David J. Neivandt

Implementing the Theory of Sum Frequency Generation Vibrational Spectroscopy: A Tutorial Review

Abstract The interfacial regions between bulk media, although often comprising only a fraction of the material present, are frequently the site of reactions and phenomena that dominate the macroscopic properties of the entire system. Spectroscopic investigations of such interfaces are often hampered by the lack of surface specificity of most available techniques. Sum frequency generation vibrational spectroscopy (SFS) is a non‐linear optical technique which provides vibrational spectra of molecules solely at interfaces. The spectra may be analysed to provide the polar orientation, molecular conformation, and average tilt angle of the adsorbate to the surface normal. This article is aimed at newcomers to the field of SFS, and via a tutorial approach will present and develop the general sum frequency equations and then demonstrate how the fundamental theory elucidates the important experimental properties of SFS.

Secretion without Golgi

A growing number of proteins devoid of signal peptides have been demonstrated to be released through the non‐classical pathways independent of endoplasmic reticulum and Golgi. Among them are two potent proangiogenic cytokines FGF1 and IL1α. Stress‐induced transmembrane translocation of these proteins requires the assembly of copper‐dependent multiprotein release complexes. It involves the interaction of exported proteins with the acidic phospholipids of the inner leaflet of the cell membrane and membrane destabilization. Not only stress, but also thrombin treatment and inhibition of Notch signaling stimulate the export of FGF1. Non‐classical release of FGF1 and IL1α presents a promising target for treatment of cardiovascular, oncologic, and inflammatory disorders. J. Cell. Biochem. 103: 1327–1343, 2008.

Method for Production of Polymer and Carbon Nanofibers from Water-Soluble Polymers

Nanometer scale carbon fibers (carbon nanofibers) are of great interest to scientists and engineers in fields such as materials science, composite production, and energy storage due to their unique chemical, physical, and mechanical properties. Precursors currently used for production of carbon nanofibers are primarily from nonrenewable resources. Lignin is a renewable natural polymer existing in all high-level plants that is a byproduct of the papermaking process and a potential feedstock for carbon nanofiber production. The work presented here demonstrates a process involving the rapid freezing of an aqueous lignin solution, followed by sublimation of the resultant ice, to form a uniform network comprised of individual interconnected lignin nanofibers. Carbonization of the lignin nanofibers yields a similarly structured carbon nanofiber network. The methodology is not specific to lignin; nanofibers of other water-soluble polymers have been successfully produced. This nanoscale fibrous morphology has not been observed in traditional cryogel processes, due to the relatively slower freezing rates employed compared to those achieved in this study.

Surface treatments of wood–plastic composites (WPCs) to improve adhesion

In an effort to improve the adhesive bonding between wood–plastic composites (WPCs) formulated with polypropylene and a commercial epoxy adhesive, surface treatments were performed to chemically and/or physically modify the surface of WPCs. The treatments were performed on extruded WPC that had been planed and consisted of chromic acid treatment, flame treatment, water treatment, flame then water treatment and water then flame treatment. The strength of the adhesive bonds of the treated samples was tested following ASTM D 905 and the maximum shear stress was calculated for each treatment. The chromic acid and flame treatments increased their respective average shear strengths by 97% and 67% compared to an untreated control group. The increase in bond strength due to these two treatments is believed to be a result of their oxidative mechanisms. The water treatment, which consisted of covering the planed surface of a WPC with water for 10 min, resulted in an increase in shear strength of 31% relative to the control. Characterization of the water-treated WPC surface with profilometry and scanning electron microscopy indicated that the likely mechanism for the increase in bond strength was the absorption of water and subsequent swelling of the wood present in the WPC, creating greater surface area for bonding. The combination of flame and water treatments showed increased shear strength relative to the individual treatments alone, indicating that the two processes might act synergistically to facilitate the formation of stronger adhesive bonds.

Characterizing the mechanism of improved adhesion of modified wood plastic composite (WPC) surfaces

To have a better knowledge of the phenomena that affect the adhesion characteristics of wood plastic composites (WPCs) a series of surface treatments was performed. The treatments consisted of chemical, mechanical, energetic, physical, and a combination of energetic and physical WPC surface modifications. After each treatment, the composite boards were bonded using a commercial epoxy adhesive, and bond shear strength was determined according to ASTM D 905. All the surface treatments, except the mechanical one, were performed and presented in a previous paper (W. Gramlich et al., J. Adhesion Sci. Technol. 20, 1873–1887 (2006)). Mechanical treatment and surface characterization for all the treatments were performed in the present study. The surface characterization included application of thermodynamic and spectroscopic techniques. Most of the surface treatments improved the adhesive bondability of wood plastic composites and, particularly, the smoothest WPC surfaces increased the shear strength by 100% with respect to the control. Thermodynamic measurements indicate that the WPCs low surface energy of about 25 mJ/m2, is likely due principally to the surface migration of a lubricant component used in the extrusion formulation. The surface energy increased over 45% with respect to the control samples after the chemical treatments. X-ray photoelectron spectroscopy analysis indicated that high oxidation levels of the WPC surfaces resulted in high surface energy and high bond shear strength.

P0-9 A Lateral Field Excited Acoustic Wave Sensor for the Detection of Saxitoxin in Water

In the United States, approximately 20% of all foodborne disease outbreaks result from the consumption of seafood products. Specifically, the disease Paralytic Shellfish Poisoning (PSP) is caused by consuming molluscan shellfish contaminated with a suite of neurotoxins the most potent of which is saxitoxin (STX). The current method for detecting STX is the mouse bioassay in which a mouse is exposed to a shellfish sample and the time required for the mouse to perish is noted. The length of time required for the mouse to die is used to estimate the level of STX in the original sample. Since this technique is a time consuming and costly laboratory-based procedure, a rapid in situ sensor is needed to detect STX levels in shellfish and in sea water so timely closures of shellfish grounds can be made to protect public health. In this work, a novel Lateral Field Excited (LFE) acoustic wave sensor, which has been successfully used for chemical and biological sensing, is employed to detect STX in water, proving itself as a feasible alternative to the mouse bioassay in STX detection.

Forced Air Plasma Treatment (FAPT) of Hybrid Wood Plastic Composite (WPC)–Fiber Reinforced Plastic (FRP) Surfaces

Forced atmospheric (air) plasma treatment (FAPT) was applied to wood plastic composite (WPC) and continuous glass fiber reinforced plastic (FRP) surfaces to improve their adhesive bonding properties. The FRP was composed of oriented continuous E-glass fibers in a polypropylene matrix, while the WPC was fabricated using wood flour, polypropylene and additives. The FAPT was applied using two levels of discharge length projected from the discharge head (2.5″ and 1″) to ionize the air, oxidize the surfaces and improve wettability. The treatment was performed by passing the electrode over either surface, five or ten times. Surface characterization consisted of thermodynamic (surface energy determination), chemical (X-ray photoelectron spectroscopy), mechanical (shear strength) and microscopic (atomic force microscopy (AFM)) analysis. The results indicate that the acid–base component of the surface energy for both WPC and FRP after FAPT correlates with an increase in wettability. X-ray photoelectron spectroscopy was performed on wood regions and non-wood regions of the WPC surfaces; the oxygen concentration increased to a larger extent in the non-wood regions. Bonding shear strength measurements indicated increases of 50% after FAPT on WPC surfaces (2.5″ discharge length, 1 pass) and up to 200% for the hybrid WPC–FRP. Atomic force microscopy measurements using a silicon tip probe showed increases in adhesive force interactions up to 56% on WPC surfaces post-FAPT.

Protein-Phospholipid Interactions in Nonclassical Protein Secretion: Problem and Methods of Study

Extracellular proteins devoid of signal peptides use nonclassical secretion mechanisms for their export. These mechanisms are independent of the endoplasmic reticulum and Golgi. Some nonclassically released proteins, particularly fibroblast growth factors (FGF) 1 and 2, are exported as a result of their direct translocation through the cell membrane. This process requires specific interactions of released proteins with membrane phospholipids. In this review written by a cell biologist, a structural biologist and two membrane engineers, we discuss the following subjects: (i) Phenomenon of nonclassical protein release and its biological significance; (ii) Composition of the FGF1 multiprotein release complex (MRC); (iii) The relationship between FGF1 export and acidic phospholipid externalization; (iv) Interactions of FGF1 MRC components with acidic phospholipids; (v) Methods to study the transmembrane translocation of proteins; (vi) Membrane models to study nonclassical protein release.

Comparison of Actin- and Glass-Supported Phospholipid Bilayer Diffusion Coefficients

The formation of biomimetic lipid membranes has the potential to provide insights into cellular lipid membrane dynamics. The construction of such membranes necessitates not only the utilization of appropriate lipids, but also physiologically relevant substrate/support materials. The substrate materials employed have been shown to have demonstrable effects on the behavior of the overlying lipid membrane, and thus must be studied before use as a model cushion support. To our knowledge, we report the formation and investigation of a novel actin protein-supported lipid membrane. Specifically, inner leaflet lateral mobility of globular actin-supported DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine) bilayers, deposited via the Langmuir-Blodgett/Langmuir Schaefer methodology, was investigated by z-scan fluorescence correlation spectroscopy across a temperature range of 20-44°C. The actin substrate was found to decrease the diffusion coefficient when compared to an identical membrane supported on glass. The depression of the diffusion coefficient occurred across all measured temperatures. These results indicated that the actin substrate exerted a direct effect on the fluidity of the lipid membrane and highlighted the fact that the choice of substrate/support is critical in studies of model lipid membranes.

Phospholipid Diffusion Coefficients of Cushioned Model Membranes Determined via Z-Scan Fluorescence Correlation Spectroscopy

Model cellular membranes enable the study of biological processes in a controlled environment and reduce the traditional challenges associated with live or fixed cell studies. However, model membrane systems based on the air/water or oil/solution interface do not allow for incorporation of transmembrane proteins or for the study of protein transport mechanisms. Conversely, a phospholipid bilayer deposited via the Langmuir-Blodgett/Langmuir-Schaefer method on a hydrogel layer is potentially an effective mimic of the cross section of a biological membrane and facilitates both protein incorporation and transport studies. Prior to application, however, such membranes must be fully characterized, particularly with respect to the phospholipid bilayer phase transition temperature. Here we present a detailed characterization of the phase transition temperature of the inner and outer leaflets of a chitosan supported model membrane system. Specifically, the lateral diffusion coefficient of each individual leaflet has been determined as a function of temperature. Measurements were performed utilizing z-scan fluorescence correlation spectroscopy (FCS), a technique that yields calibration-free diffusion information. Analysis via the method of Wawrezinieck and co-workers revealed that phospholipid diffusion changes from raftlike to free diffusion as the temperature is increased-an insight into the dynamic behavior of hydrogel supported membranes not previously reported.