Fluorescence amines

Chloro-7-nitrobenz-2,l,3-oxadiazole (NBD-C1) reacts with primary and secondary aliphatic amines to produce intensely fluorescent derivatives. Although anilines, phenols and thiols react with NBD-C1, they produce derivatives which do not fluoresce or which are only weakly fluorescent. This limits the types of compounds which can be analyzed with this reagent and thus makes the technique more selective. This selectivity is desirable in trace analysis because of a lower degree of interference from co-extractives. The general reaction scheme for formation of the fluorescent amine derivatives is shown in Fig.4.50. 

Transglutaminase catalyzes cross-linking between peptide chains in fibrin clots, the cornihed envelope of epidermal cells, and the vaginal plug from seminal plasma in rodents. Glutaminyl residues serve as acyl donors to peptide-bound lysine. This assay makes use of a small synthetic peptide, benzyloxycarbonyl-L-Gln-Gly, and fluorescent amine monodansylcadaverine as substrates. 

Thiol addition enhances the emission properties of already highly fluorescent amine-capped CdSe/ZnS core-shell QDs... 

A more qualitative estimate of endosome pH can be obtained by monitoring the distribution of a permeant, fluorescent amine such as 9-aminoacridine or acridine orange whose fluorescence varies with concentration. Such amines acaimulate in acid compartments because the protonated form of the dye is much less membrane permeant than the free base. Indeed, if the latter equilibrates readily across membranes then the pH within the vesicle i.s given by the relationship (1.5) ... 

Attaching of fluorescent probes to PLP has also been used to determine PLP. Chauhan and Dakshinamurti employed reductive amination of PLP with methyl anthranilate and sodium cyanoborohydride to form a highly fluorescent amine (83). Durko et al. (54) prepared diphenyl-isobenzofurane derivatives of Be vitamers to enable fluorometric measurement of vitamin Be. However, the use of fluorescent probes are generally not suitable for routine analytical work, mainly because the unreacted fluorescent probe may interfere in Be vitamer quantification (83). 

Browning Reactions. The fluorescent components formed in the browning reaction (8) of peroxidized phosphatidylethanolamine are produced mainly by interaction of the amine group of PE and saturated aldehydes produced through the decomposition of fatty acid hydroperoxides. 

Another fluorescent pigment class (23) is based on a urethane-type resin the primary raw materials are isocyanates, amines, and hydroxy compounds. 

Derivatization is useful for detection of compounds such as amino acids and amines that lack easily detectable groups. For similar reasons, saccharides, as a class of compound, ehcit much interest. Two derivatization schemes have been reported using benzamide (61) and FMOC—hydrazine (62) to produce fluorescent products. 

A new cyanide dye for derivatizing thiols has been reported (65). This thiol label can be used with a visible diode laser and provide a detection limit of 8 X 10 M of the tested thiol. A highly sensitive laser-induced fluorescence detector for analysis of biogenic amines has been developed that employs a He—Cd laser (66). The amines are derivatized by naphthalenedicarboxaldehyde in the presence of cyanide ion to produce a cyanobenz[ isoindole which absorbs radiation at the output of He—Cd laser (441.6 nm). Optimization of the detection system yielded a detection limit of 2 x 10 M. 

Primary and secondary amines, amino acids and phenols react In the case of long-wavelength UV light (A = 365 nm) the DANS amides fluoresce yellow-green, while amines that have reacted at a phenolic OH group have an intense yellow to yellow-orange fluorescence The detection hmit for DANS amides is ca 10 mol [86]... 

In the case of substances whose structures are pH-dependent (e.g. phenols, carboxylic and sulfonic acids, amines etc.) it is possible to produce fluorescences or make them disappear by the deliberate manipulation of the pH [213] (Table 20). Shifts of the positions of the absorption and emission bands have also been reported. This is particularly to be observed in the case of modified silica gels, some of which are markedly acidic or basic in reaction (Table 25). 

Dimethylaminocinnamaldehyde reacts with primary amines to form colored or fluorescent Schiff s bases (I). Pyrroles react with the reagent to form colored or fluorescent condensation products (II) ... 

The DOOB reagent, which is formed by reaction of diphenylboric anhydride with salicylaldehyde, yields fluorescent reaction products with primary amines [1]. 

Fluorescamine reacts directly with primary amines to form fluorescent products. Secondary amines yield nonfluorescent derivatives which can be transformed into fluorescent products by a further reaction with primary amines. 

In the presence of 2-mercaptoethanol o-phthalaldehyde reacts with primary amines to yield fluorescent isoindole derivatives [20] ... 

Vanillin reacts with primary amines in weakly basic media to form fluorescent or colored Schiff s bases whereby colored phenolates are also produced at the same time. 

This order agrees with that of quenching constant (Aqr) vaiues of the fluorescence of amines by AN. That is, the easier the reaction between an excited aromatic tertiary amine and the ground state AN, the faster the initiation. 

To activate 1-2 mg of panal with a primary amine, 1 ml of 2-3 M primary amine hydrochloride (pH 1.2, with HC1), and 2-3 mg of CTAB are added, and the mixture is incubated at 45° C for 2-5 days. The product is dark orange and fluoresces yellow. 

An excellent discussion on derivatization techniques has been given by Lawrence (17) including a detailed discussion on pre-column derivatization (18) and post-column derivatization (19). Probably, the more popular procedures are those that produce fluorescing derivatives to improve detector sensitivity. One of the more commonly used reagents is dansyl chloride (20), 5-dimethylamino-naphthalene-1-sulphonyl chloride (sometimes called DNS-chloride or DNS-C1). The reagent reacts with phenols and primary and secondary amines under slightly basic conditions forming sulphonate esters or sulphonamides. 

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