Comparison of Physicochemical Properties of Native Mucus and Reconstituted Mucin Gels.

Simulating native mucus with model systems such as gels made from reconstituted mucin or commercially available polymers presents experimental advantages including greater sample availability and reduced inter- and intradonor heterogeneity. Understanding whether these gels reproduce the complex physical and biochemical properties of native mucus at multiple length scales is critical to building relevant experimental models, but few systematic comparisons have been reported. Here, we compared bulk mechanical properties, microstructure, and biochemical responses of mucus from different niches, reconstituted mucin gels (with similar pH and polymer concentrations as native tissues), and commonly used commercially available polymers.

Probing the potential of mucus permeability to signify preterm birth risk.

Preterm birth is the leading cause of neonatal mortality, and is frequently associated with intra-amniotic infection hypothesized to arise from bacterial ascension across a dysfunctional cervical mucus plug. To study this dysfunction, we assessed the permeability of cervical mucus from non-pregnant ovulating (n = 20) and high- (n = 9) and low-risk (n = 16) pregnant women to probes of varying sizes and surface chemistries. We found that the motion of negatively charged, carboxylated microspheres in mucus from pregnant patients was significantly restricted compared to ovulating patients, but not significantly different between high- and low-risk pregnant women.

Kinetics of peptide folding in lipid membranes.

Despite our extensive understanding of water-soluble protein folding kinetics, much less is known about the folding dynamics and mechanisms of membrane proteins. However, recent studies have shown that for relatively simple systems, such as peptides that form a transmembrane α-helix, helical dimer, or helix-turn-helix, it is possible to assess the kinetics of several important steps, including peptide binding to the membrane from aqueous solution, peptide folding on the membrane surface, helix insertion into the membrane, and helix-helix association inside the membrane. Herein, we provide a brief review of these studies and also suggest new initiation and probing methods that could lead to improved temporal and structural resolution in future experiments.

Divalent cation-induced cluster formation by polyphosphoinositides in model membranes.

Polyphosphoinositides (PPIs) and in particular phosphatidylinositol-(4,5)-bisphosphate (PI4,5P2), control many cellular events and bind with variable levels of specificity to hundreds of intracellular proteins in vitro. The much more restricted targeting of proteins to PPIs in cell membranes is thought to result in part from the formation of spatially distinct PIP2 pools, but the mechanisms that cause formation and maintenance of PIP2 clusters are still under debate. The hypothesis that PIP2 forms submicrometer-sized clusters in the membrane by electrostatic interactions with intracellular divalent cations is tested here using lipid monolayer and bilayer model membranes.

Computational design of a β-peptide that targets transmembrane helices.

The design of β-peptide foldamers targeting the transmembrane (TM) domains of complex natural membrane proteins has been a formidable challenge. A series of β-peptides was designed to stably insert in TM orientations in phospholipid bilayers. Their secondary structures and orientation in the phospholipid bilayer was characterized using biophysical methods.