Search results for "halos"
showing 10 items of 175 documents
Role of residual water hydrogen bonding in sugar/water/biomolecule systems: a possible explanation fortrehalose peculiarity
2007
We report on the set of experimental and simulative evidences which enabled us to suggest how biological structures embedded in a non-liquid water–saccharide solvent are anchored to the surrounding matrix via a hydrogen bond network. Such a network, whose rigidity increases by decreasing the sample water content, couples the degrees of freedom of the biostructure to those of the matrix and gives place to protein–saccharide–water structures (protein–solvent conformational substates). In particular, the whole set of data evidences that, while the protein–sugar interaction is well described in terms of a water entrapment hypothesis, the water replacement hypothesis better describes the sugar–m…
Effects of protein on retention of ADH enzyme activity encapsulated in trehalose matrices by spray drying
2008
The retention of the enzymatic activity of alcohol dehydrogenase (ADH) on spray drying was examined under various drying conditions. Trehalose was used in the formulation of feed stocks for the spray drying. The retention of ADH activity was dependent on the concentration of ADH in the feed solution. The addition of other proteins, such as bovine serum albumin and β-lactoglobulin, exhibited an additional improvement of the retention of ADH activity. The inlet and outlet temperature of the drying air was another key factor for the enzyme activity on the spray drying. The surface morphology of the spray-dried particle was changed drastically with the addition of proteins.
Characterisation of the glycosidic linkage by infrared and Raman spectroscopy in the C-H stretching region: α,α-trehalose and α,α-trehalose-2,3,4,6,6…
1991
Abstract I.r. and Raman spectra of solid α,α-trehalose and α,α-trehalose- 2,3,4,6,6-d 10 in the C-H and C-D stretching regions are recorded. The experimental data are reproduced satisfactorily by normal co-ordinate and i.r. absorption intensity calculations which take into account the specific interactions of each C-H hydrogen with nearby oxygen lone-pairs. The relevance of the region 2800–3000 cm −1 in α,α-trehalose- 2,3,4,6,6-d 10 for the study of the conformational properties of the inter-glycosidic linkage is discussed.
The water association band as a marker of hydrogen bonds in trehalose amorphous matrices
2017
The relevant role played by residual water in modulating the dynamics and structure of a protein, a matrix and their coupling has been thoroughly studied in bioprotective amorphous saccharide matrices via experiments and simulations. In order to better characterize this residual water and the hydrogen bond structures in which it is involved, in this work infrared spectroscopy experiments are conducted on trehalose-water systems. The properties of water are inferred from the study of a peculiar infrared band, the water association band, which we exploited as a marker of the hydrogen bonds in which water is involved. Our aim was the identification of populations of water molecules, which give…
On the biochemical classification of yeast trehalases: Candida albicans contains two enzymes with mixed features of neutral and acid trehalase activi…
2009
Abstract Two enzymes endowed with trehalase activity are present in Candida albicans . The cytosolic trehalase (Ntc1p), displayed high activity in exponential phase regardless of the carbon source (glucose, trehalose or glycerol). Ntc1p activity was similar in neutral (pH 7.1) or acid (pH 4.5) conditions, strongly inhibited by ATP, weakly stimulated by divalent cations (Ca 2+ or Mn 2+ ) and unaffected in the presence of cyclic AMP. The Ntc1p activity decreased in stationary phase, except in glycerol-grown cultures, but the catalytic properties did not change. In turn, the cell wall-linked trehalase (Atc1p) showed elevated activity in resting cells or in cultures growing on trehalose or glyc…
Immediate early response of the marine sponge Suberites domuncula to heat stress: Reduction of trehalose and glutathione concentrations and glutathio…
1997
The marine sponge Suberites domuncula was used to identify early markers for thermal stress. Cubes from sponges have been kept for 30 min at 31°C (10 °C higher than the ambient temperature). After this treatment the sponge cubes were kept again at 21°C. To demonstrate that the animals reacted to the elevated temperature, the expression of heat shock protein (HSP) was determined. Using an antibody raised against HSP70, it was found by Western blotting that the animals specifically express a 45 kDa polypeptide after heat treatment. It was shown that even after 10 min of heat treatment the steady-state concentration of trehalose drops by 40% from a base level of 13 nmol/mg protein. The activit…
MbCO embedded in trehalosyldextrin matrices: thermal effects and protein-matrix coupling
2010
Saccharide-based biopreservation is widely studied because of its scientific importance and possible technological outcomes for food and pharmaceutical industries. Ternary protein/saccharide/water systems have been extensively exploited to model the characteristics of the in vivo biopreservation process. A tight, water dependent, protein–matrix coupling has been shown to occur in various simple saccharide amorphous matrices, which is stronger in trehalose. The efficiency as bioprotectant of trehalose has been ascribed to this tight coupling, since the appearance of damages on biological structures will more involve structural variations of the surrounding matrix. Here we present, as an appl…
Impact of Starmerella bacillaris and Zygosaccharomyces bailii on ethanol reduction and Saccharomyces cerevisiae metabolism during mixed wine fermenta…
2021
AbstractThe bulk of grape juice fermentation is carried out by the yeast Saccharomyces cerevisiae, but non-Saccharomyces yeasts can modulate many sensorial aspects of the final products in ways not well understood. In this study, some of such non-conventional yeasts were screened as mixed starter cultures in a fermentation defined medium in both simultaneous and sequential inoculations. One strain of Starmerella bacillaris and another of Zygosaccharomyces bailii were chosen by their distinct phenotypic footprint and their ability to reduce ethanol levels at the end of fermentation, particularly during simultaneous vinification. S. bacillaris losses viability strongly at the end of mixed fer…
Interaction Between Osmotic and Hydrostatic Pressure in Yeast Inactivation
1999
The protective effect of an osmotic perturbation on high-pressure inactivation has been investigated using a yeast strain:Saccharomyces cerevisiae. Osmotic shocks have been carried out with binary medium (glycerol/sorbitol and water) with or without glucose. Variations of osmotic level, osmotic shift kinetics and time between osmotic and hydrostatic treatment (350 MPa/10 min) have allowed the characterization of cell baroprotection. Two different cumulative baroprotection effects have been distinguished: one conferred by the solute on biological structures and the other related to the osmotic stress, cell volume variations and stress metabolism response (HSP, trehalose). These experiments h…