Voyager DP-263-S Betriebsanweisung PDF herunterladen (Seite 153)

100

101

Preparing Samples

Voyager

™

Biospectrometry

™

Workstation User’s Guide 3-23

3.1.5.3 Cation Exchange

When to use

Use this technique for non-polar proteins or DNA when you

know the sample contains only a salt contaminant. This

technique is faster than dialysis but does not remove other

contaminants.

What you need

Use 200-mesh cation exchange beads. Cation exchange

beads in the ammonium form work best for MALDI

applications.

Preparation of

beads in

ammonium form

To prepare cation exchange beads in the ammonium form:

1. Place beads in twice the bead volume of

1M ammonium acetate.

2. Leave beads in ammonium acetate overnight.

3. Remove beads, and wash with water, acetone, and then

hexane through a Buchner funnel under vacuum.

Following washing, beads can be stored indefinitely

and used as needed.

Procedure

To perform cation exchange:

1. Place about 0.1 mg (a small spatula-tip-full) of cation

exchange beads on a piece of laboratory film.

2. Add 5 to 10 µl of sample for 200-mesh cation exchange

beads. If sample quantity is limited, you can make up the

difference with deionized water.

3. Add 5 to 10 µl of matrix on top of the sample, as matrix

may also contain salt.

4. Mix by withdrawing and expelling about 20 times with a

pipet.

NOTE: The volume of sample decreases as the beads

absorb water.

5. Allow the beads to settle for 30 seconds.

6. Remove the supernatant with a clean pipet tip and spot on

the sample plate.

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