text: Peptide bonds are reduced by this element in the Lowry assay for protein concentration.
full_question: Peptide bonds are reduced by this element in the Lowry assay for protein concentration. Complex IV of the ETC relies on iron and this element exchanging electrons. This element's tetraammine complex is colored indigo, making it a great detector for ammonia. The original high-temperature superconductors were oxides of this element. It only forms +1 and +2 oxidation states. This element and (*) zinc made up a Daniell cell, the prototypical galvanic cell. The standard for electrical conductivity is given relative to this element. This element reacts with carbonates to form verdigris. It alloys with both zinc and tin to make brass and bronze respectively. For 10 points, name this metal found right above silver and gold on the Periodic Table. 
first_sentence: Peptide bonds are reduced by this element in the Lowry assay for protein concentration.
raw_answer: copper [or Cu]