Research

Research

Prof. Basu was born in West Bengal, India. He completed his studies in India before moving to the USA. After completing postdoctoral studies at Arizona, he moved to Pittsburgh taking a faculty position at Duquesne University. In 2016, Basu Group moved to Indiana University-Purdue University Indianapolis. His research interest is in defining many roles that metal ions play in biological systems. The lab focuses on the general areas described in detail below.

Cellular interaction of Arsenicals.

Organoarsenicals have a long history of medicinal use. This dates back to the early work of Elrich led to the discovery of salvarsan for treating syphilis. More recently. However, another organoarsenical, roxarsone, has received much attention.  We have demonstrated that microbes can readily transform roxarsone releasing inorganic arsenic. In addition, we have shown the proangiogenic potential of roxarsone. Current projects includes a molecular level understanding of the events. To this end, we are using proteomic approaches (both 2D PAGE and LC-MS-MS) in identifying the key proteins involved in the chemistry. We have identified a large number of proteins that are up/down regulated depending on the conditions.

Bacterial Nitrate and Arsenic Reductases.

Using an informatics approach we have classified all nitrate reductases into four distinct sub-famillies: eukaryotic nitrate reductase (Euk-NR), membrane bound nitrate reductase (Nar), cytosolic assimilatory nitrate reductase (Nas) and periplasmic nitrate reductase (Nap). Geonome sequences of epsilonproteobacteria, many of them are pathogenic, have Nap. These pathogens can generate toxic nitrogen oxides through nitrate reduction. We have isolated substantial quantities of nitrate reductase from Sulfurospirillum barnesii for detailed biophysical investigation. A particular interest to us is to evaluate, at the molecular level, how nitrate reduction can influence the reduction of chromium.

In parallel, we have isolated and purified arsenate reductase from a haloakalophilic bacterium, Bacillus selenitireducens as a heterodimer. Interestingly, the optimum pH of this enzyme is 9.5 and functions very efficiently at a high salinity (90 g/l NaCl).  The arsenate reductase has also been isolated and characterized.

Rational Synthesis of Molybdenum Cofactor.

Both nitrate reductase and arsenate reductase have molybdenum cofactor at the active site. The same basic cofactor is also present in many eukaryotic enzymes such as sulfite oxidase and xanthine oxidase. Genetic disorder leading to defect in molybdenum cofactor biosynthesis leads to several physiological disorders, yet complete chemical synthesis of the cofactor has yet not been possible. We have developing a new modular synthetic approach for this important biomolecule.

Development of new Sensors for Metal Ions.

We have developed a new class of ene-dithiols that binds metal ions very effectively. These molecules were synthesized an ongoing efforts to synthesize certain features of the molybdenum cofactor. Many of the molecules are fluorophoric and we are exploring their optical properties as well as their metal binding, particularly lead binding, properties.

Mechanism of Oxygen Atom Transfer Reactions.

Many of the molybdenum enzymes function via oxygen atom transfer reactions. In general, OAT reactions have been investigated for many years, and such reactions have been interpreted in terms of a single transition state model.  Using well-defined model compounds we have demonstrated the multi-step nature of the OAT reactions. We have detected, isolated, and structurally characterized intermediate molecules of OAT reactions. Our detailed kinetic analyses have identified the rate-limiting step among these multiple steps of the reactions.