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Modified Random Sequential Adsorption Model for Understanding Kinetics of Proteins Adsorption at a Liquid–Solid Interface

Evidence and attribution

Authority of statements

Prose below (Summary, Methods, Findings) summarizes the publication identified by doi, title, and pdf_path in the front matter. For fitted kinetic parameters, RSA derivations, and MD setup details, rely on the peer-reviewed article.

Summary

Human serum albumin (HSA) adsorption on a hydrophobic hexadecanethiolated gold surface is measured in real time with 83 MHz micromachined quartz crystal resonators, comparing single-injection and multi-injection protocols at the same final bulk concentration. The measured kinetics show RSA-like jamming at long times together with a slowdown that standard random sequential adsorption (RSA) transport models do not fully capture. The authors introduce an interface-depletion modified RSA picture with an exponentially depleting interfacial supply. Complementary ReaxFF molecular dynamics of a thiolated gold surface with explicit water supports preferred interfacial orientation of adsorbed protein segments and a strongly reduced lateral diffusion coefficient in the interfacial layer; coupling faster surface attachment to slower interfacial diffusion rationalizes the depleted interfacial concentration and the observed slowdown relative to bulk-limited uptake.

Methods

A — Force-field training / fitting: ReaxFF for Au–S–C–H–O thiolated gold / aqueous interfaces as used in the article (no new parameter fit summarized on this page).

B — Molecular dynamics / sampling: ReaxFF MD (LAMMPS) of hexadecanethiol-covered Au with explicit water and reduced HSA representation; staged equilibration then 400 ps production (analysis last 200 ps). NVT, 298.15 K, 0.25 fs, Berendsen thermostat (100 fs damping).

C — DFT / static QM: Not the primary layer for adsorption trajectories summarized here.

D — Review / non-simulation framing: Experiment: 83 MHz QCM real-time HSA adsorption on hydrophobic thiol/Au; single- vs multi-injection at matched final concentration; RSA/jamming-limit coverage.

Engine: LAMMPS ReaxFF as above. System: hexadecanethiol-covered Au with explicit water and a reduced HSA representation; atom counts are given in the Langmuir article. Boundaries / periodicity: 3D PBC is the default for this class of thiol/Au aqueous slab models; confirm frozen vs mobile Au layers in pdf_path. Ensemble / thermostat / timestep / duration: NVT, 298.15 K, 0.25 fs, Berendsen thermostat (100 fs damping), 400 ps production (analysis on last 200 ps) after staged equilibration as in Methods. Barostat / pressure: N/A — NVT constant-volume interfacial cell; no NPT segment reported for the production MD. Electric field: N/A — not used. Replica / enhanced sampling: N/A — not used.

Findings

Experimental transients are described with the proposed interface-depletion RSA framework (exponential depletion of the interfacial layer). ReaxFF trajectories indicate specific adsorption orientation at the thiolated interface and markedly reduced in-layer diffusion versus bulk-like behavior, supporting the idea that reduced interfacial diffusivity and adsorption rate together produce interfacial depletion and the slowed HSA uptake observed on the hydrophobic surface.

Limitations

  • Atomistic modeling uses a reduced representation of HSA (segments / simplified geometry as in the paper), not full all-atom protein at experimental size; quantitative diffusion coefficients are model-dependent.
  • Classical reactive MD cannot capture all conformational and electrostatic details of soft biological adsorption without experimental or higher-level benchmarks.

Relevance to group

Includes Adri C. T. van Duin as co-author; demonstrates ReaxFF at biomolecule–metal–aqueous interfaces paired with microgravimetric kinetics.

Citations and evidence anchors

Reader notes (navigation)

  • Protein / interface and biosensor-adjacent work: cross-link from paper-index-by-domain or theme hubs as the corpus grows.