Biopolymerization-driven self-assembly of nanofiber air-bridges

Several proteins, including actin and fibrin, polymerize in vivo to form nanometre diameter fibers. These processes can be duplicated in vitro using only the essential enzyme and protein precursors. These same protein solutions are directed to self-assemble into oriented arrays of air-bridges using only the crude operation of hand brushing them over textured micron-scale surfaces. The creation of these suspended structures could be used as nanomechanical elements in various sensors and actuators, and their fabrication by this rapid directed self-assembly method would be useful, especially during the early phases of prototype device development. The fabrication method extends earlier studies (Harfenist et al., Nano Lett., 2004, 4, 1931) in which an organic polymer dissolved in a volatile solvent forms nanofiber air-bridges through a combination of capillary force driven thinning of liquid bridges and evaporation driven solidification of the polymer solution. However, in the current study polymerization is initiated when a monomeric solution of soluble protein is brushed over the micro-textured surface. When fibrinogen solutions are brushed over a thrombin primed surface, or monomeric actin over a KCl primed array, fiber air-bridges are formed, sometimes reaching diameters as small as 16 nm. The uniformity in diameter of one hand-brushed array of 358 parallel fibrin air-bridges was 36.4 nm (6.8 nm standard deviation), with no more than 3 broken fibers. The fibrin bridges are shown to be both highly elastomeric and adhesive through demonstration of the construction and stretching of a three point bridge using a micromanipulator. Also the brush-on method produced ordered arrays of suspended fibrin membranes, which sometimes were anchored perpendicular to the vertical sidewalls of the textured surface and other times were anchored parallel to the sidewalls. The demonstration of air-bridge formation by biopolymerization suggested that air-bridges might also be formed during initiated polymerization of organic monomers. Even though the monomer of norbornylene has a much smaller molecular weight than fibrinogen, hand brushing of norbornylene in toluene with Grubbs\u27 catalyst resulted in the self-assembly of fiber air-bridges as small as 4 nm diameter over nearly 6 microns length

Detection of renal tissue and urinary tract proteins in the human urine after space flight.

The urine protein composition samples of ten Russian cosmonauts (male, aged of 35 up to 51) performed long flight missions and varied from 169 up to 199 days on the International Space Station (ISS) were analyzed. As a control group, urine samples of six back-up cosmonauts were analyzed. We used proteomic techniques to obtain data and contemporary bioinformatics approaches to perform the analysis. From the total number of identified proteins (238) in our data set, 129 were associated with a known tissue origin. Preflight samples contained 92 tissue-specific proteins, samples obtained on Day 1 after landing had 90 such proteins, while Day 7 samples offered 95 tissue-specific proteins. Analysis showed that consistently present proteins in urine (under physiological conditions and after space flight) are cubilin, epidermal growth factor, kallikrein-1, kininogen-1, megalin, osteopontin, vitamin K-dependent protein Z, uromodulin. Variably present proteins consists of: Na(+)/K(+) ATPase subunit gamma, β-defensin-1, dipeptidyl peptidase 4, maltasa-glucoamilasa, cadherin-like protein, neutral endopeptidase and vascular cell adhesion protein 1. And only three renal proteins were related to the space flight factors. They were not found in the pre-flight samples and in the back-up cosmonaut urine, but were found in the urine samples after space flight: AFAM (afamin), AMPE (aminopeptidase A) and AQP2 (aquaporin-2). This data related with physiological readaptation of water-salt balance. The proteomic analysis of urine samples in different phases of space missions with bioinformation approach to protein identification provides new data relative to biomechemical mechanism of kidney functioning after space flight

Peptides identified for the pos-flight proteins.

<p>Peptides identified for the pos-flight proteins.</p

Microalbuminuria (mg/day) during Space Mission.

<p>Data from Cirillo et al. (28).</p

MSMS data for two peptides of aquaporin 2.

<p>MSMS data for two peptides of aquaporin 2.</p

Renal proteins in the prime and back-up cosmonauts’ urine before and after space flight.

<p>Renal proteins in the prime and back-up cosmonauts’ urine before and after space flight.</p