Adenine behavioral changes

Surface-enhanced near-infrared Raman spectroscopy has been utilized to study the behavior of nicotinamide adenine dinucleotide on a gold electrode [303]. It has been found that either adenine or nicotinamide moiety changes its adsorption states during potential scanning. 

The acid-base behavior of nucleotides is dominated by the acidity of the nucleic bases and the phosphate groups (Table 8.5.2). Some remarkable changes in pk values are observed when going from hydrophobic to hydrophilic derivatives (e.g., it is more difficult to protonate the NH2 of adenosine than that of adenine), the acidity of the anomeric pentose proton (typical pk, values 12-13), and the pk 2 value of the phosphate close to 7. At high pH values, the 20H group of ri-bose can also be deprotonated (Shabarova and Bogdanov, 1994). 

Surface modification of mesoporous silica gel (average pore diameter 15 nm) by P-nicotinamide adenine dinucleotide (NAD+) (Vartzouma et al. 2004) leads to changes in the Si CP MAS NMR spectrum (Figure 1.247). The intensity of Qj and Qi sites decreases because of replacing of the surface H atoms by NAD+. This changes can be used to estimate the adsorption degree of a modifier that is of importance to elucidate the influence of modified surfaces on the interfacial behavior of water or other adsorbates. 

---