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The dissociation constant K(d) of the photosystem I (PSI):ferredoxin complex has been measured by backscattering interferometry (BSI) with cyanobacterial PSI (350 kDa) and ferredoxin (10.5 kDa). The BSI signal, consisting of shifts for interference fringes resulting from a change in refractive index due to complex formation, was monitored as ferredoxin concentration was titrated. K(d) values of 0.14-0.38 microM were obtained with wild-type PSI whereas no complex was detectable with a PSI mutant containing a single mutation (R39Q) in the PsaE extrinsic subunit. These results are in quantitative agreement with previous functional determinations consisting in the detection of fast electron transfer within the complex. They provide evidence that the main contribution for the high affinity binding of ferredoxin to PSI is due to a single region of PsaE comprising arginine 39. They do not support the existence of a secondary binding site that could have escaped functional detection.
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http://dx.doi.org/10.1021/ja102208u | DOI Listing |
We present a multibeam lidar system that simultaneously transmits an array of low-crosstalk codes and detects the backscattered returns from all directions on a single large-area high-speed detector via direct detection, without a local oscillator beam. We generate a series of long, time-shifted, self-synchronizing maximum-length pseudo-noise (PN) codes in the form of an array of intensity-modulated beams from a single aperture, using only two traveling-wave acousto-optic deflectors (AODs). The cascaded AODs, driven by counter-propagating acoustic waves, are imaged onto each other, and the diffracted fields are imaged onto the far field target, where the interferometric product between two binary phase-shift keying (BPSK)-encoded maximum-length (ML) sequences generates time-permuted versions of the PN code as an array of beams highly identifiable as well-separated peaks in the cross-correlation.
View Article and Find Full Text PDFWe present a universal technique for noninvasive investigation of thin multilayer optically transparent tissues based on polarization-sensitive optical coherence tomography. To reach higher diagnostic accuracy, we revisit the model of the cornea structure and reconsider the physical features of the interaction of light with the tissue structural elements. In the scheme proposed, the probing beam is algorithmically adjustable such that the x-polarized radiation impinges each consecutive structural layer; the object beam is formed by the reflection and back-scattering.
View Article and Find Full Text PDFClin Implant Dent Relat Res
April 2025
Division of Restorative and Prosthetic Dentistry, College of Dentistry, the Ohio State University, Columbus, Ohio, USA.
Introduction: The long-term success of dental implants depends on the preservation of supporting tissues over time. Recent studies have highlighted the release of titanium particles as a potential etiology for the onset and progression of peri-implant diseases modulated by inflammatory biomarkers. This study provides a comprehensive analysis of surface changes associated with high insertion torque placement.
View Article and Find Full Text PDFTalanta
April 2025
Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada. Electronic address:
A microanalytical technique based on the photothermal effect in conjunction with back-scattering interferometry (BSI) using a single laser beam was developed for quantitative detection of heavy metals. After the chromogenic reaction of an analyte in a capillary tube, the photothermal effect induced by irradiation with the same laser beam leads to a change of the refractive index of the solution, which can be "quantified" using the BSI technique. For prove-of-concept, Cu(II) was chosen as the trial analyte, for which the solution changes to purplish through reacting with the chromogenic reagent; a single laser beam of 532 nm was adapted for both inducing the photothermal effect and realizing BSI detection.
View Article and Find Full Text PDFPhys Rev E
October 2024
Department of Chemistry and Physics, Mount Royal University, Calgary, Alberta, Canada.
In data mining, density-based clustering, which entails classifying datapoints according to their distributions in some space, is an essential method to extract information from large datasets. With the advent of software-based radio, ionospheric radars are capable of producing unprecedentedly large datasets of plasma turbulence backscatter observations, and new automatic techniques are needed to sift through them. We present an algorithm to automatically identify and track clusters of radar echoes through time, using dbscan, a celebrated density-based clustering method for noisy point clouds.
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