Dansyl chloride -reactive

The amine-reactive 5-(dimethylamino)naphthalene-l-sulfonyl (dansyl) chloride 28 [80] and related fluorophores [81, 82], as well as the 5-((2 aminoethyl)amino) naphthalene-1-sulfonic acid (EDANS) 29, are included in the naphthalene fluorophore family. Derivatives of the latter, such as compound 30, exhibit a Lm.ix/ Lem 336/520 nm, molar absorptivity (e) of 6.1 x 103 M-1 cm-1, and a fluorescent quantum yield of 0.27 in water [83], The use of EDANS is particularly interesting in FRET experiments [84, 85]. Furthermore, 4-amino-3,6-disulfonylnaphthalimides (e.g., Lucifer yellow 31), associated to a longer absorption (Lmax 428 nm) [86] are suitable polar tracers [87]. 

Extrinsic fluorescence is used whenever the natural fluorescence of a macromolecule is inadequate for accurate fluorescence measurement. In this case, one can attach a fluorescent reporter group by using the reactive isocyanate or isothiocyanate derivatives of fluorescein or rhodamine, two intensely fluorescent molecules. One can covalently also label a protein s a- and e-amino groups with dansyl chloride (/.e., A,A-dimethylaminonaphtha-lenesulfonyl chloride). Another useful reagent is 8-ani-lino-l-naphthalenesulfonic acid (abbreviated ANS). This compound is bound noncovalently by hydrophobic interactions in aqueous solutions, ANS is only very fluorescent, but upon binding within an apolar environment, the quantum yield of ANS becomes about 100 times greater. 

Comparison with in vivo procedures Although the FDNB procedure proved to be a suitable reference method, there is no doubt that all methods should be ultimately compared to in vivo procedures. For this reason selected samples were also analyzed by plasma amino acid and digestibility methods. Preliminary results ( Table II ) show that plasma lysine results correlated very well with results for lysine digestibility and FDNB lysine ( r =0.95 ), reasonably well with those for dansyl chloride lysine, succinic anhydride reactive lysine and dye binding lysine, but poorly with total lysine. Although the absolute values were in many cases very different, it is apparent that all methods except total lysine can be used to at least indicate the extent of lysine damage. 

Hill, R.D. and Laing, R.R., Specific reaction of dansyl chloride with one lysine residue in rennin, Biochim. Biophys. Acta 132, 188-190, 1967 Chen, R.F., Huorescent protein-dye conjugates. I. Heterogeneity of sites on serum albumin labeled by dansyl chloride. Arch. Biochem. Biophys. 128, 163-175, 1968 Chen, R.F., Dansyl-labeled protein modified with dansyl chloride activity effects and fluorescence properties. Anal Biochem. 25, 412M16, 1968 Brown, C.S. and Cunningham, L.W., Reaction of reactive sulfydryl groups of creatine kinase with dansyl chloride. Biochemistry 9, 3878-3885, 1970 Hsieh, W.T. and Matthews, K.S., Lactose repressor protein modified with dansyl chloride activity effects and fluorescence properties. 

Nucleophilic substitution reactions of dansyl chloride with anilines (entry 16)128 are reported in various protic solvents. Interestingly, the Px values are in parallel with the rates, which are dependent on the dielectric constant (e)49 of the solvent as can be seen from the data presented for each solvent in the order [e k2 (xlO4 M 1 s 1 at 30 °C for X = H) px], MeOH [32.66 107 0.67], EtOH [24.55 37.7 0.55], w-PrOH [20.45 8.71 0.50], 2-PrOH [19.92 5.33 0.41], n-BuOH [17.51 3.07 0.34], MeCN [35.94 13.7 0.72]. In the aprotic solvent MeCN, the rate is somewhat slow despite the largest s and Px values. Since the reactivity changes in parallel to the selectivity, the RSP is violated, and a stepwise mechanism through an intermediate can be excluded. Solvatochromic analysis also suggested that the reaction proceeds via an associative S 2 mechanism. 

Peptide analysis, sequencing and synthesis All fluorescent dye labels with reactive groups for amine, dansyl chloride, dabsyl chloride. Fluorescent isothiocyanates. N-Terminal amino acid analysis, peptide sequencing, peptide synthesis, labeling peptides in solution, solid-phase synthesis of labeled peptides 37... 

FIGURE 2.1 Reagents for introducing a fluorophore into compounds with a complementary reactive functional group. Reagents 1 = dansyl chloride 2 = dabsyl chloride 3 = dansyl hydrazine 4 = fluorescamine 5 = 2,4-dihydro-6,7-dimethoxy-4-methyl-3-oxo-quinoxaline-2-carbonyl azide 6 = o-phthalaldehyde 7 = fluorenyhnethyloxycarbonyl chloride 8 — 4-bromome iyl-7-methoxycoumarin and 9 = 4-chloro-7-nitrobenzofurazan. 

It has an acylated NH2 terminus and so is not reactive to dansyl chloride. The yield of crude peptide averaged about 60%. 

Cellulose Sulfonates. Cellulose sulfonates are inorganic esters of cellulose and sulfonic acids in which there is a sulfur-oxygen bond formed to link the cellulose and sulfonic acid moieties. Figure 4 depicts the three most common cellulose sulfonates described in the literature, cellulose methanesulfonate (mesylate) (4), cellulose toluenesulfonate (tosylate) (5), and cellulose dansylate (6) (22-25). Cellulose tosylate is the most commonly described cellulose sulfonate in the literature. Cellulose sulfonates are typically prepared in a homogeneous process by dissolving cellulose in a dimethylacetamide/lithium chloride (DMAc/LiCl) mixture and reacting the cellulose with sulfonylchloride in the presence of triethylamine (Fig. 5) (25). Cellulose sulfonates can also be prepared in situ for use as reactive intermediates (26,27). The use of cellulose tosylate as a reactive intermediate is be discussed in more detail later in this report. 

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