Nucleobases-amino acids complexes

Lippert, Hadjiliadis and co-workers have prepared and characterized a number of ternary complexes containing ammine, amino acid or peptide, and nucleobase, for example, the complex 51 containing 1-methylcytosine and glycine [35] [36] and 52 containing 9-methylguanine and glycine [35] [36]. These complexes may be prepared either by reaction of [Pt(NH3)2(gly-./V, 0)]+ (9) with the nucleobase B (in which case the amino acid was sometimes completely displaced by the base molecules [37]), or by reaction of cA-[Pt(NH3)2(B)(H20)]2+ with the amino acid (in which case the complex with O-bound amino acid was observed initially as an intermediate [35]). 

In contrast to the amino acid, peptide, and protein conjugates, where a number of different organometallic complexes were used for labeling, DNA derivatives are by and large limited to ferrocene. This is very likely due to the attractive electrochemical properties of ferrocene. Indeed, electrochemical DNA sensors are covered in more detail in Section 1.31.5.2. Two recent reviews cover the ferrocene conjugates with nucleobases, nucleosides and nucleotides,... 

Several functional groups have been used to obtain cellulose anion exchangers [aminoethyl (AE), diethylami-noethyl (DEAE)] or cation exchangers [carboxymethyl (CM), phosphate (P)] for TLC. Polyethyleneimine (PEI) cellulose is not a chemically modified cellulose, but a complex of cellulose with PEL These cellulose exchangers are particularly useful for the separation of proteins, amino acids, enzymes, nucleobases, nucleosides, nucleotides, and nucleic acids (Table 2). 

Keywords amino acids cadmium complexes crystal structures nucleobases thiolates vitamins... 

There are numerous ways to determine experimentally pK values of chemical compounds (205). Classical methods are potentiometric titration and ultraviolet (UV) spectroscopy, among others. These techniques have been widely applied for nucleobases and also for metal-nucleobase complexes. For the extremes such as negative pK values (pK < —2) of singly or multiply protonated nucleobases, or very high pK values (pK >15) for deprotonation of exocyclic amino groups of nucleobases (C, G, A), modifications have to be employed. These include the consideration of the Hammett acidity function in superacidic solvents or solvent mixtures (206), as well as extrapolative techniques according to Bunnett-Olsen and Marziano-Cimino-Passerini to be applied in polar, aprotic solvents (45, 207). 

---