Dansyl groups

Righetti and co-workers [11] were one of the first to demonstrate the utility of classical isoelectric focusing for the chiral separation of small molecules in a slab gel configuration. In their system, dansylated amino acids were resolved enan-tiomerically through complexation with (i-cyclodextrin. Preferential complexation between the cyclodextrin and the derivatized amino acid induced as much as a 0.1 pH unit difference in the pK s of the dansyl group. 

Reports on the use of fluorescent derivatives abound (5). Some reagents have become widely used. The dansyl group is probably the most thoroughly studied. Dansyl chloride has been widely used as a fluorescent derivatizing reagent for HPLC (6,7). It reacts readily with primary and secondary amino groups (7) and with phenols (8), but forms derivatives of alcohols very slowly (9). The lower detection limit for dansyl derivatives of aliphatic amines is in the range of 300 femtomoles per injection. 

The validity of the Forster theory was tested and confirmed in a number of model studies with compounds that contained a donor and an acceptor separated by well-defined rigid spacers. This work has been reviewed 5] In a classical study, a naphthyl group (donor) was attached to the C-terminal and a dansyl group (acceptor) to the N-terminal of poly-L-proline oligomers (1-12 proline residues) 61 These proline oligomers assume a trans helical conformation in ethanol and thus represent spacers of well-defined length (12-46 A). A continuous decrease in the transfer efficiency from 100% at a donor-acceptor separation of... 

Figure 23-15 Efficiency of energy transfer as a function of distance between a-naphthyl and dansyl groups at the ends of a polyprolyl "rod" (L-prolyl)n. The observed efficiencies of transfer for n = 1 to 12 are shown as points. The solid line corresponds toanr6 distance dependence. From L. Stryer.150...

Fluorescence energy transfer, which can be observed when the absorbance spectrum of a fluorescent probe such as the dansyl group... 

A side-chain NH-Boc group of perhydropyrido[2,l-c][l,4]oxazin-3-one 215 was changed for a NH-dansyl group by treatment first in a 30 1 mixture of MeOH and AcCl at room temperature for 20 h, then the residue of the evaporated reaction mixture was dissolved in DMF and was reacted with dansyl chloride in the presence of NEt3 at room temperature for 4 h (08BMC10216). 

I. 1-anthryl-l -naphthyl alkanes. II. Nicotinamide-adenine-dinucleotide (reduced) NADH. IFF Oligomers of poly-L-proline with a-naphthyl group as energy donor and dansyl group as energy acceptor. III. p-methoxy benzene and flourene chromophere in norbornadiene-spirocyio-propane frame. V and VI. Anthrone and naphthalene chromphore in spiro-compounds. 

Like PAMAM dendrimers, polylysine dendrimers are largely characterised by amide bonds. They attracted interest as potential therapeutic agents for use in boron neutron capture therapy and in magnetic resonance imaging (MRI) (see Chapter 8), since dendritic polylysines apparently have a lower toxicity than their linear counterparts. The polylysine shown in Fig. 4.10 with a total of 80 terminal boron atoms in the carborane units and a dansyl group was designed specifically for boron neutron capture therapy [20]. 

The dendrimer of mixed POPAM/Frechet type shown in Fig. 5.5 formally bears several types of fluorophores in three shells naphthyl units on the periphery two layers with dimethoxybenzene character further inside and finally the strongly fluorescing dansyl groups - adding up to a total of 64 luminophoric moieties. Incident UV radiation interacts first with the naphthyl groups, which... 

Fig. 5.8 Quen ching of the fluorescence of the dendrimer host in the presence of eosin (as guest) by energy transfer starting from the photoactive dansyl groups. The guest...

Reinhout et al. prepared a (3-CD-calix[4]arene couple 64 in which a dansyl unit is attached to calix[4]arene and oriented toward the secondary face of (3-CD [56], This compound exhibits a fluorescence peak at 538 nm, and its intensity was hardly influenced by guest molecules. The examination of molecular models suggested a very strong self-inclusion of the dansyl group into the CD cavity. 

Consistent with the principles outlined in Chapter 1, strong hydrogen-bonded association may be achieved by multiple complementary interactions, as in the barbiturate-appended porphyrin system shown in 11.21 (cf. molecular rosettes, Section 10.6.4). This receptor binds a complementary dansyl (dimethylaminonapthalene-sulfonyl) group with an association constant in excess of 106 M-1. In this case, electron transfer is from the photoabsorbing dansyl group to the porphyrin acceptor quenching is almost total, suggesting very fast electron transfer relative to the rate of fluorescence.12... 

Later on, Aoki et al. [5] described a similar ligand, bearing an anthrylmethylamino group instead of the dansyl group (Scheme 5). 

Upon pH-dependent fluorescence titration, the fluorescence of the dansyl group increased 8.5 times as the pH value increased. The quantum yield at pH 11.0 was 6 times higher than at pH 7.4. The fluorescence emission was greatly enhanced by the presence of yttrium(III) and lanthanum(III) ion (8.6 times and 3.8 times, respectively). On the other hand, the fluorescence was not affected by the presence of a great many similar cations. This means the ligand was a selective probe for Y31 and La3+ working in aqueous solutions. 

Aoki, S., Kawatani, H., Goto, T., Kimura, E., Shiro, M. A double-functionalized cyclen with carbamoyl and dansyl groups (cyclen = 1,4,7,10-tetraazacyclododecane) A selective fluorescent probe for Y3+ and... 

Figure 16.2 Fluorescence assay with chemically modified gypsy moth PBP. (A) Attachment of a dansyl group to PBP. (B) Fluorescence spectrum of modified PBP saturated with 6b and without 6b. (C) Titration of dansylated PBP with 6b.

Fig. 9 Crystal structures of two separate crystals of P450CAM bound to D-8-Ad at 1.45 A (left) and 2.2 A (right) resolution. In the higher resolution structure the dansyl group is found to make an interaction with Pro 187 in the P/G loop while in the other crystal the dansyl is packed in a similar way against Pro89 of the B helix...

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