质谱法研究气相中18-冠醚-6与氨基酸的非共价相互作用
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摘要
利用电喷雾电离质谱研究了在气相条件下18-冠醚-6与20余种天然氨基酸及其异构体间的非共价相互作用。定性结果表明,在气相中18-冠-6可以与氨基酸形成化学计量比为1∶1的非共价复合物。配制一系列不同浓度的18-冠-6分别与固定浓度的氨基酸反应,利用质谱测得反应物和产物的质谱峰,计算冠醚分别与L-苯丙氨酸、L-酪氨酸、L-赖氨酸和L-天冬氨酸反应的复合物结合常数lg Ka分别为3.90、3.75、4.06和3.64,基于此建立了校准曲线。通过竞争反应实验,以上述4种氨基酸与冠醚复合物的结合常数为参考值,可推算得到其余氨基酸与冠醚的结合常数。实验结果表明,冠醚-氨基酸复合物的稳定性与氨基酸的种类相关,节碱性氨基酸以及侧链是烷基(或氢原子)的氨基酸对冠醚的亲和性更好,而酸性氨基酸(如L-丝氨酸)以及侧链上有酰胺键的氨基酸,对冠醚的亲和性较低。研究了18-冠-6对L型氨基酸及其D型异构体的手性选择性,结果表明,18-冠-6只能识别部分中性氨基酸。
The non-covalent interactions between 18-crown-6( 18c6) and 20 common types of protonated amino acids were explored by electrospray ionization mass spectrometry( ESI-MS). The mass spectra showed the formation of 1 ∶ 1 stoichiometric non-covalent complexes between 18c6 and amino acids. The calibration curves and linear equations for the complexes of L-Phe,L-Tyr,L-Lys and L-Asp with 18c6 were established by mass spectrometric titration and used as reference values for competitive ESI-MS. Through competitive equilibrium,the binding constants for the complexes of 18c6 with other L-amino acids and their D-isomers were derived. It was found,as a general trend,lg Ka for the complexes of 18c6 with the basic amino acid and the amino acid with alkyl side chain were larger than other complexes,and among the amino acids with alkyl side chain,Gly and Ala exhibited greater 18c6 binding affinities. As for Ser and Thr,the intramolecular hydrogen bond between the nitrogen atom from terminal -NH_2 and the oxygen atom from carboxyl may impede their protonated amino-group to attack the 18c6. Furthermore,Gln and Asn exhibited lower 18c6 binding affinities probably due to effects of electron-withdrawing group of acylamide. Finally,the chiral selectivity of 18c6 for 19 L-,or D-amino acids was measured by ESI-MS,indicating 18c6 could only recognize some neutral amino acid isomers.
The non-covalent interactions between 18-crown-6( 18c6) and 20 common types of protonated amino acids were explored by electrospray ionization mass spectrometry( ESI-MS). The mass spectra showed the formation of 1 ∶ 1 stoichiometric non-covalent complexes between 18c6 and amino acids. The calibration curves and linear equations for the complexes of L-Phe,L-Tyr,L-Lys and L-Asp with 18c6 were established by mass spectrometric titration and used as reference values for competitive ESI-MS. Through competitive equilibrium,the binding constants for the complexes of 18c6 with other L-amino acids and their D-isomers were derived. It was found,as a general trend,lg Ka for the complexes of 18c6 with the basic amino acid and the amino acid with alkyl side chain were larger than other complexes,and among the amino acids with alkyl side chain,Gly and Ala exhibited greater 18c6 binding affinities. As for Ser and Thr,the intramolecular hydrogen bond between the nitrogen atom from terminal -NH_2 and the oxygen atom from carboxyl may impede their protonated amino-group to attack the 18c6. Furthermore,Gln and Asn exhibited lower 18c6 binding affinities probably due to effects of electron-withdrawing group of acylamide. Finally,the chiral selectivity of 18c6 for 19 L-,or D-amino acids was measured by ESI-MS,indicating 18c6 could only recognize some neutral amino acid isomers.
引文
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5 Lee A,Choi H J,Jin K B,Hyun M H.J.Chromatogr.A,2011,1218(26):4071-4076
6 Yamashita J,Minagawa M,Sonobe A,Ohashi S.Chem.Lett.,1982,9:1409-1412
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8 Brown G R,Foubister A.J.Med.Chem.,1983,26:590-592
9 LIU Yu-Jian,LIU Zhi-Min,XU Zhi-Gang.Chinese J.Anal.Chem.,2017,45(3):369-373刘育坚,刘智敏,许志刚.分析化学,2017,45(3):369-373
10 Mistarz U H,Brown J M,Haselmann K F,Rand K D.Structure,2016,24:310-318
11 Gromiha M M,Selvaraj S.Curr.Bioinform.,2008,3(1):1-9
12 Liu Z J,Cheng S J,Gallie D R,Julian R R.Anal.Chem.,2008,80:3846-3852
13 Frański R,Schroeder G,Kamysz W,Niedzialkowskin P,Ossowski T.J.Mass Spectrom.,2007,42:459-466
14 Stedwell C N,Galindo J F,Gulyuz K,Roitberg A E,Polfer N C.J.Phys.Chem.A,2013,117:1181-1188
15 Chen Y,Rodgers M T.J.Am.Chem.Soc.,2012,134:5863-5875
16 Schmidt A C,Neustadt M,Otto M.J.Mass Spectrom.,2007,42:771-780
17 Kempen E C,Brodbelt J S.Anal.Chem.,2000,72:5411-5416
18 Zhang H R,Chen G,Wang L,Ding L,Tian Y,Jin W Q,Zhang H Q.Int.J.Mass Spectrom.,2006,252:1-10
19 TANG Ming-Sheng,LI Xiao-Fei.J.Zhengzhou Univ.,2004,36(3):59-63唐明生,李晓飞.郑州大学学报(理学版),2004,36(3):59-63
20 Yu Q,Cao J,Liu T,Wang Z.Chem.Res.Chin.Univ.,2009,25(3):362-367
21 Usacheva T R,Shamin V A,Chemov I V,Matteoli E,Terekhova I V,Kumeev R S.Chem.Phys.Lett.,2012,543:155-158
22 Wei W,Chu Y,Wang,R,He,X,Ding,C.Rapid Commun.Mass Spectrom.,2015,29:927-936
23 LI Ming,CHEN Huan-Wen,LIU Zhi-Qiang,LIU Shu-Ying,JIN Qin-Han.Prog.Chem.,2006,18(10):1369-1374李明,陈焕文,刘志强,刘淑莹,金钦汉.化学进展,2006,18(10):1369-1374
24 YUAN Bi,CHEN Wei-Hong,WANG Wu-Lin,SHI Hao.Zhejiang Chemical Industry,2013,44(5):25-31袁碧,陈卫红,汪吴林,石浩.浙江化工,2013,44(5):25-31
25 Wu E Q,Kim K T,Adidi S K,Lee Y K,Cho J W,Lee W,Kang J S,Arch.Pharm.Res.,2015,38(8):1499-1505