21 research outputs found
Sitting at the edge: How biomolecules use hydrophobicity to tune their interactions and function
Water near hydrophobic surfaces is like that at a liquid-vapor interface,
where fluctuations in water density are substantially enhanced compared to that
in bulk water. Here we use molecular simulations with specialized sampling
techniques to show that water density fluctuations are similarly enhanced, even
near hydrophobic surfaces of complex biomolecules, situating them at the edge
of a dewetting transition. Consequently, water near these surfaces is sensitive
to subtle changes in surface conformation, topology, and chemistry, any of
which can tip the balance towards or away from the wet state, and thus
significantly alter biomolecular interactions and function. Our work also
resolves the long-standing puzzle of why some biological surfaces dewet and
other seemingly similar surfaces do not.Comment: 12 pages, 4 figure
Evaluation of stress-inducible hsp90 gene expression as a potential molecular biomarker in Xenopus laevis
Chemical Form Matters: Differential Accumulation of Mercury Following Inorganic and Organic Mercury Exposures in Zebrafish Larvae
Mercury, one of the most toxic elements, exists in various
chemical
forms each with different toxicities and health implications. Some
methylated mercury forms, one of which exists in fish and other seafood
products, pose a potential threat, especially during embryonic and
early postnatal development. Despite global concerns, little is known
about the mechanisms underlying transport and toxicity of different
mercury species. To investigate the impact of different mercury chemical
forms on vertebrate development, we have successfully combined the
zebrafish, a well-established developmental biology model system,
with synchrotron-based X-ray fluorescence imaging. Our work revealed
substantial differences in tissue-specific accumulation patterns of
mercury in zebrafish larvae exposed to four different mercury formulations
in water. Methylmercury species not only resulted in overall higher
mercury burdens but also targeted different cells and tissues than
their inorganic counterparts, thus revealing a significant role of
speciation in cellular and molecular targeting and mercury sequestration.
For methylmercury species, the highest mercury concentrations were
in the eye lens epithelial cells, independent of the formulation ligand
(chloride <i>versus</i> l-cysteine). For inorganic
mercury species, in absence of l-cysteine, the olfactory
epithelium and kidney accumulated the greatest amounts of mercury.
However, with l-cysteine present in the treatment solution,
mercuric bis-l-cysteineate species dominated the treatment,
significantly decreasing uptake. Our results clearly demonstrate that
the common differentiation between organic and inorganic mercury is
not sufficient to determine the toxicity of various mercury species