Remote electronic control of DNA hybridization through inductive coupling to an attached metal nanocrystal antenna

Fast complementation of split fluorescent protein triggered by DNA hybridization

Fluorescent proteins have proven to be excellent reporters and biochemical sensors with a wide range of applications. In a split form, they are not fluorescent, but their fluorescence can be restored by supplementary protein-protein or protein-nucleic acid interactions that reassemble the split polypeptides. However, in prior studies, it took hours to restore the fluorescence of a split fluorescent protein because the formation of the protein chromophore slowly occurred de novo concurrently with reassembly. Here we provide evidence that a fluorogenic chromophore can self-catalytically form within an isolated N-terminal fragment of the enhanced green fluorescent protein (EGFP). We show that restoration of the split protein fluorescence can be driven by nucleic acid complementary interactions. In our assay, fluorescence development is fast (within a few minutes) when complementary oligonucleotide-linked fragments of the split EGFP are combined. The ability of our EGFP system to respond quickly to DNA hybridization should be useful for detecting the kinetics of many other types of pairwise interactions both in vitro and in living cells.

Ultrafast Cooling of Photoexcited Electrons in Gold Nanoparticle−Thiolated DNA Conjugates Involves the Dissociation of the Gold−Thiol Bond

Using UV-visible extinction spectroscopy and femtosecond pump-probe transient absorption spectroscopy, we have studied the effect of femtosecond laser heating on gold nanoparticles attached to DNA ligands via thiol groups. It is found that femtosecond pulse excitation of the DNA-modified nanoparticles at a wavelength of 400 nm leads to desorption of the thiolated DNA strands from the nanoparticle surface by the dissociation of the gold-sulfur bond. The laser-initiated gold-sulfur bond-breaking process is a new pathway for nonradiative relaxation of the optically excited electrons within the DNA-modified gold nanoparticles, as manifested by a faster decay rate of the excited electronic distribution at progressively higher laser pulse energies. The experimental results favor a bond dissociation mechanism involving the coupling between the photoexcited electrons of the nanoparticles and the gold-sulfur bond vibrations over one involving the conventional phonon-phonon thermal heating processes. The latter processes have been observed previously by our group to be effective in the selective photothermal destruction of cancer cells bound to anti-epidermal growth factor receptor-conjugated gold nanoparticles.

Degradation of Protein in Nanoplasma Generated around Gold Nanoparticles in Solution by Laser Irradiation

We developed a method of protein degradation in an aqueous solution containing gold nanoparticles by irradiation of a pulse laser. In the present study, lysozyme was used as an example. Lysozyme degradation proceeded most efficiently when a pH of the solution was adjusted so that it was at the isoelectric point. The scheme of the lysozyme degradation is as follows: (1) Lysozyme molecules in the solution are neutralized and adsorbed on the gold nanoparticles with its pH value adjusted at the isoelectric point, (2) nanoplasma is generated in the close vicinity of a gold nanoparticle which is excited by an intense 532-nm laser, (3) lysozyme molecules in the nanoplasma are degraded into small fragments. Lysozyme degradation does not proceed efficiently at a pH value deviated from the isoelectric point because the lysozyme molecules are dissolved uniformly so that only a small portion of the lysozyme molecules are located in the vicinity of gold nanoparticles which create the nanoplasma.

Temperature-programmed assembly of DNA:Au nanoparticle bioconjugates

Temperature has been used to control the order of assembly events in a solution containing three types of particles to be linked by two different sets of complementary DNA. At higher temperatures, only the duplexes having higher thermal stability were able to form. By starting at a high temperature and then cooling the sample, these more stable sequences hybridized first, followed by the less stable sequences at lower temperatures. Because of the use of thiolated DNA on Au particles, some loss and exchange of the DNA strands occurred at elevated temperatures. However, since cooperativity favors the "correct" assemblies, Au-S bond lability did not appreciably impact the order of the assembly process. Temperature programming combines the selectivity of DNA-directed assembly with the ability to control the order in which several complementary strands hybridize in a common solution and could contribute to the synthesis of more complex nanostructured materials.

Nanoparticle-mediated local and remote manipulation of protein aggregation

The local heat delivered by metallic nanoparticles selectively attached to their target can be used as a molecular surgery to safely remove toxic and clogging aggregates. We apply this principle to protein aggregates, in particular to the amyloid beta protein (Abeta) involved in Alzheimer's disease (AD), a neurodegenerative disease where unnaturally folded Abeta proteins self-assemble and deposit forming amyloid fibrils and plaques. We show the possibility to remotely redissolve these deposits and to interfere with their growth, using the local heat dissipated by gold nanoparticles (AuNP) selectively attached to the aggregates and irradiated with low gigahertz electromagnetic fields. Simultaneous tagging and manipulation by AuNP of Abeta at different stages of aggregation allow both, noninvasive exploration and dissolution of molecular aggregates.

DNA nanomechanical switches under folding kinetics control

Existing DNA nanodevices operate at equilibrium under changes in solution composition. We propose an alternative DNA switch design that can be driven and maintained out of equlibrium, under fixed chemical conditions. Moderate cooling rate after heat denaturation drives the switch to its lowest energy conformation, while rapid cooling (>100 degrees C/ms) locks the molecule in a unique alternative conformation that is retained over weeks at room temperature. This reversible process is probed using fluorescent energy transfer. DNA switches operating out of equilibrium should be more amenable to nanotechnology applications and scalable integration.

Gold nanoparticle-cytochrome C complexes: the effect of nanoparticle ligand charge on protein structure

We report the effect of nanoparticle ligand charge on the structure of a covalently, site-specifically linked protein. Au nanoparticles with positive, negative, and neutral ligands were appended to a specific cysteine, C102, of Saccharomyces cerevisiae cytochrome c. Conjugates were purified by HPLC or gel electrophoresis. Circular dichroism spectroscopy shows that changing the nanoparticle ligand dramatically influences the attached cytochrome c structure. The protein retains its structure with neutral ligands but denatures in the presence of charged species. This is rationalized by the electrostatic interaction of amino acids in the local vicinity of C102 with the endgroups of the ligand.

A DNA ring acting as a thermal ratchet

Several DNA nanomotors have been recently constructed in laboratories worldwide. These machines are, however, relatively slow and do not perform continuous rotations. We have recently proposed a rotary DNA nanomachine that shows a continuous rotation with a frequency of 10(2)-10(4) Hz. This motor is a closed DNA ring whose elastic features are tuned such that it can be externally driven via e.g. periodic temperature changes. As a result, the twirling ring propels itself through the fluid with a speed of tens of nanometres up to a few microns per second. The current paper gives a more detailed presentation of this motor and provides a derivation of the low- and high-frequency asymptotic behaviour of thermal ratchets in general.

Protein components for nanodevices

A long-term goal of nanobiotechnology is to build tiny devices that respond to the environment, perform computations and carry out tasks. Considerable progress has been made in building protein components for such devices, and here we describe examples, including self-assembling protein arrays, pores with triggers and switches, and motor proteins harnessed for specific tasks. A major issue that has been successfully addressed in this recent work is the interface between the proteins and other components of the system, such as a metal surface. While further progress is expected in the coming years, the assembly of devices from the components has seen more limited accomplishments. For example, although a wide variety of sensors based on nanobiotechnology has been developed, unresolved problems still confront the construction of complex nanobioelectronic circuits, and the development of nanorobotics with biological components remains a distant dream.

Integrated nanoparticle-biomolecule hybrid systems: synthesis, properties, and applications

Nanomaterials, such as metal or semiconductor nanoparticles and nanorods, exhibit similar dimensions to those of biomolecules, such as proteins (enzymes, antigens, antibodies) or DNA. The integration of nanoparticles, which exhibit unique electronic, photonic, and catalytic properties, with biomaterials, which display unique recognition, catalytic, and inhibition properties, yields novel hybrid nanobiomaterials of synergetic properties and functions. This review describes recent advances in the synthesis of biomolecule-nanoparticle/nanorod hybrid systems and the application of such assemblies in the generation of 2D and 3D ordered structures in solutions and on surfaces. Particular emphasis is directed to the use of biomolecule-nanoparticle (metallic or semiconductive) assemblies for bioanalytical applications and for the fabrication of bioelectronic devices.

Expanding the optical trapping range of gold nanoparticles

We demonstrate stable three-dimensional (3D) single-beam optical trapping of gold nanoparticles with diameters between 18 and 254 nm. Three-dimensional power spectral analysis reveals that, for nanoparticles with diameters less than 100 nm, the trap stiffness is proportional to the volume of the particle. For larger particles, the trap stiffness still increases with size, however, less steeply. Finally, we provide numbers for the largest forces exertable on gold nanoparticles.

Defined DNA/nanoparticle conjugates

Glutathione monolayer-protected gold clusters were reacted by place exchange with 19- or 20-residue thiolated oligonucleotides. The resulting DNA/nanoparticle conjugates could be separated on the basis of the number of bound oligonucleotides by gel electrophoresis and assembled with one another by DNA-DNA hybridization. This approach overcomes previous limitations of DNA/nanoparticle synthesis and yields conjugates that are precisely defined with respect to both gold and nucleic acid content.

Peptide-Based Nanotubes and Their Applications in Bionanotechnology

In nature, biological nanomaterials are synthesized under ambient conditions in a natural microscopic-sized laboratory, such as a cell. Biological molecules, such as peptides and proteins, undergo self-assembly processes in vivo and in vitro, and these monomers are assembled into various nanometer-scale structures at room temperature and atmospheric pressure. The self-assembled peptide nanostructures can be further organized to form nanowires, nanotubes, and nanoparticles via their molecular-recognition functions. The application of molecular self-assemblies of synthetic peptides as nanometer-scale building blocks in devices is robust, practical, and affordable due to their advantages of reproducibility, large-scale production ability, monodispersity, and simpler experimental methods. It is also beneficial that smart functionalities can be added at desired positions in peptide nanotubes through well-established chemical and peptide syntheses. These features of peptide-based nanotubes are the driving force for investigating and developing peptide nanotube assemblies for biological and non-biological applications.

Hierarchical self-assembly of a coiled-coil peptide into fractal structure

Here we report the hierarchical self-assembly of a cross-linkable coiled-coil peptide containing an internal cysteine. Atomic force microscopy (AFM) experiments revealed the fractal structure of the assemblies, and molecular simulations showed that the peptides cross-linked to form clusters of coiled-coils, which further assembled to form globules of tens of nanometers in diameter. Such hierarchical organization was modulated by pH or thiol-reducing agent. Exploitation of the fractal structures through chemical methods may be valuable for the fabrication of materials spanning multiple length scales.

Nanorobotics Control Design: A Collective Behavior Approach for Medicine

The authors present a new approach using genetic algorithms, neural networks, and nanorobotics concepts applied to the problem of control design for nanoassembly automation and its application in medicine. As a practical approach to validate the proposed design, we have elaborated and simulated a virtual environment focused on control automation for nanorobotics teams that exhibit collective behavior. This collective behavior is a suitable way to perform a large range of tasks and positional assembly manipulation in a complex three-dimensional workspace. We emphasize the application of such techniques as a feasible approach for the investigation of nanorobotics system design in nanomedicine. Theoretical and practical analyses of control modeling is one important aspect that will enable rapid development in the emerging field of nanotechnology.

Highly Efficient, Wavelength-Tunable, Gold Nanoparticle Based Optothermal Nanoconvertors

A photon-to-thermal energy conversion nanosystem based the near-infrared irradiation of one-dimensional gold nanoparticles (nanorods) is highly efficient and tunable to the incident wavelength. Using ambient photothermal detection, we observed a temperature rise of ca. 30 degrees C upon irradiating an aliquot of an aqueous nanoparticle suspension with a laser for 5 s. The temperature can be elevated even higher by embedding the particles into a poorly thermally conducting solid medium. The illuminated area of a sample containing nanorod particles embedded in a polyurethane matrix can be heated to >100 degrees C upon irradiation for 1 min. This optothermal conversion efficiency can be turned on selectively by tuning the wavelength to match that of the surface plasmon resonance of the particles. This specificity, with respect to the wavelength of the incident light, makes these highly efficient, particle-based, optothermal nanoconvertors suitable for potential use in multicolor detection on biochips and related sensors and as ideal contrasting agents for optoacoustic biomedical imaging applications.

Nanowiring of a redox enzyme by metallized peptides

A molecular assembly consisting of a redox enzyme, NADH peroxidase, a metallized double-helical peptide, and a gold nanoparticle immobilized onto a gold wire derivatized with a benzenedithiol compound, initiated and conducted redox signals in the presence of H(2)O(2) and NADH. The current generated by the binding of NADH, the electron donor, was transduced through the molecular assembly with apparently little loss of signal to the solution. The currents measured correlate to an electron transfer rate constant on the order of 3,000 s(-1) within each assembly. This electron transfer rate is two orders of magnitude higher than the endogenous electron transfer rate from NADH to the native enzyme, 27 s(-1). This rate indicates that the metallized peptide is in a conformation conducive for electron transfer and, in conjunction with the redox enzyme, can form effective conduits of electrical signals. This work demonstrates the feasibility of utilizing designed and highly efficient biomolecular assemblies for the production of ultra-sensitive, in-situ biosensors.

Thermal transport in au-core polymer-shell nanoparticles

Thermal transport in aqueous suspensions of Au-core polymer-shell nanoparticles is investigated by time-resolved measurements of optical absorption. The addition of an organic cosolvent to the suspension causes the polystyrene component of the polymer shell to swell, and this change in the microstructure of the shell increases the effective thermal conductivity of the shell by a factor of approximately 2. The corresponding time scale for the cooling of the nanoparticle decreases from 200 ps to approximately 100 ps. The threshold concentration of cosolvent that creates the changes in thermal conductivity, 5 vol % tetrahydrofuran in water or 40 vol % N,N-dimethylformamide in water, is identical to the threshold concentrations for producing small shifts in the frequency of the plasmon resonance. Because the maximum fraction of solvent in the polymer shell is less than 20 vol %, the increase in the effective thermal conductivity of the shell cannot be easily explained by contributions to heat transport by the solvent or enhanced alignment of the polystyrene backbone along the radial direction.

Labeling ribonuclease S with a 3 nm Au nanoparticle by two-step assembly

We label ribonuclease S with a 3 nm Au nanoparticle (NP) by utilizing its two-piece structure. One portion, S-peptide, is mutated with a unique NP attachment site. NP-peptide self-assembles with the other portion, S-protein, to form an active enzyme. NP mobility decreases with peptide labeling and S-protein association. Surface plasmon shifts support conjugation. Higher S-peptide coverages on the NP surface reduce nonspecific adsorption, while sterically hindering assembly of RNaseS. Thiols displace nonspecific adsorption, maximizing site-specific labeling.

What is nanomedicine?

The early genesis of the concept of nanomedicine sprang from the visionary idea that tiny nanorobots and related machines could be designed, manufactured, and introduced into the human body to perform cellular repairs at the molecular level. Nanomedicine today has branched out in hundreds of different directions, each of them embodying the key insight that the ability to structure materials and devices at the molecular scale can bring enormous immediate benefits in the research and practice of medicine.

Heat flow in proteins: Computation of thermal transport coefficients

The rate of vibrational energy transfer and thermal transport coefficients are computed for two structurally distinct proteins, green fluorescent protein (GFP) and myoglobin. The computation of thermal transport coefficients exploits the scaling of the energy diffusion coefficient with the vibrational mode frequency of a protein. Near 300 K we find that vibrational energy transfer due to anharmonicity contributes substantially to thermal transport because of the localization of many thermally accessible normal modes. The thermal diffusivity for the beta-barrel GFP is larger than that for myoglobin, particularly at low temperature due to a mean free path for vibrational energy propagation that is twice as large at low frequency. Vibrational energy transfer is also faster in GFP than in myoglobin for most vibrational modes.

The dynamic properties of an intramolecular transition from DNA duplex to cytosine-thymine motif triplex

We here report that the formation and breakdown of an intramolecular cytosine-thymine (CT) motif DNA triple-helix can be performed repeatedly, quickly and independently of its local concentration without performance reduction over successive cycles; as a consequence, we propose that this set of characteristics makes the DNA duplex-triplex transition an ideal candidate to power simple nanometer-scale devices capable of maintaining effective performance regardless of their local concentration.

Attachment of ferrocene nanotubes on beta-cyclodextrin self-assembled monolayers with molecular recognitions

Ferrocene nanotubes were fabricated by binding carboxylic acid-derivatized ferrocenes onto template peptide nanotubes via hydrogen bonding. When these ferrocene-functionalized nanotubes were incubated with beta-cyclodextrin (beta-CD) self-assembled monolayers (SAMs) coated on patterned Au substrates in solution, the ferrocene nanotubes recognized and attached onto the beta-CD SAMs via host-guest molecular recognition. The ferrocene nanotubes were also observed to recognize the certain cavity size of CD. The attachment/detachment of nanotubes on the beta-CD SAMs was controlled electrochemically by tuning the redox states of ferrocene nanotubes. This electric field-responsive building block may be applied to build nanometer-sized switching components in electronics and sensors.

Remote activation of capsules containing Ag nanoparticles and IR dye by laser light

We present a novel method for remote release of an encapsulated material from polyelectrolyte capsules based on laser light illumination. Two different components were introduced in the polyelectrolyte shells of PAH/PSS capsules-either Ag nanoparticles or IR dye-to induce absorption of light. Under laser illumination the capsules containing Ag nanoparticles or IR dye were deformed or cut, thus providing a venue for remote release of encapsulated materials. The experiments were conducted with a low-power near-infrared continuous-wave laser diode.

Synthesis of monofunctionalized gold nanoparticles by fmoc solid-phase reactions

In this communication, solid-phase reactions for the synthesis of Lys-monofunctionalized gold nanoparticles are described. A controlled and selective fabrication of linear nanoparticle arrays can be achieved through peptide linkage systems, and therefore it is essential to prepare Fmoc amino acid nanoparticle building blocks susceptible to Fmoc solid-phase peptide synthesis. Gold nanoparticles containing carboxylic acids (2) in the organic shell were covalently ligated to Lys on solid supports through amide bond coupling reactions. We employed Fmoc-Lys-substituted polymer resins such as Fmoc-Lys-Wang or Fmoc-Lys-HMPA-PEGA. The low density of Lys on the matrix enabled 2 nm-sized gold nanoparticles to react with Lys in a 1:1 ratio. Subsequent cleavage reactions using 60% TFA reagent resulted in Lys transfer from the solid matrix to gold nanoparticles, and the Fmoc-Lys-monofunctionalized gold nanoparticles (5) were obtained with 3-15% yield. Synthesis using HMPA-PEGA resin increased productivity due to the superior swelling properties of PEGA resin in DMF. Monofunctionalization of nanoparticles was microscopically characterized using TEM for the ethylenediamine-bridged nanoparticle dimers (6). By counting the number of 6, we found that at least 60% of cleaved nanoparticles were monofunctionalized by Lys. This method is highly selective and efficient for the preparation of monofunctionalized nanoparticles.

Electrochemical Coding of Single-Nucleotide Polymorphisms By Monobase-Modified Gold Nanoparticles

Rapidly increasing information about the human genome requires a fast and simple method for the detection of single-nucleotide polymorphisms (SNPs). To date, the conventional SNP detection technologies have been unable to identify all possible SNPs and needed further development in cost, speed, and sensitivity. Here we describe a novel method to discriminate and code all possible combinations. SNPs were coded by monitoring the changes in the electrochemical signal of the monobase-modified colloidal gold (Au) nanoparticles. First, a chitosan layer was formed on the alkanethiol self-assembled monolayer-modified Au nanoparticle. The monobases were then attached onto the chitosan-coated Au nanoparticles through their 5' phosphate group via the formation of a phosphoramidate bond with the free amino groups of chitosan. The size of the surface-modified Au nanoparticle was found to be 8.46 +/- 1.53 nm by using atomic force microscopy. If there is a SNP in DNA and the mismatched bases are complementary to the monobase, Au nanoparticles accumulate on the electrode surface in the presence of DNA polymerase I (Klenow fragment), thus resulting in a significant change in the Au oxide wave. In this report, monobase-modified Au nanoparticles show not only the presence of a SNP, but also identify which bases are involved within the pair. Especially, the identification of a transversion SNP, which contains a couple of the same pyrimidine or purine bases, is greatly simplified. A model study was performed by using a synthetic 21-base DNA probe related to tumor necrosis factor (TNF-alpha) along with its all possible mutant combinations. This versatile nanoparticle-based electrochemical protocol is a promising candidate for coding all mutational changes.

New technologies for nutrition research

The Experimental Biology 2003 symposium entitled "New Technologies for Nutrition Research" was organized to highlight new and emerging technologies, including nanotechnology and proteomics, and to suggest ways for their integration into nutrition research. Speakers focused on topics that included accelerator mass spectrometry for ultra-low level radiolabel tracing, nanodevices for real-time optical intracellular sensing, mass spectrometric techniques for examining protein expression, as well as potential applications for nanotechnology in the food sciences. These technologies may be particularly useful in obtaining accurate spatial information and low-level detection of essential and nonessential bioactive food components (nutrients) and their metabolites, and in enhancing the understanding of the impact of nutrient/metabolite and biomolecular interactions. Highlights from this symposium are presented briefly herein.

Metal nanoparticles as labels for heterogeneous, chip-based DNA detection

The last decade has witnessed the development of a variety of metal nanoparticle-based techniques for DNA detection. High sensitivity and specificity, miniaturization, and cost-efficient detection are problems addressed by the use of nanoparticle labels in heterogeneous DNA detection schemes. The small label size, established bioconjugation chemistry, and the unusual optical and electrical properties of metal nanoparticles make them unique tools for DNA detection. This paper reviews the different physical characteristics of metal nanoparticles and their implementation in assays. It covers various optical as well as gravimetric, electrochemical and electrical methods for analysing nanoparticle-labelled analytes, and particularly DNA, at sensing surfaces.

Small-scale systems for in vivo drug delivery

Recent developments in the application of micro- and nanosystems for drug administration include a diverse range of new materials and methods. New approaches include the on-demand activation of molecular interactions, novel diffusion-controlled delivery devices, nanostructured 'smart' surfaces and materials, and prospects for coupling drug delivery to sensors and implants. Micro- and nanotechnologies are enabling the design of novel methods such as radio-frequency addressing of individual molecules or the suppression of immune response to a release device. Current challenges include the need to balance the small scale of the devices with the quantities of drugs that are clinically necessary, the requirement for more stable sensor platforms, and the development of methods to evaluate these new materials and devices for safety and efficacy.

Fabrication of novel biomaterials through molecular self-assembly

Two complementary strategies can be used in the fabrication of molecular biomaterials. In the 'top-down' approach, biomaterials are generated by stripping down a complex entity into its component parts (for example, paring a virus particle down to its capsid to form a viral cage). This contrasts with the 'bottom-up' approach, in which materials are assembled molecule by molecule (and in some cases even atom by atom) to produce novel supramolecular architectures. The latter approach is likely to become an integral part of nanomaterials manufacture and requires a deep understanding of individual molecular building blocks and their structures, assembly properties and dynamic behaviors. Two key elements in molecular fabrication are chemical complementarity and structural compatibility, both of which confer the weak and noncovalent interactions that bind building blocks together during self-assembly. Using natural processes as a guide, substantial advances have been achieved at the interface of nanomaterials and biology, including the fabrication of nanofiber materials for three-dimensional cell culture and tissue engineering, the assembly of peptide or protein nanotubes and helical ribbons, the creation of living microlenses, the synthesis of metal nanowires on DNA templates, the fabrication of peptide, protein and lipid scaffolds, the assembly of electronic materials by bacterial phage selection, and the use of radiofrequency to regulate molecular behaviors.

Application of host-guest chemistry in nanotube-based device fabrication: photochemically controlled immobilization of azobenzene nanotubes on patterned alpha-CD monolayer/Au substrates via molecular recognition

Azobenzene-functionalized nanotubes recognized and attached onto well-defined complementary regions of thiolated alpha-CD SAM/Au substrates via host-guest molecular recognition. The binding between the azobenzene nanotubes and the alpha-CD SAM/Au substrates was controlled by UV irradiation. The light-induced attachment-detachment of the azobenzene nanotubes on the alpha-CD SAMs was reversible. Some of the nanotubes were capable of interconnecting two Au substrates. This smart building block may be applied to build photoactive nanometer-sized mechanical switches in electronics.

Optical properties and ultrafast dynamics of metallic nanocrystals

Noble metal particles have long fascinated scientists because of their intense color, which led to their application in stained glass windows as early as the Middle Ages. The recent resurrection of colloidal and cluster chemistry has brought about the strive for new materials that allow a bottoms-up approach of building improved and new devices with nanoparticles or artificial atoms. In this review, we discuss some of the properties of individual and some assembled metallic nanoparticles with a focus on their interaction with cw and pulsed laser light of different energies. The potential application of the plasmon resonance as sensors is discussed.

Au nanowire fabrication from sequenced histidine-rich peptide

A new biological approach to fabricate Au nanowires was examined by using sequenced histidine-rich peptide nanowires as templates. The sequenced histidine-rich peptide molecules were assembled as nanowires, and the biological recognition of the sequenced peptide toward Au lead to efficient Au coating on the nanowires. Monodisperse Au nanocrystals were uniformly coated on the histidine peptide nanowires with the high-density coverage, and the crystalline phases of the Au nanocrystals were observed as (111) and (220). The uniformity of the Au coating on the nanowires without contamination of precipitated Au aggregates is advantageous for the fabrication of electronics and sensor devices when the nanowires are used as the building blocks. We believe this simple metal nanowire fabrication method can be applied to various metals and semiconductors with peptides whose sequences are known to mineralize specific ions.

Synthesis of ODNs containing 4-methylamino-1,8-naphthalimide as a fluorescence probe in DNA

Synthesis and fluorescence properties of oligodeoxynucleotides containing 4-methylamino-1,8-naphthalimide (NI) have been described. NI was successfully incorporated into DNA without significant destabilization of DNA whilst retaining its high fluorescence quantum yield. The attachment site of the NI greatly affected its property as an energy acceptor in FRET analysis.

Nanostructures as tailored biological probes

A new generation of spectroscopic dyes is gradually becoming available to biological researchers, from an unexpected source: materials chemists who study the synthesis and properties of nano-sized inorganic objects. Research into tailoring the optical properties, surface chemistry and biocompatibility of metallic and semiconductor nanoparticles, exemplified in part by a recent report by Mirkin, Schatz and coworkers, is fulfilling the promise of these nanostructures as customizable substitutes for organic molecular probes.

Stem-loop oligonucleotides: a robust tool for molecular biology and biotechnology

The specific structural features of stem-loop (hairpin) DNA constructs provide increased specificity of target recognition. Recently, several robust assays have been developed that exploit the potential of structurally constrained oligonucleotides to hybridize with their cognate targets. Here, I review new diagnostic approaches based on the formation of stem-loop DNA oligonucleotides: molecular beacon methodology, suppression PCR approaches and the use of hairpin probes in DNA microarrays. The advantages of these techniques over existing ones for sequence-specific DNA detection, amplification and manipulation are discussed.