All posts by Manaswini Sarangi

Scientists find a novel way for lead-free water

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World’s massive economic growth is undoubtedly the result of the industrial era, which began between 18th-19th century in parts of Europe and North America. With the constant need and greed of human beings, industrialization became colossal in no time and with it we have brought upon ourselves both the positive and negative aspects. Current ecological system has been under perpetual mortification, thanks to the enormous level of pollution in air, water, soil, just name it; owing to the undeniable expansion of mechanisation. Among several other consequences of the above, contamination of drinking water on our planet is one of the most pressing issues of our time. Drinking water constitutes a minuscule fraction of entire water content on earth that renders the survival of a vast majority of living organisms. Release of heavy metal ions like those of lead, mercury and cadmium from industries to water has edged disastrous fallouts in public health. This paucity of clean drinking water has directed scientists over the world to find ways to remove hazardous wastes and purify contaminated water.

blog-2_c Simplistic illustration of ion exchange mechanism for lead capture and removal (in water).

Ekashmi Rathore, a graduate student in Dr. Kanishka Biswas’s Laboratory at NCU, JNCASR, have identified a novel compound for isolating lead from water. Through the traditional process of intercalation – a reversible insertion of a molecule (or ion) into materials with layered structures, Ekashmi synthesised a potassium intercalated layered compound 1 (K-MPS-1, K0.48Mn0.76PS3.H2O ) which is competent enough for efficient extraction of lead ions from water even at extremely low concentration, i.e. 1 ppb which is well below the tolerance level of lead ions in drinking water, <15 ppb as per USA-EPA 2. During intercalation of potassium ion, the interlayer spacing (van der Waals gap) between the sheets increases, creating voids at the manganese sites. In the following step, when the lead contaminated water was allowed to pass through the intercalated compound, the potassium ions were displaced and lead ions got adsorbed into the void sites of manganese, further restoring the increased gap (originally interlayer spacing at 6.45 Å, intercalation increased it to 9.40 Å, then void site occupancy by lead ions decreased it back to ~6.45 Å).

The entire process has been examined in a wide range of pH (2-12) water and works adequately great in being able to remove lead within this whole spectrum. Along with making the compound useable in various types of water content, the team has also shown its high removal capacity (~393 mg/g) of lead ions compared to earlier studies. Further data showed 97% extraction of lead ions in a matter of 4.5h and ≥99% removal within no more than 12h. The course of action being relatively swift ensures its pragmatic nature at an industrial level. They also showed the compound’s precise selectivity in terms of being able to capture and remove only lead ions from a pool of several other mono and divalent ions that are also present in water. Additionally, the compound is stable to oxidisation compared to previously tried methods and hence comes across as an advantage in materialising this reaction.

img_20180407_175937Ekashmi (left) with Dr. Kanishka Biswas (right) at Solid State Chemistry Laboratory in NCU, JNCASR.

In fact, very interestingly, when the same procedure was experimented using water from a nearby lake (Rachenahalli Lake, Bangalore), the compound (K-MPS-1) was successfully able to selectively sequester ~99% of lead ions! So, as we can see, this novel intercalated compound is able to efficiently isolate harmful lead from drinking water through its high removal capacity, its high selectivity, being able to function in a wide pH range, works even when the concentration of lead ion is very low and more importantly being stable.

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Sources of heavy metal and radionuclide in water and schematic representation for the mechanism of lead ion (Pb2+) and cesium ion (Cs+ ) capture by K-MPS-1. (Mn, purple; P, blue; S, yellow; K, black; heavy metal or radionuclide, green).

Ekashmi’s alluring idea accompanied by the prudent experiments led it to a success where her work got published in The Journal of Physical Chemistry (C) 1. She also got an award by The Falling Walls Lab India 2017, following which she beautifully presented her work in Berlin the same year (check out the video). She owes this success to her mentor Dr. Kanishka Biswas for encouraging her to pursue the idea of lead removal despite the main theme of the lab being research on thermoelectric materials. Ekashmi pursued this idea further and implemented it in efficient capture and removal of Cesium, an enduring radioisotope, from water using the same compound K-MPS-1 and similar methodology used for lead isolation 3. Further research on her plate includes mercury removal from contaminated areas and development of prototypes for detection of hazardous wastes in water.

This article is authored by Manaswini Sarangi, Evolutionary Biology Laboratory, EIBU, JNCASR.

References

  1. Rathore, Ekashmi, Provas Pal, and Kanishka Biswas. “Layered Metal Chalcophosphate (K-MPS-1) for Efficient, Selective, and ppb Level Sequestration of Pb from Water.” The Journal of Physical Chemistry C121.14 (2017).
  2. United States Environmental Protection Agency; Drinking Water Requirements for States and Public Water Systems; https://www.epa.gov/dwreginfo/lead-and-copper-rule.
  3. Rathore, Ekashmi, Provas Pal, and Kanishka Biswas. “Reversible and efficient sequestration of Cs from water by layered metal thiophosphate, K0. 48Mn0. 76PS3. H2O.” Chemistry-A European Journal (2017).

Deciphering a new role of a protein complex aiding the Pac-man job inside cells!

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Bagging two Nobel Prizes, first in 1974 1 and then recently in 2016 2, work on Autophagy stands at the cutting edge of both fundamental and application based research. The word autophagy with its Greek origin, meaning ‘self-eating’ (auto: self, phagein: to eat) is one among several efficient mechanisms functioning inside a living organism.

The channel through which intracellular materials such as certain byproducts of metabolism, damaged proteins, those that are brewing for degradation are actively ingested by the cell itself is what defines the course and action of autophagy. These intracellular materials that are intended for ultimate degradation are ingested by a structure called autophagosome or the ‘Pacman’ as aptly called by Dr. Ravi Manjithaya, a research scientist at MBGU, JNCASR. These autophagosomes then play the role of a garbage truck where they transport the ingested cargo into another structure called lysosome. Post fusion with the vacuole (lysosome), multiple enzymes help in the ultimate degradation and absorption of intracellular waste. This process also involves sending back useful items like amino acids back to the cytoplasm.

So, you see there is this whole system of collecting the trash, degrading and eventually re-cycling them! What’s more fun and further interesting is digging out the mechanism underlying the efficient functionality of this integral system of autophagy.

rm-2Dr. Ravi Manjithaya with his graduate student Gaurav Barve at the           Autophagy Lab

Dr. Ravi Manjithaya’s (RM) group at MBGU studies autophagy and related elemental processes using yeast, human cells and mouse as model systems. The molecular components of autophagy were first laid out in the yeast Saccharomyces cerevisiae. His group explores through multiple approaches like, the ‘cargo approach’ to identify regulatory mechanisms fundamental to autophagy by examining which of the toughest cargos can be tackled by this process. For this, his group employs both, a ‘chemical biology approach’ and the ‘classical genetics approach’.

One of his group’s latest works has carried out an unbiased screen for autophagy defects in yeast Saccharomyces cerevisiae, and shown the significance of a group of proteins called ‘Septins’ during the early stages of autophagy 3. Septins, first discovered in yeast S. cerevisiae are a group of proteins that are highly conserved in eukaryotes (although absent in plants) and serve as one of the key cytoskeletal elements in cell division process. Functional role of septins in yeast autophagy was unclear before this study. However, septins have been shown to have role in dynamics of cell membrane shapes. In order to determine the importance of septins in autophagy and their potential contribution to the formation of the autophagosomal membrane structure per se, RM’S group carried out well-thought out targeted experiments using budding yeast cells.

By following degradation of cargo (peroxisomes) for autophagic capture and degradation, RM’s group identified several septins whose functional forms were required in this process. To understand their roles better, the lead author and graduate student, Gaurav resorted to fluorescent live cell microscopy. By following these fluorescently tagged (GFP: Green Fluorescent Protein) septins, Gaurav observed the transition of these septins towards the locations inside the cell that are important for autophagosome formation. Interestingly, the septin-GFP proteins were often found in the shape of ring (roughly the size of autophagosomes) surrounding the pre-autophagosomal structures (PAS), which is the birthplace of autophagosomes. The team further went ahead to examine if the septins had physical interaction with autophagy proteins and identified two autophagy proteins, Atg8 and Atg9 as septin interacting partners. Gaurav elucidated how precisely this septin movement is vital  for providing membrane from various cellular locations for building autophagosomes.

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Overall, RM’s team for the first time exemplified the key role of these groups of proteins called septins in autophagosome maturation, direct physical interaction with autophagosomal membrane proteins (Atg8, Atg9), movement of septins from one location to another and most intriguingly development of septin rings that are similar in dimension to that of the autophagosomes. This study has opened up new questions such as how exactly septins help in autophagosome formation? Since septins interacted with Atg9 vesicles, how do the aid in providing membrane source for autophagosome formation? Does the complex of septins involved in cell division is the same complex that helps in autophagosome formation or are there some additional factors involved in it? And finally, what drives septins off from their usual localization at the bud-neck (region between mother and daughter yeast cell) to the site of autophagosome formation?

This work published in the Journal of Cell Science (JCS), 2018 details the beauty of this entire mechanism at play.

This article is authored by Manaswini Sarangi, Evolutionary Biology Laboratory, EIBU, JNCASR.

References

  1. “Physiology or Medicine 1974 – Press Release”. org.Nobel Media AB (2014). http://www.nobelprize.org/nobel_prizes/medicine/laureates/1974/press.html
  1. “The 2016 Nobel Prize in Physiology or Medicine – Press Release”. org.Nobel Media AB (2014). http://www.nobelprize.org/nobel_prizes/medicine/laureates/2016/press.html
  1. Barve, Gaurav, et al. “Septins are involved at the early stages of macroautophagy in S. cerevisiae.” J Cell Sci(2018): jcs-209098.
  1. Barve, Gaurav. “First person–Gaurav Barve.” (2018).