Science.

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Across
  1. 3. specialized biological proteins that act as catalysts, speeding up vital chemical reactions in living organisms without being consumed
  2. 4. relating to the nucleus of an atom.
Down
  1. 1. a class of oxidative enzymes found in bioluminescent organisms (such as fireflies, bacteria, and fungi)
  2. 2. Soviet physicist who won the 1958 Nobel Prize in Physics for discovering the "Cherenkov effect" in 1934