A polymer having the general formula: HOCH₂(CH₂OCH₂)XCH₂OH and available in a range of molecular weights from ca 1000 to ca 6000. PEG 4000 and PEG 6000 are commonly used to promote cell or protoplast fusion, and to facilitate DNA uptake in the transformation of organisms such as yeast. PEG is also used to concentrate solutions by withdrawing water from them.