Figure 1.
Schematic of the Nano-LC MALDI-MS droplet interface device.
(a) Water-in-oil droplets are generated at a microfluidic T-junction having two aqueous inlets, one oil inlet and an outlet channel. The LC effluent is transferred into the microfluidic device via a fused silica capillary. The second aqueous inlet is used to introduce MALDI matrix in a controlled manner. LC effluent and MALDI matrix meet at the T-junction and are delivered into the oil stream where they are broken into droplets due to shear forces. (b) The deposition probe consists of a 200 µm i.d. Teflon tubing and an oleophilic membrane. Droplets generated in the interface device are transported to the MALDI target via the Teflon tubing. The PTFE membrane extracts the continuous oil phase leaving the aqueous droplet suspended at the tip of the tubing. This droplet is then directly spotted onto the MALDI target by contact deposition.
Figure 2.
Effect of FC-40 oil on the crystallisation of HCCA.
(a) Typical crystal surface formed using 1 µm of the matrix prepared in the dried drop format, (b) Addition of 0.5 µm of FC-40 oil onto the top left hand side well, (c) Addition of 0.5 µm dye loaded matrix onto the same well after 3 seconds, (d) after 5 seconds, (e) after 7 seconds, (f) after 10 seconds, (g) after 13 seconds and (h) after 20 seconds.
Figure 3.
Sinapinic acid matrix crystallisation using the dried drop and droplet deposition method.
(a) Matrix without oil, (b) Matrix in the presence of FC-40 oil. (c) BSA and matrix in the absence of FC-40 oil (d) BSA and matrix in the presence of FC-40 oil and (e) matrix crystals formed when a sample is spotted using the droplet deposition probe.
Figure 4.
MALDI MS spectra of BSA, Cytochrome C and Lysozyme.
(a–c) Spectra obtained from samples spotted using the traditional dried drop technique. (d–f) Spectra obtained from samples spotted using the microfluidic interface and deposition probe. Proteins were prepared at stock concentrations and diluted 1∶1 in a Sinapinic acid matrix prepared at a concentration of 12.5 mg/ml in 45% acetonitrile, 45% ethanol and 10% (0.1%) trifluoroacetic acid.
Figure 5.
LC–MALDI MS analysis of peptides generated from Trypsin digested Cytochrome C.
(a) The LC separation profile of the Cytochrome C digest. (b) and (c) detail the mass spectrometry results using a commercial spotter and using the droplet deposition probe respectively. The mass spectrometry results were plotted as relative peptide abundance versus the spot number. Table S3 compares the results from both spotters.
Figure 6.
LC–MALDI MS analysis of peptides generated from Trypsin digested Bovine Serum Albumin.
(a) The LC separation profile of the BSA digest. (b) and (c) detail the mass spectrometry results using a commercial spotter and using the deposition probe respectively. The mass spectrometry results were plotted as relative peptide abundance versus the spot number. Table S4 compares the results from each spotter and lists the mono-isotopic mass of each peak.