Investigating Lipase/Stain Interactions: Determining Interfacial Protein Conformation with Surface Spectroscopy.

Conventional bulk protein structure determination methods are not suitable for understanding the distinct and diverse interactions of proteins with interfaces. Notably, interfacial activation is a feature common to many lipases involving movement of a helical "lid" region upon contact with a hydrophobic surface to expose the catalytic site. Here we use the surface specificity of vibrational sum frequency generation spectroscopy (VSFG) spectroscopy to directly probe the conformation of lipase (TLL) at hydrophobic interfaces.

Umbrella-like Helical Structure of α-Synuclein at the Air-Water Interface Observed with Experimental and Theoretical Sum Frequency Generation Spectroscopy.

The misfolding of α-synuclein (αS) into amyloid aggregates is catalyzed by hydrophobic surfaces and associated with severe brain disorders, such as Parkinson's disease. Despite the important role of interfaces, the three-dimensional structure of αS at the interfaces is still not clear. We report interface-specific sum frequency generation (SFG) experiments of monomeric αS binding to the air-water interface, a model system for the important hydrophobic surfaces.

Elevated concentrations cause upright alpha-synuclein conformation at lipid interfaces.

The amyloid aggregation of α-synuclein (αS), related to Parkinson's disease, can be catalyzed by lipid membranes. Despite the importance of lipid surfaces, the 3D-structure and orientation of lipid-bound αS is still not known in detail. Here, we report interface-specific vibrational sum-frequency generation (VSFG) experiments that reveal how monomeric αS binds to an anionic lipid interface over a large range of αS-lipid ratios.

Peptide Orientation at Emulsion Nanointerfaces Dramatically Different from Flat Surfaces.

The adsorption of protein to nanoparticles plays an important role in toxicity, food science, pharmaceutics, and biomaterial science. Understanding how proteins bind to nanophase surfaces is instrumental for understanding and, ultimately, controlling nanoparticle (NP) biochemistry. Techniques probing the adsorption of proteins at NP interfaces exist; however, these methods have been unable to determine the orientation and folding of proteins at these interfaces.

Theoretical Sum Frequency Generation Spectra of Protein Amide with Surface-Specific Velocity-Velocity Correlation Functions.

Vibrational sum frequency generation (vSFG) spectroscopy is widely used to probe the protein structure at interfaces. Because protein vSFG spectra are complex, they can only provide detailed structural information if combined with computer simulations of protein molecular dynamics and spectra calculations. We show how vSFG spectra can be accurately modeled using a surface-specific velocity-velocity scheme based on normal modes.

Tutorials in vibrational sum frequency generation spectroscopy. III. Collecting, processing, and analyzing vibrational sum frequency generation spectra.

In this Tutorial series, we aim to provide an accessible introduction to vibrational sum frequency generation (VSFG) spectroscopy, targeted toward people entering the VSFG world without a rigorous formal background in optical physics or nonlinear spectroscopy. In this article, we discuss in detail the processes of collecting and processing VSFG data, and user-friendly processing software (sfgtools) is provided for use by people new to the field. Some discussion of analyzing VSFG spectra is also given, specifically with a discussion of fitting homodyne VSFG spectra, and a discussion of what can be learned (both qualitatively and quantitatively) from VSFG spectra.

Peptide Mimic of the Marine Sponge Protein Silicatein Fabricates Ultrathin Nanosheets of Silicon Dioxide and Titanium Dioxide.

Two-dimensional (2D) materials have attracted attention for potential applications in light harvesting, catalysis, and molecular electronics. Mineral proteins involved in hard tissue biogenesis can produce 2D structures with high fidelity by using sustainable production routes. This study shows that a peptide mimic based on the catalytic triad of the marine sponge protein silicatein catalyzes the formation of nanometer thin and stable sheets of silicon dioxide and titanium dioxide.

Tutorials in vibrational sum frequency generation spectroscopy. II. Designing a broadband vibrational sum frequency generation spectrometer.

In this Tutorial series, we aim to provide an accessible introduction to vibrational sum frequency generation (VSFG) spectroscopy, targeted toward people entering the VSFG world without a rigorous formal background in optical physics or nonlinear spectroscopy. In this article, we describe in depth how a broadband VSFG spectrometer is designed and constructed, using the instrument in SurfLab, Aarhus University, as an illustrative case. Detailed information about specific instrumentation (together with reasons why things are the way they are) is given throughout.

Tutorials in vibrational sum frequency generation spectroscopy. I. The foundations.

Interfaces between bulk media are often where critical molecular processes occur that can dictate the chemistry of an entire macroscopic system. Optical spectroscopy such as IR or Raman spectroscopy is often challenging to apply to interfaces due to contributions from bulk phases that dominate the spectra, masking any detail about the interfacial layer. Vibrational sum frequency generation (VSFG) spectroscopy is a nonlinear spectroscopy that allows vibrational spectra of molecules at interfaces to be directly measured.

The complex between molecular oxygen and an organic molecule: modeling optical transitions to the intermolecular charge-transfer state.

The collision complex between the ground electronic state of an organic molecule, M, and ground state oxygen, O2(X3Σg-), can absorb light to produce an intermolecular charge transfer (CT) state, often represented simply as the M radical cation, M+˙, paired with the superoxide radical anion, O2-˙. Aspects of this transition have been the subject of numerous studies for ∼70 years, many of which address fundamental concepts in chemistry and physics. We now examine the extent to which the combination of Molecular Dynamics simulations and electronic structure response methods can model transitions to the toluene-O2 CT state.

Tungsten Iodide Clusters as Singlet Oxygen Photosensitizers: Exploring the Domain of Resonant Energy Transfer at 1 eV.

The photophysics of selected tungsten iodide clusters was examined with respect to their role as a photosensitizer for the production of singlet oxygen, O(aΔ). We examined all-iodo octahedral clusters, [WI(I)], and ligand-substituted octahedral clusters, [WI(L)], in which the ligand, L, occupies the outer apical positions surrounding the cluster core. We also examined a square-pyramidal cluster, [WI(I)], in which the tungsten core was presumably more accessible to diffusional encounter with ground state oxygen, O(XΣ).