Quantum chemical caculations of the most stable conformers of methylamine-pyridoxal-5-phosphate Schiff base three tautomeric (enol, keto, and zwitterionic) structures and their monohydrates and dihydrates have been carried out at the B3LYP/6-31+G**, M062X/6-31+G**, and BVP86/TZVP levels of theory. The optimized structures, harmonic force fields, and vibrational frequencies of tautomers have been obtained. The influence of macrohydration on the conformational composition of tautomers have been studied using the polarized continuum model. Vertical ionization potentials of the most stable monohydrates and dihydrates of methylamine-pyridoxal-5'-phosphate tautomers have been calculated. The influence of macrohydration and microhydration on the structure, spectra, and vertical ionization energies of the monohydrates and dihydrates of methylamine-pyridoxal-5-phosphate tautomers have been discussed.

中文翻译：

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最稳定的甲胺-吡啶代-5'-磷酸互变异构体与水相互作用的量子化学模型：一水合物和二水合物的结构和性质

已在B3LYP / 6-31 + G **上进行了最稳定构象的甲胺-吡啶氧-5-磷酸席夫碱三个互变异构体（烯醇，酮和两性离子）结构及其一水合物和二水合物的量子化学计算， M062X / 6-31 + G **和BVP86 / TZVP的理论水平。获得了互变异构体的优化结构，谐波力场和振动频率。使用极化连续谱模型研究了大水合对互变异构体构象组成的影响。已计算出最稳定的甲胺-吡py醛-5'-磷酸互变异构体一水合物和二水合物的垂直电离势。大水合和微水合对结构，光谱，