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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Protonation of Gly_n Homologues in Matrix-Assisted Laser Desorption Ionization
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Protonation of Gly_n Homologues in Matrix-Assisted Laser Desorption Ionization

机译：基质辅助激光解吸电离中Gly_n同源物的质子化

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摘要

Protonation reactions of Gly_n homologues were studied in order to elucidate the effect of peptide chain length and matrix materials on the matrix-assisted laser desorption ionization (MALDI) mechanism. At 337 nm nitrogen laser excitation the relative ion yield-chain length relationship showed considerable variability in 3,5-dimethoxy-4-hydroxycinnamic acid (SA), 2,5-dihydroxybenzoic acid (DHB), 6-aza-2-thiothymine (ATT), and α-cyano-4-hydroxycinnamic acid (CHCA), the four matrices studied. For SA and ATT, a monotonic increase of relative ion yields (RIYs) was observed with increasing peptide length. Similar increasing pattern and significantly higher RIYs were found for the homologues of the Gly_n series in the CHCA matrix with the exception of Gly. The particularly high MALDI ion yield of this amino acid in CHCA may be attributed to preferential embedding and/or more efficient condensed-phase proton transfer. To unveil the nature of the proton-transfer reactions in MALDI, the peptide length dependence of the measured RIYs was compared to the trends observed in proton affinities (PAs) of the same homologues as well as to ion-molecule reaction rates calculated using the Langevin cross section. Chain extension enhancements in MALDI RIYs of all the studied matrices cannot be explained either by the increase in ground-state ion-molecule reaction rates or by a linear dependence on gas-phase PAs. However, in SA and ATT positive correlation was observed between MALDI RIYs of Gly_n homologues and their PAs. The RIYs observed in CHCA were significantly higher than in SA. This effect could be explained by the markedly lower PA of CHCA (183 ± 2 kcal/mol) compared to that of SA (204 ± 4 kcal/mol).
机译：为了阐明肽链长度和基质材料对基质辅助激光解吸电离（MALDI）机理的影响，研究了Gly_n同源物的质子化反应。在337 nm氮气激光激发下，相对离子产率-链长关系显示3,5-二甲氧基-4-羟基肉桂酸（SA），2,5-二羟基苯甲酸（DHB），6-氮杂-2-硫代胸腺嘧啶（ ATT）和α-氰基-4-羟基肉桂酸（CHCA），这四个矩阵进行了研究。对于SA和ATT，随着肽长度的增加，相对离子产率（RIYs）单调增加。在CHCA矩阵中，除了Gly之外，Gly_n系列的同源物也发现了相似的增长模式和显着更高的RIY。 CHCA中此氨基酸的MALDI离子收率特别高，这可能归因于优先嵌入和/或更有效的凝聚相质子转移。为了揭示MALDI中质子转移反应的性质，将测得的RIYs的肽长度依赖性与相同同源物的质子亲和力（PAs）趋势以及使用Langevin计算的离子分子反应速率进行了比较。横截面。不能通过基态离子分子反应速率的增加或对气相PA的线性依赖性来解释所有研究基质的MALDI RIY的链增长增强。然而，在SA和ATT中，观察到Gly_n同系物的MALDI RIY与其PA之间存在正相关。 CHCA中观察到的RIY显着高于SA中。 CHCA的PA（183±2 kcal / mol）显着低于SA（204±4 kcal / mol）的PA，可以解释这种效果。

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