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What structural features of protein molecules allow them to form the crystals required for imaging by X-ray crystallography?
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To determine: The structural features of protein molecules that allow proteins to form crystals required for imaging by X-ray crystallography.
Introduction: X-ray crystallography is a technique that enables scientists to determine the exact position of thousands of atoms that are present in a typical molecule of protein. In X-ray crystallographic technique, a sharp beam of X-rays is directed over the crystals where it diffracts at specific angles to form diffraction pattern of spots.
Explanation of Solution
The formation of crystals of proteins is a very crucial step for imaging of proteins by X-ray crystallography techniques. By forming a molecule of protein into a crystal, in which atoms align themselves in a well-defined and repetitive manner, researchers can measure diffraction of X-rays by atoms. It helps in determining the position of atoms within the molecule of protein.
For the formation of protein crystals, the size of crystals should be sufficiently large (20-100 micrometer on each side) and must be free of any kind of imperfection such as a fracture that would lead to scattering of X-rays and their analysis.
Crystals of proteins are usually grown by decreasing solubility of proteins by adding precipitants. All these precipitants bind with molecules of water and reduce the amount of free water in the solution in which dissolution of proteins takes place. Formation of crystals takes place when the solution becomes supersaturated.
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Chapter 3 Solutions
Becker's World of the Cell (9th Edition)
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- Oftentimes, the major challenge in the determination of protein structure via X-ray crystallography is the production of good crystals. One common approach is to crystallize fragments of the whole protein instead of crystallizing the whole protein. If you were to cleave a protein into fragments that will still retain the folding of that fragment in the whole protein, where is the best location to perform the cleavage? O At the ends of each alpha helix. O At the ends of a protein motif. O At the points connecting protein domains. O At the ends of beta strands.arrow_forwardThe given protein, Protein X, is a heterotrimer - meaning it is a multimeric protein consisting of different polypeptide chains. Its molecular weight is 200 kDa. Using SDS-PAGE, the protein was characterized and the following profile is the result (attached in the picture). 1: Standard Protein Ladder 2: Protein X solution 3: Protein X solution + β-mercaptoethanol Based on the given gel profile in the picture, can it be concluded that the solution of Protein X is pure? Explain. can it be concluded that disulfide bonds hold together Protein X's quaternary structure? Explain.arrow_forwardThe given protein, Protein X, is a heterotrimer - meaning it is a multimeric protein consisting of different polypeptide chains. Its molecular weight is 200 kDa. Using SDS-PAGE, the protein was characterized and the following profile is the result (attached in the picture). 1: Standard Protein Ladder 2: Protein X solution 3: Protein X solution + β-mercaptoethanol Determine the molecular weights of the three subunits of protein X based on the gel profile. Write the MW of each subunit and explain the obtained answer.arrow_forward
- Describe the 4 levels of protein structure: primary, secondary, tertiary and quaternary. And, note which will be disrupted by application of heat.arrow_forwardWhat is the minimum number of polypeptide chains necessary for quaternary structure to exist?arrow_forwardWhat type of information is contained in the three-dimensional structure of proteins? What is the significance of 3D structure prediction? Discuss in depth the key aspects involved in 3D protein structure prediction and computational assessment.arrow_forward
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