High resolution luminescence spectrometer. 1: simultaneous recording of total luminescence and phosphorescence

A low temperature investigation of the intermediates of the photocycle of light-adapted bacteriorhodopsin. Optical absorption and fluorescence measurements

Optical absorption and emission measurements have been made on samples of light-adapted purple membrane of Halobacterium halobium at temperatures ranging from 77 K to room temperature. As a result of these experiments a set of equations is given which described thermal and photochemical reactions interrelating various intermediates of the reaction cycle of the chromophore of light-adapted bacteriorhodopsin (BR). Further some specific problems connected to these intermediates have been investigated. Thus the room temperature emission spectrum of bacteriorhodopsin has been found to exhibit a Stokes shift of 3430 cm-1 only, if low excitation intensities are used. The recently detected intermiediate P-BR can be shown to convert thermally into bacteriorhodopsin following a first-order decay with the activation energy delta E = 2.4 +/- 0.2 kcal/mol. The thermal decay of K-BR consists of two exponentials if measured on purple membrane suspensions in a mixture of H2O and glycerol (1 : 1, v/v). A simple procedure is given for trapping the intermediate L-BR at 170 K in a very pure form. M-BR is shown to consist of two species, MI-BR and MII-BR. They are characterized by similar optical absorption spectra but different thermal stability. Further the oscillator strengths corresponding to the long wavelength absorption bands of the intermediates bacteriorhodopsin, K-, L, MI- and MII-BR have been calculated. They have been discussed with respect to the question which of the corresponding absorption spectra show the characteristics of isomerism of the chromophore or simply solvatochromism.

High resolution luminescence spectrometer. 2:data treatment and corrected spectra

In Part 1 [Appl. Opt. 12, 1286 (1973)] we described the design of a high resolution luminescence spectrometer for research purposes. In this paper the computer processing of its digital output is discussed. The data treatment is based upon statistical concepts. Subroutines for wavelength calibration, dark count correction, data smoothing, and curve presentation have been developed. Corrected emission and excitation spectra may be obtained with additional calibration data, and relative quantum yields may be determined. The final luminescence spectra are plotted with their corresponding standard deviations.