The present application relates to a method of making liposomes having membrane proteins incorporated therein, the method comprising: providing the membrane protein in solution; providing a solution of preformed liposomes; and incubating the mixture. Prior to the step of providing a solution of preformed liposomes, the liposomes are formed by combining a mixture of phospholipids with a solution of at least one type of unsaturated fatty acid. The methods of the present invention further relate to the method of making a reagent comprising tissue factor reconstituted into preformed liposomes. The method of the present invention for making a tissue factor reagent comprises: providing tissue factor in solution; providing a solution of preformed liposomes comprising a mixture of phospholipids and at least one type of unsaturated fatty acid; and incubating the mixture.