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Komodo dragons are the largest living lizards and are the apex predators in their environs. They endure numerous strains of pathogenic bacteria in their saliva and recover from wounds inflicted by other dragons, reflecting the inherent robustness of their innate immune defense. We have employed a custom bioprospecting approach combining partial de novo peptide sequencing with transcriptome assembly to identify cationic antimicrobial peptides from Komodo dragon plasma. Through these analyses, we identified 48 novel potential cationic antimicrobial peptides. All but one of the identified peptides were derived from histone proteins. The antimicrobial effectiveness of eight of these peptides was evaluated against Pseudomonas aeruginosa (ATCC 9027) and Staphylococcus aureus (ATCC 25923), with seven peptides exhibiting antimicrobial activity against both microbes and one only showing significant potency against P. aeruginosa. This study demonstrates the power and promise of our bioprospecting approach to cationic antimicrobial peptide discovery, and it reveals the presence of a plethora of novel histone-derived antimicrobial peptides in the plasma of the Komodo dragon. These findings may have broader implications regarding the role that intact histones and histone-derived peptides play in defending the host from infection. Data are available via ProteomeXChange with identifier PXD005043.

Miniaturization of electronic devices to the level of single molecules requires detailed understanding of the mechanisms of their operation. One of the questions here is the identification of the role of structural alterations in charge separation and stabilization in photoactive complexes. To address this question, we calculate optimized molecular and electronic structures, and optical and vibrational spectra of l,l'-dimethyl 4,4'-bipyridinium-bis tetraphenylborate PQ(BPh(4))(2) complex ab initio using density functional theory approach and compare them with the experimentally observed UV-Vis and Raman spectra of the molecules in solid-state films. The results indicate that the association of PQ and BPh(4) leads to the formation of an internally ionized structure that is accompanied by the structural reorganization of both PQ (the twisting of pyridinium rings) and BPh(4) (phenyl rings rotation) moieties. The quanta of light do not seem to be directly involved in the formation of this ionized structure, but provide energy for fast recombination of the separated charges between BPh(4)(-) and PQ(2+). The high efficiency of the dark charge separation and the stabilization of separated charges in the complex permit the using of PQ(BPh(4))(2) in various charge-transfer devices like molecular probes, photovoltaic devices or chemical memory units.

Electron transfer (ET) through oxidized (QOPV) and reduced-protonated (HQOPV) forms of oligo(phenylene vinylene) quinone placed between two gold electrodes in the absence and presence of external water molecules is calculated using density functional theory with a nonequilibrium Green’s function method. The results show that the presence of hydrogen atoms as an internal component (in reduced-protonated form of the molecule) screens the stimulating effect of oxygen on QOPV conductivity and eliminates the efficiency of the molecule conductance at low bias voltages. The formation of a complex with water restores the HQOPV conductivity at low biases and opens several additional strong conductivity channels below the Fermi level, substantially improving the efficiency of ET between QOPV and the electrode, especially at longer distances between the molecule and the metal. This effect of water can be utilized in the construction of novel highly efficient electrochemically gated electronic devices. It also opens ...

Electron transmission parameters of oligo(phenylene vinylene) quinone (OPVQ) placed between two gold electrodes were calculated ab initio using density functional theory (DFT) with the nonequilibri...

Timely identification of biothreat organisms from large numbers of clinical or environmental samples in potential outbreak or attack scenario is critical for effective diagnosis and treatment. This study aims to evaluate the potential of resequencing arrays for this purpose. Albeit suboptimal, this report demonstrated that respiratory pathogen microarray version 1 can identify Bacillus anthracis, Francisella tularensis, Yersinia pestis and distinguish them from benign 'near neighbor' species in a single assay. Additionally, the sequence information can discriminate strains and possibly the sources of the strains. With further development, it is possible to use resequencing microarrays for biothreat surveillance.

The electron-transfer (ET) parameters for oriented and aligned monolayers of the bacterial photosynthetic reaction center (RC) from Rhodobacter sphaeroides formed on the top of self-assembled monolayers (SAMs) of alkanethiols of various lengths immobilized on gold electrode are estimated using cyclic voltammetry and photoelectrochemistry. Utilization of the unique polyHis tag in the protein and the Ni−NTA chelator complex in SAMs allows for specific protein orientation with the RC primary donor facing the electrode. To improve the efficiency of ET between the RC special pair and the electrode, an RC-Cyt complex was formed (J. Am. Chem. Soc. 2006, 128, 12044−12045). The results are analyzed in terms of integrated Marcus formalism, taking into account the density of electronic states in the metal. The dependence of the ET rate on the distance between RC and electrode demonstrates an adiabatic region up to 10 A, typical for other proteins, followed by a nonadiabatic area of electron tunneling with a β-factor...

Simultaneous testing for detection of infectious pathogens that cause similar symptoms (e.g., acute respiratory infections) is invaluable for patient treatment, outbreak prevention, and efficient use of antibiotic and antiviral agents. In addition, such testing may provide information regarding possible coinfections or induced secondary infections, such as virally induced bacterial infections. Furthermore, in many cases, detection of a pathogen requires more than genus/species-level resolution, since harmful agents (e.g., avian influenza virus) are grouped with other, relatively benign common agents, and for every pathogen, finer resolution is useful to allow tracking of the location and nature of mutations leading to strain variations. In this study, a previously developed resequencing microarray that has been demonstrated to have these capabilities was further developed to provide individual detection sensitivity ranging from 10 1 to 10 3 genomic copies for more than 26 respiratory pathogens while still retaining the ability to detect and differentiate between close genetic neighbors. In addition, the study demonstrated that this system allows unambiguous and reproducible sequence-based strain identification of the mixed pathogens. Successful proof-of-concept experiments using clinical specimens show that this approach is potentially very useful for both diagnostics and epidemic surveillance.

The identification and sequencing of novel cationic antimicrobial peptides (CAMPs) have proven challenging due to the limitations associated with traditional proteomics methods and difficulties sequencing peptides present in complex biomolecular mixtures. We present here a process for large-scale identification and de novo-assisted sequencing of newly discovered CAMPs using microparticle capture followed by tandem mass spectrometry equipped with electron-transfer dissociation (ETD). This process was initially evaluated and verified using known CAMPs with varying physicochemical properties. The effective parameters were then applied in the analysis of a complex mixture of peptides harvested from American alligator plasma using custom-made (Bioprospector) functionalized hydrogel particles. Here, we report the successful sequencing process for CAMPs that has led to the identification of 340 unique peptides and the discovery of five novel CAMPs from American alligator plasma.

Cationic antimicrobial peptides and their therapeutic potential have garnered growing interest because of the proliferation of bacterial resistance. However, the discovery of new antimicrobial peptides from animals has proven challenging due to the limitations associated with conventional biochemical purification and difficulties in predicting active peptides from genomic sequences, if known. As an example, no antimicrobial peptides have been identified from the American alligator, Alligator mississippiensis, although their serum is antimicrobial. We have developed a novel approach for the discovery of new antimicrobial peptides from these animals, one that capitalizes on their fundamental and conserved physico-chemical properties. This sample-agnostic process employs custom-made functionalized hydrogel microparticles to harvest cationic peptides from biological samples, followed by de novo sequencing of captured peptides, eliminating the need to isolate individual peptides. After evaluation of the peptide sequences using a combination of rational and web-based bioinformatic analyses, forty-five potential antimicrobial peptides were identified, and eight of these peptides were selected to be chemically synthesized and evaluated. The successful identification of multiple novel peptides, exhibiting antibacterial properties, from Alligator mississippiensis plasma demonstrates the potential of this innovative discovery process in identifying potential new host defense peptides.

There is an increasing recognition that detailed nucleic acid sequence information will be useful and even required in the diagnosis, treatment and surveillance of many significant pathogens. Because generating detailed information about pathogens leads to significantly larger amounts of data, it is necessary to develop automated analysis methods to reduce analysis time and to standardize identification criteria. This is especially important for multiple pathogen assays designed to reduce assay time and costs. In this paper, we present a successful algorithm for detecting pathogens and reporting the maximum level of detail possible using multi-pathogen resequencing microarrays. The algorithm filters the sequence of base calls from the microarray and finds entries in genetic databases that most closely match. Taxonomic databases are then used to relate these entries to each other so that the microorganism can be identified. Although developed using a resequencing microarray, the approach is applicable to any assay method that produces base call sequence information. The success and continued development of this approach means that a non-expert can now perform unassisted analysis of the results obtained from partial sequence data.

The exponential growth of pathogen nucleic acid sequences available in public domain databases has invited their direct use in pathogen detection, identification, and surveillance strategies. DNA microarray technology has offered the potential for the direct DNA sequence analysis of a broad spectrum of pathogens of interest. However, to achieve the practical attainment of this potential, numerous technical issues, especially nucleic acid amplification, probe specificity, and interpretation strategies of sequence detection, need to be addressed. In this report, we demonstrate an approach that combines the use of a custom-designed Affymetrix resequencing Respiratory Pathogen Microarray (RPM v.1) with methods for microbial nucleic acid enrichment, random nucleic acid amplification, and automated sequence similarity searching for broad-spectrum respiratory pathogen surveillance. Successful proof-of-concept experiments, utilizing clinical samples obtained from patients presenting adenovirus or influenza virus-induced febrile respiratory illness (FRI), demonstrate the ability of this approach for correct species- and strain-level identification with unambiguous statistical interpretation at clinically relevant sensitivity levels. Our results underscore the feasibility of using this approach to expedite the early surveillance of diseases, and provide new information on the incidence of multiple pathogens.

Plants and photosynthetic bacteria contain protein−molecular complexes that harvest photons with nearly optimum quantum yield and an expected power conversion efficiency exceeding 20%. In this work, we demonstrate the integration of electrically active photosynthetic protein−molecular complexes in solid-state devices, realizing photodetectors and photovoltaic cells with internal quantum efficiencies of approximately 12%. Electronic integration of devices is achieved by self-assembling an oriented monolayer of photosynthetic complexes, stabilizing them with surfactant peptides, and then coating them with a protective organic semiconductor.

With restrictions on the use of metallic biocides in aquatic antifouling coatings, it is important to develop new methods to both contain and deliver these alternative compounds from marine coatings systems. Utilization of microencapsulation is one approach to the delivery of biocides that has not been utilized in the mainstream of antifouling paint formulations. When formulating next generation paints that utilize hydrophobic nonmetallic biocides, it is necessary to develop an understanding of the release kinetics of the compounds from model polymeric coatings in order to better develop methods for providing long-term efficacy. The biocide 4,5-dichloro-2-n-octyl-4-isothiazolin-3-one is a nonmetallic and nonenvironmentally persistent biocide that has been registered in several countries for use as an antifouling agent and has gained approval by the U.S. Environmental Protection Agency. The release characteristics of this biocide from copper microtubules as well as polymeric films were determined by high performance liquid chromatography.

Results reported in this study provide, for the first time, a simple approach to tune the diameter of nanoscale diacetylenic phospholipid-based tubules. We have found a clear correlation between the n segments of the acyl chains in diacetylenic phosphocholines and the diameter of nanotubules formed from lipid mixtures containing diacetylenic phosphocholine and a short-chain “spacer” lipid. Microscopic structures in the aqueous dispersions of equimolar mixtures of diacetylenic phospholipid, DCm,nPCs, and saturated spacer lipids (DCm‘PCs) were studied to understand and formulate the basis for developing the “design” rules for the formation of stable nanoscale structures. An increase in the number of n resulted in an increase in the diameter of the tubules produced by the mixtures. Circular dichroism (CD) spectra of these mixtures were analyzed and the very complex CD spectra clearly confirmed the chiral nature of the nanotubule architecture. Tubules from most of the mixtures demonstrated long-term storage s...

This Letter describes two approaches for sensing changes in spiking cells when only a limited amount of spike data is available. The first method detects changes in dynamically constructed local expansion rates, and the other uses spike area distributions. These two methods were tested on time series from cultured neurons. Over-sampled data was generated from experiments on single cells before and after being treated with a small concentration of channel blocker, but relatively few spikes were recorded. In the spontaneously spiking cells, the local expansion rates showed a sensitivity that correlated with the channel concentration level, while the driven cells showed no such correlation. Spike area distributions showed measurable differences between control and treated conditions for both types of spiking, and a much higher degree of sensitivity. Because these methods are based on analysis of short time series analysis, they might provide novel means for cell drug and toxin detection.

Many types of amphiphilic molecules self-assemble in solution to form cylindrical tubules and helical ribbons. Some examples include diacetylenic lipids, amide amphiphiles, bile, and diblock copolymers. Researchers have proposed a variety of models to explain the formation of these high-curvature structures. These models can be divided into two broad categories: models based on the chiral elastic properties of membranes, and models based on other effects, including electrostatic interactions, elasticity of orientational order, and spontaneous curvature. In this paper, we review the range of theoretical approaches and compare them with relevant experiments. We argue that the category of models based on chiral elastic properties provides the most likely explanation of current experimental results, and we propose further theoretical and experimental research to give a more detailed test of these models.

Nanoscale structures have been found to self-assemble in a binary mixture of a long-chain, diacetylenic phospholipid and a short chain, saturated lipid. We observe unusual chiral-optical signatures of nanotubule, twisted ribbon, and microtubule morphologies that can be used to monitor their temporal and thermal stability. Circular dichroism results suggest that chiral packing of the lipids drives formation of these aggregates. The ease of formation, stability, and robust behavior of these lipid cylinders suggest that they have potential use in applications requiring high aspect ratio nanomaterials.

We have demonstrated a new approach for imaging nanoscale patterns on three-dimensional submicrometer structures using charged particles. Nanoparticle structures were assembled onto lipid tubules through the sequential adsorption of oppositely charged polymers and silica spheres. For tubules of the zwitterionic lipid DC8,11PC, this process leads to the formation of caps on the ends of the tubules, with 50−100 silica spheres in each cap. For tubules of DC8,11PC mixed with 2% of the charged lipid DC8,9PEOH, the sequential adsorption leads to both end caps and helices of nanoparticles winding around the interior of the tubules. These results give new insight into the pattern of charge in lipid tubules.

Recent fundamental research has revealed the possibility to rationally form supramolecular aggregates. These self-assembled structures range in size from several nanometers (containing a few molecules) to hundreds of microns (containing billions of molecules). The ability to control both the morphology and size of these aggregates through modifications of both molecular structure and solution conditions suggests the possibility that they might be exploited to solve important problems in the development of advanced material applications. It is also possible that the lesson learned for the study of chiral behavior in lipid may have some relevance to the study of the ways in which polypeptide tapes self assemble in to fibers. Tubules formed from phospholipids constitute a unique self-assembled microstructure and show promise in a number of biotechnological applications [1]. This article will provide an outline of the talk that was given in June 1999 at the International Meeting on Polypeptide self-assembly held in Crete. It will discuss advances that have led to the understanding of chiral behavior and the subsequent ability to control the structure of lipid-derived tubules and the resulting impact of this on materials applications. Modifications to the molecular structure of lipids have been made to increase the versatility of liposomes as delivery agents for pharmaceutical agents [2]. Phospholipids with photopolymerizable diacetylenic moieties in the acyl chains were synthesized to increase the durability of liposomes [3-5]. However, Yager and Schoen found that some polymerizable lipids selfassemble to form hollow, cylindrical structures known as tubules [6]. Remarkably, tens of billions of molecules self-organize to form these

Several techniques for controlling the morphology of self-assembled lipid tubules are investigated by using circular dichroism spectroscopy and electron microscopy. These studies show that variations in the molecular structure of the diacetylenic phospholipid, lipid concentration, and solution conditions allow for control of the number of bilayers in the tubule walls, but not their diameter. Tubules formed in water and mixtures of alcohols adopt interesting morphologies and allow for further control of tubule structure. In addition, studies of lipids with different acyl chains show that tubule morphology is sensitive to the degree of order within the chains. Because of the chiral molecular architecture in lipid tubules, intense peaks in their circular dichroism spectra are observed. These peaks can be monitored to obtain information on the tubule morphology. This information is correlated to direct observations made using electron microscopy. Results of these studies have led to the optimization of large ...

Circular dichroism and calorimetry have been used to study the melting of self-assembled phospholipid tubules in alcohol/water solutions. The tubules are found to melt either continuously or discontinuously, depending on the type of alcohol, the alcohol/water ratio, and the lipid concentration. At high proportions of alcohol and low lipid concentrations, the ellipticity continuously decreases with temperature and a very broad peak in the specific heat is observed. In solutions with lower proportions of alcohol or large lipid concentrations, a large drop in ellipticity is accompanied by a sharp peak in the specific heat when the acyl chains disorder. The CD and specific heat measurements can be explained in terms of two distinct thermodynamic processes: the discontinuous melting is a first-order transition of the lipid bilayers from the ordered Lβ‘ phase to the disordered Lα phase, while the continuous melting reflects an increase in the lipid solubility with temperature. These results show that the solve...

We present a general theory for the equilibrium structure of cylindrical tubules and helical ribbons of chiral lipid membranes. This theory is based on a continuum elastic free energy that permits variations in the direction of molecular tilt and in the curvature of the membrane. The theory shows that the formation of tubules and helical ribbons is driven by the chirality of the membrane. Tubules have a first-order transition from a uniform state to a helically modulated state, with periodic stripes in the tilt direction and ripples in the curvature. Helical ribbons can be stable structures, or they can be unstable intermediate states in the formation of tubules., Comment: 43 pages, including 12 postscript figures, uses REVTeX 3.0 and epsf.sty

Lipid-based tubules serve as models for the development of advanced materials based upon molecular self-assembly. The processes by which tubules are formed and how they are coated with metals (nickel in the Figure) or used as templates in order to increase the strength of the final material are described. Their electrical and magnetic properties are discussed.

Polymerizable phospholipids are organic monomers that are able to self-assemble into membranes. This is quite similar to the self assembly of naturally occurring lipid membranes found in biological systems. The polymerizable lipids can then be polymerized to stabilize these membranes. These stabilized structures have a number of different morphologies which offer a variety of technically attractive features. This article reviews the chemical and physical properties of these materials in terms of their technological applications.

The area of self-assembled ultrafine particulate-based composites (nano composites) has been a major thrust in advanced material development. In this paper we report on the application of biologically derived, self-assembled cylindrical microstructures to form advanced composite materials for controlled release applications. These microstructures (we call them tubules) have many applications in the material sciences. This paper will focus on the potential for rationally controlling the fabrication of submicron microstructures for controlled release applications.

We present a continuum theory for the self-assembly of cylindrical tubules from chiral lipid bilayers in any tilted fluid phase. This theory shows that tubule formation is driven by an intrinsic bending force due to molecular chirality, and gives the radius in terms of the continuum parameters. The radius diverges as an untilted phase is approached. The theory also predicts that the tilt direction is modulated in a helical striped pattern on the tubule. This striped pattern is consistent with helical patterns observed in electron micrographs of lipid tubules.

The tubule-forming lipid 1,2-bis (10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine has been dispersed in water as a suspension of large vesicles. The temperature of the dispersion was dropped in small steps from 45°C to 37°C, and at each step aliquots of the sample were flash-frozen in liquid propane for freeze-fracture replication. In this temperature range most of the vesicles collapse, losing their internal water, and transform to tubules. The vesicles display surface roughness at 43°C, which becomes interspersed with smooth regions at 40°C. At 37°C the smooth areas appear to become predominant and the vesicles roll themselves up into the hollow cylindrical form of tubules. This process is partly reversible, since rewarming this preparation to 50°C leads to reformation of vesicles that display some surface roughness. Low and wide-angle X-ray scattering was used to follow the disorder-order lipid hydrocarbon chain transition on cooling for samples prepared with tightly packed tubules (centrifugation pellet) or highly concentrated lipid-water lamellar phases. In both cases the transition started at about 40°C, being rapidly achieved in the case of the tubule pellet but showing coexistence for several days at room temperature of disordered and ordered lipid in the case of the lamellar sample.

The single-molecule conductivity of quinone-oligo(phenylene vinylene) (Q-OPV) attached to a gold substrate was studied using electrochemical scanning tunnelling microscopy. The results show that the molecule has two discrete conductivity states: a low-conductivity state, when it is oxidized, and a high-conductivity state, when reduced. The electron transport through the molecule in both states occurs via coherent tunnelling. The molecular conductivity in either oxidation state is independent from the electrochemical gate potential; however, the gate potential can be used to switch the oxidation state of the molecule. Numerical calculations suggest that the highest occupied molecular orbital (HOMO) of Q-OPV controls tunnelling through the molecule and that the independence of conductivity from the electrochemical gate in either oxidation state originates from strong penetration of HOMO into the substrate. In addition, the greater delocalization of HOMO in the reduced state than in the oxidized state explains the greater conductivity of Q-OPV in the former than in the latter.

A multidisciplinary approach to the fabrication of biologically based microstructure composites for vacuum field emission is described. Diacetylenic lipid 1,2-bis(10,12-tricosadiynol)-sn-glycero-3-phosphocholine (DC 8.9 PC) was self-assembled to form hollow cylindrical tubules approximately 0.5 μm in average diameter and 50–80 μm long. Following the deposition of nickel on the inner and outer tubule surfaces by an electroless plating method, the nickel-plated tubules were magnetically aligned in an epoxy matrix to form a composite material. Subsequent selective removal of the matrix provided a composite base template of oriented exposed tubules. The tubule template was coated with a thin sputtered gold film to provide the surface electrical contact. The resultant microstructures demonstrated vacuum field emission of current I > 10 μ A at relatively low applied macroscopic electric fields (about 60–150 kV cm −1 ).

The effect of modification of the polar headgroup of diacetylenic phospholipids on bilayer morphology and monolayer properties has been investigated. The lipids were prepared by substituting the choline portion of 1,2-bis(10, 12-tricosadiynoyl)-sn-glycero-3-phosphocholine with the glycols HO(CH 2 ) n OH ( n = 2, 3, 4), by means of a phospholipase D catalyzed transphosphatidylation. In the presence of CuCl 2 (pH 5.6 and ionic strength 0.18), the lipid with n = 2, produced a bimodal population of small diameter (0.1 μm) and large diameter (0.9 μm) tubules, the lipid for n = 3 produced a similar bimodal distribution of tubules except that the diameter of the smaller tubules increased to 0.3 μm. No small diameter tubules were formed from the lipid where n = 4. An increase or decrease either in the pH or ionic strength decreased the yield of tubules and affected the formation of the small diameter tubules, respectively. The counteranion of the metal salt present in the aqueous medium was also found to affect tubule diameter. The molecular area of the lipids was 70 A 2 /molecule ( n = 2), 105 A 2 /molecule ( n = 3) and 160 A 2 /molecule ( n = 4). Monolayer studies suggested that the packing behavior of lipids at the air-water interface in the low surface pressure region was influenced by the subphase pH, ionic strength and counteranions.

A top surface imaging approach for the fabrication of submicron features on solid substrates has been developed. A monolayer film is exposed to patterned deep ultraviolet radiation, then selectively metallized using electroless deposition such that a thin metal layer (200-400 A) is deposited only in the unexposed areas. The film/metal assembly is a highly effective mask for reactive ion etching which can subsequently be stripped from the substrate after feature definition. Features with 0.3 μm line width in polysilicon and working transistor test structures have been produced using this process

Patterned deep UV irradiation of organosilane self-assembled monolayer (SAM) films caused photocleavage of the organic groups in the molecule, and creates alternating regions of intact film and hydrophilic, surface silanol moieties. The exposed regions can undergo a second chemisorption reaction to produce an assembly of SAMs in the same molecular plane. The patterned SAM films can also act as a template for selective build-up of materials in the z-direction. The use of UV patterned silane SAM films as imaging layers for optical lithography has been demonstrated. The exposed films are selectively metallized using electroless deposition to produce a thin metal layer only in the unexposed areas. The film/metal assembly is a highly resistive barrier to reactive ion etching (RIE) for pattern transfer into the substrate. Features to 0.5 μm line width and working transistor test structures have been produced using this process.

The construction of efficient light energy converting (photovoltaic and photo-electronic) devices is a current and great challenge in science and technology and one that will have important economic consequences. Several innovative nanoelectronic materials were proposed to achieve this goal, semiconductor quantum dots, metallic nanowires and carbon nanotubes (CNT) are among them. As a charge separating unit for light energy conversion, we propose the utilization of the most advanced photoelectronic material developed by nature, photosynthetic reaction center proteins. As a first step in this direction, we constructed a novel bioinorganic nanophotoelectronic material with photoactive photosynthetic reaction center (RC) proteins encapsulated inside a multiwall CNT arrayed electrode. The material consists of photosynthetic RC-cytochrome complexes acting as charge separating units bound to the inner walls of a CNT electrode and ubiquinone-10 (Q2) serving as a soluble electron-transfer mediator to the counter electrode. The proteins were immobilized inside carbon nanotubes by a Ni(NTA)-alkane-pyrene linker, forming a self-assembled monolayer (SAM) on the surface of inner CNT walls and allowing for unidirectional protein orientation. The material demonstrates an enhanced photoinduced electron transfer rate and shows substantial improvement in photocurrent density compared to that obtained with the same proteins when immobilized on planar graphite (HOPG) electrode. The results suggest that protein encapsulation in precisely organized arrayed tubular electrode architecture can considerably improve the performance of photovoltaic, photoelectronic, or biofuel cell devices. They demonstrate the potential for substantial advantages of precisely organized nano electrode tubular arrayed architecture for variety biotechnological applications.

Zoonotic microbes have historically been, and continue to emerge as, threats to human health. The recent outbreaks of highly pathogenic avian influenza virus in bird populations and the appearance of some human infections have increased the concern of a possible new influenza pandemic, which highlights the need for broad-spectrum detection methods for rapidly identifying the spread or outbreak of all variants of avian influenza virus. In this study, we demonstrate that high-density resequencing pathogen microarrays (RPM) can be such a tool. The results from 37 influenza virus isolates show that the RPM platform is an effective means for detecting and subtyping influenza virus, while simultaneously providing sequence information for strain resolution, pathogenicity, and drug resistance without additional analysis. This study establishes that the RPM platform is a broad-spectrum pathogen detection and surveillance tool for monitoring the circulation of prevalent influenza viruses in the poultry industry and in wild birds or incidental exposures and infections in humans.

Reversible conductance switching in single quinone-oligo(phenylene vinylene) (Q-OPV) molecules was demonstrated using electrochemical STM. The switching was achieved by application of electrochemical potential to the substrate supporting the molecule. The ratio of conductances between the high- and low-conductivity states is over 40. The high-conductivity state is ascribed to strong electron delocalization of the fully conjugated hydroquinone-OPV structure, whereas the low-conductivity state is characterized by disruption of electron delocalization in the quinone-OPV structure.

Designs, calculations, and initial data are presented from a program investigating the use of biomolecular and eutectic composite microstructures as vacuum field-emission cathodes. Calculations, supported by the initial data, indicate that these electron sources should be capable of macroscopic beam current densities, J>or=100 A/cm/sup 2/, without the formation of a surface plasma. The absence of a plasma allows these cathodes to operate as a long-pulse to DC electron sources. The designs avoid the formation of surface plasma by forcing the current emitted from the tips to transit a thin layer of silicon. The natural high-field current-limiting nature of the silicon serves to prevent the ablation of tip structures and the subsequent formation of cathode plasma. Initial data obtained with these microstructures has demonstrated Fowler-Nordheim characteristic emission. Coated bio-molecular composite cathodes have demonstrated stable DC current densities of approximately 100 mA/cm/sup 2/, and the eutectic composite cathodes have demonstrated similarly stable DC current densities of approximately 1 A/cm/sup 2/. >

The construction of efficient light energy converting (photovoltaic and photoelectronic) devices is a current and great challenge in science and technology and one that will have important economic consequences. Here we show that the efficiency of these devices can be improved by the utilization of a new type of nano-organized material having photosynthetic reaction center proteins encapsulated inside carbon nanotube arrayed electrodes. In this work, a generically engineered bacterial photosynthetic reaction center protein with specifically synthesized organic molecular linkers were encapsulated inside carbon nanotubes and bound to the inner tube walls in unidirectional orientation. The results show that the photosynthetic proteins encapsulated inside carbon nanotubes are photochemically active and exhibit considerable improvement in the rate of electron transfer and the photocurrent density compared to the material constructed from the same components in traditional lamella configuration.

The photosynthetic reaction center (RC) is one of the most advanced light sensing and energy converting materials developed by Nature. Its coupling with inorganic surfaces is attractive for the identification of the mechanisms of interprotein electron transfer (ET) and for the possible applications for the construction of protein-based innovative photoelectronic and photovoltaic devices. Using genetically engineered bacterial RC proteins and specifically synthesized organic linkers, we were able to construct self-assembled and aligned biomolecular surfaces on various electrodes, including gold, carbon, indium tin oxide (ITO), highly ordered pyrrolytic graphite (HOPG) and carbon nanotube (CNT) arrays. Our results show that, after immobilization on the electrodes, the photosynthetic RC can operate as a highly efficient photosensor, optical switch, and photovoltaic device.

The gene transfer agent (GTA) is a phage-like particle capable of exchanging double-stranded DNA fragments between cells of the photosynthetic bacterium Rhodobacter capsulatus. Here we show that the major capsid protein of GTA, expressed in E. coli , can be assembled into prohead-like structures in the presence of calcium ions in vitro. Transmission electron microscopy (TEM) of uranyl acetate staining material and thin sections of glutaraldehyde-fixed material demonstrates that these associates have spherical structures with diameters in the range of 27–35 nm. The analysis of scanning TEM images revealed particles of mass ∼ 4.3 MDa, representing 101 ± 11 copies of the monomeric subunit. The establishment of this simple and rapid method to form prohead-like particles permits the GTA system to be used for genome manipulation within the photosynthetic bacterium, for specific targeted drug delivery, and for the construction of biologically based distributed autonomous sensors for environmental monitoring.

The aggregate is repre-sented as a tethered network connected by elastic springs; ateach node in the network a vector variable describes the localaverage molecular orientation. The system evolves via theMetropolis algorithm, governed by a free energy functionalthat takes into account bend, stretch, and chiral elastic terms(see Fig. 1).We found that aggregate curvature changes smoothlyfrom cylindrical to saddle-like as a function of elasticmoduli. We also demonstrated that, contrary to intuition, ag-gregates of either handedness may form from material of asingle chirality, depending on molecular tilt orientation.This work was supported by the U.S. Navy and the Na-tional Science Foundation DMR-0116090. Acknowledgmentis made to the donors of the American Chemical SocietyPetroleum Research Fund for partial support of this research.

Many biological and synthetic materials self-assemble into helical or twisted aggregates. The shape is determined by a complex interplay between elastic forces and the orientation and chirality of the constituent molecules. We study this interplay through Monte Carlo simulations, with an accelerated algorithm motivated by the growth of an aggregate out of solution. The simulations show that the curvature changes smoothly from cylindrical to saddle-like as the elastic moduli are varied. Remarkably, aggregates of either handedness form from molecules of a single handedness, depending on the molecular orientation., 4 pages, including 4 postscript figures, uses REVTeX 4

Two research areas currently under study, lipid-based tubules and optical nanolithography, are highlighted, and the potential technological impact of the work is discussed. One of the first efforts in the liposome field was to try to improve liposome performance by making them stronger and more stable, so that they would be less likely to break open or leak their contents when sheared, heated or subjected to other forms of stress. This was achieved by cross-linking. Exposed lipid headgroups on the tubule surface proved to be susceptible to the attachment of catalysts, which allowed the microstructures to be electrolessly coated with metal. Once the lipid structures have been metalized, the resulting microstructures are quite robust, and compatible with most material environments. An optical lithography process has been developed and described for fabrication of high-resolution microstructures of metal and other materials on a variety of substrates. The process has applications in numerous areas of microcircuit lithography. >

Studies on polymerizable phospholipids, are reported with an emphasis on diacetylenic lipids. By incorporating a diacetylenic moiety two specific goals are achieved; (1) modification of membrane morphologies, and (2) stabilization of the resultant microstructures. To explore the properties of diacetylenic phosphatides, the authors have synthesized and characterized a number of phospholipids. This report deals with the properties of aqueous dispersion of these diacetylenic lipids. >