Dendrimer chromatography

As for conventional linear polymers, gel permeation chromatography (GPC) can be used to find information on the composition of dendrimers, including their polydispersities. Obtaining standards of known relative molar mass and polydispersity is a problem with dendrimers, so the approach that has been taken most often is to use polystyrene standards, as described in Chapter 6. 

Wrodnigg TM, Eder B (2001) The Amadori and Heyns Rearrangements Landmarks in the History of Carbohydrate Chemistry or Unrecognized Synthetic Opportunities 2/5 115 -175 Wyttenbach T, Bowers MT (2003) Gas-Phase Confirmations The Ion Mobility/Ion Chromatography Method. 225 201 -226 Yamaguchi H, Harada A (2003) Antibody Dendrimers. 228 237-258... 

The reaction of the first-generation dendron 29 with the core, which is a trin-uclear platinum complex (30) bridged by 1,3,5-triethynylmesitylene, in a molar ratio of 3 1 resulted in the formation of the first-generation dendrimer (31). Since the reaction proceeded quantitatively and no side products were observed, the first-generation dendrimer was easily isolated by alumina column chromatography. 

Solvatochromic probes have been used for a variety of applications like the study polarity of pure and mixed solvents [99], and the retention behavior in reverse-phase liquid chromatography [100] among other applications. Frechet et al. used 4-(N-methylamino)-l-nitrobenzene (p-MANB), as the chromophore, to probe the microenvironment of polyaromatic ether based dendrimers [101]. 

Attached to the periphery of a lst-generation dendrimer, Ti(OCHMe2)2-com-plexes of the six TADDOL moieties in 84 catalyze - in homogeneous solution -the enantioselective addition of diethylzinc to benzaldehyde with about the same selectivity ((S) (R) 97 3) as do six monomeric TADDOL units [105],but, with a molecular weight of only 3833 Da, dendrimer 84 had to be separated by column chromatography rather than by ultrafiltration methods. 

Purify the derivatized dendrimer using gel filtration (size exclusion chromatography) on a desalting column or through use of ultrafiltration spin-tubes (for G-4 and above). For smaller dendrimers, the derivatives may be purified by repeated precipitation from a meth-anolic solution by addition of ethyl acetate, dioxane, or benzene. The SPDP-dendrimer may be dried by lyophilization (if in water or buffer) or by solvent evaporation in vacuo (if the precipitation method was used). 

Purify the conjugate from unreacted protein or unreacted dendrimer using gel filtration chromatography with a matrix having an exclusion limit appropriate to accommodate the size of the molecules being separated (i.e., a HiPrep 16/60 column packed with Sephacryl S-200 HR, GE Healthcare). 

Purify the modified dendrimer away from reactants and reaction by-products using dialysis or size exclusion chromatography. 

Purify the biotinylated dendrimer by diluting it with an equal volume of water and then using dialysis, ultrafiltration, or size exclusion chromatography. 

Purify the biotin-dendrimer using size exclusion chromatography on a desalting matrix or by use of ultrafiltration (e.g., centrifugal concentrators). 

Purify the DTPA-dendrimer using dialysis, size exclusion chromatography, or spin-tube concentrators having a molecular weight cutoff of 5,000 Daltons. 

The monodispersed nature of dendrimers has been verified extensively by mass spectroscopy, size exclusion chromatography, gel electrophoresis and electron microscopy (TEM). As is always the case, the level of monodispersity is determined by the skill of the synthetic chemist, as well as the isolation/purification methods utilized. 

The earliest work on dendrimer characterization was concerned with aspects of the organic chemistry - did the proposed chemical reaction take place without side reactions and what was the conversion Since near-100% conversion and near-perfect removal of excess reactants is required for making pure dendrimer, common methods of spectroscopy and chromatography can be used to verify the structure. In a wide variety of dendrimer chemistries, nearly perfect structures have been produced, at least for earlier generations wherein the techniques are more quantitative. 

B., 37, 362 (1995). The authors claimed that acetone solutions (5, 10 and 20%, specifically) of a sample that had gel permeation chromatography retention time close to that of a linear polystyrene of 1.1 x 106 molecular mass, had four decades lower viscosity than the corresponding solutions of flexible-chain linear poly(butyl methacrylate). However, in our opinion, neither the examined sample was characterized satisfactorily enough to be referred to as a dendrimer, nor the rheology was described sufficiently enough to draw any conclusions about the solution s flow behavior. Therefore, we refer to this paper here only for reasons of curiosity. 

It should be noted that discrepancies amidst available data may result from different methods of determination. For example, selected hydrodynamic radii of PAMAM dendrimers of Table 14.1 were obtained by two different experimental methods for generations 1 through 4 by dilute solution viscometry, while for generations 5 through 10 by size exclusion chromatography. 

Further characterization of the dendrimer-coupled protein complexes was studied by hydrophobic interaction chromatography carried out by purification over an octyl-Sepharose column. The products obtained by reaction of SIAB with ALP and its complex with third-generation dendrimer, ALP-E3, were... 

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