The Experts below are selected from a list of 39 Experts worldwide ranked by ideXlab platform

H Kagan - One of the best experts on this subject based on the ideXlab platform.

  • modulation of lysyl oxidase activity toward peptidyl lysine by vicinal Dicarboxylic Amino Acid residues implications for collagen cross linking
    Journal of Biological Chemistry, 1994
    Co-Authors: Narasimhan Nagan, H Kagan
    Abstract:

    The substrate specificity of lysyl oxidase has been explored with synthetic oligopeptides. kcat/Km increased with increasing peptide length in Ac-(Gly)n-Lys-(Gly)n-CONH2 (n = 1-5). Using 11-mers as the standard peptide length, Glu immediately N-terminal to Lys increased kcat/Km 8.8-fold over that for the -Lys-Glu- sequence and 4.9-fold over the glutamate-free control. Kinetic constants were significantly less perturbed when Glu was 2 or more residues distant from Lys. Replacement of Glu in -Glu-Lys- with Gln significantly increased Km and lowered kcat/Km. Asp rather than Glu N-terminal to Lys decreased Km similar to that of the -Glu-Lys- 11-mer, although the kcat decreased considerably, indicating that lysyl oxidase responds to the side chain length of vicinal Asp or Glu at this position. -Asp-Glu-Lys- within an 11-mer was not oxidized, although this sequence is oxidized within the N-terminal telopeptide of the alpha 1(I) chain in type I collagen fibrils. Thus, lysyl oxidase exhibits distinct preferences for sequences vicinal to lysine. These results are discussed with respect to a model requiring collagen fibril formation prior to oxidation of lysine in collagen by lysyl oxidase.

  • modulation of lysyl oxidase activity toward peptidyl lysine by vicinal Dicarboxylic Amino Acid residues
    1994
    Co-Authors: Narasimhan Nagan, H Kagan
    Abstract:

    The substrate specificity of purified lysyl oxidase has been explored with synthetic, 11-mer oligopeptides. -Glu-Lys-in Ac-Glyn(Glu,Lys)Glym-NH2 was a more favorable substrate than the glutamate-free control peptide and considerably more favorable than the -Lys-Glu- sequence as well as sequences in which Glu was separated from Lys by intervening Gly residues. The kcat for the -Asp-Glu- sequence was markedly reduced from that of the -Glu-Lys- sequence, indicating that lysyl oxidase responds to the side chain length of vicinal Asp or Glu at this position. -Asp-Glu-Lys-within an 11-mer was not oxidized, although this sequence is oxidized within the N-telopeptide of the α 1(I) chain in type I collagen fibrils. Thus, lysyl oxidase exhibits distinct preferences for sequences vicinal to lysine. These results are discussed with respect to a model requiring collagen fibril formation prior to oxidation of lysine in collagen by lysyl oxidase.

Romain Bordes - One of the best experts on this subject based on the ideXlab platform.

  • interfacial and aggregation behavior of Dicarboxylic Amino Acid based surfactants in combination with a cationic surfactant
    Langmuir, 2019
    Co-Authors: Manas Barai, Romain Bordes, Manas Kumar Mandal, Atanu Karak, Anuttam Patra, Sudipta Dalai, Amiya Kumar Panda
    Abstract:

    The interfacial and micellization behavior of three Dicarboxylic Amino Acid-based anionic surfactants, abbreviated as AAS (N-dodecyl derivative of -Aminomalonate, -aspartate, and -glutamate) in combination with hexadecyltrimethylammonium bromide (HTAB) were investigated by surface tension, conductance, UV-vis absorption/emission spectroscopy, dynamic light scattering (DLS), and viscosity studies. Critical micelle concentration (CMC) values of the surfactant mixtures are significantly lower than the predicted values, indicating associative interaction between the components. Surface excess, limiting molecular area, surface pressure at the CMC, and Gibbs free energy indicate spontaneity of the micellization processes compared to the pure components. CMC values were also determined from the sigmoidal variation in the plot of micellar polarity and pyrene UV vis absorption/emission intensities with surfactant concentration. The aggregation number, determined by static fluorescence quenching method, increases with decreasing mole fraction of the AAS (alpha(AAS)), where the micelles are mainly dominated by the HTAB molecules. The size of the micelle increases with decreasing alpha(AAs), leading to the formation of larger and complex aggregates, as also supported by the viscosity studies. Micelles comprising 20-40 mol % AAS are highly viscous, in consonance with their sizes. Some of the mixed surfactant systems show unusual viscosity (shear thickening and increased viscosity with increasing temperature). Such mixed surfactant systems are considered to have potential in gel-based drug delivery and nanoparticle synthesis.

  • physical chemical characteristics of Dicarboxylic Amino Acid based surfactants
    Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2011
    Co-Authors: Romain Bordes, Krister Holmberg
    Abstract:

    Three Dicarboxylic Amino Acid-based surfactants, the disodium salts of dodecylAminomalonic Acid, dodecylaspartic Acid and dodecylglutamic Acid, having one, two and three carbon atoms, respectively between the carboxyl groups, have been studied with respect to solution behavior and adsorption at the air-water interface, as well as on a number of solid surfaces. The Dicarboxylic surfactants had 4-5 times higher CMC than the dodecylglycinate, which only has one carboxyl group. The role of the amide bond for the self-assembly process was assessed by comparing sodium dodecylglycinate with sodium dodecylsarcosinate. The former can build hydrogen bonds between adjacent molecules via the amide groups but the latter which has an N-methyl group, cannot, It was found that the ability to form intermolecular hydrogen bonds lead to tighter packing both at the air-water interface and in micelles. The CMC was not affected, however. Dodecylglutamate was found to be very calcium tolerant compared to the two other Dicarboxylic surfactants. This was attributed to differences in chelating calcium. Whereas dodecylAminomalonate and dodecylaspartate can form intramolecular chelates with calcium ions, dodecylglutamate prefers to form an intermolecular complex. Formation of an intermolecular complex leads to tight packing at the air-water interface and to very low surface tension values. The ability to form intramolecular chelates is advantageous for adsorption at calcium-containing surfaces, however. Whereas dodecylAminomalonate and, in particular, dodecylaspartate adsorb strongly on hydroxyapatite, dodecylglutamate shows very weak adsorption. On other surfaces, where there exist no specific interactions involving the surfactant headgroup, the three surfactants gave similar adsorption behavior.

Claudio Scazzocchio - One of the best experts on this subject based on the ideXlab platform.

  • agta the Dicarboxylic Amino Acid transporter of aspergillus nidulans is concertedly down regulated by exquisite sensitivity to nitrogen metabolite repression and ammonium elicited endocytosis
    Eukaryotic Cell, 2009
    Co-Authors: Angeliki Apostolaki, Zoi Erpapazoglou, Laura Harispe, Maria Billini, Panagiota Kafasla, Dimosthenis Kizis, Miguel A Penalva, Claudio Scazzocchio
    Abstract:

    We identified agtA, a gene that encodes the specific Dicarboxylic Amino Acid transporter of Aspergillus nidulans. The deletion of the gene resulted in loss of utilization of aspartate as a nitrogen source and of aspartate uptake, while not completely abolishing glutamate utilization. Kinetic constants showed that AgtA is a high-affinity Dicarboxylic Amino Acid transporter and are in agreement with those determined for a cognate transporter activity identified previously. The gene is extremely sensitive to nitrogen metabolite repression, depends on AreA for its expression, and is seemingly independent from specific induction. We showed that the localization of AgtA in the plasma membrane necessitates the ShrA protein and that an active process elicited by ammonium results in internalization and targeting of AgtA to the vacuole, followed by degradation. Thus, nitrogen metabolite repression and ammonium-promoted vacuolar degradation act in concert to downregulate Dicarboxylic Amino Acid transport activity.

Krister Holmberg - One of the best experts on this subject based on the ideXlab platform.

  • physical chemical characteristics of Dicarboxylic Amino Acid based surfactants
    Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2011
    Co-Authors: Romain Bordes, Krister Holmberg
    Abstract:

    Three Dicarboxylic Amino Acid-based surfactants, the disodium salts of dodecylAminomalonic Acid, dodecylaspartic Acid and dodecylglutamic Acid, having one, two and three carbon atoms, respectively between the carboxyl groups, have been studied with respect to solution behavior and adsorption at the air-water interface, as well as on a number of solid surfaces. The Dicarboxylic surfactants had 4-5 times higher CMC than the dodecylglycinate, which only has one carboxyl group. The role of the amide bond for the self-assembly process was assessed by comparing sodium dodecylglycinate with sodium dodecylsarcosinate. The former can build hydrogen bonds between adjacent molecules via the amide groups but the latter which has an N-methyl group, cannot, It was found that the ability to form intermolecular hydrogen bonds lead to tighter packing both at the air-water interface and in micelles. The CMC was not affected, however. Dodecylglutamate was found to be very calcium tolerant compared to the two other Dicarboxylic surfactants. This was attributed to differences in chelating calcium. Whereas dodecylAminomalonate and dodecylaspartate can form intramolecular chelates with calcium ions, dodecylglutamate prefers to form an intermolecular complex. Formation of an intermolecular complex leads to tight packing at the air-water interface and to very low surface tension values. The ability to form intramolecular chelates is advantageous for adsorption at calcium-containing surfaces, however. Whereas dodecylAminomalonate and, in particular, dodecylaspartate adsorb strongly on hydroxyapatite, dodecylglutamate shows very weak adsorption. On other surfaces, where there exist no specific interactions involving the surfactant headgroup, the three surfactants gave similar adsorption behavior.

Narasimhan Nagan - One of the best experts on this subject based on the ideXlab platform.

  • modulation of lysyl oxidase activity toward peptidyl lysine by vicinal Dicarboxylic Amino Acid residues implications for collagen cross linking
    Journal of Biological Chemistry, 1994
    Co-Authors: Narasimhan Nagan, H Kagan
    Abstract:

    The substrate specificity of lysyl oxidase has been explored with synthetic oligopeptides. kcat/Km increased with increasing peptide length in Ac-(Gly)n-Lys-(Gly)n-CONH2 (n = 1-5). Using 11-mers as the standard peptide length, Glu immediately N-terminal to Lys increased kcat/Km 8.8-fold over that for the -Lys-Glu- sequence and 4.9-fold over the glutamate-free control. Kinetic constants were significantly less perturbed when Glu was 2 or more residues distant from Lys. Replacement of Glu in -Glu-Lys- with Gln significantly increased Km and lowered kcat/Km. Asp rather than Glu N-terminal to Lys decreased Km similar to that of the -Glu-Lys- 11-mer, although the kcat decreased considerably, indicating that lysyl oxidase responds to the side chain length of vicinal Asp or Glu at this position. -Asp-Glu-Lys- within an 11-mer was not oxidized, although this sequence is oxidized within the N-terminal telopeptide of the alpha 1(I) chain in type I collagen fibrils. Thus, lysyl oxidase exhibits distinct preferences for sequences vicinal to lysine. These results are discussed with respect to a model requiring collagen fibril formation prior to oxidation of lysine in collagen by lysyl oxidase.

  • modulation of lysyl oxidase activity toward peptidyl lysine by vicinal Dicarboxylic Amino Acid residues
    1994
    Co-Authors: Narasimhan Nagan, H Kagan
    Abstract:

    The substrate specificity of purified lysyl oxidase has been explored with synthetic, 11-mer oligopeptides. -Glu-Lys-in Ac-Glyn(Glu,Lys)Glym-NH2 was a more favorable substrate than the glutamate-free control peptide and considerably more favorable than the -Lys-Glu- sequence as well as sequences in which Glu was separated from Lys by intervening Gly residues. The kcat for the -Asp-Glu- sequence was markedly reduced from that of the -Glu-Lys- sequence, indicating that lysyl oxidase responds to the side chain length of vicinal Asp or Glu at this position. -Asp-Glu-Lys-within an 11-mer was not oxidized, although this sequence is oxidized within the N-telopeptide of the α 1(I) chain in type I collagen fibrils. Thus, lysyl oxidase exhibits distinct preferences for sequences vicinal to lysine. These results are discussed with respect to a model requiring collagen fibril formation prior to oxidation of lysine in collagen by lysyl oxidase.