2-氨基-5-硝基吡啶在基体辅助激光解吸/电离质谱法测定核酸分子中的应用

报道以2-氨基-5-硝基吡啶为基体用基体辅助激光解吸/电离质谱法(MALDI-MS)对DNA样品进行测定并研究它们的激光质谱特征,结果表明,2-氨基-5-硝基吡啶是DNA的一高效基体.用柠檬酸铵和NH_4~+阳离子交换树脂除去试剂和样品中的碱金属离子,能显著地提高解吸/电离DNA分子的效率.     

2—氨基—5—硝基吡啶在基体辅助激光解吸／电离质谱法测定核酸分子中的 …

报道以２－氨基－５－硝基吡啶为基体用基体辅助激光解吸／电离质谱法（ＭＡＬＤＩ－ＭＳ）对ＤＮＡ样品进行测定并研究它们的激光质谱特征,结果表明,２－氨基－５－硝基吡啶是ＤＮＡ的一高铲基体。用柠檬酸铵和ＮＨ＾＋４阳离子交换树脂除去试剂和样品中的碱金属离子,能显著地提高解吸／电离ＤＮＡ分子的效率。     

MALDI-TOFMS测定高聚合度葡聚糖及不同基体在测定中的作用比较

应用基体辅助激光解吸电离飞行时间质谱(MALDI-TOFMS)直接对未经分级的高聚合度(n>100)葡聚糖样品进行了测定,检测到的葡聚糖最大分子量达18000以上.对2,5-二羟基苯甲酸(DHB)、1-羟基异喹啉(1-HIQ)及3,4-二羟基肉桂酸(咖啡酸,CA)3种一元基体以及DHB与1-HIQ,DHB与CA两种二元基体在测定中的作用进行了比较.结果表明,DHB基体测定的质量范围较大;DHB+1-HIQ和DHB+CA二元混合基体对样品的解吸电离效果及谱图重现性好;DHB+1-HIQ基体获得的谱图分辨率高.     

3-羟基-4-甲氧基肉桂酸--基体辅助激光解吸电离质谱法测定DNA的有效基体

报道用基体辅助激光解吸电离质谱法（ ＭＡＬＤＩ－ ＭＳ） 测定ＤＮＡ 分子的一种有效基体３－ 羟基－ ４ － 甲氧基肉桂酸。 实验发现该基体对ＤＮＡ 分子解吸和电离效率高, 对ＤＮＡｄ（ Ｔ） １０ 分子离子峰的分辨率为５ ５５１ ．４ , 信噪比为１１ ．８ 。３ － 羟基－ ４ － 甲氧基肉桂酸是ＭＡＬＤＩ－ ＭＳ 法测定ＤＮＡ 分子的一个可供选择使用有效基体。     

基体辅助激光解吸/电离飞行时间质谱在脱氧核糖核酸分析中的样品制备与纯化方法及进展

样品的制备与纯化是基体辅助激光解吸／电离飞行时间质谱(MALDI-TOF-MS)能成功用于脱氧核糖核酸(DNA)分析的关键所在。近年来对DNA样品制备与纯化方法的探讨和改进已取得了一些新的进展。本文就此作一简要概述。     

以2-氨基-5-硝基噻唑为基质辅助激光解吸/电离飞行时间质谱的有效基质分析DNA及蛋白质样品

采用碱性新基质2-氨基-5-硝基噻唑对DNA和蛋白质样品进行了基质辅助激光解吸/电离飞行时间质谱分析.结果表明,2-氨基-5-硝基噻唑能有效地解吸电离DNA和蛋白质样品.采用正离子检测模式,分析分子量小于5000的pd(T)₁₀,pd(C)₁₀,pd(A)₈,pd(G)₁₀和pd(5′ATCGATCGAT3′)DNA样品时,分辨率均可达到1万以上;与分析DNA样品的常用基质相比,2-氨基-5-硝基噻唑解吸/电离样品分子所需要的激光强度小,易于获得信噪比和分辨率高及重复性好的谱图;分析蛋白质胰岛素、细胞色素C及牛血清白蛋白样品能达到与α-氰基-4-羟基肉桂酸(HCCA)和3,5-二甲氧基-4-羟基肉桂酸(SA)相同的效果.采用负离子检测模式则能以较高的信噪比获得分子量达到7000的DNA的分子离子峰信号.此外,以2-氨基-5-硝基噻唑为基质的基质辅助激光解吸/电离(MALDI)测定还表现出一定的耐盐能力.     

α-腈基阿魏酸基体在MALDI-TOFMS测定中的应用研究

在基体辅助激光解吸电离飞行时间质谱（MALDI－TOFMS）测定中基体的作用举足轻重。有效或特效基体的发现和应用不仅可提高测试灵敏度和分辨率,加大分子量测定范围,还能扩增测试样品的种类,推动MALDI－TOFMS应用的发展。目前MALDI－TOFMS分析的常用基体^[1,2]测定多肽、蛋白质的α-腈基－4－羟基肉桂酸（4HCCA）和介子酸（SA）效果比较理想;而测定糖类物质的2,5－二羟基苯甲酸（DHB）则不能完全适用于在组成、结构、序列以及连接方式上存在多样性的碳水化合物的分子;测定DNA的3－羟基吡啶甲酸（3－HPA）使用时必须对样品、溶剂甚至基体本身进行严格纯化,较为烦琐,测定含百个碱基以上大分子量DNA的灵敏度和分辨率还不理想。本文考察研究α-腈基阿魏酸（CFA）旨在寻找MALDI－TOFMS测定的有效新基体,为MALDI－TOFMS测定提供更多的基体选择。     

3—羟基—4—甲氧基肉桂酸——基体辅助激光解吸电离质谱法测定DNA的有 …

报家长在体辅助激光解吸电离质谱法（ＭＡＬＤＩ－ＭＳ）测定ＤＮＡ分子的一种有效基体３－羟基－４－甲氧基肉桂酸。实验发现该基体对ＤＮＡ分子解吸和电离效率高,对ＤＮＡｄ（Ｔ）１０分子离子峰的分辨率为５５５１．４倍,噪比为１１．８。３－羟基－４－甲氧基肉桂酸是ＭＡＬＤＩ－ＭＳ法测定ＤＮＡ分子的一个可供选择使用有效基体。     

改善液体辅助表面解吸常压化学电离质谱成像空间分辨率的研究

液体辅助表面解吸常压化学电离源(LA-DAPCI)通过电晕放电产生的初级离子和高密度带电液滴,能够对样品表面的中性待测物进行解吸电离,该离子源具有较高的离子化效率,适合复杂基体样品的质谱成像研究.为了满足质谱成像对空间分辨率的要求,本实验通过优化离子源结构、萃取剂组成、萃取剂流量、载气流速、离子源的几何位置参数等实验条件,有效提高了LA-DAPCI源的空间分辨率(从(441±14) μm提高到(58±7)μm).应用LA-DAPCI-MS/MS方法对罗丹明6G进行测定,检测限为0.01 ng/cm2,实验结果令人满意,为其应用于复杂基体样品的质谱成像研究提供科学依据.     

表面活性剂的基体辅助激光解吸电离/质谱分析表征

利用基体辅助激光解吸电离／质谱（MALDI－MS）技术对表面活性剂的分析表征进行了详细研究。以2，5－二羟基苯甲酸作为基体，考察MALDI样品制备方法如液滴干燥法、快速干燥法及三明治法对测定结果的影响，发现三明治方法更适合表面活性剂的分析。MALDI可以准确测定离子型表面活性剂的分子量，同时对于非离子型表面活性剂，还可以测定其平均聚合度和分子量的分布。     

Determination of the glycosidic linkage in peracetylated disaccharides comprised of D-glucopyranose units by use of desorption electron-ionization mass spectrometry.

An oxonium ion at m/z317 is present in the desorption electron ionization and ammonia desorption chemical ionization mass spectra of peracetylated disaccharides, comprised of glucopyranose units linked (1-->2), (1-->3), (1-->4) and (1-->6), but is absent in the spectra of the (1-->1)-linked isomer. The ion at m/z317, which is derived from the reducing moiety, has an O-formyl group at the position of linkage to the non-reducing moiety, and O-acetyl groups at each of the remaining positions. The isomeric monoformyl, triacetyl oxonium ions (at m/z317), derived from the (1-->2)-, (1-->3)-, (1-->4)- and (1-->6)-linked disaccharides, give distinctly different mass-analysed ion kinetic energy spectra, thereby enabling the linkage position to be assigned unambiguously.     

The detection of intact double-stranded DNA by MALDI

DNA fragments have been analyzed by matrix-assisted laser desorption ionization (MALDI) and electrospray mass spectrometry. In many cases, only the single-stranded oligonucleotides have been detected. Recently, spectra of intact double-stranded DNA have been obtained in both electrospray and massive cluster impact ionization. We show here the first MALDI spectra of intact double-stranded DNA (EcoR1 adaptor 12/16) that is clearly not due to nonspecific dimer formation. 6-Aza-2-thiothymine was used as the matrix in the presence of ammonium citrate. Via the same procedure but with other matrices commonly employed for oligonucleotide analysis, the intact DNA duplex was not detected. No sign of the homodimer of either of the single strands is observed. Although the spectrum also shows peaks attributable to each of the single strands, these are demonstrated to arise from the DNA solution and not the sample preparation or desorption process.     

Effect of impurities on the matrix-assisted laser desorption/ionization mass spectra of insulin.

The effect of impurity (sodium sulfate Na2SO4; copper sulfate CuSO4; potassium ferrocyanide K4Fe(CN)6; and triammonium citrate (NH4)3C6H5O7) concentration on the positive matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) spectra of insulin is described. 2,5-Dihydroxybenzoic acid was used as a desorption matrix. The estimated maximum concentrations of tested salts for which no insulin signal was observed were determined.     

Mass spectrometry imaging of triglycerides in biological tissues by laser desorption ionization from silicon nanopost arrays

Mass spectrometry imaging (MSI) is used increasingly to simultaneously detect a broad range of biomolecules while mapping their spatial distributions within biological tissue sections. Matrix‐assisted laser desorption ionization (MALDI) is recognized as the method‐of‐choice for MSI applications due in part to its broad molecular coverage. In spite of the remarkable advantages offered by MALDI, imaging of neutral lipids, such as triglycerides (TGs), from tissue has remained a significant challenge due to ion suppression of TGs by phospholipids, e.g. phosphatidylcholines (PCs). To help overcome this limitation, silicon nanopost array (NAPA) substrates were introduced to selectively ionize TGs from biological tissue sections. This matrix‐free laser desorption ionization (LDI) platform was previously shown to provide enhanced ionization of certain lipid classes, such as hexosylceramides (HexCers) and phosphatidylethanolamines (PEs) from mouse brain tissue. In this work, we present NAPA as an MSI platform offering enhanced ionization efficiency for TGs from biological tissues relative to MALDI, allowing it to serve as a complement to MALDI‐MSI. Analysis of a standard lipid mixture containing PC(18:1/18:1) and TG(16:0/16:0/16:0) by LDI from NAPA provided an ~49 and ~227‐fold higher signal for TG(16:0/16:0/16:0) relative to MALDI, when analyzed without and with the addition of a sodium acetate, respectively. In contrast, MALDI provided an ~757 and ~295‐fold higher signal for PC(18:1/18:1) compared with NAPA, without and with additional Na⁺. Averaged signal intensities for TGs from MSI of mouse lung and human skin tissues exhibited an ~105 and ~49‐fold increase, respectively, with LDI from NAPA compared with MALDI. With respect to PCs, MALDI provided an ~2 and ~19‐fold increase in signal intensity for mouse lung and human skin tissues, respectively, when compared with NAPA. The complementary coverage obtained by the two platforms demonstrates the utility of using both techniques to maximize the information obtained from lipid MS or MSI experiments.     

Synthesis,Biomacromolecular Interactions,Photodynamic NO Releasing and Cellular Imaging of Two [RuCl(qn)(Lbpy)(NO)]X Complexes

Two light-activated NO donors [RuCl(qn)(Lbpy)(NO)]X with 8-hydroxyquinoline (qn) and 2,2′-bipyridine derivatives (Lbpy) as co-ligands were synthesized (Lbpy₁ = 4,4′-dicarboxyl-2,2′-dipyridine, X = Cl⁻ and Lbpy₂ = 4,4′-dimethoxycarbonyl-2,2′-dipyridine, X = NO₃⁻), and characterized using ultraviolet–visible (UV-vis) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (¹H NMR), elemental analysis and electrospray ionization mass spectrometry (ESI-MS) spectra. The [RuCl(qn)(Lbpy₂)(NO)]NO₃ complex was crystallized and exhibited distorted octahedral geometry, in which the Ru–N(O) bond length was 1.752(6) Å and the Ru–N–O angle was 177.6(6)°. Time-resolved FT-IR and electron paramagnetic resonance (EPR) spectra were used to confirm the photoactivated NO release of the complexes. The binding constant (K_b) of two complexes with human serum albumin (HSA) and DNA were quantitatively evaluated using fluorescence spectroscopy, Ru-Lbpy₁ (K_b~10⁶ with HSA and ~10⁴ with DNA) had higher affinity than Ru-Lbpy₂. The interactions between the complexes and HSA were investigated using matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS) and EPR spectra. HSA can be used as a carrier to facilitate the release of NO from the complexes upon photoirradiation. The confocal imaging of photo-induced NO release in living cells was successfully observed with a fluorescent NO probe. Moreover, the photocleavage of pBR322 DNA for the complexes and the effect of different Lbpy substituted groups in the complexes on their reactivity were analyzed.     

纯C60/C70的热解吸电子电离质谱研究

用热解析电子电离方法来测C60/C70的质谱获得了较好的结果。纯C60/C70样品是按文献[5]方法制得的。将C60/C70样品直接送入离子源内, 瞬间快速升温, 使C60/C70样品在分解之前就得到充分挥发, 再用70eV的电子轰击C60, C70蒸气, 使之电离得到分析鉴定。实验结果表明, 热解析电子电离方法有快原子轰击(FAB)等方法比拟的优点, 它不仅简单快速, 而且谱图本底峰少, 分子结构信息多。     

Matrix-assisted laser desorption/ionization mass spectrometry of polysaccharides with 2',4',6'-trihydroxyacetophenone as matrix

So far, there have been only a few matrices reported for detection of polysaccharides with molecular weight higher than 3000 Daltons by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). In this work, we found that 2',4',6'-trihydroxyacetophenone (THAP) is a good matrix for MALDI time-of-flight MS analysis of polysaccharides with broad mass range. Large polysaccharides, dextrans, glycoproteins and polysialic acids have been successfully detected by MALDI-MS with THAP as matrix.     

Analysis of sugar epimers using mass spectrometry: N-acetyllactosamine-6,6'-disulfate and the 2'-epimer

Galbeta1-4GlcNAc-6,6'-disulfate and 2'-epimer corresponding to Galbeta1- 4ManNAc-6,6'-disulfate were distinguished by mass spectrometry by utilizing fast atom bombardment (FAB), electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) methods. As for the steric information, negative-ion ESI mass spectrometry/mass spectrometry (MS/MS) provides the most extensive data, but FAB MS/MS also reveals detailed structural information of interest in our case, where MALDI MS is not yet fully equipped with post-source decay.     

Deconstructing Desorption Electrospray Ionization: Independent Optimization of Desorption and Ionization by Spray Desorption Collection

Spray desorption collection (SDC) and reflective electrospray ionization (RESI) were used to independently study the desorption and ionization processes that together comprise desorption electrospray ionization (DESI). Both processes depend on several instrumental parameters, including the nebulizing gas flow rate, applied potential, and source geometries. Each of these parameters was optimized for desorption, as represented by the results obtained by SDC, and ionization, as represented by the results obtained by RESI. The optimized conditions were then compared to the optimization results for DESI. Our results confirm that optimal conditions for desorption and ionization are different and that in some cases the optimized DESI conditions are a compromise between both sets. The respective results for DESI, RESI, and SDC for each parameter were compared across the methods to draw conclusions about the contribution of each parameter to desorption and ionization separately and then combined within DESI. Our results indicate that desorption efficiency is (1) independent of the applied potential and (2) the impact zone to inlet distance, and that (3) gas pressure settings and (4) sprayer to impact zone distances above optimal for DESI are detrimental to desorption but beneficial for ionization. In addition, possible interpretations for the observed trends are presented.     

Mass spectrometric studies of the gas phase retro-<Emphasis Type="Italic">Michael</Emphasis> type fragmentation reactions of 2-hydroxybenzyl-<Emphasis Type="Italic">N</Emphasis>-pyrimidinylamine derivatives

The gas-phase fragmentation reactions of 2-hydroxybenzyl-N-pyrimidinylamine derivatives (Compounds 1 to 6), the O-N-type acid-catalyzed Smiles rearrangement products of 2-pyrimidinyloxy-N-arylbenzylamine derivatives, have been examined via positive ion matrix-assisted laser desorption/ionization (MALDI) infrared multiphoton dissociation (IRMPD) mass spectrometry in FT-ICR MS and via negative ion electrospray ionization (ESI) in-source collision-induced dissociation (CID) mass spectrometry, respectively. The major fragmentation pathway of protonated 1 to 6 gives the F ions under IRMPD; theoretical results show that the retro-Michael reaction channel is more favorable in both thermodynamics and kinetics. This explanation is supported by H/D exchange experiments and the MS/MS experiment of acetylated 1. Deprotonated 1 to 6 give rise to the solitary E ions (aromatic nitrogen anions) in the negative ion in-source CID; theoretical calculations show that a retro-Michael mechanism is more reasonable than a gas-phase intramolecular nucleophilic displacement (SN2) mechanism to explain this reaction process.