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At least 793 records · Page 44Linked to original sources
PubMed2002

Sorting fluorescent nanocrystals with DNA.

Semiconductor nanocrystals with narrow and tunable fluorescence are covalently linked to oligonucleotides. These biocompounds retain the properties of both nanocrystals and DNA. Therefore, different sequences of DNA can be coded with nanocrystals and still preserve their ability to hybridize to their complements. We report the case where four different sequences of DNA are linked to four nanocrystal samples having different colors of emission in the range of 530-640 nm. When the DNA-nanocrystal conjugates are mixed together, it is possible to sort each type of nanoparticle by using hybridization on a defined micrometer-size surface containing the complementary oligonucleotide. Detection of sorting requires only a single excitation source and an epifluorescence microscope. The possibility of directing fluorescent nanocrystals toward specific biological targets and detecting them, combined with their superior photostability compared to organic dyes, opens the way to improved biolabeling experiments, such as gene mapping on a nanometer scale or multicolor microarray analysis.

DNA↗
PubMed2002

Individual water-soluble dendrimer-encapsulated silver nanodot fluorescence.

Easily observed on the single molecule level, highly fluorescent and photostable silver nanoclusters have been photochemically prepared within poly(amidoamine) dendrimer hosts in aqueous solutions. The dendrimer cage stabilizes and solubilizes the nanoclusters to yield highly stable, photoactivated single nanodots ranging in size from 2 to 8 silver atoms. These multicolored, highly fluorescent species are extremely photostable and readily observed on the single molecule scale with weak mercury lamp excitation. Such easily created, bright, photoactivated water-soluble fluorophores are likely to greatly expand the impact of single molecule labeling studies in a wide variety of systems.

Fluorescent Dyes↗
PubMed2003

Bright phosphorescence of a trinuclear copper(I) complex: luminescence thermochromism, solvatochromism, and "concentration luminochromism".

A photophysical study is reported for the trinuclear copper(I) complex {[3,5-(CF3)2Pz]Cu}3. The neutral compound exhibits multicolor bright phosphorescent emissions both in the solid state and in solution. The emission can be tuned to multiple visible colors by controlling the temperature, solvent, and {[3,5-(CF3)2Pz]Cu}3 concentration, giving rise to luminescence thermochromism, luminescence solvatochromism, and a new optical phenomenon called "concentration luminochromism", respectively.

Journal Article↗
PubMed2004

Near-complete suppression of quantum dot blinking in ambient conditions.

Colloidal semiconductor quantum dots are attractive fluorophores for multicolor imaging because of broad absorption and narrow emission spectra, and they are brighter and far more photostable than organic dyes. However, severe intermittence in emission (also known as blinking) has been universally observed from single dots and has been considered an intrinsic limitation difficult to overcome. This is unfortunate because growing applications in spectroscopy of single biological molecules and quantum information processing using single photon sources could greatly benefit from long-lasting and nonblinking single-molecule emitters. For instance, in a recent application of single-dot imaging, the tracking of membrane receptors was interrupted frequently due to the stroboscopic nature of recording. Blinking can also reduce the brightness in ensemble imaging via signal saturation. Here we show that the quantum dot blinking can be suppressed with the emission duty cycle approaching 100% while maintaining biocompatibility.

Biocompatible Materials↗
PubMed2005

Fluorescent profiling of natural product producers.

The identification of natural product producer organisms remains a problem for both isolation and natural product classification. A concise screen is developed through fluorescent modification of a set of natural products that offer a common activity. Through real-time multicolor microscopy, the processing, storage, and effects of a natural product are rapidly screened at the level of the strain and individual organism.

Animals↗
PubMed2005

Single molecular multianalyte (Ca2+, Mg2+) fluorescent probe and applications to bioimaging.

Intracellular signal transduction relies on spatial and temporal signal transmitter dynamics. To clarify the correlations of these transmitter molecules, multicolor-imaging has been widely used. However, in the case of applying multiple indicators in a cell, spectral overlap of the indicators prevents accurate quantitative analysis. Moreover, the invasive (toxic) effect, the localization, the metabolism, as well as photobleaching of these indicators complicate the situation. Here, we show that single-molecular multifluorescent probes can overcome these problems. While intracellular calcium plays a critical role as a signal transmitter and magnesium acts as a cofactor in many situations, the correlations between the two cations are now the main issue. We designed and synthesized a Ca2+-Mg2+ responsive multifluorescent probe, KCM-1. KCM-1 shows a spectral blue shift upon complexation to Ca2+ and a red shift to the presence of Mg2+. With data analyzed at different excitation wavelengths, the concentrations of Ca2+ and Mg2+ are simultaneously quantified. Furthermore, by using the AM-ester method, intracellular Ca2+ and Mg2+ concentrations are simultaneously imaged. Such a type of intracellular multiple analyte imaging by a single-molecular multifluorescent probe is successfully demonstrated for the first time.

Calcium↗
PubMed2006

Specific and stable fluorescence labeling of histidine-tagged proteins for dissecting multi-protein complex formation.

Labeling of proteins with fluorescent dyes offers powerful means for monitoring protein interactions in vitro and in live cells. Only a few techniques for noncovalent fluorescence labeling with well-defined localization of the attached dye are currently available. Here, we present an efficient method for site-specific and stable noncovalent fluorescence labeling of histidine-tagged proteins. Different fluorophores were conjugated to a chemical recognition unit bearing three NTA moieties (tris-NTA). In contrast to the transient binding of conventional mono-NTA, the multivalent interaction of tris-NTA conjugated fluorophores with oligohistidine-tagged proteins resulted in complex lifetimes of more than an hour. The high selectivity of tris-NTA toward cumulated histidines enabled selective labeling of proteins in cell lysates and on the surface of live cells. Fluorescence labeling by tris-NTA conjugates was applied for the analysis of a ternary protein complex in solution and on surfaces. Formation of the complex and its stoichiometry was studied by analytical size exclusion chromatography and fluorescence quenching. The individual interactions were dissected on solid supports by using simultaneous mass-sensitive and multicolor fluorescence detection. Using these techniques, formation of a 1:1:1 stoichiometry by independent interactions of the receptor subunits with the ligand was shown. The incorporation of transition metal ions into the labeled proteins upon labeling with tris-NTA fluorophore conjugates provided an additional sensitive spectroscopic reporter for detecting and monitoring protein-protein interactions in real time. A broad application of these fluorescence conjugates for protein interaction analysis can be envisaged.

Chelating Agents↗
PubMed2006

Planar gold nanoparticle clusters as microscale mirrors.

Dispersible microscale mirror particles were synthesized by linkage of citrate-coated gold nanoparticles and 3-aminopropylsilyl-modified Ca2Nb3O10 perovskite nanoplates. The mirror particles reflect 14-19% of light in the 500-800 nm wavelength interval with retention of polarization. Due to their directional reflection properties, laser-irradiated micromirror dispersions in solvents exhibit Brownian motion-driven multicolor blinking behavior.

Journal Article↗
PubMed2025

Live-Cell Monitoring and Omics Analysis of Liquid-Solid Transitions of Biomolecular Condensates.

Biomolecular condensates, or so-called membraneless organelles, transition from liquid into more solid-like states over time, contributing to the development of pathological conditions. The present study proposes a simple method using photoactive yellow protein (PYP) and its specific fluorescent covalent ligands to distinguish between the liquid and solid states of protein condensates in live cells. The method, compatible with fluorescence-activated cell sorting (FACS), correlates the stiffness of specific protein condensates with their accessibility to PYP ligands, enabling quantitative multicolor monitoring of condensate solidification. We applied this technique to 12 phase-separating proteins and their mutants, finding that TDP-43, particularly its A315T mutant linked to familial amyotrophic lateral sclerosis, most readily forms solid aggregates. Furthermore, this FACS-compatible strategy enabled the isolation of distinct cell populations based on condensate states, allowing for subsequent proteomic and transcriptomic analyses. Our findings demonstrate that condensate solidification is accompanied by the upregulated expression of extracellular matrix proteins, suggesting a previously unrecognized link between solid aggregate formation and extracellular matrix hardening.

Humans↗
PubMed2005

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.

Journal Article↗
PubMed2005

Chemiluminescence of CdTe nanocrystals induced by direct chemical oxidation and its size-dependent and surfactant-sensitized effect.

CdTe nanocrystals (NCs) capped with thioglycolic acid (TGA) were synthesized via a microwave-assisted method. The chemiluminescence (CL) of CdTe NCs induced by directly chemical oxidation and its size-depended and surfactant-sensitized effect in aqueous solution were then investigated. It was found that oxidants, especially hydrogen peroxide and potassium permanganate, could directly oxidize CdTe NCs to produce strong CL emission in basic conditions. The oxidized CL of CdTe NCs displayed size-dependent effect and its intensity increased along with increasing the sizes of the NCs. Moreover, the CL intensity could, if surfactants CTAB or beta-cyclodextrin were added to the above CL system, be sensitized to some degree. The sensitized CL induced by CTAB and beta-cyclodextrin is mainly contributing to the formation of aggregate nanostructure and the micellar micronanoenvironment, respectively. The possible oxidized CL mechanisms were further examined by means of photoluminescence spectra, CL spectra, and transmission electron microscopy studies. The CL properties of CdTe NCs not only will be helpful to study physical chemistry properties of semiconductor nanocrystals but also are expected to find use in many fields such as luminescence devices, bioanalysis, and multicolor labeling probes.

Journal Article↗
PubMed2004

Heterogeneous molecular distribution in supported multicomponent lipid bilayers.

Membrane domains contribute important structural and functional attributes to biological membranes. We describe the heterogeneous nanoscale distribution of lipid molecules within microscale membrane domains in multicomponent lipid bilayers composed of dipalmitoylphosphatidylcholine (DPPC), dilauroylphosphatidylcholine (DLPC), and cholesterol (chol). The lipids were labeled with the fluorescent lipid analogues Bodipy-PC and DiI-C20:0 to identify the distribution of individual membrane components. We used a near-field scanning optical microscope (NSOM) at room temperature to identify the nanoscale structures in the membrane. Simultaneous multicolor NSOM imaging at the emission maxima of the fluorescent analogues revealed a patchy distribution of Bodipy-PC and DiI-C20:0 indicative of phase separations in the bilayer. In a cholesterol-free system (DPPC/DLPC = 1:1), NSOM images proved that the two phosphatidylcholine molecules can coexist in domains at the micrometer level but form nanoscopic patches within the domains; DPPC occurs at the edge of the domains, whereas DLPC is present throughout the domains. In the presence of cholesterol (DPPC/DLPC = 7:3, chol = 18.9%), the two lipid molecules were more miscible but incomplete phase separations also occurred. The average domain sizes were 140-200 nm, well below the resolution capabilities of diffraction-limited light microscopy techniques; the domains were unresolvable by confocal microscopy. Our high-resolution NSOM studies of membrane domain behavior provide a better understanding of complex membrane phase phenomena in multicomponent biological membranes.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2004

Inkjet printing of well-defined polymer dots and arrays.

Inkjet printing represents a highly promising polymer deposition method, which is used for, for example, the fabrication of multicolor polyLED displays and polymer-based electronics parts. The challenge is to print well-defined polymer structures from dilute solution. We have eliminated the formation of ring stains by printing nonvolatile acetophenone-based inks on a perfluorinated substrate using different polymers. (De)pinning of the contact line of the printed droplet, as related to the choice of solvent, is identified as the key factor that determines the shape of the deposit, whereas the choice of polymer is of minor importance. Adding 10 wt % or more of acetophenone to a volatile solvent (ethyl acetate)-based polymer solution changes the shape of the deposit from ring-like to dot-like, which may be due to the establishment of a solvent composition gradient. Arrays of closely spaced dots have also been printed. The size of the dots is considerably smaller than the nozzle diameter. This may prove a potential strategy for the inkjet printing of submicrometer structures.

Journal Article↗
PubMed2003

Practical synthetic route to functionalized rhodamine dyes.

[reaction: see text] An efficient method for the synthesis of functionalized rhodamine derivatives has been developed. Multigram quantities of these water-soluble fluorophores can be prepared from inexpensive precursors and purified without the use of chromatography. A series of protein-reactive functional groups has been installed through subsequent reactions, providing materials for biomolecule modification. For multicolor applications, a solid-phase purification strategy has been developed to afford rhodamine derivatives possessing a wide range of spectral properties.

Journal Article↗
PubMed1997

Visual verification of close disposition between a rice A genome-specific DNA sequence (TrsA) and the telomere sequence.

A rice A genome-specific tandem repeat sequence (TrsA) and telomeric nucleotide sequences, (TTTAGGG)n, were simultaneously detected by multicolor fluorescence in situ hybridization (McFISH) using rice prometaphase chromosomes. Six pairs of TrsA sites visualized by fluorescence signals were all localized on the long arms close to the telomeric regions. Differences in the copy number of TrsA at the different sites were visualized both by the size of the telomeric condensation block stained with Giemsa solution and the signal intensity after FISH with TrsA. McFISH analyses using interphase nuclei could resolve close disposition of TrsA and telomere and also gave rough estimation of the distance between them. The functional significance of the close disposition of TrsA and telomere is discussed.

Chromosome Mapping↗
PubMed2001

Classical and molecular cytogenetics of the zebrafish, Danio rerio (Cyprinidae, Cypriniformes): an overview.

The zebrafish, Danio rerio, has recently become the model system for the genetic analysis of vertebrate development. This paper reviews the advances in zebrafish cytogenetics, obtained through classical and molecular techniques, which will lead to the assignment of specific linkage groups to specific chromosome pairs in the zebrafish genome project. Several chromosome pairs of the 50-chromosome karyotype of D. rerio were differentially stained by classical staining techniques and additional information has been obtained by molecular cytogenetics. Indeed, the analysis of constitutive heterochromatin by C-banding and base-specific fluorochrome staining had suggested a differential composition of peri- and paracentromeric constitutive heterochromatin. The chromosome mapping of distinct AT- and GC-rich zebrafish satellite DNAs by means of PRINS (Primed in situ) and multicolor FISH (Fluorescence in situ Hybridization) has confirmed this hypothesis, which therefore provided the chromosome localization of 10% of the zebrafish genome. The analysis of nucleolus organizer regions (NORs) by silver staining and by FISH with 18S rDNA has also revealed the existence of variable and inactive NORs, in addition to those on the terminal regions of the long arms of the three NOR-bearing chromosome pairs. Other multicopy genes, such as minor ribosomal genes, or multicopy repeats, such as telomere specific sequences, have now been mapped on zebrafish chromosomes. The latest advancement in zebrafish molecular cytogenetics is the chromosome mapping of single locus genes. Single-copy genes from each of the 25 genetic linkage groups are now being mapped on zebrafish chromosomes by using PAC clones.

Animals↗
PubMed1999

Preimplantation genetic diagnosis of aneuploidy: were we looking at the wrong chromosomes?

PURPOSE: Our purpose was to study aneuploidy frequencies of chromosomes 1, 4, 6, 7, 14, 15, 17, 18, and 22 in cleavage-stage embryos. These frequencies were compared to spontaneous abortion data to determine differences in survival rate of their aneuploidies. METHODS: One hundred ninety-four embryos were analyzed with multicolor fluorescence in situ hybridization. Embryos were divided into three maternal age groups: 20 to 34.9 years, (2) 35 to 39.9 years, and (3) 40 years and older. Embryos were also divided into two developmental and morphological groups; arrested and nonarrested embryos. RESULTS: The rate of aneuploidy was 14.51%, 14.10%, and 31.48% for age groups 1, 2, and 3, respectively (P < 0.005). The chromosomes most frequently involved in aneuploidy events were 22, 15, 1, and 17. CONCLUSIONS: The chromosomes most involved in spontaneous abortions are not necessarily the ones causing a decrease in implantation rates with maternal age. Other aneuploidies, such as for chromosomes 1 and 17, may seldom implant or die shortly after implantation.

Adult↗
PubMed1999

Advantages of day 4 embryo transfer in patients undergoing preimplantation genetic diagnosis of aneuploidy.

PURPOSE: Following preimplantation genetic diagnosis of aneuploidy, embryo transfer was executed on day 4, with the aim of providing more time for expanding from six to nine the number of diagnosed chromosomes per single cell (Group 2; 45 cycles). The results obtained were compared to those derived from conventional day 3 transfer (Group 1; 71 cycles). METHODS: For multicolor fluorescence in situ hybridization analysis, two panels of probes were used: the first, specific for chromosomes XY, 13, 16, 18, and 21, was tested in all patients (Groups 1 and 2); the second was implemented only in Group 2 patients for the detection of chromosomes 14, 15, and 22. RESULTS: A total of 406 embryos underwent fluorescence in situ hybridization analysis in Group 1, and 236 in Group 2. Comparable percentages of both chromosomal abnormalities (61% and 62%) and pregnancy and implantation rates (36% and 24.5% in Group 1, 41% and 23.6% in Group 2) resulted, regardless of the higher mean age in Group 2. CONCLUSIONS: The diagnosis of the nine chromosomes which are most frequently associated with aneuploidy in humans could have an immediate impact on the rate of spontaneous abortions. Additional advantages are represented by the more accurate morphological evaluation of euploid embryos; the advanced compaction, which means that embryos are less exposed to damage during the transfer procedure; and the possibility of performing a reanalysis in cases where a fluorescence in situ hybridization diagnosis is not obtained.

Adult↗