Week 8 L1a: Fundamentals of Biological Mass Spectrometry

Question 1

What is mas spec?

Answer 1

allows the mass of a molecule to be determined

measuring the physical properties of charged particles.

Question 2

What can be used alongside mass spec to determine structure?

Answer 2

Tandem mass spec

Question 3

What can mass spec be useful in, in relation to life science?

Answer 3

proteomics

Question 4

What is proteomics?

Answer 4

identification of protein species in a biological sample

Identification of different proteoforms

Question 5

What else can MS be used of?

Answer 5

drug testing, security (explosives), quality control & forensics

Question 6

What is a classical methods of MS?

Answer 6

electron ionisation mass spec

Question 7

How do we create a charge on the sample?

Answer 7

shoot a beam of electrons at it. typically +1 charge

Question 8

What does mass spec measure?

Answer 8

mass/charge ratio

m/z

Question 9

How does the e- beam create a +1 charge on molecule?

Answer 9

kicks out an e- from a neutral molecules we are trying to study

Question 10

What does EI-MS cause?

Answer 10

fragmentation of molecule

Question 11

What molecules is mas spec useful in?

Answer 11

small molecules, not large

Question 12

Why are larger molecules harder to analyse with EI-MS?

Answer 12

more bonds = will generate many fragments resulting in a lot of noise

Question 13

What is used to separate ionised sampled in EI-MS?

Answer 13

MAGNET

Question 14

What does the detector tell us?

Answer 14

the m/z depending on where it hits the detector
light or heavy sample ???
y+, x+, z+ etc
We have known points on the detector and will correlate to where the molecule hits

Question 15

Why does the mass not change of the molecule when ionised?

Answer 15

e- = negligible

mass very similar to original

Question 16

Why must MS carried out in a vacuum?

Answer 16

prevent collision with air molecules

take out air molecules

Question 17

Does the MS measure charge?

Answer 17

NO! only measure m/z ratio

Question 18

What detects the m/z ratio?

Answer 18

mass analysers

Question 19

What is the mean free path?

Answer 19

The average distance travelled by an ion before it collides with an air molecule

Question 20

What is the mean free path equation?

Answer 20

wavelength=1/N*pheta

Question 21

Why might the parent molecule appear with a mass of +1?

Answer 21

diff isotopes of carbon, C12/13

Question 22

What does brutal MS result in?

Answer 22

quantitatal fragmentation

cant see parent molecule

Question 23

What level of ion can be created?

Answer 23

+1, +2, +3 etc

Question 24

Why are there small line surrounded main/main lines?

Answer 24

abundance of isotopes

increase of 1 mass unit on neutral molecule.

Question 25

What can a high resolution MS detect?

Answer 25

specific charge +2,+3 etc

Question 26

What is a mono-isotopic series?

Answer 26

number very similar of peaks, indicating isotopes

Question 27

What is soft ionisation?

Answer 27

ionised but the molecules don’t fall apart

Question 28

What are examples of soft ionisation techniques?

Answer 28

Electro-spray ionisation ESI

Matric-Assisted Laser Desorption Ionisation MALDI

Question 29

ESI: what is it called when the water droplets increases until explosion?

Answer 29

Rayleigh limit

Question 30

ESI: what increases charge of water droplets?

Answer 30

electron spraying capillary

Question 31

What happens at the Rayleigh limit?

Answer 31

The water molecules break up to lots of smaller particles. keep repeating.

Question 32

What happens to drop size in ESI?

Answer 32

gets smaller and smaller until gaseous ions, just ions

molecule doesn’t fragment

Question 33

Is ESI useful in macromolecules?

Answer 33

yes

Question 34

What is added to the molecule and where in ESI?

Answer 34

H+ added to basic regions, giving it a +1 charge. Increasing mass by 1.

Question 35

What are basic region?

Answer 35

N-terminal, Lys, Arg and His side chains

Question 36

What is an analyte technique?

Answer 36

MALDI

Question 37

What can MALDI be used for?

Answer 37

soft ionisation technique for larger molecule