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Tandem Mass Spectroscopy for Structural Biology

An Alternative to Traditional Sequencing Techniques

! MS Techniques for the Specific Fragmentation of Peptides

Sustained off-resonance irradiation collision-induced dissociation (SORI-CID) Infrared multiphoton dissociation (IRMPD) Blackbody infrared radiative dissociation (BIRD) Surface-induced dissociation Electron capture dissociation (ECD) y

CID is used to induce fragmentation of gas- phase ions via inelastic collisions of translationally excited ions with neutral atoms or molecules. Fragmentation of amide bonds to produce N-terminal b and C-terminal y ions is observed also in IRMPD and BIRD

H2N

R1

O

H N

R2

  • O

    R3

N H

O

H

H N

N H

R4

R3

H N

  • O

    R4

  • O

    R5

N H

O

O

OH

N H

R5

O

O H y 3

b

R2

H N

O

R1

NH2

b2

O

SORI-CID fragment ion spectrum of human luteinizing hormone-releasing hormone using 7 Tesla FT-ICR MS. All amide bonds, except the two closest to the N- and C-termini, were cleaved in this 10-residue peptide, resulting in a sequence tag of six amino acid residues from the y ion series

The Ion Mobility / Ion Chromatography Method

Structural Information of the Gas Phase Conformation of Molecules or Non-Covalent Clusters

! Ion Mobility-Mass Spectroscopy

gaseous

MS

drift

MS

ion source

#1

tube

#2

Ion mobility (K) is defined by an ions ability to travel through a buffer gas under weak uniform electric field to an equilibrium drift velocity.

Collision cross section (!) is determined by ion geometry but also interaction between ion and the buffer gas. (ie. ions with compact structures have small cross sections and large ion mobility)

K=

3z

2"

16N

µkBT

detector

1/2

1 !

Ions are separated by size in a sort of "ion chromatography."

8

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