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Mass Spectrometry
 

SAMPLE SUBMISSION

 


SAMPLE CONCENTRATION
These are guidelines.  Detection of a sample is largely dependent uponto how well a molecule ionizes.  Excess sample concentration may overwhelm the matrix and lead to a suppression of ionization.

Sample Type

Peptide

500Da – 5000Da

1-10pmol/ul (1-10uM)

Peptide/Proteins

5kDa – 25kDa

5-25pmol/ul (5-25uM)

Protein

25kDa – 100kDa

25-100pmol/ul (25-100uM)

DNA/RNA

500Da – 3000Da

1-10pmol/ul (1-10uM)

DNA/RNA

>3000Da

10-100pmol/ul (10-100uM)

Small Molecules

100Da – 500Da

1pmol/ul (1uM)

Polymer

500Da – 5000Da

Inquire
** All samples submitted to PAN are discarded after 2 weeks.
Volume of 10ul is generally enough for workup.


SOLVENTS/BUFFERS
We recommend submitting samples in water, acetronitrile (ACN), 0.1% TFA.  Volatile solvents are acceptable (ie methanol, ethanol, etc).  Though, MALDI-TOF is tolerant of potentially interfering solvents/buffers, but we recommend keeping the solvent/buffer concentrations to a minimum (see table below).  Excess solvent/buffer concentration can lead to a suppression of ionization.

Solvent/Buffer

Tris buffer

<100mM

Phosphate buffer

<50mM

NaCl

<50mM

Sodium Acetate

<50mM

Sodium Azide

<10mM

HEPES

<100mM

TEAA

<50mM

Glycerol

<1.0%

Detergent (ie.Triton-X, SDS)

<0.1%

We provide ziptip clean up of samples to remove excess buffer/solvent. Please contact us if you have any concerns about your sample buffer conditions.

 


MATRIX (for prespotted samples)
Spot 1ul of matrix onto silver MALDI plate, add 1ul of sample to matrix spot, allow to air dry. 

Sample Type

Matrix

Recipe

Peptide (<5000Da)

DHB
2,5 dihydroxybenzoic acid

10mg/ml
Water

Peptide (<5000Da)

CHCA
a-cyano-4-hydroxycinnamic acid

10mg/ml
50%ACN/0.1%TFA

Protein (5kD – 100kD)

SA
sinapinic acid

10mg/ml
50%ACN/0.1%TFA

DNA/RNA

HPA
3-hydroxypicolinic acid

9: HPA-50mg/ml 50%ACN
1: Ammonium tartrate-50mg/ml water

A good spot should look lightly cloudy. If the spot looks clear or glassy this could indicate the sample is too concentrated. If the spot is heavily precipitated (i.e. very white) this could indicate too much salt in the spot.  To overcome these problems, one can dilute the sample and/or remove salts using a ziptip and respot. Also, the PAN Facility has a variety of other matrix on hand, if you would like to test them out please contact us.

 


Common Adducts/Modifications

Adduct

Mass (Da)

sodium 22.9
potassium 39.0
oxidation 15.9
acetylation 42.0
formylation 27.9
phosphorylation 79.9
trityl

242

dimethoxytrityl (DMT)

302

depurination

-150

If you see a peak that is half the mass of the M+, this is the doubly-charged species of M+.
If you see a peak that is double the mass of the M+, this is the dimer of the M+.