MS Principles

8/13/2019 MS Principles

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Dwight Glenn Jr.

Briana Halbert

MS Principles


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What is Mass Spectroscopy?

Mass Spectrometry (MS) is a technique formeasuring the mass, (MW) of a molecule.

From this information it is possible to gain

structural information about a molecule by

measuring the mass fragments produced when

molecules are broken apart

Mass Spectrometers have 3 basic parts:

Ionization source, Mass analyzer, and Detector


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Mass Spectrometry Needs Ionization-how the protein is injected in to the

MS machine

Separation-Mass and Charge is determined

Activation-protein are broken into smallerfragments (peptides/AAs)

Mass Determination-m/z ratios are

determined for the ionized protein

fragments/peptides


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Mass spectrometers near me g t tu e

Reflector Time Of Flight tube

detector

reflector

ion source

ion source

detector

time of flight

time of flight

Time of flight (TOF) (MALDI)

Measures the time required for ions to fly down the lengthof a chamber.

Often combined with MALDI (MALDI-TOF) Detections frommultiple laser bursts are averaged. Multiple laser

Tandem MS- MS/MS

-separation and identification of compounds in complexmixtures

- induce fragmentation and mass analyze the fragment ions.

- Uses two or more mass analyzers/filters separated by a

collision cell filled with Argon or Xenon

Different MS-MS configurations

Quadrupole-quadrupole (low energy)

Magnetic sector-quadrupole (high)

Quadrupole-time-of-flight (low energy)

Time-of-flight-time-of-flight (low energy)


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How does a mass spectrometer work?

Ionization

method

MALDI

Electrospray(Proteins must be

charged and dry)

Mass analyzer

MALDI-TOF

MW

Triple Quadrapole AA seq

MALDI-QqTOF AA seq and MW

QqTOF AA seq and protein modif.

Create ions Separate ions Detect ions

Mass

spectrum

Database

analysis


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Three Components:

This is a glimpse to how a mass spectrometer worksstarting from the sample to the data on the display

screen.


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Mass Spec Principles

Ionizer

Sample

+_

Mass Analyzer Detector


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MS


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Video

http://www.youtube.com/watch?v=J-wao0O0_qM
http://www.youtube.com/watch?v=J-wao0O0_qMhttp://www.youtube.com/watch?v=J-wao0O0_qMhttp://www.youtube.com/watch?v=J-wao0O0_qMhttp://www.youtube.com/watch?v=J-wao0O0_qM


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What happens inside the

spectrometer?

During an experiment a small amount of a sampleis vaporized into the ionization source.

The energy of the electron beam will strike the

organic molecule and will dislodge a valence

electron

This dislodgement produces a cation radical


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Cation Radical

Cation because the molecule has lost an

electron and has a positive charge

Radical because the molecule now has an

odd number of electrons


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Next Step

Electron bombardment transfers so much energythat most of the cation radicals fragment after

they are formed.

This means that they break into smaller pieces

because a bond has been weakened by loss of

an electron and some retain their positive charge

while some are neutral.

These fragments then flow through a curved pipe

in a strong magnetic field


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What is the data?

In the pipe there are different paths andaccording to the mass-to-charge ratio (m/z) it will

determine which fragments go where. Lower

mass charge ratio is deflected more.

Neutral fragments (radical) are not deflected by

the magnetic field and are then lost on the walls

of the pipe.

Positively charged fragments (cation) are sorted

by the mass spectrometer onto a detector which

records them as peaks at various (m/z) ratios


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How to read the data:

Since the number of charges z on each ion isusually 1, the value of m/z for each ion is its

mass.

The mass spectrum of a compound is typically

presented as a bar graph

(m/z) is on the x-axis

Relative abundance is on the y axis.


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How to read the data Some important peaks to remember: The base peak is the peak assigned to the intensity of 100%

It is also the tallest peak, is the most stable cation


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How to read the data The next peak is the parent peak

This peak corresponds to the unfragmented cation radical

This is also known as the molecular ion


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What is it?

Since the parent peak has a m/z of 44 that meansthat the MW of the substance will equal 44.

The mass spectrum shown was for propane C3H8

has a molecular weight of 44


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Video

http://www.youtube.com/watch?v=tOGM2gOHKPc&NR=1&feature=endscreen
http://www.youtube.com/watch?v=tOGM2gOHKPc&NR=1&feature=endscreenhttp://www.youtube.com/watch?v=tOGM2gOHKPc&NR=1&feature=endscreenhttp://www.youtube.com/watch?v=tOGM2gOHKPc&NR=1&feature=endscreenhttp://www.youtube.com/watch?v=tOGM2gOHKPc&NR=1&feature=endscreen


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Question:What is mass spec used for.


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Answer:

Measuring the mass, (MW) of a

molecule


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Question

The base peak in a mass spectrum represents

(a) the most stable radical

(b) the most stable alkene

(c) the most stable cation(d) the molecular ion


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Answer

C. the most stable cation

MS Principles

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