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. Author manuscript; available in PMC: 2021 Dec 1.
Published in final edited form as: Structure. 2020 Aug 6;28(12):1337–1343.e4. doi: 10.1016/j.str.2020.07.009

Figure 2. Fine-tuning PEG deposition conditions at the cloud-point phase transition point is crucial for optimum single-molecule surface properties.

Figure 2.

(A) Non-specific adsorption of 20 nM Alexa647-labelled Gal4-VP16. Linear PEG deposition in a carbonate/bi-carbonate buffer at pH 9.5 with a transition (cloud) point of 0.5 M K2SO4. Note the inhomogeneous surface properties for PEG grafted above the transition point (last two panels, 0.64 M). Scale bars: 1.5 μm. (B) Quantification of non-specific sticking vs. [K2SO4], for Gal4-VP16, TBP and TFIID. Linear PEG deposition in 0.1 M Na2HCO3 pH 9–9.5 (red symbols) or a carbonate/bi-carbonate buffer at pH 9.5 (black symbols). Vertical dotted lines: transition points, 0.4 M and 0.5 M K2SO4 respectively. (C) Performance of 4-arm star-PEG surfaces for TFIIB and TFIIF. The performance of the best linear PEG surfaces at 0.55 M K2SO4 is shown for comparison. In (B, C) symbols and error bars represent mean ± S.D. from 3 independent experiments. See also Figure S2 and Tables S2, S3.