Phosphate, resonance hybrid

Because of resonance hybridization, the products of ATP hydrolysis are more stable than ATP. When a molecule has two or more alternative structures that differ only in the position of electrons, the result is called a resonance hybrid. The electrons in a resonance hybrid with several contributing structures possess much less energy than those with fewer contributing structures. The contributing structures of the phosphate resonance hybrid are illustrated in Figure 4.10. 

The stability of the resonance hybrid (see fig. 10.4/7) accounts for the catalytic action of pyridoxal-5 -phosphate in the reactions shown in equations (3) through (6). 

The covalent bonding in the tetrahedral P04 anion may be described as the average of four resonance hybrids such as (I), giving the average structure (2) with tetrahedral (Td) symmetry. These two views of the bonding illustrate important features of phosphate chemistry. (I) shows that up to three... 

Fig. 49. 600-MHz H NMR spectra of cross-linked mixed-valency asymmetric hybrid hemoglobin (a+CNp)A(aP)cXL, in deoxy and CO forms, in the presence of 0.1 Af phosphate at pH 6.8 and 21°C. (A) Hyperfine-shifted proton resonances in D20 (B) exchangeable and hyperfine-shifted proton resonances in H20. [From Miura and Ho (1982)].

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