Mechanistic insight into patterned supported lipid bilayer self-assembly.

Patterned supported lipid bilayers (SLBs) provide a model system for studying fluid lipid bilayers and transmembrane proteins in an array format. SLB arrays self-assemble on patterned self-assembled monolayers (SAMs) consisting of hexadecanethiol and glycol-terminated regions. While the mechanism of SLB formation on glass has been studied extensively, the formation of SLBs on other substrates is not necessarily well understood. Moreover, SLB arrays on patterned SAMs represent an intriguing system, since lipid vesicles do not adhere to glycol-terminated monolayers. Here, we utilize surface plasmon resonance imaging (SPRi) and kinetic analysis to examine the mechanism of SLB formation on the glycol-terminated regions of patterned SAMs and supported lipid monolayer (SLM) formation on alkyl-terminated regions of patterned SAMs. We determine that vesicles rupture to form a patterned SLB through a two-step mechanism that is dependent upon vesicle attachment at the interface of the two regions of the patterned monolayer.

Increased stability of glycol-terminated self-assembled monolayers for long-term patterned cell culture.

Self-assembled monolayers (SAMs) are widely used to confine proteins and cells to a pattern to study cellular processes and behavior. To fully explore some of these phenomena, it is necessary to control cell growth and confinement for several weeks. Here, we present a simple method by which protein and cellular confinement to a pattern can be maintained for more than 35 days. This represents a significant increase in pattern stability compared to previous monolayer systems and is achieved using an amide-linked glycol monomer on 50 Å titanium/100 Å gold-coated glass coverslips. In addition, this study provides insight into the method of SAM degradation and excludes interfacial mixing of the monomers and blooming of the adlayer as major mechanisms for SAM degradation.

Microcontact printing for creation of patterned lipid bilayers on tetraethylene glycol self-assembled monolayers.

Supported lipid bilayers (SLBs) formed on many different substrates have been widely used in the study of lipid bilayers. However, most SLBs suffer from inhomogeneities due to interactions between the lipid bilayer and the substrate. In order to avoid this problem, we have used microcontact printing to create patterned SLBs on top of ethylene-glycol-terminated self-assembled monolayers (SAMs). Glycol-terminated SAMs have previously been shown to resist absorbance of biomolecules including lipid vesicles. In our system, patterned lipid bilayer regions are separated by lipid monolayers, which form over the patterned hexadecanethiol portions of the surface. Furthermore, we demonstrate that α-hemolysin, a large transmembrane protein, inserts preferentially into the lipid bilayer regions of the substrate.

Sequence or structure: using bioinformatics and homology modeling to understand functional relationships in cAMP/cGMP binding domains.

The relationship between sequence, structure, and function is examined by comparing nineteen cyclic nucleotide monophosphate binding domains of known structure from six different functional families. Comparisons are made by structure and sequence alignment and through the generation of 3610 homology models. This analysis suggests there are only weak relationships between functional families, sequence, and/or structure. However, we have identified that for cyclic nucleotide monophosphate binding domains privileged template structures occur for homology modeling. The existence of privileged template structures, capable of creating accurate modeling for a broad family of proteins, may lead to improved homology modeling protocols.