Protein Structure

Question 1

What are the two most important techniques for elucidating the conformation of proteins

Answer 1

X-ray crystallography and nuclear magnetic resonance spectroscopy

Question 2

What are the three components of x-ray crystallographic analysis

Answer 2

protein crystal, a source of x-rays, and a detector

Question 3

X-ray crystallography first requires the preparation of a protein or protein complex into what

Answer 3

a crystal form, in which all protein molecules are oriented in a fixed, repeated arrangement with respect to one another

Question 4

Slowly adding ___________ or another ______ to a concentrated solution of protein to reduce its solubility favors the formation of highly ordered crystals

Answer 4

Ammonium sulfate or salt

Question 5

Enzyme crystals may display catalytic activity if the crystals are suffused with _____

Answer 5

substrate

Question 6

a beam of x-rays of wavelength _____ is produced by accelerating electrons against a copper target

Answer 6

1.54 angstroms

Question 7

synchrotoron radiation

Answer 7

The acceleration of electrons in circular orbits at speeds close to the speed of light

Question 8

which are more intense synchroton-generated x-ray beams or those generated by electrons hitting copper

Answer 8

Synchroton-generated x-ray beams

Question 9

Higher intensity of the x-ray beams allows for what

Answer 9

higher quality data from smaller crystals over a shorter exposure time.

Question 10

When a narrow beam of x-rays is directed at the protein crystal?

Answer 10

Most of the beam passes directly though the crystal while a small part is scattered in various directions

Question 11

the scattered, or diffracted, x-rays can be detected by

Answer 11

x-ray film or a solid-state electronic detector

Question 12

What is the purpose of the scattering pattern

Answer 12

it provides abundant information about protein structure

Question 13

What are the 3 basic principles underlying x-ray crystallography

Answer 13

1. ) electrons scatter x-rays
2. ) the scattered waves recombine
3. ) the way in which the scattered waves recombine depends only on the atomic arrangement

Question 14

The amplitude of the wave scattered by an atom is proportional to what

Answer 14

its number of electrons (Thus, a carbon atom scatters six times as strongly as a hydrogen atom does)

Question 15

If scattered waves are in phase they

Answer 15

add to one another

Question 16

What is an election-density map

Answer 16

it is a three-dimensional graphic representation of where the electrons are most densely localized and is used to determine the positions of the atoms in the crystallized molecule

Question 17

When is Nuclear magnetic resonance spectroscopy used

Answer 17

when proteins do not readily crystallize

it is able to reveal atomic structure of macromolecules in solution

Question 18

Nuclear magnetic resonance spectroscopy is dependent on what

Answer 18

the fact that certain atomic nuclei are intrinsically magnetic

Question 19

The ____ of a proton generates a magnetic moment

Answer 19

Spinning

Question 20

The magnetic moment can take how many states and what are their names

Answer 20

2, alpha and beta

Question 21

which magnetic moment has a lower energy alpha or beta and why

Answer 21

alpha, because it aligns with the applied field

Question 22

what causes a magnetic moment to go from alpha to beta state

Answer 22

applying a pulse of electromagnetic radiation (radio frequency, or RF, pulse) provided that the frequency corresponds to the engr. difference between the alpha and beta states