Complexes with Amino Acids

Uchegbu and coworkers have studied the complexation and delivery of DNA using a unique poly(amino acid)-based polymer vesicle. A polymer of either poly (L-lysine) or poly(L-omithine) was functionalized with methoxy-poly(ethylene glycol) (mPEG) and hydrophobic palmitic acid chains to synthesize an amphiphilic triblock of either mPEG-6-poly(L-lysine)-6-palmitoyl or mPEG-Z>-poly(L-omithine)-6-palmitoyl. Vesicles formed from these polymers were complexed with DNA and showed improved transfection in vitro over poly(amino acid) complexed with DNA or DNA alone [82]. 

Table 12 Reaction selectivity kolk ) of various protonated /3-CD/amino acid complexes with 1-propylamine...

Other chiral phases include those based on proteins, cellulose triacetate, amino acids complexed with copper and chiral crown ethers. 

Wilchek, M., Ariely, S., and Patchornik, A., The reaction of asparagine, glutamine, and derivatives with phosgene, J. Org. Chem. 33, 1258-1259, 1968 Hamilton, R.D. and Lyman, D.J., Preparation of A-carboxy-a-amino acid anhydrides by the reaction of copper(II)-amino acid complexes with phosgene, J. Org. Chem. 34, 243-244,1969 Pohl, L.R., Bhooshan, B.,... 

The ORD spectra of several L-a-amino acid complexes with Cr(III) (Tsangaris, 1970) show strong negative Cotton effects in the 536-508-nm range (d-d transition). The only exception is the hydroxyproline complex, which gives rise to a positive Cotton effect. Additional Cotton effects are observed in the 598-584-nm range and in the neighborhood of 400 nm. All complexes have two absorption bands at 572-530 and 412-399 nm. The CD spectral characteristics of a number of amino acid complexes of Cr(III) have also been described (Oki, 1977 Oki and Takahashi, 1977). 

Amino acids can also be determined by amperometric detection with a copper electrode under neutral or alkaline conditions. This method is very selective, with the working electrode potential set at only -1-0.10 mV versus Ag/AgCl. In this detection method, amino acids complex with Cu " " ions present on the electrode surface, producing a response that is proportional to the concentration of the amino acid. Detection limits are between 10 and 100 pmol and can be improved if microbore chromatography is employed. The slower flow rates utilized with microbore chromatography columns allow more time for complexation to take place, thus improving the detection limits. 

Functionalized polystyrene resins have been employed for ligand-exchange chromatography of racemates of amino-acids. > The resins carry asymmetric sorbent groups, for example of oc-amino-acids complexed with Cu > or Ni , capable of selective formation of mixed ligands with amino-acid enantiomers. Structures (10) and (11) are examples of reactive sites bonded to polystyrene resins for this purpose. The second type of structure is produced by direct... 

Two different dinuclear m-acetato-m-benzophenone iminato palladium complexes were prepared as a variety of different solvates. The dynamics of these were studied by both C CP MAS and static NMR spectroscopy. " Single-crystal X-ray diffraction and solid-state Pb NMR spectroscopic experiments have been conducted on four lead amino acid complexes with nitrato or perchlorato counterions, namely neutral isoleucine, deprotonated leucine, monodeprotonated aspartic acid, and neutral valine. " ... 

Mascagni, P., Hyde, C. B., Charalambous, M. A., and Welham, K. J. (1987) The use of crown ethers in peptide chemistry. Part 1. Syntheses of amino acid complexes with the cyclic polyether 18-crown-6 and their oligomerisation in dicylohexylcarbodi-imide-containing solutions. J.Chem. Soc. Perkin Trans. 2, 323-327. 

Such an approach applied to a number of amino acids complexed with Mn(II) has shown that the dipolar contribution to relaxation is not predominant in most cases (Esperon and Martin, 1976). Temperature- and frequency-dependence studies are required to determine if any limitation is caused by an intermediate exchange rate or scalar contributions. measurements appear to provide better estimates of distances than do T2 measurements when scalar contributions are present in the relaxation mechanism. 

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