The biomolecule-membrane interface is one of most important and complex subjects in biology. Biomolecules can interact and manipulate the cellular membrane and the surrounding- they can transport ions, alter the lipid structure, and act as artificial receptors. Despite the importance for surface engineering and drug development, the molecular mechanisms behind interfacial biomolecule action have largely remained elusive. We use ultrafast sum frequency scattering (SFS) spectroscopy to determine the structure and the mode of action by which these biomolecules interact with and manipulate interfaces. The majority of work in the field of sum frequency generation has been done on flat model interfaces. This limits some important membrane properties such as membrane fluidity and dimensionality – important factors in biomolecule-membrane interactions. To move towards three-dimensional nanoscopic interfaces, we utilize SFS spectroscopy to interrogate the surface of 3D lipid monolayers and vesicles. We have utilized SFS spectroscopy to follow the membrane action of lysozyme and shed light on a novel, engineered apoptosis-inducing receptor (AIR). SFS studies at the lysozyme-lipid interface demonstrate that binding of lysozyme induces increased lipid monolayer order. An increase in acyl chain order determined by the ratio of the CH3 symmetric and CH2 asymmetric peak amplitudes and lipid head group orientation change from about 0° to greater than 60° suggests that lysozyme inserts into the lipid layer causing lipid dehydration and reorientation. The amide I SFS spectrum of lysozyme interacting with the model cell lipid monolayer is also studied to observe the folding and ordering of the protein. Furthermore, utilizing extruded vesicles we have observed the insertion and membrane disruption of engineered AIR. Decreased peak amplitudes in the acyl chain and the ester group of the lipid vesicle strongly indicates insertion of the engineered AIR. Altogether, with SFS we have made strides to improve biologically relevant membrane interfaces.

Observing biomolecules at three-dimensional lipid interfaces

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.