PAN_MSPEC

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	Mass Range	Concentration
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	Concentration
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.

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+.