Hydration Repulsion Effects of the Formation of Supported Lipid Bylayers

When zwitterionic lipids fuse onto substrates such as silica (SiO2), the water of hydration between the two approaching surfaces must be removed, giving rise to an effective hydration repulsion. Removal of water around the polar headgroups of the lipid and the silanols (SiOH) of SiO2 allows supported lipid bilayer (SLB) formation, although an interstitial water layer remains between the lipid and surface. The importance of hydration repulsion in SLB formation is demonstrated by monitoring fusion of zwitterionic lipids onto silica (SiO2) nanoparticles heat treated to control the silanol group (SiOH) density and thus the amount of bound water. SLB formation, observed by cryo-TEM and nanodifferential scanning calorimetry, was found to be slower for the more hydrated surfaces. Although the SiOH density decreased with increasing heat treatment temperature, z-potentials were the same for all the SiO2. This arose since at the pH ¼ 8 of the experiments, only isolated silanols, with a pKa ¼ 4.9, and not hydrogen bonded silanols, with a pKa ¼ 8.5, were dissociated/charged.1 Since there were no differences in double layer forces between the SUVs and SiO2, which are the largest and most important interactions determining lipid fusion onto surfaces,2,3 the slower rate of SLB formation of DMPC onto SiO2 nanoparticles with higher silanol densities and more bound water was therefore attributed to greater hydration repulsion of the more hydrated nanoparticles. For SiO2 heated to 1000 °C, with only a few isolated silanols, little adsorbed water and many hydrophobic Si–O–Si groups, particle aggregation occurred and lipid sheaths formed around the nanoparticle aggregates

Detectable clonal mosaicism and its relationship to aging and cancer

In an analysis of 31,717 cancer cases and 26,136 cancer-free controls from 13 genome-wide association studies, we observed large chromosomal abnormalities in a subset of clones in DNA obtained from blood or buccal samples. We observed mosaic abnormalities, either aneuploidy or copy-neutral loss of heterozygosity, of >2 Mb in size in autosomes of 517 individuals (0.89%), with abnormal cell proportions of between 7% and 95%. In cancer-free individuals, frequency increased with age, from 0.23% under 50 years to 1.91% between 75 and 79 years (P = 4.8 × 10(-8)). Mosaic abnormalities were more frequent in individuals with solid tumors (0.97% versus 0.74% in cancer-free individuals; odds ratio (OR) = 1.25; P = 0.016), with stronger association with cases who had DNA collected before diagnosis or treatment (OR = 1.45; P = 0.0005). Detectable mosaicism was also more common in individuals for whom DNA was collected at least 1 year before diagnosis with leukemia compared to cancer-free individuals (OR = 35.4; P = 3.8 × 10(-11)). These findings underscore the time-dependent nature of somatic events in the etiology of cancer and potentially other late-onset diseases

Spectroscopic study of Α- and Β-phase isotactic polypropylene and of atactic polypropylene in solution

No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/38673/1/180231221_ftp.pd

Engineered Interfaces in Hybrid Ceramic–Polymer Electrolytes for Use in All-Solid-State Li Batteries

Composites of inorganic lithium ion conducting glass ceramics (LICGCs) and organic polymers may provide the best combination of properties for safe solid separators in lithium or lithium ion batteries to replace the currently used volatile liquid electrolytes. A key problem for their use is the high interfacial resistance that develops between the two, increasing the total cell impedance. Here we show that the application of a thin conformal SiO₂ coating onto a LICGC followed by silanization with (CH₃CH₂O)₃–Si–(OCH₂CH₂)–OCH₃ in the presence of LiTFSI results in good adhesion between the SiO₂ and the LICGC, a low resistance interface, and good wetting of Li⁰. Further, the cross-linked polymer formed on the surface of the silanated SiO₂ interface formed from excess (CH₃CH₂O)₃–Si–(OCH₂CH₂)–OCH₃ prevents corrosion of the LICGC by Li⁰ metal. The use of SiO₂ as a “glue” enables compatibilization of inorganic ceramics with other polymers and introduction of interfacial pendant anions