Chromophores aromatic

The pyrene-like aromatic chromophore of BaPDE is characterized by a prominent and characteristic absorption spectrum in the A 310-360 nm spectral region, and a fluorescence emission in the X 370-460 nm range. These properties are sensitive to the local microenvironment of the pyrenyl chromophore, and spectroscopic techniques are thus useful in studies of the structures of the DNA adducts and in monitoring the reaction pathways of BaPDE and its hydrolysis products in DNA solutions. 

Figure 1 Jablonskii diagram illustrating the energy levels and photophysical processes for an aromatic chromophore (ISC = inter-system crossing IC = internal conversion).

DeAngelis, G.G. and Wildman, W.C., Circular dichroism studies. 1. A quadrant rule for the optically active aromatic chromophore in rigid polycyclic systems. Tetrahedron, 25, 5099, 1969. 

D. A. Chignell and W. B. Gratzer, Solvent effects on aromatic chromophores and their relation to ultraviolet difference spectra of proteins, J. Phys. Chem. 72, 2934-2941 (1968). 

Subsequently, the application of a quadrant rule developed for compounds bearing an asymmetric center adjacent to the aromatic chromophore by means of considerations of the CD and ORD spectra of products of established absolute configuration to the alkaloids of the 5,10b-ethanophenanthridine series led to conclusions on their absolute stereochemistry at variance with those mentioned above 42). 

From the optical and chiroptical properties of [2.2]metacyclophanes, compared with those of [10]paracyclophanes40), it was concluded that in the former an inherently achiral aromatic chromophore perturbed by vibrations is presumably responsible 

Morishima et al. [30, 50-54, 73-76] have made extensive investigations on photoinduced ET, using polycyclic aromatic chromophores covalently attached to polyelectrolytes. They were the first to show that the polyeletrolyte molecular surface provides an unusual microenvironment which greatly changes the rate of photoinduced ET and the fate of the charged photoproducts. 

In addition to red-shifted spectra and low rotational amplitude, Ehrlich ascites plasma membranes exhibit Cotton effects in the region of aromatic chromophores, 250-300 m/ (89). Similar behavior has been observed in other proteins, such as carbonic anhydrase (34) and lysozyme (58), and disappear upon denaturation. Ehrlich ascites plasma mem- 

The UV and CD curves of optically active (S)-9-hydroxy-6-methyl-3,4-dihydro-2//-pyrido[2,1 -6] [1,3]thiazinium-4-carboxylate were measured in 1 N hydrochloric acid and in 1 N sodium hydroxide solutions (73ACS1059). The CD spectrum in acid solution exhibits positive bands at 212 and 233 nm and negative bands at 257 and 345 nm, and UV maxima were found at 211, 239, and 342 nm. The two latter bands are associated with the aromatic chromophore. In alkaline solution a bathochromic shift occurred, and the 

Practical Considerations. Typical absorption assay methods utilize ultraviolet (UV) or visible (vis) wavelengths. With most spectrophotometers, the measured absorbance should be less than 1.2 to obtain a strictly linear relationship (/.c., to obey the Beer-Lambert Law). Nonlinear A versus c plots can result from micelle formation, sample turbidity, the presence of stray light (see below), bubble formation, stacking of aromatic chromophores, and even the presence of fine cotton strands from tissue used to clean the faces of cuvettes. One is well advised to confirm the linearity of absorbance with respect to product (or substrate) concentration under the exact assay conditions to be employed in 

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