Quantitative Characterization of DNA Films by X-ray Photoelectron Spectroscopy

Abstract

We describe the use of self-assembled films of thiolated (dT)25 single-stranded DNA (ssDNA) on gold as a model system for quantitative characterization of DNA films by X-ray photoelectron spectroscopy (XPS). We evaluate the applicability of a uniform and homogeneous overlayer-substrate model for data analysis, examine model parameters used to describe DNA films (e.g., density and electron attenuation length), and validate the results. The model is used to obtain quantitative composition and coverage information as a function of immobilization time. We find that when the electron attenuation effects are properly included in the XPS data analysis, excellent agreement is obtained with Fourier transform infrared (FTIR) measurements for relative values of the DNA coverage, and the calculated absolute coverage is consistent with a previous radiolabeling study. Based on the effectiveness of the analysis procedure for model (dT)25 ssDNA films, it should be generally valid for direct quantitative comparison of DNA films prepared under widely varying conditions.

X-ray induced damage in DNA monitored by X-ray photoelectron spectroscopy

“…3͑a͒ includes contributions from a deoxyribose sugar, i.e., alcohol and cyclic ether, and from nucleobase, i.e., C u N bonds. Previously reported C 1s spectra from single stranded DNA oligonucleotides 20,22 are slightly different from those presented here, particularly with respect to the relative intensities of subpeaks. As shown in Fig.…”

“…Generally, the N and P elements are unaffected by surface contamination during sample preparation and handling; thus their existence indicates adsorption of the DNA sample onto the substrate. 20 In addition to four principal elements in a film ͑C, N, O, and P͒, a peak is observed at the binding energy of 272 eV attributed to the ejection of photoelectrons from Cl 1s due to the presence of salt in the sample. No peak was observed in the region characteristic of the silicon substrate ͑99.7 eV͒.…”

Construction of a densely poly(ethylene glycol)-chain-tethered surface and its performance

“…[58][59][60][61][62] Efficient immobilization protocols yielding high surface coverage, well-established alignment and proper orientation of single-strand DNA (ssDNA) on surfaces as a probe molecule are primary issues in the construction of high-performance DNA-based sensors. The immobilization of probe ssDNA molecules onto a gold surface is generally accomplished by using sulfanylanchored DNA (DNA-SH; It was well known that 'mercapto-' and '-thiol' have been used in the scientific literature as prefix and suffix, respectively.…”

Quantification of discrete oxide and sulfur layers on sulfur‐passivated InAs by XPS

“…The binding energies (BE) are reported with 0.1 eV precision, on the basis of a two-point analyzer energy calibration described in detail elsewhere. 12 Two types of normal-emission angle-integrated surveys were used to monitor samples for presence of contaminants: 0-1400 eV BE range (1.8 eV analyzer resolution, 1 eV point spacing), and 0-550 eV BE range (0.9 eV analyzer resolution, 0.33 eV point spacing). High-resolution normal-emission angle-integrated scans were acquired for the As 3d, In 3d, O 1s, C 1s, S 2p, and As 2p regions, with 0.36 eV analyzer resolution (0.9 eV for As 2p).…”