Reaction-Induced FT-IR Spectroscopic Studies of Biological Energy Conversion in Oxygenic Photosynthesis and Transport

Abstract

While membrane-associated proteins make up a substantial percentage of total cellular proteins, a much smaller fraction of known X-ray and NMR protein structures are derived from membrane proteins. Alternative approaches to understanding structure, function, and mechanism in membrane-associated enzymes are clearly needed. Vibrational FT-IR spectroscopy offers a method by which high-resolution structural and dynamic information can be obtained about this class of proteins. Reaction-induced FT-IR spectroscopy is an implementation of vibrational spectroscopy, in which the difference spectrum associated with a perturbative stimulus is recorded. This approach simplifies the spectrum and monitors the structural changes directly involved in the functional transition. In this article, we describe reaction-induced FT-IR studies of the photosynthetic and transport proteins, photosystem II, photosystem I, and lactose permease. In oxygenic plant photosynthesis, photosystem II and I convert light energy to chemical energy. In secondary active transport, the permease converts an electrochemical gradient into the energy required to move lactose into the cell. Reaction-induced FT-IR spectra acquired from these proteins can identify intermediates in the reaction mechanism. Vibrational bands in spectra acquired from photosystem II, photosystem I, and the permease are assigned by a combination of site-directed mutagenesis, isotopic labeling, and kinetic techniques. This article summarizes our recent progress in the study of photosynthetic and transport proteins with reaction-induced FT-IR spectroscopy.

Disparity in Allosteric Interactions of Monastrol with Eg5 in the Presence of ADP and ATP: A Difference FT-IR Investigation

“…Negative bands at 1525 and 1344 cm -1 have been previously assigned to the symmetric and antisymmetric stretching vibrations of the disappearing NO 2 group (16,18). This is confirmed by use of 15 N-caged ATP ( Figure 2B, solid line); this photolysis spectrum has spectral shifts (shaded negative lines) that arise from the isotopic substitution of the nitrophenylethyl moiety. The negative antisymmetric and symmetric NO 2 vibrations of caged ATP are downshifted by 27 and 21 cm -1 , respectively.…”

Exploring the Effect of Operational Factors and Characterization Imperative to the Synthesis of Silver Nanoparticles

“…This spectroscopy method is employ to detect and distinguish small absorption bands (changes on the order of 10 À3 ) of functional group covalently grafted onto silver or functionally active points that is characteristics to AgNPs. This method has the ability to give precision, it is easily reproducible and also a favorable signal-to-noise ratio [39][40][41]. One of the major advantage of FTIR spectrometers to other methods of characterization of AgNPs is that, it is a non-invasive technique, data are collected rapidly data, signals are strong and bold, large signal-to-noise ratio, and very little sample is heat-up [42].…”

Some recent contributions of FTIR difference spectroscopy to the study of cytochrome oxidase1

“…If the process is a reversible photo‐cycle, then the changes in the FTIR spectrum can be time‐resolved by repetitive flashing and signal averaging. Much of the technical development of FTIR as applied to biochemical problems has involved photo‐reactive systems, in particular bacteriorhodopsin [1,15–17] and the photosynthetic reaction center [18,19]. Cytochrome oxidase can be reduced in situ by photoreducing agents [20] or oxidized using ‘caged O 2 ’ [4,20].…”