Sentence:  The precipitate was washed twice with an 80 % saturated solution of * * f , dissolved in a small quantity of 0.1 M neutral phosphate buffer , dialyzed against cold distilled water till free from ammonium ions , and <WSD>lyophilized</WSD> using liquid nitrogen . 
Meaning of the word marked with <WSD> tags:  to dry (blood, serum, or tissue) by freezing in a high vacuum