the mammalian RyR that the conduction pore of the calcium release channel resides within the carboxyl-terminal end of the protein and further demonstrate that structural and functional features are essentially shared by mammalian and insect RyRs.

Xu, X; Bhat, M B; Nishi, M; Takeshima, H; Ma, J

2000-01-01

228

The synaptic targeting of mGluR1 by its carboxyl-terminal domain is crucial for cerebellar function.  

PubMed

The metabotropic glutamate receptor subtype 1 (mGluR1, Grm1) in cerebellar Purkinje cells (PCs) is essential for motor coordination and motor learning. At the synaptic level, mGluR1 has a critical role in long-term synaptic depression (LTD) at parallel fiber (PF)-PC synapses, and in developmental elimination of climbing fiber (CF)-PC synapses. mGluR1a, a predominant splice variant in PCs, has a long carboxyl (C)-terminal domain that interacts with Homer scaffolding proteins. Cerebellar roles of the C-terminal domain at both synaptic and behavior levels remain poorly understood. To address this question, we introduced a short variant, mGluR1b, which lacks this domain into PCs of mGluR1-knock-out (KO) mice (mGluR1b-rescue mice). In mGluR1b-rescue mice, mGluR1b showed dispersed perisynaptic distribution in PC spines. Importantly, mGluR1b-rescue mice exhibited impairments in inositol 1,4,5-trisphosphate receptor (IP3R)-mediated Ca(2+) release, CF synapse elimination, LTD induction, and delay eyeblink conditioning: they showed normal transient receptor potential canonical (TRPC) currents and normal motor coordination. In contrast, PC-specific rescue of mGluR1a restored all cerebellar defects of mGluR1-KO mice. We conclude that the long C-terminal domain of mGluR1a is required for the proper perisynaptic targeting of mGluR1, IP3R-mediated Ca(2+) release, CF synapse elimination, LTD, and motor learning, but not for TRPC currents and motor coordination. PMID:24523559

Ohtani, Yoshiaki; Miyata, Mariko; Hashimoto, Kouichi; Tabata, Toshihide; Kishimoto, Yasushi; Fukaya, Masahiro; Kase, Daisuke; Kassai, Hidetoshi; Nakao, Kazuki; Hirata, Tatsumi; Watanabe, Masahiko; Kano, Masanobu; Aiba, Atsu

2014-02-12

229

Are carboxyl groups the most acidic sites in amino acids? Gas-phase acidities, photoelectron spectra, and computations on tyrosine, p-hydroxybenzoic acid, and their conjugate bases.  

PubMed

Deprotonation of tyrosine in the gas phase was found to occur preferentially at the phenolic site, and the conjugate base consists of a 70:30 mixture of phenoxide and carboxylate anions at equilibrium. This result was established by developing a chemical probe for differentiating these two isomers, and the presence of both ions was confirmed by photoelectron spectroscopy. Equilibrium acidity measurements on tyrosine indicated that deltaG(acid)(o) = 332.5 +/- 1.5 kcal mol(-1) and deltaH(acid)(o) = 340.7 +/- 1.5 kcal mol(-1). Photoelectron spectra yielded adiabatic electron detachment energies of 2.70 +/- 0.05 and 3.55 +/- 0.10 eV for the phenoxide and carboxylate anions, respectively. The H/D exchange behavior of deprotonated tyrosine was examined using three different alcohols (CF3CH2OD, C6H5CH2OD, and CH3CH2OD), and incorporation of up to three deuterium atoms was observed. Two pathways are proposed to account for these results, and all of the experimental findings are supplemented with B3LYP/aug-cc-pVDZ and G3B3 calculations. In addition, it was found that electrospray ionization of tyrosine from a 3:1 (v/v) CH3OH/H2O solution using a commercial source produces a deprotonated [M-H]- anion with the gas-phase equilibrium composition rather than the structure of the ion that exists in aqueous media. Electrospray ionization from acetonitrile, however, leads largely to the liquid-phase (carboxylate) structure. A control molecule, p-hydroxybenzoic acid, was found to behave in a similar manner. Thus, the electrospray conditions that are employed for the analysis of a compound can alter the isomeric composition of the resulting anion. PMID:19115946

Tian, Zhixin; Wang, Xue-Bin; Wang, Lai-Sheng; Kass, Steven R

2009-01-28

230

1-Aza-niumyl-cyclo-butane-1-carboxyl-ate monohydrate  

PubMed Central

In the title compound, C5H9NO2·H2O, the amino acid is in the usual zwitterionic form involving the ?-carboxyl­ate group. The cyclo­butane backbone of the amino acid is disordered over two conformations, with occupancies of 0.882?(7) and 0.118?(7). In the crystal, N—H?O and O—H?O hydrogen bonds link the zwitterions [with the water molecule involved as both acceptor (with the NH3 +) and donor (through a single carboxylate O from two different aminocyclobutane carb­oxylate moities)], resulting in a two-dimensional layered structure lying parallel to (100).

Butcher, Ray J.; Brewer, Greg; Burton, Aaron S.; Dworkin, Jason P.

2014-01-01

231

rac-2-Amino-pyridinium cis-2-carb-oxy-cyclo-hexane-1-carboxyl-ate  

PubMed Central

In the structure of the title compound, C5H7N2 +·C8H11O4 ?, the cis anions associate through head-to-tail carb­oxy­lic acid–carboxyl O—H?O hydrogen bonds [graph set C(7)], forming chains which extend along c and are inter­linked through the carboxyl groups, forming cyclic R 2 2(8) associations with the pyridinium and an amine H-atom donor of the cation. Further amine–carboxyl N—H?O inter­actions form enlarged centrosymmetric rings [graph set R 4 4(18)] and extensions down b, giving a three-dimensional structure.

Smith, Graham; Wermuth, Urs D.

2011-01-01

232

Mass spectrometry-based carboxyl footprinting of proteins: Method evaluation  

Microsoft Academic Search

Protein structure determines function in biology, and a variety of approaches have been employed to obtain structural information about proteins. Mass spectrometry-based protein footprinting is one fast-growing approach. One labeling-based footprinting approach is the use of a water-soluble carbodiimide, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) and glycine ethyl ester (GEE) to modify solvent-accessible carboxyl groups on glutamate (E) and aspartate (D). This paper describes

Hao Zhang; Jianzhong Wen; Richard Y. C. Huang; Robert E. Blankenship; Michael L. Gross

233

On the construction of Kramers paired double group symmetry functions  

NASA Astrophysics Data System (ADS)

Relativistic quantum chemical calculations on molecular systems can greatly be expedited by making use of the full molecular symmetry, including both double point group and time-reversal symmetry. A simple yet general scheme is proposed here to make double point group symmetry functions also form Kramers pairs such that the resulting operator matrices have the desired structure (i.e., quaternion, complex, or real). The key idea is to insert appropriate phase factors into the symmetry functions or make a suitable unitary transformation of them. Arbitrary finite double point groups can be handled in the same way. As for a product basis, the same symmetrization can be achieved by simple modifications of the vector coupling (Clebsch-Gordan) coefficients. This is especially of interest to, e.g., time-dependent relativistic density functional linear response theory or relativistic two-electron repulsion integral evaluations in general. Several examples are provided to illustrate the algorithm and its efficiency.

Peng, Daoling; Ma, Jianyi; Liu, Wenjian

234

Surface functional group dependent apatite formation on bacterial cellulose microfibrils network in a simulated body fluid.  

PubMed

The apatite forming ability of biopolymer bacterial cellulose (BC) has been investigated by soaking different BC specimens in a simulated body fluid (1.5 SBF) under physiological conditions, at 37 degrees C and pH 7.4, mimicking the natural process of apatite formation. From ATR-FTIR spectra and ICP-AES analysis, the crystalline phase nucleated on the BC microfibrils surface was calcium deficient carbonated apatite through initial formation of octacalcium phosphate (OCP) or OCP like calcium phosphate phase regardless of the substrates. Morphology of the deposits from SEM, FE-SEM, and TEM observations revealed the fine structure of thin film plates uniting together to form apatite globules of various size (from <1 mum to 3 mum) with respect to the substrates. Surface modification by TEMPO (2,2,6,6-tetramethylpyperidine-1-oxyl)-mediated oxidation, which can readily form active carboxyl functional groups upon selective oxidation of primary hydroxyl groups on the surface of BC microfibrils, enhanced the rate of apatite nucleation. Ion exchanged treatment with calcium chloride solution after TEMPO-mediated oxidation was found to be remarkably different from other BC substrates with the highest deposit weight and the smallest apatite globules size. The role of BC substrates to induce mineralization rate differs according to the nature of the BC substrates, which strongly influences the growth behavior of the apatite crystals. PMID:17111406

Nge, Thi Thi; Sugiyama, Junji

2007-04-01

235

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

NASA Technical Reports Server (NTRS)

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 degrees C and 76 degrees C or heat-shocked at 85 degrees C by using immunofluorescence microscopy and in thick sections of rapidly frozen cells grown at 76 degrees 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 degrees 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 degrees C and 76 degrees C or heat-shocked at 85 degrees 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

236

From Infinite to Two Dimensions through the Functional Renormalization Group.  

PubMed

We present a novel scheme for an unbiased, nonperturbative treatment of strongly correlated fermions. The proposed approach combines two of the most successful many-body methods, the dynamical mean field theory and the functional renormalization group. Physically, this allows for a systematic inclusion of nonlocal correlations via the functional renormalization group flow equations, after the local correlations are taken into account nonperturbatively by the dynamical mean field theory. To demonstrate the feasibility of the approach, we present numerical results for the two-dimensional Hubbard model at half filling. PMID:24877952

Taranto, C; Andergassen, S; Bauer, J; Held, K; Katanin, A; Metzner, W; Rohringer, G; Toschi, A

2014-05-16

237

From Infinite to Two Dimensions through the Functional Renormalization Group  

NASA Astrophysics Data System (ADS)

We present a novel scheme for an unbiased, nonperturbative treatment of strongly correlated fermions. The proposed approach combines two of the most successful many-body methods, the dynamical mean field theory and the functional renormalization group. Physically, this allows for a systematic inclusion of nonlocal correlations via the functional renormalization group flow equations, after the local correlations are taken into account nonperturbatively by the dynamical mean field theory. To demonstrate the feasibility of the approach, we present numerical results for the two-dimensional Hubbard model at half filling.

Taranto, C.; Andergassen, S.; Bauer, J.; Held, K.; Katanin, A.; Metzner, W.; Rohringer, G.; Toschi, A.

2014-05-01

238

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

2013-05-01

239

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

240

Functional renormalization group approach to correlated fermion systems  

NASA Astrophysics Data System (ADS)

Numerous correlated electron systems exhibit a strongly scale-dependent behavior. Upon lowering the energy scale, collective phenomena, bound states, and new effective degrees of freedom emerge. Typical examples include (i) competing magnetic, charge, and pairing instabilities in two-dimensional electron systems; (ii) the interplay of electronic excitations and order parameter fluctuations near thermal and quantum phase transitions in metals; and (iii) correlation effects such as Luttinger liquid behavior and the Kondo effect showing up in linear and nonequilibrium transport through quantum wires and quantum dots. The functional renormalization group is a flexible and unbiased tool for dealing with such scale-dependent behavior. Its starting point is an exact functional flow equation, which yields the gradual evolution from a microscopic model action to the final effective action as a function of a continuously decreasing energy scale. Expanding in powers of the fields one obtains an exact hierarchy of flow equations for vertex functions. Truncations of this hierarchy have led to powerful new approximation schemes. This review is a comprehensive introduction to the functional renormalization group method for interacting Fermi systems. A self-contained derivation of the exact flow equations is presented and frequently used truncation schemes are described. Reviewing selected applications it is shown how approximations based on the functional renormalization group can be fruitfully used to improve our understanding of correlated fermion systems.

Metzner, Walter; Salmhofer, Manfred; Honerkamp, Carsten; Meden, Volker; Schönhammer, Kurt

2012-01-01

241

Species, functional groups, and thresholds in ecological resilience  

USGS Publications Warehouse

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.

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

2012-01-01

242

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

243

Direct functionalization of the hydroxyl group of the 6-mercapto-1-hexanol (MCH) ligand attached to gold nanoclusters.  

PubMed

Au-MCH nanoclusters of (1.5 +/- 0.3) nm diameter (MCH = 6-mercapto-1-hexanol, HS-(CH2)6-OH) have been prepared and characterized by Transmission Electron Microscopy (TEM), UV-visible, Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared (FTIR) absorption spectroscopies, X-ray Powder Diffraction (XRD), and Thermogravimetric Analysis (TGA). While in nanocluster form dispersed in solution, the OH terminal group of the MCH ligand has been directly functionalized through small organic molecule reactions in near-quantitative yield (>90%) to generate ester, carbamate, carboxylic acid, nitrite, and aldehyde groups, as recorded by FTIR spectroscopy. The size of the final gold nanocluster derivative is preserved for all the reactions studied here. PMID:17064127

Tan, Hua; Zhan, Tong; Fan, Wai Yip

2006-11-01

244

Synthetic control of isolated, single functional groups on silica surfaces.  

PubMed

We report control of the density of isolated, single functional groups in homogeneously mixed trichloroalkyl silanes on various silica surfaces. The functional groups are covalently bound to a silane derived from the Rink resin. This Rink-silane is reactive to any nucleophile. Control over the density of functional groups is achieved by diluting the immersion solution containing the Rink-silane with an inert silane, octadecyltrichlorsilane. The isolated nature of the functional groups is confirmed by the stochastic blinking of fluorescent single boron-dipyrromethane dyes imaged in total internal reflection geometry. The robust character of silane monolayers allows facile covalent binding and cleavage of molecular species from silica surfaces as well as general synthetic transformations to be conducted. This is shown by the covalent attachment and then cleavage of a naphthalene chromophore. This low-cost and scalable platform has great potential for use in sensing, molecular electronics, semiconductor processing, and the investigation of fundamental processes in catalysis and the kinetics of molecular association. PMID:24856635

Dagg, Alexander P; Huang, Zhiyuan; Marks, Monica A; Zhou, Dapeng; Chawla, Megha; Tang, Ming L

2014-06-24

245

Receptor Site Labeling through Functional Groups. Barbital and Amphetamine Derivatives.  

National Technical Information Service (NTIS)

A probe for a drug receptor site can be assembled from a fragment (D) derived from a drug of proven biological activity, a connection of variable length and character (Cn), and a moiety (Y) capable of reactivity toward a limited set of functional groups (...

E. M. Kosower N. S. Kosower T. Miyadera

1970-01-01

246

Coordination modes of bridge carboxylates in dinuclear manganese compounds determine their catalase-like activities.  

PubMed

To explore the role of bridge carboxylate coordination modes on the catalase-like activities of dinuclear manganese compounds, [Mn(II)2(bpmapa)2(H2O)2](ClO4)2 (1), [Mn(II)2(pbpmapa)2(H2O)2](ClO4)2 (2), and [Mn(II)2(bpmaa)2(H2O)3](ClO4)2 (3) (bpmapa = [bis(2-pyridylmethyl)amino]propionic acid, pbpmapa = alpha-phenyl-beta-[bis(2-pyridylmethyl)amino]propionic acid, and bpmaa = [bis(2-pyridylmethyl)amino]acetic acid), in which Mn(II)-Mn(II) centers have a similar coordination sphere but different carboxylate-Mn bridging modes have been synthesized and structurally characterized by single X-ray diffraction, UV-visible, IR, and EPR spectroscopies, and their catalase-like activities were investigated. Studies of their catalytic activities and the influence of the nitrogenous bases on their catalytic activities indicated that the carboxylate-Mn coordination mode was crucial in H2O2 deprotonation, and eventually in H2O2 disproportionation. Compound 1 with a bidentate carboxylate bridge showed higher catalase-like activity than 2 and 3, in which the carboxylate groups have a monodentate bridging mode. The deprotonation ability of the carboxylate anion was determined by the O-C-O angle and the distance between the weakly bound oxygen of the bridging carboxylate to the manganese ion. The smaller the angle, and the shorter the distance, the stronger the basicity that the carboxylate anion exhibits. The bidentate mu-1,1 bridging coordination mode functionally mimicked the glutamate residues at the manganese catalase active site. Our results suggested that increasing the basicity of the bridging carboxylate ligand of the catalase model compounds will increase their deprotonation ability and lead to more active catalase mimics. PMID:19809747

Jiang, Xiaojun; Liu, Hui; Zheng, Bing; Zhang, Jingyan

2009-10-28

247

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

248

Functional complementation of truncated human skeletal-muscle chloride channel (hClC-1) using carboxyl tail fragments  

PubMed Central

Crystal structures of bacterial CLC (voltage-gated chloride channel family) proteins suggest the arrangement of permeation pores and possible gates in the transmembrane region of eukaryotic CLC channels. For the extensive cytoplasmic tails of eukaryotic CLC family members, however, there are no equivalent structural predictions. Truncations of cytoplasmic tails in different places or point mutations result in loss of function or altered gating of several members of the CLC family, suggesting functional importance. In the present study, we show that deletion of the terminal 100 amino acids (N889X) in human ClC-1 (skeletal-muscle chloride channel) has minor consequences, whereas truncation by 110 or more amino acids (from Q879X) destroys channel function. Use of the split channel strategy, co-injecting mRNAs and expressing various complementary constructs in Xenopus oocytes, confirms the importance of the Gln879–Arg888 sequence. A split between the two CBS (cystathionine ?-synthase) domains (CBS1 and CBS2) gives normal function (e.g. G721X plus its complement), whereas a partial complementation, eliminating the CBS1 domain, eliminates function. Surprisingly, function is retained even when the region Gly721–Ala862 (between CBS1 and CBS2, and including most of the CBS2 domain) is omitted from the complementation. Furthermore, even shorter peptides from the CBS2-immediate post-CBS2 region are sufficient for functional complementation. We have found that just 26 amino acids from Leu863 to Arg888 are necessary since channel function is restored by co-expressing this peptide with the otherwise inactive truncation, G721X.

Wu, Weiping; Rychkov, Grigori Y.; Hughes, Bernard P.; Bretag, Allan H.

2005-01-01

249

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

PubMed

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. PMID:21931320

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

2012-10-01

250

Isolation and characterization of a ?1-pyrroline-5-carboxylate synthetase (NtP5CS) from Nitraria tangutorum Bobr. and functional comparison with its Arabidopsis homologue.  

PubMed

Several functional and regulatory proteins play important roles in controlling plant stress tolerance. Proline (Pro) is one of the most accumulated osmolytes correlated with tolerance to stresses. ?(1)-Pyrroline-5-carboxylate synthetase (P5CS) is a rate-limiting enzyme in Pro biosynthesis. In the present study, we isolated the cDNA for a P5CS gene (NtP5CS) from the halophyte Nitraria tangutorum. Phylogenetic analysis and subcellular localization analysis of NtP5CS-GFP protein in onion cells showed that NtP5CS was a new P5CS gene and was involved in Pro synthesis in N. tangutorum. Expression of the NtP5CS gene was induced by salt stress, dehydration, and high and low temperatures. Escherichia coli overexpressing AtP5CS or NtP5CS exhibited better growth in all treatments, including high salinity, high alkalinity, dehydration, osmotic, heat and cold stresses. Additionally, NtP5CS recombinant E. coli cells grew better than did AtP5CS recombinant cells in response to abiotic stresses. Our data demonstrate that the P5CS from a halophytic species functions more efficiently than its homologue from a glycophytic species in improving the stress tolerance of E. coli. PMID:24338163

Zheng, Linlin; Dang, Zhenhua; Li, Haoyu; Zhang, Huirong; Wu, Shubiao; Wang, Yingchun

2014-01-01

251

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

252

The UAT Groups Project: HI Deficiency and Mass Function for Galaxies in Groups  

NASA Astrophysics Data System (ADS)

We present the HI deficiencies of galaxies in a sample of ten well-studied groups that form a subset of the Arecibo Legacy Fast-ALFA (ALFALFA) survey. We expect the HI content of galaxies in groups to reflect the strong galaxy-galaxy interactions that are likely to take place in these dense, but low velocity dispersion environments; HI gas may, for example, be tidally drawn out, merged with other galaxies, or destroyed in starbursts. We find that, despite strong morphological segregation (with early-type galaxies dominating the centers of the groups) , most late-type massive galaxies near the center exhibit only slightly depressed levels of HI relative to late-type galaxies in the outskirts. Similarly, the HI mass function for these groups is consistent with that for the full ALFALFA survey, despite the clear difference in galaxy populations across environments.

Egner, Joanna; Crone-Odekon, M.; Raskin, M.; Undergraduate ALFALFA Team

2014-01-01

253

Functional group interactions of a 5-HT3R antagonist  

PubMed Central

Background Lerisetron, a competitive serotonin type 3 receptor (5-HT3R) antagonist, contains five functional groups capable of interacting with amino acids in the 5-HT3R binding site. Site directed mutagenesis studies of the 5-HT3AR have revealed several amino acids that are thought to form part of the binding domain of this receptor. The specific functional groups on the ligand that interact with these amino acids are, however, unknown. Using synthetic analogs of lerisetron as molecular probes in combination with site directed mutagenesis, we have identified some of these interactions and have proposed a model of the lerisetron binding site. Results Two analogs of lerisetron were synthesized to probe 5-HT3R functional group interactions with this compound. Analog 1 lacks the N1 benzyl group of lerisetron and analog 2 contains oxygen in place of the distal piperazine nitrogen. Both analogs show significantly decreased binding affinity to wildtype 5-HT3ASRs. Mutations at W89, R91, Y142 and Y152 produced significant decreases in binding compared to wildtype receptors. Binding affinities of analogs 1 and 2 were altered only by mutations at W89, and Y152. Conclusions Based on the data obtained for lerisetron and analogs 1 and 2, we have proposed a tentative model of the lerisetron binding pocket of the 5-HT3ASR. According to this model, The N-benzyl group interacts in a weak interaction with R91 while the benzimidazole group interacts with W89. Our data support an interaction of the distal amino nitrogen with Y142 and Y152.

Venkataraman, Padmavati; Joshi, Prasad; Venkatachalan, Srinivasan P; Muthalagi, Mani; Parihar, Harish S; Kirschbaum, Karen S; Schulte, Marvin K

2002-01-01

254

The Conversion of Carboxylic Acids to Ketones: A Repeated Discovery  

NASA Astrophysics Data System (ADS)

This article describes the history of the reaction converting carboxylic acids to ketones. The reaction has been rediscovered several times, yet has actually been known for centuries. The best known version of the process is the Dakin West reaction (1928), which applies to ?-amino acids and also involves the simultaneous conversion of the amine group to amido functionality. Unlike other examples, this particular reaction has attracted a reasonable amount of attention and it appears to be better known than the conversion of simple carboxylic acids to ketones. However, this reaction was described as long ago as 1612, when Beguin published an account of it in his book, Tyrocinium Chymicum . Since then, many chemists have rediscovered the reaction, apparently independently. One of the earliest modern accounts was by W. H. Perkin, Sr., in 1886, who made various simple ketones by refluxing the appropriate carboxylic acids with base. However, this work has been largely ignored, including by his son, W. H. Perkin, Jr., who used a more complicated base-catalyzed ketonization to prepare small ring compounds in the early years of the 20th century. Other articles detailing the application of ketonization to organic acids are discussed, including our own work, which employed the process to crosslink carboxylated polymers for possible technical application in coatings. Despite its relative obscurity, the reaction was used by Woodward et al. in the total synthesis of strychnine, reported in 1963, and this is discussed in detail at the end of the article. See Featured Molecules .

Nicholson, John W.; Wilson, Alan

2004-09-01

255

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

256

Groups as units of functional analysis, individuals as proximate mechanisms.  

PubMed

Whenever selection operates at a given level of a multitier hierarchy, units at that level should become the object of functional analysis, and units at lower levels should be studied as proximate mechanisms. This intuition already exists for the study of genes in individuals, when individuals are the unit of selection. It is only beginning to be applied for the study of individuals in groups, when groups are the unit of selection. Smaldino's target article is an important step in this direction with an emphasis on human cultural evolution, but the same algorithm applies to all multilevel evolutionary processes. PMID:24970426

Wilson, David Sloan

2014-06-01

257

Effect of Functional Group and Carbon Chain Length on the Odor Detection Threshold of Aliphatic Compounds  

PubMed Central

Odor detection thresholds (ODTs) are used for assessing outdoor and indoor air quality. They are obtained experimentally by olfactometry and psychophysical methods, and large compilations are available in the literature. A non-linear regression equation was fitted to describe the ODT variability of 114 aliphatic compounds based on the alkyl chain length for different homologous series (carboxylic acids, aldehydes, 2-ketones, esters, 1-alcohols, amines, thiols, thioethers and hydrocarbons). The resulting equation reveals an effect of the functional group, molecular size and also an interaction between both factors. Although the mechanistic interpretation of results is uncertain, the relatively high goodness-of-fit (R2 = 0.90) suggests that ODT values of aliphatic compounds can be predicted rather accurately, which is not the case for rigid molecules. This equation may serve as a basis for the development of more complex ODT models taking into account diverse structural features of odorants. The variability of power-law exponents was also investigated for the homologous series.

Zarzo, Manuel

2012-01-01

258

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

259

Improved synthesis of DCDHF fluorophores with maleimide functional groups  

PubMed Central

A group of dicyanodihydrofuran (DCDHF) fluorophores with thiol-reactive maleimide functionality has been synthesized. One of the methods involves aromatic nucleophilic substitution reaction between an arylfluoride containing DCDHF and an amine containing protected maleimide. An alternative and generally useful method involves combination of the Mitsunobu reaction of a DCDHF-OH with a furan or 2-methylfuran protected maleimide and then subsequent retro Diels–Alder reaction.

Lu, Zhikuan; Weber, Ryan; Twieg, Robert J.

2008-01-01

260

Extensions of Positive Definite Functions on Amenable Groups  

Microsoft Academic Search

Let $S$ be a subset of a amenable group $G$ such that $e\\\\in S$ and\\u000a$S^{-1}=S$. The main result of the paper states that if the Cayley graph of $G$\\u000awith respect to $S$ has a certain combinatorial property, then every positive\\u000adefinite operator-valued function on $S$ can be extended to a positive definite\\u000afunction on $G$. Several known extension

M. Bakonyi; D. Timotin

2010-01-01

261

Polycomb Group Proteins Are Key Regulators of Keratinocyte Function  

Microsoft Academic Search

The Polycomb group (PcG) proteins are epigenetic suppressors of gene expression that function through modification of histones to change chromatin structure and modulate gene expression and cell behavior. Recent studies show that PcG proteins are expressed in epidermis, that their levels change during differentiation and in disease states, and that PcG expression is regulated by agents that influence cell proliferation

Richard L Eckert; Gautam Adhikary; Ellen A Rorke; Yap Ching Chew; Sivaprakasam Balasubramanian

2011-01-01

262

Room temperature decarboxylative trifluoromethylation of ?,?-unsaturated carboxylic acids by photoredox catalysis.  

PubMed

A visible-light-induced decarboxylative trifluoromethylation of ?,?-unsaturated carboxylic acids, which uses the Togni reagent as the CF3 source is disclosed. The corresponding trifluoromethylated alkenes were obtained in moderate to high yields with excellent functional group tolerance at ambient temperature. Preliminary mechanistic analyses suggest a radical-type mechanism. PMID:24445904

Xu, Pan; Abdukader, Ablimit; Hu, Kaidong; Cheng, Yixiang; Zhu, Chengjian

2014-03-01

263

The melanocortin-1 receptor carboxyl terminal pentapeptide is essential for MC1R function and expression on the cell surface  

Microsoft Academic Search

The pigmentary actions of the melanocortins are mediated by the melanocortin-1 receptor (MC1R), a seven transmembrane domains receptor positively coupled to Gs and the cAMP cascade. In order to define the structure–function relationships of potentially relevant domains in MC1R, particularly its C-terminal cytosolic tail, we generated and analyzed several variants with C-terminal deletions, as well as point mutants in selected

J. Sánchez-Más; B. L. Sánchez-Laorden; L. A. Guillo; C. Jiménez-Cervantes; J. C. García-Borrón

2005-01-01

264

Correlation functions for pairs and groups of galaxies  

NASA Technical Reports Server (NTRS)

There are many studies on the correlation functions of galaxies, of clusters of galaxies, even of superclusters (e.g., Groth and Peebles 1977; Davies and Peebles 1983; Kalinkov and Kuneva 1985, 1986; Bahcall 1988 and references therein) but not so many on pairs and groups of galaxies. Results of the calculations of two-point correlation fuctions for some catalogs of pairs and groups of galaxies are given. It is assumed that the distances to pairs and groups of galaxies are given by their mean redshifts according to R = sigma (sup n, sub i-1) V sub i/nH (sub 0), where n is the number of galaxies in the system and H sub 0 = 100 km s(exp -1) Mpc(exp -1).

Kalinkov, M.; Kuneva, I.

1990-01-01

265

An efficient tandem approach for the synthesis of functionalized 2-pyridone-3-carboxylic acids using three-component reaction in aqueous media.  

PubMed

Novel analogs of 2-pyridone-3-carboxylic acids 4a-l have been prepared by the three-component reaction of 3-formyl chromone, Meldrum's acid, and primary amines in the presence of a catalytic amount of diammonium hydrogen phosphate in water. Good-to-high yields, easy work-up, and an environmentally friendly profile are the advantages of this method for the synthesis of 2-pyridone-3-carboxylic acid derivatives. PMID:24792225

Mehrparvar, Saber; Balalaie, Saeed; Rabbanizadeh, Mahnaz; Ghabraie, Elmira; Rominger, Frank

2014-08-01

266

Pyruvate carboxylation in neurons.  

PubMed

Carboxylation of pyruvate in the brain was for many years thought to occur only in glia, an assumption that formed much of the basis for the concept of the glutamine cycle. It was shown recently, however, that carboxylation of pyruvate to malate occurs in neurons and that it supports formation of transmitter glutamate. The role of pyruvate carboxylation in neurons is to ensure tricarboxylic acid cycle activity by compensating for losses of alpha-ketoglutarate that occur through release of transmitter glutamate and GABA; these amino acids are alpha-ketoglutarate derivatives. Available data suggest that neuronal pyruvate carboxylation is quantitatively important. But because there is no net CO(2) fixation in the brain, pyruvate carboxylation must be balanced by decarboxylation of malate or oxaloacetate. Such decarboxylation occurs in both neurons and astrocytes. Several in vitro studies have shown a neuroprotective effect of pyruvate supplementation. Pyruvate carboxylation may be one mechanism through which such treatment is effective, because pyruvate carboxylation through malic enzyme is active during energy deficiency and leads to an increase in the level of dicarboxylates that can be metabolized through the tricarboxylic acid cycle for ATP production. PMID:11746399

Hassel, B

2001-12-01

267

Nanoparticles made of multi-block copolymer of lactic acid and ethylene glycol containing periodic side-chain carboxyl groups for oral delivery of cyclosporine A  

PubMed Central

The purpose of this study was to evaluate the potential of new carboxylated multi-block copolymer of lactic acid and ethylene glycol (EL14) for nanoparticle (NP) formation and their ability to deliver high molecular weight hydrophobic drug—cyclosporine A (CsA). CsA-loaded EL14 NPs were compared with traditional poly(lactide-co-glycolide) (PLGA) NPs, both prepared by emulsion–diffusion–evaporation process. On the one hand, the increase in drug payload from 10 to 30 per cent for EL14 NPs showed no difference in particle size, however the entrapment efficiency tends to decrease from 50 to 43 per cent; on the other hand, the more hydrophobic PLGA showed an increasing trend in entrapment efficiency from 20 to 62 per cent with increasing particle size. Over 90 per cent of CsA was released in vitro from both the nanoparticulates; however, the release was much slower in the case of more hydrophobic PLGA. On in vivo evaluation in rats, the NPs made of EL14 showed a higher Cmax, a faster Tmax and enhanced tissue levels to that of PLGA that are crucial for CsA's activity and toxicity; however, the overall bioavailability of the nanoparticulates was similar and higher than Neoral. Together these data demonstrate the feasibility of NPs made of low molecular weight, hydrophilic polymer EL14 for efficient delivery of CsA.

Ankola, D. D.; Battisti, A.; Solaro, R.; Kumar, M. N. V. Ravi

2010-01-01

268

[The functional status of sailors from different job groups].  

PubMed

Taking into account different professional duties and peculiarities of combat training all servicemen are working in different conditions that obviously reflects on their functional state. Submarine personnel with its prolonged stay in technogenic environment is exposed to continuous stresses, basically of emotional genesis, which is aggravated by hypokinesia and hypodynamia in the conditions of sensor deprivation and chronostress. As for skin divers who are working in natural environment, they are basically withstand periodic and short-time loads with domination of physical component. During these studies 17 submariners and 9 frogmen (age 19-24) were examined in the conditions of their routine combat training in the North Europe region. It was found out that functional state of divers was considerably better than of submariners. It proves the detriment influence of specialized adaptation and also demonstrates the differences in functional state of seamen from different professional groups. PMID:7571502

Shatalov, A I; Myznikov, I L; Obaturov, A A

1995-06-01

269

The numerically optimized regulator and the functional renormalization group  

NASA Astrophysics Data System (ADS)

We aim to optimize the functional form of the compactly supported smooth (CSS) regulator within the functional renormalization group (RG), in the framework of bosonized two-dimensional quantum electrodynamics (QED2) and of the three-dimensional O(N = 1) scalar field theory in the local potential approximation (LPA). The principle of minimal sensitivity (PMS) is used for the optimization of the CSS regulator, recovering all the major types of regulators in appropriate limits. Within the investigated class of functional forms, a thorough investigation of the CSS regulator, optimized with two different normalizations within the PMS method, confirms that the functional form of a regulator first proposed by Litim is optimal within the LPA. However, Litim’s exact form leads to a kink in the regulator function. A form of the CSS regulator, numerically close to Litim’s limit while maintaining infinite differentiability, remains compatible with the gradient expansion to all orders. A smooth analytic behavior of the regulator is ensured by a small, but finite value of the exponential fall-off parameter in the CSS regulator. Consequently, a compactly supported regulator, in a parameter regime close to Litim’s optimized form, but regularized with an exponential factor, appears to have favorable properties and could be used to address the scheme dependence of the functional RG, at least within the approximations employed in the studies reported here.

Márián, I. G.; Jentschura, U. D.; Nándori, I.

2014-05-01

270

Enhanced selectivity of CO(2) over CH(4) in sulphonate-, carboxylate- and iodo-functionalized UiO-66 frameworks.  

PubMed

Three new functionalized UiO-66-X (X = -SO(3)H, 1; -CO(2)H, 2; -I; 3) frameworks incorporating BDC-X (BDC: 1,4-benzenedicarboxylate) linkers have been synthesized by a solvothermal method using conventional electric heating. The as-synthesized (AS) as well as the thermally activated compounds were characterized by X-ray powder diffraction (XRPD), diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, thermogravimetric (TG), and elemental analysis. The occluded H(2)BDC-X molecules can be removed by exchange with polar solvent molecules followed by thermal treatment under vacuum leading to the empty-pore forms of the title compounds. Thermogravimetric analysis (TGA) and temperature-dependent XRPD (TDXRPD) experiments indicate that 1, 2 and 3 are stable up to 260, 340 and 360 °C, respectively. The compounds maintain their structural integrity in water, acetic acid and 1 M HCl, as verified by XRPD analysis of the samples recovered after suspending them in the respective liquids. As confirmed by N(2), CO(2) and CH(4) sorption analyses, all of the thermally activated compounds exhibit significant microporosity (S(Langmuir): 769-842 m(2) g(-1)), which are comparable to that of the parent UiO-66 compound. Compared to the unfunctionalized UiO-66 compound, all the three functionalized solids possess higher ideal selectivity in adsorption of CO(2) over CH(4) at 33 °C. PMID:23361454

Biswas, Shyam; Zhang, Jian; Li, Zhibao; Liu, Ying-Ya; Grzywa, Maciej; Sun, Lixian; Volkmer, Dirk; Van Der Voort, Pascal

2013-04-01

271

Structural and functional characterization of the human NBC3 sodium/bicarbonate co-transporter carboxyl-terminal cytoplasmic domain.  

PubMed

The sodium bicarbonate co-transporter, NBC3, is expressed in a range of tissues including heart, skeletal muscle and kidney, where it modulates intracellular pH and bicarbonate levels. NBC3 has a three-domain structure: 67 kDa N-terminal cytoplasmic domain, 57 kDa membrane domain and an 11 kDa C-terminal cytoplasmic domain (NBC3Ct). The role of C-terminal domains as important regulatory regions is an emerging theme in bicarbonate transporter physiology. This study determined the functional role of human NBC3Ct and characterized its structure using biochemical techniques. The NBC3 C-terminal domain deletion mutant (NBC3DeltaCt) had only 12 +/- 5% of wild-type transport activity. This low activity is attributable to low steady-state levels of NBC3DeltaCt and almost complete retention inside the cell, as assessed by immunoblots and confocal microscopy, suggesting a role of NBC3Ct in cell surface processing. To characterize the structure of NBC3Ct, amino acids 1127-1214 of NBC3 were expressed as a GST fusion protein (GST.NBC3Ct). GST.NBC3Ct was cleaved with PreScission Protease and native NBC3Ct could be purified to 94% homogeneity. Gel permeation chromatography and sedimentation velocity ultracentrifugation of NBC3Ct indicated a Stokes radius of 26 and 30 angstroms, respectively. Shape modelling revealed NBC3Ct as a prolate shape with long and short axes of 19 and 2 nm, respectively. The circular dichroism spectra of NBC3Ct did not change over the pH 6.2-7.8 range, which rules out a large change of secondary structure as a component of pH sensor function. Proteolysis with trypsin and chymotrypsin identified two proteolytically sensitive regions, R1129 and K1183-K1186, which could form protein interaction sites. PMID:14578046

Loiselle, Frederick B; Jaschke, Paul; Casey, Joseph R

2003-01-01

272

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

273

The Set2 histone methyltransferase functions through the phosphorylated carboxyl-terminal domain of RNA polymerase II.  

PubMed

The histone methyltransferase Set2, which specifically methylates lysine 36 of histone H3, has been shown to repress transcription upon tethering to a heterologous promoter. However, the mechanism of targeting and the consequence of Set2-dependent methylation have yet to be demonstrated. We sought to identify the protein components associated with Set2 to gain some insights into the in vivo function of this protein. Mass spectrometry analysis of the Set2 complex, purified using a tandem affinity method, revealed that RNA polymerase II (pol II) is associated with Set2. Immunoblotting and immunoprecipitation using antibodies against subunits of pol II confirmed that the phosphorylated form of pol II is indeed an integral part of the Set2 complex. Gst-Set2 preferentially binds to CTD synthetic peptides phosphorylated at serine 2, and to a lesser extent, serine 5 phosphorylated peptides, but has no affinity for unphosphorylated CTD, suggesting that Set2 associates with the elongating form of the pol II. Furthermore, we show that set2Delta ppr2Delta double mutants (PPR2 encodes TFIIS, a transcription elongation factor) are synthetically hypersensitive to 6-azauracil, and that deletions in the CTD reduce in vivo levels of H3 lysine 36 methylation. Collectively, these results suggest that Set2 is involved in regulating transcription elongation through its direct contact with pol II. PMID:12511561

Li, Bing; Howe, LeAnn; Anderson, Scott; Yates, John R; Workman, Jerry L

2003-03-14

274

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

275

Characterization of three new carboxylic ester hydrolases isolated by functional screening of a forest soil metagenomic library.  

PubMed

Three new lipolytic genes were isolated from a forest soil metagenomic library by functional screening on tributyrin agar plates. The genes SBLip1, SBLip2 and SBLip5.1 respectively encode polypeptides of 445, 346 and 316 amino acids. Phylogenetic analyses revealed that SBLip2 and SBLip5.1 belong to bacterial esterase/lipase family IV, whereas SBLip1 shows similarity to class C ?-lactamases and is thus related to esterase family VIII. The corresponding genes were overexpressed and their products purified by affinity chromatography for characterization. Analyses of substrate specificity with different p-nitrophenyl esters showed that all three enzymes have a preference for short-acyl-chain p-nitrophenyl esters, a feature of carboxylesterases as opposed to lipases. The ?-lactamase activity of SBLip1, measured with the chromogenic substrate nitrocefin, was very low. The three esterases have the same optimal pH (pH 10) and remain active across a relatively broad pH range, displaying more than 60 % activity between pH 6 and 10. The temperature optima determined were 35 °C for SBLip1, 45 °C for SBLip2 and 50 °C for SBLip5.1. The three esterases displayed different levels of tolerance to salts, solvents and detergents, SBLip2 being overall more tolerant to high concentrations of solvent and SBLip5.1 less affected by detergents. PMID:23160923

Biver, Sophie; Vandenbol, Micheline

2013-02-01

276

Functional Groups Based on Leaf Physiology: Are they Spatially and Temporally Robust.  

National Technical Information Service (NTIS)

The functional grouping hypothesis, which suggests that complexity in function can be simplified by grouping species with similar responses, was tested in the Florida scrub habitat. Functional groups were identified based on how species in fire maintained...

T. E. Foster J. R. Brooks

2002-01-01

277

Symmetry groups, density-matrix equations and covariant Wigner functions  

NASA Astrophysics Data System (ADS)

A representation theory for Lie groups is developed taking the Hilbert space, say Hw, of the w?-algebra standard representation as the representation space. In this context the states describing physical systems are amplitude wave functions but closely connected with the notion of the density matrix. Then, based on symmetry properties, a general physical interpretation for the dual variables of thermal theories, in particular the thermofield dynamics (TFD) formalism, is introduced. The kinematic symmetries, Galilei and Poincaré, are studied and (density) amplitude matrix equations are derived for both of these cases. In the same context of group theory, the notion of phase space in quantum theory is analysed. Thus, in the non-relativistic situation, the concept of density amplitude is introduced, and as an example, a spin-half system is algebraically studied; Wigner function representations for the amplitude density matrices are derived and the connection of TFD and the usual Wigner-function methods are analysed. For the Poincaré symmetries the relativistic density matrix equations are studied for the scalar and spinorial fields. The relativistic phase space is built following the lines of the non-relativistic case. So, for the scalar field, the kinetic theory is introduced via the Klein-Gordon density-matrix equation, and a derivation of the Jüttiner distribution is presented as an example, thus making it possible to compare with the standard approaches. The analysis of the phase space for the Dirac field is carried out in connection with the dual spinor structure induced by the Dirac-field density-matrix equation, with the physical content relying on the symmetry groups. Gauge invariance is considered and, as a basic result, it is shown that the Heinz density operator (which has been used to develope a gauge covariant kinetic theory) is a particular solution for the (Klein-Gordon and Dirac) density-matrix equation.

Santana, A. E.; Neto, A. Matos; Vianna, J. D. M.; Khanna, F. C.

2000-06-01

278

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

279

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

280

MICROBIAL TRANSFORMATION OF ESTERS OF CHLORINATED CARBOXYLIC ACIDS  

EPA Science Inventory

Two groups of compounds were selected for microbial transformation studies. In the first group were carboxylic acid esters having a fixed aromatic moiety and an increasing length of the alkyl component. Ethyl esters of chlorine-substituted carboxylic acids were in the second grou...

281

ESG: extended similarity group method for automated protein function prediction  

PubMed Central

Motivation: Importance of accurate automatic protein function prediction is ever increasing in the face of a large number of newly sequenced genomes and proteomics data that are awaiting biological interpretation. Conventional methods have focused on high sequence similarity-based annotation transfer which relies on the concept of homology. However, many cases have been reported that simple transfer of function from top hits of a homology search causes erroneous annotation. New methods are required to handle the sequence similarity in a more robust way to combine together signals from strongly and weakly similar proteins for effectively predicting function for unknown proteins with high reliability. Results: We present the extended similarity group (ESG) method, which performs iterative sequence database searches and annotates a query sequence with Gene Ontology terms. Each annotation is assigned with probability based on its relative similarity score with the multiple-level neighbors in the protein similarity graph. We will depict how the statistical framework of ESG improves the prediction accuracy by iteratively taking into account the neighborhood of query protein in the sequence similarity space. ESG outperforms conventional PSI-BLAST and the protein function prediction (PFP) algorithm. It is found that the iterative search is effective in capturing multiple-domains in a query protein, enabling accurately predicting several functions which originate from different domains. Availability: ESG web server is available for automated protein function prediction at http://dragon.bio.purdue.edu/ESG/ Contact: cspark@cau.ac.kr; dkihara@purdue.edu Supplementary information: Supplementary data are available at Bioinformatics online.

Chitale, Meghana; Hawkins, Troy; Park, Changsoon; Kihara, Daisuke

2009-01-01

282

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

2013-01-18

283

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

284

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

2013-01-01

285

Synthesis of branched cyclomaltooligosaccharide carboxylic acids (cyclodextrin carboxylic acids) by microbial oxidation.  

PubMed

Novel branched cyclomaltooligosaccharide carboxylic acid (cyclodextrin carboxylic acid) derivatives were synthesized by microbial oxidation using Pseudogluconobacter saccharoketogenes to oxidize five types of branched cyclodextrins, including maltosyl beta-cyclodextrin (maltosyl-beta-CyD). For each novel cyclodextrin carboxylic acid derivative synthesized, the hydroxymethyl group of the terminal glucose residue in the branched part of the molecule was regiospecifically oxidized to a carboxyl group to give the corresponding uronic acid. In addition, the physicochemical properties of cyclomaltoheptaosyl-(6-->1)-alpha-D-glucopyranosyl-(4-->1)-alpha-D-glucopyranosiduronic acid (GUG-beta-CyD) (1) and its sodium salt were studied more extensively, as these compounds are most likely to have a practical application. PMID:11398984

Ishiguro, T; Fuse, T; Oka, M; Kurasawa, T; Nakamichi, M; Yasumura, Y; Tsuda, M; Yamaguchi, T; Nogami, I

2001-04-23

286

Surface Functionalization of Magnetic Iron Oxide Nanoparticles for MRI Applications - Effect of Anchoring Group and Ligand Exchange Protocol  

PubMed Central

Hydrophobic magnetite nanoparticles synthesized from thermal decomposition of iron salts must be rendered hydrophilic for their application as MRI contrast agents. This process requires refunctionalizing the surface of the nanoparticles with a hydrophilic organic coating such as polyethylene glycol. Two parameters were found to influence the magnetic behavior and relaxivity of the resulting hydrophilic iron oxide nanoparticles: the functionality of the anchoring group and the protocol followed for the functionalization. Nanoparticles coated with PEGs via a catecholate-type anchoring moiety maintain the saturation magnetization and relaxivity of the hydrophobic magnetite precursor. Other anchoring functionalities, such as phosphonate, carboxylate, and dopamine decrease the magnetization and relaxivity of the contrast agent. The protocol for functionalizing the nanoparticles also influences the magnetic behavior of the material. Nanoparticles refunctionalized according to a direct biphasic protocol exhibit higher relaxivity than those refunctionalized according to a two-step procedure which first involves stripping the nanoparticles. This research presents the first systematic study of both the binding moiety and the functionalization protocol on the relaxivity and magnetization of water-soluble coated iron oxide nanoparticles used as MRI contrast agents.

Smolensky, Eric D.; Park, Hee-Yun E.; Berquo, Thelma S.; Pierre, Valerie C.

2011-01-01

287

Phospholipid functional groups involved in protein kinase C activation, phorbol ester binding, and binding to mixed micelles.  

PubMed

The specificity of the phospholipid cofactor requirement of rat brain protein kinase C was investigated using Triton X-100 mixed micellar methods. Sixteen analogues of phosphatidylserine were prepared and tested for their ability to support protein kinase C activity, [3H]phorbol 12,13-dibutyrate binding, and protein kinase C binding to mixed micelles. Phosphatidylserinol, -L-serine methyl ester, -N-acetyl-L-serine, -2-hydroxyacetate, -3-hydroxypropionate, and -4-hydroxybutyrate did not activate protein kinase C in mixed micelles containing 2 mol % of sn-1,2-dioleoylglycerol. This indicates that both the carboxyl and amino moieties are important for activation. Phosphatidyl-D-serine and -L-homoserine were incapable of supporting full activation; this demonstrates stereospecificity and the importance of the distance between the phosphate and carboxyl and amino moieties. Since 1,2-rac-phosphatidyl-L-serine and 1,3-phosphatidyl-L-serine fully supported protein kinase C activity, the stereochemistry within the glycerol backbone at the interface was not necessary for maximal activation. Neither lysophosphatidyl-L-serine nor 1-oleoyl-2-acetyl-sn-glycero-3-phospho-L-serine supported protein kinase C activity implying that the interfacial conformation is critical to the activation process. The phospholipid dependencies of [3H]phorbol 12,13-dibutyrate binding and of protein kinase C binding to mixed micelles containing sn-1,2-dioleoylglycerol did not mirror those for activation. The data demonstrate that protein kinase C possesses a high degree of specificity with respect to phospholipid activation and implicate several functional groups within the phospho-L-serine polar head group in binding and activation. PMID:2768240

Lee, M H; Bell, R M

1989-09-01

288

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

289

Understanding biocatalyst inhibition by carboxylic acids  

PubMed Central

Carboxylic acids are an attractive biorenewable chemical in terms of their flexibility and usage as precursors for a variety of industrial chemicals. It has been demonstrated that such carboxylic acids can be fermentatively produced using engineered microbes, such as Escherichia coli and Saccharomyces cerevisiae. However, like many other attractive biorenewable fuels and chemicals, carboxylic acids become inhibitory to these microbes at concentrations below the desired yield and titer. In fact, their potency as microbial inhibitors is highlighted by the fact that many of these carboxylic acids are routinely used as food preservatives. This review highlights the current knowledge regarding the impact that saturated, straight-chain carboxylic acids, such as hexanoic, octanoic, decanoic, and lauric acids can have on E. coli and S. cerevisiae, with the goal of identifying metabolic engineering strategies to increase robustness. Key effects of these carboxylic acids include damage to the cell membrane and a decrease of the microbial internal pH. Certain changes in cell membrane properties, such as composition, fluidity, integrity, and hydrophobicity, and intracellular pH are often associated with increased tolerance. The availability of appropriate exporters, such as Pdr12, can also increase tolerance. The effect on metabolic processes, such as maintaining appropriate respiratory function, regulation of Lrp activity and inhibition of production of key metabolites such as methionine, are also considered. Understanding the mechanisms of biocatalyst inhibition by these desirable products can aid in the engineering of robust strains with improved industrial performance.

Jarboe, Laura R.; Royce, Liam A.; Liu, Ping

2013-01-01

290

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

291

Functional renormalization group approach for inhomogeneous interacting Fermi systems  

NASA Astrophysics Data System (ADS)

The functional renormalization group (fRG) approach has the property that, in general, the flow equation for the two-particle vertex generates O (N4) independent variables, where N is the number of interacting states (e.g., sites of a real-space discretization). In order to include the flow equation for the two-particle vertex, one needs to make further approximations if N becomes too large. We present such an approximation scheme, called the coupled-ladder approximation, for the special case of an onsite interaction. Like the generic third-order-truncated fRG, the coupled-ladder approximation is exact to second order and is closely related to a simultaneous treatment of the random phase approximation in all channels, i.e., summing up parquet-type diagrams. The scheme is applied to a one-dimensional model describing a quantum point contact.

Bauer, Florian; Heyder, Jan; von Delft, Jan

2014-01-01

292

Renormalization group irreversible functions in more than two dimensions  

NASA Astrophysics Data System (ADS)

There are two general irreversibility theorems for the renormalization group in more than two dimensions: the first one is of entropic nature, while the second one, by Forte and Latorre, relies on the properties of the stress-tensor trace, and has been recently questioned by Osborn and Shore. We start by establishing under what assumptions this second theorem can still be valid. Then it is compared with the entropic theorem and shown to be essentially equivalent. However, since the irreversible function of the (corrected) Forte-Latorre theorem is nonuniversal (whereas the relative entropy of the other theorem is universal), it needs the additional step of renormalization. On the other hand, the irreversibility theorem is only guaranteed to be unambiguous if the integral of the stress-tensor trace correlator is finite, which happens for free theories only in dimensions smaller than four.

Gaite, José

2000-12-01

293

Polycomb Group Proteins Are Key Regulators of Keratinocyte Function  

PubMed Central

The Polycomb group (PcG) proteins are epigenetic suppressors of gene expression that function through modification of histones to change chromatin structure and modulate gene expression and cell behavior. Recent studies show that PcG proteins are expressed in epidermis, that their levels change during differentiation and in disease states, and that PcG expression is regulated by agents that influence cell proliferation and survival. The results indicate that PcG proteins regulate keratinocyte cell-cycle progression, apoptosis, senescence, and differentiation. These proteins are expressed in progenitor cells, in the basal layer, and in suprabasal keratinocytes, and the level, timing, and distribution of expression suggest that the PcG proteins have a central role in maintaining the balance between cell survival and death in multiple epidermal compartments. Additional studies indicate an important role in skin cancer progression.

Eckert, Richard L.; Adhikary, Gautam; Rorke, Ellen A.; Ching Chew, Yap; Balasubramanian, Sivaprakasam

2011-01-01

294

A DFT-based model for calculating solvolytic reactivity. The nucleofugality of aliphatic carboxylates in terms of Nf parameters.  

PubMed

The most comprehensive nucleofugality scale, based on the correlation and solvolytic rate constants of benzhydrylium derivatives, has recently been proposed by Mayr and co-workers (Acc. Chem. Res., 2010, 43, 1537-1549). In this work, the possibility of employing quantum chemical calculations in further determination of nucleofugality (Nf) parameters of leaving groups is explored. Whereas the heterolytic transition state of benzhydryl carboxylate cannot be optimized by quantum chemical calculations, the possibility of an alternative model reaction is examined in order to obtain nucleofugality parameters of various aliphatic carboxylates, which can properly be included in the current nucleofugality scale. For that purpose, ground and transition state structures have been optimized for the proposed model reaction, which includes anchimerically assisted heterolytic dissociation of cis-2,3-dihydroxycyclopropyl trans-carboxylates. The validity of the model reaction as well as of applied DFT methods in the presence of the IEFPCM solvation model is verified by correlating calculated free energies of activation of the model reaction with literature experimental data for solvolysis of reference dianisylmethyl carboxylates. For this purpose the ability of several functionals (including popular B3LYP) is examined, among which the M06-2X gives the best results. The very good correlation indicates acceptable accurate relative reactivities of aliphatic carboxylates, and enables the estimation of rate constants for solvolysis of other dianisylmethyl carboxylates in aqueous ethanol mixtures, from which the corresponding Nf parameters are determined using mentioned Mayr's equation. In addition, DFT calculations confirm the previous experimental observation that the abilities of aliphatic carboxylate leaving groups in solution are governed by the inductive effect of substituents attached to the carboxyl group. PMID:24964919

Denegri, Bernard; Mati?, Mirela; Kronja, Olga

2014-08-14

295

Fermionic functional renormalization group approach to superfluid phase transition  

NASA Astrophysics Data System (ADS)

A fermionic functional renormalization group (FRG) is applied to describe the superfluid phase transition of the two-component fermionic system with attractive contact interaction. The connection between the fermionic FRG approach and the conventional Bardeen-Cooper-Schrieffer (BCS) theory with Gorkov and Melik-Barkhudarov (GMB) correction are clarified in detail in the weak coupling region by using the renormalization group flow of the fermionic four-point vertex with particle-particle and particle-hole scattering contributions. To go beyond the BCS+GMB theory, coupled FRG flow equations of the fermion self-energy and the four-point vertex are studied under an Ansatz concerning their frequency/momentum dependence. We found that the fermion self-energy turns out to be substantial even in the weak coupling region, and the frequency dependence of the four-point vertex is essential to obtain the correct asymptotic-ultraviolet behavior of the flow for the self-energy. The superfluid transition temperature and the associated chemical potential are calculated in the region of negative scattering lengths.

Tanizaki, Yuya; Fej?s, Gergely; Hatsuda, Tetsuo

2014-04-01

296

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

297

Changes in Bird Functional Diversity across Multiple Land Uses: Interpretations of Functional Redundancy Depend on Functional Group Identity  

PubMed Central

Examinations of the impact of land-use change on functional diversity link changes in ecological community structure driven by land modification with the consequences for ecosystem function. Yet, most studies have been small-scale, experimental analyses and primarily focussed on plants. There is a lack of research on fauna communities and at large-scales across multiple land uses. We assessed changes in the functional diversity of bird communities across 24 land uses aligned along an intensification gradient. We tested the hypothesis that functional diversity is higher in less intensively used landscapes, documented changes in diversity using four diversity metrics, and examined how functional diversity varied with species richness to identify levels of functional redundancy. Functional diversity, measured using a dendogram-based metric, increased from high to low intensity land uses, but observed values did not differ significantly from randomly-generated expected values. Values for functional evenness and functional divergence did not vary consistently with land-use intensification, although higher than expected values were mostly recorded in high intensity land uses. A total of 16 land uses had lower than expected values for functional dispersion and these were mostly low intensity native vegetation sites. Relations between functional diversity and bird species richness yielded strikingly different patterns for the entire bird community vs. particular functional groups. For all birds and insectivores, functional evenness, divergence and dispersion showed a linear decline with increasing species richness suggesting substantial functional redundancy across communities. However, for nectarivores, frugivores and carnivores, there was a significant hump-shaped or non-significant positive linear relationship between these functional measures and species richness indicating less redundancy. Hump-shaped relationships signify that the most functionally diverse communities occur at intermediate levels of species richness. Interpretations of redundancy thus vary for different functional groups and related ecosystem functions (e.g. pollination), and can be substantially different to relationships involving entire ecological communities.

Luck, Gary W.; Carter, Andrew; Smallbone, Lisa

2013-01-01

298

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

2011-09-14

299

Effects of macrophyte functional group richness on emergent freshwater wetland functions.  

PubMed

Most plant diversity-function studies have been conducted in terrestrial ecosystems and have focused on plant productivity and nutrient uptake/retention, with a notable lack of attention paid to belowground processes (e.g., root dynamics, decomposition, trace gas fluxes). Here we present results from a mesocosm experiment in which we assessed how the richness of emergent macrophyte functional groups influences aboveground and belowground plant growth and microbial-mediated functions related to carbon and nitrogen cycling, with an emphasis on methane (CH4) efflux and potential denitrification rates. We found that an increase in the richness of wetland plant functional groups enhanced belowground plant biomass, altered rooting patterns, and decreased methane efflux, while having no effect on aboveground plant production or denitrification potential. We hypothesize that the greater root production and increased rooting depth in the highest diversity treatments enhanced CH4 oxidation to a relatively greater degree than methane production, leading to an overall decrease in CH4 efflux across our plant functional group richness gradient. PMID:18051659

Bouchard, Virginie; Frey, Serita D; Gilbert, Janice M; Reed, Sharon E

2007-11-01

300

Functional movement screen scores in a group of running athletes.  

PubMed

The purpose of this study was to determine the mean values of the functional movement screen (FMS) in a group of long-distance runners. The secondary aims were to investigate whether the FMS performance differed between sexes and between young and older runners. Forty-three runners, 16 women (mean age = 33.5 years, height = 165.2 cm, weight = 56.3 kg, and body mass index [BMI] = 20.6) and 27 men (mean age = 39.3 years, height = 177.6 cm, weight = 75.8 kg, and BMI = 24.2) performed the FMS. All the runners were injury-free and ran >30 km·wk. Independent t-tests were performed on the composite scores to examine the differences between men and women and also between young (<40 years) and older runners (>40 years). Contingency tables (2 × 2) were developed for each of the 7 screening tests to further look at the differences in groups for each single test. The ? values were calculated to determine significant differences. Statistical significance was set at p ? 0.05. There was no significant difference in the composite score between women and men. There were significant differences between the sexes in the push-up and straight leg test scores, with the women scoring better on each test. A significant difference was found in the composite scores between younger and older runners (p < 0.000). Additional score differences were found for the squat, hurdle step, and in-line lunge tests with the younger runners scoring better. This study provided mean values for the FMS in a cohort of long-distance runners. These values can be used as a reference for comparing FMST scores in other runners who are screened with this tool. PMID:24662154

Loudon, Janice K; Parkerson-Mitchell, Amy J; Hildebrand, Laurie D; Teague, Connie

2014-04-01

301

Effect of functional groups on antioxidant properties of substituted selenoethers.  

PubMed

Selenoethers attached to functional groups through propyl chain viz., bis(3-carboxypropyl)selenide (SeBA), bis(3-hydroxypropyl)selenide (SePOH) and bis(3-aminopropyl)selenide dihydrochloride (SePAm), have been examined for their ability to inhibit peroxyl radical mediated DNA damage, peroxyl radical scavenging ability and glutathione peroxidase (GPx) like activity. The DNA damage was monitored by gel electrophoresis, bimolecular rate constants for scavenging of model peroxyl radical were determined by pulse radiolysis and the GPx activity was followed by their ability to reduce hydrogen peroxide in the presence of glutathione utilizing NADPH decay and HPLC analysis. Among these compounds, SeBA showed maximum DNA protecting activity and it was also the most efficient in scavenging peroxyl radicals with the highest GPx mimicking activity. Quantum chemical calculations confirmed that SeBA with the highest energy level of HOMO (highest occupied molecular orbital) is the easiest to undergo oxidation and therefore exhibits better radical scavenging, GPx mimicking and DNA protecting activity than SePOH or SePAm. PMID:21235282

Prabhu, P; Bag, P P; Singh, B G; Hodage, A; Jain, V K; Iwaoka, M; Priyadarsini, K I

2011-04-01

302

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

303

The Human Immunodeficiency Virus Tat Proteins Specifically Associate with TAK In Vivo and Require the Carboxyl Terminal Domain of RNA Polymerase II for Function  

Microsoft Academic Search

Humanimmunodeficiencyvirustypes1and2encodecloselyrelatedproteins,Tat-1andTat-2,thatstimulate viral transcription. Previously, we showed that the activation domains of these proteins specifically interact in vitro with a cellular protein kinase named TAK. In vitro, TAK phosphorylates the Tat-2 but not the Tat-1 protein, a 42-kDa polypeptide of unknown identity, and the carboxyl-terminal domain (CTD) of RNA poly- merase II (RNAP II). We now show that the 42-kDa substrate

XINZHEN YANG; CHRISTINE H. HERRMANN; ANDANDREW P. RICE

1996-01-01

304

Modification of polylactide surfaces with lactide-ethylene oxide functional block copolymers: accessibility of functional groups.  

PubMed

Feasibility of using amphiphilic block copolymers composed of polylactide (PLA) and poly(ethylene oxide) (PEO) blocks for biomimetic surface modification of polylactide-based biomaterials for tissue engineering was investigated. PEO-b-PLA copolymers were deposited on the PLA surface from a solution in PEO-selective solvent. Copolymers with a neutral omega-methoxy end group of the PEO block (mPEO-b-PLA) were used to provide hydrophilic surface of PLLA, which exhibited suppressed nonspecific protein adsorption. Their analogues, containing biotin group at the end of PEO block (bPEO-b-PLA), were used as a model of functional copolymers, carrying a biomimetic group, for example, a cell-adhesion fibronectine-derived peptide sequence. The surface topography of functional groups on the modified surface and their accessibility for interaction with a protein receptor was investigated, taking advantage of specific biotin-avidin interaction, on surfaces modified with a combination of mPEO-b-PLA and bPEO-b-PLA copolymers. The accessibility of model biotin groups for interaction with their protein counterpart was proven through visualization of avidin or avidin-labeled nanospheres with atomic force microscopy. PMID:19954220

Tresohlavá, Eliska; Popelka, Stepán; Machová, Ludka; Rypácek, Frantisek

2010-01-11

305

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

306

Nutrient resorption patterns of plant functional groups in a tropical savanna: variation and functional significance  

Microsoft Academic Search

Green and senesced leaf nitrogen (N) and phosphorus (P) concentrations of different plant functional groups in savanna communities\\u000a of Kruger National Park, South Africa were analyzed to determine if nutrient resorption was regulated by plant nutritional\\u000a status and foliar N:P ratios. The N and P concentrations in green leaves and the N concentrations in senesced leaves differed\\u000a significantly between the

Jayashree Ratnam; Mahesh Sankaran; Niall P. Hanan; Rina C. Grant; Nick Zambatis

2008-01-01

307

Oxygen activation by nonheme iron(II) complexes: alpha-keto carboxylate versus carboxylate.  

PubMed

Mononuclear iron(II) alpha-keto carboxylate and carboxylate compounds of the sterically hindered tridentate face-capping ligand Tp(Ph2) (Tp(Ph2) = hydrotris(3,5-diphenylpyrazol-1-yl)borate) were prepared as models for the active sites of nonheme iron oxygenases. The structures of an aliphatic alpha-keto carboxylate complex, [Fe(II)(Tp(Ph2))(O(2)CC(O)CH(3))], and the carboxylate complexes [Fe(II)(Tp(Ph2))(OBz)] and [Fe(II)(Tp(Ph2))(OAc)(3,5-Ph(2)pzH)] were determined by single-crystal X-ray diffraction, all of which have five-coordinate iron centers. Both the alpha-keto carboxylate and the carboxylate compounds react with dioxygen resulting in the hydroxylation of a single ortho phenyl position of the Tp(Ph2) ligand. The oxygenation products were characterized spectroscopically, and the structure of the octahedral iron(III) phenolate product [Fe(III)(Tp(Ph2))(OAc)(3,5-Ph(2)pzH)] was established by X-ray diffraction. The reaction of the alpha-keto carboxylate model compounds with oxygen to produce the phenolate product occurs with concomitant oxidative decarboxylation of the alpha-keto acid. Isotope labeling studies show that (18)O(2) ends up in the Tp(Ph2) phenolate oxygen and the carboxylate derived from the alpha-keto acid. The isotope incorporation mirrors the dioxygenase nature of the enzymatic systems. Parallel studies on the carboxylate complexes demonstrate that the oxygen in the hydroxylated ligand is also derived from molecular oxygen. The oxygenation of the benzoylformate complex is demonstrated to be first order in metal complex and dioxygen, with activation parameters DeltaH++ = 25 +/- 2 kJ mol(-1) and DeltaS++ = -179 +/- 6 J mol(-1) K(-1). The rate of appearance of the iron(III) phenolate product is sensitive to the nature of the substituent on the benzoylformate ligand, exhibiting a Hammett rho value of +1.3 indicative of a nucleophilic mechanism. The proposed reaction mechanism involves dioxygen binding to produce an iron(III) superoxide species, nucleophilic attack of the superoxide at the alpha-keto functionality, and oxidative decarboxylation of the adduct to afford the oxidizing species that attacks the Tp(Ph2) phenyl ring. Interestingly, the alpha-keto carboxylate complexes react 2 orders of magnitude faster than the carboxylate complexes, thus emphasizing the key role that the alpha-keto functionality plays in oxygen activation by alpha-keto acid-dependent iron enzymes. PMID:12823001

Mehn, Mark P; Fujisawa, Kiyoshi; Hegg, Eric L; Que, Lawrence

2003-07-01

308

Deliberately designed processes to physically tether the carboxyl groups of poly(pentacosadiynoic acid) to a poly(vinyl alcohol) glassy matrix to make poly(pentacosadiynoic acid) thermochromically reversible in the matrix.  

PubMed

In this article, we demonstrate that by tethering carboxyl groups of poly(10,12-pentacosadiynoic acid) (PDA) to a poly(vinyl alcohol) (PVA) matrix, PDA, which is irreversible in its pure form, becomes reversible in the thermochromism. The tethering is realized by simple but deliberately designed processes: (1) Disperse the commercially available monomer 10,12-pentacosadiynoic acid (DA) nanocrystals in a PVA aqueous solution by the "NCCM" method invented in our laboratory. (2) Anneal and dry the mixture solution at a temperature higher than the melting point of pure DA crystal. (3) Polymerize the as-annealed DA/PVA blend films by UV irradiation. After the polymerization, PDA/PVA films with completely reversible thermochromism are obtained. The reversible PDA/PVA films can be easily dissolved in water, leading to water-dispersible nanoaggregates with the reversibility. Blends of PDA with other water-soluble polymers such as poly(ethylene oxide) (PEO), poly(acrylic acid) (PAA) and poly(allyamine) (PAM), were prepared respectively, by the same processes and under the same conditions. It is found that all these nanocomposites are irreversible or partially reversible in the thermochromism; either the relatively low glassy transition temperature of the polymer matrix (in the case of PEO) or the partial ionization nature of the polymer (in the cases of PAA and PAM) is responsible for the irreversibility or the partial reversibility. PMID:21568353

Guo, Juan; Zhu, Lei; Jiang, Ming; Chen, Daoyong

2011-06-01

309

Controls of functional group chemistry on calcium carbonate nucleation: Insights into systematics of biomolecular innovations for skeletal mineralization?  

NASA Astrophysics Data System (ADS)

Living organisms produce skeletal structures within a complex matrix of organic macromolecules that guide the nucleation and growth of crystalline structures into the organic-inorganic composites we know as biominerals. This type of biomolecule-directed mineralization is an ancient process as evidenced by structures in the fossil record that date to the Ediacaran (ca. 549 Ma). Our understanding of template-directed biomineralization, however, is largely based upon assumptions from studies that: 1) qualitatively demonstrate some chemical functionalities influence the nucleating mineral phase and morphology; 2) propose proteins are the primary driver to template-directed mineralization and 3) propose the ubiquitous polysaccharides are inert components. Thus, a mechanistic basis for how the underlying chemistry of macromolecules controls nucleation kinetics and thermodynamics in template-directed nucleation is not well established. Moreover, there is not yet a good appreciation for how patterns of skeletal mineralization evolved with biochemical innovations in response to environmental changes over geologic timescales. In small steps toward understanding biochemical controls on biomineralization, we test the hypothesis that the kinetics and thermodynamics of calcium carbonate (CaCO3) formation is regulated by a systematic relationship to the functional group chemistry of macromolecules. A long-term goal is to establish the energetic basis for biochemical motifs that are seen (and not seen) at sites of calcification across the phylogenetic tree. Two types of studies were conducted. The first measured nucleation rates on model biomolecular substrates with termini that are found in proteins associated with sites of calcification (-COOH, -PO4, and -SH) and two alkanethiol chain lengths (16-C and 11-C) at a variety of chemical driving forces. The measurements show functional group chemistry and molecule conformation regulate rates by a predictable relation to interfacial free energy. A second study tested the hypothesis that polysaccharides can also confer reactivity through their functional group chemistry. Using high purity polysaccharides with regular monomer sequences as simple model compounds, we quantify the effect of functional group chemistry (chitosan, hyaluronic acid, heparin, alginic acid) and monomer sequencing (two stereoisomers of alginic acid) on the kinetic and thermodynamic barriers to CaCO3 formation. Analysis of the data indicates the barriers to nucleation are correlated by a systematic relationship to charge as the number of carboxyl groups per monomer of polysaccharide. The findings demonstrate a physical basis for how organic surfaces regulate the thermodynamic barrier to nucleation through interfacial free energy and suggest the chemical basis for recurring motifs that are seen in modern organisms. We also show that polysaccharides may indeed have active roles in promoting calcite mineralization and suggest their presumed function as inert framework molecules should be revisited.

Dove, P. M.; Hamm, L. M.; Giuffre, A. J.

2012-12-01

310

Synthesis of Silver Nanoclusters and Functionalization with Glucosamine for Glyconanoparticles  

Microsoft Academic Search

Functionalized nanoparticles are promising candidates for the construction of new nanomaterials. In this paper, glucosamine was covalently functionalized on the surface of silver nanoparticles to fabricate glyconanoparticles. Silver nanoclusters obtained by liquid-solid-solution (LSS) strategy under hydrothermal condition were first functionalized by carboxyl-terminated alkanethiol and the terminal carboxyl group was subsequently bonded with side-chain amino group of glucosamine surface through EDC\\/NHS

Murugan Veerapandian; Kyusik Yun

2010-01-01

311

Perceptual Visual Grouping under Inattention: Electrophysiological Functional Imaging  

ERIC Educational Resources Information Center

Two types of perceptual visual grouping, differing in complexity of shape formation, were examined under inattention. Fourteen participants performed a similarity judgment task concerning two successive briefly presented central targets surrounded by task-irrelevant simple and complex grouping patterns. Event-related potentials (ERPs) were…

Razpurker-Apfeld, Irene; Pratt, Hillel

2008-01-01

312

FUNCTIONALIZED HIGH-DENSITY POLYETHYLENE WITH BLOCKED ISOCYANATE GROUP  

Microsoft Academic Search

Blocked HI (BHI) was synthesized by the reaction of HI (2-hydroxyethyl methacrylate combined with isophorone diisocyanate) with ?-caprolactam (CPL). CPL was used as a blocking agent to improve storage stability of HI. From the Fourier transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (H-NMR) spectra it was found that NH group in CPL reacted with remaining isocyanate (NCO) groups

Dong-Hyun Kim; Kang-Yeol Park; Ju-Young Kim; Kyoung-Do Suh

2000-01-01

313

Chemical modification and pH dependence of kinetic parameters to identify functional groups in a glucosyltransferase from Strep. Mutans  

SciTech Connect

A glucosyltransferase, forming a predominantly al-6 linked glucan, was partially purified from the culture filtrate of S. mutans GS-5. The kinetic properties of the enzyme, assessed using the transfer of /sup 14/C glucose from sucrose into total glucan, were studied at pH values from pH 3.5 to 6.5. From the dependence of km on pH, a group with pKa = 5.5 must be protonated to maximize substrate binding. From plots of V/sub max/ vs pH two groups, with pKa's of 4.5 and 5.5 were indicated. The results suggest the involvement of either two carboxyl groups (one protonated, one unprotonated in the native enzyme) or a carboxyl group (unprotonated) and some other protonated group such as histidine, cysteine. Chemical modification studies showed that Diethylyrocarbonate (histidine specific) had no effect on enzyme activity while modification with p-phydroxy-mercuribenzoate or iodoacetic acid (sulfhydryl reactive) and carbodimide reagents (carboxyl specific) resulted in almost complete inactivation. Activity loss was dependent upon time of incubation and reagent concentration. The disaccharide lylose, (shown to be an inhibitor of the enzyme with similar affinity to sucrose) offers no protection against modification by the sulfhydryl reactive reagents.

Bell, J.E.; Leone, A.; Bell, E.T.

1986-05-01

314

New approaches to the synthesis of selected hydroxyquinolines and their hydroxyquinoline carboxylic acid analogues  

NASA Astrophysics Data System (ADS)

New approaches to the synthesis of selected crystalline hydroxyquinolines and their carboxylic acid analogues were elaborated in this paper with the auxiliary of computational and spectroscopic characterization, such as FTIR, NMR and single crystal X-ray measurements. The experimental data were further rationalized based on a DFT calculation method with B3LYP functional, which reflected the impact of electron donating or withdrawing groups on the energy level of HOMO orbitals and the reactivity of the substituted hydroxyquinolines.

Szala, Marcin; Nycz, Jacek E.; Malecki, Grzegorz J.

2014-08-01

315

The SLC13 gene family of sodium sulphate\\/carboxylate cotransporters  

Microsoft Academic Search

The SLC13 gene family consist of five sequence-related members that have been identified in a variety of animals, plants, yeast and bacteria. Proteins encoded by these genes are divided into two functionally unrelated groups: the Na +-sulphate (NaS) cotransporters and the Na +-carboxylate (NaC) cotransporters. Members of this family include the renal Na +-dependent inorganic sulphate transporter-1 (NaSi-1, SLC13A1), the

Daniel Markovich; Heini Murer

2004-01-01

316

Silver-catalyzed decarboxylative trifluoromethylthiolation of aliphatic carboxylic acids in aqueous emulsion.  

PubMed

A silver-catalyzed decarboxylative trifluoromethylthiolation of secondary and tertiary carboxylic acids under mild conditions tolerates a wide range of functional groups. The reaction was dramatically accelerated by its performance in an aqueous emulsion, which was formed by the addition of sodium dodecyl sulfate to water. It was proposed that the radical, which was generated from the silver-catalyzed decarboxylation in the "oil-in-water" droplets, could easily react with the trifluoromethylthiolating reagent to form the product. PMID:24764209

Hu, Feng; Shao, Xinxin; Zhu, Dianhu; Lu, Long; Shen, Qilong

2014-06-10

317

Preparation of pentafluorosulfanyl (SF5) pyrrole carboxylic acid esters.  

PubMed

Pyrrole derivatives bearing a pentafluorosulfanyl group are currently unknown. In this paper, a facile preparation of SF5-substituted pyrrole carboxylic acid esters in good yield is reported. Utilizing the cycloaddition of an azomethine ylide to pentafluorosulfanylalkynes, a series of dihydropyrroles were prepared and oxidized to the respective 1-tert-butyl-4-(pentafluorosulfanyl)pyrrole-2-carboxylic acid esters in good yield. Further treatment of these pyrroles with catalytic triflic acid allowed removal of the tert-butyl group. PMID:19555094

Dolbier, William R; Zheng, Zhaoyun

2009-08-01

318

Influence of functional groups in solid carbon materials on decomposition of hydrogen peroxide  

SciTech Connect

The catalytic activity of solid carbon materials (diamond, graphite, and carbon black) in the decomposition of hydrogen peroxide in aqueous solution is determined by the chemical composition of the functional groups, increasing in the sequence: oxide-hydride-chloride functional groups. The weaker influence of the chemical structure of functional groups on the overall catalytic activity of graphite samples is due to the considerable contribution of the basal area of graphite, inert in formation of functional groups, to the total sample area. The higher activity of chloride functional groups on graphite than on diamond is presumably due to the higher electrical conductivity of graphite.

Olenchuk, L.A.; Gordeev, S.K.; Smirnov, E.P.

1987-10-20

319

The non-competitive antagonists 2-methyl-6-(phenylethynyl)pyridine and 7-hydroxyiminocyclopropan[b]chromen-1a-carboxylic acid ethyl ester interact with overlapping binding pockets in the transmembrane region of group I metabotropic glutamate receptors.  

PubMed

We have investigated the mechanism of inhibition and site of action of the novel human metabotropic glutamate receptor 5 (hmGluR5) antagonist 2-methyl-6-(phenylethynyl)pyridine (MPEP), which is structurally unrelated to classical metabotropic glutamate receptor (mGluR) ligands. Schild analysis indicated that MPEP acts in a non-competitive manner. MPEP also inhibited to a large extent constitutive receptor activity in cells transiently overexpressing rat mGluR5, suggesting that MPEP acts as an inverse agonist. To investigate the molecular determinants that govern selective ligand binding, a mutagenesis study was performed using chimeras and single amino acid substitutions of hmGluR1 and hmGluR5. The mutants were tested for binding of the novel mGluR5 radioligand [(3)H]2-methyl-6-(3-methoxyphenyl)ethynyl pyridine (M-MPEP), a close analog of MPEP. Replacement of Ala-810 in transmembrane (TM) VII or Pro-655 and Ser-658 in TMIII with the homologous residues of hmGluR1 abolished radioligand binding. In contrast, the reciprocal hmGluR1 mutant bearing these three residues of hmGluR5 showed high affinity for [(3)H]M-MPEP. Radioligand binding to these mutants was also inhibited by 7-hydroxyiminocyclopropan[b]chromen-1a-carboxylic acid ethyl ester (CPCCOEt), a structurally unrelated non-competitive mGluR1 antagonist previously shown to interact with residues Thr-815 and Ala-818 in TMVII of hmGluR1. These results indicate that MPEP and CPCCOEt bind to overlapping binding pockets in the TM region of group I mGluRs but interact with different non-conserved residues. PMID:10934211

Pagano, A; Ruegg, D; Litschig, S; Stoehr, N; Stierlin, C; Heinrich, M; Floersheim, P; Prezèau, L; Carroll, F; Pin, J P; Cambria, A; Vranesic, I; Flor, P J; Gasparini, F; Kuhn, R

2000-10-27

320

Detection of functional groups and antibodies on microfabricated surfaces by confocal microscopy  

SciTech Connect

Fluorescence confocal microscopy was used to characterize micron-sized microfabricated silicon particles and planar oxides surfaces after silanization and immobilization of IgG antibody. Surfaces treated with amino- and mercaptosilanes were tested by the presence of amine and sulfhydryl groups by labeling with specific fluorescein probes. In addition, human antibody (IgG) was immobilized to the thiol-coated microparticles using the heterobifunctional crosslinker succinimidyl 4-(N-maleimidolmthyl)-cyclohexane-1-carboxylate. Estimates of the surface density of IgG were consistent with 8.3% of a monolayer of covalently-bound antibody. Confocal images confirmed uniform layers of both silanes and antibodies on the microparticles. The sensitivity limit for the confocal measurements was determined to be as low as 1.5 x 10{sup {minus}5} fluors per nm{sup 2}.

Nashat, A.H.; Ferrari, M. [Univ. of California, Berkeley, CA (United States)] [Univ. of California, Berkeley, CA (United States); Moronne, M. [Lawrence Berkeley National Lab., CA (United States)] [Lawrence Berkeley National Lab., CA (United States)

1998-10-20

321

Surface heterogeneity of polysiloxane xerogels functionalized by 3-aminopropyl groups  

Microsoft Academic Search

DRIFT spectra of xerogels synthesized by co-condensation of tetraethoxysilane (or 1,2-bis(triethoxysilyl)ethane) and 3-aminopropyltriethoxysilane have been measured using termoevacuation in the temperature range 50–350°C. The disappearance of bands related to the vibrations of water molecule with temperature growth and shifts of absorption band related to the deformation vibrations of amino groups to the high-frequency region have been observed. The formation of

Yu. L. Zub; N. V. Stolyarchuk; M. Barczak; A. Dabrowski

2010-01-01

322

Discriminant Function Analysis of Inventoried Interests Among Selected Engineering Groups.  

ERIC Educational Resources Information Center

The utility of multiple discriminant function analysis (MDFA) to differentiate among the interest patterns of engineers was examined. Subjects were 229 engineers who were administered the Strong Vocational Interest Blank (SVIB) in 1935 as college freshmen (1935 FR) and again in 1966, and 210 freshmen who completed the SVIB in 1966 and had…

Clemens, Bryan; Linden, James

323

Group Functions and Multi-Valued Cellular Cascades.  

National Technical Information Service (NTIS)

A multi-valued cellular cascade is a one-dimensional array of multi-valued two-input one-output combinational switching cells. The paper derives necessary and sufficient conditions for the realizability of multi-valued combinational switching functions by...

I. Shinahr M. Yoeli

1968-01-01

324

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

325

Mixture of a molybdenum carboxylate and a molybdenum dithiophosphate or a molybdenum dithiocarbamate for use in a hydrovisbreaking process  

SciTech Connect

A molybdenum is described containing mixture selected from the group consisting of a mixture comprising a molybdenum dithiophosphate and a molybdenum carboxylate and a mixture comprising a molybdenum dithiocarbamate and a molybdenum carboxylate.

Howell, J.A.; Kukes, S.G.

1987-11-10

326

Noncommutative symmetric functions IV: Quantum linear groups and Hecke algebras at q =0  

Microsoft Academic Search

We present representation theoretical interpretations of quasi-symmetric functions and noncommutative symmetric functions in terms of quantum linear groups and Hecke algebras at q = 0. We obtain in this way a noncommutative realization of quasi-symmetric functions analogous to the plactic symmetric functions of Lascoux and Schutzenberger. The generic case leads to a notion of quantum Schur function.

Daniel Krob; Jean-Yves Thibon

1997-01-01

327

Quantifying additive interactions of the osmolyte proline with individual functional groups of proteins: comparisons with urea and glycine betaine, interpretation of m-values.  

PubMed

To quantify interactions of the osmolyte l-proline with protein functional groups and predict their effects on protein processes, we use vapor pressure osmometry to determine chemical potential derivatives d?2/dm3 = ?23, quantifying the preferential interactions of proline (component 3) with 21 solutes (component 2) selected to display different combinations of aliphatic or aromatic C, amide, carboxylate, phosphate or hydroxyl O, and amide or cationic N surface. Solubility data yield ?23 values for four less-soluble solutes. Values of ?23 are dissected using an ASA-based analysis to test the hypothesis of additivity and obtain ?-values (proline interaction potentials) for these eight surface types and three inorganic ions. Values of ?23 predicted from these ?-values agree with the experiment, demonstrating additivity. Molecular interpretation of ?-values using the solute partitioning model yields partition coefficients (Kp) quantifying the local accumulation or exclusion of proline in the hydration water of each functional group. Interactions of proline with native protein surfaces and effects of proline on protein unfolding are predicted from ?-values and ASA information and compared with experimental data, with results for glycine betaine and urea, and with predictions from transfer free energy analysis. We conclude that proline stabilizes proteins because of its unfavorable interactions with (exclusion from) amide oxygens and aliphatic hydrocarbon surfaces exposed in unfolding and that proline is an effective in vivo osmolyte because of the osmolality increase resulting from its unfavorable interactions with anionic (carboxylate and phosphate) and amide oxygens and aliphatic hydrocarbon groups on the surface of cytoplasmic proteins and nucleic acids. PMID:23909383

Diehl, Roger C; Guinn, Emily J; Capp, Michael W; Tsodikov, Oleg V; Record, M Thomas

2013-09-01

328

Study of substituent effects on rotational isomers and monomer–dimer equilibria of the 3-carboxy group in 4-substituted ( R)-2-(3,4-methylenedioxyphenyl)-6-isopropyloxy-2 H-chromen-3-carboxylic acids in dilute CCl 4 and CHCl 3 solutions by FTIR spectroscopy  

Microsoft Academic Search

FTIR spectra of the title carboxylic acids (I–III) with 4-substituents (H, CH3 or C6H5) and their related compounds IV–VI with 4-(substituted phenyl) groups were measured in dilute CCl4 and CHCl3 solutions. The concentration dependence of FTIR spectra of I–IV was also measured in these solutions. These spectra were subjected to curve analysis in order to quantitatively identify the rotational isomers

Mamoru Takasuka; Kenichi Matsumura; Natsuki Ishizuka

2001-01-01

329

Carboxylated poly(glycerol methacrylate)s for doxorubicin delivery.  

PubMed

Poly(glycerol methacrylate)s (PGOHMAs) were successfully synthesized via the hydrolysis of the epoxy groups on linear and/or star-shaped poly(glycidyl methacrylate)s (PGMAs). Further modification of the hydroxyl groups on PGOHMAs with succinic anhydride (SA) or 1,2-cyclohexanedicarboxylic anhydride (CDA) resulted in a new type of polyacid polymer, namely, PGOHMACOOH for short, which was then employed to prepare pH-sensitive assemblies using dialysis method. The carboxylated polymers were quite effective in the encapsulation of doxorubicin hydrochloride (DOX) by electrostatic interaction. Compared with poly(acrylic acid) (PAA), the star-shaped PGOHMA modified with CDA exhibited higher encapsulation efficiency and loading capacity, as well as better pH-responsive release profile. Scanning electron microscope images showed that the polymeric nanoparticles before and after encapsulation of DOX were spherical in shape. The encapsulation efficiency, loading capacity and release properties of these polymers were found to rely on their backbone architectures and the type of carboxylated functionalities. By fine-tuning these factors to achieve optimal properties, such type of polymeric materials holds promise as an attractive and effective drug delivery vehicle. PMID:22085680

Ma, Yanan; Gao, Hui; Gu, Wenxing; Yang, Ying-Wei; Wang, Yinong; Fan, Yunge; Wu, Guolin; Ma, Jianbiao

2012-01-23

330

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

331

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

332

Application of the functionally generated path technique to restore mandibular molars in bilateral group function occlusion.  

PubMed

The functionally generated path (FGP) is a static representation of the opposing cusps' dynamic eccentric movements from a centric position to achieve optimal articulation and occlusal harmony. When understood and appreciated, use of the FGP technique is a straightforward and practical method to achieve harmonious occlusal anatomy of restorations with the anterior determinant/anterior guidance, the posterior determinant/condylar guidance, existing occlusal and cuspal anatomy, and the neuromuscular system. Although the FGP technique is normally used in the fabrication of maxillary posterior indirect restorations, it is described and applied here in the fabrication of mandibular posterior restorations that maintained the patient's bilateral group function occlusion while eliminating the nonworking side and protrusive interferences. This novel procedure involved the use of a stone crib to intraorally construct a stone core that captured the FGP recording while simultaneously indexing to the contralateral and ipsilateral mandibular dentition. This technique lends additional stability to the stone core to minimize error during the mounting process. PMID:23106795

DuVall, Nicholas B; Rogers, Paul M

2013-04-01

333

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

334

Substituent Effects. Vi. Theoretical Interpretation of Additivity Rules of NMR Using Mcwenny Group Functions.  

National Technical Information Service (NTIS)

McWeeny group functions, in conjunction with the popular Ramsey formulation, are used to theoretically account for the additive influence of substituents observed in NMR spectra. In this treatment the group wavefunctions are assumed to perturb one another...

T. Vladimiroff E. R. Malinowski

1966-01-01

335

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

336

Infrared-chemical derivatization method for determination of total hydroxyls and carboxyls in petroleum and syncrudes  

SciTech Connect

Oxygen-containing functional group (hydroxyl and carboxyl) in fuels or crude oils, or fractions thereof, are determined by RI spectroscopy. The approach is based on chemical derivatization followed by measurement of RI bands of the corresponding derivatives. The chemical derivatization procedure involves two steps: (1) esterification of carboxylic acids with 2,2,2-trifluoroethanol and (2) acylation of alcoholic and phenolic hydroxyls with trifluoroacetyl chloride. The aryl trifluoroacetates absorb at 1800 cm/sup /minus/1/; the 2,2,2-trifluoroethyl esters absorb in the region 1760-1740 cm/sup /minus/1/. Variation of molar absorptivity of the derivatives as a function of structure is determined using pure compounds and well defined fractions from actual fuel samples. The overall accuracy, precision, sensitivity, and range of applicability to petroleum and related sample types are discussed. 52 refs., 3 figs., 9 tabs.

Yu, S.K-T; Green, J.B.

1988-09-01

337

Structural characterization and function determination of a nonspecific carboxylate esterase from the amidohydrolase superfamily with a promiscuous ability to hydrolyze methylphosphonate esters.  

PubMed

The uncharacterized protein Rsp3690 from Rhodobacter sphaeroides is a member of the amidohydrolase superfamily of enzymes. In this investigation the gene for Rsp3690 was expressed in Escherichia coli and purified to homogeneity, and the three-dimensional structure was determined to a resolution of 1.8 Å. The protein folds as a distorted (?/?)8-barrel, and the subunits associate as a homotetramer. The active site is localized to the C-terminal end of the ?-barrel and is highlighted by the formation of a binuclear metal center with two manganese ions that are bridged by Glu-175 and hydroxide. The remaining ligands to the metal center include His-32, His-34, His-207, His-236, and Asp-302. Rsp3690 was shown to catalyze the hydrolysis of a wide variety of carboxylate esters, in addition to organophosphate and organophosphonate esters. The best carboxylate ester substrates identified for Rsp3690 included 2-naphthyl acetate (kcat/Km = 1.0 × 10(5) M(-1) s(-1)), 2-naphthyl propionate (kcat/Km = 1.5 × 10(5) M(-1) s(-1)), 1-naphthyl acetate (kcat/Km = 7.5 × 10(3) M(-1) s(-1)), 4-methylumbelliferyl acetate (kcat/Km = 2.7 × 10(3) M(-1) s(-1)), 4-nitrophenyl acetate (kcat/Km = 2.3 × 10(5) M(-1) s(-1)), and 4-nitrophenyl butyrate (kcat/Km = 8.8 × 10(5) M(-1) s(-1)). The best organophosphonate ester substrates included ethyl 4-nitrophenyl methylphosphonate (kcat/Km = 3.8 × 10(5) M(-1) s(-1)) and isobutyl 4-nitrophenyl methylphosphonate (kcat/Km = 1.1 × 10(4) M(-1) s(-1)). The (SP)-enantiomer of isobutyl 4-nitrophenyl methylphosphonate was hydrolyzed 10 times faster than the less toxic (RP)-enantiomer. The high inherent catalytic activity of Rsp3690 for the hydrolysis of the toxic enantiomer of methylphosphonate esters make this enzyme an attractive target for directed evolution investigations. PMID:24832101

Xiang, Dao Feng; Kumaran, Desigan; Swaminathan, Subramanyam; Raushel, Frank M

2014-06-01

338

Role of functional groups on Aspergillus niger biomass in the detoxification of hexavalent chromium.  

PubMed

Chromium (VI) contamination is not uncommon, especially near industries involved in leather tanning, chrome painting, metal cleaning and processing, wood preservation and alloy preparation. The mutagenic and carcinogenic properties of Chromium (VI) necessitate effective remedial processes. Difficulties associated with chemical and physical techniques to remediate a Chromium (VI) contaminated site to EPA recommended level (50 ppm), in addition to higher costs involved, assert the need for bioremedial measures. Biosorption can be one such solution to clean up heavy metal contamination. The objective of this study was to examine the main aspects of a possible strategy for the removal of Chromium (VI), employing Aspergillus niger biomass. The roles played by amines, carboxylic acids, phosphates, in Chromium (VI) biosorption were studied. Amino and the carboxy groups on the fungal cell wall play an important role in sorption. However, the role of carboxy group was far less than amino group. Surface adsorption of Chromium (VI) was also seen by scanning electron microscopy (SEM) thus indicating involvement of ion-exchange and surface adsorption mechanism in removal of Chromium (VI) ions. PMID:21117413

Narvekar, Sneha; Vaidya, Varsha K

2009-10-01

339

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

340

Synthesis and structure of dawson polyoxometalate-based, multifunctional, inorganic-organic hybrid compounds: organogermyl complexes with one terminal functional group and organosilyl analogues with two terminal functional groups.  

PubMed

Four novel multifunctional polyoxometalate (POM)-based inorganic-organic hybrid compounds, [?(2)-P(2)W(17)O(61){(RGe)}](7-) (Ge-1, R(1) = HOOC(CH(2))(2(-)) and Ge-2, R(2) = H(2)C?CHCH(2(-))) and [?(2)-P(2)W(17)O(61){(RSi)(2)O}](6-) (Si-1, R(1) and Si-2, R(2)), were prepared by incorporating organic chains having terminal functional groups (carboxylic acid and allyl groups) into monolacunary site of Dawson polyoxoanion [?(2)-P(2)W(17)O(61)](10-). In these POMs, new modification of the terminal functional groups was attained by introducing organogermyl and organosilyl groups. Dimethylammonium salts of the organogermyl complexes, (Me(2)NH(2))(7)[?(2)-P(2)W(17)O(61)(R(1)Ge)]·H(2)O MeN-Ge-1 and (Me(2)NH(2))(7)[?(2)-P(2)W(17)O(61)(R(2)Ge)]·4H(2)O MeN-Ge-2, were obtained as analytically pure crystals, in 22.8% and 55.3% yields, respectively, by stoichiometric reactions of [?(2)-P(2)W(17)O(61)](10-) with separately prepared Cl(3)GeC(2)H(4)COOH in water, and H(2)C?CHCH(2)GeCl(3) in a solvent mixture of water/acetonitrile. Synthesis and X-ray structure analysis of the Dawson POM-based organogermyl complexes were first successful. Dimethylammonium salts of the corresponding organosilyl complexes, (Me(2)NH(2))(6)[?(2)-P(2)W(17)O(61){(R(1)Si)(2)O}]·4H(2)O MeN-Si-1 and (Me(2)NH(2))(6)[?(2)-P(2)W(17)O(61){(R(2)Si)(2)O}]·6H(2)O MeN-Si-2, were also obtained as analytically pure crystalline crystals, in 17.1% and 63.5% yields, respectively, by stoichiometric reactions of [?(2)-P(2)W(17)O(61)](10-) with NaOOC(CH(2))(2)Si(OH)(2)(ONa) and H(2)C?CHCH(2)Si(OEt)(3). These complexes were characterized by elemental analysis, thermogravimetric and differential thermal analyses (TG/DTA), FTIR, solid-state ((31)P) and solution ((31)P, (1)H, and (13)C) NMR, and X-ray crystallography. PMID:21902232

Nomiya, Kenji; Togashi, Yoshihiro; Kasahara, Yuhki; Aoki, Shotaro; Seki, Hideaki; Noguchi, Marie; Yoshida, Shoko

2011-10-01

341

Applying AFM-based nanofabrication for measuring the thickness of nanopatterns: the role of head groups in the vertical self-assembly of omega-functionalized n-alkanethiols.  

PubMed

Molecules of n-alkanethiols with methyl head groups typically form well-ordered monolayers during solution self-assembly for a wide range of experimental conditions. However, we have consistently observed that, for either carboxylic acid or thiol-terminated n-alkanethiols, under certain conditions nanografted patterns are generated with a thickness corresponding precisely to a double layer. To investigate the role of head groups for solution self-assembly, designed patterns of omega-functionalized n-alkanethiols were nanografted with systematic changes in concentration. Nanografting is an in situ approach for writing patterns of thiolated molecules on gold surfaces by scanning with an AFM tip under high force, accomplished in dilute solutions of desired ink molecules. As the tip is scanned across the surface of a self-assembled monolayer under force, the matrix molecules are displaced from the surface and are immediately replaced with fresh molecules from solution to generate nanopatterns. In this report, side-by-side comparison of nanografted patterns is achieved for different matrix molecules using AFM images. The chain length and head groups (i.e., carboxyl, hydroxyl, methyl, thiol) were varied for the nanopatterns and matrix monolayers. Interactions such as head-to-head dimerization affect the vertical self-assembly of omega-functionalized n-alkanethiol molecules within nanografted patterns. At certain threshold concentrations, double layers were observed to form when nanografting with head groups of carboxylic acid and dithiols, whereas single layers were generated exclusively for nanografted patterns with methyl and hydroxyl groups, regardless of changes in concentration. PMID:20131892

Kelley, Algernon T; Ngunjiri, Johnpeter N; Serem, Wilson K; Lawrence, Steve O; Yu, Jing-Jiang; Crowe, William E; Garno, Jayne C

2010-03-01

342

Red electroluminescence of ruthenium sensitizer functionalized by sulfonate anchoring groups.  

PubMed

We have synthesized five novel Ru(ii) phenanthroline complexes with an additional aryl sulfonate ligating substituent at the 5-position [Ru(L)(bpy)2](BF4)2 (1), [Ru(L)(bpy)(SCN)2] (2), [Ru(L)3](BF4)2 (3), [Ru(L)2(bpy)](BF4)2 (4) and [Ru(L)(BPhen)(SCN)2] (5) (where L = 6-one-[1,10]phenanthroline-5-ylamino)-3-hydroxynaphthalene 1-sulfonic, bpy = 2,2'-bipyridine, BPhen = 4,7-diphenyl-1,10-phenanthroline), as both photosensitizers for oxide semiconductor solar cells (DSSCs) and light emitting diodes (LEDs). The absorption and emission maxima of these complexes red shifted upon extending the conjugation of the phenanthroline ligand. Ru phenanthroline complexes exhibit broad metal to ligand charge transfer-centered electroluminescence (EL) with a maximum near 580 nm. Our results indicated that a particular structure (2) can be considered as both DSSC and OLED devices. The efficiency of the LED performance can be tuned by using a range of ligands. Device (2) has a luminance of 550 cd m(-2) and maximum efficiency of 0.9 cd A(-1) at 18 V, which are the highest values among the five devices. The turn-on voltage of this device is approximately 5 V. The role of auxiliary ligands in the photophysical properties of Ru complexes was investigated by DFT calculation. We have also studied photovoltaic properties of dye-sensitized nanocrystalline semiconductor solar cells based on Ru phenanthroline complexes and an iodine redox electrolyte. A solar energy to electricity conversion efficiency (?) of 0.67% was obtained for Ru complex (2) under standard AM 1.5 irradiation with a short-circuit photocurrent density (Jsc) of 2.46 mA cm(-2), an open-circuit photovoltage (Voc) of 0.6 V, and a fill factor (ff) of 40%, which are all among the highest values for ruthenium sulfonated anchoring groups reported so far. Monochromatic incident photon to current conversion efficiency was 23% at 475 nm. Photovoltaic studies clearly indicated dyes with two SCN substituents yielded a higher Jsc for the cell than dyes with a tris-homoleptic anchor substituent. PMID:24818219

Shahroosvand, Hashem; Abbasi, Parisa; Mohajerani, Ezeddin; Janghouri, Mohammad

2014-06-28

343

Trypanosoma brucei prenylated-protein carboxyl methyltransferase prefers farnesylated substrates.  

PubMed Central

Carboxyl methylation of the C-terminal prenylated cysteine, which occurs in most farnesylated and geranylgeranylated proteins, is a reversible step and is implicated in the regulation of membrane binding and cellular functions of prenylated proteins such as GTPases. The gene coding for prenylated-protein carboxyl methyltransferase (PPMT) of the protozoan parasite Trypanosoma brucei has been cloned and expressed in the baculovirus/Sf9 cell system. The protein of 245 amino acids has 24-28% sequence identity to the orthologues from other species including human and Saccharomyces cerevisiae. Methyltransferase activity was detected in the membrane fraction from Sf9 cells infected with the recombinant baculovirus using N -acetyl- S -farnesylcysteine (AFC) and S -adenosyl[ methyl -(3)H]methionine ([(3)H]AdoMet) as substrates. Recombinant T. brucei PPMT prefers AFC to N -acetyl- S -geranylgeranylcysteine (AGGC) by 10-50-fold based on the V (max)/ K (m) values. Native PPMT activity detected in the membrane fraction from T. brucei procyclics displays similar substrate specificity ( approximately 40-fold preference for AFC over AGGC). In contrast, mouse liver PPMT utilizes both AFC and AGGC as substrates with similar catalytic efficiencies. Several cellular proteins of the T. brucei bloodstream form were shown to be carboxyl methylated in a cell-free system. Incorporation of [(3)H]methyl group from [(3)H]AdoMet into most of the proteins was significantly inhibited by AFC but not AGGC at 20 microM, suggesting that T. brucei PPMT acts on farnesylated proteins in the cell. Cells of the T. brucei bloodstream form show higher sensitivity to AFC and AGGC (EC(50)=70-80 microM) compared with mouse 3T3 cells (EC(50)>150 microM).

Buckner, Frederick S; Kateete, David P; Lubega, George W; Van Voorhis, Wesley C; Yokoyama, Kohei

2002-01-01

344

Trypanosoma brucei prenylated-protein carboxyl methyltransferase prefers farnesylated substrates.  

PubMed

Carboxyl methylation of the C-terminal prenylated cysteine, which occurs in most farnesylated and geranylgeranylated proteins, is a reversible step and is implicated in the regulation of membrane binding and cellular functions of prenylated proteins such as GTPases. The gene coding for prenylated-protein carboxyl methyltransferase (PPMT) of the protozoan parasite Trypanosoma brucei has been cloned and expressed in the baculovirus/Sf9 cell system. The protein of 245 amino acids has 24-28% sequence identity to the orthologues from other species including human and Saccharomyces cerevisiae. Methyltransferase activity was detected in the membrane fraction from Sf9 cells infected with the recombinant baculovirus using N -acetyl- S -farnesylcysteine (AFC) and S -adenosyl[ methyl -(3)H]methionine ([(3)H]AdoMet) as substrates. Recombinant T. brucei PPMT prefers AFC to N -acetyl- S -geranylgeranylcysteine (AGGC) by 10-50-fold based on the V (max)/ K (m) values. Native PPMT activity detected in the membrane fraction from T. brucei procyclics displays similar substrate specificity ( approximately 40-fold preference for AFC over AGGC). In contrast, mouse liver PPMT utilizes both AFC and AGGC as substrates with similar catalytic efficiencies. Several cellular proteins of the T. brucei bloodstream form were shown to be carboxyl methylated in a cell-free system. Incorporation of [(3)H]methyl group from [(3)H]AdoMet into most of the proteins was significantly inhibited by AFC but not AGGC at 20 microM, suggesting that T. brucei PPMT acts on farnesylated proteins in the cell. Cells of the T. brucei bloodstream form show higher sensitivity to AFC and AGGC (EC(50)=70-80 microM) compared with mouse 3T3 cells (EC(50)>150 microM). PMID:12141948

Buckner, Frederick S; Kateete, David P; Lubega, George W; Van Voorhis, Wesley C; Yokoyama, Kohei

2002-11-01

345

Functional Groups Based on Leaf Physiology: Are they Spatially and Temporally Robust?  

NASA Technical Reports Server (NTRS)

The functional grouping hypothesis, which suggests that complexity in function can be simplified by grouping species with similar responses, was tested in the Florida scrub habitat. Functional groups were identified based on how species in fire maintained FL scrub function in terms of carbon, water and nitrogen dynamics. The suite of physiologic parameters measured to determine function included both instantaneous gas exchange measurements obtained from photosynthetic light response curves and integrated measures of function. Using cluster analysis, five distinct physiologically-based functional groups were identified. Using non-parametric multivariate analyses, it was determined that these five groupings were not altered by plot differences or by the three different management regimes; prescribed burn, mechanically treated and burn, and fire-suppressed. The physiological groupings also remained robust between the two years 1999 and 2000. In order for these groupings to be of use for scaling ecosystem processes, there needs to be an easy-to-measure morphological indicator of function. Life form classifications were able to depict the physiological groupings more adequately than either specific leaf area or leaf thickness. THe ability of life forms to depict the groupings was improved by separating the parasitic Ximenia americana from the shrub category.

Foster, Tammy E.; Brooks, J. Renee; Quincy, Charles (Technical Monitor)

2002-01-01

346

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

347

4-Carboxypiperidinium 1-carboxycyclobutane-1-carboxylate.  

PubMed

The title salt, C(6)H(12)NO(2)(+)·C(6)H(7)O(4)(-) or ISO(+)·CBDC(-), is an ionic ensemble assisted by hydrogen bonds. The amino acid moiety (ISO or piperidine-4-carboxylic acid) has a protonated ring N atom (ISO(+) or 4-carboxypiperidinium), while the semi-protonated acid (CBDC(-) or 1-carboxycyclobutane-1-carboxylate) has the negative charge residing on one carboxylate group, leaving the other as a neutral -COOH group. The -(+)NH(2)- state of protonation allows the formation of a two-dimensional crystal packing consisting of zigzag layers stacked along a separated by van der Waals distances. The layers extend in the bc plane connected by a complex network of N-H···O and O-H···O hydrogen bonds. Wave-like ribbons, constructed from ISO(+) and CBDC(-) units and described by the graph-set symbols C(3)(3)(10) and R(3)(3)(14), run alternately in opposite directions along c. Intercalated between the ribbons are ISO(+) cations linked by hydrogen bonds, forming rings described by the graph-set symbols R(6)(6)(30) and R(4)(2)(18). A detailed analysis of the structures of the individual components and the intricate hydrogen-bond network of the crystal structure is given. PMID:22307260

Belandria, Lusbely M; Mora, Asiloé J; Delgado, Gerzon E; Briceño, Alexander

2012-02-01

348

Cloning and functional characterization of novel variants and tissue-specific expression of alternative amino and carboxyl termini of products of slc4a10.  

PubMed

Previous studies have shown that the electroneutral Na(+)/HCO(3) (-) 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 HCO(3) (-) 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. PMID:23409100

Liu, Ying; Wang, Deng-Ke; Jiang, De-Zhi; Qin, Xue; Xie, Zhang-Dong; Wang, Qing K; Liu, Mugen; Chen, Li-Ming

2013-01-01

349

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

350

A Re-evaluation of How Functional Groups Modify the Electronic Structure of Graphene Oxide.  

PubMed

The first 4 eV of the conduction band in graphene oxide is dominated by states from carbon sites that are in close proximity, but not directly bonded, to oxidizing functional groups. The carbon sites that are bonded directly to these groups, such as epoxide and hydroxyl groups, are much higher in energy. PMID:24903059

Hunt, Adrian; Kurmaev, Ernst Z; Moewes, Alex

2014-07-01

351

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

NASA Astrophysics Data System (ADS)

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(C 6H 5CHCHCOO) 2(H 2O) 2] ( I) with chelating carboxylate group (C 6H 5CHCHCOO = cinnamate), [Zn 2(C 6H 5COO) 4(pap) 2] ( II) with syn-syn bridging carboxylate (C 6H 5COO = benzoate; pap = papaverine), [Zn(C 6H 5CHCHCOO) 2(mpcm)] n ( III) with syn-anti carboxylate bridge (mpcm = methyl-3-pyridylcarbamate), [Zn(C 5H 4NCOO) 2(H 2O) 4] ( IV) with ionic carboxylate group (C 5H 4NCOO = nicotinate), [Zn(C 6H 5COO) 2(pcb) 2] n ( V) with monodentate carboxylate coordination (pcb = 3-pyridylcarbinol) and [Zn 3(C 6H 5COO) 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, ?exp = ?as(COO -) - ?s(COO -). Then the values ?exp were compared with those calculated from structural data of the carboxylate anion ( ?calc). The conclusions about the carboxylate binding which resulted from the ? 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 ?exp values on the magnitudes of Zn-O-C angles in bidentate carboxylate coordination was observed.

Zele?ák, V.; Vargová, Z.; Györyová, K.

2007-02-01

352

Functional end groups for polymers prepared using ring-opening metathesis polymerization  

Microsoft Academic Search

The precise placement of functional groups on the chain-ends of macromolecules is a major focus of polymer research. Most common living polymerization techniques offer specific methods of end-functionalization governed by the active propagating species and the kinetics of the polymerization reaction. Ring-opening metathesis polymerization has established itself as one of the most functional-group-tolerant living polymerization techniques known, but this tolerance

Stefan Hilf; Andreas F. M. Kilbinger

2009-01-01

353

Social Disinterest Attitudes and Group Cognitive-Behavioral Social Skills Training for Functional Disability in Schizophrenia  

PubMed Central

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.

Granholm, Eric; Ben-Zeev, Dror; Link, Peter C.

2009-01-01

354

Use of the Sequence Rule for Indexing Functional Groups in Organic Compounds  

ERIC Educational Resources Information Center

A new method of indexing functional groups in organic compounds is described, utilizing the Cahn-Ingold-Prelog sequence rule. Functional carbon atoms are first classified by functionality, a measure of the oxidation state, then ordered by means of a modified sequence rule. Substructure searching and other applications are discussed. (30…

Hudrlik, Paul F.

1973-01-01

355

Chemical Properties of a Perfluoropolyether Lubricant with Functional Groups of Pentafluorobenzyl on Hard Disk Media  

NASA Astrophysics Data System (ADS)

A perfluoropolyether lubricant (LUB-B) with pentafluorobenzyl functional groups at both ends of the main chain was synthesized by the authors, and the chemical characteristics of its film of 2.0± 0.2 nm thickness on hard disk media were investigated by time-of-flight secondary ion mass spectrometry and compared with those of a synthesized lubricant (LUB-A) with benzyl groups and the commercial AM3001 lubricant with (3,4-dioxomethylenephenyl)methyl groups. AM3001 lost 94% of its functional groups from the main chain on the disk surface after a 672-h exposure even in a regular clean room at 23°C and 55%RH@. LUB-A lost 35% of its functional groups after a 768-h exposure. LUB-B hardly lost any of its functional groups even after a 768-h exposure, and showed the highest chemical stability. It was suggested that hydrolysis at the ether linkage between the main chain and the functional group eliminated the functional groups from the main chain. The decomposition rate seemed to depend on the chemical stability of the benzyl cation.

Hara, Hiroki; Nishiguchi, Ikuzo; Sugi, Seiki; Yamamoto, Yoshimasa; Tsuboi, Shigeru; Itoh, Kotaro

2001-05-01

356

Evaluation of a series of prolylamidepyridines as the chiral derivatization reagents for enantioseparation of carboxylic acids by LC-ESI-MS/MS and the application to human saliva.  

PubMed

Mass spectrometry has become a popular analytical tool because of its high sensitivity and specificity. The use of a chiral derivatization reagent for the mass spectrometry (MS) detection seems to be efficient for the enantiomeric separation of racemates. However, the number of chiral reagents for the liquid chromatography (LC)-MS/MS analysis is very limited. According to these observations, we are currently in the process of developing novel labeling reagents for chiral molecules in MS/MS analysis. The derivatization reagent that is effective for enhancing not only the electrospray ionization-MS/MS sensitivity but also the reversed-phase LC resolution of carboxylic acid enantiomers should have a highly proton-affinitive moiety and an asymmetric structure near the reactive functional group. Furthermore, the resulting derivative has to provide a characteristic product ion suitable for the selected reaction monitoring. Based upon these considerations, a series of prolylamidepyridines ((S)-N-pyrrolidine-2-carboxylic acid N-(pyridine-2-yl)amide (PCP2), (S)-N-pyrrolidine-2-carboxylic acid N-(pyridine-3-yl)amide, and (S)-N-pyrrolidine-2-carboxylic acid N-(pyridine-4-yl)amide) was synthesized as ideal labeling reagents for the enantioseparation of chiral carboxylic acids and evaluated in terms of separation efficiency and detection sensitivity by ultra-performance LC (UPLC)-MS/MS. Among the synthesized reagents, PCP2 was the most efficient chiral derivatization reagent for the enantioseparation of carboxylic acid. The Rs values and the detection limits of the derivatives of non-steroidal anti-inflammatory drugs, which were selected as the representative carboxylic acids, were in the range of 2.52-6.07 and 49-260 amol, respectively. The sensitive detection of biological carboxylic acids (detection limits, 32-520 amol) was also carried out by the proposed method using PCP2 and UPLC-MS/MS. The PCP2 was applied to the determination of carboxylic acids in human saliva. Several biological carboxylic acids, such as lactic acid (LA), 3-hydroxybutylic acid, maric acid, succinic acid, ?-ketoglutalic acid, and citric acid, were clearly identified in the saliva of healthy persons and diabetic patients. Furthermore, the ratio of D-LA in diabetic patients was higher than that in normal subjects. Judging from these results, PCP2 seems to be a useful chiral derivatization reagent for the determination not only of chiral, but also achiral, carboxylic acids in real samples. PMID:24500756

Kuwabara, Tomohiro; Takayama, Takahiro; Todoroki, Kenichiro; Inoue, Koichi; Min, Jun Zhe; Toyo'oka, Toshimasa

2014-04-01

357

Divergence of Function in Sequence-Related Groups of Escherichia coli Proteins  

PubMed Central

The most prominent mechanism of molecular evolution is believed to have been duplication and divergence of genes. Proteins that belong to sequence-related groups in any one organism are candidates to have emerged from such a process and to share a common ancestor. Groups of proteins in Escherichia coli having sequence similarity are mostly composed of proteins with closely related function, but some groups comprise proteins with unrelated functions. In order to understand how function can change while sequences remain similar, we have examined some of these groups in detail. The enzymes analyzed in this work include representatives of amidotransferases, phosphotransferases, decarboxylases, and others. Most sequence-related groups contain enzymes that are in the same classes of Enzyme Commission (EC) numbers. We have concentrated on groups that are heterogeneous in that respect, and also on groups containing more than one enzyme of any pathway. We find that although the EC number may differ, the reaction chemistry of these sequence-related proteins is the same or very similar. Some of these families illustrate how diversification has taken place in evolution, using common features of either reaction chemistry or ligand specificity, or both, to create catalysts for different kinds of biochemical reactions. This information has relevance to the area of functional genomics in which the activities of gene products of unknown reading frames are attributed by analogy to the functions of sequence-related proteins of known function.

Nahum, Laila Alves; Riley, Monica

2001-01-01

358

Grouping  

NSDL National Science Digital Library

This interactive Flash applet models the measurement interpretation of division. A child or teacher chooses a total number of objects and a divisor representing the size of equal groups. The applet allows the user to move the objects into equal groups and links the process to jumps on a number line. The applet can be used to introduce children to remainders and to reinforce the language and notation of division. It works well on an interactive white board or projector. A teacher's guide to this collection of applets is cataloged separately.

2006-01-01

359

4-Amino-pyridinium cis-2-carb-oxy-cyclo-hexane-1-carboxyl-ate  

PubMed Central

In the structure of the title molecular salt, C5H7N2 +·C8H11O4 ?, the cis monoanions associate through short O—H?O hydrogen bonds in the carb­oxy­lic acid groups [graph set C(7)], forming zigzag chains which extend along the c axis. These are inter­linked through pyridinium and amine N—H?O hydrogen bonds, giving a three-dimensional network structure.

Smith, Graham; Wermuth, Urs D.

2011-01-01

360

Production of Printed Indexes of Chemical Reactions. I. Analysis of Functional Group Interconversions  

ERIC Educational Resources Information Center

A program is described which identifies functional group interconversion reactions, hydrogenations, and dehydrogenations in a data base containing structures encoded as Wiswesser Line Notations. Production of the data base is briefly described. (17 references) (Authors)

Clinging, R.; Lynch, M. F.

1973-01-01

361

Few-body hierarchy in non-relativistic functional renormalization group equations and a decoupling theorem  

NASA Astrophysics Data System (ADS)

For non-relativistic quantum field theory in the few-body limit with instantaneous interactions it is shown within the functional renormalization group formalism that propagators are not renormalized and that the renormalization group equations of one-particle irreducible vertex functions are governed by a hierarchical structure. This hierarchy allows to solve the equations in the n-body sector without knowledge or assumptions about the m-body sectors where m>n.

Floerchinger, Stefan

2014-07-01

362

Anatomic and Functional Variability: The Effects of Filter Size in Group fMRI Data Analysis  

Microsoft Academic Search

In the analysis of group fMRI scans, an optimal spatial filter should be large enough to accurately blend functionally homologous anatomic regions, yet small enough not to blur the functionally distinct regions. Hanning filters varying from 0.0 to 18.0 mm were evaluated in a group analysis of six healthy controls performing a simple finger-tapping paradigm. Test–retest reliability and Talairach-based measurements

Tonya White; Daniel O'Leary; Vincent Magnotta; Stephan Arndt; Michael Flaum; Nancy C. Andreasen

2001-01-01

363

Ecophysiological traits of plant functional groups in forest and pasture ecosystems from eastern Amazônia, Brazil  

Microsoft Academic Search

The plant functional group approach has the potential to clarify ecological patterns and is of particular importance in simplifying\\u000a the application of ecological models in high biodiversity ecosystems. Six functional groups (pasture grass, pasture sapling,\\u000a top-canopy tree, top-canopy liana, mid canopy tree, and understory tree) were established a priori based on ecosystem inhabited,\\u000a life form, and position within the forest

Tomas F. Domingues; Luiz A. Martinelli; James R. Ehleringer

2007-01-01

364

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

365

The interaction of carboxylic acids with aluminium oxides: journeying from a basic understanding of alumina nanoparticles to water treatment for industrial and humanitarian applications.  

PubMed

Carboxylic acids are found to react with aluminium oxides via a topotactic reaction such that the carboxylate acts as a bridging ligand. This reaction allows for carboxylate-functionalized alumina nanoparticles to be prepared directly from boehmite (AlOOH). Understanding the structural relationship between molecular and surface species allows for the rationalization/prediction of suitable alternative ligands as well as alternative oxide surfaces. The identity of the carboxylate substituent controls the pH stability of a nanoparticle as well as the porosity and processability of ceramics prepared by thermolysis. Through the choice of functional groups on the carboxylic acid the properties of the alumina surface or alumina nanoparticle can be tailored. For example, the solubility/miscibility of nanoparticles can be tuned to the solvent/matrix, and the wettability to be varied from hydrophobic to super hydrophilic. The choice Zwitter ionic substituents on alumina micro-/ultra-filtration membranes are found to enhance the flux and limit fouling while allowing for the facile separation of organic compounds from water. Examples are presented of purification of frac and flow-back water from oil well production as well as providing drinking water from contaminated sources in underdeveloped regions. PMID:24728503

Barron, Andrew R

2014-06-14

366

Functional Groups Based on Leaf Physiology: Are they Spatially and Temporally Robust?  

NASA Technical Reports Server (NTRS)

The functional grouping hypothesis, which suggests that complexity in ecosystem function can be simplified by grouping species with similar responses, was tested in the Florida scrub habitat. Functional groups were identified based on how species in fire maintained Florida scrub regulate exchange of carbon and water with the atmosphere as indicated by both instantaneous gas exchange measurements and integrated measures of function (%N, delta C-13, delta N-15, C-N ratio). Using cluster analysis, five distinct physiologically-based functional groups were identified in the fire maintained scrub. These functional groups were tested to determine if they were robust spatially, temporally, and with management regime. Analysis of Similarities (ANOSIM), a non-parametric multivariate analysis, indicated that these five physiologically-based groupings were not altered by plot differences (R = -0.115, p = 0.893) or by the three different management regimes; prescribed burn, mechanically treated and burn, and fire-suppressed (R = 0.018, p = 0.349). The physiological groupings also remained robust between the two climatically different years 1999 and 2000 (R = -0.027, p = 0.725). Easy-to-measure morphological characteristics indicating functional groups would be more practical for scaling and modeling ecosystem processes than detailed gas-exchange measurements, therefore we tested a variety of morphological characteristics as functional indicators. A combination of non-parametric multivariate techniques (Hierarchical cluster analysis, non-metric Multi-Dimensional Scaling, and ANOSIM) were used to compare the ability of life form, leaf thickness, and specific leaf area classifications to identify the physiologically-based functional groups. Life form classifications (ANOSIM; R = 0.629, p 0.001) were able to depict the physiological groupings more adequately than either specific leaf area (ANOSIM; R = 0.426, p = 0.001) or leaf thickness (ANOSIM; R 0.344, p 0.001). The ability of life forms to depict the physiological groupings was improved by separating the parasitic Ximenia americana from the shrub category (ANOSIM; R = 0.794, p = 0.001). Therefore, a life form classification including parasites was determined to be a good indicator of the physiological processes of scrub species, and would be a useful method of grouping for scaling physiological processes to the ecosystem level.

Foster, Tammy E.; Brooks, J. Renee

2004-01-01

367

Biocatalytic reduction of carboxylic acids.  

PubMed

An increasing demand for non-petroleum-based products is envisaged in the near future. Carboxylic acids such as citric acid, succinic acid, fatty acids, and many others are available in abundance from renewable resources and they could serve as economic precursors for bio-based products such as polymers, aldehyde building blocks, and alcohols. However, we are confronted with the problem that carboxylic acid reduction requires a high level of energy for activation due to the carboxylate's thermodynamic stability. Catalytic processes are scarce and often their chemoselectivity is insufficient. This review points at bio-alternatives: currently known enzyme classes and organisms that catalyze the reduction of carboxylic acids are summarized. Two totally distinct biocatalyst lines have evolved to catalyze the same reaction: aldehyde oxidoreductases from anaerobic bacteria and archea, and carboxylate reductases from aerobic sources such as bacteria, fungi, and plants. The majority of these enzymes remain to be identified and isolated from their natural background in order to evaluate their potential as industrial biocatalysts. PMID:24737783

Napora-Wijata, Kamila; Strohmeier, Gernot A; Winkler, Margit

2014-06-01

368

Functionalization of Boron and Nitrogen-Doped Graphene and Carbon Nanotubes: An Ab Initio Study  

Microsoft Academic Search

We study the mechanism of covalent functionalization of boron (B) and nitrogen (N) doped graphene and carbon nanotubes by carboxyl (COOH) groups. Our calculations are carried out using density functional theory combined with the generalized gradient approximation for the exchange-correlation functional. The binding energies and equilibrium geometries of carboxylated B\\/N-doped graphene sheets and carbon nanotubes are examined in cases of

Nabil Al-Aqtash; Igor Vasiliev

2010-01-01

369

Wigner functions for a class of semi-direct product groups  

NASA Astrophysics Data System (ADS)

Following a general method proposed earlier, we construct here Wigner functions defined on coadjoint orbits of a class of semidirect product groups. The groups in question are such that their unitary duals consist purely of representations from the discrete series and each unitary irreducible representation is associated with a coadjoint orbit. The set of all coadjoint orbits (hence UIRs) is finite and their union is dense in the dual of the Lie algebra. The simple structure of the groups and the orbits enables us to compute the various quantities appearing in the definition of the Wigner function explicitly. A large number of examples, with potential use in image analysis, is worked out.

Krasowska, Anna E.; Twareque Ali, S.

2003-03-01

370

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

371

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

2011-01-01

372

Group Statistics of DTI Fiber Bundles Using Spatial Functions of Tensor Measures  

Microsoft Academic Search

\\u000a We present a framework for hypothesis testing of differences between groups of DTI fiber tracts. An anatomical, tract-oriented\\u000a coordinate system provides a basis for estimating the distribution of diffusion properties. The parametrization of sampled,\\u000a smooth functions is normalized across a population using DTI atlas building. Functional data analysis, an extension of multivariate\\u000a statistics to continuous functions is applied to the

Casey B. Goodlett; P. Thomas Fletcher; John H. Gilmore; Guido Gerig

2008-01-01

373

Synthesis and structure of m-terphenyl-based cyclophanes with nitrogen intra-annular functional groups.  

PubMed

[structure: see text] Herein we describe an efficient synthesis of cyclophanes comprised of intra-annular nitrogen functional groups through a template-promoted cyclization by ring-closing metathesis (RCM). The synthesis proceeds through condensation of meta-styryl anilines with acenaphthenequinone to form the templates, followed by RCM with Grubb's second-generation catalyst to afford cyclophanes with internal alpha-diimine functionality. Prolonged hydrogenation efficiently removes the template to provide a macrocycle containing the diamine functionality. PMID:15012051

Camacho, Drexel H; Salo, Eric V; Guan, Zhibin

2004-03-18

374

Representations of the Weyl group and Wigner functions for SU(3)  

NASA Astrophysics Data System (ADS)

Bases for SU(3) irreps are constructed on a space of three-particle tensor products of two-dimensional harmonic oscillator wave functions. The Weyl group is represented as the symmetric group of permutations of the particle coordinates of these spaces. Wigner functions for SU(3) are expressed as products of SU(2) Wigner functions and matrix elements of Weyl transformations. The constructions make explicit use of dual reductive pairs which are shown to be particularly relevant to problems in optics and quantum interferometry.

Rowe, D. J.; Sanders, B. C.; de Guise, H.

1999-07-01

375

Vibrational spectroscopy of functional group chemistry and arsenate coordination in ettringite  

Microsoft Academic Search

The functional group chemistry and coordination of AsO43?-sorption complexes in ettringite [Ca6Al2(SO4)3(OH)12·26H2O] were evaluated as a function of sorption type (adsorption, coprecipitation) and pH using Raman and Fourier Transform infrared (FTIR) spectroscopies. The reactive functional groups of ettringite, ?Al-OH, ?Ca-OH2, and ?Ca2-OH exhibit broad overlapping OH bands in the range 3600–3200 cm?1, prohibiting separation of component vibrational bands. The SO42?

Satish C. B. Myneni; Samuel J. Traina; Glenn A. Waychunas; Terry J. Logan

1998-01-01

376

Fragrance material review on methyl hexyl oxo cyclopentanone carboxylate.  

PubMed

A toxicologic and dermatologic review of methyl hexyl oxo cyclopentanone carboxylate when used as a fragrance ingredient is presented. Methyl hexyl oxo cyclopentanone carboxylate is a member of the fragrance structural group ketones cyclopentanones and cyclopentenones. The common characteristic structural element of the group members is a cyclopentanone or cyclopentenone ring with a straight or branched chain alkane or alkene substituent. This review contains a detailed summary of all available toxicology and dermatology papers that are related to this individual fragrance ingredient and is not intended as a stand-alone document. Available data for methyl hexyl oxo cyclopentanone carboxylate were evaluated then summarized and includes physical properties, acute toxicity, skin irritation, skin sensitization, and genotoxicity data. A safety assessment of the entire ketones cyclopentanones and cyclopentenones will be published simultaneously with this document; please refer to Belsito et al. (this issue) for an overall assessment of the safe use of this material and all ketones cyclopentanones and cyclopentenones in fragrances. PMID:22449537

Scognamiglio, J; Jones, L; Letizia, C S; Api, A M

2012-10-01

377

Arrival order among native plant functional groups does not affect invasibility of constructed dune communities.  

PubMed

Different arrival order scenarios of native functional groups to a site may influence both resource use during development and final community structure. Arrival order may then indirectly influence community resistance to invasion. We present a mesocosm experiment of constructed coastal dune communities that monitored biotic and abiotic responses to different arrival orders of native functional groups. Constructed communities were compared with unplanted mesocosms. We then simulated a single invasion event by bitou (Chrysanthemoides monilifera ssp. rotundata), a dominant exotic shrub of coastal communities. We evaluated the hypothesis that plantings with simultaneous representation of grass, herb and shrub functional groups at the beginning of the experiment would more completely sequester resources and limit invasion than staggered plantings. Staggered plantings in turn would offer greater resource use and invasion resistance than unplanted mesocosms. Contrary to our expectations, there were few effects of arrival order on abiotic variables for the duration of the experiment and arrival order was unimportant in final community invasibility. All planted mesocosms supported significantly more invader germinants and significantly less invader abundance than unplanted mesocosms. Native functional group plantings may have a nurse effect during the invader germination and establishment phase and a competitive function during the invader juvenile and adult phase. Arrival order per se did not affect resource use and community invasibility in our mesocosm experiment. While grass, herb and shrub functional group plantings will not prevent invasion success in restored communities, they may limit final invader biomass. PMID:23468238

Mason, T J; French, K; Jolley, D

2013-10-01

378

Southern GEMS groups - II. HI distribution, mass functions and HI deficient galaxies  

NASA Astrophysics Data System (ADS)

We investigate the neutral hydrogen (HI) content of 16 groups for which we have multiwavelength data including X-ray observations. Wide-field imaging of the groups was obtained with the 20-cm multibeam system on the 64-m Parkes telescope. We have detected 10 previously uncatalogued HI sources, one of which has no visible optical counterpart. We examine the HI properties of the groups, compared to their X-ray characteristics, finding that those groups with a higher X-ray temperature and luminosity contain less HI per galaxy. The HI content of a group depends on its morphological make-up, with those groups dominated by early-type galaxies containing the least total HI. We determined the expected HI for the spiral galaxies in the groups, and found that a number of the galaxies were HI deficient. The HI deficient spirals were found both in groups with and without a hot intragroup medium. The HI deficient galaxies were not necessarily found at the centre of the groups, however, we did find that two-thirds of HI deficient galaxies were found within about 1Mpc from the group centre, indicating that the group environment is affecting the gas loss from these galaxies. We determined the HI mass function for a composite sample of 15 groups, and found that it is significantly flatter than the field HI mass function. We also find a lack of high HI mass galaxies in groups. One possible cause of this effect is the tidal stripping of HI gas from spiral galaxies as they are pre-processed in groups. The observations were obtained with the Australia Telescope which is funded by the Commonwealth of Australia for operations as a National Facility managed by CSIRO. E-mail: vkilborn@swin.edu.au

Kilborn, Virginia A.; Forbes, Duncan A.; Barnes, David G.; Koribalski, Bärbel S.; Brough, Sarah; Kern, Katie

2009-12-01

379

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

380

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

2013-06-18

381

Disorder in the anionic part of catena-poly[[(pyrazine-2-carboxyl-ato)copper(II)]-?-pyrazine-2-carboxyl-ato  

PubMed Central

The title compound, [Cu(C5H3N2O2)0.88(C6H4NO2)1.12]n, is characterized by disorder of the anion, resulting from a statistical occupation in a 0.44?(3):0.56?(3) ratio of pyrazine-2-carboxylate and pyridine-2-carboxylate. The compound was isolated during attempts to synthesize a mixed-ligand coordination polymer by solvothermal reaction between copper(II) nitrate and equimolar mixtures of pyrazine-2-carboxylic acid and pyridine-2-carb­oxy­lic acid in a mixture of water and EtOH. The difference in the two components of the compound is due to substitutional disorder of a CH group for one of the N atoms of the pyrazine ring which share the same site in the structure. In the crystal structure, the CuII atom lies on an inversion centre and is six-coordinated in a distorted N2O4 geometry. The carboxyl­ate group carbonyl O atoms are weakly coordinated to an equivalent CuII atom that is translated one unit cell in the a-axis direction, thus forming a polymeric chain through carboxyl­ate bridges.

Albanez, Joselyn; Brito, Ivan; Cardenas, Alejandro; Lopez-Rodriguez, Matias

2012-01-01

382

Density functional study of electronic, charge density, and chemical bonding properties of 9-methyl-3-Thiophen-2-YI-Thieno [3,2-e] [1, 2, 4] Thriazolo [4,3-c] pyrimidine-8-Carboxylic acid ethyl ester crystals  

NASA Astrophysics Data System (ADS)

A comprehensive theoretical density functional investigation of the electronic crystal structure, chemical bonding, and the electron charge densities of 9-Methyl-3-Thiophen-2-YI-Thieno [3, 2-e] [1, 2, 4] Thriazolo [4,3-c] Pyrimidine-8-Carboxylic Acid Ethyl Ester (C15H12N4O2S2) is performed. The density of states at Fermi level equal to 5.50 (3.45) states/Ry cell, and the calculated bare electronic specific heat coefficient is found to be 0.95 (0.59) mJ/mole-K2 for the local density approximation (Engel-Vosko generalized gradient approximation). The electronic charge density space distribution contours in (1 0 0) and (1 1 0) planes were calculated. We find that there are two independent molecules (A and B) in the asymmetric unit exhibit intramolecular C-H…O, C-H…N interactions. This intramolecular interaction is different in molecules A and B, where A molecule show C-H…O interaction while B molecule exhibit C-H…N interaction. We should emphasis that there is ?-? interaction between the pyrimidine rings of the two neighbors B molecules gives extra strengths and stabilizations to the superamolecular structure. The calculated distance between the two neighbors pyrimidine rings found to be 3.345 Å, in good agreement with the measured one (3.424(1) Å).

Reshak, A. H.; Kamarudin, H.; Alahmed, Z. A.; Auluck, S.; Chyský, Jan

2014-06-01

383

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

384

2-Amino-pyridinium 1-phenyl-cyclo-propane-1-carboxyl-ate  

PubMed Central

In the title salt, C5H7N2 +·C10H9O2 ?, 2-amino­pyridine and 1-phenyl­cyclo­propane-1-carb­oxy­lic acid crystallize together, forming a 2-amino­pyridinium–carboxyl­ate supra­molecular heterosynthon involving two N—H?O hydrogen bonds, which in turn dimerizes to form a four-component supra­molecular unit also sustained by N—H?O hydrogen bonding. A C—H?? inter­action between a pyridine C—H group and the centroid of the phenyl ring of the anion further stabilizes the four-component supra­molecular unit. The overall crystal packing also features C—H?O inter­actions.

He, Guangwen; Aitipamula, Srinivasulu; Chow, Pui Shan; Tan, Reginald B. H.

2010-01-01

385

Critical Design Features of Phenyl Carboxylate-Containing Polymer Microbicides  

PubMed Central

Recent studies of cellulose-based polymers substituted with carboxylic acids like cellulose acetate phthalate (CAP) have demonstrated the utility of using carboxylic acid groups instead of the more common sulfate or sulfonate moieties. However, the pKa of the free carboxylic acid group is very important and needs careful selection. In a polymer like CAP the pKa is approximately 5.28. This means that under the low pH conditions found in the vaginal lumen, CAP would be only minimally soluble and the carboxylic acid would not be fully dissociated. These issues can be overcome by substitution of the cellulose backbone with a moiety whose free carboxylic acid group(s) has a lower pKa. Hydroxypropyl methylcellulose trimellitate (HPMCT) is structurally similar to CAP; however, its free carboxylic acids have pKas of 3.84 and 5.2. HPMCT, therefore, remains soluble and molecularly dispersed at a much lower pH than CAP. In this study, we measured the difference in solubility and dissociation between CAP and HPMCT and the effect these parameters might have on antiviral efficacy. Further experiments revealed that the degree of acid substitution of the cellulose backbone can significantly impact the overall efficacy of the polymer, thereby demonstrating the need to optimize any prospective polymer microbicide with respect to pH considerations and the degree of acid substitution. In addition, we have found HPMCT to be a potent inhibitor of CXCR4, CCR5, and dual tropic strains of human immunodeficiency virus in peripheral blood mononuclear cells. Therefore, the data presented herein strongly support further evaluation of an optimized HPMCT variant as a candidate microbicide.

Rando, Robert F.; Obara, Sakae; Osterling, Mark C.; Mankowski, Marie; Miller, Shendra R.; Ferguson, Mary L.; Krebs, Fred C.; Wigdahl, Brian; Labib, Mohamed; Kokubo, Hiroyasu

2006-01-01

386

Critical design features of phenyl carboxylate-containing polymer microbicides.  

PubMed

Recent studies of cellulose-based polymers substituted with carboxylic acids like cellulose acetate phthalate (CAP) have demonstrated the utility of using carboxylic acid groups instead of the more common sulfate or sulfonate moieties. However, the pK(a) of the free carboxylic acid group is very important and needs careful selection. In a polymer like CAP the pK(a) is approximately 5.28. This means that under the low pH conditions found in the vaginal lumen, CAP would be only minimally soluble and the carboxylic acid would not be fully dissociated. These issues can be overcome by substitution of the cellulose backbone with a moiety whose free carboxylic acid group(s) has a lower pK(a). Hydroxypropyl methylcellulose trimellitate (HPMCT) is structurally similar to CAP; however, its free carboxylic acids have pK(a)s of 3.84 and 5.2. HPMCT, therefore, remains soluble and molecularly dispersed at a much lower pH than CAP. In this study, we measured the difference in solubility and dissociation between CAP and HPMCT and the effect these parameters might have on antiviral efficacy. Further experiments revealed that the degree of acid substitution of the cellulose backbone can significantly impact the overall efficacy of the polymer, thereby demonstrating the need to optimize any prospective polymer microbicide with respect to pH considerations and the degree of acid substitution. In addition, we have found HPMCT to be a potent inhibitor of CXCR4, CCR5, and dual tropic strains of human immunodeficiency virus in peripheral blood mononuclear cells. Therefore, the data presented herein strongly support further evaluation of an optimized HPMCT variant as a candidate microbicide. PMID:16940105

Rando, Robert F; Obara, Sakae; Osterling, Mark C; Mankowski, Marie; Miller, Shendra R; Ferguson, Mary L; Krebs, Fred C; Wigdahl, Brian; Labib, Mohamed; Kokubo, Hiroyasu

2006-09-01

387

Sensitive and selective electrochemical determination of quinoxaline-2-carboxylic acid based on bilayer of novel poly(pyrrole) functional composite using one-step electro-polymerization and molecularly imprinted poly(o-phenylenediamine).  

PubMed

A facile and efficient molecularly imprinted polymer (MIP) recognition element of electrochemical sensor was fabricated by directly electro-polymerizing monomer o-phenylenediamine (oPD) in the presence of template quinoxaline-2-carboxylic acid (QCA), based on one-step controllable electrochemical modification of poly(pyrrole)-graphene oxide-binuclear phthalocyanine cobalt (II) sulphonate (PPY-GO-BiCoPc) functional composite on glassy carbon electrode (GCE). The MIP film coated on PPY-GO-BiCoPc functional composite decorated GCE (MIP/PPY-GO-BiCoPc/GCE) was presented for the first time. The synergistic effect and electro-catalytic activity toward QCA redox of PPY-GO-BiCoPc functional composite were discussed using various contrast tests. Also, the effect of experimental variables on the current response such as, electro-polymerization cycles, template/monomer ratio, elution condition for template removal, pH of the supporting electrolyte and accumulation time, were investigated in detail. Under the optimized conditions, the proposed MIP sensor possessed a fast rebinding dynamics and an excellent recognition capacity to QCA, while the anodic current response of square wave voltammetry (SWV) was well-proportional to the concentration of QCA in the range of 1.0×10(-8)-1.0×10(-4) and 1.0×10(-4)-5.0×10(-4) mol L(-1) with a low detection limit of 2.1 nmol L(-1). The established sensor was applied successfully to determine QCA in commercial pork and chicken muscle samples with acceptable recoveries (91.6-98.2%) and satisfactory precision (1.9-3.5% of SD), demonstrating a promising feature for applying the MIP sensor to the measurement of QCA in real samples. PMID:24331049

Yang, Yukun; Fang, Guozhen; Wang, Xiaomin; Pan, Mingfei; Qian, Hailong; Liu, Huilin; Wang, Shuo

2014-01-01

388

NMR determination of total carbonyls and carboxyls: a tool for tracing the evolution of atmospheric oxidized organic aerosols.  

PubMed

Nuclear magnetic resonance (NMR) spectroscopy is used to investigate the chemical composition of organic aerosol in terms of functional group distribution with a special focus on secondary organic aerosol (SOA) formation. The knowledge of the functional group composition is a benchmark for understanding how SOA components partition into the particulate phase and undergo chemical transformation. The paper presents a new chemical derivatization procedure coupled to proton NMR (1H NMR) analysis for the specific determination of total carbonylic groups in atmospheric aerosol samples, which couples with the procedure for determination of total carboxylic acid groups described in a previous work. A first deployment of the combined techniques for the analysis of PM10 samples collected in the Po Valley in the warm season shows that the concentration in the particulate phase of total carbonyls varies and covaries with respect to those of carboxylic acids and of less-oxidized functional groups. The proposed methodology provides the breakdown of the oxygenated fraction of the organic aerosol into major functional groups through well-established chemical methods and can be used to benchmark the more sensitive and widely used aerosol mass spectrometric techniques. PMID:18678015

Moretti, F; Tagliavini, E; Decesari, S; Facchini, M C; Rinaldi, M; Fuzzi, S

2008-07-01

389

Not all carboxylates are created equal: Differences in interaction of carboxylated peptides with a CaCO3 dimer.  

PubMed

The carboxylate group has been considered the "glue" for mineralizing proteins because of its ability to bind Ca(II). We propose the calcium salts of dicarboxylated dipeptides (Asp-Asp and Glu-Glu) as the smallest models of a mineralizing protein active site. Molecular dynamics/simulated annealing was used for conformational search of the dipeptide global minimum. Semiempirical blind docking was used for configurational search of all cluster-peptide complexes and structures were then optimized in the gas phase at the RI-MP2/SVP level of theory. Solvent effects were also taken into account. We found that the energy of interaction of the calcium carboxylates with a calcium carbonate dimer can be either favorable or unfavorable depending on side-chain length, so side-chain carboxylic groups belonging to different amino acids may show different affinities towards calcium carbonate. PMID:24999163

Rosas-García, Víctor M; de León-Abarte, Isidro; Vidal-López, Germán; Palacios-Pargas, Arturo; Jáuregui-Prado, Xóchitl

2014-08-01

390

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

391

TMSCN/DBU-mediated facile redox transformation of ?,?-unsaturated aldehydes to carboxylic acid derivatives.  

PubMed

Redox transformation of an ?,?-unsaturated aldehyde to a carboxylic acid derivative by means of a combination of TMSCN and DBU was investigated. In addition to the wide use of the carboxylic acid derivatives provided by this reaction, temperature-dependent control of the kinetic or thermodynamic protonation pattern was found to selectively switch the stereochemistry of the acyl group in the product. PMID:24446807

Kaise, Hiromi; Shimokawa, Jun; Fukuyama, Tohru

2014-02-01

392

Two dimensional self-assembly of bis-acylureas having various functional end groups.  

PubMed

We present the synthesis and morphology study of thirteen bis-acylurea molecules with various functional end groups. The bis-acylureas have two acylurea groups, -NH-CO-NH-CO-, divided by a pentamethylene spacer, -(CH(2))(5)-, and two symmetric functional end groups, such as, aliphatic, benzyl, mono- and bi-thiophenyl, sulfur-containing, and propargyl (HC[triple bond]CCH(2)-) moieties. The bis-acylureas were synthesized by the coupling reactions of ureas with pimeloyl chloride or pimelic acid. Upon cooling from hot isotropic solutions, the bis-acylureas spontaneously form supermolecules. In the cases of aliphatic, benzyl, mono- and bi-thiophenyl functional groups, two dimensional supramolecular structures with molecularly flat surfaces were formed. Single crystal X-ray diffraction results demonstrate that each bis-acylurea molecule forms biaxial hydrogen bonds with four adjacent molecules forming a grid-like crystalline structure. Among the bis-acylureas with sulfur-containing end groups, those with sulfide (-S-) and disulfide (-SS-) moieties self-organize into two dimensional superstructures, while those with thiol (-SH) and bulky protecting group (-S-trityl) precipitate with irregular shapes. The bis-acylurea with propargyl end groups form superstructures of low order possibly due to the steric effect between the rigid moieties. However, the derivatives prepared by click reactions have lamellar molecular packing similar to those of bis-acylureas forming multilayered nanosheet structures. PMID:21536305

Kim, Jong-Uk; Davis, Riju; Zentel, Rudolf

2011-07-15

393