Dissertation Defence: Qualitative insight into uronylated human milk oligosaccharides and mucin derived non-invasively from the neonatal gut
January 23 at 1:00 pm - 5:00 pm
Nitin, supervised by Dr. Wesley Zandberg, will defend their dissertation titled “Qualitative insight into uronylated human milk oligosaccharides and mucin derived non-invasively from the neonatal gut” in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemistry.
An abstract for Nitin’s dissertation is included below.
Examinations are open to all members of the campus community as well as the general public. Registration is not required for in-person exams.
ABSTRACT
Glycosylation—the covalent attachment of one or more carbohydrate residues to proteins—is a key post-translational modification that expands the information complexity of cells. The resulting glycans, also called oligosaccharides, form a dynamic and cellular microenvironment-dependent repertoire known as the glycome. The protein that protects the gut, called mucin-2 (MUC2) is among the most heavily glycosylated in nature, bearing thousands of unique glycans that play key roles in acquiring and maintaining a healthy community of gut bacteria called a microbiome. In early life, one of the most functionally-important sources of oligosaccharides is human milk which contains a diverse array of free glycans (i.e. these are not linked to proteins) that bear a striking chemical resemblance to MUC2-borne glycans. Critical roles of HMOs in infant health include shaping gut microbiome composition, modulating immune responses, and supporting neurodevelopment. This thesis longitudinally investigated the structural and functional diversity of glycans in early life, with a focus on free human milk oligosaccharides (HMOs) and protein-linked infant gut-derived mucin (MUC2) O-glycans. Particular attention was given to sulfated HMOs, an underexplored subclass with potential immunomodulatory properties. This work reports, for the first time, the identification of uronic acid-containing HMOs and O-glycans non-invasively derived from infant MUC2. To support this investigation, a robust analytical workflow was developed using porous graphitized carbon (PGC) high-performance liquid chromatography coupled with electrospray ionization tandem mass spectrometry (HPLC-ESI-MSMS). Special emphasis was placed on optimizing the collision induced dissociation (CID) conditions in negative ESI mode, as acidic modifications such as sialylation and sulfation increase the energy required for effective fragmentation. Stepwise energy ramping revealed that the formation of diagnostic bond cleavages was influenced by both glycan structure and collision energy. This approach enabled the structural characterization of numerous sulfated HMOs, including a previously unreported subclass containing glucuronic acid (GlcA), further expanding the known glycan repertoire in early life.
