Interactions and Dissociation Constants of Galactomannan Rendered Cellulose Films with Concavalin A by SPR Spectroscopy

Interactions of biomolecules at interfaces are important for a variety of physiological processes. Among these, interactions of lectins with monosaccharides have been investigated extensively in the past, while polysaccharide-lectin interactions have scarcely been investigated. Here, we explore the adsorption of galactomannans (GM) extracted from Prosopis affinis on cellulose thin films determined by a combination of multi-parameter surface plasmon resonance spectroscopy (MP-SPR) and atomic force microscopy (AFM). The galactomannan adsorbs spontaneously on the cellulose surfaces forming monolayer type coverage (0.60 ± 0.20 mg·m-2). The interaction of a lectin, Concavalin A (ConA), with these GM rendered cellulose surfaces using MP-SPR has been investigated and the dissociation constant KD (2.1 ± 0.8 × 10-8 M) was determined in a range from 3.4 to 27.3 nM. The experiments revealed that the galactose side chains as well as the mannose reducing end of the GM are weakly interacting with the active sites of the lectins, whereas these interactions are potentially amplified by hydrophobic effects between the non-ionic GM and the lectins, thereby leading to an irreversible adsorption.

Antibody Profile of Colostrum and the Effect of Processing in Human Milk Banks: Implications in Immunoregulatory Properties

BACKGROUND

When feeding preterm infants, donor milk is preferred if the mother's own milk is unavailable. Pasteurization may have detrimental effects on bioactivity, but more information is needed about its effects on the immunological compounds. Research aim: This work has two main aims: evaluate the antibody profile of colostrum and study the quantitative variations in the antibodies' level and specific reactivity after undergoing Holder pasteurization. The authors focused on immunoregulatory components of colostrum (antidietary antibodies and TGF-β2) in the neonatal gut.

METHODS

This is a descriptive cross-sectional study of a convenience sample of 67 donated colostrum samples at different days after delivery, both raw and pasteurized. Antibody profiles were analyzed at different times during breastfeeding, and total and specific antibodies (IgM, IgA, and IgG subclasses) were compared with tetanus toxoid and ovalbumin using enzyme-linked immunosorbent assay. The processing effect on total and specific antibodies, as well as TGF-β2, was evaluated by paired analyses.

RESULTS

No variations in immunological compounds were observed throughout the colostrum stage. The TGF-β2, antibodies' concentrations, and antibodies' specific reactivity after pasteurization did not vary significantly as days of lactation varied. Changes in antibody levels were dependent on isotype and IgG subclass, and IgG4 showed remarkable resistance to heating. Moreover, the effect of the pasteurization on specific reactivity was antigen dependent.

CONCLUSION

The supply of relevant immunological components is stable throughout the colostrum stage. The effects of pasteurization on antibodies depend on isotype, subclass, and specificity. This information is relevant to improving the immunological quality of colostrum, especially for preterm newborns.