Fluorescent compounds, chemical structures

Both compounds were non-fluorescent. Compound KM-1 was similar to PMs in the absorption maximum (A.max 488 nm) but not in the spectral shape, whereas KM-2 was similar to PMs in the spectral shape but not in the absorption maximum at 515 nm (Fig. 9.10). The chemical structures of KM-1 and KM-2 have been determined by high-resolution mass spectrometry and NMR spectrometry (Fig. 9.11 Stojanovic, 1995). 

Balaiah V, Seshadri TR, Venkateswarlu V (1942) Visible fluorescence and chemical constitution of compounds of the benzopyrone group. Part III. Further study of structural influences in coumarins. Proc Ind Acad Sci 16A 68-82... 

In the last twenty years, many of the developed and validated high performance liquid chromatography methods with conventional diode array or fluorescence detectors (DAD, FLD) were improved and substituted by new hyphenation with mass spectrometric instrumentation and/or NMR, especially for the analyses of raw materials derived from Natural sources. The main goal of this coupling is achieved by improvement of selectivity and sensitivity of new instrumental configurations [7], Furthermore, with these configurations it is possible to obtain, in only one analysis, the complete chemical structure elucidation, identification and quantification of targeted compounds. 

A prevailing problem with neuroactive steroid analysis by HPLC is the lack of sufficient chromaphores or fluorophores within their chemical structures to allow suitable spectrophotometric end-point detection such as with UV/VIS or fluorescence with adequate sensitivity. The multitude of structural isomers of the metabolites also decreases the applicability of RP-HPLC since the chromatographic profiles become very complex with co-eluting peaks. Due to these inherent problems, it is often necessary to derivatize this group of compounds prior to chromatographic separation and suitable end-point detection to allow their direct determination at physiological concentrations. 

An additional piece of information can be obtained by studying a synthetic compound derived from the GFP chromophore (1-28) fluorescing at room temperature. In Fig. 3a we show the chemical structure of the compound that we studied in dioxan solution by pump-probe spectroscopy. If we look at the differential transmission spectra displayed in Fig. 3b, we observed two important features a stimulated emission centered at 508 nm and a huge and broad induced absorption band (580-700 nm). Both contributions appear within our temporal resolution and display a linear behavior as a function of the pump intensity in the low fluences limit (<1 mJ/cm2). We note that the stimulated emission red shifts with two characteristic time-scales (500 fs and 10 ps) as expected in the case of solvation dynamics. We conclude that in the absence of ESPT this chromophore has the same qualitative dynamical behavior that we attribute to the relaxed anionic form. 

Electronic Structure. Measurements of paramagnetic susceptibility, paramagnetic resonance, light absorption, fluorescence, and crystal structure, in addition to a consideration of chemical and other properties, have provided a great deal of information about the electronic configuration of the aqueous actinide ions in which the electrons arc in the 5/ shell. There are exceptions, such as U2S3, and subnormal compounds, such as TI12S3, where 6d electrons are present. 

Thus far, only several fluorescent scaffolds have been studied by the diversity-oriented approach and broader chemical space could be achieved for introducing higher diversity. Even more, there are other fluorescent dye scaffolds remain untouched yet. As more fluorescent compounds are synthesized systematically, richer information for structure-photophysical property relationships should be available, which in turn could help for the designing of target-specific fluorescence sensors. 

Riboflavin was first observed in 1879 by the English chemist Alexander Wynter Blyth (1844-1921) who noticed a compound in cow s milk that glowed with a yellow fluorescence when exposed to light. Blyth called the compound lachtochrome (lachto- = milk and -chrome = color), but was unable to determine its chemical composition or its chemical properties. In fact, it was not until the 1930s that the chemical nature of the compound was determined. The Swiss chemist Paul Karrer (1889-1971) and the Austrian-German chemist Richard Kuhn (1900-1967) independently determined the chemical structure of riboflavin and first... 

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