Direct analysis of reversed-phase high-performance thin layer chromatography separated tryptic protein digests using...

Area of Science:

• Analytical Chemistry
• Biochemistry
• Mass Spectrometry

Background:

• High-performance thin-layer chromatography (HPTLC) is a chromatographic technique used for separating and analyzing compounds.
• Mass spectrometry (MS) is a powerful analytical technique for determining the mass-to-charge ratio of ions.
• Combining HPTLC with MS offers a sensitive approach for peptide and protein analysis.

Purpose of the Study:

• To develop and evaluate a method for sampling, ionizing, and detecting tryptic peptides separated on HPTLC plates using liquid microjunction surface sampling probe electrospray ionization mass spectrometry (LM-SPS-ESI-MS).
• To assess the feasibility of this technique for protein identification and sequence coverage determination.
• To investigate the influence of protein size and sample loading on the achieved sequence coverage.

Main Methods:

• Tryptic digests of five proteins (cytochrome c, myoglobin, beta-casein, lysozyme, and bovine serum albumin (BSA)) were separated on reversed-phase HPTLC (RP-8 and RP-18) plates.
• Developed HPTLC lanes were analyzed using a liquid microjunction surface sampling probe electrospray ionization mass spectrometry (LM-SPS-ESI-MS).
• Full scan and data-dependent tandem mass spectrometry (MS/MS) were acquired to identify peptides and determine protein sequence coverage.

Main Results:

• The LM-SPS-ESI-MS method successfully enabled the detection and verification of tryptic peptide distributions on HPTLC plates.
• Data-dependent tandem MS/MS provided protein identification and sequence coverage information.
• Highest sequence coverages were achieved for smaller proteins like cytochrome c (62.5%) and myoglobin (58.3%) on RP-8 plates.
• Some peptide band overlap was observed, and larger proteins (beta-casein, BSA) resulted in lower sequence coverage, especially when loaded in lower amounts.

Conclusions:

• LM-SPS-ESI-MS is a viable technique for analyzing tryptic peptides separated by HPTLC, facilitating protein identification.
• The separation efficiency on HPTLC plates impacts sequence coverage, with better separation leading to higher coverage.
• Protein size and sample loading amount are critical factors affecting the success of this analytical approach.