Investigation of Hydration States of Ionic Liquids by Fourier Transform Infrared Absorption Spectroscopy: Relevance to Stabilization of Protein Molecules.

Among many kinds of ionic liquids, some hydrated ionic liquids (Hy ILs) have shown an exceptional capability to stabilize protein molecules and maintain their structure and functions over a long period. However, the complex IL-water interaction among these protein-stabilizing Hy ILs has yet to be elucidated clearly. In this work, we investigate the origin of the compatibility of ionic liquid with proteins from the viewpoint of hydration structure.

Interphase Protein Layers Formed on Self-Assembled Monolayers in Crowded Biological Environments: Analysis by Surface Force and Quartz Crystal Microbalance Measurements.

We investigated a viscous protein layer formed on self-assembled monolayers (SAMs) in crowded biological environments. The results were obtained through force spectroscopic measurements using colloidal probes and substantiated by exhaustive analysis using a quartz crystal microbalance with an energy dissipation technique. A hydrophobic SAM of -octanethiol (C8 SAM) in bovine serum albumin (BSA) solution is buried under an adlayer of denatured BSA molecules and an additional viscous interphase layer that is five times more viscous than the bulk solution.

Protein- and Cell-Resistance of Zwitterionic Peptide-Based Self-Assembled Monolayers: Anti-Biofouling Tests and Surface Force Analysis.

Peptide-based self-assembled monolayers (peptide-SAMs) with specific zwitterionic amino acid sequences express an anti-biofouling property. In this work, we performed protein adsorption and cell adhesion tests using peptide-SAMs with repeating units of various zwitterionic pairs of amino acids (EK, DK, ER, and DR). The SAMs with the repeating units of EK and DK (EK and DK SAMs) manifested excellent bioinertness, whereas the SAMs with the repeating units of ER and DR (ER and DR SAMs) adhered proteins and cells.

Data-Driven Prediction of Protein Adsorption on Self-Assembled Monolayers toward Material Screening and Design.

We attempt to predict the water contact angle (WCA) of self-assembled monolayers (SAMs) and protein adsorption on the SAMs from the chemical structures of molecules constituting the SAMs using machine learning with an artificial neural network (ANN) model. After training the ANN with data of 145 SAMs, the ANN became capable of predicting the WCA and protein adsorption accurately. The analysis of the trained ANN quantitatively revealed the importance of each structural parameter for the WCA and protein adsorption, providing essential and quantitative information for material design.

Molecular-scale structures of the surface and hydration shell of bioinert mixed-charged self-assembled monolayers investigated by frequency modulation atomic force microscopy.

We studied the surface structure and hydration structure of a bioinert mix-charged self-assembled monolayer (MC-SAM) comprised of sulfonic acid (SA)- and trimethylamine (TMA)-terminated thiols in liquid by frequency modulation atomic force microscopy (FM-AFM) at a molecular-scale. The TMA end groups showed a highly-ordered rectangular arrangement on a gold substrate in phosphate buffer saline (PBS). Highly structured water was observed at the interface of the MC-SAM and PBS, whereas a less structured hydration structure was observed on bioactive SAMs such as those with OH- and COO- terminal groups.

Interactions between protein molecules and the virus removal membrane surface: Effects of immunoglobulin G adsorption and conformational changes on filter performance.

Membrane fouling commonly occurs in all filter types during virus filtration in protein-based biopharmaceutical manufacturing. Mechanisms of decline in virus filter performance due to membrane fouling were investigated using a cellulose-based virus filter as a model membrane. Filter performance was critically dependent on solution conditions; specifically, ionic strength.