Good flow and compaction properties are necessary for the manipulation of particulate material in the pharmaceutical industry. The influence of the addition of an alternative sweetener, rebaudioside A, in a concentration 0.2% w/w and 0.5% w/w on the flow, shear and compaction properties of sorbitol for direct compaction, Merisorb® 200, was investigated in this work. Rebaudioside A worsened the flow properties of sorbitol: the Hausner ratio, the compressibility index and the mass flow rate through the aperture of a model hopper. Using a Jenike shear cell revealed a significant increase in cohesion leading to the decrease of the flow function; moreover, the addition of rebaudioside A increased the total energy for compression of tablets and plasticity estimated by the force-displacement method. Finally, the tablets showed a higher tensile strength and needed longer time to disintegrate compared to the tablets made of sorbitol itself. In view of the results for the free-flowable excipient, sorbitol, the effects of stevia even for a 0.2% w/w concentration have to be carefully considered, particularly whenever used in pharmaceutical formulations of poor flow properties.
Cation-Cl(-) cotransporters (CCCs) are integral membrane proteins which catalyze the coordinated symport of Cl(-) with Na(+) and/or K(+) ions in plant and mammalian cells. Here we describe the first Saccharomyces cerevisiae CCC protein, encoded by the YBR235w open reading frame. Subcellular localization studies showed that this yeast CCC is targeted to the vacuolar membrane. Deletion of the YBR235w gene in a salt-sensitive strain (lacking the plasma-membrane cation exporters) resulted in an increased sensitivity to high KCl, altered vacuolar morphology control and decreased survival upon hyperosmotic shock. In addition, deletion of the YBR235w gene in a mutant strain deficient in K(+) uptake produced a significant growth advantage over the parental strain under K(+)-limiting conditions, and a hypersensitivity to the exogenous K(+)/H(+) exchanger nigericin. These results strongly suggest that we have identified a novel yeast vacuolar ion transporter mediating a K(+)-Cl(-) cotransport and playing a role in vacuolar osmoregulation. Considering its identified function, we propose to refer to the yeast YBR235w gene as VHC1 (vacuolar protein homologous to CCC family 1).
- MeSH
- chloridy chemie MeSH
- DNA chemie MeSH
- elektrochemie metody MeSH
- fluorescenční mikroskopie metody MeSH
- fylogeneze MeSH
- genotyp MeSH
- iontový transport MeSH
- kationty chemie MeSH
- koncentrace vodíkových iontů MeSH
- konfokální mikroskopie metody MeSH
- membránové potenciály MeSH
- nigericin farmakologie MeSH
- oligonukleotidy chemie MeSH
- osmotický tlak MeSH
- otevřené čtecí rámce MeSH
- rekombinace genetická MeSH
- Saccharomyces cerevisiae - proteiny chemie fyziologie MeSH
- Saccharomyces cerevisiae metabolismus MeSH
- sorbitol chemie MeSH
- symportéry chemie fyziologie MeSH
- vakuoly chemie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- MeSH
- anestetika lokální chemie MeSH
- glycerol chemie MeSH
- karbamáty chemie MeSH
- povrchové napětí MeSH
- propylenglykoly chemie MeSH
- sorbitol chemie MeSH
- Publikační typ
- srovnávací studie MeSH
