Near-infrared fluorescence microscopy of single-walled carbon nanotubes in phagocytic cells

The uptake of pristine single-walled carbon nanotubes into macrophage-like cells has been studied using the nanotubes' intrinsic near-infrared fluorescence. Macrophage samples that have been incubated in growth media containing suspended single-walled nanotubes show characteristic nanotube fluorescence spectra. The fluorescence intensities increase smoothly with incubation time and external nanotube concentration. Near-infrared fluorescence microscopy at wavelengths above 1100 nm provides high contrast images indicating localization of nanotubes in numerous intracellular vesicles. Nanotube uptake appears to occur through phagocytosis. Population growth of macrophage cultures is unaffected by exposure to single-walled nanotube concentrations of ca. 4 mug/mL for up to 96 h.     

Electron density as the main parameter influencing the formation of fullerenes in a carbon plasma

Thermodynamic estimates are presented for the formation of spheroidal and flat carbon clusters from reactant species of different charges. Charge is shown to strongly influence the geometry and stability of flat clusters. Changes in the charge of flat clusters can promote both their folding to spheroidal structures and their dissociation. It is concluded that the fluctuations of electron concentration in carbon plasmas can result in the accumulation of fullerene clusters and the dissociation of flat clusters.     

Ozonides,epoxides, and oxidoannulenes of C(70)

Six new monoadducts of C(70) with oxygen species have been prepared, isolated, and characterized following ozonation of C(70) solutions. The initial products are two ozonide monoadducts, identified as a,b- and c,c-C(70)O(3). These ozonides lose O(2) through thermolysis or photolysis to form various isomers of C(70)O. The a,b-C(70)O(3) isomer dissociates through thermolysis with a decay time of 14 min at 296 K to form the [6,6]-closed epoxide a,b-C(70)O. When photolyzed, it instead forms a [5,6]-open oxidoannulene identified as a,a-C(70)O. These reactions mimic those seen for C(60)O(3). By contrast, the c,c-C(70)O(3) isomer, which has a thermolysis lifetime of 650 min at 296 K, decays thermally only to an oxidoannulene deduced to be d,d-C(70)O. Photolysis of c,c-C(70)O(3) produces a mixture of the oxidoannulenes b,c-C(70)O and c,d-C(70)O plus a minor amount of the c,c-epoxide. All four C(70)O oxidoannulene isomers undergo photoisomerization, giving eventually the a,b- and c,c-C(70)O epoxides.     

Photoproperties of isolated cis and trans stilbene molecules

A detailed account is given of the experimental approach to measuring transient spectra of dilute gases using picosecond pulses. The picosecond continuum generated by Nd:glass laser pulses is used to probe gaseous samples and spectra are recorded in a double beam arrangement. The pump and probe pulses interact with the sample over a few centimeters by means of a dielectric waveguide. Picosecond time resolved spectra, relative fluorescence quantum yield measurements, and fluorescence spectra are reported for trans-stilbene under collision free conditions. The lifetime of the optically prepared states at 265 nm and 287 nm are 15 ps and 55 ps respectively, measured by the decay of the transient absorption. The deuteration effect is less than 20%. The variation of the fluorescence yield with vibrational energy excess in the excited state of trans is fitted to these lifetime measurements to yield the variation of nonradiative decay due to twisting of trans-stilbene. Cis-stilbene is suggested to twist in less than 1 ps. Consideration of the spectral results yields new information about the isomerization of stilbene, in particular that there exists a barrier to twisting in the isolated molecule and that vibrational energy redistribution at the trans configuration is probably not complete on the time scale of our experiments. A pictorial model for discussing constant energy relaxation phenomena is introduced.     

Two-phase flow patterns and void fractions in downward flow Part I: Steady-state flow patterns

Observations of void fractions and flow patterns have been made during steady-state, co-current, downward flow of liquid refrigerant 113 and its vapor. The new data on flow pattern transitions, plus the available downward flow data in the literature, have been compared with available predictions. It was found that the flow pattern map previously developed for horizontal and upward flow can be extended to downward flow with only minor modifications. Part II of this paper will report on the void fraction measurements and the observations of flow pattern transitions during flow transients.     

Effects of fluid properties and pipe diameter on two-phase flow patterns in horizontal lines

Extensive new data have been obtained on the transitions between two-phase flow patterns during co-current gas liquid flow in horizontal lines. Fluid properties were varied in a systematic manner to determine the effects of liquid viscosity, liquid density, interfacial tension and gas density. Line sizes varied from 1.2 to 5 cm for most of the tests. Visual observations were supplemented by an analysis of pressure drop fluctuations and hence the present data are believed to be less subjective than most past observations.

The transition data from the present tests, as well as available literature data, were compared to the most frequently used transition line correlations. In almost all cases serious deficiencies were observed. Revised dimensionless correlations which fit present data, and those previously available, are presented.     

The long and short of it: the influence of N-carboxyethyl versusN-carboxymethyl pendant arms on in vitro and in vivo behavior of copper complexes of cross-bridged tetraamine macrocycles

A cross-bridged cyclam ligand bearing two N-carboxymethyl pendant arms (1) has been found to form a copper(II) complex that exhibits significantly improved biological behavior in recent research towards (64)Cu-based radiopharmaceuticals. Both the kinetic inertness and resistance to reduction of Cu-1 are believed to be relevant to its enhanced performance. To explore the influence of pendant arm length on these properties, new cross-bridged cyclam and cyclen ligands with longer N-carboxyethyl pendant arms, 2 and 4, and their respective copper(II) complexes have been synthesized. Both mono- as well as di-O-protonated forms of Cu-2 have also been isolated and structurally characterized. The spectral and structural properties of Cu-2 and Cu-4, their kinetic inertness in 5 M HCl, and electrochemical behavior have been obtained and compared to those of their N-carboxymethyl-armed homologs, Cu-1 and Cu-3. Only the cyclam-based Cu-1 and Cu-2 showed unusually high kinetic inertness towards acid decomplexation. While both of these complexes also exhibited quasi-reversible Cu(II)/Cu(I) reductions, Cu-2 is easier to reduce by a substantial margin of +400 mV, bringing it within the realm of physiological reductants. Similarly, of the cyclen-based complexes, Cu-4 is also easier to reduce than Cu-3 though both reductions are irreversible. Biodistribution studies of (64)Cu-labeled 2 and 4 were performed in Sprague Dawley rats. Despite comparable acid inertness to their shorter-armed congeners, both longer-armed ligand complexes have poorer bio-clearance properties. This inferior in vivo behavior may be a consequence of their higher reduction potentials.     

Post-Harvest Operations to Generate High-Quality Medicinal Cannabis Products: A Systemic Review

The traditional Cannabis plant as a medicinal crop has been explored for many thousands of years. The Cannabis industry is rapidly growing; therefore, optimising drying methods and producing high-quality medical products have been a hot topic in recent years. We systemically analysed the current literature and drew a critical summary of the drying methods implemented thus far to preserve the quality of bioactive compounds from medicinal Cannabis. Different drying techniques have been one of the focal points during the post-harvesting operations, as drying preserves these Cannabis products with increased shelf life. We followed or even highlighted the most popular methods used. Drying methods have advanced from traditional hot air and oven drying methods to microwave-assisted hot air drying or freeze-drying. In this review, traditional and modern drying technologies are reviewed. Each technology will have different pros and cons of its own. Moreover, this review outlines the quality of the Cannabis plant component harvested plays a major role in drying efficiency and preserving the chemical constituents. The emergence of medical Cannabis, and cannabinoid research requires optimal post-harvesting processes for different Cannabis strains. We proposed the most suitable method for drying medicinal Cannabis to produce consistent, reliable and potent medicinal Cannabis. In addition, drying temperature, rate of drying, mode and storage conditions after drying influenced the Cannabis component retention and quality.     

Oxime as a general photocage for the design of visible light photo-activatable fluorophores

Photoactivatable fluorophores have been widely used for tracking molecular and cellular dynamics with subdiffraction resolution. In this work, we have prepared a series of photoactivatable probes using the oxime moiety as a new class of photolabile caging group in which the photoactivation process is mediated by a highly efficient photodeoximation reaction. Incorporation of the oxime caging group into fluorophores results in loss of fluorescence. Upon light irradiation in the presence of air, the oxime-caged fluorophores are oxidized to their carbonyl derivatives, restoring strong fluorophore fluorescence. To demonstrate the utility of these oxime-caged fluorophores, we have created probes that target different organelles for live-cell confocal imaging. We also carried out photoactivated localization microscopy (PALM) imaging under physiological conditions using low-power light activation in the absence of cytotoxic additives. Our studies show that oximes represent a new class of visible-light photocages that can be widely used for cellular imaging, sensing, and photo-controlled molecular release.

Photoactivatable fluorophores have been widely used for tracking molecular and cellular dynamics with subdiffraction resolution.