Enzyme Catalysis Enhances Lateral Lipid Motility and Directional Particle Transport on Membranes

The dynamic interplay between the composition of lipid membranes and the behavior of membrane-bound enzymes is critical to the understanding of cellular function and viability, and the design of membrane-based biosensing platforms. While there is a significant body of knowledge on how lipid composition and dynamics affect membrane-bound enzymes, little is known about how enzyme catalysis influences the motility and lateral transport in lipid membranes. Using enzymes-attached lipids in supported bilayers (SLB), we show catalysis-induced enhanced lateral diffusion of lipids in the bilayer. Enhancing the membrane viscosity by increasing the cholesterol content in the bilayer suppresses the overall diffusion but not the relative diffusion enhancement of the enzyme-attached lipids. We also provide direct evidence of catalysis-induced membrane fluctuations leading to the enhanced diffusion of passive tracers resting on the SLB. Additionally, by using active enzyme patches, we demonstrate the directional transport of tracers on SLBs. These are first steps in understanding diffusion and transport in lipid membranes due to active, out-of-equilibrium processes that are the hallmark of living systems. In general, our study demonstrates how active enzymes can be used to control diffusion and transport in confined 2-D environments.

Holographic Grating Enhancement of TI/PMMA Polymers in the Dark Diffusion Process

The dark diffusion enhancement process (DDEP) caused by photopolymerization during the pre-exposure of TI/PMMA (titanocene dispersed methyl methacrylate matrix) polymers was theoretically analyzed and experimentally investigated, revealing the holographic grating enhancement of TI/PMMA polymers in the post-exposure process without additional operations. The diffusion of photo-initiators and photoproducts dominated the grating enhancement process after exposure. We adopted two pre-exposure methods, long-time (second level) and short-time (millisecond level) laser exposure, at 532 nm, to investigate the DDEP during the post-exposure process. A five-fold enhancement in grating strength was achieved in consecutive long-time pre-exposures, while a two-fold grating development was examined after short-time exposure. Additionally, the exposure durations and repetition rates influenced the grating increment of the DDEP. This study provided a basis for the feasibility of holographic application in TI/PMMA photopolymers via the dark diffusion effect.

Modification of Densification Mechanisms By The Timing of Mechanical Pressure During Spark Plasma Sintering

The application of mechanical pressure during a sintering process is connected with grains sliding and diffusion enhancement. However, the timing of mechanical pressure during the rapid sintering process was not addressed. In the present study, four different timings of mechanical pressure with final pressure 50 MPa starting from the beginning, 600 ℃, 900 ℃ and at sintering temperature, furthermore one pressure-less SPS have been studied during SPS of Nano-Alumina powder (Taimei, Japan) at 1100 ℃, 1150 ℃, 1200 ℃, and 1300 ℃, respectively. The density, hardness, microstructure, and grain size of each sample were measured and calculated carefully. The results show that applying the pressure at 900 ℃ brings high density and small grain size, leading to the best Vickers hardness. The interaction between pressure and vapor, leading to the different vapor transfer rate of the first sintering stage, is considered as a reason for the differences in the microstructure.

Adjustable diffusion enhancement of water molecules in a nanoscale water bridge

Adjustable enhanced diffusion coefficients in a water bridge are 4 times larger than those in bulk water.