MALDI

MALDI stands for Matrix Assisted Laser Desorption Ionization. This MALDI-TOF/TOF can be used for high and low resolution mass spectrometry of small molecules, peptides, proteins, metabolites, and polymers. It is also capable of producing MS/MS fragmentation spectra for structural characterization or peptide sequencing. Polymer analysis is possible using Polymerix software. Flex-imaging and SCiLS software allow for fast MS analysis of aluminum-backed TLC plates and MALDI imaging, including tissue samples. It uses a Smartbeam II UV (355 nm) laser for ionization.

Parameters: unlimited mass range; normally used for molecules above 300 amu; usually only observe singly charged molecules, but +/-2 and +/-3 are possible.

This instrument often produces [M+H]⁺ ions in positive mode and [M-H]^- ions in negative mode. However, other ions may also be observed- such as Na+, K+, Li+, Ag+... - if they are highly abundant in the sample or are added to improve ionization. This can be very useful for polymer ionization.

Watch this video on the theory of MALDI-TOF.

To learn more about this instrument, see Bruker's autoflex maX brochure and this overview of the instrument's capabilities.

Pricing

Please see the MALDI self-service page for more information.

MALDI Lab Hours

The MALDI lab is generally open 8-5 M-F.

For after hours access, your PI will need to send a request for MBB building access and MBB 1.420 access to Maria Person at mperson@austin.utexas.edu.

Training

This instrument is available as an open access / self-service instrument after initial training.

Contact the Proteomics Facility to schedule MALDI training.

Here are their instructions for self-service training.

After training, please follow these MALDI protocols from the Proteomics Facility.

MALDI Target Plate

If you are going to be using the MALDI a lot, it is probably worth it for your lab to purchase your own MALDI target plate. This plate has 384 target spots, so you can prepare a lot of samples in advance and run them all quickly in one instrument session. The Bruker Daltonics part number for the standard polished steel plate is 8280781. The cost should be around $450 if you get a quote from Bruker directly. It is available through Fisher on the UT marketplace, but may be more expensive.

Target Plate Template

We find it useful to keep a chart of which spot has which sample on it. You can download our target plate template and record your initials and sample name on each grid position. Before running samples, we prepare the plate with a calibration spot in the middle of every 3x3 square block. In this way, you can nearly always have a calibrant spot next to your sample, to increase mass accuracy.

Sample Preparation

-Watch this video to learn about MALDI sample preparation and spotting.

-Here is the Sigma Aldrich website on MALDI matrix selection and sample preparation.

-Here is a ZipTip Protocol to remove salts from your sample before MALDI.

Analyzing Polymers

-Here is an overview of the capabilities of Polymer Analysis by MALDI-TOF from Bruker.

-Here is an extensive literature review on the analysis of polymers by MALDI.

Polar polymers such as PEGs and PPGs tend to be very straightforward to analyze. Slightly polar polymers such as polystyrene are more difficult (you often need to add silver ions, which can form adducts with the phenyl rings). Even non-polar polyethylene has been analyzed, but is extremely difficult to ionize. As always, check the literature to see how other researchers have analyzed the type of polymer that you are interested in.

-NIST has a synthetic polymer MALDI recipes database that may help you determine which matrix and salt additive to use.

-Here are some tips for getting started analyzing polymers with MALDI.

-Here is a very useful introduction to the Polymerix Software.