Search results for "Macromolecular Substance"
showing 10 items of 882 documents
The synthesis of nareielasie aldehyde and related lsocarbostyrils
1977
The synthesis of several isoearboslyrils is reported, including lorrnyl derivatives at (1-4, like nareiclasie aldehyde (I) and the homologous aldehyde (XV).
Conformational preferences of side-chain protected amino acid residues and their impact in peptide synthesis
1983
Using the host-guest technique, tentative scales for the helix-inducing power and the β-structure-forming potential of various side-chain protected amino acid residues in trifluoro-ethanol are established mainly by CD measurements. The generally lower tendency for β-structure formation of the host–guest peptides compared to that of the host peptide is discussed. The influence of these conformational features on the solubility of the peptides is also pointed out.
Dispersion of titanate nanotubes for nanomedicine: comparison of PEI and PEG nanohybrids.
2014
In the present study, we report the dispersion of titanate nanotubes (TiONts) via polymer grafting (PolyEthylene Glycol, PEG) or polymer adsorption (polyethylene imine, PEI) where different TiONts/polymer ratios have been investigated. The TiONts/PEI and TiONts/PEG nanohybrids were characterized by scanning and transmission electron microscopy as well as by zeta potential measurements in order to determine both their dispersion state and stability in water (at different pH for zetametry). The nature of the chemical bonds at the surface of these nanohybrids was investigated by Fourier-transformed infrared (FTIR) spectroscopy while the grafting densities of PEG on the nanotubes were quantifie…
ChemInform Abstract: Oligosaccharide Synthesis via Electrophile-Induced Activation of Glycosyl-N-allylcarbamates.
2010
Abstract Glycosyl-N-allyl carbamates, obtained by reaction of anomerically unprotected saccharides with allyl isocyanate, can be activated by an electrophile-induced cyclisation and reacted with glycosyl acceptors to form the corresponding oligosaccharides By this method the mucin core 2 trisaccharide2 has successfully been synthesized. Due to the mild glycosylation conditions even 1-O-acetyl protected glycosyl acceptors can be used. This was demonstrated in the synthesis of a 1,6-linked glucosyl trisaccharide whereby a reptitious glycosylation strategy could be applied. 1. Dedicated to the memory of Professor Akira Hasegawa.
Carotenoids and the Assembly of Light-harvesting Complexes
2006
Carotenoids are constitutive components of all light-harvesting complexes in plants and many such complexes in bacteria. In the crystal structures of several light-harvesting complexes, carotenoids are seen to span the lipid bilayer and connect components of the complex on both membrane surfaces and/or to mediate the interaction of transmembrane protein helices. This important stabilizing function suggests that these pigments are also actively involved in the assembly of light-harvesting complexes. Verification of this notion appears too ambitious a goal at present, as the question of how the pigment-protein complexes of the photosynthetic apparatus are assembled is still open. However, inf…
Chitin: A Structural Biopolysaccharide with Multiple Applications
2014
Chitin is a naturally occurring fibre-forming polymer that plays a protective role in many lower eukaryotes similar to that of cellulose in plants. Chemically it is a long-chain unbranched polysaccharide made of N-acetylglucosamine residues linked through β-1,4 covalent bonds; it is the second most abundant organic compound in nature, after cellulose. Taking into account the role played by chitin in different biological structures (i.e. fungal cell walls, insect peritrophic matrix, insect and crustacean cuticles, eggshells from nematodes, cyst wall of protozoa), its metabolism (biosynthesis and degradation) is essential for different morphogenetic events. Absent in vertebrates and plants, c…
Molecular characterization of the phenolic acid metabolism in the lactic acid bacteria Lactobacillus plantarum
2001
The lactic acid bacteria Lactobacillus plantarumdisplays substrate-inducible decar- boxylase activities on p-coumaric, caffeic and ferulic acids. Purification of the p-coumaric acid decarboxylase (PDC) was performed. Sequence of the N-terminal part of the PDC led to the cloning of the corresponding pdc gene. Expression of this gene in Escherichia colirevealed that PDC displayed a weak activity on ferulic acid, detectable in vitro in the presence of ammonium sulfate. Transcrip- tional studies of this gene in L. plantarum demonstrated that the pdc transcription is phenolic acid- dependent. A mutant deficient in the PDC activity, designated LPD1, was constructed to study phe- nolic acid altern…
1981
Elution curves on spherosil gels in pure and mixed eluents of poly(dimethylsiloxane), PDMS, and poly(methyl methacrylate), PMMA, as well as those of polystyrene, PS, just for comparison, have been determined. In a general way, PDMS elution volumers fit to those of PS, whereas PMMA elution curves shift to higher retention volumes. The differences in retention volumes between the different polymeric solutes have been interpreted in terms of differences in polymer-gel and polymer-solvent interactions. Hydrogen-bonding seems to be the main contribution to solute-substrate interactions.
Methyl-Substituted α-Cyclodextrin as Affinity Material for Storage, Separation, and Detection of Trichlorofluoromethane
2018
Abstract The severely ozone‐depleting trichlorofluoromethane is still appearing in several recycling processes or industrial applications. A simple and selective supramolecular complex formation of per‐methylated α‐cyclodextrin (1) with the highly volatile trichlorofluoromethane (2) is reported. This interaction moreover leads to thermally stable crystals. Per‐methylated α‐cyclodextrin is successfully exploited as a reversible and selective adsorption material for liquid and airborne trichlorofluoromethane as well as an affinity material for the chemical sensing and detection of this particular volatile organic component.
Polymerization of methyl and phenyl oxazoline initiated with alkyl chloroformates
2010
It has been shown that alkyl chloroformates are capable of initiating the polymerization of oxazolines. Esters itself initiate rather slowly and the polymerization proceeds via covalent growing species. Exchange of counter ions with triflate or iodide anions leads to faster initiation and higher reaction rates. The polymerization is of living character.