Question

5. The Royal Swedish Academy of Science awarded the Nobel Prize in Chemistry 2017 Jacques Dubochet, Joachim Frank, and Richard Henderson "for developing cryo- electron microscopy for the high- resolution structure determination of biomolecules in solution". Based on your Bonus reading assignment, “The Development of Cryo-Electron Microscopy”, answer the following questions. a. X-ray crystallography and NMR are the methods preceded cryo-EM for structure determination as discussed in Lecture #13? Discuss the fundamental principles of these technologies, their differences, and their limitations.

Answer 1

X ray crystallography is a technique in which atomic and molecular structure of a crystal can b determined,

Crystalline structures cases a beam of incident x Ray's to diffraction in specific directions.and an image is formed.

Limitation is as unit cell becomes larger and complex,, picture provided becomes less resolved ..

NMR. is nuclear magnetic resonance.

In which nuclei in strong constant magnetic field are given a weak oscillating magnetic field. Nuclei produce electromagnetic signal with a frequency characteristic of magnetic field .

NMR is used to determine the structure of organic molecules in Solution.

It is also used in MRI.

Limitation is desired isotope of NMR may have little abundance.

Cryo, electron microscopy is a technique applied on samples cooled to cryogenic temperature and embedded in environment of vitreous water.

It is used for macromolecular structure determination

Limitations is image contrast is low and

Difficulty to take images in tilted specimens..