He is an expert in enzymology and has conducted many studies in that field.

He is an expert in enzymology and conducts many researches.

His body showed a rejection reaction to the transplanted organ.

She overreacted to his words.

Nuclear reactions are used for mass production of energy.

His single word triggered a chain reaction, and everything changed.

I was surprised by his overreaction.

This reaction occurs through a chemical process.

He is an excellent chemist who made many discoveries.

He is an expert in petrochemistry.