Question

Which of the following is NOT an application of proteomics?

• A. Identification of all proteins in the sample
• B. Identification of 3 dimensional structure of all proteins in the sample
• C. Expression profiling of proteins in the sample
• D. Identification of post-translational modification site of protein

Hint:

Proteomics = Mass Spectrometry.
Structural Biology = X-ray/NMR.
Proteomics gives you the "Parts List" of the cell; Structural Biology shows you the "Blueprint" of the individual parts.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
Proteomics is the large-scale study of the proteome—the entire set of proteins produced or modified by an organism or system. The question identifies which of the listed tasks is outside the scope of standard proteomic methodologies.

Step 2: Detailed Explanation:

• Scope of Proteomics: Proteomics typically utilizes High-Throughput (HTP) techniques like 2D-Gel Electrophoresis and Mass Spectrometry (MS). It excels at identifying which proteins are present (Option A) and determining their relative abundance (expression profiling, Option C) under different conditions (e.g., healthy vs. diseased).

• Functional Analysis: Modern proteomics can also map post-translational modifications (PTMs) like phosphorylation or glycosylation (Option D), which are critical for protein function.

• Limitation regarding 3D Structure: Determining the 3-dimensional structure of a protein is the domain of Structural Biology. This requires specialized, low-throughput techniques like X-ray Crystallography, NMR Spectroscopy, or Cryo-Electron Microscopy.

• Scale: While "Structural Proteomics" is an emerging sub-field, it is currently impossible to determine the 3D structure of "all" proteins in a complex biological sample simultaneously using standard proteomic workflows. Proteomics tells you "what" and "how much," but not the "exact shape" of every molecule.

Step 3: Final Answer:
While proteomics provides comprehensive data on protein identity and expression, it does not routinely identify the 3D structures of all proteins in a sample; that remains a challenge for structural biology.