Ratiometric analysis of fluorescence lifetime for probing binding sites in albumin with near-infrared fluorescent molecular probes

A number of diseases have been linked to abnormal conformation of albumin, a major extracellular protein in blood. Current protein structural analysis requires pure isolated samples, thereby limiting their use for albumin analysis in blood. In this study, we report a new approach for high-throughput structure-related analysis of albumin by using the fluorescence lifetime properties of near-infrared (NIR) polymethine dyes. Based on molecular modeling, polymethine dyes are bound to two binding sites with different polarities on albumin. As a result, an NIR molecular probe exhibits two distinct lifetimes with two corresponding fluorescent fractional contributions. The distribution of fractional contributions along with individual fluorescence lifetimes represents unique parameters for characterizing albumin architecture by ratiometric analysis. After screening a small library of NIR polymethine dyes, we identified and used a polymethine dye with optimal fluorescence lifetime properties to assess structure-related differences in commercially available bovine serum albumin as model systems. The results show that changes in the lifetime of NIR dyes reflect the perturbation of the tertiary structures of albumin and that albumin prepared by different methods has slightly altered tertiary structures. Because of the reduced absorption of light by blood in the NIR region, the method developed can be used to determine structural changes in albumin in whole blood without prior isolation of the pure protein.     

Near-infrared fluorescent molecular probes for imaging and diagnosis of nephro-urological diseases

Near-infrared (NIR) fluorescence imaging has improved imaging depth relative to conventional fluorescence imaging in the visible region, demonstrating great potential in both fundamental biomedical research and clinical practice. To improve the detection specificity, NIR fluorescence imaging probes have been under extensive development. This review summarizes the particular application of optical imaging probes with the NIR-I window (700–900 nm) or the NIR-II window (1000–1700 nm) emission for diagnosis of nephron-urological diseases. These molecular probes have enabled contrast-enhanced imaging of anatomical structures and physiological function as well as molecular imaging and early diagnosis of acute kidney injury, iatrogenic ureteral injury and bladder cancer. The design strategies of molecular probes are specifically elaborated along with representative imaging applications. The potential challenges and perspectives in this field are also discussed.

Near-infrared fluorescent molecular probes with improved imaging depth and optimized biodistribution have been reviewed, showing great potential for diagnosis of nephro-urological diseases.     

Bioinspired molecular design of light-harvesting multiporphyrin arrays

Recent progress in fundamental studies on multiporphyrin arrays has provided structural parameters for the molecular design of artificial light-harvesting antennae which mimic the wheel-like antenna complexes of photosynthetic purple bacteria. Covalent and noncovalent approaches have been employed for the construction of artificial light-harvesting multiporphyrin arrays. Such arrays are categorized into ring-shaped, windmill-shaped, star-shaped, and dendritic architectures. In particular, dendritic multiporphyrin arrays have been proven to be promising candidates for both providing a large absorption cross-section and enabling the vectorial transfer of energy over a long distance to a designated point. Such molecular and supramolecular systems are also expected to be potent components for molecular electronics and photonic devices.     

Synthesis and photophysical,antibacterial studies of some novel molecular tweezers

Zeroth and first generation dendritic wedges with thiophene amide as surface group and 1, 2, 3-triazole as bridging unit which can function as molecular tweezers are synthesised by both convergent and divergent approaches. All the synthesised dendritic wedges displayed the absorbance band between 256 and 294 nm and fluorescence maximum between 357 and 528 nm supporting their self complementary property. Dendritic wedge 5 showed better antibacterial activity than other dendritic wedges in the assay against the human pathogens viz Staphylococcus aureus, Escherichia coli, Bacillus cereus and Klebsiella pneumonia and the dentritic wedge 5 was also effective in the computational molecular docking studies.     

A direct comparison of one- and two-component dendritic self-assembled materials: elucidating molecular recognition pathways

This paper compares and contrasts, for the first time, one- and two-component gelation systems that are direct structural analogues and draws conclusions about the molecular recognition pathways that underpin fibrillar self-assembly. The new one-component systems comprise l-lysine-based dendritic headgroups covalently connected to an aliphatic diamine spacer chain via an amide bond. One-component gelators with different generations of headgroup (from first to third generation) and different length spacer chains are reported. The self-assembly of these dendrimers in toluene was elucidated using thermal measurements, circular dichroism (CD) and NMR spectroscopies, scanning electron microscopy (SEM), and small-angle X-ray scattering (SAXS). The observations are compared with previous results for the analogous two-component gelation system in which the dendritic headgroups are bound to the aliphatic spacer chain noncovalently via acid-amine interactions. The one-component system is inherently a more effective gelator, partly as a consequence of the additional covalent amide groups that provide a new hydrogen bonding molecular recognition pathway, whereas the two-component analogue relies solely on intermolecular hydrogen bond interactions between the chiral dendritic headgroups. Furthermore, because these amide groups are important in the assembly process for the one-component system, the chiral information preset in the dendritic headgroups is not always transcribed into the nanoscale assembly, whereas for the two-component system, fiber formation is always accompanied by chiral ordering because the molecular recognition pathway is completely dependent on hydrogen bond interactions between well-organized chiral dendritic headgroups.     

Increasing materials' response to two-photon NIR light via self-immolative dendritic scaffolds

Photoactivation using two photons of NIR allows non-invasive biological manipulation. We applied the principle of dendritic amplification to improve the materials' sensitivity to NIR light. Light induced uncaging or release of L-glutamic acid was 2.8 fold higher when incorporating 4-bromo-7-hydroxycoumarin (Bhc) with self-immolative dendrimers compared with Bhc directly conjugated to L-glutamic acid.     

Theoretical consideration of the molecular mass distribution of starlike polymers formed by attachment of linear polymers to dendritic cores

Star‐shaped polymers can be synthesized by condensation of linear polymers to dendritic cores. The distribution of molecular masses of such hybrid star polymers and the factors influencing it have been investigated by calculations based on population balance equations and Laplace transformations. Moreover, the expressions for numerical calculations of molecular mass distributions have been derived for both Poisson and Schultz–Zimm types of initial molecular mass distributions. According to the calculation results, the molecular mass distribution of the star polymers is strongly dependent on the distribution of the length of linear polymers. Beyond this, the molecular mass development is affected by several parameters that describe the reaction degree of dendritic cores, thus, by the fraction of all functional groups of dendritic cores involved in grafting, denoted by p; the average branching degree of one starlike molecule, represented by ρ; or the fraction of dendritic molecules becoming the cores of star polymers, expressed by p/ρ, provided the star molecule contains only one core. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2751–2758, 2001     

Computer simulation of architectural and molecular weight effects on the assembly of amphiphilic linear-dendritic block copolymers in solution

Langevin dynamics simulations are performed on linear-dendritic diblock copolymers containing bead-spring, freely jointed chains composed of hydrophobic linear monomers and hydrophilic dendritic monomers. The critical micelle concentration (CMC), micelle size distribution, and shape are examined as a function of dendron generation and architecture. For diblock copolymers with a linear block of fixed length, it is found that the CMC increases with increasing dendron generation. This trend qualitatively agrees with experiments on linear-dendritic diblock and triblock copolymers with hydrophilic dendritic blocks and hydrophobic linear blocks. The flexibility of the dendritic block is altered by varying the number of spacer monomers between branch points in the dendron. When comparing linear-dendritic diblock copolymers with similar molecular weights, it is shown that increasing the number of spacer monomers in the dendron lowers the CMC due to an increase in flexibility of the dendritic block. Analysis on the micellar structure shows that linear-dendritic diblock copolymers pack more densely than what would be expected for a linear-linear diblock copolymer of the same molecular weight.     

Self-assembly of molecular dumbbells into organized bundles with tunable size

Dumbbell-shaped molecules consisting of three biphenyls connected through vinyl linkages as a conjugated rod segment and aliphatic polyether dendritic wedges with different cross-sections (i.e., dibranch (1), tetrabranch (2) and hexabranch (3)) were synthesized and characterized. The molecular dumbbells self-assemble into discrete bundles that organize into three-dimensional superlattices. Molecule 1, based on a dibranched dendritic wedge, organizes into primitive monoclinic-crystalline and body-centered, tetragonal liquid crystalline structures, while molecules 2 and 3, based on tetra- and hexabranched dendritic wedges, respectively, form only body-centered, tetragonal liquid crystalline structures. X-ray diffraction experiments and density measurements showed that the rod-bundle cross-sectional area decreases with increasing cross-section of the dendritic wedges. The influences of supramolecular structure on the bulk-state optical properties were investigated by measuring the UV/Vis absorption and steady state fluorescence spectroscopies. As the cross-section of the dendritic wedge of the molecule increases, the absorption and emission maxima shift to higher energy. This can be attributed to a quantum size effect of the three-dimensionally confined nanostructure.     

Silsesquioxane dendrimers as catalysts: a bite-sized molecular dynamics study

A method of calculating the bite (P-M-P) angle for dendritic ligands is reported. Diphenylphosphine terminated dendritic ligands were modified with either a single rhodium or a rhodium complex [HRh(CO)(2)] and molecular dynamics techniques used to run simulations to determine the dynamic bite angle (beta(d)) as a time averaged property. The effects of changing the composition of the dendritic branches is investigated and comparison with experimental hydroformylation data reveals that the dendrimer with the highest linear: branched ratio also has a dynamic bite angle closest to the theoretical ideal value of 120 degrees .     

Near-infrared small molecular fluorescent dyes for photothermal therapy

This review aims to provide a summary of the progress in fluorescent dyes for photothermal therapy in recent years and it is classified according to the structure of organic molecules including cyanines, phthalocyanines, rhodamine analogues and BODIPYs.     

Synthesis and evaluation of polyhydroxylated near-infrared carbocyanine molecular probes

[reaction: see text] A new near-infrared (NIR) fluorescent molecular probe derived from indocarbocyanine dye and galactose was prepared, and the procedure was optimized. The presence of a nonionic polyhydroxyl moiety between hydrophobic groups enhances solubility and possibly minimizes aggregation in aqueous solutions. The structural framework of this molecule provides multivalent sites for labeling diverse molecules.     

Near‐Infrared Optogenetic Genome Engineering Based on Photon‐Upconversion Hydrogels

Photon upconversion (UC) from near‐infrared (NIR) light to visible light has enabled optogenetic manipulations in deep tissues. However, materials for NIR optogenetics have been limited to inorganic UC nanoparticles. Herein, NIR‐light‐triggered optogenetics using biocompatible, organic TTA‐UC hydrogels is reported. To achieve triplet sensitization even in highly viscous hydrogel matrices, a NIR‐absorbing complex is covalently linked with energy‐pooling acceptor chromophores, which significantly elongates the donor triplet lifetime. The donor and acceptor are solubilized in hydrogels formed from biocompatible Pluronic F127 micelles, and heat treatment endows the excited triplets in the hydrogel with remarkable oxygen tolerance. Combined with photoactivatable Cre recombinase technology, NIR‐light stimulation successfully performs genome engineering resulting in the formation of dendritic‐spine‐like structures of hippocampal neurons.     

Label-free molecular imaging of immunological synapses between dendritic and T cells by Raman micro-spectroscopy

Confocal Raman micro-spectroscopy (CRMS) was used to measure spectral images of immunological synapse formation between dendritic and T cells without using molecular labels or other invasive procedures. The purpose-built inverted CRMS instrument integrated an environmental enclosure and a near-infrared laser to allow measurements on live cells maintained under physiological conditions. The integration of the wide-field fluorescence also enabled viability assays and direct comparison between Raman spectral images and gold-standard immuno-fluorescence images for specific molecules. Raman spectral images of nucleus and proteins were built by fuzzy c-mean clustering method. The Raman images were found to be in good correspondence with the immuno-fluorescence images of DNA and actin. These results indicate that actin is a main contributor to the Raman spectrum of the cytoplasm of dendritic and T cells. While for control cells the Raman spectral images of proteins indicated a more homogeneous distribution of proteins in the cytoplasm of dendritic cells, they indicated a higher accumulation of proteins at the immunological synapses when dendritic cells were pre-treated with laminin. These conclusions were also supported by confocal immuno-fluorescence imaging after cell fixation and labelling. This study demonstrates the potential of CRMS for label-free non-invasive imaging of junctions between live cells. Therefore, this technique may become a useful tool for studying cellular processes in live cells and where non-invasive molecular specific imaging is desirable, such as cell-cell interactions.     

Palladium catalysis using dendrimers: molecular catalysts versus nanoparticles

Dendritic Pd catalysts, dendrimer-stabilized Pd nanoparticle (PdNP) catalysts, and their comparison and combined use for carbon–carbon coupling reactions are discussed with emphasis on the research carried out in the author’s laboratory during the last decade. Multinuclear star-shaped catalysts rather than dendritic catalysts can reach the efficiency of the best monometallic catalysts, whereas PdNPs stabilized by dendrimers can react with turnover numbers close to 10⁶ and bring useful mechanistic indications. In both areas, leaching issues are examined. Finally, results of the literature in asymmetric Pd catalysis by chiral dendrimers and Pd nanoparticles stabilized by chiral ligands are also reviewed, revealing the importance of the dendritic and molecular ligand design and the role of leaching Pd atoms.     

Examination of chlorin-bacteriochlorin energy-transfer dyads as prototypes for near-infrared molecular imaging probes

Abstract New classes of synthetic chlorin and bacteriochlorin macrocycles are characterized by narrow spectral widths, tunable absorption and fluorescence features across the red and near-infrared (NIR) regions, tunable excited-state lifetimes (<1 to >10 ns) and chemical stability. Such properties make dyad constructs based on synthetic chlorin and bacteriochlorin units intriguing candidates for the development of NIR molecular imaging probes. In this study, two such dyads (FbC-FbB and ZnC-FbB) were investigated. The dyads contain either a free base (Fb) or zinc (Zn) chlorin (C) as the energy donor and a free base bacteriochlorin (B) as the energy acceptor. In both constructs, energy transfer from the chlorin to bacteriochlorin occurs with a rate constant of approximately (5 ps)(-1) and a yield of >99%. Thus, each dyad effectively behaves as a single chromophore with an exceptionally large Stokes shift (85 nm for FbC-FbB and 110 nm for ZnC-FbB) between the red-region absorption of the chlorin and the NIR fluorescence of the bacteriochlorin (lambda(f) = 760 nm, Phi(f) = 0.19, tau approximately 5.5 ns in toluene). The long-wavelength transitions (absorption, emission) of each constituent of each dyad exhibit narrow (相似文献   

Dendronized molecular knots: selective synthesis of various generations,enantiomer separation,circular dichroism

For the first time, knot molecules (of the amide type) are synthesized, which bear one to three dendritic units of various generations at their periphery. They were obtained through two different routes: i) attachment of dendritic wedges to new mono-, di- and trihydroxy functionalized dodecaamide knots that have been obtained by selective debenzylation of oligobenzyloxy substituted knots, or ii) cyclization of already dendron substituted pyridine-2,6-dicarbonyl dichlorides with an "extended diamine" to directly yield the "tri-dendroknots". The derivatization of knot molecules by functional substituents and even large dendritic units is an important advance in the synthesis and property variation of molecular knots. This holds true in particular for substitution of the pyridine units of the knots, whereas the isophthalic acid units seem not to tolerate larger substitutents, as reflected in lower knot yields. These syntheses also demonstrate knots to be accessible indirectly by substitution of the corresponding mono-, di- and tri-functionalized knot skeleton. An advantage of dendritic "decoration" is the control of solubility and chromatographic behaviour of the molecular knots (knotanes). Suggestions are made about the threading mechanism by supramolecular template effects leading to the formation of amide-based molecular knots. The topological chirality of the new "dendroknots" is shown by efficient enantioseparations (separation factor alpha between 1.22 and 1.48). For this purpose (commercially unavailable) chiral column material of the Chiralpak type was used, in which the chiral component is covalently bonded to the silica gel support. The racemate splittings provide additional evidence for the knotted structure, as all other conceivable isomers such as macromonocyclic or catenated dodecaamides would not be chiral. The pure enantiomers obtained exhibit pronounced Cotton effects in their circular dichroism spectra. By comparison with the unsubstituted knot, the absolute configuration (Lambda, Delta) of all new knots is derived.     

The spatial effect of near-infrared spectroscopy and its application to the study of supramolecular chemistry

An unlooked-for experimental observation that in near-infrared spectroscopy (NIR) the absorption peak of the second overtone of aniline adsorbed by 13X molecular sieve nearly disappeared led us investigate a fundamental question: the behavior of NIR when the outside space surrounding a molecule is too small to allow the molecule to vibrate freely. Through NIR of various organic compounds adsorbed by different porous inorganic materials like 13X molecular sieve, silica gel and active aluminium oxide, and NIR of supramolecular cyanuric acid-melamine, we can reasonably confirm a theoretical inference that in the micro-environment above, all intensities of NIR absorbance decrease, and the second overtone decreases more than the first overtone does. Furthermore, one distinct feature of NIR, higher sensitivity to the size of micro-environmental space as compared with mid-infrared (MIR), and its potential application to the study of supramolecular structure are outlined by our experiments.     

Iterative molecular assembly based on the cation-pool method. Convergent synthesis of dendritic molecules

An iterative method for molecular assembly has been developed based on the cation-pool method using (trimethylsilyl)diphenylmethane as a building block. The silyl group works as both an activating group of the benzene ring in the Friedel-Crafts type reaction and an electroauxiliary in the subsequent low temperature anodic oxidation to generate dendritic diarylcarbenium ions, which were well characterized by low-temperature NMR spectroscopy. The convergent synthesis of dendritic molecules has been achieved by repeating the sequence.     

Morphology and molecular organisation of liquid-crystalline perylene-3,4,9,10-tetra-(n-hexylester) deposited on a solid substrate

Liquid-crystalline perylene-3,4,9,10-tetra-(n-hexylester) forms characteristic dendritic or flower-like structures at room temperature when it is deposited on a hydrophilic glass substrate using the zone-casting technique. It was found that such unique structures were not possible to be created simply by recrystallisation of this dye from a liquid-crystalline columnar phase. On the basis of the observations using a confocal microscope and the study of wide angle X-ray scattering (WAXS) as well as the analysis of the absorption and fluorescence spectra, some conclusions, concerning the molecular organisation in the dendritic structure, are drawn. Based on the research, one can assume that the dendrites are formed by columnar molecular aggregates with the column axes parallel to the substrate. Such an organisation of the molecules can be interesting from the point of view of organic electronics.