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Emission of Alkali Halide Cluster Ions from the Charged Droplets Generated from Electrospray Ionization
IF 3.1 2区 化学 Q2 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-05 DOI: 10.1021/jasms.4c0045210.1021/jasms.4c00452
Seongjae Jang, Minsu Kim, Yoonjin Kim, Junyoung Ahn and Jongcheol Seo*, 

In this study, the formation and emission of alkali halide cluster ions in charged droplets generated by electrospray ionization (ESI) was investigated using mass spectrometry (MS). We focus on ion emission at the air–solution interface of charged droplets, distinguishing between two mechanisms: the ion evaporation model (IEM), where ions are released directly from the interface, and the charge residue model (CRM), where ions are generated after complete solvent evaporation. Using an iodide/chloride mixture, we analyzed how interfacial affinity influences the composition of the generated alkali halide cluster cations and anions. With the knowledge that iodides have much higher interfacial affinities than chlorides, a relative faction of iodide in the cluster ion enables us to distinguish between IEM and CRM. Small cluster anions and cations exclusively containing iodides are suggested to be from IEM, while the larger cluster ions containing more chlorides are expected to be from CRM. This work clarifies the distinctions between IEM and CRM in alkali halide cluster ion formation and also establishes a robust analytical approach for assessing interfacial affinities of ions using ESI-MS, which may potentially enhance our understanding of interfacial chemistry and its implications in atmospheric and analytical sciences.

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引用次数: 0
Characterization of Sugammadex-Related Isomeric Cyclodextrin Impurities Using Cyclic Ion Mobility High-Resolution Mass Spectrometry. 利用环离子迁移高分辨质谱法表征舒降之相关异构环糊精杂质
IF 3.1 2区 化学 Q2 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-05 Epub Date: 2025-01-24 DOI: 10.1021/jasms.4c00243
Péter S Szakály, Dávid Papp, Arnold Steckel, Erzsébet Varga, Gitta Schlosser

Cyclic ion mobility-mass spectrometry (cIM-MS) is a powerful technique for separating and identifying isomeric mixtures of compounds. When coupled with chromatography, cIM-MS creates a multidimensional separation system, with high resolving power and peak capacity. In this study, we report the cyclic ion mobility separation and high-resolution mass spectrometry identification of four regioisomers of a Sugammadex-related impurity, abbreviated as Di-OH-SGM. Separation using multipass cyclic ion mobility was achieved by selecting the [M + 2Na]2+ ion, while other adducts, such as [M + Na]+, [M + 2H]2+, [M + H + Na]2+, and [M - 2H]2- did not yield isomer separation. Two methods were developed for ion mobility separation of the isomers: a conventional multipass method and a slicing method. Isomer assignment was based on the characteristic fragment ions. The collision cross section values (cTWCCSN2) of the resolved cyclodextrin isomers were also determined. Ion mobility separation of structurally different fragment ions was demonstrated. Additionally, by coupling cIM-MS with reversed-phase liquid chromatography (HPLC-cIM-MS), two-dimensional separation of the isomers was achieved. The isomers, separated using HPLC-cIM-MS, were identified with the same approach as with cIM-MS alone, and their elution order provided insights into their relative hydrophobicity.

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引用次数: 0
New Library-Based Methods for Nontargeted Compound Identification by GC-EI-MS. 基于文库的非靶向化合物GC-EI-MS鉴定新方法
IF 3.1 2区 化学 Q2 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-05 Epub Date: 2025-01-13 DOI: 10.1021/jasms.4c00451
Deborah F McGlynn, Lindsay D Yee, H Martin Garraffo, Lewis Y Geer, Tytus D Mak, Yuri A Mirokhin, Dmitrii V Tchekhovskoi, Coty N Jen, Allen H Goldstein, Anthony J Kearsley, Stephen E Stein

While gas chromatography mass spectrometry (GC-MS) has long been used to identify compounds in complex mixtures, this process is often subjective and time-consuming and leaves a large fraction of seemingly good-quality spectra unidentified. In this work, we describe a set of new mass spectral library-based methods to assist compound identification in complex mixtures. These methods employ mass spectral uniqueness and compound ubiquity of library entries alongside noise reduction and automated comparison of retention indices to library compounds. As a test data set, we used a publicly available electron ionization mass spectrometry data set consisting of 4833 spectra of particulate organic compounds emitted by combustion of wildland fuels. In the present work, spectra in this data set were first identified using the NIST 2023 EI-MS Library and associated batch process identification software (NIST MS PepSearch) using retention-index corrected Identity Search scoring. Resulting identifications and related information were then employed to parametrize other factors that correlate with identification. A method for identifying compounds absent from but related to those present in mass spectral libraries using the Hybrid Similarity Search is illustrated. Nevertheless, some 90% of the spectra remain unidentified. Through comparison of unidentified to identified mass spectra in this data set, a new simple measure, namely median relative abundance, was developed for evaluating the likelihood of identification.

虽然气相色谱-质谱法(GC-MS)长期以来一直用于鉴定复杂混合物中的化合物,但该过程通常是主观且耗时的,并且留下了很大一部分看似质量良好的光谱未被识别。在这项工作中,我们描述了一套新的基于质谱库的方法来辅助复杂混合物中的化合物鉴定。这些方法利用库条目的质谱唯一性和化合物的普遍性,以及降噪和保留指数与库化合物的自动比较。作为测试数据集,我们使用了一个公开的电子电离质谱数据集,该数据集由4833个由荒地燃料燃烧释放的颗粒有机化合物的光谱组成。在目前的工作中,该数据集中的光谱首先使用NIST 2023 EI-MS库和相关的批处理识别软件(NIST MS PepSearch)使用保留索引校正的身份搜索评分进行识别。结果识别和相关信息然后被用来参数化与识别相关的其他因素。一种方法来识别化合物不存在,但相关的那些存在于质谱库使用混合相似搜索说明。然而,大约90%的光谱仍未被识别。通过对该数据集中未识别质谱与已识别质谱的比较,建立了一种新的简单度量,即中位数相对丰度,用于评估鉴定的可能性。
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引用次数: 0
Ionization Characteristics of Glycan Homologues in Various Modes of Electrospray. 聚糖同源物在不同电喷雾模式下的电离特性。
IF 3.1 2区 化学 Q2 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-05 Epub Date: 2024-12-23 DOI: 10.1021/jasms.4c00425
Nicholas R Allen, Kanwal Jeet, Tolulope Ogunsanya, Ian Ferraro, Nancy Fernandes, Huishan Li, Thaddaeus Webster, Carrie Mason, Anyin Li

Fluorescence labeled glycan homologous mixtures were quantified using fluorescence and then used to evaluate ionization performances in electrospray ionization at micro, nano, and femto flow modes. nanoESI produced higher (2+ and 3+) charged ions adducted with sodium and calcium. In comparison, femtoESI was found to favor the generation of [M + H]+ ions against metal adducts, even with nonvolatile salts up to 1 mM for NaCl and 100 μM for CaCl2. For labeled glucose homopolymer (GHP) glycans, nanoESI and femtoESI had 0.81 and 3 nM detection limits, respectively. With LC separation and a much higher flow rate, conventional microflow ESI detected all glycans with 10-fold lower concentrations. Overall, nanoESI had the optimum uniformity in the relative ionization efficiency (RIE). When summing up intensities of analyte ions formed with all charge carriers, the RIE of the midsized glycans (10 to 16 glucose units) appear to be uniform (RIE 95%-105%). For the smaller (1-5 glucose units) glycan components, femtoESI provided better uniformity than nanoESI and conventional ESI. For the labeled IgG N-glycans, the impact of chemical structure on the ionization efficiency was revealed by the strong correlation between their RIE trends in different ionization modes.

荧光标记的聚糖同源混合物使用荧光定量,然后用于评估在微、纳米和飞飞流模式下电喷雾电离的电离性能。纳米esi产生了与钠和钙内合的更高的(2+和3+)带电离子。相比之下,femtoESI有利于金属加合物生成[M + H]+离子,即使是非挥发性盐高达1 mM (NaCl)和100 μM (CaCl2)。对于标记的葡萄糖均聚物(GHP)聚糖,nanoESI和femtoESI的检出限分别为0.81 nM和3 nM。通过LC分离和更高的流速,传统的微流ESI检测到的多糖浓度降低了10倍。总的来说,纳米esi在相对电离效率(RIE)上具有最佳的均匀性。当对所有载流子形成的分析物离子的强度进行汇总时,中等大小聚糖(10 ~ 16个葡萄糖单位)的RIE似乎是均匀的(RIE 95%-105%)。对于较小的糖组分(1-5葡萄糖单位),飞质ESI比纳米ESI和常规ESI具有更好的均匀性。对于标记的IgG n -聚糖,化学结构对其电离效率的影响体现在它们在不同电离模式下的RIE趋势之间的强相关性。
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引用次数: 0
Gas-Phase Fluorescence Excitation Experiments on Cryogenically Cold Rhodamine B Cations Linked to Various Amino Acid Esters. 低温冷罗丹明B阳离子与不同氨基酸酯连接的气相荧光激发实验。
IF 3.1 2区 化学 Q2 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-05 Epub Date: 2025-01-06 DOI: 10.1021/jasms.4c00469
Iden Djavani-Tabrizi, Ziqi Yuan, Thomas Toft Lindkvist, Jiamin Xing, Li Chen, Steen Bro Ndsted Nielsen

Förster resonance energy transfer (FRET) is becoming a valuable technique in gas-phase structural biology for identifying local structural motifs and conformations of biological molecules, such as peptides and proteins. This method involves labeling the biomolecule with two dyes, a donor dye and an acceptor dye, that are commonly charged rhodamines. Here we examine how different amino acid (AA) methyl esters linked to the dye via amide linkages can influence the dye transition energy and, consequently, the energy-transfer efficiency, using cryogenic ion fluorescence spectroscopy. Absorption spectra were recorded for rhodamine B+-labeled AA esters (RB+-AA) through fluorescence-excitation experiments at the LUNA2 setup in Aarhus, which operates at cryogenic temperatures (down to approximately 100 K). The AAs studied include aliphatic ones (alanine (A), leucine (L), tert-leucine (tert-L), and methionine (M)), aromatic ones (phenylalanine (F) and tryptophan (W)), and two with polar side chains (serine (S) and threonine (T)). Results show that the band maximum either remains unchanged compared to RB+ or red shifts by over 3 nm in the case of RB+-M and RB+-F. While the spectra of RB+-A and RB+-L closely resemble that of RB+, RB+-tert-L shows a distinct red shift of about 1.4 nm. Spectral variations do not appear to be more influenced by the presence of aromatic AA side chains than other types, as differences observed between aliphatic AAs are comparable to those between the three groups. Instead, these variations appear to arise from differing conformations where the dihedral angle between the xanthene moiety and the pendant phenyl group varies, as influenced by the linked AA side chain. The angle determines the π-overlap between the two aromatic moieties, and according to TD-DFT calculations, an angle larger than 90° can easily account for red shifts due to larger delocalization of the π-electron cloud. Another factor is the polarizability of the side chain that could also contribute to the red shift. RB+-F and RB+-W spectra exhibit red-shifted, narrower absorption profiles, which is likely associated with the large aromatic side chains that limit the number of contributing structural configurations.

Förster共振能量转移(FRET)正在成为气相结构生物学中一种有价值的技术,用于识别生物分子(如肽和蛋白质)的局部结构基序和构象。这种方法包括用两种染料标记生物分子,一种是供体染料,一种是受体染料,这两种染料通常是带电荷的罗丹明。在这里,我们研究了不同的氨基酸(AA)甲酯通过酰胺键连接到染料如何影响染料的转变能量,从而影响能量转移效率,使用低温离子荧光光谱。在奥尔胡斯的LUNA2装置上,通过荧光激发实验记录了罗丹明B+标记的AA酯(RB+-AA)的吸收光谱,该装置在低温(低至约100 K)下工作。研究的AA包括脂肪族(丙氨酸(A),亮氨酸(L),亮氨酸(tert-L)和蛋氨酸(M)),芳香族(苯丙氨酸(F)和色氨酸(W)),以及两个极性侧链(丝氨酸(S)和苏氨酸(T))。结果表明,与RB+相比,RB+-M和RB+-F的能带最大值保持不变或红移超过3nm。虽然RB+-A和RB+-L的光谱与RB+非常相似,但RB+-tert-L表现出明显的红移,约为1.4 nm。与其他类型相比,芳香AA侧链的存在对光谱变化的影响似乎并不大,因为在脂肪族AA之间观察到的差异与三组之间的差异相当。相反,这些变化似乎是由不同的构象引起的,在构象中,由于连接的AA侧链的影响,杂蒽部分和悬垂的苯基之间的二面角发生了变化。这个角度决定了两个芳基之间的π重叠,根据TD-DFT计算,大于90°的角度可以很容易地解释由于π电子云较大的离域而导致的红移。另一个因素是侧链的极化性,这也可能导致红移。RB+-F和RB+-W光谱表现出红移,窄吸收谱,这可能与大芳侧链限制了贡献结构构型的数量有关。
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引用次数: 0
Mass Spectrometry Analysis of Chemically and Collisionally Dissociated Molecular Glue- and PROTAC-Mediated Protein Complexes Informs on Disassembly Pathways. 化学和碰撞解离分子胶和protac介导的蛋白质复合物的质谱分析为拆卸途径提供了信息。
IF 3.1 2区 化学 Q2 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-05 Epub Date: 2025-01-15 DOI: 10.1021/jasms.4c00429
Edvaldo V S Maciel, Jonathan Eisert, Julian Müller, Tanja Habeck, Frederik Lermyte

Molecular glues (MGs) and proteolysis-targeting chimeras (PROTACs) are used to modulate protein-protein interactions (PPIs), via induced proximity between compounds that have little or no affinity for each other naturally. They promote either reversible inhibition or selective degradation of a target protein, including ones deemed undruggable by traditional therapeutics. Though native MS (nMS) is capable of analyzing multiprotein complexes, the behavior of these artificially induced compounds in the gas phase is still not fully understood, and the number of publications over the past few years is still rather limited. Here, we studied two MG-induced complexes between mTORFRB and FKBP12 as well as a PROTAC-induced complex between FKBP51FK1 and the von Hippel-Lindau E3 ligase (VHL). Native MS combined with collision-induced dissociation (CID) provided a way of measuring not only the formation of these complexes but also their dissociation pathways. Both protein complexes seem to eject preferably the centrally located small (compared to the mass of the proteins) ligand upon CID, rather than dissociating a peripheral subunit, as is often observed for naturally occurring protein complexes. In contrast, chemically induced dissociation in solution generated complementary data to CID, by disrupting the PPI surface, which resulted in more diverse MS spectra that preserved the stronger interactions in solution.

分子胶(mg)和蛋白水解靶向嵌合体(PROTACs)被用于调节蛋白-蛋白相互作用(PPIs),通过诱导天然相互亲和力很少或没有亲和力的化合物之间的接近。它们促进目标蛋白的可逆抑制或选择性降解,包括传统疗法认为不可药物的蛋白。虽然天然MS (nMS)能够分析多蛋白复合物,但这些人工诱导的化合物在气相中的行为仍未完全了解,并且在过去几年中发表的数量仍然相当有限。在这里,我们研究了mTORFRB和FKBP12之间的两种mg诱导复合物以及FKBP51FK1和von Hippel-Lindau E3连接酶(VHL)之间的protac诱导复合物。天然质谱结合碰撞诱导解离(CID)提供了一种方法,不仅可以测量这些复合物的形成,还可以测量它们的解离途径。这两种蛋白质复合物似乎都倾向于将位于中心的小配体(与蛋白质的质量相比)排斥在CID上,而不是像通常在自然发生的蛋白质复合物中观察到的那样解离周围的亚基。相反,溶液中的化学诱导解离通过破坏PPI表面,产生了与CID互补的数据,从而产生了更多样化的质谱,保留了溶液中更强的相互作用。
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引用次数: 0
Rigorous Analysis of Multimodal HDX-MS Spectra. 多模态HDX-MS谱的严格分析。
IF 3.1 2区 化学 Q2 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-05 Epub Date: 2025-01-21 DOI: 10.1021/jasms.4c00471
Lisa M Tuttle, Ellie I James, Florian Georgescauld, Thomas E Wales, David D Weis, John R Engen, Abhinav Nath, Rachel E Klevit, Miklos Guttman

An inherent strength of hydrogen/deuterium exchange coupled to mass spectrometry (HDX-MS) is its ability to detect the presence of multiple conformational states of a protein, which often manifest as multimodal isotopic envelopes. However, the statistical considerations for accurate analysis of multimodal spectra have yet to be established. Here we outline an unrestrained binomial distribution fitting approach with the corresponding statistical tests to accurately detect and, when possible, deconvolute isotopic distributions that contain multiple subpopulations. The algorithms have been incorporated into an updated version of the freely available software, HX-Express, and validated using known mixtures of peptides deuterated to varying degrees. This approach presents a readily accessible tool to fit and interpret bimodal and trimodal behavior in HDX-MS data for mixed populations, EX1 kinetics, and pulse labeling data.

氢/氘交换耦合质谱(HDX-MS)的固有优势在于它能够检测蛋白质的多种构象状态,这些构象状态通常表现为多模态同位素包膜。然而,对多模态光谱进行精确分析的统计考虑尚未建立。在这里,我们概述了一种不受约束的二项分布拟合方法,以及相应的统计检验,以准确地检测并在可能的情况下反卷积包含多个亚群的同位素分布。该算法已纳入免费软件HX-Express的更新版本,并使用不同程度氘化的已知多肽混合物进行验证。该方法提供了一种易于获取的工具,用于拟合和解释混合种群、EX1动力学和脉冲标记数据的HDX-MS数据中的双峰和三峰行为。
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引用次数: 0
Faces of Mass Spectrometry/Ljiljana Paša-Tolić.
IF 3.1 2区 化学 Q2 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-05 Epub Date: 2025-01-24 DOI: 10.1021/jasms.4c00513
Anne Brenner, J D Brookbank
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引用次数: 0
The Enzyme Effect: Broadening the Horizon of MS Optimization to Nontryptic Digestion in Proteomics. 酶效应:拓宽质谱优化到蛋白质组学非色氨酸消化的视野。
IF 3.1 2区 化学 Q2 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-05 Epub Date: 2025-01-13 DOI: 10.1021/jasms.4c00396
Kinga Nagy, Péter Sándor, Károly Vékey, László Drahos, Ágnes Révész

In recent years, alternative enzymes with varied specificities have gained importance in MS-based bottom-up proteomics, offering orthogonal information about biological samples and advantages in certain applications. However, most mass spectrometric workflows are optimized for tryptic digests. This raises the questions of whether enzyme specificity impacts mass spectrometry and if current methods for nontryptic digests are suboptimal. The success of peptide and protein identifications relies on the information content of MS/MS spectra, influenced by collision energy in collision-induced dissociation. We investigated this by conducting LC-MS/MS measurements with different enzymes, including trypsin, Arg-C, Glu-C, Asp-N, and chymotrypsin, at varying collision energies. We analyzed peptide scores for thousands of peptides and determined optimal collision energy (CE) values. Our results showed a linear m/z dependence for all enzymes, with Glu-C, Asp-N, and chymotrypsin requiring significantly lower energies than trypsin and Arg-C. We proposed a tailored CE selection method for these alternative enzymes, applying ca. 20% lower energy compared to tryptic peptides. This would result in a 10-15 eV decrease on a Bruker QTof instrument and a 5-6 NCE% (normalized collision energy) difference on an Orbitrap. The optimized method improved bottom-up proteomics performance by 8-32%, as measured by peptide identification and sequence coverage. The different trends in fragmentation behavior were linked to the effects of C-terminal basic amino acids for Arg-C and trypsin, stabilizing y fragment ions. This optimized method boosts the performance and provides insight into the impact of enzyme specificity. Data sets are available in the MassIVE repository (MSV000095066).

近年来,具有不同特异性的替代酶在基于ms的自下而上的蛋白质组学中变得越来越重要,提供了生物样品的正交信息和在某些应用中的优势。然而,大多数质谱工作流程都针对色氨酸消化进行了优化。这就提出了酶特异性是否会影响质谱分析的问题,以及目前用于非胰蛋白酶消化的方法是否不够理想。肽和蛋白质鉴定的成功依赖于MS/MS谱的信息含量,受碰撞诱导解离过程中碰撞能量的影响。我们通过LC-MS/MS测量不同的酶,包括胰蛋白酶、Arg-C、gluc、Asp-N和糜凝胰蛋白酶,在不同的碰撞能量下进行了研究。我们分析了数千个肽的肽分数,并确定了最佳碰撞能量(CE)值。我们的研究结果显示,所有酶都具有线性的m/z依赖性,其中gluc、Asp-N和糜凝胰蛋白酶所需的能量明显低于胰蛋白酶和Arg-C。我们提出了一种针对这些替代酶的定制CE选择方法,与色氨酸肽相比,其能量降低了约20%。这将导致布鲁克QTof仪器降低10-15 eV, Orbitrap仪器降低5-6 NCE%(归一化碰撞能量)。通过多肽鉴定和序列覆盖,优化后的方法将自下而上的蛋白质组学性能提高了8-32%。断裂行为的不同趋势与c端碱性氨基酸对Arg-C和胰蛋白酶的作用有关,它们稳定了y片段离子。这种优化的方法提高了性能,并深入了解了酶特异性的影响。数据集在海量存储库(MSV000095066)中可用。
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引用次数: 0
Structural Categorization of Adenine, Guanine, and Xanthine Derivatives Using Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry with 5-Nitrosalicylic Acid and 1,5-Diaminonaphtalene. 用基质辅助激光解吸/电离质谱法对5-硝基水杨酸和1,5-二氨基萘进行腺嘌呤、鸟嘌呤和黄嘌呤衍生物的结构分类
IF 3.1 2区 化学 Q2 BIOCHEMICAL RESEARCH METHODS Pub Date : 2025-02-05 Epub Date: 2025-01-04 DOI: 10.1021/jasms.4c00405
Tohru Yamagaki, Mika Nobuhara

In this study, we analyzed purine derivatives using multimatrix variation matrix-assisted laser desorption ionization mass spectrometry (MALDI MS) with α-cyano-4-hydroxycinnamic acid (CHCA), 1,5-diaminonaphtalene (DAN), 5-formylsalicylic acid (FSA), and 5-nitrosalicylic acid (NSA) as matrices. Further, we focused on the abstraction/attachment of hydrogen from/to analytes and detected [M - H]+, [M + 2H]+• and/or [M + 3H]+ in MALDI MS spectra of compounds containing nitrogen and/or carbonyl oxygen. Although [M - H]+ generation of purine compounds in MALDI MS with conventional matrices was challenging, NSA-MALDI MS effectively yielded the [M - H]+species of purine derivatives compared with CHCA, FSA, and DAN, and the [M - H]+/[M + H]+ ratios reflected their structures, such as the substituting groups and positions. We speculated that the molecular ion [M]+• generated and the subsequent hydrogen radical abstraction proceeded by NSA matrix from the α-carbon of the amine group. The nitro group (-NO2) of NSA can withdraw hydrogen radicals in photochemical reactions. The [M - H]+ of adenosine, guanosine, and inosine suggested that hydrogen abstraction occurred in the ribose unit. The xanthine isomer of paraxanthine was distinguished from those of theophylline and theobromine using their [M - H]+/[M + H]+ ratios obtained with NSA-MALDI MS. Additionally, [M + 2H]+• generated in DAN-MALDI MS of xanthine derivatives due to their carbonyl groups. The relative abundances of [M + 2H]+• of xanthine derivatives were much higher than those of the other purine derivatives such as adenine derivatives which generated [M + 3H]+ in their DAN-MALDI MS. DAN induced the hydrogen attachment of purine compounds because the amine group (-NH2) of DAN can give hydrogen radicals in photochemical reactions. NSA- and DAN-MALDI MS characterized purine derivatives and were useful for their structure categorization.

本研究以α-氰基-4-羟基肉桂酸(CHCA)、1,5-二氨基萘(DAN)、5-甲酰水杨酸(FSA)和5-硝基水杨酸(NSA)为基质,采用多基质变异基质辅助激光解吸电离质谱法(MALDI MS)分析嘌呤衍生物。此外,我们重点研究了从分析物中提取/附着氢,并在含有氮和/或羰基氧的化合物的MALDI质谱中检测到[M - H]+, [M + 2H]+•和/或[M + 3H]+。虽然用传统基质在MALDI质谱中生成[M - H]+嘌呤化合物具有挑战性,但与CHCA、FSA和DAN相比,NSA-MALDI质谱有效地生成了[M - H]+类嘌呤衍生物,且[M - H]+/[M + H]+比值反映了嘌呤衍生物的结构,如取代基和位置。我们推测,在胺基α-碳上通过NSA基质生成了分子离子[M]+•并进行了随后的氢自由基提取。在光化学反应中,NSA的硝基(-NO2)具有清除氢自由基的作用。腺苷、鸟苷和肌苷的[M - H]+表明氢的提取发生在核糖单元。利用NSA-MALDI质谱法将副黄嘌呤的黄嘌呤同分异构体与茶碱和可可碱的黄嘌呤同分异构体的[M - H]+/[M + H]+比值进行了区分。此外,由于黄嘌呤衍生物的羰基,在DAN-MALDI质谱法中生成了[M + 2H]+•。黄嘌呤衍生物的[M + 2H]+•的相对丰度远高于其他嘌呤衍生物,如腺嘌呤衍生物在其DAN- maldi ms中生成[M + 3H]+, DAN诱导嘌呤化合物的氢附着是因为DAN的胺基(-NH2)在光化学反应中可以产生氢自由基。NSA-和DAN-MALDI质谱对嘌呤衍生物进行了表征,并对其结构进行了分类。
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引用次数: 0
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Journal of the American Society for Mass Spectrometry
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