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Abstract  

It has been suggested that in ‘dry’ protein-trehalose-water systems, water-mediated hydrogen bond network, whose strength increases by drying, anchors the protein to its surroundings. To further characterize this effect, we performed a DSC study on low-water myoglobin-trehalose systems. The denaturation temperature resulted to increase by decreasing hydration, and linearly correlated to the glass transition temperature of both the ternary protein-water-trehalose and the binary water-trehalose systems. Further measurements are being performed to investigate eventual differences among different saccharides.

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Abstract  

Precipitation of trehalose dihydrate in water is observed at room temperature for trehalose concentrations higher than 47.5%w/w. Direct observations of crystal melting in water and measures of the solution density determine the thermal variations of trehalose saturationS(T) (mM) in water: ln(S(T))=ln(0.1223)-(1330/T) withR 2 =0.9982. The glass transition (Tg) curve measured by DSC is lower at low concentrations and higher at high concentrations than previously reported.T g is also measured as a function of the cooling/warming rates. Analysis of specific heat changes atT g and associated activation energy leads to identify a most stable glassy state around the second eutectic concentration.

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Trehalose dihydrate, on careful dehydration below its fusion point, retains its original crystal facets but becomes X-ray amorphous, an unusual example of direct crystal-to-glass transformation. From DSC studies, the glass obtained by this route seems to be of abnormally low enthalpy, but after an initial scan, the normal form of glass transition is exhibited, withT g=115‡C, a higher value than previously reported. We give a preliminary thermal and mechanical characterization of this material and find it to be a very fragile liquid. The highT g is shown to rationalize the exceptionally high water content of the trehalose+water solution that vitrifies at ambient temperature (i.e.T g=298 K), and hence helps explain its use by Nature as a desiccation protectant. The spontaneous vitrification of crystalline materials during desolvation is related to the phenomenology of pressure-induced or decompression-induced vitrification of crystals via the concept of limiting metastability.

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Abstract  

The phase transitions of α,α-trehalose dihydrate (T h) were investigated by either differential thermal analysis (DTA) with an in-house apparatus of variable-pressure type equipped with an open sample holder or commercially available TG (thermal gravimetry)-DTA apparatus for comparison under the same experimental conditions as to the heating rate (2°C min−1), the type of pan (open), and the particle size of T h (63 μm). The former DTA measurements were carried out under five different total pressures, 101, 75, 61, 48 and 35 kPa, which provided quite helpful information necessary for confirmative assignments of the endothermic peaks due to either melting or dehydration of T h. The usage of largely different amount of T h, 126 and 14 mg for the DTA and TG-DTA measurements respectively, led to their different DTA traces, showing that there were largely different extents of the influence by the measured sample surface exposed to the surrounding atmosphere on its dehydration behavior. In addition the high thermal sensitivity achieved with such mass of T h gave rise to an interesting discovery of an unidentified thermal event at 92°C prior to either melting or dehydration of T h.

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constitute about 90% of water-soluble proteins of the lens and contribute to the transparency and refractive properties by forming a uniform concentration gradient in the lens [ 3 ]. Trehalose, a disaccharide formed by alpha-1,1 linkage of two d

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Abstract  

As trehalose is a glucose font and also an additive in food, a new reliable method for trehalose determination is proposed. The analytical method uses an isothermal microcalorimeter, directly relates the analyte concentration with the heat variation of the enzymatic decomposition of trehalose into two glucose molecules. The enzymatic reaction is performed inside the calorimeter in the presence of trehalase enzyme immobilized on amino activated glass beads. Through the calibration curve, the trehalose quantity in some food samples (mushrooms and honey) has been determined. The calorimetric procedure was compared to a previously identified methodology based on an amperometric biosensor.

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Abstract  

Dehydration of trehalose dihydrate implemented by slow heating (1 K min−1), has been monitored by Raman microspectroscopy from 25 to 110�C directly on single crystals. Between 90 and 120�C, gas initially trapped in irregular macroscopic defects, reorganizes to form spherical vacuoles. The Raman analysis of these vacuoles highlights that the areas in vicinity of the defects are the first affected by the dehydration mechanisms. Indeed, the progressive amorphization of the crystal starts around these defects.

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Abstract  

In this paper we compare the solid-state transformations upon room temperature milling of four sugars: lactose, trehalose, mannitol and sorbitol. The two disaccharides (lactose and trehalose) are found to undergo a direct transformation from crystal to glass while the two sugar alcohols (mannitol and sorbitol) are found to undergo polymorphic transformations. The origin of these different behaviors is discussed and ascribed to the relative position of the glass transition temperature (T g) of the amorphous states with respect to the milling temperature. This point was also finely studied through co-milling experiments of lactose and mannitol. These two compounds having their glass transition respectively above and below room temperature the T g of the mixture can be conveniently tuned on either side of the milling temperature by varying the concentrations.

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We studied the effects of storage temperature on the stability of dehydrated POPC (1-palmitoyl-2-oleoyl-phosphatidylcholine) mixed with sucrose, trehalose, or a sucrose/raffinose mixture. We used DSC to measure the gel-to-fluid phase transition temperature (T m) of POPC after incubation either below or near the glass transition temperature (T g) of the sugars in the mixture. Glass formation by the sugars around fluid-phase POPC led to the lowering ofT m below that of the fully hydrated lipid. Phospholipid phase behavior did not change during storage belowT g. In some samples stored aboveT g, trehalose crystallized completely; in these samples, theT g of POPC increased to that of the partially dehydrated phospholipid. Melting the crystalline sugar re-established its ability to lower POPC'sT m. We conclude that prevention of complete sugar crystallization was important for stability in the dry state, and that storage belowT g conferred long-term stability to the dehydrated sugar-lipid mixtures.

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