Quantitative -correlation spectroscopy

In quantitative /-correlations (Fig. 7.12), a coupling of interest is extracted from quantitative evaluation of the ratio of cross-peak to diagonal-peak intensities in an out-and-back correlation experiment between spins B and C. 

In the preparation period of the out-and-back correlation experiment, in-phase coherence Bx evolves into anti-phase coherence 2ByCz during r, a subsequent 90°X(B,C) pulse converts these two operators to Bx and 2BzCy, which evolve and give rise to a reference 

158 7 Methods for the Measurement of Angle Restraints Application to Biomacromolecules 

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A related experiment TOCSY (Total Correlation Spectroscopy) gives similar information and is relatively more sensitive than the REIAY. On the other hand, intensity of cross peak in a NOESY spectrum with a short mixing time is a measure of internuclear distance (less than 4A). It depends on the correlation time and varies as . It is positive for small molecules with short correlation time (o r <<1) and is negative for macromolecules with long correlation time (wr >>l) and goes through zero for molecules with 1 Relaxation effects should be taken into consideration for quantitative interpretation of NOE intensities, however. 

Fluorescence intensity detected with a confocal microscope for the small area of diluted solution temporally fluctuates in sync with (i) motions of solute molecules going in/out of the confocal volume, (ii) intersystem crossing in the solute, and (hi) quenching by molecular interactions. The degree of fluctuation is also dependent on the number of dye molecules in the confocal area (concentration) with an increase in the concentration of the dye, the degree of fluctuation decreases. The autocorrelation function (ACF) of the time profile of the fluorescence fluctuation provides quantitative information on the dynamics of molecules. This method of measurement is well known as fluorescence correlation spectroscopy (FCS) [8, 9]. 

In addition to the characteristic XRD patterns and photoluminescence, UV-visible and X-ray absorption spectra, another fingerprint thought to indicate lattice substitution of titanium sites was the vibrational band at 960 cm-1, which has been recorded by infrared and Raman spectroscopy (33,34). Although there is some controversy about the origin of this band, its presence is usually characteristic of a good TS-1 catalyst, although it turned out to be experimentally extremely difficult to establish quantitative correlations between the intensity of the 960 cm-1 band and the Ti content of a Ti silicate and/or its catalytic activity. 

This section is concerned with the quantitative correlation of reaction rates and equilibria of organic reactions with the structure of the reactants. We will restrict the discussion to benzene derivatives. The focus is on a remarkably simple treatment developed by L. P. Hammett in 1935, which has been tremendously influential. Hammett s correlation covers chemical reactivity, spectroscopy and other physical properties, and even the biological activity of drugs. Virtually all quantitative treatments of reactivity of organic compounds in solution start with the kinds of correlations that are discussed in this section. 

Petersen NO, Hoddelius PL, Wiseman PW, Seger O, Magnusson KE. Quantitation of membrane receptor distributions by image correlation spectroscopy concept and application. Biophys. J. 1993 65 1135-1146. 

E. Rhoades, T.F. RamlaU, W.W. Webb, D. Eliezer, Quantitation of alpha-synuclein binding to lipid vesicles using fluorescence correlation spectroscopy. Biophys. J. 90(12), 4692-4700 (2006)... 

Unlike correlation spectroscopy based on spin diffusion, the adiabatic version enables, in principle, almost full exchange of magnetization between the two spins. As a result, the entire signal intensity will reside in the cross-peaks. Violation of the adiabaticity is characterized by the appearance of a diagonal peak and can be expected to occur if the rotation sweep is too fast compared to the interaction between spins. While numerical simulations indicate possible linear dependencies of the polarization transfer coefficient on spin coupling and the rate of the sweep over a range of practical values, the validity of this assumption remains to be tested. Here we present a semi-quantitative example of a relayed polarization transfer process. 

For a number of assays, fluorescent-labeled analogues of a hgand are used. Some of those assays are of a quantitative nature, such as in fluorescence correlation spectroscopy (FCS), where the fluorescent-labeled analogue is used to determine binding kinetics (Fig. 5.5) [36]. FCS allows the direct detection of molecular interactions in solution. FCS monitors the random motion of a fluorescent molecule... 

C=0 stretch mode is quite strong in Raman or IR spectra and in some cases quantitative correlation between hydrogen bonding energy and C=0 stretch frequency can be determined [8, 9]. Thus, it is ideally suited for studies of the substrate C=0 bond activation in the enzyme complexes. Two dehydrogenases, LDH and LADH, have been studied in detail by vibrational spectroscopy. 

A set of experiments on TS-1 samples with variable Ti content, synthesized and treated in a reproducible way, has allowed to proof the quantitative correlation between Ti content and the intensity of the 960cm" IR feature. The linear correlation between the intensity of the 960cm band and x has been also confirmed by Raman spectroscopy. 

The output of individual flagellar motors in E. coli was measured as a function of the intracellular concentration of the chemotactic signaling protein. The concentration of this molecule, fused to GFP, was monitored with fluorescence correlation spectroscopy. Motors from different bacteria exhibited an identical steep input-output relation, suggesting that they actively contribute to signal amplification in chemotaxis. These experimental studies can be extended to quantitative in vivo studies of other biochemical networks. ... 

Foldes-Papp, Z and Rigler, R, Quantitative two-color fluorescence cross-correlation spectroscopy in the analysis of polymerase chain reaction. Biological Chemistry3S2 (2001) 473-478. 

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