In the 1950s, christian anfinsen demonstrated the renaturation of the protein ribonuclease (rnase) in vitro. after reduction (to reduce the disulfide links) and the addition of urea (to denature the protein), the protein was in an unfolded state. after removing the urea and the reducing agent, the protein refolded, with greater than 90% activity. if the urea were removed after oxidation occurred, the protein had less than 5% activity. why would the protein not refold correctly if the urea were removed after the reducing agent was removed? (in other words, what would happen if the urea were removed after oxidation? ) choose the best answer.

(a) urea would participate in weak bonding interactions with rnase, preventing oxidation of cys.
(b) the protein would not fully unfold (denature).
(c) disulfide bonds are not positioned correctly unless weak bonding interactions are present.
(d) contaminants in the rnase preparation would form covalent bonds with the protein, preventing reactivation.

The correct answer to the question: What would happen if the urea were removed after oxidation, would be, C: Disulfide bonds are not positioned correctly unless weak bonding interactions are present.

Explanation:

Christian Anfinsen´s and colleagues´s research on proteins, their structure, their function, and what affects them, yielded information that has impacted the way that proteins are studied today. This research was not only able to find the structure of proteins, but also how this structure was formed, and what would happen if it was affected by different factors, meaning, if the protein would remain functional or not. In his experiment with urea, Anfinsen and his colleagues found that what mattered in protein structure was the fine balance in the elements, called residue, inside the structure, and not those on the outside. They also found that when urea was removed from the protein after oxidation had happened, then the cysteine residue would not be placed correctly inside the structure, thus affecting it and reducing its capacity to perform.

step 1: initiation

initiation is the beginning of transcription. it occurs when the enzyme rna polymerase binds to a region of a gene called the promoter. this signals the dna to unwind so the enzyme can ‘‘read’’ the bases in one of the dna strands. the enzyme is now ready to make a strand of mrna with a complementary sequence of bases.

step 2: elongation

elongation is the addition of nucleotides to the mrna strand. rna polymerase reads the unwound dna strand and builds the mrna molecule, using complementary base pairs. there is a brief time during this process when the newly formed rna is bound to the unwound dna. during this process, an adenine (a) in the dna binds to an uracil (u) in the rna.

step 3: termination

termination is the ending of transcription, and occurs when rna polymerase crosses a stop (termination) sequence in the gene. the mrna strand is complete, and it detaches from dna.