欢迎光临iblog
第1楼2008/08/21
不了解Q-TOF，说说这两种扫描方式吧。
1、precursor ion scan: 母离子扫描，Q3选定某一特定m/z的子离子，
扫描Q1，得到能产生该子离子的所有前体离子，即母离子谱图。
Q1 masses Q3masses
from to from to
300 400 191
适合于含有相同局部结构的不同化合物的鉴定。
2、neutral loss scanning：中性丢失扫描，Q1和Q3同时扫描，只是
二者始终保持某一特定的质量差（即中性丢失质量），一般标记可产
生该特定中性丢失的前体离子。
Q1 masses Q3masses
from to from to
200 420 182 402
适合于含某一官能团的化合物鉴定（如含-OH，-NH2）
ericson114
第2楼2008/08/21
不知道我这样理解对不：
也就是说不管这两种模式，刚开始应该都需要做一个MS1的full scan ,比如说这是event 1;
然后再发生event 2, Q1先选择某个precursor ion ，Q2 CID, Q3扫描特定的离子（要么特定子离子，要么减少特定Neutral loss的m/z ion）
这两种模式都是需要发生这两个event的吧？
ericson114
第5楼2008/08/21
谢谢
我有两个问题
第一，precursor ion scan不是需要选择特定的子离子进行检测的吗？那TOF本身是无法选择离子的吧，如何实现？
第二，我不理解Q和TOF无法同步是什么意思，是指scan时间上有差距吗？不过TOF倒是也不能选择M-m，因此也就是无法实现neutral loss 吧
欢迎光临iblog
第8楼2008/08/26
[quote]原文由 ericson114 发表:不知道我这样理解对不：
也就是说不管这两种模式，刚开始应该都需要做一个MS1的full scan ,比如说这是event 1;
然后再发生event 2, Q1先选择某个precursor ion ，Q2 CID, Q3扫描特定的离子（要么特定子离子，要么减少特定Neutral loss的m/z ion）
这两种模式都是需要发生这两个event的吧？
如果我对你的话理解没错的话(hehe,绕口令)， “也就是说不管这两种模式，刚开始应该都需要做一个MS1的full scan ,比如说这是event 1”，这句话不准确。不一定都有这个full scan 过程，full scan 是常用的一个基本扫描模式，但它不是所有扫描模式的先导，例如子离子扫描过程：Q1只允许你设定的母离子通过（四极杆所加RF/DC电压为特定值），Q2 CID，Q3扫描记录产生的子离子（Q3在进行扫描，但我理解你说的event 1 不是这个过程吧）。
其他的就不说了，大家讲的已经很清楚了。
虽不是我的主题贴，但是也受益颇多，所以顺便谢谢大家的讨论与分享em0805]
徐好狗
第9楼2008/08/27
你看的那本书太老了，换个英文的吧。
Anal. Chem., 79 (15), 5991 -5999, 2007. 10.1021/ac070619k S0003-2700(07)00619-1
Web Release Date: June 16, 2007
Copyright © 2007 American Chemical Society
Screening and Sequencing of Glycated Proteins by Neutral Loss Scan LC/MS/MS Method
Himanshu S. Gadgil,* Pavel V. Bondarenko, Michael J. Treuheit, and Da Ren*
Department of Pharmaceutics, Amgen, Inc., Thousand Oaks, California 91320
Received for review March 28, 2007. Accepted May 16, 2007.
Abstract:
Nonenzymatic protein glycation is caused by a Schiff's base reaction between the aldehyde groups of reducing sugars and the primary amines of proteins. A reversed-phase liquid chromatography method followed by a neutral loss scan mass spectrometric method was developed for the screening of glycation in proteins. The neutral loss scan was based on a unique sugar moiety neutral loss (-162 Da) that we observed in the fragmentation spectra of glycated peptides on Q-Tof type mass spectrometers. The collision energy was optimized for this neutral loss using a glycated synthetic peptide, and 20 eV was found to be the optimum collision energy. The neutral loss scan experiment was composed of two segments. In the first segment, the glycated peptides were identified based on the signature neutral loss of 162 Da when the collision energy was elevated to 20 eV. In the second segment, the glycated peptides were selected as the parent ions and fragmented at higher collision energy to break the peptide bonds. The fragmentation spectra of the selected glycated peptides revealed both the amino acid sequences and the sites of glycation. This neutral loss scan method was used to study the glycation in human serum albumin (HSA). The glycation sites in HSA were identified based on the retention time shift of glycated peptides, the mass accuracy from the MS scan, the signature neutral loss, and MS/MS information. Using this method, we were able to identify that 31 lysine residues were partially glycated from the glycated HSA sample, which has a total of 59 lysine residues.
徐好狗
第10楼2008/08/27
doi:10.1016/j.jasms.2005.11.002 How to Cite or Link Using DOI (Opens New Window)
Copyright © 2006 American Society for Mass Spectrometry Published by Elsevier B.V.
Article
Multiple Neutral Loss Monitoring (MNM): A Multiplexed Method for Post-Translational Modification Screening
Michael D. Hoffmanlow asterisk, low asterisk, Matthew J. Sniatynskia, Jason C. Rogalskia, J.C. Yves Le Blancb and Juergen Kastc, Corresponding Author Contact Information, E-mail The Corresponding Author
aThe Biomedical Research Centre, University of British Columbia, Vancouver, British Columbia, Canada bMDS Sciex, Concord, Ontario, Canada cDepartment of Chemistry, University of British Columbia, Vancouver, British Columbia, Canada
Received 24 August 2005;
revised 3 November 2005;
accepted 7 November 2005.
Available online 27 January 2006.
Post-translational modifications of proteins are involved in determining the activity of proteins and are essential for proper protein function. Current mass spectrometric strategies require one to specify a particular type of modification, in some cases also a particular charge state of a protein or peptide that is to be studied before the actual analysis. Due to these requirements, most of the modifications on proteins are not considered in such an experiment and, thus, a series of similar analyses need to be performed to ensure a more extensive characterization. A novel scan strategy has been developed, multiple neutral loss monitoring (MNM), allowing for the comprehensive screening of post-translational modifications (PTM) on proteins that fragment as neutral losses in a mass spectrometer. MNM method parameters were determined by performing product ion scans on a number of modified peptides over a range of collision energies, providing neutral loss energy profiles and optimal collision energies (OCE) for each modification, supplying valuable information pertaining to the fragmentation of these modifications and the necessary parameters that would be required to obtain the best analysis. As the optimal collision energy was highly dependent on the type of modification and the charge state of the peptide, the MNM scan was operated with a collision energy gradient. Autocorrelation analyses identified the type of modification, and convolution mapping analyses identified the associated peptide. The MNM scan with the new collision energy parameters was successfully applied to a mixture of four modified peptides in a BSA digest. The implementation of this technique will allow for comprehensive screening of all modifications that fragment as neutral losses.
赛默飞实验室产品焕新计划有奖调研！
【七月征文】不一YOUNG实验“猿”
报名开启：ICS2024第十三届光谱网络会议！
推荐收藏！盘点中药材及饮片检测解决方案
