Those originally employed were based either on the fusion of the PCE to a tumour specific antibody (Antibody-Directed Prodrug Therapy, ADEPT) or on the delivery of the gene encoding the PCE using viral or non-viral vectors (Gene-Directed Enzyme Prodrug Therapy, GDEPT).
Urea is widely used in fertilizers as a source of nitrogen and is an important raw material for the chemical industry. Friedrich WÃ¶hler's discovery in 1828 that urea can be produced from inorganic starting materials was an important conceptual milestone in chemistry.
All NPNâs generate ammonia in the rumen which enters the liver and finally converted to urea. 2.1. Urea the most common NPN Urea is the principle commercial source of NPN for use in ruminant diets. Urea is a simple compound that contains 46.7 percent of nitrogen compared to 16 percent for most proteins.When plant protein feeds, such as soybean meal, are high priced, it is economical to use urea as a protein supplement in ruminant rations.Urea, the cheapest solid nitrogen source, is a white crystalline water-soluble powder that is used as a fertilizer.rea is a simple compound that contains 46.7 percent of nitrogen compared to 16 percent for most proteins. When plant protein feeds, such as soybean meal, are high priced, it is economical to use urea as a protein supplement in ruminant rations.