Tertiary structure of protein is best determined by:
**Core Concept**
The tertiary structure of a protein refers to its three-dimensional shape and spatial arrangement of atoms, which is crucial for its function. This level of structure is determined by the interactions between amino acids and the overall folding of the protein.
**Why the Correct Answer is Right**
The correct answer is determined by the use of X-ray crystallography, which involves scattering X-rays off the atoms within a protein crystal to produce a diffraction pattern that can be used to determine the protein's three-dimensional structure. This method is capable of resolving the tertiary structure of proteins with high accuracy. The scattered X-rays are diffracted in specific directions, and the resulting diffraction pattern can be used to reconstruct the protein's three-dimensional structure.
**Why Each Wrong Option is Incorrect**
* **Option A:** NMR spectroscopy is a technique used to determine the secondary and tertiary structure of proteins, but it is not as accurate as X-ray crystallography for determining the tertiary structure.
* **Option B:** Mass spectrometry is a technique used to determine the molecular weight and composition of proteins, but it does not provide information about their tertiary structure.
* **Option C:** Circular dichroism spectroscopy is a technique used to determine the secondary structure of proteins, but it does not provide information about their tertiary structure.
**Clinical Pearl / High-Yield Fact**
X-ray crystallography is a key technique for determining the structure of proteins, which is essential for understanding their function and developing new treatments for diseases.
**Correct Answer:** C. Circular dichroism spectroscopy is a technique used to determine the secondary structure of proteins, but it does not provide information about their tertiary structure.