Glycoprotein profiling by electrospray mass spectrometry.

Area of Science:

• Analytical Chemistry
• Biochemistry
• Glycoscience

Background:

• Glycoproteins exhibit significant microheterogeneity due to diverse glycosylation.
• Ovine luteinizing hormone alpha-subunit (oLHalpha) is biologically relevant and displays extensive glycoform variation.
• Site-specific glycosylation impacts protein function, such as receptor binding affinity.

Purpose of the Study:

• To compare different electrospray mass spectrometry (MS) methods for site-specific glycoprotein analysis.
• To characterize the glycoforms present at the Asn(56) site of oLHalpha.
• To evaluate the utility of various MS instruments and scanning modes for glycopeptide profiling.

Main Methods:

• Electrospray ionization mass spectrometry (ESI-MS) was employed.
• Analysis was performed using a quadrupole ion trap, triple quadrupole, and quadrupole time-of-flight (qTOF) mass spectrometer.
• Neutral loss and precursor ion scanning techniques were utilized alongside standard MS methods.

Main Results:

• Over 20 unique glycoforms were identified at the Asn(56) glycosylation site of oLHalpha.
• All three MS instruments successfully profiled the glycopeptide composition.
• The qTOF instrument demonstrated the lowest sample consumption among the compared systems.

Conclusions:

• Site-specific analysis of complex glycoproteins like oLHalpha is feasible using various MS techniques.
• The characterized glycoforms at Asn(56) are critical for understanding ligand-receptor interactions.
• Comparative MS analysis provides valuable insights into glycoprotein heterogeneity and analytical method performance.