Detection of Saturated Fatty Acids Associated with a Self-Healing Synthetic Biological Membrane Using Fiber-Enhanced Surface Enhanced Raman Scattering.

The Synthetic Biological Membrane (SBM) project at NASA Ames developed a portable, self-repairing wastewater purification system. The self-repair process relies upon secreted fatty acids from a genetically engineered organism. However, solubilized fatty acids are difficult to detect using conventional methods. Surface-enhanced Raman scattering (SERS) was used to successfully detect solubilized fatty acids with the following limits of detection: 10-9 M, 10-8 M, 10-9 M, and 10-6 M for decanoic acid, myristic acid, palmitic acid, and stearic acid, respectively. Additionally, hollow core photonic crystal fiber (HCPCF) was applied as the sampling device together with SERS to develop in situ surveillance of the production of fatty acids. Using SERS + HCPCF yielded an 18 fold enhancement in SERS signal for the CH2 twist peak at 1295 cm-1 as compared to SERS alone. The results will help the SBM project to integrate a self-healing wastewater purification membrane into future water recycling systems.

Flexible antibodies with nonprotein hinges.

There is a significant need for antibodies that can bind targets with greater affinity. Here we describe a novel strategy employing chemical semisynthesis to produce symmetroadhesins: antibody-like molecules having nonprotein hinge regions that are more flexible and extendible and are capable of two-handed binding. Native chemical ligation was carried out under mild, non-denaturing conditions to join a ligand binding domain (Aß peptide) to an IgG1 Fc dimer via discrete oxyethylene oligomers of various lengths. Two-handed Aß-Fc fusion proteins were obtained in quantitative yield and shown by surface plasmon resonance to bind an anti-Aß antibody with a K(D) at least two orders of magnitude greater than the cognate Aß peptide. MALDI-TOF MS analysis confirmed the protein/nonprotein/protein structure of the two-handed molecules, demonstrating its power to characterize complex protein-nonprotein hybrids by virtue of desorption/ionization mediated by peptide sequences contained therein. We anticipate many applications for symmetroadhesins that combine the target specificity of antibodies with the novel physical, chemical and biological properties of nonprotein hinges.

Detection of Saturated Fatty Acids Associated with a Self-Healing Synthetic Biological Membrane Using Fiber-Enhanced Surface Enhanced Raman Scattering.

The Synthetic Biological Membrane (SBM) project at NASA Ames developed a portable, self-repairing wastewater purification system. The self-repair process relies upon secreted fatty acids from a genetically engineered organism. However, solubilized fatty acids are difficult to detect using conventional methods. Surface-enhanced Raman scattering (SERS) was used to successfully detect solubilized fatty acids with the following limits of detection: 10-9, 10-8, 10-9, and 10-6 M for decanoic acid, myristic acid, palmitic acid, and stearic acid, respectively. Additionally, hollow core photonic crystal fiber (HCPCF) was applied as the sampling device together with SERS to develop in situ surveillance of the production of fatty acids. Using SERS + HCPCF yielded an 18-fold enhancement in SERS signal for the CH2 twist peak at 1295 cm-1 as compared to SERS alone. The results will help the SBM project to integrate a self-healing wastewater purification membrane into future water recycling systems.

A Novel Technique for Visualizing the Intralymphatic Primo Vascular System by Using Hollow Gold Nanospheres.

Until recently, the primo vascular system (PVS) has been unnoticed by most anatomists due to the small diameter and translucent features of the threadlike network. These properties make primo vessels (PVs) difficult to visualize for harvest and for further characterization. One particular PVS subtype that is located within the lymphatic vessels (LVs) is of strong interest because with a proper contrast, these long PVs can be visualized through the transparent LV wall and can be harvested to provide sufficient sample material for analysis. The most common method to visualize this PVS subtype utilizes Alcian blue as the contrast agent. This technique is effective, but tedious, and has relatively low repeatability. The purpose of this study was to develop a new technique that allows reliable visualization of the intralymphatic PVS (IL-PVS) in a user-friendly manner. The method was designed to provide optical contrast to the PVS by taking advantage of the porous nature of the PV's external wall and interstitial matrix. Turquoise-green-colored hollow gold nanospheres (HGNs) in the size range of 50-125 nm were found to provide excellent optical contrast for the IL-PVS in rats. The PVS was visualized within 10 minutes after HGN administration at a 95% success rate.

Ultrafast transient absorption studies of hematite nanoparticles: the effect of particle shape on exciton dynamics.

Much progress has been made in using hematite (α-Fe2 O3 ) as a potentially practical and sustainable material for applications such as solar-energy conversion and photoelectrochemical (PEC) water splitting; however, recent studies have shown that the performance can be limited by a very short charge-carrier diffusion length or exciton lifetime. In this study, we performed ultrafast studies on hematite nanoparticles of different shapes to determine the possible influence of particle shape on the exciton dynamics. Nanorice, multifaceted spheroidal nanoparticles, faceted nanocubes, and faceted nanorhombohedra were synthesized and characterized by using SEM and XRD techniques. Their exciton dynamics were investigated by using femtosecond transient absorption (TA) spectroscopy. Although the TA spectral features differ for the four samples studied, their decay profiles are similar, which can be fitted with time constants of 1-3 ps, approximately 25 ps, and a slow nanosecond component extending beyond the experimental time window that was measured (2 ns). The results indicate that the overall exciton lifetime is weakly dependent on the shape of the hematite nanoparticles, even though the overall optical absorption and scattering are influenced by the particle shape. This study suggests that other strategies need to be developed to increase the exciton lifetime or to lengthen the exciton diffusion length in hematite nanostructures.