Y.-G. Yang

Design and Synthesis of Fluorinated Dendrimers for Sensitive F-19 MRI

To achieve high sensitivity for (19)F MRI, a class of novel dendritic molecules with multiple pseudosymmetrical fluorines was designed and efficiently synthesized. Through iterative bromination and Williamson ether synthesis under mild conditions, a fluorinated dendrimer with 540 pseudosymmetrical fluorines was conveniently prepared without performing the group protection in a convergent way. The dendrimer is characterized by a strong (19)F NMR peak and short relaxation times. Eventually, an appreciably enhanced (19)F MRI at an extremely low concentration (18.5 μM) was achieved, which demonstrated the potential utility of such dendritic molecules in highly sensitive (19)F MRI.

Mitochondria Targeted and Intracellular Biothiol Triggered Hyperpolarized 129Xe Magnetofluorescent Biosensor

Biothiols such as gluthathione (GSH), cysteine (Cys), homocysteine (Hcy), and thioredoxin (Trx) play vital roles in cellular metabolism. Various diseases are associated with abnormal cellular biothiol levels. Thus, the intracellular detection of biothiol levels could be a useful diagnostic tool. A number of methods have been developed to detect intracellular thiols, but sensitivity and specificity problems have limited their applications. To address these limitations, we have designed a new biosensor based on hyperpolarized xenon magnetic resonance detection, which can be used to detect biothiol levels noninvasively. The biosensor is a multimodal probe that incorporates a cryptophane-A cage as 129Xe NMR reporter, a naphthalimide moiety as fluorescence reporter, a disulfide bond as thiol-specific cleavable group, and a triphenylphosphonium moiety as mitochondria targeting unit. When the biosensor interacts with biothiols, disulfide bond cleavage leads to enhancements in the fluorescence intensity and changes in the 129Xe chemical shift. Using Hyper-CEST (chemical exchange saturation transfer) NMR, our biosensor shows a low detection limit at picomolar (10-10 M) concentration, which makes a promise to detect thiols in cells. The biosensor can detect biothiol effectively in live cells and shows good targeting ability to the mitochondria. This new approach not only offers a practical technique to detect thiols in live cells, but may also present an excellent in vivo test platform for xenon biosensors.

PHOTOMETRIC PROPERTIES FOR SELECTED ALGOL-TYPE BINARIES. VI. THE NEWLY DISCOVERED oEA STAR FR ORIONIS

New photometry of the neglected eclipsing binary FR Orionis was obtained in 2012 November and December. Using the updated Wilson–Devinney program, the photometric elements were deduced from two-color light curves. The results indicate that this system is a semi-detached binary, with a mass ratio of 0.325(±0.002) and a fill-out factor of the primary of fp = 73.5(±0.2)%. The oscillating light curves imply that FR Ori may be an oscillating EA (oEA)-type star with a rapidly pulsating, mass-accreting primary component. After we removed the theoretical light curves from the observations, Fourier analysis revealed that the more massive component possibly shows a δ Scuti type pulsation with four detected frequencies. The dominant frequency is f1 = 38.6c day −1 (i.e., Ppuls = 37.3 minutes), and the pulsation constant is Q = 0.014 days. Based on all available eclipsing times, the orbital period is undergoing a secular period increase with a rate of dP/dt = +8.85(±0.66) × 10 −8 day yr −1 , which may be interpreted by mass transfer from the secondary to the primary. We expect that the more massive component will fill its Roche lobe due to mass transfer of the secondary. Therefore, the oEA star FR Ori may evolve into a contact configuration.

PHOTOMETRIC STUDIES OF THREE NEGLECTED SHORT-PERIOD CONTACT BINARIES GN BOOTIS, BL LEONIS, AND V1918 CYGNI

We present new photometry for three short-period contact binaries, GN Boo, BL Leo, and V1918 Cyg, observed from 2008 December to 2012 April using several small telescopes in China. Photometric models were deduced from new observations using the updated Wilson-Devinney Code. The results show that GN Boo and BL Leo are W-type contact binaries, while V1918 Cyg is an A-type one. The mass ratios and fill-out factors are q = 0.320(+/- 0.002) and f = 5.8(+/- 0.1)% for GN Boo, q = 0.476(+/- 0.005) and f = 21.3(+/- 1.1)% for BL Leo, q = 0.264(+/- 0.002), and f = 49.7(+/- 0.7)% for V1918 Cyg, respectively. From the (O - C) curves, it is discovered that the orbital periods of three binaries have varied in a complicated way, i.e., cyclic oscillation for GN Boo, long-term period decrease for BL Leo, and both for V1918 Cyg. The cyclic variations for GN Boo and V1918 Cyg may probably be attributed to the magnetic activity of the primary component or light-time effect due to the third body. Meanwhile, the secular period decreases for BL Leo and V1918 Cyg may result from mass transfer from the primary to the secondary, accompanying the mass and angular momentum loss from the central system. Finally, GN Boo, BL Leo, and V1918 Cyg will evolve into deep contact binaries. Additionally, a statistical study of 37 contact binaries with decreasing periods is given. We obtained the relations of q - f and q - d ln P/dt, and preliminarily determined the mass loss rate of d ln M/dt from the binary system.

PHOTOMETRIC PROPERTIES OF SELECTED ALGOL-TYPE BINARIES. III. AL GEMINORUM AND BM MONOCEROTIS WITH POSSIBLE LIGHT-TIME ORBITS

We present the CCD photometry of two Algol-type binaries, AL Gem and BM Mon, observed from 2008 November to 2011 January. With the updated Wilson-Devinney program, photometric solutions were deduced from their EA-type light curves. The mass ratios and fill-out factors of the primaries are found to be q ph = 0.090(± 0.005) and f 1 = 47.3%(± 0.3%) for AL Gem, and q ph = 0.275(± 0.007) and f 1 = 55.4%(± 0.5%) for BM Mon, respectively. By analyzing the O–C curves, we discovered that the periods of AL Gem and BM Mon change in a quasi-sinusoidal mode, which may possibly result from the light-time effect via the presence of a third body. Periods, amplitudes, and eccentricities of light-time orbits are 78.83(± 1.17) yr, 00204(±00007), and 0.28(± 0.02) for AL Gem and 97.78(± 2.67) yr, 00175(±00006), and 0.29(± 0.02) for BM Mon, respectively. Assumed to be in a coplanar orbit with the binary, the masses of the third bodies would be 0.29 M ☉ for AL Gem and 0.26 M ☉ for BM Mon. This kind of additional companion can extract angular momentum from the close binary orbit, and such processes may play an important role in multiple star evolution.

Increasing Cancer Therapy Efficiency through Targeting and Localized Light Activation

Currently, the potential of cancer therapy is compromised by a variety of problems related to tumor specificity, drug access, and limited efficacy. We report a novel approach to improve the effectiveness of cancer treatment utilizing a light-responsive nanoconstruct. Effectiveness is increased by enhancing drug absorption through heating and the production of free radicals. Treatment specificity is increased through chemical targeting of the nanoconstruct and localization of light delivery to the tumor. When reaching the tumor, magnetic resonance imaging is enhanced and near-infrared fluorescence is activated upon drug release, making it possible to visualize the localized treatment at both the tissue and cellular levels. This dual-modality imaging nanoconstruct enables the synergistic treatment and observable evaluation of solid tumors with dramatically improved efficacy, giving rise to a promising new approach for cancer therapy and evaluation.

PHOTOMETRIC PROPERTIES FOR SELECTED ALGOL-TYPE BINARIES. IV. AV HYDRAE AND DZ CASSIOPEIAE

We present BVR photometric observations and several eclipsing times for AV Hya and DZ Cas from 2004 to 2011. Using the Wilson-Devinney method, the photometric solutions with hot spots were deduced from their asymmetric light curves. The results indicate that both stars are Algol-type binaries, whose mass ratio, q(ph), and fill-out factor of the primary, f(1), are q(ph) = 0.255(+/- 0.002) and f(1) = 81.2(+/- 0.2)% for AV Hya, and q(ph) = 0.093(+/- 0.003) and f(1) = 98.7(+/- 0.3)% for DZ Cas. Based on all available light minimum times, it is discovered that the O-C curve of each star could be described by a light-time orbit overlying on a downward parabola. Their periods and amplitudes are P-3 = 37.2(+/- 0.7) yr and A = 0.(d)0095(+/- 0.(d)0006) for AV Hya, and P-3 = 62.5(+/- 1.0) yr andA = 0.(d)0183(+/- 0.(d)0007) for DZ Cas. Cyclic variations may result from the light-time effect due to the third body. The secular period decrease rates are dP/dt = -1.47(+/- 0.04) x 10(-7) days yr(-1) for AV Hya and dP/dt = -0.92(+/- 0.04) x 10(-7) days yr(-1) for DZ Cas. This may be interpreted using mass and angular momentum loss from the system. With decreasing period, the fill-out factor of the primary increases and it may finally fill its inner Roche lobe. Therefore, AV Hya and DZ Cas with a secular period decrease will evolve from semi-detached configurations into contact ones.

Potential detection of cancer with fluorinated silicon nanoparticles in 19F MR and fluorescence imaging

Fluorescence is widely used for cell imaging due to its high sensitivity and rich color choices but limited for in vivo imaging because of its low light penetration. Meanwhile, magnetic resonance imaging (MRI) is widely applied for in vivo diagnosis but not suitable for cell imaging because of its low resolution. As a result of rare background in living organisms, 19F-MRI stands out in several fields of clinical application. Herein, we report a one-pot microwave synthesis of fluorinated silicon nanoparticles (19FSiNPs), for detection of cancer cells and tumors. Based on the quantum effects of the nano-sized nanoparticles, 19FSiNPs can act as a label free dye for ultracontrast cell fluorescence imaging. Our experiments demonstrated that these nanoprobes significantly enhanced in vivo19F/1H MRI contrast in rats with non-small cell lung tumors. Moreover, the resulting 19FSiNPs exhibited high water dispersibility and excellent biocompatibility, which make them promising for both cell imaging and in vivo imaging applications.