Chemical structure of lipid A as found in E. coli. Lipid A is a lipid component of an endotoxin held responsible for the toxicity of gram-negative bacteria. It is the innermost of the three regions of the lipopolysaccharide (LPS), also called endotoxin molecule, and its hydrophobic nature allows it to anchor the LPS to the outer membrane.
watermark - Computer Definition. 1  A translucent mark or image in paper produced by pressing the paper in a mold or on a processing roll during the manufacturing process. The watermark is visible when the paper is held to a light. A watermark is used as a sign of authenticity in order to make the counterfeiting of currency and postage stamps more difficult, for example.
Definition of bookmark for English Language Learners : something (such as a piece of paper) that is put in a book to show the place where you stopped reading computers: something (such as a menu entry or icon) that allows you to go quickly and directly to something (such as an Internet site) that you have seen before