Resonance Raman technique

From a practical standpoint, the use of the glancing angle X-ray method, while powerful, requires a synchrotron source and therefore, due to the constraints of beam time, is necessarily limited in the number of systems that can be studied in a given time period. Of the optical methods listed, the fluorescence and resonance Raman techniques directly measure spectra of an embedded... 

However, the determination of the vapor-complex vibrational frequencies may be achieved by (1) careful examination of the spectra of the reacting gases In separate cells and then comparing the spectra with those from cells containing the vapor mixture and (2) enhancement of the Raman band Intensities of the complex(es) by the use of resonance Raman techniques ( ). The results reported In this paper have been obtained by these methods. 

By resonance Raman techniques, the O—O stretch is observed at 744 cm in oxyhemocycanin and at 844 cm in oxyhemerythrin. Dioxygen is therefore coordinated as peroxo species. By use of unsymmetrically labeled dioxygen, — O, it was established that dioxygen coordinates symmetrically 4 ... 

The kinetics of the photoisomerization of bilirubin has been studied because of the relevance to phototherapy. The fluorescence of bilirubin increases on binding to human serum albumin. This and other primary photoprocesses have been investigated by picosecond spectroscopy. Karvaly has put forward a new photochemical mechanism for energy conversion in bacteriorhodopsin. An extensive review of the photophysics of light transduction in rhodopsin and bacteriorhodopsin has been made by Birge. The dynamics of cis-trans isomerization in rhodopsin has been analysed by INDO-CISD molecular orbital theory. Similar calculations on polyenes and cyanine dyes have also been reported. A new picosecond resonance Raman technique shows that a distorted... 

As of now, three technical problems stand in the way of a universal application of resonance Raman techniques. The first is the absence of a properly tunable strong monochromatic light source in part of the visible and near ultraviolet spectrum. The second is the difficulty of separating unrelaxed Raman emission from the much more intense relaxed emission in strongly... 

Of the many biological systems studied by resonance Raman techniques (for a review, see Warshel, 1977), we select two for closer scrutiny. These systems, based on long polyene chains and the porphyrin ring, respectively, are characterized by accessible visible absorption bands, which moreover lead to population of excited states that are of biological interest. 

Carboxypeptidase.— The resonance Raman technique has been used to study the microenvironment of azotyrosyl-248 in carboxypeptidase A (CPA) which has been modified with diazotized /j-arsanilic acid the co-ordination number of the zinc is thought to be five (17). Steady-state kinetic studies on both CPA and carboxypeptidase B (CPB) have revealed significant differences between the activities of the enzymes in solution and their activities in the crystalline state, thus reinforcing the significance of the spectral results (reported in Vol. 5, p. 287) with solid and aqueous arsanolazot)nosyl-248 CPA. 

A problem unique to Raman spectroscopy is the fact that most polymers fluoresce strongly when exposed to laser radiation. This problem can be reduced by using Fourier transform and resonance Raman techniques. Because of this and other difficulties associated with Raman spectroscopy, the quality of Raman spectra of polymers is typically less than that of IR spectra. Therefore, it is not surprising that a quick search of the literature reveals many more quantitative studies of polymers using IR than using Raman. 

Both ordinary and resonance Raman techniques have been used to characterize a diverse array of biological systems, from proteins and amino acids, lipids and fatty acids, and carbohydrates to phenolic substances, terpenoids, alkaloids, and polyacefylenes [112]. It is a nondestructive technique, which when coupled with microscopy can be very useful for qualitative and quantitative analyses. 

Resonance enhancement can be used to remove fluorescence by making the Raman signal much more intense than the fluorescence signal. The UV-resonance Raman method can be used to enhance the Raman signal above the fluorescence signal if the sample has the proper electronic structure for resonance enhancement and if the proper UV frequency source is available. The resonance Raman technique is discussed in the section Resonance Raman Spectroscopy (p. 229) in this chapter. 

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