19 research outputs found
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Using lasers to probe the transient light absorption by proteorhodopsin in marine bacterioplankton
We constructed an experimental apparatus that used lasers to provide the probe beams for measuring the transient absorption kinetics of bacterioplankton that contain proteorhodopsin, a microbial protein that binds retinal and is analogous to animal rhodopsin. With this approach we were able to observe photocycles characteristic of functioning retinylidene ion pumps. Using light from lasers instead of broadband sources as transmittance probe beams can be advantageous when examining optically dense, highly scattering samples such as concentrated microbial cultures. Such a laser-based approach may prove useful in shipboard studies for identifying proteorhodopsin in whole cell suspensions concentrated from seawater.This paper was published in Applied Optics and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/ao/home.cfm. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law
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In situ monitoring of ocean chlorophyll via laser-induced fluorescence backscattering through an optical fiber
The first seagoing test of a prototype laser/fiber-optic system for in situ detection of ocean chlorophyll fluorescence is described. Radiation at 488 nm originating from a shipboard argon laser was transmitted through 20 of 200-µm core optical fiber to the distal tip mounted on the microstructure profiler, the Rapid Sampling Vertical Profiler. The backscattered fluorescence emission signal was collected through the same fiber and processed on board ship. A series of measurements indicated that (1) successful isolation of shipinduced vibrations could be achieved using our optical bench framework to maintain optical alignments; (2) ambient chlorophyll concentrations could be detected in situ; (3) a Raman scattering signal from water could also be detected and should provide an internal standard against which chlorophyll fluorescence may be calibrated.This paper was published in Applied Optics and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/ao/home.cfm. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law
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Multiple excitation fluorometer for in situ oceanographic applications
A new in situ fluorometer for the detection of oceanic photosynthetic pigment fluorescence is described.
Emission spectra from 546 to 733 nm are recorded for each of three different visible excitation bands ten
times a second. A Spectralon cell is used to improve the excitation coupling to and the collection
efficiency from the sample volume. Laboratory tests demonstrated that the fluorescence emission spectra
from the violet, blue, and green excitation can be used to discriminate among various algal species.
The instrument was used at sea in extended in situ deployments on an undulating vehicle (SeaSoar).This paper was published in Applied Optics and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://www.opticsinfobase.org/ao/home.cfm. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.Keywords: In situ excitation fluorometer, oceanography, chlorophyll fluorescenc
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Microstructure Profiles of Laser-induced Chlorophyll Fluorescence Spectra: Evaluation of Backscatter and Forward-Scatter Fiber-Optic Sensors
The implementation and characterization of backscatter and forward-scatter fiber-optic fluorescence sensors attached to a microstructure profiling instrument are described. By using an optical multichannel array detector to record emission spectra, eight profiles per hour of chlorophyll fluorescence spectra at 2-cm intervals can be obtained throughout the upper 100 m of ocean. The advantages and disadvantages realized by the deployment of the two sensors are compared with respect to the determination of in situ chlorophyll concentrations and fluorescence microstructure in the ocean. It is concluded that the forward-scatter sensor has better signal-to-noise and signal variability characteristics than does the backscatter sensor and is less susceptible to nonlinear fluorescence responses of phytoplankton due to effects such as fluorescence induction