Biology Reference
In-Depth Information
(ITO) coated glass slides and fi x the sections by thaw-mounting.
By touching the opposite glass side with a fi ngertip for ca 20-30 s
the ice in the section is melted and evaporated.
4. Transfer the ITO slides with the sections into a desiccator for
0.5-1.0 h until they are completely dried. The time until com-
plete dryness varies and is longest for the high water content
tissues (roots). Alternatively, for low water containing samples,
the drying step can be skipped.
5. Use whiteout solution to place marks close to the samples for
defi nition of sample position in the fl exImaging software
before starting the measurement run (
see
Subheading
2.1
,
item 5f
).
6. Capture an optical image with a slide scanner or a stereomicro-
scope (e.g., Leica MZ6, Wetzlar, Germany) connected to a
digital camera (AxioCam ICc1, Zeiss, Jena, Germany) or a
similar image acquisition system (
see
Note 1
).
4.2 Matrix
Deposition for
MALDI-MSI
of Small Molecules
The following procedures have been optimized for the automated
deposition of matrix onto cryo-sections using the ImagePrep
device (Bruker Daltonics GmbH, Bremen, Germany;
see
Note 2
).
1. Fill the matrix vial with pure methanol and set the global spray
power adjustment for the instrument as described in the
ImagePrep manual.
2. Insert the slide with the dried sample into the ImagePrep
instrument and adjust slide position on the small elevation in
the way that the light sensor isn't covered by a section. Fill an
appropriate amount of matrix solution (7-8 ml) into the reser-
voir of the spraying device.
3. Apply matrix solutions via sensor-controlled vibrational vapor-
ization, utilizing the ImagePrep device (Bruker Daltonics
GmbH) as per the manufacturer's instructions (
see
Note 6
).
Different spray protocols specifi c for the particular matrices are
provided.
4. Immediately after matrix application clean the spray device
with methanol.
4.3 MALDI-MSI
Measurement
of Small Molecules
Methods are described for Bruker ultrafl eXtreme instrumentation
(Bruker Daltonics GmbH), but are generally applicable for Bruker
MALDI-TOF instruments.
1. Fit the freshly prepared slides into a Slide Adapter II MALDI
target and introduce the adapter into the source of the MS
instrument.
2. Select the required fl exControl method. For small molecule's
MSI measurement select an
m/z
range of 80-1,300 and a sample
