Search results for "Macro"
showing 10 items of 3471 documents
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.
IR-spectroscopic studies of Zymomonas mobilis and levan precipitate
2002
Abstract The mid-infrared (mid-IR) absorption spectra of Zymomonas mobilis 113 “S” bacterial biomass grown in sucrose or glucose medium, and levan precipitate in the fingerprint region were studied. IR-qualitative and quantitative analyses were carried out. The principal component concentration changes in Z. mobilis biomass at different growth phases showed that protein concentration was higher in case of glucose-based medium, but the total carbohydrate concentration was higher if grown in sucrose-based medium. Low concentration of intracellular carbohydrates was a characteristic parameter of levan-producing Z. mobilis cells. It was shown that during 2-month storage of Z. mobilis inoculum i…
A green route to synthesize poly(lactic acid)-based macromonomers in scCO2 for biodegradable nanoparticle production
2014
Poly(lactic acid)-based macromonomers, aimed at biomedical applications and with well-defined average chain length, are produced through catalytic ring-opening polymerization of L,L-lactide co-initiated by a co-monomer bearing a double bond. Reactions have been carried out in supercritical carbon dioxide (scCO2) at different temperatures, ranging from 90 to 130 °C. The resulting oligomers have been characterized by different techniques (1H-NMR, 13CNMR, MALDI-TOF, ESI, GPC, FT-IR, TGA), which show that oligomers with narrower molecular weight distribution are produced at the lowest temperature. In addition, a significant reduction of the impact of the secondary reactions has been found at th…
Computer simulations of undercooled fluids and the glass transition
2000
Abstract Two model studies are presented that attempt to describe the static and dynamic properties of glass-forming fluids via molecular dynamics simulations: The first model is an atomistically realistic model of SiO 2 , the second model provides a coarse-grained description of polymer liquids, i.e., typical `fragile' glassformers, while SiO 2 is the prototype of a `strong glassformer'. For both models, attention is given to the questions as to which range of temperatures are properties in equilibrium, and whether such simulations can help to interpret experiments and/or check theoretical predictions. While in the simulation of SiO 2 using the potential of van Beest, Kramer and van Santen…
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…
Influence of Mannaproteins from Yeast on the Aroma Intensity of a Model Wine
1994
Abstract The influence of mannaproteins released from yeast cell walls during alcoholic fermentation on the volatility of aroma substances was investigated in a model wine. After the characterization of macromolecules (substrates), two techniques have been used to study the interactions with aroma compounds: headspace analysis and an equilibrium dialysis method. The assumed effects of these macromolecules from yeasts on the fixation of volatile compounds were demonstrated. The physico-chemical interactions between aroma substances and mannaproteins depended on the nature of volatile compounds. Protein concentration in substrates was an important factor in their binding capacity. The retenti…
Dynamics of macromolecules grafted in spherical brushes under good solvent conditions
2013
Spherical polymer brushes have a structure intermediate between star polymers and polymer brushes on flat substrates, and are important building blocks of polymer nanoparticles. Molecular dynamics simulations are presented for isolated spherical polymer brushes under good solvent conditions, varying the grafting density as well as the chain length, using a coarse-grained bead-spring model of flexible chains. We complement previous work on the static properties of the same model by analyzing the chain dynamics, studying the motions of monomers in relation to their position along the grafted chains, and extract suitable relaxation times. A qualitative discussion in terms of the Rouse model is…
Guest-Induced Folding and Self-Assembly of Conformationally Adaptive Macrocycles into Nanosheets and Nanotubes
2017
A conformationally adaptive macrocycle is presented, namely zorb[4]arene, which exists in multiple conformations in the uncomplexed state. The binding cavity of zorb[4]arene is concealed, either due to a collapsed conformation or by self-inclusion. The zorb[4]arene with long alkyl chains manifests itself with surprisingly low melting point and thus exist as an oil at room temperature. Binding of a guest molecule induces the folding and conformational rigidity of zorb[4]arene and leads to well-defined three-dimensional structures, which can further self-assemble into nanosheets or nanotubes upon solvent evaporation, depending on guest molecules and the conformations they can induce.
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.
Non-hydrolysable macromolecular constituents from outer walls of Chlorella fusca and Nanochlorum eucaryotum
1992
Abstract Many green microalgae possess a thin trilaminar outer wall (TLS) with a very high resistance to chemical degradation. TLS are known to play an important protective role in living cells. They are also selectively preserved during fossilization and thus provide a major contribution to the fossil organic matter of a number of sedimentary rocks. However, little information is available on TLS chemical structure. Examination of the TLS of Chlorella fusca (a lacustrine Chlorophycea) and of Nanochlorum eucaryotum (a recently discovered marine Chlorophycea) indicated that (i) they exhibit morphological features commonly observed in other green microalgae, (ii) their non-hydrolysable macrom…