PHYSIOLOGICAL CHEMISTEY 309 



acetic acid, the precipitate when formed being soluble in excess. They are 

 represented by the mucoid of ovarian cysts, the ovo-mucoid of white of egg, and 

 bodies (sometimes termed chondro-proteids) which occur along with collagen in 

 cartilage. These last on decomposition with an acid yield protein and a reducing 

 body called chondroi tin -sulphuric acid, which can further be decomposed to 

 yield chondrosin, a body containing nitrogen, but more strongly reducing than 

 dextrose. This body can still further be decomposed to glucosamine, the usual 

 carbohydrate moiety of the mucins. Of this the mucins contain about 30 %. 



fCH 2 (OH) 

 CHOH 



Formula of I ( J HOH 

 Glucosamine. l^jj 



CH(NH 2 ) 



J3 



The Nucleo-proteins. These consist of protein in combination with 

 nuclein, and form the chief constituent of the nuclei of cells. Nuclein 

 itself is a compound of protein, with an organic acid known as nucleic 

 acid. 



PREPARATION OF NUCLEO-PROTEIN. 



METHOD I. A cellular organ, such as the thymus or pancreas, is 

 minced and macerated overnight with water made faintly alkaline with 

 caustic soda or ammonia. The extract is then strained through muslin, 

 litmus added, and then weak acetic acid. When the reaction becomes 

 faintly acid, a copious precipitate of nucleo-protein occurs. The nucleo- 

 protein is filtered off and dissolved in weak alkali (1 % sodium carbonate). 



METHOD II. Demonstration. The minced organ is pounded in a 

 mortar, with an equal amount of solid NaCl. Upon throwing the mass 

 into excess of water in a tall cylinder, the nucleo-protein rises as a 

 stringy mass to the top of the water. This is collected and dissolved in 

 1% sodium carbonate. 



EXPERIMENT XII. Some of this alkaline solution is supplied 



(1) Add acetic acid white precipitate soluble with difficulty in 



excess. (Cf. mucin, which is insoluble, and caseinogen, 

 which is readily soluble.) 



(2) Perform the protein colour tests. 



(3) Ascertain how it is " salted out." 



Demonstration. The precipitate of nucleo-protein has been 

 digested with pepsin hydrochloric acid for twenty-four hours. The 

 protein has become converted into peptone the liberated nuclein has 

 fallen down as a brown sediment. 



