Patent ID: 6903196

Claim:
A method of identifying a protein exposed on a luminal surface of a cell lining of a perfusible space in situ or in vivo comprising the following steps: (a) providing a cell membrane impermeable reagent comprising three domains (i) a first domain comprising a chemical moiety capable of covalently and non-specifically binding to the protein exposed on the luminal surface of a cell lining of a perfusible space in situ or in vivo, (ii) a second domain comprising a labeling domain, and (iii) a third domain situated between the first and second domains linking the first domain to the second domain by a cleavable chemical moiety, wherein the cleavable chemical moiety comprises a disulfide group, a periodate-cleavable glycol, a dithionite-cleavable diazobond, a hydroxylamine-cleavable ester, or a base-labile sulfone; (b) administering the membrane impermeable reagent into the perfusible space in an intact organ or an intact animal to react the cell membrane impermeable reagent with proteins exposed on the luminal surface of the cell lining of the perfusible space to label the lumen-exposed protein; and (c) identify a lumen exposed protein under a condition that does not denature the protein.