r******l
发帖数: 48 | 1 It seems the machine has problem and needs to be fixed. The data from such
machine is not reliable. |
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s*******c
发帖数: 179 | 2 UCR? UC, Riverisde? I heard MS manager there is a mean SOB and idiot. But
new TOF instrument is almost solely for those outsourced samples. The people
in the department can hardly get on the instrument. |
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w********g
发帖数: 447 | 3 Another suggestion I will make is to try MS/MS on Q-Tof. I believe you did
MS/MS on ion-trap? So fragment with mass below 1/3 of your molecular ion
will not be seen. Try instrument other than ion trap. Maybe you can also get
more clue. |
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f********r
发帖数: 190 | 4 Ok. I will ask them to do another MS/MS on Q-Tof and see what we can get.
Thanks for the all feedback here.
get |
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b*******g
发帖数: 1309 | 5 还是直接做EI比较好
EIMS 的谱图库比较多，search 到的可能性比较大
Q-tof 之类是增加了检测范围，跟ion trap在本质上没有区别 |
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w********g
发帖数: 447 | 6 除了1/3 mass cut off, q-tof跟ion trap的fragmentation依然可以差老远，比如fix
charged的东西。这种是case by case，主要看分子的性质啦。
如果楼主坚持这个长链的家伙是很常见的化合物，EI可能会有希望。 |
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E****F
发帖数: 10 | 7 你的ion-trap MS/MS用了47eV,得到的product ion 信息不是很充足。如果要做Q-TOF的
话，可以尝试不同的collision enrgy，建议加大CE到60-100eV试试。另外扩大mass
range来看看是否有dimer或trimer. 如果猜测是脂肪酸的话，可以去www.lipidmaps.
org查询一下database，那里有isotope distribution for natural isotopes. 如果不
用NMR,就麻烦些上stable isotope, like C13, H2,or O18，希望对你有帮助。 |
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w********g
发帖数: 447 | 8 如果是173是[M+Na]+的话Q-tof的MS/MS的好处是应该可以看到低mass端一个单独的Na+
的峰，一目了然。ion-trap就看不到。
eV |
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x*****g
发帖数: 82 | 9 问题1： MALDI-TOF发现单一的产物峰M+122（DMAP分子量），怎么解释？
问题2： 柱层析产品核磁总是有DCC的存在，如何继续纯化？ |
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l***d
发帖数: 1828 | 10 组里打算买一台质谱仪，本来想买agilent的，结果太贵了，Waters有个二手的打算卖
给我们，不知道waters的ESI Q-TOF怎么样？操作，维护怎么样？我们这里没人用过，不知道如何？先谢谢了。 |
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s***e
发帖数: 404 | 11 不是Tof, 是3Q, 浓度也不高, 最低的点就是detection limit了. 关键是以前的用的是
一样的浓度,curve是直的. |
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p**********m
发帖数: 472 | 12 室内温度到底对tof 的影响有多大. mass accuracy 老是drift on daily basis.
可能是温度问题吗 ,我们实验室也是一会儿冷一会儿热的. |
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k********s
发帖数: 320 | 13 Q-tof accuracy is very temperature dependent. For good accuracy you need to
use lockspray or at least adjust Veff using Leucine Enkephalin on daily
basis. |
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k********s
发帖数: 320 | 14 1. Are you using Q-tof premier or not?
2. Did you use W mode?
3. What is your nominal mass accuracy, less than 0.1 amu I hope?
4. What did you use in lockspray lock mass?
5. Is the mass you are looking for very different from your lock mass?
6. Is the signal of the mass you are looking for very different from
that of your lock mass?
7. Did you make sure that when you do mass measurement, the cps of your
analyte is <200? i.e take signal from tail if the intensity is too high?
8. Did you use on-th |
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b****u
发帖数: 2771 | 15 其实 接你前面的问题
LC 中 band broadening 是 液相中diffusion
MS 里 是气相的
气相的影响应该小
不过 MS 的 Resolution 和 analyzer 有关
Orbi, FTICR > TOF-reflectron >Q, LT
分子的 initial energy, uniform of field, vacuum, 都有影响。 |
|
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W*******R
发帖数: 1224 | 17 PITC对氨基的衍生物在酸性下很不稳定，你过柱子柱子如果是硅胶柱等弱酸性物质，你
当然什么都拿不到。好好看看edman降解是怎么回事，机理要搞懂。 |
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S*****n
发帖数: 6055 | 18 你怎么衡量催化效率？转化率还是TOF？另外你是均相催化还是非均相？ |
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b*******g
发帖数: 1309 | 19 你啥都不懂，还买仪器
实验目的不一样，买的仪器也不一样
Q跟QQQ，Q-TOF，Ion trap差太远了
另外这个只是MS，没有LC
另外，有些老板买仪器都有多达30%的discoun，你买就没有，哈哈 |
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m******i
发帖数: 73 | 21 Two Postdoc positions are available immediately at Department of Environmental Sciences and Engineering, University of North
Carolina at Chapel Hill. We are working on quantitation of carcinogen-
induced DNA adducts and protein biomarkers. The lab is equipped with 3
Triple quadrupole mass spectrometers, 1 ion trap, 1 ICP-MS and 1 Q-TOF. We
also have several HPLC, UPLC and nano-LC systems. The successful candidates
should have hand-on experience on liquid chromatographic techniques and mass
spect |
|
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s*******c
发帖数: 179 | 23 plus a proton, +1.007276 |
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t******t
发帖数: 3045 | 24 ESI positive mode: mostly yes |
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x*****g
发帖数: 82 | 26 国内有机硕士毕业，博士期间的工作经历如下
Synthesis and characterization of Polymer & monomer, Modification functional
molecules to polymer scaffolds
The application of synthetic biocompatible polymers, like drug and gene
delivery
Operating Instrumentals, NMR, HPLC, GPC, MS (MALDI-TOF),TEM, Confocals IR,
DLS etc.
publication现在只有一篇jacs和国内时候发的几篇有机方向文章，还有4-5篇已经投出
或者即将投出。
明年五月份毕业，不知道能不能在毕业前找到位子，其实也想找工业的，但是自己口语
不好，没信心。
将来何去何从还没有打算。
罗嗦了一大堆，请大家给点建议，现在心里很忐忑，谢谢 |
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p*******8
发帖数: 158 | 27 Our lab plans to buy one, but not sure how much budget will need for regular
-use basis. So can you tell me approximately how much for a simple MALDI or
MALDI-MS/MS, based on your experience. I know I can quote with different
companies such like AB Sciex, Bruker, or Micromass. However, I won't be
bothered by their agents right now during this beginning step . By the way,
tell me instrument type and specifications as possible as you can. Thanks. |
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b*******g
发帖数: 1309 | 28 Bruker Autoflex 3
250K-400K, 看你的配置跟service，以及关系 |
|
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h********n
发帖数: 4079 | 30 Thank you very much.
5ppm)
you |
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R*******1
发帖数: 6 | 31 Ad Description for BS/MS Sr Associate Scientist
Responsibilities:
• Work within the Analytical Protein Chemistry area to provide
analytical support for novel peptide and protein therapeutics in pre-
clinical and clinical development.
• Primary responsibilities include the identification and
characterization of post-translational modifications in protein therapeutic
candidates, using state of the art separations technology and mass
spectrometry instrumentation, with an emphasis ... 阅读全帖 |
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b*******g
发帖数: 1309 | 32 PMF (peptide mass fingerprint)
一般PMF 只可以ID 一种蛋白
MS/MS 可以ID 多种蛋白 |
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y***l
发帖数: 1095 | 33 谢谢，那DIGEST的部分只能TA提前帮学生做了？？如果学生LAB只有三小时的话。。。
除了BSA还有别的蛋白推荐吗？因为你说一个已知，一个未知。。。 至少需要两种蛋白
吧。 |
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b*******g
发帖数: 1309 | 34 找一些其他便宜的蛋白
like Cyt C， Myoglobin 这类呗 |
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K********A
发帖数: 917 | 35 帮助IONIZATION？MALDI不熟。估计是Cu2+能络合到被测物上增加charge |
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b*********2
发帖数: 190 | 36 Cu(II)+e- -->Cu(I)，
copper salt acts like a "electron sink",thus enhance the positive mode
signal |
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b*********2
发帖数: 190 | 37 Small proteins, <20k without disulfide bonds, can be digested to some extent
(maybe not completely) within 2-3 hours if increase the ration of enzyme/
target protein. However, you may want to prepare some digested sample
beforehand just in case. |
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y***l
发帖数: 1095 | 38 非常感谢。。。
关于那个DIGEST，看来还是不适合当天做啊，如果实验时间总共才三小时的话。。。
要是不用做PROTEIN的，直接有关于PEPTIDE的实验设计就好了。 |
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b*********2
发帖数: 190 | 39 You may start the session with analyzing simple peptides, or peptide
mixtures. Then follow with the digested protein and database search.
3 hours is pretty short,especially if they have no hands-on experience with
MALDI before. |
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y***l
发帖数: 1095 | 40 嗯，是的只一个三小时的SESSION的话，做PROTEIN 不合适，而且我自己也没有经验，
所以不做那个好了。要不就买A, B, C, D, E五种PEPTIDE，告诉他们是哪五种，一人给
一个未知PEPTIDE MIXTURE，大概有两三种PEPTIDE，然后每人做一个MALDI，用M/Z判断
自己有哪两三种PEPTIDE，不知道这样会不会太简单。。。
还是说不告诉他们A,B,C,D,E是什么，每一个再做MS/MS，然后根据MS/MS自己推是什么
PEPTIDE？或者有什么网上的数据库可以用的？ |
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b*********2
发帖数: 190 | 41 如果我是你，我会这么设计：
买三种peptide（比如angiotensin之类的），三种protein（比如myoglobin,beta-
lactoglobulin等常见的），实验之前你把protein给digest好，作为三个unknown。
前半节，准备matrix，让他们自己混各种peptide点板玩，对谱有个大致的印象。如果
有时间可以做MS/MS，倒推sequence。不过如果他们完全没有接触过，这里还需要一点
时间讲解b，y ion的基础知识。
后半节，把unknown protein digests发给他们，得到谱图，分别用手动计算和
database search来判断哪个是什么protein。
对于de novo sequencing，可以用protein prospector作为依据，MS/MS和digest都可
以计算。 |
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f*********e
发帖数: 1144 | 42 sounds quite complicated for undergrads:) espcially the de novo part, I have
a lot of trouble manually interpreting spectra as a postdoc in MS field |
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f*********e
发帖数: 1144 | 43 The software together with Autoflex (FlexAnalysis/Biotools) are not that
easy themselves, you don't want to get yourself trapped if you are not
familiar with them.
Skip MS2, just fire on a couple spots and show them the peaks. Make it like
a PC game. Peptides PMF is enough together with calibration (well,
calibration is kinda tricky too). Don't try intact proteins.
We had 3 days onsite training on Autoflex w/o LIFT and I still keep bugging
bruker.....shame on me...hehehehehe |
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f*********e
发帖数: 1144 | 44 rite, additionally, pierce spin column may complete the process in 15min....
reduction and alkylation will help a lot as well. But sample prep itself is
a big deal for maldi. My suggestion is just to simply mix peptide standards
together. Enough for 3 hours undergrad course.
extent |
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b*******g
发帖数: 1309 | 45 哈哈，我一直在想 bruker MALDI 的3-day training 是给谁准备的。。。
（我们仪器装好之后就training了半个小时）
我training 过很多本科生，基本上一个小时后就可以了（不包括使用biotool）
另外，MALDI 是一个很容易上手的仪器，我们training MALDI imaging 也不过只花了3
个小时
like
bugging |
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L****r
发帖数: 333 | 46 BB's method is too complicated to undergraduates.
1. Carefully calibrate the instruments using standards.
2. Teach students how to spot samples: sandwich (matrix-sample-matrix); mix
sample and matrix solution, then spot; matrix then sample. Compare the
performance.
3. Analyze two protein samples, remember: if lots of salts in the protein
solution, you need to extract the protein using ZIP tip or NuTip.
I THINK THIS IS ENOUGH FOR UNDERGRADUATES WITHIN 3 HOURS
Good luck! |
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y***l
发帖数: 1095 | 47 谢谢！ 这个的后半部分好象蛮复杂的样子，我自己熟悉尚需要时日，恐怕现在就写成
实验教程不太现实。。。。看来偶们对本科生的水平估计不同啊。。。偶以前只教过
GENERAL CHEM，对SENIOR学生的水平还不是很清楚呢。 |
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y***l
发帖数: 1095 | 48 你们肯定是MASS大组吧？！
偶六月份要去BRUKER的TRAINING，汗，应该是为偶们这种人准备的，呵呵
了3 |
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y***l
发帖数: 1095 | 49 谢谢！很喜欢这个设计，我会给peptide unknown和protein unknown，这样他们可以分
别用RP mode和LP mode，考虑到虽然train一个人，一小时是够了，但本科生要排队用
机子吧，三小时应该差不多了。我觉得用三种方法点板挺好的。不过题外问一下你们这
些常做MALDI的人，这三种点板方式，在实际应用中你们觉得哪种好呢？或者说对于不
同的analyte，有各自适合的方法？
mix |
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b*******g
发帖数: 1309 | 50 有点区别。但是应该看不出来多大，还是不要用的
关键是不用的analyte 要用不同的matrix，还不如比较matrix 的区别 |
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