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(P700 - P700) Fourier transform visible and infrared difference spectra (DS) have been obtained using photosystem I (PSI) complexes isolated from cells of Fischerella thermalis PCC 7521 grown under white light (WL) or far-red light (FRL). PSI from cells grown under FRL (FRL-PSI) contain ~8 chlorophyll f (Chl f) molecules (Shen et al., Photosynth. Res. Jan. 2019). Both the visible and infrared DS indicate that neither the PA or PB pigments of P700 are Chl f molecules, but do support the conclusion that at least one of the A-1 cofactors is a Chl f molecule. The FTIR DS indicate that the hydrogen bond to the 13-keto CO group of the PA pigment of P700 is weakened in FRL-PSI, as might be expected given that the proteins that bind the P700 pigments are substantially different in FRL-PSI (Gan et al., Science 345, 1312-1317, 2014). The FTIR DS obtained using FRL-PSI display a band at 1664 cm that is assigned (based on density functional theory calculations) to the 2-formyl CO group of Chl f, that upshifts 5 cm upon P700 formation. This is much less than expected for a cation-induced upshift, indicating that the Chl f molecule is not one of the pigments of P700. In WL-PSI the A-1 cofactor is a Chl a molecule with 13-keto and 13-methylester CO mode vibrations at 1696 and 1750 cm, respectively. In FRL-PSI the A-1 cofactor is a Chl f molecule with 13-keto and 13-methylester CO mode vibrations at 1702 and 1754 cm, respectively.
This article was published in the following journal.
Name: Biochimica et biophysica acta. Bioenergetics
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A spectroscopic technique in which a range of wavelengths is presented simultaneously with an interferometer and the spectrum is mathematically derived from the pattern thus obtained.
Analysis based on the mathematical function first formulated by Jean-Baptiste-Joseph Fourier in 1807. The function, known as the Fourier transform, describes the sinusoidal pattern of any fluctuating pattern in the physical world in terms of its amplitude and its phase. It has broad applications in biomedicine, e.g., analysis of the x-ray crystallography data pivotal in identifying the double helical nature of DNA and in analysis of other molecules, including viruses, and the modified back-projection algorithm universally used in computerized tomography imaging, etc. (From Segen, The Dictionary of Modern Medicine, 1992)
That portion of the electromagnetic spectrum usually sensed as heat. Infrared wavelengths are longer than those of visible light, extending into the microwave frequencies. They are used therapeutically as heat, and also to warm food in restaurants.
An optical source that emits photons in a coherent beam. Light Amplification by Stimulated Emission of Radiation (LASER) is brought about using devices that transform light of varying frequencies into a single intense, nearly nondivergent beam of monochromatic radiation. Lasers operate in the infrared, visible, ultraviolet, or X-ray regions of the spectrum.
A noninvasive technique that uses the differential absorption properties of hemoglobin and myoglobin to evaluate tissue oxygenation and indirectly can measure regional hemodynamics and blood flow. Near-infrared light (NIR) can propagate through tissues and at particular wavelengths is differentially absorbed by oxygenated vs. deoxygenated forms of hemoglobin and myoglobin. Illumination of intact tissue with NIR allows qualitative assessment of changes in the tissue concentration of these molecules. The analysis is also used to determine body composition.