Andriole Erica J, Colyer Kathryn E, Cornell Elizabeth, Poutsma John C
Department of Chemistry, The College of William and Mary, Williamsburg, Virginia 23187-8795, USA.
J Phys Chem A. 2006 Oct 12;110(40):11501-8. doi: 10.1021/jp063081f.
The absolute proton affinities of the nonprotein amino acids canavanine and canaline have been determined using the extended kinetic method in an electrospray ionization quadrupole ion trap instrument. Canavanine results from the substitution of an oxygen atom for the delta-CH2 group in the side chain of the protein amino acid arginine, whereas canaline results from a similar substitution at the delta-CH2 group in the side chain of ornithine. Absolute proton affinities of 1001+/-9 and 950+/-7 kJ/mol are obtained for canavanine and canaline, respectively. For canaline, this proton affinity is in excellent agreement with theoretical predictions obtained using the hybrid density functional theory method B3LYP/6-311++G**//B3LYP/6-31+G*. For canavanine, theory predicts a somewhat larger proton affinity of 1015 kJ/mol. Oxygen atom substitution in these nonprotein amino acids results in a decrease in their proton affinities of 40-50 kJ/mol compared to arginine and ornithine.
已使用扩展动力学方法在电喷雾电离四极杆离子阱仪器中测定了非蛋白质氨基酸刀豆氨酸和刀豆氨酸的绝对质子亲和力。刀豆氨酸是由蛋白质氨基酸精氨酸侧链中的δ-CH2基团被氧原子取代产生的，而刀豆氨酸是由鸟氨酸侧链中的δ-CH2基团发生类似取代产生的。刀豆氨酸和刀豆氨酸的绝对质子亲和力分别为1001±9和950±7 kJ/mol。对于刀豆氨酸，该质子亲和力与使用混合密度泛函理论方法B3LYP/6-311++G**//B3LYP/6-31+G*获得的理论预测结果非常吻合。对于刀豆氨酸，理论预测其质子亲和力稍大，为1015 kJ/mol。与精氨酸和鸟氨酸相比，这些非蛋白质氨基酸中的氧原子取代导致它们的质子亲和力降低了40-50 kJ/mol。
