Increase In Molecular Size Research Articles

Molecular configuration of gelatin–water suspensions at low concentration

Direct assessment of gelatin molecular configuration has been difficult due the complexity of the molecule and limitations of analytical techniques. The objective of this work was the molecular characterization of bovine gelatin as a function of temperature, concentration and time. Diluted suspensions were prepared at different concentrations (7.5 × 10−5 to 1.5 g/l) and kept at temperatures above (S1) (40 °C) and below (S2) (5 °C) the gelling point as determined by Differential Scanning Calorimetry. Circular dichroism measurements showed the secondary structure of a polyproline II like spectra similar to native collagen at S1 and a denaturated configuration at S2 conditioning. Atomic Force Microscopy (AFM) at S1, using a HOPG substrate, showed single strands segments with two marked distributions in heights, ∼0.6 nm and ∼1.6 nm, indicating possible helical configurations even at high temperatures. At S2, AFM showed only one height distribution in the range of ∼0.9 nm but wider (0.3–1.6 nm range). At increasing gelatin concentration (12 g/l) and annealing time (48 h), a well-defined network was detected with narrow height distribution (∼1.0 nm) featuring aggregates and highly ordered structure zones. An analysis of gelatin strand interactions, showed a network linked by knots with a coordination number Z = 3 (strands) with a bond length of ∼50 nm. The gel network formation and aggregation was consistent with molecular size increase observed by Dynamic Light Scattering, showing variations in hydrodynamic dimensions from ∼10 nm (S1) to ∼100 nm (S2). This experimental approach has allowed to pinpoint differences in molecular configuration of gelatin, which may be applied in the study the structuring pathway of other biopolymers and the association kinetics during storage for a wide range of temperatures.

Glycosylation site-targeted PEGylation of glucose oxidase retains native enzymatic activity

Targeted PEGylation of glucose oxidase at its glycosylation sites was investigated to determine the effect on enzymatic activity, as well as the bioconjugate's potential in an optical biosensing assay. Methoxy-poly(ethylene glycol)-hydrazide (4.5kDa) was covalently coupled to periodate-oxidized glycosylation sites of glucose oxidase from Aspergillus niger. The bioconjugate was characterized using gel electrophoresis, liquid chromatography, mass spectrometry, and dynamic light scattering. Gel electrophoresis data showed that the PEGylation protocol resulted in a drastic increase (ca. 100kDa) in the apparent molecular mass of the protein subunit, with complete conversion to the bioconjugate; liquid chromatography data corroborated this large increase in molecular size. Mass spectrometry data proved that the extent of PEGylation was six poly(ethylene glycol) chains per glucose oxidase dimer. Dynamic light scattering data indicated the absence of higher-order oligomers in the PEGylated GOx sample. To assess stability, enzymatic activity assays were performed in triplicate at multiple time points over the course of 29 days in the absence of glucose, as well as before and after exposure to 5% w/v glucose for 24h. At a confidence level of 95%, the bioconjugate's performance was statistically equivalent to native glucose oxidase in terms of activity retention over the 29 day time period, as well as following the 24h glucose exposure. Finally, the bioconjugate was entrapped within a poly(2-hydroxyethyl methacrylate) hydrogel containing an oxygen-sensitive phosphor, and the construct was shown to respond approximately linearly with a 220±73% signal change (n=4, 95% confidence interval) over the physiologically-relevant glucose range (i.e., 0–400mg/dL); to our knowledge, this represents the first demonstration of PEGylated glucose oxidase incorporated into an optical biosensing assay.

Fluorescence quenching as an indicator of the conformational change of humic<br>acids

Humic acids as a water soluble fraction of humus play important role in the plant growth. Even though structure of humic acids is not clear, their spectroscopic properties can reveal us useful information. To investigate influence of humic acids reorganization, HPSEC fractionation at mild fractionation conditions has been carried out. Reconstruction of secondary chromatograms of separated fractions showed molecular size increase and increased response on fluorescence detector, although neither molecular size change nor significant absorbance increase was observed on UV-VIS detector. However, bigger aggregates, that didn't fluoresce in the unfractionated sample started to fluoresce. The reason for this behavior is not some change of spectral properties of a specific fraction, but a general fluorescence increase indicating humic acid reorganization. Therefore spectroscopic changes can be used as a tool for monitoring their reorganization, which might play an important role in nutrients soil plant mobility and should be studied in more details from that perspective.

Synthesis and Evaluation of 64Cu-Labeled Monomeric and Dimeric NGR Peptides for MicroPET Imaging of CD13 Receptor Expression

The NGR-containing peptides have been shown to bind specifically to CD13/aminopeptidase N (APN) receptor, one of the attractive tumor vasculature biomarkers. In this study, we evaluated (64)Cu-labeled monomeric and dimeric NGR peptides for microPET imaging of CD13 receptor expression in vivo. Western blot analysis and immunofluorescence staining were performed to identify CD13-positive and CD13-negative cell lines. NGR-containing peptides were conjugated with 1,4,7,10-tetraazadodecane-N,N',N″,N‴-tetraacetic acid (DOTA) and labeled with (64)Cu (t(1/2) = 12.7 h) in ammonium acetate buffer. The resulting monomeric ((64)Cu-DOTA-NGR1) and dimeric ((64)Cu-DOTA-NGR2) peptides were then subjected to in vitro stability, cell uptake and efflux, small animal micorPET, and biodistribution studies. In vitro studies demonstrated that CD13 receptors are overexpressed in human fibrosarcoma HT-1080 cells and negative in human colon adenocarcinoma HT-29 cells. The binding affinity of (64)Cu-DOTA-NGR2 to HT-1080 cells was measured to be within low nanomolar range and about 2-fold higher than that of (64)Cu-DOTA-NGR1. For small animal microPET studies, (64)Cu-DOTA-NGR2 displayed more favorable in vivo performance in terms of higher tumor uptake and slower tumor washout in CD13-positive HT-1080 tumor xenografts as compared to (64)Cu-DOTA-NGR1. As expected, significantly lower tumor uptake and poorer tumor/normal organ contrast were observed for both (64)Cu-DOTA-NGR1 and (64)Cu-DOTA-NGR2 in CD13-negative HT-29 tumor xenografts in comparison with those in the HT-1080 tumor xenografts. The CD13-specific tumor activity accumulation of both (64)Cu-DOTA-NGR1 and (64)Cu-DOTA-NGR2 was further demonstrated by significant reduction of tumor uptake in HT-1080 tumor xenografts with a coinjected blocking dose of cyclic NGR peptide [c(CNGRC)]. The biodistribution results were consistent with the quantitative analysis of microPET imaging. We concluded that both (64)Cu-DOTA-NGR1 and (64)Cu-DOTA-NGR2 have good and specific tumor uptake in CD13-positive HT-1080 tumor xenografts. (64)Cu-DOTA-NGR2 showed higher tumor uptake and better tumor retention than (64)Cu-DOTA-NGR1, presumably due to bivalency effect and increase in apparent molecular size. (64)Cu-DOTA-NGR2 is a promising PET probe for noninvasive detection of CD13 receptor expression in vivo.

Effects of Enteromyxum leei (Myxozoa) infection on gilthead sea bream (Sparus aurata) (Teleostei) intestinal mucus: glycoprotein profile and bacterial adhesion

The intestinal myxosporean parasite Enteromyxum leei causes severe desquamative enteritis in gilthead sea bream (Sparus aurata) (Teleostei) that impairs nutrient absorption causing anorexia and cachexia. In fish, as in terrestrial vertebrates, intestinal goblet cells are responsible for the adherent mucus secretion overlying epithelial cells, which constitutes a first line of innate immune defense against offending microorganisms but serves also as substrate and nutrient source for the commensal microflora. The secreted intestinal mucus of parasitized (n = 6) and unexposed (n = 8) gilthead sea bream was isolated, concentrated, and subjected to downward gel chromatography. Carbohydrate and protein contents (via PAS and Bradford stainings), terminal glycosylation (via lectin ELISA), and Aeromonas hydrophila and Vibrio alginolyticus adhesion were analyzed for the isolated intestinal mucins. Parasitized fish, compared with unexposed fish, presented intestinal mucus mucins with a lower glycoprotein content and glycosylation degree at the anterior and middle intestine, whereas both glycoprotein content and glycosylation degree increased at the posterior intestine section, though only significantly for the total carbohydrate content. Additionally, a slight molecular size increase was detected in the mucin glycoproteins of parasitized fish. Terminal glycosylation of the mucus glycoproteins in parasitized fish pointed to an immature mucin secretion (N-acetyl-α-D-galactosamine increase, α-L-fucose, and neuraminic-acid-α-2-6-galactose reduction). Bacterial adhesion to large-sized mucus glycoproteins (>2,000 kDa) of parasitized fish was significantly lower than in unexposed fish.

Dispersion polymerization of acrylamide with water‐soluble chitosan as the stabilizer

AbstractA cationic polyelectrolyte of P (CMTC‐AM‐DMC) was synthesized by dispersion polymerization in aqueous solution of ammonium chloride, with acrylamide and dimethylaminoethyl methacrylate methyl chloride as main raw materials. N‐carboxymethylthioureidochitosan was used as both the reactant and the stabilizer, and 2,2′‐azobis (2‐amidinopropane) dihydrochloride (V‐50) as the initiator. The effects of the major reaction variables such as the concentration of inorganic salt and initiator, temperature, reaction time, and pH on the polymerization were discussed in this article. The optimal conditions of the polymerization were determined by orthogonal tests. The results showed that an increase in salt concentration resulted in an increase of molecular weight and particle size and a decrease of apparent viscosity, while when salt concentration was up to 23.9%, apparent viscosity was slightly higher than others. Molecular weight, particle size, and apparent viscosity all decreased with the increase of initiator. The apparent viscosity, molecular weight, and particle size would decrease with pH, and the product would be coagulated when pH > 7. Temperature influenced the characteristic a lot. Overall conversion was less dependent on these factors except for the temperature. Molecular weight and overall conversion increased gradually with the time, and the monomers could react completely at about 5–7 h. Flocculation occurred with 13% of salt concentration, 0.005% of initiator, and pH > 7. The optimal reaction conditions for obtaining a stable aqueous dispersion were 22.3% for ammonium chloride, 0.007% for initiator, react under 55 °C for 5 h at pH = 4. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

DFT calculations of structures, 13C NMR chemical shifts, and Raman RBM mode of simple models of small‐diameter zigzag (4,0) carboxylated single‐walled carbon nanotubes

Linearly conjugated benzene rings (acenes), belt-shaped molecules (cyclic acenes), and models of single-walled carbon nanotubes (SWCNTs) with one carboxylic group at the open end were fully optimized at the B3LYP/6-31G* level of theory. These models were selected to obtain some insight into the nuclear isotropic changes resulting from systematically increasing the basic building units of open-tip-monocarboxylated SWCNTs. In addition, the position of radial breathing mode (RBM), empirically correlated with the SWCNT diameter, was directly related with the radius of model cyclic acene rings. A regular convergence of selected structural, NMR, and Raman parameters with the molecular system size increase was observed, and a simple two-parameter mathematical formula enabled their estimation in infinity. The predicted (13) C NMR chemical shifts of carbon atoms close to the substituted rim of carboxylated models of zigzag (4,0) SWCNTs differed significantly from the pristine nanotubes.

Molecular Design Properties of OxyVita Hemoglobin, a New Generation Therapeutic Oxygen Carrier: A Review.

OxyVita Hb is a new generation hemoglobin based oxygen carrier (HBOC) produced through modification of a zero-linked polymerization mechanism using activators which incorporate cross-linked bovine tetramer hemoglobin into “super-polymeric” macromolecules (Average molecular weight = 17 MDa) for the purpose of oxygen delivery when whole blood or packed red cells are not available. This molecular design approach was generated in order to address several fundamental biochemical and physiological weaknesses of previous generations of HBOCs. Observation during pre-clinical and clinical studies provided evidence that these early generation acellular HBOCs were directly associated with loss of retention within the circulatory system, extravasation across endothelial tissue membranes due to their small molecular size leading to arterial and venous vasoconstriction with coupled increases in mean arterial pressure (MAP). The inherent increase in molecular size and structural stability of the OxyVita Hb is a direct response to addressing these serious weaknesses that have occurred during the evolution of HBOC development within the past two decades. The nature of the zero-linked synthetic route eliminates any chemical linkers remaining in the product, eliminating side reaction concerns, such as reversibility and decomposition due to weak chemical bonds, dependency on temperature and pressure, and residual toxicity

Triazole, Benzotriazole, and Naphthotriazole as Copper Corrosion Inhibitors: I. Molecular Electronic and Adsorption Properties

The gas-phase adsorption of 1,2,3-triazole, benzotriazole, and naphthotriazole-considered as corrosion inhibitors-on copper surfaces was studied and characterized using density functional theory (DFT) calculations. We find that the molecule-surface bond strength increases with increasing molecular size, thus following the sequence: triazole<benzotriazole<naphthotriazole. This trend is explained in terms of molecular electronegativity and chemical hardness, which decrease monotonously as the molecular size increases. While the electronegativity of triazole is almost degenerate with the work function of Cu(111) surface, the electronegativity of larger acenotriazoles is smaller. The difference in electronegativity between the Cu(111) and the acenotriazoles thus increases with increasing the molecular size, which, together with decreasing the molecular hardness, results in larger molecule-to-metal electron charge transfer and stronger molecule-surface bonds.

Interaction of Actin with Carcinoembryonic Antigen-related Cell Adhesion Molecule 1 (CEACAM1) Receptor in Liposomes Is Ca2+- and Phospholipid-dependent

The regulation of binding of G-actin to cytoplasmic domains of cell surface receptors is a common mechanism to control diverse biological processes. To model the regulation of G-actin binding to a cell surface receptor we used the cell-cell adhesion molecule carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1-S) in which G-actin binds to its short cytoplasmic domain (12 amino acids; Chen, C. J., Kirshner, J., Sherman, M. A., Hu, W., Nguyen, T., and Shively, J. E. (2007) J. Biol. Chem. 282, 5749-5760). A liposome model system demonstrates that G-actin binds to the cytosolic domain peptide of CEACAM1-S in the presence of negatively charged palmitoyl-oleoyl phosphatidylserine (POPS) liposomes and Ca(2+). In contrast, no binding of G-actin was observed in palmitoyl-oleoyl phosphatidylcholine (POPC) liposomes or when a key residue in the peptide, Phe-454, is replaced with Ala. Molecular Dynamics simulations on CEACAM1-S in an asymmetric phospholipid bilayer show migration of Ca(2+) ions to the lipid leaflet containing POPS and reveal two conformations for Phe-454 explaining the reversible availability of this residue for G-actin binding. NMR transverse relaxation optimized spectroscopic analysis of (13)C-labeled Phe-454 CEACAM1-S peptide in liposomes plus actin further confirmed the existence of two peptide conformers and the Ca(2+) dependence of actin binding. These findings explain how a receptor with a short cytoplasmic domain can recruit a cytosolic protein in a phospholipid and Ca(2+)-specific manner. In addition, this model system provides a powerful approach that can be applied to study other membrane protein interactions with their cytosolic targets.

Assessment of Gaussian-4 theory for the computation of enthalpies of formation of large organic molecules

Gas-phase enthalpies of formation of 122 relatively large organic molecules with up to 15 non-hydrogen atoms have been calculated at the Gaussian-4 (G4) level of theory using the atomization reaction procedure. The calculated values were compared with experimental data published mainly last years. Particular attention has been given to nitro compounds and nitrogen, oxygen, and sulfur containing heterocyclic compounds. The expected accumulation of systematic errors as the molecular size increases was not observed with increasing the number of non-hydrogen atoms from 6 to 15. The largest mean absolute deviation between experimental and G4 enthalpies of formation, 10.7 kJ/mol, was revealed for nitro compounds. All theoretical values for nitro compounds were underestimated by 5–15 kJ/mol. The best agreement with experiment with mean absolute deviation of 4.5 kJ/mol was observed for compounds which types were widely presented in the original test set of G4 method. The mean absolute deviations for nitrogen heterocycles (6.8 kJ/mol) and oxygen and sulfur heterocycles (9.1 kJ/mol) are noticeably larger. Experimental enthalpies of formation of four compounds (N,N-dinitromethanamine, 2,3,5,6-tetrachloronitrobenzene, 2-methyl-2H-tetrazole, and proline) were suggested to be unreliable from comparison with the G4 values calculated from atomization energies and isodesmic reactions.

Abstract 5361: DNA damage by platinum-based drugs induces p21-dependent recruitment of PCNA as a homotrimer into the inhibited G1-phase CDK complex

Abstract DNA damage results in activation of cell cycle checkpoints and cell cycle arrest as a result of inhibition of cyclin-dependent kinases (CDK). In G1 phase, checkpoint activation is often associated with inhibition of CDK4/cyclin D1 and CDK2/cyclin E activities, usually by p21 in a p53-dependent manner. Our investigations in A2780 ovarian tumor cells with cisplatin and 1R,2R-diaminocyclohexane-(trans-diacetato)(dichloro)-platinum(IV) (DAP), a platinum analog that circumvents cisplatin resistance, demonstrated that both agents activated the p53-p21 pathway, which inhibited G1-phase CDK4 and CDK2 kinases, beginning at ∼18 h after drug treatment. However, biochemical analysis of the inhibited complex demonstrated an increase in size by ∼100-150 kDa, which was not consistent with binding of p21 alone and the anticipated stoichiometry of 1 for CDK:p21. In order to account for the p21-dependent increase in the size of the CDK complex, we undertook large-scale immunoprecipitation with antibodies to cyclin D (for the CDK4 complex) or cyclin E (for the CDK2 complex) following DAP treatment, and analyzed the inhibited complex by mass spectrometry for additional recruited proteins. This analysis revealed only one additional protein, namely PCNA, in the inhibited CDK2 and CDK4 complex. As confirmation of p21-dependence, immunodepletion of p21 in boiled cell lysates from DAP-treated cells abolished the binding of PCNA to the CDK complex in a cell-free binding assay. Similar p27 depletion did not prevent the binding of PCNA to the complex. However, PCNA binding with p21 at a stocihiometry of 1 was insufficient to account for the increase in molecular size of the inhibited CDK complex, and it was likely that PCNA was present in its trimeric state. This was confirmed by employing mutant PCNA (Y114A) which could not form the homotrimer and, consequently, was unable to bind to p21 and become recruited into the CDK complex. Moreover, inhibiting the binding of PCNA to p21 did not prevent p21 from inhibiting CDK2, and this indicated that PCNA is not vital for p21-dependent inhibition of kinase activity. On the other hand, knockdown of PCNA by siRNA in A2780 cells potentiated the cytotoxicity of DAP, whereas p21 knockout in HCT-116(p21-/-) cells decreased the sensitivity to this agent. Taken together, our data demonstrate that p21-dependent recruitment of PCNA as a homotrimer substantially increases the molecular size of the CDK complex, but whereas PCNA recruitment does not contribute to p21-dependent inhibition of the kinase, it may attenuate the effect of p21 on drug-induced cytotoxicity. (Supported by NCI RO1 CA127263). Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 5361. doi:10.1158/1538-7445.AM2011-5361

The effect of hydrothermal treatment on column performance for monolithic silica capillary columns

Monolithic silica capillary columns with i.d. 100 μm and monolithic silica rods were prepared with tetramethoxysilane (TMOS) or a mixture of TMOS and metyltrimethoxysilane (MTMS) using different hydrothermal treatments at T = 80 °C or 120 °C. Nitrogen physisorption was applied for the pore characterization of the rods and inverse size exclusion chromatography (ISEC) for that of the capillary columns. Using nitrogen physisorption, it was shown change of pore size and surface area corresponds to that of hydrothermal treatment and silica precursor. The results from ISEC agreed well with those from nitrogen physisorption regarding the pore size distribution (PSD). In addition, the retention factors for hexylbenzene with the ODS-modified capillary columns in methanol/water = 80/20 at T = 30 °C could also support the results from nitrogen physisorption. Furthermore, column efficiency for the columns was evaluated with alkylbenzenes and three kinds of peptides, leucine-enkephalin, angiotensin II, and insulin. Column efficiency for alkylbenzenes was similar independently of the hydrothermal treatment at T = 120 °C. Even for TMOS columns, there was no significant difference in column efficiency for the peptides despite the difference in hydrothermal treatment. In contrast, for hybrid columns, it was possible to confirm the effect on hydrothermal treatment at T = 120 °C resulting in a different column efficiency, especially for insulin. This difference supports the results from both nitrogen physisorption and ISEC, showing the presence of more small pores of ca. 3–6 nm for a hybrid silica without hydrothermal treatment at T = 120 °C. Consequently, the results suggest that hydrothermal treatment for a hybrid column with higher temperature or longer time is necessary, compared to that for a TMOS column, to provide higher column efficiency with increase in molecular size of solute.

Research on Genetic Algorithms based on Real Coded and Data Information for Global Optimization

The genetic algorithm is recently developed real number coding used in challenging problems finding the lowest energy structure of the same group of atomic interaction through the wells potential. Find the global optimal this function is difficult, because it has a large number of local extremum, molecular size increase exponentially. The results of the cluster contain 15 atoms, and obtained. The results show the excellent performance of newly developed real number coding genetic algorithm, the earlier published the results.

Structural Analysis of Hepta-, Nona-, and Undeca-Cyclic Aromatic Hydrocarbons by NMR Spectroscopy

Large condensed polycyclic aromatic hydrocarbons (LCPAHs) generally have distorted structures due to steric repulsion between neighboring hydrogen atoms. The distortion may influence their physicochemical properties such as electric conductivity, photoconductivity, and photochromism. Accordingly we have synthesized LCPAHs and analyzed their structure. In the present study, we synthesized an undecacyclic aromatic compound, dibenzo[a,rst]-dinaphtho[2,1,8-klm:1′,2′-o]pentaphene (DDPP) and determined the structure by use of NMR spectroscopy. To assign the 1H- and 13C-NMR chemical shifts completely, we used the HMQC-TOCSY (Heteronuclear Multiple Quantum Coherence-Total Correlation SpectroscopY) method in which the original proton-carbon correlation is relayed to neighboring protons in the same spin-system. Furthermore, we compared the chemical shifts (δs) of the heptacyclic aromatic hydrocarbon, peropyrene, the nonacyclic, violanthrene B (VEB), and the undecacyclic, DDPP, and investigated correlations between their local structure and δs. For the protons in the bay region, the averaged δs decrease as molecular size increases: 9.23 ppm (hepta-) > 9.07 ppm (nona-) > 8.77 ppm (undeca-). Similar change in the δs is also found for the protons in the cove region: 9.37 ppm (nona-) > 8.81 ppm (undeca-). Thus, it is noted that the averaged δs for the protons in the cove region become downfield than those for the protons in the bay region. The findings are explained in terms of the anisotropic effect of the local magnetic field of benzene rings.

Bifunctional fusion proteins of the human engineered antibody domain m36 with human soluble CD4 are potent inhibitors of diverse HIV-1 isolates

Currently used antiretroviral therapy is highly successful but there is still a need for new effective and safe prophylactics and therapeutics. We have previously identified and characterized a human engineered antibody domain (eAd), m36, which exhibits potent broadly neutralizing activity against HIV-1 by targeting a highly conserved CD4 binding-induced (CD4i) structure on the viral envelope glycoprotein (Env) gp120. m36 has very small size (∼15 kDa) but is highly specific and is likely to be safe in long-term use thus representing a novel class of potentially promising HIV-1 inhibitors. Major problems with the development of m36 as a candidate therapeutic are possible short serum half life and lack of effector functions that could be important for effective protection in vivo. Fusion of m36 to human IgG1 Fc resulted in dramatically diminished neutralization potency most likely due to the sterically restricted nature of the m36 epitope that limits access of large molecules. To confer effector functions and simultaneously increase the potency, we first matured m36 by panning and screening a mutant library for mutants with increased binding to gp120. We next fused m36 and its mutants with the first two domains (soluble CD4, sCD4) of the human CD4 using a polypeptide linker. Our results showed that the selected m36 mutants and the sCD4 fusion proteins exhibited more potent antiviral activities than m36. The m36-sCD4 fusion proteins with human IgG1 Fc showed even higher potency likely due to their bivalency and increased avidity although with a greater increase in molecular size. Our data suggest that m36 derivatives are promising HIV-1 candidate therapeutics and tools to study highly conserved gp120 structures with implications for understanding mechanisms of entry and design of vaccine immunogens and small-molecule inhibitors.

Arabidopsis thaliana seed germination and early seedling growth are inhibited by monoethanolamine salts of para-halogenated benzoic acids

In spite of the simplicity of its molecules, the complex effects of benzoic acids on the regulation of plant growth are an increasingly attractive field of research to chemists and biologists. Halide substituted benzoic acids offer an excellent opportunity to explore the effect of electron withdrawing substituents (fluoro-, chloro-, bromo- and iodo-) on the response of plant growth stage. Under normal physiological conditions, benzoic acids are ionized molecules that exhibit low solubility in water. Monoethanolamine, a natural alkanolamine, was used to generate salts of monoethanolamine of halogenated para-substituted benzoic acids, new compounds with biological activity. This study reports on the biological effects of these substances at different concentrations on Arabidopsis thaliana seed germination and early seedling growth. Seed germination at 22°C, in a vertical position, under a photoperiod of 16 h light and 8 h darkness, was variable depending on the concentration of the compounds applied. Final germination percentages were similar for all treatments and control at 0.05 mM and 0.1 mM (exception p-Br BA and p-I MEASPBA). No germination occurred when seeds were treated with more than 0.5 mM. The results also revealed that the primary root length and the number of secondary roots are reduced in a concentration-dependent manner and also in relation to increasing atomic size of the substituents (F < Cl < Br < I). It is concluded that uptake rates of benzoic acid anions by roots decrease with a decrease in hydrophilic character of the anion and with an increase in molecular size.

An effective Hamiltonian survey of the anharmonic vibrational state space of SCCl2 up to the dissociation energy

We survey about 3.5 million feature states in the anharmonic state space of SCCl(2) to answer three questions: how sharp is the threshold for intramolecular vibrational energy redistribution (IVR), how do specific resonances and regions of state space contribute to the threshold, and how many undiluted spectral features (or localized eigenstates) persist as energy increases? As quantitative measures we use the dilution factor sigma, Heller's F, and e, which describes how close to the edge of state space a feature lies. We find that an IVR threshold can be identified and lies between 250 and 300 THz. The threshold is softened because different resonances act at different energies in different parts of state space. According to our calculation, about 1 in 10(3) feature states remains undiluted near the dissociation limit of SCCl(2). This fraction matches the number of sharp spectral features observed recently by experiment when symmetry and Franck-Condon factors are taken into account, and it is in agreement with an analytical model that predicts an increasing fraction of undiluted features as molecular size increases.

Feasibility of nanofiltration for the removal of endocrine disrupting compounds

Surface water can contain significant amounts of endocrine disrupting compounds (EDCs) originating mainly from effluent of households, sewage treatment plants and farming activities. In this work the feasibility of nanofiltration for the removal of EDCs is evaluated. Estradiol retentions of, respectively, 75% (UTC-20) and 85% (NF270) and estrone retention of 83% (UTC-20) and 65% (NF270) were obtained. These retentions were lower than expected based on the MWCO and also lower than the retention of salicine, with a comparable molecular weight but more hydrophilic. However, the differences in retention between estrone, estradiol and salicine are less than those between compounds with a molecular weight below the MWCO of both membranes. This results from a decreasing influence of hydrophobicity on retention as the molecular size increases compared to the MWCO. An economical evaluation based on the obtained results showed that the implementation of nanofiltration in the drinking water process is not economically feasible for year capacities of 3.5 and 4.5Mm 3/year and peak factors of 1.3 or 1.4 using a water price of 0.50 €/m 3. This price should be more than double in order to obtain a NPV of zero at an interest of 10% over a period of 10 years. Finally, it was found that a 50% decrease of membrane prices has barely an influence on the installation costs as pay back time and NPV value were nearly the same for the different alternatives.

Effect of UVR on Lake Water and Macrophyte Leachates in Shallow Andean‐Patagonian Lakes: Bacterial Response to Changes in Optical Features

The aim of this study was to identify bacterial responses in two shallow lakes from Patagonia to UV-irradiated dissolved organic matter (DOM) coming from different sources. We carried out laboratory experiments in which natural lake water and Potamogeton linguatus leachates were irradiated (UVA-340 fluorescent tubes Q-Panel) or kept in darkness. Natural bacterial assemblages were then incubated in four treatments: natural lake water, irradiated lake water, macrophyte leachate and irradiated macrophyte leachate. We estimated bacterial abundance, composition and activity, and changes in the optical features of DOM. Our results showed that the addition of leachates caused an increase in the DOM mean molecular size. After UV exposure, a high bacterial activity was observed in lake water treatments. On the contrary, carbon uptake by bacteria was reduced in the irradiated leachate treatment. The degree of aromatization in the leachate treatments increased and thus may contribute to a dissolved carbon less available for bacterial activity. Regarding the bacteria assemblage we observed that beta-Proteobacteria outcompete the other groups in the leachate treatments, this group being more efficient at utilizing the high molecular weight DOM. These results highlight the importance of UVR interacting with different DOM sources in bacteria responses of shallow lakes.