@article {915, title = {Design of ultrasensitive DNA-based fluorescent pH sensitive nanodevices.}, journal = {Nanoscale}, volume = {7}, year = {2015}, month = {2015 Jun 14}, pages = {10008-12}, abstract = {

Here we tune the pH sensitivity of a DNA-based conformational switch, called the I-switch, to yield a set of fluorescent pH sensitive nanodevices with a collective, expanded pH sensing regime from 5.3 to 7.5. The expanded pH regime of this new family of I-switches originates from a dramatic improvement in the overall percentage signal change in response to pH of these nanodevices.

}, issn = {2040-3372}, doi = {10.1039/c5nr01158b}, author = {Halder, Saheli and Krishnan, Yamuna} } @article {912, title = {A pH-independent DNA nanodevice for quantifying chloride transport in organelles of living cells.}, journal = {Nat Nanotechnol}, volume = {10}, year = {2015}, month = {2015 Jul}, pages = {645-51}, abstract = {

The concentration of chloride ions in the cytoplasm and subcellular organelles of living cells spans a wide range (5-130 mM), and is tightly regulated by intracellular chloride channels or transporters. Chloride-sensitive protein reporters have been used to study the role of these chloride regulators, but they are limited to a small range of chloride concentrations and are pH-sensitive. Here, we show that a DNA nanodevice can precisely measure the activity and location of subcellular chloride channels and transporters in living cells in a pH-independent manner. The DNA nanodevice, called Clensor, is composed of sensing, normalizing and targeting modules, and is designed to localize within organelles along the endolysosomal pathway. It allows fluorescent, ratiometric sensing of chloride ions across the entire physiological regime. We used Clensor to quantitate the resting chloride concentration in the lumen of acidic organelles in Drosophila melanogaster. We showed that lumenal lysosomal chloride, which is implicated in various lysosomal storage diseases, is regulated by the intracellular chloride transporter DmClC-b.

}, issn = {1748-3395}, doi = {10.1038/nnano.2015.130}, author = {Saha, Sonali and Prakash, Ved and Halder, Saheli and Chakraborty, Kasturi and Krishnan, Yamuna} } @article {913, title = {Tuning the pH Response of i-Motif DNA Oligonucleotides.}, journal = {Chembiochem}, volume = {16}, year = {2015}, month = {2015 Jul 27}, pages = {1647-56}, abstract = {

Cytosine-rich single-stranded DNA oligonucleotides are able to adopt an i-motif conformation, a four-stranded structure, near a pH of 6. This unique pH-dependent conformational switch is reversible and hence can be controlled by changing the pH. Here, we show that the pH response range of the human telomeric i-motif can be shifted towards more basic pH values by introducing 5-methylcytidines (5-MeC) and towards more acidic pH values by introducing 5-bromocytidines (5-BrC). No thermal destabilisation was observed in these chemically modified i-motif sequences. The time required to attain the new conformation in response to sudden pH changes was slow for all investigated sequences but was found to be ten times faster in the 5-BrC derivative of the i-motif.

}, issn = {1439-7633}, doi = {10.1002/cbic.201500182}, author = {Lannes, Laurie and Halder, Saheli and Krishnan, Yamuna and Schwalbe, Harald} }