Structural analysis of endothelial heparan sulfate isolated from Hs2st^f/fTie2Cre⁺ mice. (A) Lung endothelial cells were metabolically labeled with ³⁵SO₄, and purified [³⁵S]heparan sulfate was digested to completion with a combination of heparin lyases I, II, and III. The resulting disaccharides were analyzed by liquid chromatography. The 4-letter disaccharide structure codes (DSC) describe the composition of each recovered disaccharide.⁴⁹  In DSC, the D designates a Δ^4,5-unsaturated uronic acid and the absence or presence of a 2-O-sulfate group is designated by 0 or 2, respectively. The N-substituent of the glucosamine unit is designated A or S for acetate or sulfate, respectively. The absence or presence of 6-O-sulfate groups on the glucosamine units is designated by the numerals 0 or 6, respectively. (B) The number of [³⁵S]sulfate groups at each position was determined and expressed as a percentage of the total. (C) Endothelial cells were metabolically labeled with ³⁵SO₄, and purified [³⁵S]heparan sulfate was digested with heparin lyase III to completion. The resulting oligosaccharide fragments was resolved by gel filtration on a Bio-Gel P-10 column. dp indicates degree of polymerization (refers to the size of the oligosaccharide in the individual peaks).