As an essential component of bioactive substances (e.g. immunoglobulins, enzymes, hormones) and cell membranes or walls (e.g. immune cells, bacterial and viral cells), glycan or carbohydrate is widely distributed in various tissues of human body involving in many fundamental bio-processes, such as energy supply, biological recognition, transportation, cell-cell adhesion, etc. Also, these carbohydrates may serve as useful targets or biomarkers in a series of human diseases diagnostics and therapeutics.