Mining Translation Inhibitors by a Unique Peptidyl-Aminonucleoside Synthetase Reveals Cystocin Biosynthesis and Self-Resistance.

Puromycin (Puro) is a natural aminonucleoside antibiotic that inhibits protein synthesis by its incorporation into elongating peptide chains. The unique mechanism of Puro finds diverse applications in molecular biology, including the selection of genetically engineered cell lines, in situ protein synthesis monitoring, and studying ribosome functions. However, the key step of Puro biosynthesis remains enigmatic.

Laser welding of fiber array units.

We report the results of fabricating fiber array unit (FAU) connectors using a near IR laser welding process, locking fibers in proper position on planar glass substrates and forming strong glass-to-glass bonds, followed by final assembly using lower coefficient of thermal expansion (CTE) epoxies. A thin metal film deposited on the glass substrate provides the absorption required to attain interfacial temperatures suitable for glass-to-glass bonding. This method allows the elimination of dedicated expensive V-groove plates while still maintaining very good fiber placement accuracy.

Characterizing the Antimicrobial Properties of 405 nm Light and the Corning® Light-Diffusing Fiber Delivery System.

Background And Objectives: Hospital-acquired infections (HAIs) and multidrug resistant bacteria pose a significant threat to the U.S. healthcare system.

Extraordinary laser-induced swelling of oxide glasses.

We describe a novel process of laser-assisted fabrication of surface structures on doped oxide glasses with heights reaching 10 - 13% of the glass thickness. This effect manifests itself as a swelling of the irradiated portion of the glass, which occurs in a wide range of glass compositions. The extent of such swelling depends on the glass base composition.

Photothermal behavior of an optical path adhesive used for photonics applications at 1550 nm.

A theoretical and experimental study of photothermal behavior in a commercially available optical path adhesive is described. Photothermal effects were examined for cw and pulsed laser radiation (approximately 1 micros) at 1550 nm. A fiber-optic backreflection technique was used to measure the thermo-optic glass transition temperature of the adhesive.

Cavity ringdown detection of losses in thin films in the telecommunication wavelength window.

The method of cavity ringdown spectroscopy (when a tunable pulsed optical parametric oscillator was used) was extended for the loss evaluation in thin films (2-20-microm thickness). The technique was applied in two key telecommunication wavelength ranges of 1260-1330 and 1480-1650 nm. The measurement sensitivity was determined to be 50 ppm (5 x 10(-5)).

Fiber-optic power limiter based on photothermal defocusing in an optical polymer.

We describe the performance of a fiber-optic power-limiting component. The passive device is dynamically responsive to the input signal and has been shown to attenuate continuous-wave power with a dynamic range of up to 9 dB at 150 mW of input power at 1550 nm. The limiting threshold is approximately 30 mW from 1530 to 1565 nm and less than 10 mW at 1430 nm.

The relaxation dynamics of the excited electronic states of retinal in bacteriorhodopsin by two-pump-probe femtosecond studies.

We present the results of two-pump and probe femtosecond experiments designed to follow the relaxation dynamics of the lowest excited state (S(1)) populated by different modes. In the first mode, a direct (S(0) --> S(1)) radiative excitation of the ground state is used. In the second mode, an indirect excitation is used where the S(1) state is populated by the use of two femtosecond laser pulses with different colors and delay times between them.

Catalysis of the retinal subpicosecond photoisomerization process in acid purple bacteriorhodopsin and some bacteriorhodopsin mutants by chloride ions.

The dynamics and the spectra of the excited state of the retinal in bacteriorhodopsin (bR) and its K-intermediate at pH 0 was compared with that of bR and halorhodopsin at pH 6.5. The quantum yield of photoisomerization in acid purple bR was estimated to be at least 0.

Replacement effects of neutral amino acid residues of different molecular volumes in the retinal binding cavity of bacteriorhodopsin on the dynamics of its primary process.

We have determined the rate and quantum yield of retinal photoisomerization, the spectra of the primary transients, and the energy stored in the K intermediate in the photocycle of some bacteriorhodopsin mutants (V49A, A53G, and W182F) in which residue replacements are found to change the Schiff base deprotonation kinetics (and thus the protein-retinal interaction). Because of their change in the local volume resulting from these individual replacements, these substitutions perturb the proton donor-acceptor relative orientation change and thus the Schiff base deprotonation kinetics. These replacements are thus expected to change the charge distribution around the retinal, which controls its photoisomerization dynamics.

Spot size reduction in coupling of laser to micromanipulator in laser microsurgery by fiberoptic link.

Background And Objective: In coupling laser with micromanipulator through fiberoptics, the resulting diameter of the spot is limited by the laws of geometrical optics, because of the high numerical aperture (N.A.) of fiberoptic radiation.

The pH dependence of the subpicosecond retinal photoisomerization process in bacteriorhodopsin: evidence for parallel photocycles.

The pH dependence of the subpicosecond decay of the retinal photoexcited state in bacteriorhodopsin (bR) is determined in the pH range 6.8-11.3.

Effect of replacing the primary quinone by different species on the ultrafast photosynthetic electron transfer in bacterial reaction centres.

Using picosecond absorption spectroscopy it has been shown that in Rhodobacter sphaeroides reaction centres the substitution of the primary quinone acceptor (QA), ubiquinone-10, by other quinone species (with redox potentials higher or lower than that of ubiquinone-10) has essentially no modifying effect on the reaction centre protein. The molecular relaxation processes that accompany the localization and stabilization of a photo-excited electron on the intermediate acceptor, bacteriopheophytin (I), are not affected, although the subsequent transfer of the electron from I to QA is slowed down. Consequently, this leads to a lower quantum efficiency of high rate of direct I-----QA reaction is normally due to the specificity of the primary quinone species and its binding site in the reaction centre protein which provide optimum steric and chemical conditions for an effective interaction between I and QA.