Pterin cation

Pterin cation, TIP3, and SPC water van der Waals parameters... 

Aminopteridine is the most sensitive to acid hydrolysis, and 6-amino- and 6-dimethyl-amino-pteridine are also hydrolyzed, even by cold 0.0IN hydrochloric acid, too rapidly for accurate determination of the cation form (52JCS1620). 2-Amino- and 4-amino-pteridine are not readily attacked by IN HCl at 20 °C but at 100 °C the former compound is destroyed and the latter converted into pteridin-4-one (5UCS474). 2,4-Diaminopteridine can be hydrolyzed by refluxing in 6N HCl for 30 minutes to 2-aminopteridin-4-one (pterin 2) and after... 

For molecules and molecular ions, such as the cations of 8-methyl-N5-deazapterin and 8-methyl-pterin, the charge distribution (which is represented in MD simulations by a set of discrete atomic charges) will be dependent on the chosen quantum chemical model. Differences in the charge distributions of these cations may influence both the relative binding and solvation thermodynamics. Consequently, we studied the relative solvation thermodynamics of similar DHFR-binding molecular ions.30 Atomic charges... 

Table 1. Dependence of free energies (kcal/mol) on the residue-based cutoff radii Rc (A) for generation of cation-solvent (c-s) and solvent-solvent (s-s) interaction lists. Free energy changes are given for the forward AGf (i.e. 8-methyl-N5-deazapterin — 8-methyl-pterin) and reverse AGr mutations of the electrostatic terms. ...

Figure 4. Structures for cations (i.e. N3 protonated forms) of the 8-methyl substituted (a) N5-deazapterins and (b) pterins R5, R6 and R7 are either H or CH3.

Amidinium type resonance determines protonation sites also in some more complex systems, such as cytosine [74] and pterin [75]. Cytosine is protonated on the ring nitrogen N-1 (Katritzky and Waring, 1963) and calculations on the electronic structure of the cation have been published (Denis and Gilbert, 1968). Pterin is... 

The preparation of a cubic phase with supramolecular chirality was achieved using a branched folic acid derivative incorporating glutamic acid residues (Fig. 11) as the source of chirality [93]. The pterin rings of folic acid residues are able to form a cyclic tetramer as a result of two hydrogen bonds between the components. Depending on the number of carbon atoms in the alkyl substituents, the compounds form columnar phases over a wide temperature range, and for 8 and 9 form cubic phases at temperatures above 130 °C. Addition of sodium triflate stabilises the cubic phase for 7, and the salt is incorporated into the other mesophases. It was implied that the cation resides between stacked tetramers. Supramolecular chirality is expressed for both the columnar and the cubic phases, as revealed by vari-... 

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