Q What makes positive and negative charges attract?

A This is an insightful question that scientists still do not have a complete answer for.

An electric charge is surrounded by an electric field such that an opposite charge placed in that region experiences a force that attracts it. We see the effects of this attraction in our everyday life, but not the field itself through which the positive and negative charges interact.

This question still has significant relevance for semiconductor materials research today. For example, how positive and negative charges interact in a material has a profound influence on the transport of charges or the current in electronic devices. Understanding this interaction is the key to the development of highly efficient materials and electronic devices.

ASSOCIATE PROFESSOR SUM TZE CHIEN, physicist and assistant dean (research) at Nanyang Technological University's (NTU) College of Science.

Q Can ATP (adenosine triphosphate) be harvested for energy outside biology, like in physics and chemistry?

A We know that ATP is the currency of the biological cell and therefore fundamental for life. Like in a typical engine, in which burning of gas, gasoline, diesel oil or hydrogen provides the energy, ATP cleavage into ADP and Pi (adenosine diphosphate and inorganic phosphate) provides the energy to drive molecular motors, which are key catalysts inside biological cells.

It will be interesting to understand how the energy release from ATP cleavage can be translated on to chips, where ATP provides energy for ultra-energy-efficient devices.

Furthermore, the way ATP is generated in the so-called electron-transport chain inside a biological cell is of great interest.

As revealed for photovoltaic cells, in which the process of photosynthesis was and is a model system, insight into such a mechanism will provide a new avenue of energy conversion in novel batteries.

PROFESSOR GERHARD GRUBER, a structural biologist and expert in ATP from NTU's School of Biological Sciences.