Fluorescence substituents

Gel permeation chromatography of protein linear random coils in guanidinium chloride allows simultaneous resolution and molecular weight analysis of polypeptide components. Column calibration results are expressed in terms of a log M vs. Kd plot or of effective hydrodynamic radius (Re/). For linear polypeptide random coils in 6M GuHCl, Re is proportional to M0 555, and M° 555 or Re may be used interchangeably. Similarly, calibration data may be interpreted in terms of N° 555 (N is the number of amino acid residues in the polypeptide chain), probably the most appropriate calibration term provided sequence data are available for standards. Re for randomly coiled peptide heteropolymers is insensitive to amino acid residue side-chain composition, permitting incorporation of chromophoric, radioactive, and fluorescent substituents to enhance detection sensitivity. 

While E form fulgides rarely emit fluorescence unless they have fluorescent substituents, C forms often fluoresce at lower temperatures.19... 

From a supramolecular perspective, cyclodextrins offer a preformed cavity of defined size within a water-soluble macrocycle. The interaction between guest molecules, or substituents to the cyclodextrin itself, leads to some useful results. Hydrophobic fluorescent substituents will be self-included by the macrocycle in aqueous solution until they are displaced by guests with even greater affinities [6]. The act of displacement will generate a fluorescent response that lends itself to sensor applications. It is also possible to use the hydrophobic core to induce rotaxane formation. This approach has been used by many groups, for example, Liu has recently used it to prepare water-soluble gold-polypseudorotaxanes that capture fullerenes such as C60 [7]. 

Materials that exhibit both electrochromic and fluorescent properties have the advantage of multifunctionality. In order to obtain polymers presenting both properties various strategies can be adopted including (fl) the modification of an electrochromic polymer through the insertion of fluorescent substituents in the monomer, (Z>) the preparation of copolymers in which at least one of the co-monomers is fluorescent, (c) fused-aromatic rings and extended Ti-conjugation systems, and (d) by the synthesis of D-A polymers. Fig. 4. 

Besides the possibility of inserting fluorescent substituents in only one monomer unit, such as pyrrole or thiophene, it is noteworthy that suitable fluorescent groups have been appended in dimeric or trimeric monomer systems. Using this approach, Cihaner and Algi have initiated a programme aimed at the design and synthesis of photo- and electroactive polymer materials based on 2,5-di(2-thienyl)pyrroles (SNS). This system consist of thiophene and pyrrole rings interconnected by their a-positions and exhibit intense blue emission upon irradiation. They have reported the synthesis and characterisation of a series of novel fluorescent and electrochromic polymers based on N-substituted... 

According to these examples, it was shown that by the help of fluorescent substituents like naphthalene, fluorene and luminol, PSNS based polymers can exhibit both fluorescent and electrochromic properties, nonetheless examples of processable fluorescent and electrochromic polymeric materials based on SNS unit are rare. ... 

Many chemical compounds have been described in the Hterature as fluorescent, and since the 1950s intensive research has yielded many fluorescent compounds that provide a suitable whitening effect however, only a small number of these compounds have found practical uses. Collectively these materials are aromatic or heterocycHc compounds many of them contain condensed ring systems. An important feature of these compounds is the presence of an unintermpted chain of conjugated double bonds, the number of which is dependent on substituents as well as the planarity of the fluorescent part of the molecule. Almost all of these compounds ate derivatives of stilbene [588-59-0] or 4,4 -diaminostilbene biphenyl 5-membeted heterocycles such as triazoles, oxazoles, imidazoles, etc or 6-membeted heterocycles, eg, coumarins, naphthaUmide, t-triazine, etc. 

Diels-Alder reactions, 4, 842 flash vapour phase pyrolysis, 4, 846 reactions with 6-dimethylaminofuKenov, 4, 844 reactions with JV,n-diphenylnitrone, 4, 841 reactions with mesitonitrile oxide, 4, 841 structure, 4, 715, 725 synthesis, 4, 725, 767-769, 930 theoretical methods, 4, 3 tricarbonyl iron complexes, 4, 847 dipole moments, 4, 716 n-directing effect, 4, 44 2,5-disubstituted synthesis, 4, 116-117 from l,3-dithiolylium-4-olates, 6, 826 electrocyclization, 4, 748-750 electron bombardment, 4, 739 electronic deformation, 4, 722-723 electronic structure, 4, 715 electrophilic substitution, 4, 43, 44, 717-719, 751 directing effects, 4, 752-753 fluorescence spectra, 4, 735-736 fluorinated derivatives, 4, 679 H NMR, 4, 731 Friedel-Crafts acylation, 4, 777 with fused six-membered heterocyclic rings, 4, 973-1036 fused small rings structure, 4, 720-721 gas phase UV spectrum, 4, 734 H NMR, 4, 7, 728-731, 939 solvent effects, 4, 730 substituent constants, 4, 731 halo... 

An interesting application of this reaction was the use of macro-molecular anhydrides, namely, styrene-maleic anhydride or vinyl acetate-maleic anhydride copolymers in the presence of perchloric acid as catalyst, these copolymers acylate mesityl oxide or d rpnone to macromolecular pyrylium salts which, with aryl substituents, are fluorescent.No crystalline products could be obtained from succinic anhydride because of the solubility and ease of decarboxylation. 

Absorption and emission spectra of six 2-substituted imidazo[4,5-/]quinolines (R = H, Me, CH2Ph, Ph, 2-Py, R = H CH2Ph, R = Ph) were studied in various solvents. These studies revealed a solvent-independent, substituent-dependent character of the title compounds. They also exhibited bathochromic shifts in acidic and basic solutions. The phenyl group in the 2-position is in complete conjugation with the imidazoquinoline moiety. The fluorescence spectra of the compounds exhibited a solvent dependency, and, on changing to polar solvents, bathochromic shifts occur. Anomalous bathochromic shifts in water, acidic solution, and a new emission band in methanol are attributed to the protonated imidazoquinoline in the excited state. Basic solutions quench fluorescence (87IJC187). 

It would be preferable to incorporate both fluorescent and electron transport properties in the same material so as to dispense entirely with the need for electron-transport layers in LEDs. Raising the affinity of the polymer facilitates the use of metal electrodes other than calcium, thus avoiding the need to encapsulate the cathode. It has been shown computationally [76] that the presence of a cyano substituent on the aromatic ring or on the vinylene portion of PPV lowers both the HOMO and LUMO of the material. The barrier for electron injection in the material is lowered considerably as a result. However, the Wessling route is incompatible with strongly electron-withdrawing substituents, and an alternative synthetic route to this class of materials must be employed. The Knoevenagel condensation... 

Saito, R., Hirano, T., Niwa, H., and Ohashi, M. (1997). Solvent and substituent effects on the fluorescent properties of coelenteramide analogues. J. Chem. Soc., Perkin Trans. 2, pp. 1711-1716. 

Table I. Effects of Peptide Substituents on Fluorescence Quantum...

Palmatine (Scheme 1) bears the same tetracychc structure as berberine but differs in the nature of the substituents on the benzo ring being methylene dioxy for berberine and dimethoxy for palmatine. In aqueous buffer, the UV-visible spectriun of palmatine shows maxima at 232, 268, 344.5 and 420 nm. Palmatine has a weak fluorescence spectrum in the range 400-650 nm with... 

Fluorescence. - A further report on the use of naphthalene phosphorus compounds for fluorescence derivatization concerns the dependence of fluorescence on the type and position of substituents on the naphthalene rings.141 It has been found that the... 

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