Encapsidation of nanoparticles by red clover necrotic mosaic virus

Icosahedral virus capsids demonstrate a high degree of selectivity in packaging cognate nucleic acid genome components during virion assembly. The 36 nm icosahedral plant virus Red clover necrotic mosaic virus (RCNMV) packages its two genomic ssRNAs via a specific capsid protein (CP) genomic RNA interaction. A 20-nucleotide hairpin structure within the genomic RNA-2 hybridizes with RNA-1 to form a bimolecular complex, which is the origin of assembly (OAS) in RCNMV that selectively recruits and orients CP subunits initiating virion assembly. In this Article, an oligonucleotide mimic of the OAS sequence was attached to Au, CoFe2O4, and CdSe nanoparticles ranging from 3 to 15 nm, followed by addition of RNA-1 to form a synthetic OAS to direct the virion-like assembly by RCNMV CP. Dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements were consistent with the formation of virus-like particles (VLPs) comparable in size to native RCNMV. Attempts to encapsidate nanoparticles with diameters larger than 17 nm did not result in well-formed viral capsids. These results are consistent with the presence of a 17 nm cavity in native RCNMV. Covalent linkage of the OAS to nanoparticles directs RNA-dependent encapsidation and demonstrates that foreign cargo can be packaged into RCNMV virions. The flexibility of the RCNMV CP to encapsidate different materials, as long as it is within encapsidation constraint, is a critical factor to be considered as a drug delivery and diagnostic vehicle in biomedical applications.     

Controlled side-by-side assembly of gold nanorods and dye molecules into polymer-wrapped SERRS-active clusters

The controlled side-by-side assembly of gold nanorods in solution together with Raman reporter dye molecules to create small SERRS-active clusters stabilised by a surrounding polymer layer is demonstrated. This promising new class of nanotags offers several advantages over spherical nanoparticles for bioimaging and is of potential importance for a wide range of plasmon-enhanced spectroscopies and can also serve as building blocks for more complex solution-phase nanostructures.     

Extraction mechanisms of charged organic dye molecules into silica-surfactant nanochannels in a porous alumina membrane

Extraction mechanisms of charged organic dye molecules are examined for an assembly of silica-surfactant nanochannels with a channel diameter of 3.4 nm, which is formed inside the pores of an anodic alumina membrane by a surfactant-template method. Experimental results confirm that the extraction mechanism depends on the sign of a charge of the dye molecules. The extraction of the cationic rhodamine 6G is predominantly caused by an ion-pair extraction process, whereas an anion-exchange process is mainly responsible for the extraction of the anionic sulforhodamine B. These extraction mechanisms are discussed by considering the microstructures of the silica-surfactant nanochannels.     

Sublimation enthalpy of dye molecules measured using fluorescence

We present an in-flight fluorescence detection scheme for molecular beams which is applied to determine the enthalpy of sublimation of dye molecules. We investigate tetraphenylporphyrin (TPP), porphine, and nile red, which are believed to be suitable candidates for molecular de Broglie wave interferometry. The measured values are H(sub)(TPP)=142+/-3 kJ/mol, H(sub)(porphine)=87+/-3 kJ/mol, and H(sub)(nile red)=66+/-2 kJ/mol. For TPP, sublimation enthalpies differ in the literature by more than a factor of 2. Our measurements confirm a value at the lower end of this scale. We discuss changes in the character of the molecular flow with the source temperature as a prime reason for discrepancies in the published data.     

Structuring of tricarbocyanine dye molecules in Langmuir-Blodgett films

The problems of formation of stable Langmuir monolayers containingN-sulfopropyl substituted thiatricarbocyanine dyes are considered: the effects of the composition of the mixture applied on the surface of an aqueous subphase and of the extent of compression of the monolayer on processes of ordering of molecular structure. Dyes are introduced into complex monolayers at the water-air interface and then are transferred on solid substrates as multilayered Langmuir-Blodgett (LB) films. For the first time the formation of J-aggregates has been observed for two tricarbocyanine dyes. The structure of J-aggregates depends on the composition of the mixture and the value of the constant pressure at which the transfer occurs. LB films of J-aggregated dyes are optically anisotropic, which is related to the fact that they are formed in the monolayer on the surface and there is no interlayer aggregation during the transfer to substrates. Heterodimers are formed in complex monolayers containing oppositely charged ions of dyes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1278–1283, July, 1995.The work was partially financially supported by the Foundation for Basic Research of the State Committee on Science and Technologies of the Ukraine (Project No. 2.2/48 Normal').     

Characterization of silica-coated tobacco mosaic virus

The deposition of silica on the surface of tobacco mosaic virus (TMV) is achieved at a higher pH (>7) as a means to enhance its usefulness as a template for the synthesis of nanostructures. Electron energy loss spectroscopy definitively shows the presence of a silica shell on the surface of the TMV while small angle X-ray scattering differentiates successfully between silica-coated TMV and silica particles in the presence of uncoated TMV. Importantly, coating reactions done in a 50% w/v methanol/water solution produce smaller silica nanostructures during the condensation of the hydrolysis intermediates, possibly aiding in obtaining uniform coating. Furthermore, TMV-templated silica coatings are found to enhance the stability of the virus particle in methanol at conditions that would ordinarily disrupt the assembled particle. Combined these findings demonstrate that TMV can function as an efficient template for the controlled deposition of silica at neutral pH.     

Order parameters of dye molecules in lyotropic nematic mesophases

The alignment in a magnetic field of two similar azo dyes in binary nematic lyotropic phases (C₇F₁₅CO₂NH₄ and C₈F₁₇CO₂NH₄ in D₂O) has been studied. The order 5 parameter for the dyes was determined by measuring quadrupolar splittings (deuterium N.M.R.), the anisotropy of the electric conductivity and dichroism. The order parameter of the dye fixed in the disc-like perfluoro micelle with positive diamagnetic anisotropy was determined as a function of magnetic field strength, surfactant concentration, temperature and chain length. In addition the time constants for orientation and disorientation were determined.     

The Stokes-shifted fluorescence risetime of dye molecules in solution

We have measured the rise of Stokes-shifted spontaneous fluorescence intensity during a 10 ps 530 nm actinic light pulse for rhodamine B, rhodamine 6G and erythrosin B dissolved in water, ethanol and methanol. The best numerical fit to our data corresponds to a time delay of less than 1 ps between excitation and fluorescence emission.     

The optical properties of triphenylmethane dye molecules and chromogens

Industrial dye monomers, including malachite green, crystal violet, brilliant green, and methyl violet, were isolated by extraction with the use of heptane. UV light absorption bands characteristic of pure molecules were determined. The molecules of the dyes studied, which were ion pairs (formed by dye cations and oxalate or chlorine anions), did not absorb light in the visible range; that is, they were not chromogens. The conclusion was drawn that chromogen particles responsible for chromaticity were supramolecular dimers of nonchromogenic triphenylmethane series molecules. This conclusion was substantiated by trends in spectral transformations with the participation of immonium hydroxides obtained from dyes and side products of the synthesis of industrial dyes with quinoid molecular structures.     

Assembly of tobacco mosaic virus into fibrous and macroscopic bundled arrays mediated by surface aniline polymerization

One-dimensional (1D) polyaniline/tobacco mosaic virus (TMV) composite nanofibers and macroscopic bundles of such fibers were generated via a self-assembly process of TMV assisted by in-situ polymerization of polyaniline on the surface of TMV. At near-neutral reaction pH, branched polyaniline formed on the surface of TMV preventing lateral association. Therefore, long 1D nanofibers were observed with high aspect ratios and excellent processibility. At a lower pH, transmission electron microscopy (TEM) analysis revealed that initially long nanofibers were formed which resulted in bundled structures upon long-time reaction, presumably mediated by the hydrophobic interaction because of the polyaniline on the surface of TMV. In-situ time-resolved small-angle X-ray scattering study of TMV at different reaction conditions supported this mechanism. This novel strategy to assemble TMV into 1D and 3D supramolecular composites could be utilized in the fabrication of advanced materials for potential applications including electronics, optics, sensing, and biomedical engineering.     

Dual-surface modification of the tobacco mosaic virus

The protein shell of the tobacco mosaic virus (TMV) provides a robust and practical tubelike scaffold for the preparation of nanoscale materials. To expand the range of applications for which the capsid can be used, two synthetic strategies have been developed for the attachment of new functionality to either the exterior or the interior surface of the virus. The first of these is accomplished using a highly efficient diazonium coupling/oxime formation sequence, which installs >2000 copies of a material component on the capsid exterior. Alternatively, the inner cavity of the tube can be modified by attaching amines to glutamic acid side chains through a carbodiimide coupling reaction. Both of these reactions have been demonstrated for a series of substrates, including biotin, chromophores, and crown ethers. Through the attachment of PEG polymers to the capsid exterior, organic-soluble TMV rods have been prepared. Finally, the orthogonality of these reactions has been demonstrated by installing different functional groups on the exterior and interior surfaces of the same capsid assemblies.     

Direct observation of vibrational relaxation of dye molecules in solution

The characteristic time for vibrational relaxation in an optically excited molecular electronic state has been measured with picosecond resolution for the molecules rhodamine B and rhodamine 6G in solution using a new experimental technique.     

Diffusion properties of dye molecules in nanoporous TiO2 networks

The adsorption of ruthenium-dye molecules out of ethanol solution onto TiO2 particles of nanoporous TiO2 films was used to study the molecules' diffusion through these layers by means of optical absorption spectrometry. Dependent on pore size, porosity, and particle size, effective diffusion constants as low as D(eff) = 4 x 10(-9) cm2/s were deduced from the uptake curves by applying a simple model for combined diffusion and adsorption. These diffusion constants for diffusion through the nanoporous network are up to 3 orders of magnitude lower than in bulk ethanol and are discussed with respect to the properties of the nanoporous material.     

Strength of interactions between immobilized dye molecules and sol-gel matrices

In this paper we present a new theory to re-examine the immobilization technique of dye doped sol-gel films, define the strength and types of possible bonds between the immobilized molecule and sol-gel glass, and show that the immobilized molecule is not free inside the pores as was previously thought. Immobilizing three different pH sensitive dyes with different size and functional groups inside the same sol-gel films revealed important information about the nature of the interaction between the doped molecule and the sol-gel matrix. The samples were characterized by means of ultraviolet-visible spectrophotometer (UV-VIS), thermal gravimetric analysis (TGA), mercury porosimetry (MP), nuclear magnetic resonance spectroscopy ((29)Si NMR) and field-emission environmental scanning electron microscopy (ESEM-FEG). It was found that the doped molecule itself has a great effect on the strength and types of the bonds. A number of factors were identified, such as number and types of the functional groups, overall charge, size, pK(a) and number of the silanol groups which surround the immobilized molecule. These results were confirmed by the successful immobilization of bromocresol green (BCG) after a completely polymerized sol-gel was made. The sol-gel consisted of 50% tetraethoxysilane (TEOS) and 50% methyltriethoxysilane (MTEOS) (w/w). Moreover, the effect of the immobilized molecule on the structure of the sol-gel was studied by means of a leaky waveguide (LW) mode for doped films made before and after polymerization of the sol-gel.     

水溶性杯芳烃对染料客体分子的包结配位作用

研究了水溶性的杯[n]芳烃磺酸盐(n=4,6,8)及杯[6]芳烃磺酸盐的烷基化衍生物在25.0℃对几种染料客体分子的包结配位作用,发现杯[n]芳烃磺酸盐均使客体的荧光强度降低,而在其下缘的烷基化衍生物却使客体的荧光强度增强,从光物理行为对这些结果进行了解释。由荧光光谱分光光度滴定技术确定了25.0℃时所形成配合物的稳定常数,讨论了其分子识别性质。     

Femtosecond dephasing studies of dye molecules in a polymer host

A femtosecond three-pulse scattering technique is used to observe dephasing of the lowest electronic transition of cresyl violet in poly-methyl methacrylate. The transition from inhomogeneous to homogeneous broadening is studied as temperature is increased front 15 to 290 K.     

Coagulation of tobacco mosaic virus in alcohol-water-LiCl solutions

The coagulation and colloidal stability of tobacco mosaic virus (TMV) in alcohol-water-LiCl solutions were studied. Without the addition of LiCl salt, the coagulation was promoted by the increase of hydrophobicity of the alcohols that is proportional to their alkyl chain length and concentration. Addition of the LiCl salt reduced the electrostatic repulsion between TMV particles resulting in coagulation in methanol-water and ethanol-water solutions. In water-alcohol-LiCl mixture, the coagulation of TMV was driven by both the hydrophobic interaction of the solution and the screening effect of the salt simultaneously. To understand the particle-particle interaction during the coagulation, the interaction energy was calculated using DLVO theory. Considering the electrostatic repulsive energy, van der Waals attractive energy, and hydrophobic interaction energy, the total energy profiles were obtained. The experiment and model calculation results indicated that the increase of alcohol concentration would increase hydrophobic attraction energy so that the coagulation is promoted. These results provide the fundamental understanding on the coagulation of biomolecular macromolecules.