Saccharose | EPFL Graph Search

vignette|Cristaux de sucre blanc. Le saccharose, saccarose ou sucrose est un sucre à la saveur douce. Extrait de certaines plantes, principalement de la canne à sucre et de la betterave sucrière, il est très largement utilisé pour l'alimentation humaine. Il s'agit d'un diholoside constitué de glucose et de fructose dont le nom normalisé est « α-D-glucopyranosyl-(1↔2)-β-D-fructofuranoside », couramment abrégé en « Glc-Fru ». En anglais, il est appelé sucrose, d'où l'abréviation « Suc » parfois rencontrée dans la littérature pour désigner ce composé. Les glucides, et notamment le saccharose, étaient jadis appelés hydrates de carbone en raison d'une ancienne expérience de déshydratation du sucre blanc par de l'acide sulfurique concentré, au cours de laquelle le saccharose, de formule brute , était décomposé en eau et en noir de carbone. On en avait déduit de manière erronée que la formule du saccharose pouvait s'écrire , correspondant à un hydrate de carbone. Cette appellation est deve

Preparation and characterization of Poly(Ethylene Glycol)/gamma-CD Polyrotaxanes using beta-CD derivatives as a capping reagent

Blaise Tardy

As living systems understanding got better, as life could be modeled in a batch, using immortalized cells, researches in fundamental sciences found startling applications of advanced techniques on living systems. As the biomaterial field developed various molecules were found to have very interesting applications on living systems. Polyrotaxane is one of these particularly interesting molecules. It is a non covalently bonded molecular necklace produced by the threading of cyclic molecules onto a linear polymer in order to form a pseudopolyrotaxane, the capping of this pseudopolyrotaxane to avoid de-threading of the cyclic compounds forms a polyrotaxane. This compound has already proven its versatility through various application including drug delivery systems, DNA delivery agent, molecular machine, hydrogel building block, resin stabilizer and a lot more. Cyclodextrins (CDs) and Polyester are known to form a pseudopolyrotaxane. CDs are composed of 6 to 8 glucopyranose forming a toroid shaped molecule that can contain different molecules depending on the solvent, experimental conditions and the number of sugar subunits. In this project an attempt has been made to synthesize a special type of polyrotaxane that would allow the whole complex to bare a higher degree of freedom compared to the ones currently documented. In order to do so the widest CD has been used (Gamma-CD, GCD), the chosen host has been poly(ethylene glycol) (PEG) chains of varying molecular weight and the capping reagent used was beta-CD derivatives. Furthermore since current literature hasn't documented it so well and its properties are essential to this study, some more characterization of the PEG/GCD pseudopolyrotaxane has been made. The Macromolecules have been characterized by maldi tof mass spectroscopy(MALDI-T-MS), electro spray ionization (ESI) mass detection, X-ray diffraction(XRD), gel phase chromatography (GPC) and liquid Nuclear magnetic resonance (NMR). The beta CD and poly(ethylene glycol) derivatives have been characterized using Fourier transform infra red spectroscopy (FTIR), NMR, MALDI-Toff MS, ESI and thin layer Chromatography (TLC)

2009

Continent-specific intake fractions and characterization factors for toxic emissions: Does it make a difference?

David Rochat

Goal and Scope. This paper aims to develop continental characterization factors for the human toxicity impacts of emissions released to air in different continents and to analyze under which conditions this spatial distinction makes a significant difference compared to generic characterization factors.

Ecomed, Springer2006

Influences of Dilute Organic Adsorbates on the Hydration of Low-Surface-Area Silicates

Bradley Floyd Chmelka, David Lyndon Emsley, David Benjamin Roger Antoine Gajan, Aaron James Rossini

Competitive adsorption of dilute quantities of certain organic molecules and water at silicate surfaces strongly influence the rates of silicate dissolution, hydration, and crystallization. Here, we determine the molecular-level structures, compositions, and site-specific interactions of adsorbed organic molecules at low absolute bulk concentrations on heterogeneous silicate particle surfaces at early stages of hydration. Specifically, dilute quantities (similar to 0.1% by weight of solids) of the disaccharide sucrose or industrially important phosphonic acid species slow dramatically the hydration of low-surface-area (similar to 1 m(2)/g) silicate particles. Here, the physicochemically distinct adsorption interactions of these organic species are established by using dynamic nuclear polarization (DNP) surface-enhanced solid-state NMR techniques. These measurements provide significantly improved signal sensitivity for near-surface species that is crucial for the detection and analysis of dilute adsorbed organic molecules and silicate species on low-surface-area particles, which until now have been infeasible to characterize. DNP-enhanced 2D Si-29{H-1}, C-13{H-1}, and P-31{H-1} heteronuclear correlation and 1D Si-29{C-13} rotational-echo double-resonance NMR measurements establish hydrogen-bond-mediated adsorption of sucrose at distinct nonhydrated and hydrated silicate surface sites and electrostatic interactions with surface Ca2+ cations. By comparison, phosphonic acid molecules are found to adsorb electrostatically at or near cationic calcium surface sites to form Ca(2+)phosphonate complexes. Although dilute quantities of both types of organic molecules effectively inhibit hydration, they do so by adsorbing in distinct ways that depend on their specific architectures and physicochemical interactions. The results demonstrate the feasibility of using DNP-enhanced NMR techniques to measure and assess dilute adsorbed molecules and their molecular interactions on low-surface-area materials, notably for compositions that are industrially relevant.