File Name : figure s1.pdf Caption : effects of the pcd and bod oxygen-scavenging systems (osss) in different buffers on the force-extension curve (fec) of a single dna molecule. (a) representative fecs of the same dna molecule measured successively in t150, t150 with pcd oss, and t150 again. the horizontal axis represents the ratio of dna length to its contour length, while the vertical axis indicates the force applied to the dna by magnetic tweezers. (b) representative fecs of the same dna molecule measured successively in t150, t150 with bod oss, and t150 with pcd oss. (c, d) fecs of dna measured in (c) pbs or (d) t50 buffer with (red) or without (black) bod oss. notice here that the solid lines represent the stretching curves and the dashed lines represent the relaxing curves. File Name : figure s2.pdf Caption : the effect of poc oss on the dna fecs in different buffers. (a) representative fecs of the same dna molecule measured successively in t150, t50, and t50 with pcd oss. (b) representative fecs of different dna molecules in t50 buffer without (left panel) and with (right panel) poc oss. different colors represent different dna molecules. the solid lines represent the stretching curves while the dashed lines correspond to the relaxing curves. File Name : figure s3.pdf Caption : dna stretching experiments in various solutions to investigate the mechanism by which the pcd oss influences the mechanical properties of dna. (a) fecs of the same dna molecule in t150 buffer without pcd oss (black) or with individual pcd oss components: protocatechuate 3,4-dioxygenase (pcd, red), trolox (green), and 3,4-dihydroxybenzoic acid (pca, blue). (b) similar to (a), but with pairs of components added: pca+trolox (light red), pcd+trolox (light green), and pca+pcd (light blue). (c) fecs of the same dna molecule in t150 buffer (without oss) at different ph values: ph=8.0 (dark red), ph=7.2 (dark green), ph=6.1 (dark blue). File Name : figure s4.pdf Caption : typical winding curves of the same dna molecule in t150 buffer (black), and t150 buffer with poc oss (green), pcd oss (blue), or bod oss (red). File Name : figure s5.pdf Caption : proposed reaction pathway for pcd oss. the reaction product, i.e., 3-carboxy-cis, cis-muconic acid, may exist in either protonated or deprotonated form depending on the ph of the solution. File Name : figure s6.pdf Caption : force-extension curves of the same dna molecule in t50 buffer (without oss) at different ph values: (a) ph=7.0, (b) ph=6.5, (c) ph=6.0. minimal changes in the dna fecs were observed as the ph of the buffer decreased from 7.0 to 6.0. File Name : figure s7.pdf Caption : fecs of the same dna molecule in t50 buffer with pcd oss at different ph values: (a) ph=7.0, (b) ph=6.5, (c) ph=6.0. fecs showed more pronounced modifications as the ph of the buffer was lowered from 7.0 to 6.0. File Name : figure s8.pdf Caption : effects of substrates in poc oss and bod oss on dna fecs. (a) fecs of the same dna molecule before (black) and after (red) introducing the poc oss substrate (glucose) into t150 buffer. (b) similar to (a), but with glucose added under low salt (t50 buffer) conditions. (c) fecs of the same dna molecule before (black) and after (red) introducing bod oss substrate (sodium ascorbate) into t150 buffer. here, the solid lines represent the stretching curves while the dashed lines correspond to the relaxing curves. File Name : figure s9.pdf Caption : single-molecule fluorescence experiments to assess oss effects on the photobleaching lifetimes of dyes in t50 buffer. (a, b) survival fraction curves of (a) cy3 and (b) cy5 obtained with bod oss (red), pcd oss (blue) and poc oss (green). each curve was calculated from over 90 single-molecule fluorescence trajectories, with survival fractions representing the percentage of fluorescent molecules not photobleached at various time slots after excitation. the characteristic photobleaching lifetime was determined via a single exponential fit (solid line) to the survival fraction decay curve. (c) photobleaching lifetimes of cy3 and cy5 fluorophores in t50 buffer with different osss, as obtained from (a) and (b). the error bars represent se from fitting. File Name : figure s10.pdf Caption : calibrated relationship between absorbance ratio (a502nm/a470nm) and ph value, using solutions with known ph values (measured with an acidometer) and a spexyte™ micro ph probe. red circles represent experimental data, and the blue dashed line indicates the fitting curve. File Name : figure s11.pdf Caption : changes in the absorption spectrum of the spexyte™ micro ph probe over a 30-minute period following the addition of bod oss or pcd oss to t150, starting from different initial ph values:(a) bod oss added to t150 buffer (initial ph = 8.0), (b) bod oss added to t150 buffer (initial ph = 7.0), (c) pcd oss added to t150 buffer (initial ph = 8.0), (d) pcd oss added to t150 buffer (initial ph = 7.0).