Mucins are major components in tear fluid and apical cell membranes on the ocular surface epithelia. Structurally, they are composed of tandem repeat domains containing heavily O-glycosylated serine and threonine residues. More than a half of its weight consists of O-glycans, which has hydrophilic nature (Fig. 1). The heavy glycosylation of mucins is believed to impart a highly negative charge and a hydrophilicity that provides a barrier to pathogen adherence and penetrance into the epithelium (Fig. 2). Alteration in both secreted and membrane-associated mucins occur in drying ocular surface diseases (Fig. 2). At the ocular surface, three types of mucins are present. The large gel-forming mucin MUC5AC is expressed by conjunctival goblet cells. Some cells of the lacrimal gland acini express the small soluble mucin MUC7. The corneal and conjunctival epithelia express the membrane-associated mucins MUCs 1, 4, and 16 (Fig. 2).
Fig. 2 Mucins expressed around corneal surface, and barrier function by tear mucins
For determination of mucin content in tear
Mucins are family of high molecular (1000 kda-10000 kda) and heavily glycosylated protein. Mucin domains within the protein core are rich in threonine and serine. The reducing ends of sugar chain N-acetylgalactosamin (GalNAc) are linked to those amino acids by the post-translational O-glicosylation (Fig.1). Mucin content can be measured as reducing ends of sugar chain after β -eliminated by diluted alkali. Reducing ends of sugar chain react at high temperatures with 2-cyanoacetamide (2-CAN) to produce intensely fluorescent condensate.
This product is designed for the measurement in fluorescence plate readers (96 well plates).
When using Fluorescence plate reader, it can measure 100 samples.
When you measure with a light spectrophotometer, please use it with a microcell.
Measurement of tear mucin
The recommended measurement wavelengths are 336 nm for Ex and 383 nm for Em, but you might not be able to measure the fluorescence wavelength when fluorescence plate leader with interference filter system is used. In such a case, please shift the fluorescent wavelength to longer.
Tear Mucin Assay Kit (O-Glycan Assay Method)
To be used for research only. DO NOT use for human gene therapy or clinical diagnosis.
Mucin Assay Kit[PDF]