The disclosure relates to a conjugate comprising a membrane anchoring agent, polyethylene glycol effective and a functional molecule that is in increasing the lifespan of sperm in the female reproductive tract, wherein the functional molecule is attached to the polyethylene glycol by an attachment group. Example conjugates are shown in the abstract figure. The functional molecule may be catalase, glutathione, CD55, CD59, CD73, DNaseI or SPAM1. The membrane anchoring agent may be a lipid, such as cholesterol, diacylglycerolipids, dialkylglycerolipids, glycerophospholipids, sphingosine derived diacyl- and dialkyl- lipids, ceramide, phosphatidate, phosphatidyl choline, phosphatidyl ethanolamine, phosphatidyl serine, phosphatidyl inositol or phosphatidyl glycerol. The attachment group may be ester amine reactive groups, maleimide, vinyl sulfone, iodoacetamide, orthopyridyl disulphide, hydrazide, benzotriazole, succinimidyl carbonate or succinimidyl active esters based on priopionic and butanoic acids. The disclosure also relates to a method for preparing a composition for use in artificial insemination or in vitro fertilization using sperm and the conjugate.
