Biological Condensate\nGrowth: Examining the Impact\nof Solute Crowder on Size Expansion

Biological condensation refers to the formation of micrometer-sized\nor smaller condensates by biological macromolecules, a process often\ninfluenced by the crowded cellular environment. Poly(ethylene glycol)\n(PEG) is commonly used to mimic cellular crowding, and its ability\nto reduce the critical nucleation concentration has been well established.\nHowever, its impact on condensate size has been less explored. This\nstudy investigates how PEG affects the size of condensates formed\nbetween protein TNP1 and DNA. Our experimental findings show that\nPEG molecules increase condensate size. Notably, at equal mass concentrations\nof PEG400, PEG3350, and PEG10000, longer PEG molecules have a much\ngreater effect on condensate expansion. Computational simulations\nfurther reveal that longer PEG molecules enhance protein–DNA\ncondensation more effectively and contribute to shaping the condensates\ninto regular forms. Overall, our study provides key insights into\nhow crowding factors influence the size and shape of colloidal growth.