33. XRay crystallography

Question 1

Bragg diffraction equation

Answer 1

2 x d x sin (O) = n x lamda

Question 2

Upper mass limit of ESI

Answer 2

100kDa

Question 3

What is the upper mass limit of MALDI?

Answer 3

300kDa

Question 4

What is the precision of mass measurement for ESI?

Answer 4

0.005%-0.05%

Question 5

What is the precision of mass measurement for MALDI?

Answer 5

0.05%-0.1%

Question 6

What is the sensitivity of ESI?

Answer 6

0.5 pmol

Question 7

What is the sensitivity of MALDI?

Answer 7

0.1 pmol

Question 8

F = q * E + q * v * B

What is this equation? Explain parameters

Answer 8

Lorentz force
Q : charge on the particle
E : electric field
B : magnetic field
V : velocity of the particle

Question 9

TOF equation

Answer 9

t = (d/sqrt2U) * sqrt (m/q)

Question 10

Wavelength range of x-rays

Answer 10

10^-8 to 10^-12 metres

Question 11

Frequency range of X-rays

Answer 11

10^6 to 10^20 hertz

Question 12

What are the 2 types of difraction?

Answer 12

• Fresnel

- Fraunhaufer

Question 13

What is a mono crystal?

Answer 13

crystal lattice of the entire sample is unbroken and continuous

Question 14

5 steps of X-ray crystallography

Answer 14

1. Crystalization of the sample
2. diffraction + interference
3. Detection
4. Calculation of lattice spacing
5. Construction of electron density map + atomic model

Question 15

What information do we get from interference pattern?

Answer 15

• angle of diffraction

- intensity of spot (pptional to the number of electrons in the plane)

Question 16

What is the interference maxima?

Answer 16

Site of amplification (constructive interference)

Question 17

What is mass spectrometry?

Answer 17

Determining the chemical composition of a sample by analyzing the spectra of the mass of atoms in a gas phase

Question 18

3 components of mass spectrometer

Answer 18

ion source
analyser
detector

Question 19

What does ESI stand for?

Answer 19

electrospray ionization

Question 20

What is the result of ESI?

Answer 20

a continuous stream of ionized, accelerated molecules

Question 21

What does MALDI stand for?

Answer 21

Matrix assisted laser desorption / ionization

Question 22

What is desorption?

Answer 22

release of an absorbed substance from a surface

Question 23

What are 3 important characteristic of the matrix the sample is absorbed into?

Answer 23

• small molecular weight
• contains tiny cations
• highly absorbtive of laser light

Question 24

What happens to the matrix when the laser hits it?

Answer 24

irradiated spot becomes heated and vibrationally excited. matrix molecules carry analyte molecules inton the gas phase. Analyte molecules are ionized by being protonated / deprotonated

Question 25

What is the Lorentz force?

Answer 25

forced exerted on a charged particle moving through both an electric and a magnetic field

Question 26

Principle of the magnetic method for mass analysis

Answer 26

ions are deflected by a magnetic field according to their masses. The lighter they are, the more deflected they will be.

Question 27

What is the time of flight method?

Answer 27

Ions with a larger m/z ratio will reach a lower speed if accelerated with the same voltage

Question 28

What technique is most used in proteomics?

Answer 28

Tandem mass spectrometry (2 or more mass analyzers connected together)

Question 29

Which enzyme is missing in phenylketonuria?

Answer 29

phenylalanine hydroxylase