Medical Library

A novel high-capacity ion trap-quadrupole tandem mass spectrometer.

We describe a prototype tandem mass spectrometer that is designed to increase the efficiency of linked-scan analyses by >100-fold over conventional linked-scan instruments. The key element of the mass spectrometer is a novel high ion capacity ion trap, combined in tandem configuration with a quadrupole collision cell and a quadrupole mass analyzer (i.e. a TrapqQ configuration). This ion trap can store >10(6) ions without significant degradation of its performance. The current mass resolution of the trap is 100-450 full width at half maximum for ions in the range 800-4000 m/z, yielding a 10-20 m/z selection window for ions ejected at any given time into the collision cell. The sensitivity of the mass spectrometer for detecting peptides is in the low femtomole range. We can envisage relatively straightforward modifications to the instrument that should improve both its resolution and sensitivity. We tested the tandem mass spectrometer for collecting precursor ion spectra of all the ions stored in the trap and demonstrated that we can selectively detect a phosphopeptide in a mixture of non-phosphorylated peptides. Based on this prototype instrument, we plan to construct a fully functional model of the mass spectrometer for detecting modification sites on proteins and profiling their abundances with high speed and sensitivity.

Krutchinsky AN, Cohen H, Chait BT.

Department of Pharmaceutical Chemistry, UCSF, MC 2280, Mission Bay, GH, Room S512F, 600 16th Street, San Francisco, CA 94158-2517, USA.

Turbulence-induced square-root broadening of the Raman fiber laser output spectrum.

The output characteristics of the conventional one-stage Raman fiber laser (RFL) are described in an optical wave turbulence formalism. Simple analytical expressions describing RFL output power and its spectral shape are presented, and square-root law for the output spectrum broadening law has been discovered. The indications of the turbulent-like spectral broadening in other types of cw fiber lasers and propagation phenomena in fibers are also discussed.

Babin SA, Churkin DV, Ismagulov AE, Kablukov SI, Podivilov EV.

Simultaneous time- and wavelength-resolved fluorescence spectroscopy for near real-time tissue diagnosis.

A novel fiber-optic-based method for simultaneous time- and wavelength-resolved fluorescence spectroscopy for the rapid diagnosis of diseased tissue is demonstrated. By combining multiple bandpass and dichroic filters (405/40, 460/50, and 550/50) with different lengths of optical fiber (1, 10, and 19 m) acting as an optical delay this system enables the near real-time acquisition and characterization of time-resolved fluorescence spectra using a single detector and excitation input. The recording of multiple fluorescence response pulses at selected wavelengths can be completed in hundreds of nanoseconds, which provides the capability of a real-time characterization of biological systems.

Sun Y, Liu R, Elson DS, Hollars CW, Jo JA, Park J, Sun Y, Marcu L.

Combined Mueller and Jones matrix method for the evaluation of the complex modulation in a liquid-crystal-on-silicon display.

We apply the polar decomposition of the Mueller matrix describing a liquid-crystal-on-silicon display to identify the diattenuator, depolarizer, and retarder contributions as a function of the gray level. The retarder contribution is expressed in terms of the equivalent Jones matrix to apply previous techniques to evaluate the phase modulation. This allows searching for optimized polarization configurations for phase- or amplitude-only modulation responses. We present results for lambda=633 nm showing a phase-only modulation up to 2pi rad and flat intensity modulation.

Moreno I, Lizana A, Campos J, Márquez A, Iemmi C, Yzuel MJ.

Scattering differentiates Alzheimer disease in vitro.

The molecular bases of Alzheimer disease and related neurodegenerative disorders are becoming better understood, but the means for definitive diagnosis and monitoring in vivo remain lacking. Near-infrared optical spectroscopy offers a potential solution. We acquired transmission and reflectance spectra of thin brain tissue slabs, from which we calculated wavelength-dependent absorption and reduced scattering coefficients from 470-1000 nm. The reduced scattering coefficients in the near infrared clearly differentiated Alzheimer from control specimens. Diffuse reflectance spectra of gross brain tissue in vitro confirmed this observation. These results suggest a means for diagnosing and monitoring Alzheimer disease in vivo, using near-infrared optical spectroscopy.

Hanlon EB, Perelman LT, Vitkin EI, Greco FA, McKee AC, Kowall NW.

Broadband light generation at ~1300 nm through spectrally recoiled solitons and dispersive waves.

We experimentally study the generation of broadband light at ~1300 nm from an 810 nm Ti:sapphire femtosecond pump laser. We use two photonic crystal fibers with a second infrared zero-dispersion wavelength (lambda(Z2)) and compare the efficiency of two schemes: in one fiber lambda(Z2)=1400 nm and the light at 1300 nm is composed of spectrally recoiled solitons; in the other fiber lambda(Z2)=1200 nm and the light at 1300 nm is composed of dispersive waves.

Falk P, Frosz MH, Bang O, Thrane L, Andersen PE, Bjarklev AO, Hansen KP, Broeng J.

Plasmon-assisted transparency in metal-dielectric microspheres: erratum.

Rohde C, Hasegawa K, Deutsch M.

Sidelobe reduction of tightly focused radially higher-order Laguerre-Gaussian beams using annular masks.

We report the reduction of sidelobes in tight focusing patterns of radially higher-order Laguerre-Gaussian (LG) beams with nonhelical phase structures. Numerical calculations based on the vectorial Debye theory reveal that a class of annular masks reduces sidelobes in the tight focusing patterns only for radially even-order LG beams. The present scheme produces small focal spots beyond the diffraction limit suitable for application to scanning microscopy, laser fine processing, etc.

Ohtake Y, Ando T, Inoue T, Matsumoto N, Toyoda H.

Distributed feedback fiber laser pumped by multimode laser diodes.

A distributed feedback fiber laser made of highly Er-Yb codoped phosphate glass fiber has been demonstrated experimentally. Efficient pump absorption allows for multimode pumping into the cladding of the active fiber. Output powers up to 160 mW have been achieved. The 35 mm long fiber laser device emits with >50 dB side mode suppression ratio.

Schülzgen A, Li L, Nguyen D, Spiegelberg Ch, Rogojan RM, Laronche A, Albert J, Peyghambarian N.

Diamond nanocrystals hosting single nitrogen-vacancy color centers sorted by photon-correlation near-field microscopy.

Diamond nanocrystals containing highly photoluminescent color centers are attractive, nonclassical, and near-field light sources. For near-field applications, the size of the nanocrystal is crucial, since it defines the optical resolution. Nitrogen-vacancy (NV) color centers are efficiently created by proton irradiation and annealing of a nanodiamond powder. Using near-field microscopy and photon statistics measurements, we show that nanodiamonds with sizes down to 25 nm can hold a single NV color center with bright and stable photoluminescence.

Sonnefraud Y, Cuche A, Faklaris O, Boudou JP, Sauvage T, Roch JF, Treussart F, Huant S.