Polyethylene Glycol 20k. Does It Fluoresce?

Abstract

Polyethylene glycol (PEG) is a polyether compound commonly used in biological research and medicine because it is biologically inert. This simple polymer exists in variable chain lengths (and molecular weights). As they are devoid of any contiguous π-system, PEGs are expected to lack fluorescence properties. However, recent studies suggested the occurrence of fluorescence properties in non-traditional fluorophores like PEGs. Herein, a thorough investigation has been conducted to explore if PEG 20k fluoresces. Results of this combined experimental and computational study suggested that although PEG 20k could exhibit "through-space" delocalization of lone pairs of electrons in aggregates/clusters, formed via intermolecular and intramolecular interactions, the actual contributor of fluorescence between 300 and 400 nm is the stabilizer molecule, i.e., 3-tert-butyl-4-hydroxyanisole present in the commercially available PEG 20k. Therefore, the reported fluorescence properties of PEG should be taken with a grain of salt, warranting further investigation.

Polyethylene Glycol Impacts Conformation and Dynamics of Escherichia coli Prolyl-tRNA Synthetase Via Crowding and Confinement Effects

“…The larger PEG polymers (PEG 8k and 20k) formed a cage-like assembly, encapsulating the dimeric Ec ProRS (Figure c,d). As reported earlier, similar aggregates were observed in the aqueous simulation of PEG 20k . The 18 PEG 8k molecules self-assembled, forming compact clusters that wrapped around all three domains of the dimeric Ec ProRS (Figure c).…”

“…In the presence of 100 mg/mL PEG 8k, similar decreases in Trp fluorescence intensity were observed for WT and mutant proteins (Table ). PEG 8k was chosen here instead of PEG 20k because the commercially available PEG 20k contains fluorescent stabilizers such as 3- tert -butyl-4-hydroxyanisole and thus fluoresces . PEG 20,000 interfered with the fluorescence measurements with mutant variants due to their weaker fluorescence properties relative to the WT enzyme.…”

“…The PEG 8k and 20k crowding agents were allowed to partially fold by running 500 ps of equilibration dynamics in water, as previously described. 40 For EG and PEG 600 crowders, Packmol 55 was used to create the solvated protein-crowder assembly by randomly distributing crowders as well as solvent molecules around the dimeric Ec ProRS. For PEG 8k and PEG 20k systems, the assembly was generated by placing the crowders in close proximity to the target protein, which could maximize the possibility of protein-crowder interactions.…”

“…Similarly, individual EG and PEG 600 crowder molecules were geometrically optimized in the gas phase using 200 and 1000 steps of the Newton–Raphson optimizer method available in the CHARMM program suite, respectively. The PEG 8k and 20k crowding agents were allowed to partially fold by running 500 ps of equilibration dynamics in water, as previously described …”

Virtual Screening of Molecules via Neural Fingerprint-based Deep Learning Technique

“…In our lab, computational chemistry has been used for over a decade in elucidating the chemistry of enzymes that are drug targets [18][19][20][21][22][23][24][25][26][27]. Using classical and quantum physics-based models, these studies explored intermolecular interactions [18,20,22]. receptor-ligand complexes [19][20][21], redox processes [23][24][25][26], and enzyme catalysis [19,21,23].…”