Many biological recognition interactions involve ligands and receptors that are tethered rather than rigidly bound on a cell surface. A surface forces apparatus was used to directly measure the force-distance interaction between polymer-tethered ligand its receptor. At separations near fully extended tether length, rapidly lock onto their binding sites, pulling receptor together. The measured potential dynamics can be modeled with standard theories of polymer colloidal interactions.

The promoters of cell adhesion are ligands, which often attached to flexible tethers that bind surface receptors on adjacent cells. Using a combination Monte Carlo simulations, diffusion reaction theory, and direct experiments (surface force measurements) the biotin-streptavidin system, we have quantified polymer chain dynamics kinetics spatial range tethered ligand-receptor binding. results show efficiency strong binding does not depend solely molecular architecture or energy...

Although polyethylene glycol (PEG) is widely used for aggregating or fusing cells, the forces responsible these interactions have remained elusive. Through a variety of techniques including quasi-elastic light scattering, surface force measurements, and 31P-NMR, we established that while PEG molecular weight 8000−10000 effective in causing aggregation vesicles, lower higher (1000 18 500, respectively) ineffective. For first time, direct measurements between lipid bilayers solutions reveal...

The structure, phase behavior, and properties of cellular membranes are derived from their composition, which includes phospholipids, sphingolipids, sterols, proteins with various levels glycosylation. Because the intricate nature membranes, a plethora in vitro studies have been carried out model membrane systems that capture particular such as fluidity, permeability, protein binding but vastly simplify composition order to focus detail on specialized property or function. Supported lipid...

We demonstrate that 18 keV x-rays can be used to study organic thin films at the solid-liquid interface by x-ray reflectivity. establish this is a powerful technique for investigating biological systems in previously inaccessible manner. Our measurements enabled density distribution of single phospholipid bilayer membranes bulk water measured with unprecedented precision. Previously, characterization biomimetic structures normal "buried" was domain neutron

Biological membranes are complex, self-organized structures that define boundaries and compartmentalize space in living matter. Composed of a wide variety lipid protein molecules, these responsive surfaces mediate transmembrane signaling material transport within the cell with its environment. It is well known membrane properties change as function composition phase state, protein-lipid interactions can induce changes membrane’s biochemical response. Here, molecular level organization...

The density distribution of a lipid monolayer at the air−water interface mixed with varying amounts poly(ethylene glycol) polymer headgroups (polymer−lipid or PEG−lipid) was measured using neutron reflectometry. structure greatly perturbed by presence bulky polymer−lipid resulting in large increase thickness headgroup region normal to and systematic roughening increasing content. These results show how hydrophilic moieties cause significant deformations out-of-plane protrusions phospholipid...

The structure of single supported dipalmitoyl-phosphatidylcholine bilayers prepared by vesicle fusion or Langmuir-Blodgett-Schaeffer (LBS) deposition techniques was characterized x-ray reflectivity and grazing incidence diffraction in bulk water. LBS display symmetric leaflets similar to monolayer structures, while yields more inhomogeneous bilayers. Diffraction establishes that lipids are always coupled across the bilayer even when deposited independently suggests existence orientational texture.

Direct writing methods are a generic and simple means to produce designed structures in three dimensions (3D). The printing is achieved by extruding materials through nozzle, which provides platform deliver wide range of materials. Although this method has been routinely used for 3D at macroscopic scales, miniaturization micrometer nanometer scales building hierarchical multidimensional represent new challenges research development. current work addresses these combining the spatial...

Polydiacetylenes (PDAs) are conjugated polymers that well known for their colorimetric transition from blue to red with the application of energetic stimulus. Sensing platforms based on polymerized diacetylene surfactant vesicles and other structures have been widely demonstrated various biosensing applications. Although less studied utilized, also results in a change non-fluorescent highly fluorescent state, making polydiacetylenes useful both fluorogenic sensing Here, we focus...

Understanding the interfacial properties of high energy explosives blended with polymer binders is important for optimizing material performance and predicting aging. In case PBX 9502, direct measurements TATB – Kel-F 800 interface have been limited by lack high-fidelity model systems. This paper reports fabrication a new thin film, sample to enable neutron reflectometry this interface. The fabricated films were characterized using X-ray diffraction, scanning electron microscopy, atomic...

Using the surface forces apparatus, we have measured static and hydrodynamic between two substrate supported lipid bilayers in water semidilute aqueous solutions of 8000 MW poly(ethylene glycol) (PEG), a neutral polymer for which is good solvent. At small separations (D < RF, Flory radius), an enhanced adhesion due to depletion attraction was measured. Conversely, at larger found repulsive barrier, not predicted by mean-field theories. Dynamic measurements viscosity as function film...

We have measured the attractive long-range 'hydrophobic' forces in water between double-chained surfactant monolayers physisorbed on mica. used both normal and high-speed video cameras to follow dynamics possible rate-dependence of force−distance profiles distance regime from 1000 Å adhesive contact, including short-distance below 100 Åthe greatest biological interest. find that hydrophobic interaction follows a double-exponential function down separations ∼50 Å, after which point force...

We report the first grazing incidence x-ray diffraction measurements of a single phospholipid bilayer at solid-liquid interface. Our and reflectivity reveal that lateral ordering in supported DPPE (1, 2-Dipalmitoyl-sn-Glycero-3-Phosphoethanolamine) is significantly less than an equivalent monolayer air-liquid findings also indicate leaflets are uncoupled contrast to scattering from free standing phosphatidylcholine bilayers. The methodology presented can be readily implemented study more...

Molecular dynamics simulations are presented of coarse-grained, polar, polymer brushes in a good polar solvent at high grafting densities. Chain extension is heavily influenced by temperature, stretching far from the surface temperature (350 K) while weak absorption and loop formation observed low (300 K). Simulations isolated free chains different lengths solution demonstrate polymers conditions both temperatures. Consistent with previous findings, increasing density leads to larger chain...